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1

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

PubMed

The design and optimisation of a neutron beam for neutron capture therapy (NCT) is accompanied by the neutron spectra measurements at the target position. The method of activation detectors was applied for the neutron spectra measurements. Epithermal neutron energy region imposes the resonance structure of activation cross sections resulting in strong self-shielding effects. The neutron self-shielding correction factor was calculated using a simple analytical model of a single absorption event. Such a procedure has been applied to individual cross sections from pointwise ENDF/B-VI library and new corrected activation cross sections were introduced to a spectra unfolding algorithm. The method has been verified experimentally both for isotropic and for parallel neutron beams. Two sets of diluted and non-diluted activation foils covered with cadmium were irradiated in the neutron field. The comparison of activation rates of diluted and non-diluted foils has demonstrated the correctness of the applied self-shielding model. PMID:15353753

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

2004-01-01

2

Moderation of neutron spectra  

SciTech Connect

Most of the accelerators that produce the various microenergetic neutron sources required for low-energy neutron dosimetry studies have been shut down. One alternative to accelerator-produced sources is the use of fission neutron or ({alpha},n) sources with unique neutron spectra. The problem with this solution is that maintenance of these sources is impractical. To help overcome this impracticality, the authors propose the use of moderating materials to produce a variety of spectra using a minimum number of sources. In the study, they performed Monte Carlo transport calculations under the following conditions: transporting neutrons from bare {sup 252}Cf or {sup 241}Am-Be sources from the center of various-sized spheres; tallying neutron spectra at 50 cm from the source. Of the twelve different moderating materials they studied, they found pure copper to be an ideal moderator. In this paper, they present flux-weighted energies, neutron spectra, and dose information for both {sup 252}Cf and {sup 241}Am-Be sources in bare and six-moderator configurations.

Hsu, H.H.; Chen, J. [Los Alamos National Lab., NM (United States). Health Physics Measurements Group

1997-05-01

3

Neutron energy spectra unfolding from foil activation detector measurements with MINUIT  

NASA Astrophysics Data System (ADS)

A method for unfolding neutron energy spectra from foil activation measurements using the multiparameter function minimisation routine MINUIT of Cernlib has been developed. It is based on the expansion of the neutron energy distribution on a set of parameters that are fitted to minimise the square sum of differences between the measured and calculated activities under smoothness and shape constraints. A modified square sum of differences expression weighted by each activation detector response contribution over the whole neutron energy range is proposed and compared with the classical square sum formulation. The proposed unfolding procedure is first illustrated by a set of 15 detectors to simulate reaction rates calculated using a typical neutron reactor energy spectrum. The demonstration of the proposed method is next achieved using measured reaction rates of the Arkansas Nuclear One power plant (ANO) benchmark spectrum of the Neutron Metrology File (NMF-90). Results of the proposed method were compared with those obtained by STAYNL and MSANDB unfolding codes using the same input data and were found in good agreement with the measured activities. The developed procedure is found to have an interesting advantage in unfolding neutron energy distribution in cases of a lack of information on the a priori solution. This has been illustrated by unfolding the JOYO MK-II fast breeder reactor neutron spectrum, using a set of experimental activation rates without a guess solution.

Seghour, A.; Seghour, F. Z.

2005-12-01

4

Measurement of neutron spectra in varied environments by the foil-activation method with arbitrary trials  

SciTech Connect

Neutron spectra have been measured by the foil-activation method in 13 different environments in and around the Sandia Pulsed Reactor, the White Sands Missile Range Fast Burst Reactor, and the Sandia Annular Core Research Reactor. The spectra were obtained by using the SANDII code in a manner that was not dependent on the initial trial. This altered technique is better suited for the determination of spectra in environments that are difficult to predict by calculation, and it tends to reveal features that may be biased out by the use of standard trial-dependent methods. For some of the configurations, studies have also been made of how well the solution is determined in each energy region. The experimental methods and the techniques used in the analyses are thoroughly explained. 34 refs., 51 figs., 40 tabs.

Kelly, J.G.; Vehar, D.W.

1987-12-01

5

Martian neutron leakage spectra  

SciTech Connect

Energy spectra of Martian leakage neutrons are calculated by a high-energy nucleon-meson transport code using a Monte Carlo technique and a one-dimensional diffusion accelerated neutral-particle transport code, which solves the Boltzmann equation. Four series of calculations were made to simulate (1) a uniform surface layer containing various amounts of H/sub 2/O, (2) different burial depths of a 50% H/sub 2/O layer underneath a 1% H/sub 2/O layer, (3) changing atmospheric pressure, and (4) a thick CO/sub 2/ ice sheet overlying a ''dirty'' water ice sheet. We found that all calculated spectra at energies less than about 1000 eV could be fitted by a superposition of thermal and epithermal functions having four free parameters. Two of these parameters, the thermal and epithermal amplitudes, were found to vary systematically over ranges exceeding 1 order of magnitude and to specify uniquely the configuration in each of the series. We conclude that measurements of leakage neutron spectra should allow determination of the hydrogen content of surface layers buried to depths up to about 100 g/cm/sup 2/ and determination of the thickness of a polar dry ice cap up to thicknesses of about 250 g/cm/sup 2/. Variations of these parameters were also shown to depend on the composition of the assumed surface layers through the average atomic mass and the macroscopic scattering and absorption cross sections. copyright American Geophysical Union 1988

Drake, D.M.; Feldman, W.C.; Jakosky, B.M.

1988-06-10

6

Martian neutron leakage spectra  

NASA Astrophysics Data System (ADS)

A high-energy nucleon-meson transport code is used to calculate energy spectra of Martian leakage neutrons. Four calculations are used to simulate a uniform surface layer containing various amounts of water, different burial depths of a 50 percent water layer underneath a 1 percent water layer, changing atmospheric pressure, and a thick carbon dioxide ice sheet overlying a "dirty" water ice sheet. Calculated spectra at energies less than about 1000 eV were fitted by a superposition of thermal and epithermal functions having four free parameters, two of which (thermal and epithermal amplitudes) were found to vary systematically and to specify uniquely the configuration in each of the series. Parameter variations depend on the composition of the assumed surface layers through the average atomic mass and the macroscopic scattering and absorption cross sections. It is concluded that measurements of leakage neutron spectra should allow determination of the hydrogen content of surface layers buried to depths up to about 100 g/sq. cm and determination of the thickness of a polar dry ice cap up to a thickness of about 250 g/sq. cm.

Drake, D. M.; Feldman, W. C.; Jakosky, B. M.

1988-06-01

7

Unfolding neutron energy spectra from foil activation detector measurements with the Gold algorithm  

NASA Astrophysics Data System (ADS)

In this work, the Gold algorithm is applied to the unfolding of neutron reactor energy spectra from reaction rates data of multiple foil activation detectors. Such a method, which forms the basis of a developed unfolding computer program called SAYD, has the advantage of not requiring a priori knowledge on the spectrum in the unfolding process. The program SAYD is first illustrated by synthesized reaction rates data calculated using a semi-empirical formulation of a typical intermediate and fast neutron reactor spectrum. The demonstration of the unfolding program SAYD is next achieved using measured reaction rates of the Arkansas Nuclear One power plant (ANO) benchmark spectrum by comparing results of SAYD program with those obtained by STAYNL and MSANDB unfolding codes.

Seghour, A.; Seghour, F. Z.

2001-01-01

8

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

Microsoft Academic Search

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

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

2009-01-01

9

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

10

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

NASA Astrophysics Data System (ADS)

A method for the interpretation of ?-ray spectra as obtained in INAA using linear least squares techniques is described. Results obtained using this technique and the traditional method previously in use at IRI are compared. It is concluded that the method presented performs better with respect to the number of detected elements, the resolution of interferences and the estimation of the accuracies of the reported element concentrations. It is also concluded that the technique is robust enough to obviate the deconvolution of multiplets.

Blaauw, Menno

1994-12-01

11

Spent-fuel photon and neutron source spectra  

SciTech Connect

Computational activities at Oak Ridge National Laboratory have been performed to develop appropriate data and techniques for computing the photon and neutron source spectra of spent fuel. The methods reviewed here include both the determination of spent-fuel composition and the radiation source spectra associated with these isotopic inventories.

Hermann, O.W.; Alexander, C.W.

1983-01-01

12

Fast neutron induced fission neutron spectra below the incident energy  

NASA Astrophysics Data System (ADS)

Fission neutron spectra from neutron induced fission in 235U and 239Pu for energies below that of the neutron inducing fission have been measured. The spectra were obtained for 1.5 MeV and 2.5 MeV incident neutrons. Previous accelerator-based fission neutron spectra measurements have been seriously complicated by time-correlated gamma-rays and scattered neutrons from the fission sample. This work provides a way to extract fission neutrons from other radiation species in a manner not previously attempted. Protons from the University of Massachusetts Lowell type CN 5.5 MV Van de Graaff accelerator were pulsed and then bunched by a Mobley compression bunching system to pulse time durations of approximately 500 ps. Monoenergetic neutron bursts produced by the 7Li(p,n)7Be reaction, were incident on samples of 235U and 239Pu inducing fission and producing fission neutrons. Three BaF2 detectors placed near the sample were used to identify fission gamma rays. The coincidence of two BaF2 detector anode signals was used to gate a liquid scintillation detector to distinguish fission events from other events in the detector. The fission neutron time-of-flight data was acquired by a new personal computer based multi-parameter data acquisition system called INVADAR. INVADAR allowed data to be taken in a multi-parameter event-mode format using a single analog-to-digital converter and an analog multiplexer. The fission neutron spectra shape and average energy measured here compare well to previous measurements and theory. The data support the theoretical suggestion that the fission neutron spectrum shape depends upon the incident neutron energy and mass of the fissioning nucleus.

Woodring, Mitchell Lee

1997-09-01

13

Comparison Between LYRA and SAND Code Performance for the Extrapolation of Data from Activation Detectors Used for Determining Spectra of Acceleration Neutrons.  

National Technical Information Service (NTIS)

Mathematical descriptions are given of the LYRA and SAND programs which are then used to evaluate typical acceleration neutron spectra or various energy conditions of incident protons, bombardment materials, and angle of neutron emission. 16 references, 1...

A. Salomone C. Birattari P. Cesana

1980-01-01

14

Prompt Fission Neutron Energy Spectra Induced by Fast Neutrons  

NASA Astrophysics Data System (ADS)

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

Staples, Parrish Alan

15

Fast Neutron Induced Fission neutron Spectra Below the Incident Energy  

SciTech Connect

Fission neutron spectra from neutron induced fission in 235U and 239Pu for energies below that of the neutron inducing fission have been measured. The spectra were obtained for 1.5 MeV and 2.5 MeV incident neutrons. Previous accelerator-based fission neutron spectra measurements have been seriously complicated by time-correlated gamma rays and scattered neutrons from the fission sample. Three barium fluoride detectors were placed near the sample undergoing induced fission and used to identify fission gamma rays. A coincidence of fission gamma rays was used to gate a liquid scintillator neutron detector to distinguish fission events from other events. The fission neutron spectral shape and average energy measured in this experiment compare well to both previous measurements and prior theory and also suggest a dependence on incident neutron energy and mass of the fissioning nucleus. An overview of the experiment, a discussion of the results, and the importance of this work to homeland security are given.

Woodring, Mitchell L.; Egan, James J.; Kegel, Gunter H.; DeSimone, David J.

2008-06-15

16

Neutron Spectra in a 15 MV LINAC  

SciTech Connect

Neutron spectra were calculated inside the treatment hall of a 15 MV LINAC, calculations were carried out using Monte Carlo methods. With a Bonner sphere spectrometer with pairs of thermoluminiscent dosimeters the neutron spectrum at 100 cm from the isocenter was measured and compared with the calculated spectrum. All the spectra in the treatment hall show the presence of evaporation and knock-on neutrons; also the room-return due to the hall features is shown. In the maze the large contribution are due to epithermal and thermal neutrons. A good agreement between the calculated and measured spectrum at 100 cm was noticed, from this comparison the differences are attributed to the water content in the concrete of the hall.

Vega-Carrillo, H. R. [Unidad Academica de Estudios Nucleares de la Universidad Autonoma de Zacatecas. Apdo. Postal 336, 98000 Zacatecas, Zac. (Mexico); Chu, Wei-Han [National Tsing Hua University, Hsinchu, Taiwan (China); Tung, Chuan-Jong [Chan Gung University, Taiwan (China); Lan, Jen-Hong [Chan Gung Memorial Hospital-Kaohsiung Medical Center and National Kaohsiung University, Kaohsiung, Taiwan (China)

2010-12-07

17

Uncertainty Quantification on Prompt Fission Neutrons Spectra  

NASA Astrophysics Data System (ADS)

Uncertainties in the evaluated prompt fission neutrons spectra present in ENDF/B-VII.0 are assessed in the framework of the Los Alamos model. The methodology used to quantify the uncertainties on an evaluated spectrum is introduced. We also briefly review the Los Alamos model and single out the parameters that have the largest influence on the calculated results. Using a Kalman filter, experimental data and uncertainties are introduced to constrain model parameters, and construct an evaluated covariance matrix for the prompt neutrons spectrum. Preliminary results are shown in the case of neutron-induced fission of 235U from thermal up to 15 MeV incident energies.

Talou, P.; Madland, D. G.; Kawano, T.

2008-12-01

18

Neutron and gamma-ray spectra of 239PuBe and 241AmBe.  

PubMed

Neutron and gamma-ray spectra of 239PuBe and 241AmBe were measured and their dosimetric features were calculated. Neutron spectra were measured using a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. The 239PuBe neutron spectrum was measured in an open environment, while the 241AmBe neutron spectrum was measured in a closed environment. Gamma-ray spectra were measured using a NaI(Tl) scintillator using the same experimental conditions for both sources. The effect of measuring conditions for the 241AmBe neutron spectrum indicates the presence of epithermal and thermal neutrons. The low-resolution neutron spectra obtained with the multisphere spectrometer allows one to calculate the dosimetric features of neutron sources. At 100 cm both sources produce approximately the same count rate as that of the 4.4 MeV gamma-ray per unit of alpha emitter activity. PMID:12150274

Vega-Carrillo, Héctor René; Manzanares-Acuña, Eduardo; Becerra-Ferreiro, Ana María; Carrillo-Nuñez, Aureliano

2002-08-01

19

Neutron Spectra and H*(10) in a 15 MV Linac  

NASA Astrophysics Data System (ADS)

Neutron spectra and the ambient dose equivalent were calculated inside the bunker of a 15 MV Varian linac model CLINAC iX. Calculations were carried out using Monte Carlo methods. Neutron spectra in the vicinity of isocentre show the presence of evaporation and knock-on neutrons produced by the source term, while epithermal and thermal neutron remain constant regardless the distance respect to isocentre, due to room return. Along the maze neutron spectra becomes softer as the detector moves along the maze. The ambient dose equivalent is decreased but do not follow the 1/r2 rule due to changes in the neutron spectra.

Benites, J.; Vega-Carrillo, H. R.; Hernandez-Davila, V. M.; Rivera, T.; Carrillo, A.; Mondragon, R.

2010-12-01

20

Neutron Spectra and H*(10) in a 15 MV Linac  

SciTech Connect

Neutron spectra and the ambient dose equivalent were calculated inside the bunker of a 15 MV Varian linac model CLINAC iX. Calculations were carried out using Monte Carlo methods. Neutron spectra in the vicinity of isocentre show the presence of evaporation and knock-on neutrons produced by the source term, while epithermal and thermal neutron remain constant regardless the distance respect to isocentre, due to room return. Along the maze neutron spectra becomes softer as the detector moves along the maze. The ambient dose equivalent is decreased but do not follow the 1/r{sup 2} rule due to changes in the neutron spectra.

Benites, J. [Centro Estatal de Cancerologia de Nayarit-SSN-Mexico, Av. Enfermeria s/n, Col. Fray Junipero Serra, 63000 Tepic, Nayarit (Mexico); Alumno del Posgrado en CBAP, Universidad Autonoma de Nayarit, Carretera Tepic-Compostela km9. C.P. 63780. Xalisco-Nayarit-Mexico (Mexico); Vega-Carrillo, H. R.; Hernandez-Davila, V. M. [Unidad Academica de Estudios Nucleares, Universidad Autonoma de Zacatecas, Apdo. Postal 336, 98000 Zacatecas, Zac. Mexico (Mexico); Rivera, T. [CICATA-IPN, Unidad Legaria, Mexico city (Mexico); Carrillo, A.; Mondragon, R. [Centro Estatal de Cancerologia de Nayarit-SSN-Mexico, Av. Enfermeria s/n, Col. Fray Junipero Serra, 63000 Tepic, Nayarit (Mexico)

2010-12-07

21

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

22

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

SciTech Connect

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

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

2011-07-01

23

Fast Neutron Flux Measurement through Neutron Activation  

Microsoft Academic Search

Neutron activation of various materials is often used to detect the fluence from a neutron source. In this report silver sleeves were placed around individual Geiger-Mueller tubes, and set in a polyethylene box to measure the neutron flux from a D-D fusion pinch. The silver is neutron activated from the DPF neutrons which are moderated by the polyethylene box, and

Jim Ferguson

2002-01-01

24

Intercomparison of Two Neutron Spectrometric Activation Measurement Techniques.  

National Technical Information Service (NTIS)

The multicomponent wire activation detector developed for determining the neutron spectrum in WWER reactors was tested by intercomparison with activation foil detectors in two different neutron spectra. The detectors were irradiated in the WWR-SM reactor ...

I. Dennstaedt H. C. Mehner J. Vegh I. Vidovszky

1981-01-01

25

Measurement of free beam neutron spectra at eight BNCT facilities worldwide  

Microsoft Academic Search

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

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

2004-01-01

26

Delayed Neutron Energy Spectra Following Fast Fission of Uranium  

Microsoft Academic Search

Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of ^{238}U nuclei. The delay-time intervals span the range 0.17 to 10.2 seconds following initial fission while the measured spectra span neutron energies from 10 keV to 4 MeV. The experiment was performed utilizing the UMass\\/Lowell 5.5 MV Van de Graaff accelerator to produce fast

Marcel Franklin Villani

1992-01-01

27

Fission Neutron Spectra and Nuclear Temperatures  

Microsoft Academic Search

It is shown that Weisskopf's nuclear evaporation theory, when allowance is made for the expected distribution of nuclear temperatures of fission fragments, predicts an essentially Maxwellian distribution of fission neutron energies in the laboratory system. This is found to be in excellent agreement with all available data. On the assumption that neutron emission is symmetrical about 90° in the center-of-mass

James Terrell

1959-01-01

28

Fission neutron spectra measurements at LANSCE - status and plans  

SciTech Connect

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

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

2009-01-01

29

Measurement of neutron spectra through composed material block bombarded with DT neutrons  

Microsoft Academic Search

A 2-dimensional composed material assembly made of the iron and hydric block has been established. The neutron spectra from the assembly bombarded with 14-MeV neutrons at neutron generator have been obtained using the proton recoil technique with a stillbene detector. The detector positions were selected at the 60°, 120°, 180° on the surface of the iron spherical shell. The background

T. H. Zhu; R. Liu; X. X. Lu; L. Jiang; Z. W. Wen; M. Wang; J. F. Lin

2009-01-01

30

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

31

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

NASA Astrophysics Data System (ADS)

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.

Sterbentz, James W.

2009-08-01

32

Angular-distribution neutron-emission spectra of niobium following bombardment by fast neutrons  

SciTech Connect

Neutron-emission spectra at ten angles between 20 and 160/sup 0/ and incident neutron energies of 5.9, 7.1 and 8.4 MeV were measured relative to the neutron field emitted after spontaneous fission of /sup 252/Cf. The angular distribution of inelastically scattered neutrons appears to be essentially isotropic where it can be separated from the dominant elastic scattering peak. Above an excitation energy of 4 MeV the spectra are well described by a Maxwellian temperature distribution.

Guenther, P.T.; Smith, A.B.

1985-01-01

33

Application of Neural Networks for unfolding neutron spectra measured by means of Bonner Spheres  

NASA Astrophysics Data System (ADS)

A Neural Network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set. The present work used the ``Stuttgart Neural Network Simulator'' as the interface for designing, training and validation of a MultiLayer Perceptron network. The back-propagation algorithm was applied. The Bonner Sphere set chosen has been calibrated at the National Physical Laboratory, United Kingdom, and uses gold activation foils as thermal neutron detectors. The neutron energy covered by the response functions goes from 0.0001eV to 10MeV. Two types of neutron spectra were numerically investigated: monoenergetic and continuous. Good results were obtained, indicating that the Neural Network can be considered an interesting alternative among the neutron spectrum unfolding methodologies.

Braga, Cláudia C.; Dias, Mauro S.

2002-01-01

34

Inversion of neutron/gamma spectra from scintillator measurements  

NASA Astrophysics Data System (ADS)

The Radiation Assessment Detector (RAD) on-board NASA's Mars Science Laboratory (MSL) rover will measure charged particles as well as neutron and gamma radiation on the Martian surface. Neutral particles are an important contribution to this radiation environment. RAD measures them with a CsI (Tl) and a plastic scintillator, which are both surrounded by an anticoincidence. The incident neutron/gamma spectrum is obtained from the measurements using inversion methods which often fit a functional behavior, e.g., a power law, to the measured data applying the instrument response function and, e.g., a least-squares method. In situations where count rates are small, i.e., where the stochastic nature of the measurement is evident, maximum likelihood estimates with underlying Poissonian statistics improve the resulting spectra. We demonstrate the measurement and inversion of gamma/neutron spectra for a detector concept featuring one high-density scintillator and one high-proton-content scintillator. The applied inversion methods derive the original spectra without any strong assumptions of the functional behavior. Instrument response functions are obtained from Monte-Carlo simulations in matrix form with which the instrument response is treated as a set of linear equations. Using the response matrices we compare a constrained least-squares minimization, a chi-squared minimization and a maximum likelihood method with underlying Poissonian statistics. We make no assumptions about the incident particle spectrum and the methods intrinsically satisfy the constraint of non-negative counts. We analyzed neutron beam measurements made at the Physikalisch Technische Bundesanstalt (PTB) and inverted the measurement data for both neutron and gamma spectra. Monte-Carlo-generated measurements of the expected Martian neutron/gamma spectra were inverted as well, here the maximum likelihood method with underlying Poissonian statistics produces significantly better results.

Köhler, J.; Ehresmann, B.; Martin, C.; Böhm, E.; Kharytonov, A.; Kortmann, O.; Zeitlin, C.; Hassler, D. M.; Wimmer-Schweingruber, R. F.

2011-11-01

35

Inversion of neutron/gamma spectra from scintillator measurements  

NASA Astrophysics Data System (ADS)

We demonstrate the measurement and inversion of gamma/neutron spectra for a detector concept featuring one high-density scintillator and one high-proton-content scintillator for the example of the Radiation Assessment Detector on-board NASA's Mars Science Laboratory. The applied inversion methods derive the original spectra without any strong assumptions of the functional behavior. Instrument response functions are obtained from Monte-Carlo simulations in matrix form with which the instrument response is treated as a set of linear equations. Using the response matrices we compare a constrained least squares minimization, a chi-squared minimization and a maximum likelihood method with underlying Poissonian statistics. We make no assumptions about the incident particle spectrum and the methods intrinsically satisfy the constraint of non-negative counts. We analyzed neutron beam measurements made at the Physikalisch Technische Bundesanstalt (PTB) and inverted the measurement data for both neutron and gamma spectra. Monte-Carlo-generated measurements of the expected Martian neutron/gamma spectra were inverted as well, here the maximum likelihood method with underlying Poissonian statistics produces significantly better results.

Koehler, J.; Ehresmann, B.; Martin, C.; Böhm, E.; Kharytonov, A.; Kortmann, O.; Zeitlin, C. J.; Hassler, D. M.; Wimmer-Schweingruber, R. F.

2011-12-01

36

Review of spent-fuel photon and neutron source spectra  

SciTech Connect

The calculations of spent-fuel photon and neutron spectra have been significantly improved over the past several years. Methods for performing these computations at ORNL have been implemented in the ORIGEN2 and ORIGEN-S codes and the SAS2 control module of the SCALE system. The codes use photon data for delayed gamma rays, x-rays, spontaneous fission gamma rays, (..cap alpha..,n) reaction gamma rays, bremsstrahlung and decay constants, taken mainly from the Evaluated Nuclear Data Structure File. The data for neutron source strengths and spectral distributions of spontaneous fission and (..cap alpha..,n) reactions were compiled from several different research projects. Brief discussions of the codes, the spectral data and the range of applicability are presented. Also, several examples of spent-fuel photon and neutron spectra are included. 29 refs.

Hermann, O.W.; Alexander, C.W.

1986-01-01

37

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

38

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

Microsoft Academic Search

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

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

2009-01-01

39

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

40

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

2009-03-28

41

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

42

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

43

Measurement and unfolding of neutron spectra using Bonner spheres.  

PubMed

Neutron spectra from Am-Be, 252Cf sources and 2H + 2H and 2H + 3H reactions have been measured using a Bonner sphere system in conjunction with a 4 x 4 mm2 LiI(Eu) detector, and unfolded using the two codes BUNKI and MAXED. The BON unfolding algorithm is used with BUNKI. It has been observed that end test percentage between 1 and 3 and smoothing factor between 0.05 and 0.1 are optimal choices for the BUNKI code. A temperature parameter 1.0 is used for MAXED. Comparison with standard spectra shows that the shape of the spectra is fairly well reproduced. A coupling between the two codes is made and the solution spectrum from BUNKI is used as the default spectrum in MAXED. PMID:15353708

Esposito, Adolfo; Nandy, Maitreyee

2004-01-01

44

Validation of neutron data libraries by comparison of measured and calculated neutron leakage spectra  

NASA Astrophysics Data System (ADS)

Neutron spectra from the 2H(d,n)3He and 9Be(d,n)10B neutron source reactions and a Pu-Be source were measured by a pulse height response spectrometer behind slabs of water, graphite, sand, Pb, Al and Fe up to 20cm thicknesses. A comparison of the measured and the calculated data has given new results for the validation of different data libraries.

Jordanova, J.; Oláh, L.; Fenyvesi, A.; El-Megrab, A. M.; ElAgib, I.; Darsono,; Klein, U.; Csikai, J.

1999-02-01

45

Neutron source images and spectra to guide neutron diagnostics specifications for the National Ignition Facility  

SciTech Connect

Both neutron images and spectra will diagnose ignition implosions at the National Ignition Facility. From the integrated Hohlraum and capsule calculations of copper-doped beryllium capsules using {approx}1 MJ of laser energy we have postprocessed neutron spectra and both energy-gated and time integrated neutron images displaying the observable consequences of two-dimensional Hohlraum asymmetries. If low signal precludes multiple down scattered images, we suggest a 6-12 MeV gate. With asymmetries, it is noted that the neutron yield, spectra, and images vary with observation direction. The yield varies only several percent when observed at different angles. Since most asymmetries are expected about the Hohlraum axis, a perpendicular view has the highest priority. The next most informative view would be along the Hohlraum axis, but may be precluded by target chamber structures. We present images at the available port angles and discuss their utility. To facilitate detailed diagnostic simulations with real pinhole geometries or penumbral apertures, we offer a compact disk containing neutron spectra and gated images from various integrated calculations.

Sweezy, J. E.; Wilson, D. C.; Bradley, P. A.; Grim, G. P.; Choi, C. K.; Coggeshall, J. C.; Wilde, C. H.; Forster, R. A.; Russell, R. D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-10-15

46

NEUTRON ACTIVATION AT 195 kev  

Microsoft Academic Search

Neutron activation cross sections were measured at 195 kev (50 kev ; energy spread) for about 30 isotopes, bY absolute gamma counting. Absolute ; calibration was effected by determining the RdTh-DâO neutron source ; strength with a flat response 4 pi graphite sphere neutron counter, and ; irradiating indium in the form of a thin, uniform, spherical shell. The results

W. S. Lyon; R. L. Macklin

1959-01-01

47

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

Microsoft Academic Search

The Bonner sphere spectrometers (BSS) are commonly used to determine the neutron spectra within various nuclear facilities. Sophisticated mathematical tools are used to unfold the neutron energy distribution from the output data of the BSS. This paper highlights a novel high-resolution neutron spectra-unfolding method using the Genetic Algorithm (GA) technique. The GA imitates the biological evolution process prevailing in the

Bhaskar Mukherjee

2002-01-01

48

Neutron Activation Data for Neutron Interrogation  

SciTech Connect

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. [Nuclear Engineering Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Micklich, Bradley J. [Intense Pulse Neutron Source, Argonne National Laboratory, Argonne, IL 60439 (United States)

2005-05-24

49

Energy spectra of solar cosmic rays according to balloon and neutron monitor data  

Microsoft Academic Search

The energy spectra of solar protons were obtained in the range from 100 MeV to several GeV on the basis of joint analysis of stratospheric and neutron-monitor measurements. The most powerful events of 1976-1982 were found occurring during the increasing and declining phases of the solar activity cycle. In the event of October 12, 1981, an additional source of fast

G. A. Bazilevskaia; P. N. Lebedev; M. S. Grigorian; T. N. Charakchian

1983-01-01

50

Fusion neutronics-streaming, shielding, heating, activation  

NASA Astrophysics Data System (ADS)

The International Thermonuclear Experimental Reactor (ITER) represents an important step towards a fusion power plant. Controlled fusion will be realized in a d-t-plasma magnetically confined by a Tokamak configuration. The first wall of the plasma chamber, blanket and vacuum vessel of ITER form a compact assembly for converting the kinetic energy of fusion neutrons into heat while simultaneously shielding the superconducting coils efficiently against neutron and accompanying photon radiation. This shielding system can be investigated with neutrons generated by low-energy accelerators. We report on experiments concerning shielding and streaming properties of a mock-up where energy spectra of both neutrons and protons were measured. They are compared with predictions of Monte Carlo calculations (code MCNP-4A) using various data libraries. The agreement justified the use of measured spectra as basis to calculate design parameters such as neutron and photon heating, radiation damage, gas production, and activation. Some of these parameters were also directly measured. The results validate the ITER design. .

Freiesleben, H.; Richter, D.; Seidel, K.; Unholzer, S.

2001-07-01

51

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

52

Equilibrium delayed neutron spectra from fast fission of uranium-235, uranium-238, and plutonium-239  

Microsoft Academic Search

A ³He neutron spectrometer has been used to measure the energy spectra of delayed neutrons in equilibrium with fission induced by sub-MeV neutrons incident upon ²³⁵U, ²³⁸U, and ²³⁹Pu. Full contribution of shorter lived delayed neutron groups not previously measured was ensured by bombarding samples for 35 out of every 100 ms and measuring delayed neutrons for 40 ms between

A. E. Evans; M. S. Krick

1977-01-01

53

Performance comparison of bonner sphere response matrices by unfolding UARK SRCC neutron spectra  

Microsoft Academic Search

Determining the energy-dependent dose equivalent for neutrons is a difficult problem. The slowing-down process that neutrons undergo in moderating detectors destroys their incident energy information, causing the detector response to be a complicated function of energy. The improvement of neutron dosimetry requires experimental determination of neutron energy spectra in irradiation environments. Bonner spheres, which consist of a thermal-neutron scintillator and

E. C. Lemley

1994-01-01

54

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

PubMed

The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The accelerator-based (7)Li(p,n)(7)Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell-Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell-Boltzmann distributions is successfully introduced. PMID:22732394

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

2012-05-17

55

Atmospheres and spectra of strongly magnetized neutron stars  

NASA Astrophysics Data System (ADS)

We construct atmosphere models for strongly magnetized neutron stars with surface fields [formmu10]B~1012-1015G and effective temperatures [formmu11]Teff~106-107K. The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free-free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron-ion plasma. Since the radiation emerges from deep layers in the atmosphere with [formmu12]?>~102gcm-3, plasma effects can significantly modify the photon opacities by changing the properties of the polarization modes. In the case where the magnetic field and the surface normal are parallel, we solve the full, angle-dependent, coupled radiative transfer equations for both polarization modes. We also construct atmosphere models for general field orientations based on the diffusion approximation of the transport equations and compare the results with models based on full radiative transport. In general, the emergent thermal radiation exhibits significant deviation from blackbody, with harder spectra at high energies. The spectra also show a broad feature [formmu13](?E/EBi~1) around the ion cyclotron resonance [formmu14]EBi=0.63(Z/A)(B/1014G)keV, where Z and A are the atomic charge and atomic mass of the ion, respectively; this feature is particularly pronounced when [formmu15]EBi>~3kTeff. Detection of the resonance feature would provide a direct measurement of the surface magnetic fields on magnetars.

Ho, Wynn C. G.; Lai, Dong

2001-11-01

56

Neutron Spectra from Intermediate-Energy Nucleus-Nucleus Reactions  

SciTech Connect

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 [GSI, Planckstr. 1, 64291 Darmstadt (Germany); Iwata, Yoshiyuki [National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Nakamura, Takashi [Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Gudima, Konstantin [Institute of Applied Physics, Academy of Science of Moldova, Chisinau, MD-2028 (Moldova, Republic of); Mashnik, Stepan; Sierk, Arnold; Prael, Richard [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2005-05-24

57

NEUTRON ENERGY SPECTRA FROM NUCLEI EXCITED BY $mu$⁻MESON CAPTURE (thesis)  

Microsoft Academic Search

The neutron energy spectra from nuclear capture of mu mesons in Al, Ca, ; Fe, Ag, I, Au, and Pb were measured. Nuclear temperatures were deduced from the ; spectra according to the Weisskopf evaporation theory. Results were compared to ; other experimental measurements and consistency with compound nuclear theory was ; discussed. The direct neutron emission spectrum was calculated

Hagge

1963-01-01

58

Reconstruction of Neutron and Deuteron Energy Spectra in Z-pinch Experiments  

NASA Astrophysics Data System (ADS)

The neutron energy spectra were reconstructed in Z-pinch experiments where deuterium atoms were present in a load. The reconstruction was based on the time-of-flight method in which time-resolved neutron detectors were placed at various distances from the neutron source. There are several theoretical approaches to the development of reconstruction algorithms (Monte Carlo, etc.). The improved Monte Carlo reconstruction technique, which simultaneously used neutron detectors placed on two opposite sites from the source, was applied to process data from experiments on the S-300 generator (Kurchatov Institute, Moscow). Since these experiments contained a small number of neutron detectors in one direction, a specific reconstruction procedure was used. From the reconstructed neutron energy spectra, also the energy distribution function of deuterons producing fusion neutrons could be calculated. The characteristics of the neutron scintillation detector and the influence of scattered neutrons were taken into account to estimate the error in the reconstruction.

Rezac, Karel; Klir, Daniel; Kubes, Pavel; Kravarik, Josef

2007-11-01

59

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

60

Neutron Energy-Deposition Spectra Measurements, and Comparisons with Geant4 Predictions  

Microsoft Academic Search

Comparisons arc presented between measured and predicted energy deposition spectra from neutron-nuclear events within a silicon semiconductor detector. Experiment data are from irradiations performed at the TRIUMF and TSL neutron beam facilities. Predictions are based on the Geant4 radiation transport toolkit, which is applied both to quantify the effects of interactions in the detector and scattering of the neutron source

P. Truscott; C. Dyer; A. Frydland; A. Hands; S. Clucas; K. Hunter

2005-01-01

61

Neutron Energy-Deposition Spectra Measurements, and Comparisons with Geant4 Predictions  

Microsoft Academic Search

Comparisons are presented between measured and predicted energy deposition spectra from neutron-nuclear events within a silicon semiconductor detector. Experiment data are from irradiations performed at the TRIUMF and TSL neutron beam facilities. Predictions are based on the Geant4 radiation transport toolkit, which is applied both to quantify the effects of interactions in the detector and scattering of the neutron source

Pete Truscott; Clive Dyer; Adam Frydland; Alex Hands; Simon Clucas; Karen Hunter

2006-01-01

62

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

63

Prompt Pulsed Neutron Activation Analysis for Detection of Fission Neutrons  

Microsoft Academic Search

A pulsed-neutron interrogation technique for detection of Special Nuclear Material (SNM) is described. The technique combines timing techniques from pulsed prompt gamma neutron activation analysis with silicon carbide (SiC) semiconductor fast neutron detector technology. SiC detectors can operate during and within nanoseconds of the end of an intense neutron pulse, providing the ability to detect the prompt neutron emissions from

Frank H. Ruddy; John G. Seidel; Robert W. Flammang

2006-01-01

64

Neutron activated switch  

DOEpatents

A switch for reacting quickly to a neutron emission. A rod consisting of fissionable material is located inside a vacuum tight body. An adjustable contact is located coaxially at an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod causes it to heat and expand longitudinally until it comes into contact with the adjustable contact. This circuit closing occurs within a period of a few microseconds.

Barton, David M. (Espanola, NM)

1991-01-01

65

Neutron activated switch  

DOEpatents

A switch for reacting quickly to a neutron emission in which a rod consisting of a rod of fissionable material inside a vacuum tight body. An adjustable contact is located coaxially an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod will cause it to heat and expand longitudinally until it comes into contact with the adjustable contact. This closing occurs within a period of a few microseconds. 2 figs.

Barton, D.M.

1989-10-30

66

Enhanced NIF neutron activation diagnostics  

SciTech Connect

The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the {sup 89}Zr/{sup 89m}Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

Yeamans, C. B.; Bleuel, D. L.; Bernstein, L. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2012-10-15

67

Chemical weapons detection by fast neutron activation analysis techniques  

NASA Astrophysics Data System (ADS)

A neutron diagnostic experimental apparatus has been tested for nondestructive verification of sealed munitions. Designed to potentially satisfy a significant number of van-mobile requirements, this equipment is based on an easy to use industrial sealed tube neutron generator that interrogates the munitions of interest with 14 MeV neutrons. Gamma ray spectra are detected with a high purity germanium detector, especially shielded from neutrons and gamma ray background. A mobile shell holder has been used. Possible configurations allow the detection, in continuous or in pulsed modes, of gamma rays from neutron inelastic scattering, from thermal neutron capture, and from fast or thermal neutron activation. Tests on full scale sealed munitions with chemical simulants show that those with chlorine (old generation materials) are detectable in a few minutes, and those including phosphorus (new generation materials) in nearly the same time.

Bach, P.; Ma, J. L.; Froment, D.; Jaureguy, J. C.

1993-06-01

68

Signature of the ?(1405) Resonance in Neutron Spectra from the K - + d Reaction  

NASA Astrophysics Data System (ADS)

Neutron spectra from the reaction were calculated in the energy range 0-50 MeV using coupled channel Faddeev equations for the description of the three-body system. The aim was to trace the signature of the ?(1405) resonance in the spectra. We found, that while in the direct spectra kinematic effects mask completely the peak corresponding to the resonance, the deviation spectrum method of Esmaili et al. (Phys. Rev. C 83:055207, 2011) is able to eliminate kinematics and differentiate between different models of ?(1405). Four different phenomenological interactions were used in order to study the effect of their pole positions on the neutron spectra.

Révai, János

2013-11-01

69

Selective activation analysis with ion-beam-tailored neutron spectra - A comparison between the reactions 7 Li(p, n)7Be and 9Be(p, n)9B  

NASA Astrophysics Data System (ADS)

When endoergic (p, n) reactions are used for the production of neutrons, the energy distribution of the neutron flux depends on the energy of the protons. By changing the proton energy, certain neutron reactions are selectively excited. This effect can then be used to determine particular elements in matrices that contribute overwhelming interference when the conventional techniques of thermal- or fast-neutron activation analysis are applied. For example, reactions that produce isomeric states through inelastic scattering have maxima in their excitation functions at energies of a couple of MeV, while (n, p) and (n, ?) reactions typically have thresholds above this region. The two targets for neutron production most appropriate for this method are lithium and beryllium. According to the literature, the reaction 7Li(p, n)7Be is a more prolific source of neutrons at proton energies below 6 MeV. On the other hand, high beam powers are necessary for practical applications and lithium metal has a melting point of 179° C in contrast with 1278°C in the case of beryllium. In this work, the response of the inelastic scattering reaction 197Au(n, n')197mAu as well as interfering threshold and neutron capture reactions in a silicate matrix have been studied for neutrons produced by proton reactions on a lithium target and compared with work, reported by us previously, for a beryllium target. The results indicate that, for thick targets, the advantages of using beryllium outweigh the disadvantages and that a suitable high-current accelerator equipped with a beryllium target would be able to determine gold rapidly at the low ppm level in a silicate matrix. The ultimate limit of detection for elements in a matrix containing aluminium, such as a rock, is dependent on interference produced by the neutron capture reaction 27Al(n, ?)28Al. Ways of reducing this interference are discussed.

Watterson, J. I. W.; Pillay, A. E.; Nailand, P.

1990-01-01

70

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

PubMed

The neutron spectra have been measured in two beam ports, one radial and another tangential, of the TRIGA Mark III nuclear reactor from the National Institute of Nuclear Research in Mexico. Measurements were carried out with the reactor core loaded with high enriched uranium fuel. Two reactor powers, 5 and 10W, were used during neutron spectra measurements using a Bonner sphere spectrometer with a (6)LiI(Eu) scintillator and 2, 3, 5, 8, 10 and 12 in.-diameter high-density polyethylene spheres. The neutron spectra were unfolded using the NSDUAZ unfolding code. For each spectrum total flux, mean energy and ambient dose equivalent were determined. Measured spectra show fission, epithermal and thermal neutrons, being harder in the radial beam port. PMID:23746708

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

2013-05-22

71

Neutronics and activation calculation for ITER generic site safety report  

Microsoft Academic Search

This paper focuses on some of the response functions obtained from a Sn radiation transport and activation analysis, namely the nuclear heating, decay heat and clearance index due to the neutron irradiation in the International Thermonuclear Experimental Reactor (ITER) fusion machine. The neutron and gamma flux spectra were calculated using the Scale 4.4a transport sequence Bonami-Nitawl-Xsdnrpm with a new 175n–42?-coupled

D. G Cepraga; G Cambi; F Carloni; M Frisoni; D Ene

2002-01-01

72

Leakage neutron spectra from spherical samples with a Pu–Be source  

Microsoft Academic Search

Leakage neutron spectra from a Pu–Be source placed in the center of a 30 cm diameter sphere filled with water, paraffin oil, SiO2 and river sand were measured using a pulse height response spectrometer (PHRS) in the 1.4–12.0 MeV energy range. The measured leakage neutron spectra have been compared with the calculated results obtained by the three dimensional Monte Carlo

I ElAgib; J Csikai; J Jordanova; L Oláh

1999-01-01

73

Calculated /alpha/-induced thick target neutron yields and spectra, with comparison to measured data  

SciTech Connect

One component of the neutron source associated with the decay of actinide nuclides in many environments is due to the interaction of decay /alpha/ particles in (/alpha/,n) reactions on low Z nuclides. Measurements of (/alpha/,n) thick target neutron yields and associated neutron spectra have been made for only a few combinations of /alpha/ energy and target nuclide or mixtures of actinide and target nuclides. Calculations of thick target neutron yields and spectra with the SOURCES code require /alpha/-energy-dependent cross sections for (/alpha/,n) reactions, as well as branching fractions leading to the energetically possible levels of the product nuclides. A library of these data has been accumulated for target nuclides of Z /le/ 15 using that available from measurements and from recent GNASH code calculations. SOURCES, assuming neutrons to be emitted isotopically in the center-of-mass system, uses libraries of /alpha/ stopping cross sections, (/alpha/,n) reaction cross reactions, product nuclide level branching fractions, and actinide decay /alpha/ spectra to calculate thick target (/alpha/,n) yields and neutron spectra for homogeneous combinations of nuclides. The code also calculates the thick target yield and angle intergrated neutron spectrum produced by /alpha/-particle beams on targets of homogeneous mixtures of nuclides. Illustrative calculated results are given and comparisons are made with measured thick target yields and spectra. 50 refs., 1 fig., 2 tabs.

Wilson, W.B.; Bozoian, M.; Perry, R.T.

1988-01-01

74

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

Microsoft Academic Search

Determining the time dependent concentration of isotopes within a nuclear reactor core is central to the analysis of nuclear fuel cycles. We present a fast, flexible tool for determining the time dependent neutron spectrum within fast reactors. The code (VBUDS: visualization, burnup, depletion and spectra) uses a two region, multigroup collision probability model to simulate the energy dependent neutron flux

Geoff Recktenwald; Mark Deinert

2010-01-01

75

Vibration Spectra of Yttrium and Uranium Hydrides by the Inelastic Scattering of Cold Neutrons  

Microsoft Academic Search

The vibration spectra of the hydrides and deuterides of yttrium and uranium have been investigated by the energy-gain scattering of cold neutrons. The measured spectra are all split into two bands, one at higher energies, due to the optical hydrogen vibrations, and another at lower energies due to metal—atom vibrations. Values have been obtained for the peaks and widths of

J. J. Rush; H. E. Flotow; D. W. Connor; C. L. THAPERt

1966-01-01

76

Reevaluation of secondary neutron spectra from thick targets upon heavy-ion bombardment  

NASA Astrophysics Data System (ADS)

Previously published data of secondary neutron spectra from thick targets of C, Al, Cu and Pb bombarded with heavy ions from He to Xe are revised by using a new set of neutron-detection efficiency values for a liquid organic scintillator calculated with SCINFUL-QMD. Additional data have been measured for bombardment of C target by 400-MeV/nucleon C ions and 800-MeV/nucleon Si ions. The set of spectra are compared with the calculation results using a Monte-Carlo heavy-ion transport code, PHITS. It was found that PHITS is able to reproduce the secondary neutron spectra in a wide neutron-energy regime.

Satoh, D.; Kurosawa, T.; Sato, T.; Endo, A.; Takada, M.; Iwase, H.; Nakamura, T.; Niita, K.

2007-12-01

77

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

78

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

79

Inversion of neutron\\/gamma spectra from scintillator measurements  

Microsoft Academic Search

The Radiation Assessment Detector (RAD) on-board NASA’s Mars Science Laboratory (MSL) rover will measure charged particles as well as neutron and gamma radiation on the Martian surface. Neutral particles are an important contribution to this radiation environment. RAD measures them with a CsI (Tl) and a plastic scintillator, which are both surrounded by an anticoincidence. The incident neutron\\/gamma spectrum is

J. Köhler; B. Ehresmann; C. Martin; E. Böhm; A. Kharytonov; O. Kortmann; C. Zeitlin; D. M. Hassler; R. F. Wimmer-Schweingruber

2011-01-01

80

EUV/soft x-ray spectra for low B neutron stars  

SciTech Connect

Recent ROSAT and EUVE detections of spin-powered neutron stars suggest that many emit ``thermal`` radiation, peaking in the EUV/soft X-ray band. These data constrain the neutron stars` thermal history, but interpretation requires comparison with model atmosphere computations, since emergent spectra depend strongly on the surface composition and magnetic field. As recent opacity computations show substantial change to absorption cross sections at neutron star photospheric conditions, we report here on new model atmosphere computations employing such data. The results are compared with magnetic atmosphere models and applied to PSR J0437-4715, a low field neutron star.

Romani, R.W.; Rajagopal, M. [Stanford Univ., CA (United States). Dept. of Physics; Rogers, F.J.; Iglesias, C.A. [Lawrence Livermore National Lab., CA (United States)

1995-05-23

81

NEUTRON GENERATOR OUTPUT MONITORING FOR NORMALIZATION OF GAMMA-RAY SPECTRA.  

SciTech Connect

Neutron generators (NG) being devices where neutron outputs are accomplished electrically, suffer from fluctuations in their outputs. Of particular importance are the short term variations that may affect individual data acquisition runs. Thus when using NGs for quantitative neutron-induced gamma-ray spectroscopy, the neutron output must be continuously monitored in real time, and normalization procedures subsequently applied to properly evaluate the gamma-ray spectra. Using a plastic scintillator, we developed a scheme for detecting fast neutrons that relies firstly, on recording a spectrum and, secondly, on establishing a region-of-interest (ROI) that may effectively discriminate against gamma rays that are always present in a neutron field. We discuss the optimization of these procedures for a field system to measure carbon in soil.

MITRA,S.; WIELOPOLSKI, L.

2006-05-08

82

X-ray spectra from convective photospheres of neutron stars.  

National Technical Information Service (NTIS)

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 ir...

V. E. Zavlin G. G. Pavlov Y. Shibanov F. J. Rogers C. A. Iglesias

1996-01-01

83

Study of degraded neutron spectra through metal matrix composites using CR-39 films  

NASA Astrophysics Data System (ADS)

Considerable interest has grown in the last decade in the use of CR-39 films in routine neutron monitoring and dosimetry. In addition, work in neutron spectrometry has been undertaken by various workers ([Decossas et al., 1984]; [Faermann et al., 1983]; [Fews et al., 1984]; [Turner et al., 1984]). In the present study metal matrix composites (MMC) samples of Pb-Li, Pb-Cd, Al-Li and Al-B4C were prepared by using powder metallurgy and alloying elements techniques. The density was obtained for these MMC samples in the range of 80-90% of the metal density. Degraded neutron spectra were obtained by exposing these samples to a 252Cf source housed in a camera and the detector used was CR-39 films covered with a 1mm PE radiator. These spectra have also been validated through [Monte Carlo Neutron and Photon Transport Code (1983)].

Gopalani, D.; Kumar, S.; Ramaseshu, P.; Sundaram, V. K.; Mehta, S. K.

1998-06-01

84

Inclusive neutron spectra from the absorption of stopped negative pions in heavy nuclei  

NASA Astrophysics Data System (ADS)

Energy spectra of neutrons emitted after the absorption of stopped negative pions in heavy nuclei from 165Ho to 238U have been measured and interpreted in terms of models for pion absorption on a peripheral nucleon pair and subsequent secondary reactions. The mean number of evaporation, direct and total neutrons, their mean energies and nuclear temperature parameters have been deduced from the inclusive neutron spectra. The extracted nuclear temperatures and level density parameters for heavy nuclei show no shell effects in the energy region excited by the stopped pion reaction. For 238U the ratio of pre- to post-fission neutron yields has been deduced from the experimental data. Address from Sept. 1981: Department of Physics, Rensselaer Polytechnic Institute, Troy, New York 12181, USA.

Isaak, H. P.; Zglinski, A.; Engfer, R.; Hartmann, R.; Hermes, E. A.; Pruys, H. S.; Schlepütz, F. W.; Kozlowski, T.; Sennhauser, U.; Walter, H. K.; Junker, K.; Mukhopadhyay, Nimai C.

1983-01-01

85

Absorption features in the spectra of X-ray bursting neutron stars  

Microsoft Academic Search

Context: The discovery of photospheric absorption lines in XMM-Newton spectra of the X-ray bursting neutron star in EXO 0748-676 by Cottam and collaborators allows us to constrain the neutron star mass-radius ratio from the measured gravitational redshift. A radius of R=9{-}12 km for a plausible mass range of M=1.4{-}1.8 M_&sun; was derived by these authors. Aims: It has been claimed

Thomas Rauch; Valery Suleimanov; Klaus Werner

2008-01-01

86

Experimentally determined neutron and gamma-ray spectra from an encapsulated CmâOâ power source  

Microsoft Academic Search

The experimentally determined neutron and gamma ray spectra of a Cm\\/sub ;\\u000a 2\\/Oâ spontaneously fissioning source are presented. The neutron spectrum ;\\u000a is given for the energy range 30 keV to 10 MeV, while the gamma ray spectrum ;\\u000a spans the energy range 205 keV to 12 MeV. (auth)

Freestone; R. M. Jr

1974-01-01

87

Gamma-ray spectra and decay heat following U-235 thermal neutron fission  

NASA Astrophysics Data System (ADS)

Gamma-ray energy spectra have been measured for aggregate fission products resulting from the thermal neutron- induced fission of 235Su. The measurements were performed using a well shielded 5/prime' x 5/prime' NaI(Tl) spectrometer in conjunction with beta-gamma gating for background reduction and for precise definition of the delay times spanning a range 0.25-14000s, with approximately three mean delay times per decade. Fission products were transferred to the detectors by a helium-jet/tape transport system, providing the capability for measurements at much shorter delay times than have been previously reported. Gamma-ray spectra were unfolded using a library of measured spectrometer response functions and the programs NGRC and CRSUP, developed as part of this project, to obtain the gamma-ray energy distribution for each delay time. The relative gamma-ray decay heat was determined from the average energy of each distribution in combination with the measured gamma-to-beta activity ratio and the relative beta activity as a function of delay time. This decay heat has been compared with summation calculations using the CINDER10 program and ENDF/B-VI fission-product data, as well as with the results of previous studies.

Nguyen, Hung Van

1997-09-01

88

Development of methods for processing spectra of multiple small-angle neutron scattering  

NASA Astrophysics Data System (ADS)

A method has been developed for processing spectra of multiple small-angle neutron scattering (MSANS) to obtain information about substance heterogeneities, namely, their size and concentration. A method has been proposed for constructing the dependence of the MSANS line width on the sample thickness starting from the angular neutron distribution measured for one sample. The standard method for processing this dependence has been improved for application at any scattering multiplicity and complete account for the instrumental line of the double-crystal spectrometer. The method has been tested for the MSANS spectra of the samples of the Fe-Ni ferromagnet, Al powders, and HTSC ceramics.

Elyutin, N. O.; L'vov, D. V.; Tyulyusov, A. N.

2012-04-01

89

Neutron spectra from monoenergetic source neutrons after multiple reflection between plane-parallel concrete interfaces  

Microsoft Academic Search

Monte Carlo calculations have been performed for neutrons reflecting between two Type 04 concrete plane-parallel interfaces. A new 23-group albedo data base (SAIL) was used in conjunction with the MORSE code to calculate the neutron spectrum at each reflection. It was found that, after thermalization, for the same order of reflection, the number of neutrons in the cavity is dependent

W. K. Hagan; G. L. Simmons

1980-01-01

90

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

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.

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

2009-01-01

92

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

NASA Astrophysics Data System (ADS)

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

Drake, Darrell

1993-03-01

93

Measurement of cold neutron spectra using a model cryogenic moderator of the IBR-2M reactor  

NASA Astrophysics Data System (ADS)

The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures of 10-50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the IBR-2M reactor and to obtain the cold neutron yield as a function of the moderator temperature. Satisfactory agreement between the experimental and calculated neutron spectra at a mesitylene temperature of 20 K has been obtained; the ratio of cold neutron intensities at 10 and 50 K is ˜1.8.

Kulikov, S. A.; Kalinin, I. V.; Morozov, V. M.; Novikov, A. G.; Puchkov, A. V.; Chernikov, A. N.; Shabalin, E. P.

2010-01-01

94

Neutron spectra evaluation obtained from the track-size distribution on electrochemically etched CR-39 foils  

SciTech Connect

We are studying the relationship between neutron energy and track-size distribution on electrochemically etched CR-39 foils using a two-stage etching procedure. Although the electrochemical etching process alters the track size, we now find that the track diameter is related to the neutron energy even after the second stage (blowup) is completed. This relationship is complex, being effected by the etching parameters, including oven temperature, etching high voltage, and etching time. Current studies are directed at establishing the effect of each of these parameters on the track-size distribution and at determining an optimal etching procedure for neutron spectra evaluation. If neutron spectral information can be determined from the track-size distribution, dose can be calculated directly from the neutron fluence and spectrum.

Hankins, D.E.; Westermark, J.

1987-05-01

95

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.

96

Neutron spectra at different High Flux Isotope Reactor (HFIR) pressure vessel surveillance locations  

SciTech Connect

This project addresses the potential problem of radiation embrittlement of reactor pressure vessel (RPV) supports. Surveillance specimens irradiated at the High Flux Isotope Reactor (HFIR) at relatively low neutron flux levels (about 1.5E + 8 cm{sup {minus}2}.s{sup {minus}1}) and low temperatures (about 50{degrees}C) showed embrittlement more rapidly than expected. Commercial power reactors have similar flux levels and temperatures at the level vessel support structures. The purposes of this work are to provide the neutron fluence spectra data that are needed to evaluate previously measured mechanical property changes in the HFIR, to explain the discrepancies in neutron flux levels between the nickel dosimeters and two other dosimeters, neptunium and beryllium, and to address any questions or peculiarities of the HFIR reactor environment. The current work consists of neutron and gamma transport calculations, dosimetry measurements, and least-squares logarithmic adjustment to obtain the best estimates for the neutron spectra and the related neutron exposure parameters. The results indicate that the fission rates in neptunium-237 (Np-237) and uranium-238 (U-238) and the helium production rates in beryllium-9 (Be-9) are dominated by photo-induced reactions. The displacements per atom rate for iron (dpa/s) from gamma rays is five times higher than the dpa/s from neutrons. The neutron fluxes in key 7, position 5 do not show any significant gradient in the surveillance capsule, but key 4 and key 2 showed differences in magnitude as well as in the shape of the spectrum. The stainless steel monitor in the V-notch of the Charpy specimens of the surveillance capsules is adequate to determine the neutron flux above 1.0 MeV at the desired V-notch location. Simultaneous adjustment of neutron and gamma fluxes with the measurements has been demonstrated and should avoid future problems with photo-induced reactions.

Remec, I. [Josef Sefan Inst., Ljubljana (Slovenia); Kam, F.B. [Oak Ridge National Lab., TN (United States)

1993-12-01

97

Neutronics activities for next generation devices  

SciTech Connect

Neutronics activities for the next generation devices are the subject of this paper. The main activities include TFCX and FPD blanket/shield studies, neutronics aspects of ETR/INTOR critical issues, and neutronics computational modules for the tokamak system code and tandem mirror reactor system code. Trade-off analyses, optimization studies, design problem investigations and computational models development for reactor parametric studies carried out for these activities are summarized.

Gonar, Y.

1985-07-01

98

Neutronics activities for next generation devices  

SciTech Connect

Neutronic activities for the next generation devices are the subject of this paper. The main activities include TFCX and FPD blanket/shield studies, neutronic aspects of ETR/INTOR critical issues, and neutronics computational modules for the tokamak system code and tandem mirror reactor system code. Trade-off analyses, optimization studies, design problem investigations and computational models development for reactor parametric studies carried out for these activities are summarized.

Gohar, Y.

1985-01-01

99

Accelerator-based neutron fields for the mock up of workplace spectra - first experimental results and comparison with calculations  

NASA Astrophysics Data System (ADS)

The energy dependence of the fluence response of a neutron radiation protection monitor generally deviates considerably from that of the fluence-to-dose equivalent conversion function. For the dose determination in a given neutron field such a monitor must therefore be calibrated by determining its yield and the dose equivalent in a neutron field similar to the given field. A wide class of neutron fields encountered at workplaces can be characterized by a superposition of thermal neutrons, a /1/E part in the region of intermediate neutron energies and, occasionally, some high-energy neutrons, e.g. remains of down-scattered fission neutrons. Our approach is to mock up appropriate neutron calibration fields by the production of neutrons in an Li(p,n) reaction (thick target) and the modification of these initial spectra with a moderator assembly consisting of two spherical shells of polyethylene and graphite, respectively. We optimized this set-up by numerical simulation of the neutron spectra with the MCNP Monte Carlo code. Spectra were calculated for the primary and for the moderated source under different angles /?, referring to the direction of the incoming protons. The achieved values of the mean fluence-to-ambient dose equivalent conversion coefficients, /, range from 276 down to 16pSvcm2. We present results of first measurements with Bonner spheres in the proposed neutron fields. We compare calculated count rates - i.e. folding the simulated neutron spectra with the Bonner sphere response functions - and the measured count rates.

Wiegel, B.; Siebert, B. R. L.; Guldbakke, S.; Wittstock, J.

1999-02-01

100

Atmospheres and Spectra of Strongly Magnetized Neutron Stars  

NASA Astrophysics Data System (ADS)

We construct atmosphere models for strongly magnetized neutron stars with surface fields B ˜1012 -1015 G and effective temperatures Teff ˜106 - 107 K. The atmospheres directly determine the characteristics of thermal emission from isolated neutron stars, including radio pulsars, soft gamma-ray repeaters, and anomalous X-ray pulsars. In our models, the atmosphere is composed of pure hydrogen or helium and is assumed to be fully ionized. The radiative opacities include free-free absorption and scattering by both electrons and ions computed for the two photon polarization modes in the magnetized electron-ion plasma. We describe a modified (due to the two photon modes) Unsöld-Lucy temperature correction method to establish radiative equilibrium and the resulting temperature profile. We discuss the effect of vacuum polarization, which modifies the dielectric property of the medium and gives rise to a resonance feature in the opacity; this feature is narrow and occurs at a photon energy that depends on the plasma density. Vacuum polarization can also induce resonant conversion of photon modes via a mechanism analogous to the MSW mechanism for neutrino oscillation. We discuss the subtleties in treating the vacuum polarization effects. We show that vacuum polarization produces a broad depression in the X-ray flux at high energies, which arises from the density dependence of the vacuum resonance feature and the large density gradient present in the atmosphere, and the depression of continuum flux strongly suppresses the equivalent width of the ion cyclotron line.

Ho, W. C. G.; Lai, D.

2003-01-01

101

Kermas for various substances averaged over the energy spectra of fast neutron therapy beams: A study in uncertainties  

Microsoft Academic Search

Kermas for various substances averaged over the energy spectra of fast neutron therapy beams, as well as ratios of average kermas relative to muscle, were calculated in an attempt to estimate the uncertainties introduced in these quantities by the poor knowledge of the elemental kerma functions, actual neutron energy spectra, and composition of tissues and other materials. Average kermas have

M. Awschalom; I. Rosenberg; A. Mravca

1983-01-01

102

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

103

Energy spectra of the pneumatically positioned neutron sources at LLNL's Hazards control standards and calibration facility  

SciTech Connect

The Hazards Control Department of Lawrence Livermore National Laboratory maintains a Standards and Calibration Laboratory that includes three neutron sources (two /sup 252/Cf and one /sup 238/PuBe that can be positioned pneumatically for irradiations. Ten moderators exist to modify the neutron energy spectra produced by these sources. The thicknesses and materials of these moderators are: 25-cm water; 5-, 10-, 15-, and 25-cm heavy water; 20-cm aluminum; and 2-, 5-, 10-, and 15-cm polyethylene. We used a multisphere spectrometer to measure the neutron spectra at 2 m from both the PuBe source and the smaller Cf source, with the sources bare, and in all of the moderators. These data were reduced in 25 energy groups ranging from 0.25 eV to 16 MeV. Except for the 15-m polyethylene moderator, we also made measurements using a liquid-scintillator fast-neutron spectrometer. These data were reduced in 0.1-MeV increments from 0.5 to 12.5 MeV. Spectra from the measurements and from independent calculations are presented in tabular and graphic form. Dosimetric values, calculated from both the measured and calculated spectra, are also presented.

Thorngate, J.H.

1987-06-15

104

Controlled thermonuclear reactor neutron spectra simulation at the LAMPF radiation effects facility  

Microsoft Academic Search

An essential element of any fusion or fission reactor materials development effort is the availability of irradiation facilities for conducting radiation effects experiments. A Radiation Effects Facility (REF) was provided for such studies at the Los Alamos Meson Physics Facility. Neutron spectra at the REF can be tailored to approximate those in either a fusion or fission reactor, while providing

M. L. Simmons; D. J. Dudziak

1976-01-01

105

Application of Neural Networks for unfolding neutron spectra measured by means of Bonner Spheres  

Microsoft Academic Search

A Neural Network structure has been used for unfolding neutron spectra measured by means of a Bonner Sphere Spectrometer set. The present work used the “Stuttgart Neural Network Simulator” as the interface for designing, training and validation of a MultiLayer Perceptron network. The back-propagation algorithm was applied. The Bonner Sphere set chosen has been calibrated at the National Physical Laboratory,

Cláudia C. Braga; Mauro S Dias

2002-01-01

106

Concurrent Measurement of Individual Gamma-Ray Spectra During and Between Fast Neutron Pulses  

Microsoft Academic Search

A fast commercial digital multi-channel analyzer (DMCA) with a 40 MHz sampling frequency, was modified for concurrent acquisition during the same data collection run, of two separate gamma-ray spectra induced during and between fast neutron pulses. The DMCA was programmed to monitor the incoming and observed count rates, and the resulting real times and dead times separately for each spectrum.

S. Mitra; L. Wielopolski; H. Tan; A. Fallu-Labruyere; W. Hennig; W. K. Warburton

2007-01-01

107

Prompt Fission Neutron Spectra Measurements From Neutron Induced Fission in ^239Pu And ^235U At Energies Below The Incident Neutron Energy  

NASA Astrophysics Data System (ADS)

Measurements of neutron induced fission neutron spectra (FNS) for ^235U and ^239Pu for energies below that of the incident neutron have been made at the University of Massachusetts Lowell Van de Graaff accelerator lab. The ^7Li(p,n)^7Be reaction produced 1.5 and 2.5 MeV neutrons used to induce fission in a 62 g ^235U sample and a 29 g ^239Pu sample. Measurements of FNS in this region are complicated by the fact that the accelerator produced incident neutrons are elastically and inelastically scattered from the sample with energies in the range of the fission neutrons. In order to enhance the detection of fission neutrons with respect to other neutron types we employed three fast BaF2 scintillation detectors near the scatterer to detect fission gamma rays in coincidence. The fission gamma-ray trigger was then used to gate a BC-501 liquid scintillation neutron detector for FNS acquisition.

Woodring, M. L.; Egan, J. J.; Kegel, G. H. R.; Mittler, A.; Staples, P. A.; Desimone, D. J.; Ko, Y. J.; Souza, D.

1996-10-01

108

Unfolding neutron spectra obtained from BS-TLD system using genetic algorithm.  

PubMed

Due to the variability of neutron spectrum within the same environment, it is essential that the spectral distribution as a function of energy should be characterized. The precise information allows radiological quantities establishment related to that spectrum, but it is necessary that a spectrometric system covers a large interval of energy and an unfolding process is appropriate. This paper proposes use of a technique of Artificial Intelligence (AI) called genetic algorithm (GA), which uses bio-inspired mathematical models with the implementation of a specific matrix to unfolding data obtained from a combination of TLDs embedded in a BS system to characterize the neutron spectrum as a function of energy. The results obtained with this method were in accordance with reference spectra, thus enabling this technique to unfold neutron spectra with the BS-TLD system. PMID:22963980

Santos, J A L; Silva, E R; Ferreira, T A E; Vilela, E C

2012-07-20

109

Effects of Fluid Temperature and Velocity Distributions on Neutron Spectra  

NASA Astrophysics Data System (ADS)

We commonly summarize the spectrum of 14 MeV neutrons produced by a laser fusion capsule by just a yield and a temperature, as if it were a uniform stationary fluid element. However, burn in a real fusion capsule occurs over a wide range of temperatures, and the velocity of the burning fuel is not negligible compared to thermal velocities. Even at low ?r, absent any scattering, these effects cause the shape of the 14 MeV peak to depart significantly from a Gaussian, and cause its width, that is, the observed burn temperature, to vary depending on viewing direction. We describe our ongoing efforts to cope with these complexities in the analysis of data from the National Ignition Facility. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Munro, D. H.; Hatchett, S. P.; Spears, B. K.

2011-11-01

110

Gamma-ray and neutron leakage spectra calculated for unshieled reactors  

SciTech Connect

The spectra of neutrons and gamma rays escaping from unshielded reactors have been calculated for a number of simplified cases. Such spectra are important in connection with reactors operating in space orbit around the earth, which would normally have little or no heavy shielding. Reactors in space, such as the Soviet RORSAT spacecraft. Knowledge of the characteristics of their leakage spectra may be useful in understanding or minimizing such interference. The Monte Carlo Neutron-Photon (MCNP) code developed at Los Alamos has been used in these calculations. In the cases considered here the critical assembly is assumed to have spherically symmetrical geometry, with a central core of fissionable material surrounded by one or more shells of other material. The outer shells considered include beryllium, beryllium oxide, sodium, potassium, lithium, lithium hydride, and iron. The results obtained, presented as graphs, show that a number of materials that may be used in space reactors should lead to distinctive gamma-ray and neutron leakage spectra. Measurements of such spectra might well be useful in characterizing an unknown reactor type. 16 refs., 33 figs.

Terrell, J.

1990-05-01

111

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

112

Determination of phosphorus using derivative neutron activation  

Microsoft Academic Search

For the determination of phosphorus in different matrices, the derivative neutron activation analysis is especially applicable to aqueous samples, since the conventional neutron activation analysis is not useful for the determination of phosphorus. Phosphorus when reacted with ammonium molybdate 4 hydrate and ammonium metavanadate forms molybdo vanado phosphoric acid. This complex is preconcentrated by extracting into methyl isobutyl ketone. The

Y. M. Scindia; A. G. C. Nair; A. V. R. Reddy; S. B. Manohar

2002-01-01

113

Neutron Activation Diagnostics for FRCHX at AFRL  

NASA Astrophysics Data System (ADS)

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 is indium-activation, with an Ortec germanium detector (GEM-10185) coupled to a multichannel analyzer. Indium is sensitive to and provides a count of DD neutrons. The second diagnostic system is Arsenic-activation that will also detect DD neutrons. The third system is Copper-activation, using a sodium iodide (NaI) coincidence system. Only DT neutrons are detected by this system. A fourth system consists of BTI Bubble detectors that are sensitive to both DD and DT neutrons. Thus, four systems will provide an absolute count of DD or DT neutrons from the FRC plasma implosion in FRCHX at the AFRL in Albuquerque later this year.

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

2009-11-01

114

Extraction of Mechanical-Reactivity Influences from Neutron Noise Spectra at the IBR-2 Reactor  

NASA Astrophysics Data System (ADS)

Neutron noise spectra in nuclear reactors are a convolution of multiple-induced reactivities. For the IBR-2 pulsed reactor (JINR-Dubna), one part is represented by the reactivities induced by the two moving reflectors, and the other part by other sources that are moderately stable. In the present study, using recordings of the mechanical noise of the two moving reflectors, their non-linear correlations into the power spectra of the reactor are extracted using statistical analysis. The remaining noise sources are moderately stable noise and can be further monitored by other automated reactor diagnoses.

Dima, M.; Pepelyshev, Yu.

2013-07-01

115

Feasibility of Neutron Activation Analysis on Paper.  

National Technical Information Service (NTIS)

Thermal neutron activation and gamma-ray spectroscopy were used to detect and measure trace elements in alpha-cellulose and ash-free filter paper samples. Each sample was irradiated in a neutron flux of 5 x 10 to the 12th power n/cm sq/sec for periods of ...

F. N. Rodrigues

1968-01-01

116

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

117

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

NASA Astrophysics Data System (ADS)

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 × 105 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)He4 nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T3.

Lee, Sungman; Park, Sangsoon; Lee, Kitae; Cha, Hyungki

2012-12-01

118

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

NASA Astrophysics Data System (ADS)

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 sources can be stored and automatically moved into irradiation position. There are changeable collimators and absorbers to modify the spectrum. In the large hall there are possibilities to study the room scatter, angular dependence of detectors, phantom albedo effect etc. Recently available sources are different Pu-Be (from 105-107n/s yield), Ra-Be and Cf.

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

2002-01-01

119

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

NASA Astrophysics Data System (ADS)

The areal density (?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 ?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.; Stoeckl, C.; Casey, D. T.; Gatu-Johnson, M.; Gardner, S.

2012-10-01

120

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

PubMed

The areal density (?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 ?R measurements and 1-D simulations. PMID:23126921

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; Stoeckl, C; Casey, D T; Gatu-Johnson, M; Gardner, S

2012-10-01

121

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

122

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

SciTech Connect

Boron Neutron Capture Therapy (BNCT) is a promising binary treatment modality for high-grade primary brain tumors (glioblastoma multiforme, GM) and other cancers. BNCT employs a boron-10 containing compound that preferentially accumulates in the cancer cells in the brain. Upon neutron capture by {sup 10}B energetic alpha particles and triton released at the absorption site kill the cancer cell. In order to gain penetration depth in the brain Fairchild proposed, for this purpose, the use of energetic epithermal neutrons at about 10 keV. Phase I/II clinical trials of BNCT for GM are underway at the Brookhaven Medical Research Reactor (BMRR) and at the MIT Reactor, using these nuclear reactors as the source for epithermal neutrons. In light of the limitations of new reactor installations, e.g. cost, safety and licensing, and limited capability for modulating the reactor based neutron beam energy spectra alternative neutron sources are being contemplated for wider implementation of this modality in a hospital environment. For example, accelerator based neutron sources offer the possibility of tailoring the neutron beams, in terms of improved depth-dose distributions, to the individual and offer, with relative ease, the capability of modifying the neutron beam energy and port size. In previous work new concepts for compact accelerator/target configuration were published. In this work, using the Van de Graaff accelerator the authors have explored different materials for filtering and reflecting neutron beams produced by irradiating a thick Li target with 1.8 to 2.5 MeV proton beams. However, since the yield and the maximum neutron energy emerging from the Li-7(p,n)Be-7 reaction increase with increase in the proton beam energy, there is a need for optimization of the proton energy versus filter and shielding requirements to obtain the desired epithermal neutron beam. The MCNP-4A computer code was used for the initial design studies that were verified with benchmark experiments using a proton recoil spectroscopy detection system. Comparison was also made between in phantom {sup 10}BF{sub 3} readings made at the BMRR and those made at the RARAF accelerator facility.

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

1998-11-06

123

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

SciTech Connect

Boron Neutron Capture Therapy (BNCT) is a promising binary treatment modality for high-grade primary brain tumors (glioblastoma multiforme, GM) and other cancers. BNCT employs a boron-10 containing compound that preferentially accumulates in the cancer cells in the brain. Upon neutron capture by {sup 10}B energetic alpha particles and triton released at the absorption site kill the cancer cell. In order to gain penetration depth in the brain Fairchild proposed, for this purpose, the use of energetic epithermal neutrons at about 10 keV. Phase 1/2 clinical trials of BNCT for GM are underway at the Brookhaven Medical Research Reactor (BMRR) and at the MIT Reactor, using these nuclear reactors as the source for epithermal neutrons. In light of the limitations of new reactor installations, e.g. cost, safety and licensing, and limited capability for modulating the reactor based neutron beam energy spectra, alternative neutron sources are being contemplated for wider implementation of this modality in a hospital environment. For example, accelerator based neutron sources offer the possibility of tailoring the neutron beams, in terms of improved depth-dose distributions, to the individual and offer, with relative ease, the capability of modifying the neutron beam energy and port size. In previous work new concepts for compact accelerator/target configuration were published. In this work, using the Van de Graaff accelerator the authors have explored different materials for filtering and reflecting neutron beams produced by irradiating a thick Li target with 1.8 to 2.5 MeV proton beams. However, since the yield and the maximum neutron energy emerging from the Li-7(p,n)Be-7 reaction increase with increase in the proton beam energy, there is a need for optimization of the proton energy versus filter and shielding requirements to obtain the desired epithermal neutron beam. The MCNP-4A computer code was used for the initial design studies that were verified with benchmark experiments using a proton recoil spectroscopy detection system. Comparison was also made between in phantom {sup 10}BF{sub 3} readings made at the BMRR and those made at the RARAF accelerator facility.

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

1999-03-01

124

The synchronous active neutron detection assay system  

SciTech Connect

We have begun to develop a novel technique for active neutron assay of fissile material in spent nuclear fuel. This approach will exploit a 14-MeV neutron generator developed by Schlumberger. The technique, termed synchronous active neutron detection (SAND), follows a method used routinely in other branches of physics to detect very small signals in presence of large backgrounds. Synchronous detection instruments are widely available commercially and are termed ``lock-in`` amplifiers. We have implemented a digital lock-in amplifier in conjunction with the Schlumberger neutron generator to explore the possibility of synchronous detection with active neutrons. The Schlumberger system can operate at up to a 50% duty factor, in effect, a square wave of neutron yield. Results are preliminary but promising. The system is capable of resolving the fissile material contained in a small fraction of the fuel rods in a cold fuel assembly; it also appears resilient to background neutron interference. The interrogating neutrons appear to be non-thermal and penetrating. Work remains to fully explore relevant physics and optimize instrument design.

Pickrell, M.M.; Kendall, P.K.

1994-08-01

125

Activities on Nuclear Data Measurements at Pohang Neutron Facility  

SciTech Connect

We report the activities of the Pohang Neutron Facility which consists of an electron linear accelerator, a water-cooled Ta target, and a 12-m time-of-flight path. It has been equipped with a four-position sample changer controlled remotely by a CAMAC data acquisition system, which allows simultaneous accumulation of the neutron time of flight spectra from 4 different detectors. It can be possible to measure the neutron total cross-sections in the neutron energy range from 0.1 eV to few hundreds eV by using the neutron time-of-flight method. A {sup 6}LiZnS(Ag) glass scintillator was used as a neutron detector. The neutron flight path from the water-cooled Ta target to the neutron detector was 12.1 m. The background level was determined by using notch-filters of Co, In, Ta, and Cd sheets. In order to reduce the gamma rays from bremsstrahlung and those from neutron capture, we employed a neutron-gamma separation system based on their different pulse shapes. The present measurements of several samples (Ta, Mo) are in general agreement with the evaluated data in ENDF/B-VI. We measured the thermal neutron capture cross-sections and the resonance integrals of the {sup 186}W(n,{gamma}){sup 187}W reaction and the {sup 98}Mo(n,{gamma}){sup 99}Mo reaction by the activation method using the {sup 197}Au(n,{gamma}){sup 198}Au monitor reaction as a single comparator. We also report the isomeric yield ratios for the 44 m, gSc isomeric pairs produced from four different photonuclear reactions {sup 45}Sc({gamma},n){sup 44m,g}Sc, {sup nat}Ti({gamma},xn1p){sup 44m,g}Sc, {sup nat}Fe({gamma},xn5p){sup 52m,g}Mn, and {sup 103}Rh({gamma},4n){sup 99m,g}Rh by using the activation method.

Kim, Guinyun [Department of Physics, Kyungpook National University, 1370 Sankyuk-Dong, Buk-Gu, Daegu 702-701 (Korea, Republic of)

2009-03-31

126

Nondestructive neutron activation analysis of basalts.  

National Technical Information Service (NTIS)

Thirty-three samples of basalts from Kanchanaburi and Phrae have been investigated qualitatively and quantitatively. Qualitative analysis of the mineral was performed by X-ray diffraction and neutron activation techniques. The contents of 17 major, minor ...

A. Sangariyavanich N. Sriratprasit

1987-01-01

127

Tissue copper determinations by neutron activation analysis  

PubMed Central

A method is described for the handling of tissue samples for copper determination by neutron activation analysis. The results obtained for normal liver copper estimations compared favourably with results obtained by conventional methods. Images

Todd, A. P.; Thorpe, M. E. C.; Rosenoer, V. M.

1967-01-01

128

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...

129

International Comparison of Means for Measuring Neutron Spectra and Radiation Doses in the IBR-30 Reactor Beam.  

National Technical Information Service (NTIS)

The results of comparison of responses of means for measurement of neutron spectra and radiation doses used in countries-participants of the JINR in a beam of the IBR-30 pulsed fast reactor are presented. The spread of neutron and gamma radiation doses me...

V. E. Aleinikov V. A. Arkhipov V. P. Bamblevskii

1980-01-01

130

Measurements of keV-Neutron Capture Cross Sections and Capture Gamma-Ray Spectra of Se  

Microsoft Academic Search

The neutron capture cross sections and capture ?-ray spectra of Se were measured in a region from 15 to 100 keV and at around 510 keV. A neutron time-of-flight method was used with a ns-pulsed neutron source based on the Li(p,n) Be reaction and with a large anti-Compton NaI(Tl) ?-ray spectrometer. A pulse-height weighting technique was applied to the observed

So KAMADA; Masayuki IGASHIRA; Tatsuya KATABUCHI; Motoharu MIZUMOTO

2010-01-01

131

A simple method for the analysis of neutron resonance capture spectra  

NASA Astrophysics Data System (ADS)

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.; van Eijk, Carel W. E.

2009-03-01

132

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

133

Standardization Activities of the Euratom Neutron Radiography Working Group.  

National Technical Information Service (NTIS)

In 1979 a working group on neutron radiography was formed at Euratom. The purpose of this group is the standardization of neutron radiographic methods in the field of nuclear fuel. Activities of this Neutron Radiography Working Group are revised. Classifi...

J. Domanus

1982-01-01

134

Reconstruction of Time-Resolved Neutron Energy Spectra in Z-Pinch Experiments Using Time-of-flight Method  

SciTech Connect

We present the reconstruction of neutron energy spectra from time-of-flight signals. This technique is useful in experiments with the time of neutron production in the range of about tens or hundreds of nanoseconds. The neutron signals were obtained by a common hard X-ray and neutron fast plastic scintillation detectors. The reconstruction is based on the Monte Carlo method which has been improved by simultaneous usage of neutron detectors placed on two opposite sides from the neutron source. Although the reconstruction from detectors placed on two opposite sides is more difficult and a little bit inaccurate (it followed from several presumptions during the inclusion of both sides of detection), there are some advantages. The most important advantage is smaller influence of scattered neutrons on the reconstruction. Finally, we describe the estimation of the error of this reconstruction.

Rezac, K.; Klir, D.; Kubes, P.; Kravarik, J. [Department of Physics, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, 166 27, Prague 6 (Czech Republic)

2009-01-21

135

Investigation of combined unfolding of neutron spectra using the UMG unfolding codes.  

PubMed

An investigation of the simultaneous unfolding of data from neutron spectrometers using the UMG codes MAXED and GRAVEL has been performed. This approach involves combining the data from the spectrometers before unfolding, thereby performing a single combined unfolding of all the data to yield a final combined spectrum. The study used measured data from three proton recoil counters and also Bonner sphere and proton recoil counter responses calculated from their response functions. In each case, the spectrum derived from combined unfolding is compared with either the spectrum obtained from merging the independently unfolded spectra or the spectrum used to calculate the responses. The advantages and disadvantages of this technique are discussed. PMID:17502320

Roberts, N J

2007-05-14

136

Absorption features in the spectra of X-ray bursting neutron stars  

NASA Astrophysics Data System (ADS)

Context: The discovery of photospheric absorption lines in XMM-Newton spectra of the X-ray bursting neutron star in EXO 0748-676 by Cottam and collaborators allows us to constrain the neutron star mass-radius ratio from the measured gravitational redshift. A radius of R=9{-}12 km for a plausible mass range of M=1.4{-}1.8 M_? was derived by these authors. Aims: It has been claimed that the absorption features stem from gravitationally redshifted (z=0.35) n=2{-}3 lines of H- and He-like iron. We investigate this identification and search for alternatives. Methods: We compute LTE and non-LTE neutron-star model atmospheres and detailed synthetic spectra for a wide range of effective temperatures (T_eff = 1{-}20 MK) and different chemical compositions. Results: We are unable to confirm the identification of the absorption features in the X-ray spectrum of EXO 0748-676 as n=2{-}3 lines of H- and He-like iron (Fe XXVI and Fe XXV). These are subordinate lines that are predicted by our models to be too weak at any T_eff. It is more likely that the strongest feature is from the n=2{-}3 resonance transition in Fe XXIV with a redshift of z=0.24. Adopting this value yields a larger neutron star radius, namely R=12{-}15 km for the mass range M=1.4{-}1.8 M_?, favoring a stiff equation-of-state and excluding mass-radius relations based on exotic matter. Combined with an estimate of the stellar radius R > 12.5 km from the work of Özel and collaborators, the z=0.24 value provides a minimum neutron-star mass of M > 1.48 M_?, instead of M > 1.9 M_?, when assuming z=0.35. Conclusions: The current state of line identifications in the neutron star of EXO 0748-676 must be regarded as highly uncertain. Our model atmospheres show that lines other than those previously thought must be associated with the observed absorption features.

Rauch, T.; Suleimanov, V.; Werner, K.

2008-11-01

137

Miniature Neutron-Alpha Activation Spectrometer  

NASA Astrophysics Data System (ADS)

We are developing a miniature neutron-alpha activation spectrometer for in-situ analysis of chem-bio samples, including rocks, fines, ices, and drill cores, suitable for a lander or Rover platform for Mars or outer-planet missions. In the neutron-activation mode, penetrating analysis will be performed of the whole sample using a ? spectrometer and in the ?-activation mode, the sample surface will be analyzed using Rutherford-backscatter and x-ray spectrometers. Novel in our approach is the development of a switchable radioactive neutron source and a small high-resolution ? detector. The detectors and electronics will benefit from remote unattended operation capabilities resulting from our NEAR XGRS heritage and recent development of a Ge ? detector for MESSENGER. Much of the technology used in this instrument can be adapted to portable or unattended terrestrial applications for detection of explosives, chemical toxins, nuclear weapons, and contraband.

Rhodes, Edgar; Holloway, James Paul; He, Zhong; Goldsten, John

2002-10-01

138

Decreasing the fission track analysis detection limit of plutonium concentrations in human excreta by utilizing two distinct neutron energy spectra  

NASA Astrophysics Data System (ADS)

Environmental Pu239 arises from the development, production and testing of nuclear weapons. Fallout of this weapon debris has produced an average worldwide Pu239 level of about 1 ppb. Traditional methods are available to measure Pu239 at fCi levels, but these methods are unable to detect Pu239 at environmental levels (100 aCi). Such an ultra sensitive method chemically separates Pu239 from naturally occurring uranium and other fissile isotopes. Then the technique is applied to the Pu239 burden effluent. Fissile samples are exposed to distinct neutron spectra to achieve quantitative analysis of each fissile isotope using fission track analysis without chemical separation. The University of Utah's 100 kW TRIGA reactor was used to deliver thermal and epithermal neutron fluences. Each isotope has a unique fission cross-section for different neutron energy ranges. It was possible to differentiate between the isotopes based on the number of fission tracks produced. The proposed technique can measure the amount of Th232, U235, and Pu239 in the sample simultaneously. Samples containing known amounts of Pu239, natural uranium (U235 and U238) were deposited on the polycarbonate Lexan detectors and irradiated in different positions in the reactor core. They were chemically etched and fission tracks were counted. The concentrations were calculated using the computer code COG and the mathematical correlations for the two irradiators. NU=-2.754 0+/-0.25x1011 T1+1.9654+/-0.24 x1012T2 NPu=3.3 861+/-0.27x107 T1-1.4973+/-0.25 x108T2 aU,1= 6.2479+/-0.17x10-13 ,aU,2= 1.1304+/-0.23x10-13 aPu,1= 8.1976+/-0.16x10-11 ,aPu,2= 1.1492+/-0.23x10-11 T1 and T2 are the number of tracks counted from samples when exposed to a known neutron spectra. Without chemical processing, the detection limit of ˜120 aCi/g can easily be achieved. Calculated amounts ranged within a factor of two to three from a known quantity deposited on the Lexan detectors. The uncertainties associated with this method stem from the differences in theoretical and actual neutron flux in the irradiators, the inefficiencies with etching process, and errors with the track counting activity.

Choe, Dong-Ok

2000-10-01

139

Investigating Coincidence Techniques in Biomedical Applications of Neutron Activation Analysis  

NASA Astrophysics Data System (ADS)

While neutron activation analysis has been widely used in biomedical applications for some time, the use of non-radioactive tracer techniques, to monitor, for example, organ blood flow, is more recent. In these studies, pre-clinical animal models are injected with micro-spheres labeled with stable isotopes of elements that have a high neutron absorption cross-section. Subsequently, samples of blood and/or tissue from different locations in the body are subjected to neutron activation analysis to measure the propagation of the labeled micro-spheres through the body. Following irradiation, the counting (with high-resolution Ge detectors) is typically delayed by a few days to dissipate short-lived activity in the samples and improve signal-to-noise for the peaks of interest in the activation spectrum. The aim of the present study was to investigate whether coincidence techniques (for isotopes which decay via two-photon cascades) could improve signal-to-noise and turn-around times. The samples were irradiated at the 1 MW research reactor at the UMass Lowell Radiation Laboratory. The analysis of the multi-parameter coincidence data recorded in event-mode will be presented and compared with the standard method of recording singles spectra.

Chowdhury, P.; Gramer, R.; Tandel, S. K.; Reinhardt, C. J.

2004-05-01

140

Phantom studies of Cd, Hg and Cl by prompt gamma neutron activation analysis using a 238Pu Be neutron source  

NASA Astrophysics Data System (ADS)

Prompt gamma neutron activation analysis is a means of non-invasive monitoring for occupational exposure to toxic heavy metals such as Cd and Hg. Preliminary kidney detection limits from previous phantom studies at McMaster were 13.6 ± 0.2 ppm for Cd (125 mL phantom) and 315 ± 24 ppm for Hg (125 mL phantom) using the 238Pu Be neutron source and 0.88 ± 0.01 ppm for Cd (125 mL phantom) and 16.91 ± 0.05 ppm for Hg (30 mL phantom) using the thermal neutron beam port at the McMaster Nuclear Reactor. The detection limits vary greatly between the two methods due to differences in experimental set-up, neutron energy spectra and a difference in dose by more than a factor of 100. The Hg detection limit from preliminary data is much higher than expected for both neutron source types. In order to explain the apparent detection limit discrepancy, measurements of Hg and Cd phantoms were performed using the 238Pu Be neutron source. The results were compared to phantom measurements of Cl, a well-known neutron activation element.

Grinyer, J.; Atanackovic, J.; Byun, S. H.; Chettle, D. R.

2007-10-01

141

Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons  

SciTech Connect

With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, we discuss recent advances in a unified macroscopic-microscopic description of large-amplitude collective nuclear dynamics. The conversion of collective energy into single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving the Hamilton equations of motion for initial conditions appropriate to fission, we obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of our calculations with experimental data are shown.

Nix, J.R.; Madland, D.G.; Sierk, A.J.

1985-01-01

142

Study of Neutron Spectra in the BFS-28, BFS-30, BFS-33 Fast Critical Assemblies Using CINI and FEI Spectrometers with Proportional Counters of Recoil Protons.  

National Technical Information Service (NTIS)

Results are given of developing a hydrogen-counter neutron spectrometer alongside with experiences in using hydrogen counters for measuring neutron spectra in fast critical BPhS assemblies. A brief account is presented of spectrometer characteristics, met...

E. N. Kuzin S. P. Belov V. G. Dvukhsherstnov Y. A. Kazanskii N. N. Shchadin

1976-01-01

143

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

144

Active and sterile neutrino mass effects on beta decay spectra  

NASA Astrophysics Data System (ADS)

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 (3H, 187Re, 107Pd, 163Ho, etc) using different masses of both active and sterile neutrinos and different values of the mixing parameter.

Boillos, Juan Manuel; Moreno, Óscar; de Guerra, Elvira Moya

2013-06-01

145

Cadmium by in vivo neutron activation analysis  

Microsoft Academic Search

\\u000a Résumé  On peut déterminer la présence de cadmium chez l'homme à l'aide de technique de l'analyse par activation neutronique in vivo.\\u000a La capture des neutrons thermiques par113Cd conduit à une émission ? prompt qui peut être détectée au moyen d'un semi-conducteur convenable. On a réalisé une installation\\u000a à l'Université de Birmingham pour produire au moyen d'un cyclotron un faisceau de neutrons

H. C. Biggin; N. S. Chen; K. V. Ettinger; J. H. Fremlin; W. D. Morgan; R. Nowotny; M. J. Chamberlain; T. C. Harvey

1974-01-01

146

Analysis of medicinal plant extracts by neutron activation method.  

National Technical Information Service (NTIS)

This dissertation has presented the results from analysis of medicinal plant extracts using neutron activation method. Instrumental neutron activation analysis was applied to the determination of the elements Al, Br, Ca, Ce, Cl, Cr, Cs, Fe, K, La, Mg, Mn,...

S. M. Vaz

1995-01-01

147

Isolation of Pseudomonas aeruginosa specific phages with broad activity spectra.  

PubMed

The aim of the study was to screen various kinds of samples for Pseudomonas aeruginosa specific phages and to isolate and partially characterize those with broad activity spectra. The Pseudomonas specific phages were isolated using an enrichment procedure with single strains or the cocktail of P. aeruginosa strains as hosts. Using the described procedure, phages were successfully isolated only from water samples, while in soil and feces no Pseudomonas specific phages were detected. The lytic spectra of isolated phages were determined by spot method on lawns of 33 P. aeruginosa strains and five species belonging to family Enterobacteriaceae. The results showed that among isolated phages, 001A, delta, and I possessed the broad activity spectra, as were able to plaque on more than 50% of tested P. aeruginosa strains, while none of the phages were able to lyse the other tested species. Significant differences in phage activity spectra were not observed when P. aeruginosa cocktail was applied for sample enrichment. The most of the phages examined by electron microscopy belonged to family Siphoviridae, while the broad activity spectra isolates, except for 001A, possessed morphological characteristics of family Podoviridae. Digested DNA of the phages delta and I showed similar patterns, indicating the prevalence and success of this phage type in the environment. PMID:19472004

Knezevic, Petar; Kostanjsek, Rok; Obreht, Dragana; Petrovic, Olga

2009-05-27

148

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

Microsoft Academic Search

Damage energy cross sections to 20 MeV are given for aluminum, vanadium, chromium, iron, nickel, copper, zirconium, niobium, molybdenum, tantalum, tungsten, lead, and 18Cr10Ni stainless steel. They are based on ENDF\\/B-IV nuclear data and the Lindhard energy partition model. Primary knockon atom (PKA) spectra are given for aluminum, iron, niobium, tantalum, and lead for neutron energies up to 15 MeV

D. G. Doran; N. J. Graves

1976-01-01

149

Determination of aluminium in a "nimonic" alloy by activation with fast neutrons.  

PubMed

Aluminium at the 6% level was determined in a 15-component "nimonic" alloy with a coefficient of variation of +/-8.7% by using fast-neutron activation followed by pulse-height analysis of gamma-ray spectra. The possibility of determining chromium, iron, cobalt and manganese is discussed. PMID:18960521

Quigley, D A; Trussler, J W

1969-03-01

150

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

151

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

152

High Resolution X-ray Spectra and Timing of Four Neutron Stars  

NASA Astrophysics Data System (ADS)

The Low and High Energy Transmission Grating Spectrometers on the Chandra Xray Observatory were used to obtain high spectral resolution for four isolated neutron stars: PSR B0656+14 (1), RX J0720.4-3125 (2), 4U 0142+61 (3) and RX J1856.53754 (4). No spectral line or edge absorption features were found in the spectra of these sources, arguing against metal-dominated atmosphere models. For the three pulsars, even phase-resolved spectra showed no significant features. The lack of a proton cyclotron line in the spectrum of 4U 0142+61 yields strong limits on the average surface field strength of between 2e14 and 1e15 G, consistent with field values estimated from spindown. The RX J1856.5-3754 data contain no evidence for pulsation, so we place a 99% confidence upper limit of 2.7% on the unaccelerated pulse fraction over a wide frequency range from 0.0001 to 100 Hz. The distance to RX J1856.5-3754 is known well enough that the apparent black body radius is too small for current neutron star models, indicating that the object may be more compact, as allowed for strange quark matter equations of state. This work has been supported in part by NASA contract NAS8-39073 to the Chandra X-ray Center. References: (1) Marshall, H.L. and Schulz, N.S. 2002, Ap.J., in press. (2) Kaplan, D.L., Marshall, H.L., Kulkarni, S.R., and van Kerkwijk, M.H. 2002, in prep. (3) Juett, A.M., Marshall, H.L., Chakrabarty, D. and Schulz, N.S. 2002, Ap. J. Letters, 568, L31. (4) Drake, J.J., Marshall, H.L., et al. 2002, Ap.J., in press.

Marshall, H.

153

Molecular-dynamics study of incoherent quasielastic neutron-scattering spectra of supercooled water  

SciTech Connect

A molecular-dynamics simulation of extended simple point charge water in a time interval of 1 fs to 50 ns has been performed to study the single-particle dynamics of water at supercooled temperatures. In spite of the fact that upon supercooling water progressively evolves into a more open structure locally, the single-particle dynamics is nevertheless shown to be dominated by the so-called cage effect experienced by the test particle. The slow structural relaxation of the cage at low temperatures leads to the phenomenon of slow dynamics that can only be completely studied by following the trajectories into the nanosecond range. The objective of this paper is twofold. First, we test the accuracy of various approximations used in previous analyses of spectra from incoherent quasielastic neutron-scattering experiments. Second, we explore the possibility of an alternative method of analysis of high-resolution quasielastic neutron-scattering spectra, taking into account the slow dynamics in supercooled water. The approximations tested are the decoupling of the self-intermediate scattering function into a product of rotational and translational components, the physical interpretation of the origin of the experimentally observed Debye-Waller factor, the rotational-diffusion approximation of the rotational intermediate scattering function, and the random jump diffusion approximation of the translational intermediate scattering function. Various approximations used previously for the component intermediate scattering functions are not sufficiently accurate. The reason for this is that at supercooled temperatures, due to the dominant cage effect, the conventional picture of the stochastic single-particle diffusion loses its validity. The diffusion process is then progressively controlled by the structural relaxation of the cage. {copyright} {ital 1997} {ital The American Physical Society}

Chen, S.; Gallo, P. [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Sciortino, F.; Tartaglia, P. [Dipartimento di Fisica and Istituto Nazionale per la Fisica della Materia, Universita di Roma La Sapienza, Piazzale Aldo Moro 2, I-00185 Roma (Italy)

1997-10-01

154

SOURCES-3A: A code for calculating ({alpha}, n), spontaneous fission, and delayed neutron sources and spectra  

SciTech Connect

In many systems, it is imperative to have accurate knowledge of all significant sources of neutrons due to the decay of radionuclides. These sources can include neutrons resulting from the spontaneous fission of actinides, the interaction of actinide decay {alpha}-particles in ({alpha},n) reactions with low- or medium-Z nuclides, and/or delayed neutrons from the fission products of actinides. Numerous systems exist in which these neutron sources could be important. These include, but are not limited to, clean and spent nuclear fuel (UO{sub 2}, ThO{sub 2}, MOX, etc.), enrichment plant operations (UF{sub 6}, PuF{sub 4}, etc.), waste tank studies, waste products in borosilicate glass or glass-ceramic mixtures, and weapons-grade plutonium in storage containers. SOURCES-3A 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 in homogeneous media (i.e., a mixture of {alpha}-emitting source material and low-Z target material) and in interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material). The code is also capable of calculating the neutron production rates due to ({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.

Perry, R.T.; Wilson, W.B.; Charlton, W.S.

1998-04-01

155

Large-sample neutron activation analysis: Present status and prospects  

Microsoft Academic Search

Neutron activation analysis is attractive for trace-element determinations in large samples. Facilities for reactor irradiation and -ray spectrometry of kilogram-size cylindrical samples are described. The thermal neutron flux is ca. 5·1012m–2·s–1 with a\\u000ath\\/\\u000aepi>104, so neutron self-thermalization can be neglected. The correction for the neutron attenuation within the sample is derived from measurement of the neutron flux depression just

P. Bode; R. M. W. Overwater; J. J. M. De Goeij

1997-01-01

156

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

157

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

158

Inter-pulse high-resolution gamma-ray spectra using a 14 MeV pulsed neutron generator  

USGS Publications Warehouse

A neutron generator pulsed at 100 s-1 was suspended in an artificial borehole containing a 7.7 metric ton mixture of sand, aragonite, magnetite, sulfur, and salt. Two Ge(HP) gamma-ray detectors were used: one in a borehole sonde, and one at the outside wall of the sample tank opposite the neutron generator target. Gamma-ray spectra were collected by the outside detector during each of 10 discrete time windows during the 10 ms period following the onset of gamma-ray build-up after each neutron burst. The sample was measured first when dry and then when saturated with water. In the dry sample, gamma rays due to inelastic neutron scattering, neutron capture, and decay were counted during the first (150 ??s) time window. Subsequently only capture and decay gamma rays were observed. In the wet sample, only neutron capture and decay gamma rays were observed. Neutron capture gamma rays dominated the spectrum during the period from 150 to 400 ??s after the neutron burst in both samples, but decreased with time much more rapidly in the wet sample. A signal-to-noise-ratio (S/N) analysis indicates that optimum conditions for neutron capture analysis occurred in the 350-800 ??s window. A poor S/N in the first 100-150 ??s is due to a large background continuum during the first time interval. Time gating can be used to enhance gamma-ray spectra, depending on the nuclides in the target material and the reactions needed to produce them, and should improve the sensitivity of in situ well logging. ?? 1984.

Evans, L. G.; Trombka, J. I.; Jensen, D. H.; Stephenson, W. A.; Hoover, R. A.; Mikesell, J. L.; Tanner, A. B.; Senftle, F. E.

1984-01-01

159

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

2009-11-07

160

Improvement of Methods Used for Reconstruction of Time Resolved Neutron Energy Spectra in D-D Fusion Reactions  

NASA Astrophysics Data System (ADS)

Several methods (Monte Carlo, maximum entropy, genetic algorithm, etc.) for the reconstruction of the time resolved neutron energy spectra have been developed in the last few decades. The energy spectra are reconstructed from time-resolved neutron signals which are recorded by several detectors in one direction at different distances. The basic formulation of the problem as well as test results indicate that the methods could give better results when detectors in the opposite direction are also included. If we want to employ both directions of neutron detection, we must know the relation between the neutrons which are emitted in one direction and the opposite direction. Considering these facts, one of the methods (namely the Monte Carlo reconstruction method) was improved. Our improvement includes the anisotropy in neutron yields and neutron energies. The transformation is based on the scattering theory and it is applied specifically to the D-D fusion reaction. This improved Monte Carlo method has been used to process data from experiments on the PF 1000 plasma focus (IPPLM, Warsaw) and on the S-300 Z-pinch (Kurchatov Institute, Moscow).

Rezac, K.; Klir, D.; Kubes, P.; Kravarik, J.

2006-10-01

161

Neutron coincidence imaging for active and passive neutron assays  

Microsoft Academic Search

Neutron multiplicity assay algorithms for ²°Pu assume a point source of fission neutrons that are detected in a single detector channel. The ²°Pu in real waste, however, is more likely to be distributed throughout the container in some random way. For different reasons, this leads to significant errors when using either multiplicity or simpler coincidence analyses. Reduction of these errors

R. J. Estep; G. S. Brunson; S. G. Melton

2001-01-01

162

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

163

Signatures of Photon-Axion Conversion in the Thermal Spectra and Polarization of Neutron Stars  

NASA Astrophysics Data System (ADS)

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; Ho, Wynn C. G.; Verde, Licia; van Adelsberg, Matthew; Jimenez, Raul

2012-04-01

164

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

165

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

166

Evaluation and use of the prompt fission neutron spectrum and spectra covariance matrices in criticality and shielding  

NASA Astrophysics Data System (ADS)

The prompt fission neutron spectra covariance matrices of 235U, 238U and 239Pu were evaluated using the Monte Carlo method for two empirical spectra formulations, Watt and Kornilov, and compared to the existing evaluations such as JENDL-3.3. The fission spectra, together with the covariance matrices and the methods for the calculation of the corresponding sensitivity profiles were validated on several applications, including shielding (VENUS-3 benchmark, pressure vessel dosimetry) as well as on fast and thermal reactor systems (KRITZ and SNEAK critical experiments). A new set of parameters for a Kornilov model is proposed that improve both benchmark performance and the agreement with recently measured differential spectra. A recommendation to use constrained sensitivity coefficients was confirmed for the case of the fission spectrum induced uncertainty in the effective multiplication factor (keff) and in the detector responses, in order to assure the proper normalisation of the corresponding covariance matrices.

Kodeli, Ivan; Trkov, Andrej; Capote, Roberto; Nagaya, Yasunobu; Maslov, Vladimir

2009-11-01

167

Hydration Effect on Low-Frequency Protein Dynamics Observed in Simulated Neutron Scattering Spectra  

PubMed Central

Hydration effects on protein dynamics were investigated by comparing the frequency dependence of the calculated neutron scattering spectra between full and minimal hydration states at temperatures between 100 and 300 K. The protein boson peak is observed in the frequency range 1–4 meV at 100 K in both states. The peak frequency in the minimal hydration state shifts to lower than that in the full hydration state. Protein motions with a frequency higher than 4 meV were shown to undergo almost harmonic motion in both states at all temperatures simulated, whereas those with a frequency lower than 1 meV dominate the total fluctuations above 220 K and contribute to the origin of the glass-like transition. At 300 K, the boson peak becomes buried in the quasielastic contributions in the full hydration state but is still observed in the minimal hydration state. The boson peak is observed when protein dynamics are trapped within a local minimum of its energy surface. Protein motions, which contribute to the boson peak, are distributed throughout the whole protein. The fine structure of the dynamics structure factor is expected to be detected by the experiment if a high resolution instrument (

Joti, Yasumasa; Nakagawa, Hiroshi; Kataoka, Mikio; Kitao, Akio

2008-01-01

168

Thermal Neutron Imaging in an Active Interrogation Environment  

Microsoft Academic Search

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

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

2009-01-01

169

Thermal neutron imaging in an active interrogation environment  

Microsoft Academic Search

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 xcitation by high energy photons. The photo-induced neutrons can be

P. E. Vanier; L. Forman; D. R. Norman

2009-01-01

170

DS02 fluence spectra for neutrons and gamma rays at Hiroshima and Nagasaki with fluence-to-kerma coefficients and transmission factors for sample measurements  

Microsoft Academic Search

Fluence spectra at several ground distances in Hiroshima and Nagasaki are provided along with associated fluence-to-kerma\\u000a coefficients from the Dosimetry System 2002 (DS02). Also included are transmission factors for calculating expected responses\\u000a of in situ sample measurements of neutron activation products such as 32P,36Cl,39Ar,41Ca, 60Co,63Ni,152Eu,  and 154Eu. The free-in-air (FIA) fluences calculated in 2002 are available for 240 angles, 69 energy

Stephen D. Egbert; George D. Kerr; Harry M. Cullings

2007-01-01

171

Measurements of fusion neutron energy spectra at JET by means of time-of-flight techniques  

Microsoft Academic Search

High fluxes of neutrons are emitted from the JET tokamak when deuterium plasmas are raised to high temperatures with neutral beam injection and ion cyclotron resonance heating. The energy distribution of these neutrons carries valuable information concerning the velocity distributions of the reacting ions. A double scattering time-of-flight spectrometer is used for measuring the neutron energy distribution. This spectrometer provides

T. Elevant; P. van Belle; O. N. Jarvis; G. Sadler

1995-01-01

172

Accounting for the thermal neutron flux depression in voluminous samples for instrumental neutron activation analysis  

SciTech Connect

At the Delft University of Technology Interfaculty Reactor Institute, a facility has been installed to irradiate cylindrical samples with diameters up to 15 cm and weights up to 50 kg for instrumental neutron activation analysis (INAA) purposes. To be able to do quantitative INAA on voluminous samples, it is necessary to correct for gamma-ray absorption, gamma-ray scattering, neutron absorption, and neutron scattering in the sample. The neutron absorption and the neutron scattering are discussed. An analytical solution is obtained for the diffusion equation in the geometry of the irradiation facility. For samples with known composition, the neutron flux--as a function of position in the sample--can be calculated directly. Those of unknown composition require additional flux measurements on which least-squares fitting must be done to obtain both the thermal neutron diffusion coefficient D[sub s] and the diffusion length L[sub s] of the sample. Experiments are performed to test the theory.

Overwater, R.M.W.; Hoogenboom, J.E. (Delft Univ. of Technology (Netherlands). Interfaculty Reactor Inst.)

1994-07-01

173

Neutron activation cross sections on lead isotopes  

NASA Astrophysics Data System (ADS)

The cross sections for the reactions Pb204(n,n'?)Pb204m, Pb204(n,2n)Pb203, Pb204(n,2n)Pb203m1, Pb204(n,3n)Pb202m, Pb206(n,3n)Pb204m, Pb206(n,?)Hg203, and Pb208(n,p)Tl208 were determined at the IRMM van de Graaff laboratory in the neutron energy range from 14 to 21 MeV. Both natural and enriched samples were irradiated with neutrons produced via the H3(d,n)He4 reaction. The induced activities were determined by gamma-ray spectrometry using a HPGe detector in a low-background shield. Neutron fluences were determined with the well-known cross section of the Al27(n,?)Na24 reaction. Enriched samples were essential to determine the cross sections for the reactions with Pb204m and Pb206m isomers in the final state. Accurate results for reactions with Pb204,206 as target nuclei with natural lead samples were enabled through a precise measurement of the isotopic ratios. For a first investigation of the consequences of the present data for nuclear reaction models they were confronted with calculations based on global parameter systematics in a phenomenological and in a microscopic approach and with parameters selected to reproduce the available data. The TALYS code was used for the former two calculations involving parameter systematics while the STAPRE code was used for the latter calculation.

Semkova, V.; Reimer, P.; Altzitzoglou, T.; Plompen, A. J. M.; Quétel, C.; Sudár, S.; Vogl, J.; Koning, A. J.; Qaim, S. M.; Smith, D. L.

2009-08-01

174

Nondestructive testing: Neutron radiography and neutron activation. (Latest citations from the INSPEC database). Published Search  

SciTech Connect

The bibliography contains citations concerning the technology of neutron radiography and neutron activation for nondestructive testing of materials. The development and evaluation of neutron activation analysis and neutron diffraction examination of liquids and solids are presented. Citations also discuss nondestructive assay, verification, evaluation, and multielement analysis of biomedical, environmental, industrial, and geological materials. Nondestructive identification of chemical agents, explosives, weapons, and drugs in sealed containers are explored. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

NONE

1996-04-01

175

An investigation of the activation of water by DT fusion neutrons and some implications for fusion reactor technology  

Microsoft Academic Search

Several fundamental aspects of the activation of water by neutrons in D-T fusion systems have been investigated in this work. The basic physical principles involved and the status of pertinent nuclear cross-section and radioactivity data were reviewed. The integral response of the dominant 16O(n,p)16N reaction was calculated using several evaluated differential cross-section representations and characteristic D-T fusion neutron spectra. The

Yujiro Ikeda; Yoshitomo Uno; Fujio Maekawa; Donald L. Smith; Itacil C. Gomes; Robert C. Ward; Anatoly A. Filatenkov

1997-01-01

176

Correction for neutron self-shielding in large-sample prompt-gamma neutron activation analysis  

Microsoft Academic Search

When a sample is analysed with neutron activation analysis (NAA) neutron self-shielding and gamma self-absorption affect the accuracy. Both effects become even more important when the mass of a sample analysed is changed from small (say, 1 g) to large (say 30 kg). Therefore, corrections have to be carried out. In this article only the correction method for neutron self-shielding

I. H. Degenaar; M. Blaauw; J. J. M. de Goeij

2003-01-01

177

Gamma-ray spectroscopy and neutron activation analysis using GAMANAL-PC and QUACANAL  

Microsoft Academic Search

Two MS-DOS based programs, GAMANAL-PC and QUACANAL have been developed in order to process data from neutron activation analysis (NAA). GAMANAL-PC is a Gaussian peak fitting program that analyses gamma-ray spectra and writes ASCII data files that are read by the QUACANAL program in order calculate elemental concentrations. The modular nature of the programs allows the nuclear analyst the ability

P. A. Beeley

1995-01-01

178

Compton suppression neutron activation methods in environmental analysis  

Microsoft Academic Search

An overview of Compton suppression neutron activation analysis (NAA) is given. The basic theory of the technique, its experimental design, uniqueness, and limitations are discussed. Experimental data showing its usefulness for the low level determination of several key elements in environmental samples that can not be obtained using conventional non-destructive neutron activation is deliberated.

S. Landsberger

1994-01-01

179

In vivo neutron activation facility at Brookhaven National Laboratory.  

National Technical Information Service (NTIS)

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 p...

R. Ma S. Yasumura F. A. Dilmanian

1997-01-01

180

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

181

Coal ash parameters by neutron activation  

NASA Astrophysics Data System (ADS)

The coal parameters, ash content and ash slagging index, may be strongly related to the chemical composition of mineral impurities in coal. Based on this assumption the authors have examined the feasibility of neutron activation techniques, both as a laboratory and a well logging method, by recording induced ?-rays in the two energy intervals with the help of a scintillation ?-ray spectrometer. Results from the Upper Silesiab Coal Basin have shown that the method can be used to evaluate the ash content and ash fusion temperature, both in the laboratory and in well logging: the corresponding mean standard deviations being 1.5 wt% and 35°C; and 3 wt% and 45°C, respectively.

Chru?ciel, Edward; Chau, Nguyen Dinh; Niewodnicza?ski, Jerzy W.

1994-12-01

182

Measurements and evaluations of neutron dose and spectra at the reactor top of the liquid-metal fast breeder type reactor, JOYO  

Microsoft Academic Search

To investigate the neutron dose and spectra around a fast reactor from the point of view of radiation protection and shielding, neutron measurements were conducted at the reactor top of JOYO, a Japanese experimental fast reactor, and an analysis by a transport calculation was performed. The measurements were carried out under a Mark II irradiation core with and without the

T. Kosako; J. Matsumoto; A. Sekiguchi; N. Ohtani; S. Suzuki; S. Takeda; O. Sato

1987-01-01

183

Determination of helium and hydrogen yield from measurements on pure metals and alloys irradiated by mixed high energy proton and spallation neutron spectra in LANSCE  

Microsoft Academic Search

The confident design of accelerator-driven spallation neutron devices will require good estimates of the cross-sections for generation of helium and hydrogen in the mixed spectra of high energy protons and neutrons that will be experienced by the structural materials. Improved estimates of these cross-sections were derived from a series of irradiations that were conducted at relatively low temperatures (

F. A Garner; B. M Oliver; L. R Greenwood; M. R James; P. D Ferguson; S. A Maloy; W. F Sommer

2001-01-01

184

Vibrational spectra, structure and antioxidant activity of gossypol imine derivatives  

NASA Astrophysics Data System (ADS)

The structures and tautomeric equilibria of natural polyphenol gossypol and four its imine derivatives were studied by FT-IR-, NMR-spectroscopy and quantum chemistry methods. It was shown that gossypol Schiff bases exist in solution as enamine-enamine tautomer and hydrazones as imine-imine tautomer. Infrared absorption spectra of studied compounds were simulated using the PM3 method. The fundamental vibrational frequencies were evaluated using various scale factors which yield a good agreement between observed and calculated frequencies. Free radical scavenging activity of gossypol and its imine derivatives was evaluated using DPPH method. Antioxidant activity of studied compounds was characterized. Gossypol hydrazones were shown to be more efficient, while Schiff base to be less efficient as antioxidants in comparison with gossypol itself.

Ilkevych, N. S.; Schroeder, G.; Rybachenko, V. I.; Chotiy, K. Y.; Makarova, R. A.

2012-02-01

185

Evaluation of New Pharmaceuticals Using In Vivo Neutron Inelastic Scattering and Neutron Activation Analysis  

Microsoft Academic Search

Nutritional status of patients can be evaluated by monitoring changes in body composition, including depletion of protein and muscle, adipose tissue distribution and changes in hydration status, bone or cell mass. Fast neutron activation (for N and P) and neutron inelastic scattering (for C and O) are used to assess in vivo elements characteristic of specific body compartments. The fast

J. J. Kehayias

2000-01-01

186

Explicit versus implicit solvent modeling of Raman optical activity spectra.  

PubMed

Raman and Raman optical activity (ROA) spectra of molecules reflect not only molecular structure and conformation but also the dynamics and interactions with the solvent. For polar, biologically relevant molecules in aqueous environment, this often complicates the band assignment and interpretation of the spectra. In the present study, implicit dielectric and explicit solvent models are compared with respect to the influence of the choice of solvent model on the spectral shape. Lactamide and 2-aminopropanol were selected as model compounds, and the Raman and ROA spectra were measured for both enantiomers. Geometries of explicitly solvated clusters were derived from quantum-mechanical calculations, classical (MD), and Car-Parrinello (CPMD) molecular dynamics. The results indicate that although the dielectric model reasonably well reproduces the main spectral features, more faithful intensity profiles, including the inhomogeneous band broadening, are obtained from the explicit MD and CPMD clusters. Additionally, the CPMD clusters are capable of reproducing most spectral features better than the classical dynamics, provided the simulation time is long enough to allow for a complete sampling of the conformational space. The hydrogen-bonded water molecules of the first hydration shell significantly influence the spectral intensities, whereas the effect of loosely attached or distant solvent molecules is minor. In order to average the signal, however, a relatively large number of MD geometries need to be considered, as was also exemplified by simulations of the ROA spectrum of the achiral molecule glycine. An explicit solvent modeling of sizable systems thus requires extensive computations, which became possible only recently due to the development of efficient analytical computational techniques. PMID:21417248

Hopmann, Kathrin H; Ruud, Kenneth; Pecul, Magdalena; Kudelski, Andrzej; Dra?ínský, Martin; Bou?, Petr

2011-03-21

187

Prompt fission neutron spectra from fission induced by 1 to 8 MeV neutrons on U235 and Pu239 using the double time-of-flight technique  

NASA Astrophysics Data System (ADS)

Prompt fission neutron spectra from U235 and Pu239 were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg U235 and 90 mg Pu239 detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced ?-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.

Noda, S.; Haight, R. C.; Nelson, R. O.; Devlin, M.; O'Donnell, J. M.; Chatillon, A.; Granier, T.; Bélier, G.; Taieb, J.; Kawano, T.; Talou, P.

2011-03-01

188

Neutron activation diagnostics at the National Ignition Facility (invited).  

PubMed

Neutron yields are measured at the National Ignition Facility (NIF) by an extensive suite of neutron activation diagnostics. Neutrons interact with materials whose reaction cross sections threshold just below the fusion neutron production energy, providing an accurate measure of primary unscattered neutrons without contribution from lower-energy scattered neutrons. Indium samples are mounted on diagnostic instrument manipulators in the NIF target chamber, 25-50 cm from the source, to measure 2.45 MeV deuterium-deuterium fusion neutrons through the (115)In(n,n')(115 m) In reaction. Outside the chamber, zirconium and copper are used to measure 14 MeV deuterium-tritium fusion neutrons via (90)Zr(n,2n), (63)Cu(n,2n), and (65)Cu(n,2n) reactions. An array of 16 zirconium samples are located on port covers around the chamber to measure relative yield anisotropies, providing a global map of fuel areal density variation. Neutron yields are routinely measured with activation to an accuracy of 7% and are in excellent agreement both with each other and with neutron time-of-flight and magnetic recoil spectrometer measurements. Relative areal density anisotropies can be measured to a precision of less than 3%. These measurements reveal apparent bulk fuel velocities as high as 200 km/s in addition to large areal density variations between the pole and equator of the compressed fuel. PMID:23126840

Bleuel, D L; Yeamans, C B; Bernstein, L A; Bionta, R M; Caggiano, J A; Casey, D T; Cooper, G W; Drury, O B; Frenje, J A; Hagmann, C A; Hatarik, R; Knauer, J P; Johnson, M Gatu; Knittel, K M; Leeper, R J; McNaney, J M; Moran, M; Ruiz, C L; Schneider, D H G

2012-10-01

189

Neutron activation diagnostics at the National Ignition Facility (invited)  

NASA Astrophysics Data System (ADS)

Neutron yields are measured at the National Ignition Facility (NIF) by an extensive suite of neutron activation diagnostics. Neutrons interact with materials whose reaction cross sections threshold just below the fusion neutron production energy, providing an accurate measure of primary unscattered neutrons without contribution from lower-energy scattered neutrons. Indium samples are mounted on diagnostic instrument manipulators in the NIF target chamber, 25-50 cm from the source, to measure 2.45 MeV deuterium-deuterium fusion neutrons through the 115In(n,n')115m In reaction. Outside the chamber, zirconium and copper are used to measure 14 MeV deuterium-tritium fusion neutrons via 90Zr(n,2n), 63Cu(n,2n), and 65Cu(n,2n) reactions. An array of 16 zirconium samples are located on port covers around the chamber to measure relative yield anisotropies, providing a global map of fuel areal density variation. Neutron yields are routinely measured with activation to an accuracy of 7% and are in excellent agreement both with each other and with neutron time-of-flight and magnetic recoil spectrometer measurements. Relative areal density anisotropies can be measured to a precision of less than 3%. These measurements reveal apparent bulk fuel velocities as high as 200 km/s in addition to large areal density variations between the pole and equator of the compressed fuel.

Bleuel, D. L.; Yeamans, C. B.; Bernstein, L. A.; Bionta, R. M.; Caggiano, J. A.; Casey, D. T.; Cooper, G. W.; Drury, O. B.; Frenje, J. A.; Hagmann, C. A.; Hatarik, R.; Knauer, J. P.; Johnson, M. Gatu; Knittel, K. M.; Leeper, R. J.; McNaney, J. M.; Moran, M.; Ruiz, C. L.; Schneider, D. H. G.

2012-10-01

190

Neutron activation diagnostics at the National Ignition Facility (invited)  

SciTech Connect

Neutron yields are measured at the National Ignition Facility (NIF) by an extensive suite of neutron activation diagnostics. Neutrons interact with materials whose reaction cross sections threshold just below the fusion neutron production energy, providing an accurate measure of primary unscattered neutrons without contribution from lower-energy scattered neutrons. Indium samples are mounted on diagnostic instrument manipulators in the NIF target chamber, 25-50 cm from the source, to measure 2.45 MeV deuterium-deuterium fusion neutrons through the {sup 115}In(n,n'){sup 115m} In reaction. Outside the chamber, zirconium and copper are used to measure 14 MeV deuterium-tritium fusion neutrons via {sup 90}Zr(n,2n), {sup 63}Cu(n,2n), and {sup 65}Cu(n,2n) reactions. An array of 16 zirconium samples are located on port covers around the chamber to measure relative yield anisotropies, providing a global map of fuel areal density variation. Neutron yields are routinely measured with activation to an accuracy of 7% and are in excellent agreement both with each other and with neutron time-of-flight and magnetic recoil spectrometer measurements. Relative areal density anisotropies can be measured to a precision of less than 3%. These measurements reveal apparent bulk fuel velocities as high as 200 km/s in addition to large areal density variations between the pole and equator of the compressed fuel.

Bleuel, D. L.; Yeamans, C. B.; Bernstein, L. A.; Bionta, R. M.; Caggiano, J. A.; Drury, O. B.; Hagmann, C. A.; Hatarik, R.; Knittel, K. M.; McNaney, J. M.; Moran, M.; Schneider, D. H. G. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Casey, D. T.; Frenje, J. A.; Johnson, M. Gatu [Massachusetts Institute of Technology Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Cooper, G. W. [University of New Mexico, Albuquerque, New Mexico 87131 (United States); Knauer, J. P. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Leeper, R. J.; Ruiz, C. L. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)

2012-10-15

191

Reactor-Neutron Monitoring with Multiple Activation Detectors.  

National Technical Information Service (NTIS)

A method of the reactor-neutron monitoring for irradiation experiments and radioisotope production has been studied by means of multiple activation detectors. For the convenience in routine works, wires of metal and alloy were used as the activation detec...

H. Matsuoka T. Sekine

1981-01-01

192

Measurement of thermal neutron cross section and resonance integral for 165Ho(n, ?) 166 g Ho reaction by the activation method  

Microsoft Academic Search

The thermal neutron cross section and the resonance integral of the reaction 165Ho(n,?)166gHo were measured by the activation method using 55Mn(n,?)56Mn monitor reaction. The sufficiently diluted MnO2 and Ho2O3 samples with and without a cylindrical Cd case were irradiated in an isotropic neutron field of the 241Am–Be neutron sources. The ?-ray spectra from the irradiated samples were measured with a

Haluk Yücel; Mustafa Karadag

2005-01-01

193

Measurement of thermal neutron cross-section and resonance integral for 186W( n,?) 187W reaction by the activation method using a single monitor  

Microsoft Academic Search

The thermal neutron cross-section (?0) and the resonance integral (I0) of the reaction 186W(n,?)187W were measured by the activation method using 55Mn as a single comparator. The diluted MnO2 and WO3 samples within and without a cylindrical Cd shield case were irradiated in an isotropic neutron field of the 241Am–Be neutron source. The ?-ray spectra from the irradiated samples were

Mustafa Karadag; Haluk Yücel

2004-01-01

194

Calculation of Dose Equivalent Index, Effective Dose Equivalent and Ambient Dose Equivalent for the Giant Resonance Neutron Spectra Produced at an Electron Accelerator.  

National Technical Information Service (NTIS)

The ANISN code has been used in this study to evaluate the attenuation of neutron beams of various spectra incident normally on slabs of different kinds of concrete. Spectra of the most common sources (Am-Be and Cf-252) and those of giant resonance neutro...

M. Pelliccioni A. Zanini

1988-01-01

195

Measurements of Neutron Yield from Deuterium Plasmas at JET by Activation Techniques  

SciTech Connect

The paper reports on experiments carried out at JET to test the possibility of using some activating materials (e.g. {sup 89}Y, {sup 167}Er, {sup 204}Pb, {sup 180}Hf, {sup 111}Cd, etc.) to perform multi-foil neutron activation measurements. It is shown that apart from indium other materials can be successfully used in these measurements delivering more exact information about fluxes and also energy spectra of the analysed neutrons. These and other materials have threshold energy in the interesting energy range (0.5-15 MeV) and relatively large cross sections for the nuclear reactions, but have not been used in the activation measurements supposedly because produce daughter nuclides with a relatively short half-life time. We propose then some modification of the JET activation system mainly in order to convey the activation samples faster to the detector.

Prokopowicz, R. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, 00-908 Warsaw (Poland); Institute of Atomic Energy, 05-400 Otwock-Swierk (Poland); Scholz, M. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, 00-908 Warsaw (Poland); Szydlowski, A. [Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Popovichev, S. [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon 0X14 3DB (United Kingdom)

2008-03-19

196

Infrared Spectra and Hydrogen Bonds of Biologically Active Benzaldehydes  

NASA Astrophysics Data System (ADS)

IR-Fourier spectra of solutions and crystals of biologically active benzaldehyde derivatives were studied. Specific features of the formation of intra- and intermolecular hydrogen bonds were analyzed. Spectral signatures that characterized participation of the hydroxyl OH group and also the OCH3 and C=O groups in the formation of intramolecular hydrogen bonds of the three different types O-H···O-H, O-H···O-CH3, and O-H···O=C were revealed. Intramolecular hydrogen bonds of the types O-H···O-H and O-H···O-CH3 were absent for benzaldehyde derivatives in the crystal phase. Only hydroxyl and carbonyl groups participated in intermolecular interactions. This resulted in the formation of linear intermolecular dimers. Seven various configurations of the linear dimers were identified in solutions and crystals.

Tolstorozhev, G. B.; Skornyakov, I. V.; Belkov, M. V.; Shimko, A. N.; Shadyro, O. I.; Brinkevich, S. D.; Samovich, S. N.

2013-09-01

197

Neutron activation analysis of inorganic fillers for polymer composites  

NASA Astrophysics Data System (ADS)

The neutron activation analysis of inorganic fillers for organic composites has been made for the purpose of studying the radioactive nuclides produced in polymer composites by neutron irradiation. Five kinds of fillers such as glass fiber, mica flake, quartz powder, alumina fiber and silicon carbide fiber were chosen as typical samples. In the neutron-irradiated glass fiber and mica flake, various long-lived radioactive nuclides were detected. On the other hand, no appreciable amount of long-lived components was found in the irradiated specimens of quartz powder, alumina and silicon carbide fibers, indicating that these are desirable as candidate fillers for polymer composites used in intense neutron fields.

Yamaoka, H.; Matsushita, R.; Miyata, K.; Nakayama, Y.

1996-08-01

198

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

199

Neutron detectors for active interrogation of highly enriched uranium  

Microsoft Academic Search

We describe the results of our effort to optimize three neutron detector systems for active interrogation of highly enriched uranium: 1) a large-area detector for maximum total efficiency, 2) modular detectors for maximum flexibility in configuring a detector system for an application, and 3) a portable detector. All three systems contained He tubes, polyethylene to moderate the neutrons, and cadmium

C. E. Moss; C. A. Goulding; C. L. Hollas; W. L. Myers

2003-01-01

200

Neutron detectors for active interrogation of highly enriched uranium  

Microsoft Academic Search

We describe the results of our effort to optimize three neutron detector systems for active interrogation of highly enriched uranium: 1) a large-area detector for maximum absolute efficiency; 2) modular detectors for maximum flexibility in configuring a detector system for an application; and 3) a portable detector. All three systems contained 3He tubes, polyethylene to moderate the neutrons, and cadmium

C. E. Moss; C. A. Goulding; C. L. Hollas; W. L. Myers

2004-01-01

201

Neutron activation analysis of gold in teak (tectona grandis).  

National Technical Information Service (NTIS)

The amount of gold in teak had been determined by using neutron activation technique. The neutron flux utilized was of the order of 10(sup 10)n/cm(sup 2)/sec. As usual the spectrum of the energy peak of gold was identified using a gamma-multichannel pulse...

1968-01-01

202

High-capacity neutron activation analysis facility. [For NURE hydrogeochemical samples  

SciTech Connect

A high-capacity neutron activation analysis facility, the Reactor Activation Facility, was designed and built and has been in operation for about a year at one of the Savannah River Plant's production reactors. The facility determines uranium and about 19 other elements in hydrogeochemical samples collected in the National Uranium Resource Evaluation program, which is sponsored and funded by the United States Department of Energy, Grand Junction Office. The facility has a demonstrated average analysis rate of over 10,000 samples per month, and a peak rate of over 16,000 samples per month. Uranium is determined by cyclic activation and delayed neutron counting of the U-235 fission products; other elements are determined from gamma-ray spectra recorded in subsequent irradiation, decay, and counting steps. The method relies on the absolute activation technique and is highly automated for round-the-clock unattended operation.

Hochel, R.C.; Bowman, W.W.; Zeh, C.W.

1980-01-01

203

Energy Spectra of the Pneumatically Positioned Neutron Sources at LLNL'S Hazards Control Standards and Calibration Facility.  

National Technical Information Service (NTIS)

The Hazards Control Department of Lawrence Livermore National Laboratory maintains a Standards and Calibration Laboratory that includes three neutron sources (two sup 252 Cf and one sup 238 PuBe that can be positioned pneumatically for irradiations. Ten m...

J. H. Thorngate

1987-01-01

204

First Measurements of Neutron Spectra using the Magnetic Recoil Spectrometer (MRS) at OMEGA  

Microsoft Academic Search

A new type of neutron spectrometer, a Magnetic Recoil Spectrometer (MRS), is being implemented at OMEGA for measurements of the scattered-DT-neutron spectrum, from which rhoR can be inferred. Implementing an MRS at OMEGA is important for several reasons. First, it allows comprehensive tests of the different MRS parameters. Second, rhoR of cryogenic DT implosions can be inferred from both the

J. A. Frenje; D. Casey; C. K. Li; J. Rygg; F. H. Seguin; R. D. Petrasso; V. Yu. Glebov; D. D. Meyerhofer; T. C. Sangster; K. Fletcher

2007-01-01

205

Neutron spectra evaluation obtained from the track-size distribution on electrochemically etched CR39 foils  

Microsoft Academic Search

We are studying the relationship between neutron energy and track-size distribution on electrochemically etched CR-39 foils using a two-stage etching procedure. Although the electrochemical etching process alters the track size, we now find that the track diameter is related to the neutron energy even after the second stage (blowup) is completed. This relationship is complex, being effected by the etching

D. E. Hankins; J. Westermark

1987-01-01

206

Measurement of cold neutron spectra using a model cryogenic moderator of the IBR2M reactor  

Microsoft Academic Search

The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures of 10-50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the

S. A. Kulikov; I. V. Kalinin; V. M. Morozov; A. G. Novikov; A. V. Puchkov; A. N. Chernikov; E. P. Shabalin

2010-01-01

207

Measurement of cold neutron spectra using a model cryogenic moderator of the IBR2M reactor  

Microsoft Academic Search

The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures\\u000a of 10–50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the\\u000a study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the

S. A. Kulikov; I. V. Kalinin; V. M. Morozov; A. G. Novikov; A. V. Puchkov; A. N. Chernikov; E. P. Shabalin

2010-01-01

208

Determination of trace contaminants in hydrogenation catalysts by neutron-activation analysis.  

PubMed

A neutron-activation method has been developed for the determination of the active constituents and contaminants in hydrogenation catalysts. The active constituents of palladium and nickel catalysts (Pd and Ni) and Zn and Co contaminants present in small amount were determined by a direct instrumental method. A NaI(Tl) scintillator and a Ge(Li) semiconductor connected to a multichannel analyser were used for the measurements. A computer was used to evaluate the gamma-spectra. Contaminants present in small amount were also determined by means of a radiochemical separation method based on heterogeneous isotopic exchange on mercury(II) sulphide and zinc sulphide precipitates. PMID:18960846

Erdey, L; Gimesi, O; Szabó, E; Csajka, M

1970-12-01

209

The synchronous active neutron detection system for spent fuel assay  

SciTech Connect

The authors have begun to develop a novel technique for active neutron assay of fissile material in spent nuclear fuel. This approach will exploit the unique operating features of a 14-MeV neutron generator developed by Schlumberger. This generator and a novel detection system will be applied to the direct measurement of the fissile material content in spent fuel in place of the indirect measures used at present. The technique they are investigating is termed synchronous active neutron detection (SAND). It closely follows a method that has been used routinely in other branches of physics to detect very small signals in the presence of large backgrounds. Synchronous detection instruments are widely available commercially and are termed {open_quotes}lock-in{close_quotes} amplifiers. The authors have implemented a digital lock-in amplifier in conjunction with the Schlumberger neutron generator to explore the possibility of synchronous detection with active neutrons. This approach is possible because the Schlumberger system can operate at up to a 50% duty factor, in effect, a square wave of neutron yield. The results to date are preliminary but quite promising. The system is capable of resolving the fissile material contained in a small fraction of the fuel rods in a cold fuel assembly. It also appears to be quite resilient to background neutron interference. The interrogating neutrons appear to be nonthermal and penetrating. Although a significant amount of work remains to fully explore the relevant physics and optimize the instrument design, the underlying concept appears sound.

Pickrell, M.M.; Kendall, P.K.

1994-10-01

210

Utilization of Boron Irradiation Filters in Reactor Neutron Activation Via Epithermal (n, gamma ) and Fast Neutron Reactions. Application to Biological Matrices.  

National Technical Information Service (NTIS)

The technique of instrumental neutron activation analysis based on irradiation with reactor epithermal and fast neutrons has been described and evaluated. Important characteristics of boron neutron absorbers used to remove thermal neutrons from the reacto...

F. Chisela

1986-01-01

211

Measurements and evaluations of neutron dose and spectra at the reactor top of the liquid-metal fast breeder type reactor, JOYO  

SciTech Connect

To investigate the neutron dose and spectra around a fast reactor from the point of view of radiation protection and shielding, neutron measurements were conducted at the reactor top of JOYO, a Japanese experimental fast reactor, and an analysis by a transport calculation was performed. The measurements were carried out under a Mark II irradiation core with and without the reactor top concrete pit cover at 98- and 48-MW(thermal) power levels, respectively. The measurements were performed at several points in and around the reactor top pit room. Neutron detectors with well-examined response functions were employed for this study - the rem (sievert) counter as a neutron dosimeter and the multi-moderator neutron detector as a neutron spectrometer. The measured neutron doses distributed from 0.4 to 100 mrem/h . (100 MW(thermal)/sup -1/ )4 to 1000 ..mu..Sv/h . (100 MW(thermal))/sup -1/) and the measured neutron spectra showed an -- 1/E type energy distribution. The rapid spatial change of the neutron spectrum could not be observed near the reactor top. The neutron flux distributions around the reactor were calculated and compared with the measured results. The two-dimensional transport code DOT 3.5 was employed for the calculation, and the neutron group constants were prepared by using JENDL-2 cross-section libraries. The values of measurements and calculations were in relatively good agreement within a factor of 3 to 5 in spite of the 12-decade decrease in neutron flux from the reactor core center. It is shown that the effect of stored fuels in in-vessel storage racks has greatly affected the neutron dose rate at the reactor top. The modeling for shielding calculations of the iron rotating plug structures is discussed.

Kosako, T.; Matsumoto, J.; Sekiguchi, A.; Ohtani, N.; Suzuki, S.; Takeda, S.; Sato, O.

1987-06-01

212

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

213

The Problem of Interference in Neutron Activation Analysis.  

National Technical Information Service (NTIS)

Interference in emission spectrography refers to the difficulty in the identification of a spectrum line of a given element from that of another element. In neutron activation analysis two possible cases may occur: either the interfering radionuclide is i...

M. Rakovic

1968-01-01

214

Instrumental Neutron Activation Analysis and Multivariate Statistics for Pottery Provenance  

NASA Astrophysics Data System (ADS)

The application of instrumental neutron activation analysis and multivariate statistics to archaeological studies of ceramics and clays is described. A small pottery data set from the Nasca culture in southern Peru is presented for illustration.

Glascock, M. D.; Neff, H.; Vaughn, K. J.

2004-06-01

215

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

NASA Astrophysics Data System (ADS)

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. 631, 495 (2005)ASJOAB0004-637X10.1086/432525], we are able to determine the mass, the radius and the mass distribution of a star from its quasinormal 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.

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

2006-12-01

216

STUDY ON PALLADIUM DETERMINATION BY NEUTRON ACTIVATION ANALYSIS  

Microsoft Academic Search

This study presents results of Pd determinations in neutron activation analysis of spiked biological tissues and CCQM-P63 automotive catalyst. Pd spiked biological tissues of bovine muscle and liver were prepared using a blender with titanium blades and Pd solutions. These materials obtained in a past form were freeze-dried and homogenized before the analysis. Thermal and epithermal neutron activation analyses were

Cássio Q. Cavalcante; Mitiko Saiki

217

Human hair neutron activation analysis: Analysis on population level, mapping  

Microsoft Academic Search

Neutron activation analysis is an outstanding analytical method having very wide applications in various fields. Analysis\\u000a of human hair within last decades mostly based on neutron activation analysis is a very attractive illustration of the application\\u000a of nuclear analytical techniques. Very interesting question is how the elemental composition differs in different areas or\\u000a cities. In this connection the present paper

L. I. Zhuk; A. A. Kist

1999-01-01

218

Tooele NDE test report: LLNL 14-MeV Neutron Activation Group  

SciTech Connect

The concept of the 14-MeV Neutron Activation technique is to non- destructively identify unknown chemical elements or atom fractions in closed containers by irradiating the enclosed material with fast neutrons. Nuclear reactions between the neutrons and the atoms of the materials in the container will generally produce gamma rays of energies that are unique to each atom. Although the gamma ray spectra produced are sensitive only to the elements that are present -- not the specific chemical compounds -- some of the constituents of chemical weapon agents are sufficiently different from those of conventional munitions to easily distinguish them from the latter, and, in most cases, from other chemical agents. This is a non-contact method of non-destructive evaluation with a data collection time projected to be around 10--30 minutes per test item with an appropriate source and detector. Good statistical data from chlorine specimens can be obtained rapidly with a modest-strength neutron source, owing to the large radiative neutron capture cross section of chlorine. Although there is qualitative evidence for the other distinctive constituents of blister and nerve agents, namely, P, S, and F, the signature reactions for these elements have much smaller cross sections and need some combination of higher neutron flux, longer data acquisition times, or a more efficient detector. This was expected; it is evident from our preliminary data-base measurements made at LLNL, where data collection times of several hours were required to achieve good statistical accuracy in the times on the order of 10--30 minutes, we have ordered a pulsed neutron source with about two orders of magnitude greater average neutron flux than the PuBe source used for all data shown here. 4 refs., 3 figs.

Alvarez, R.A.; Rowland, M.S.

1991-06-20

219

Narrow absorption features in the co-added XMM-Newton RGS spectra of isolated neutron stars  

NASA Astrophysics Data System (ADS)

We co-added the available XMM-Newton Reflection Grating Spectrometer (RGS) spectra for each of the isolated X-ray pulsars RX J0720.4-3125, RX J1308.6+2127 (RBS1223), RX J1605.3+3249 and RX J1856.4-3754 (four members of the 'Magnificent Seven') and the 'Three Musketeers' Geminga, PSR B0656+14 and PSR B1055-52. We confirm the detection of a narrow absorption feature at 0.57 keV in the co-added RGS spectra of RX J0720.4-3125 and RX J1605.3+3249 (including most recent observations). In addition, we found similar absorption features in the spectra of RX J1308.6+2127 (at 0.53 keV) and maybe PSR B1055-52 (at 0.56 keV). The absorption feature in the spectra of RX J1308.6+2127 is broader than the feature e.g. in RX J0720.4-3125. The narrow absorption features are detected with 2-5.6? significance. Although very bright and frequently observed, there are no absorption features visible in the spectra of RX J1856.4-3754 and PSR B0656+14, while the co-added XMM-Newton RGS spectrum of Geminga has not enough counts to detect such a feature. We discuss a possible origin of these absorption features as lines caused by the presence of highly ionized oxygen (in particular O VII and/or O VI at 0.57 keV) in the interstellar medium and absorption in the neutron star atmosphere, namely the absorption features at 0.57 keV as gravitational redshifted (gr= 1.17) O VIII.

Hohle, M. M.; Haberl, F.; Vink, J.; de Vries, C. P.; Neuhäuser, R.

2012-01-01

220

The investigation of fast neutron Threshold Activation Detectors (TAD)  

NASA Astrophysics Data System (ADS)

The detection of fast neutrons is usually done by liquid hydrogenous organic scintillators, where the separation between the ever present gamma rays and neutrons is achieved by the pulse shape discrimination (PSD). In many practical situation the detection of fast neutrons has to be carried out while the intense source (be it neutrons, gamma rays or x-rays) that creates these neutrons, for example by the fission process, is present. This source, or ``flash'', usually blinds the neutron detectors and temporarily incapacitates them. By the time the detectors recover the prompt neutron signature does not exist. Thus to overcome the blinding background, one needs to search for processes whereby the desired signature, such as fission neutrons could in some way be measured long after the fission occurred and when the neutron detector is fully recovered from the overload. A new approach was proposed and demonstrated a good sensitivity for the detection of fast neutrons in adverse overload situations where normally it could not be done. A temporal separation of the fission event from the prompt neutrons detection is achieved via the activation process. The main idea, called Threshold Activation Detection (or detector)-TAD, is to find appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation, and then measure the radioactively decaying activation products (typically beta and ?-rays) well after the source pulse has ended. The activation material should possess certain properties: a suitable half-life; an energy threshold below which the numerous source neutrons will not activate it (e.g. about 3 MeV); easily detectable activation products and has a usable cross section for the selected reaction. Ideally the substance would be part of the scintillator. There are several good candidates for TAD. The first one we have selected is based on fluorine. One of the major advantages of this element is the fact that it is a major constituent of available scintillators (e.g., BaF2, CaF2, hydrogen free liquid fluorocarbon). Thus the activation products of the fast prompt neutrons, in particular, the beta particles, can be measured with a very high efficiency in the detector. Other detectors and substances were investigated, such as 6Li and even common detectors such as NaI. The principles and experimental results obtained with F, NaI and 6Li based TAD are shown. The various contributing activation products are identified. The insensitivity of the fluorine based TAD to (d,D) neutrons is demonstrated. Ways and means to reduce or subtract the various neutron induced activations of NaI detector are elucidated along with its fast neutron detection capabilities. 6Li could also be a useful TAD.

Gozani, T.; King, M. J.; Stevenson, J.

2012-02-01

221

Thermal neutron imaging in an active interrogation environment  

SciTech Connect

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 xcitation by high energy photons. The photo-induced neutrons can be either prompt or delayed, depending on whether neutronemitting 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,P.E.; Forman, L., and Norman, D.R.

2009-03-10

222

A simple method for the analysis of neutron resonance capture spectra  

Microsoft Academic Search

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

Martijn C. Clarijs; Victor R. Bom; Hans Postma; Carel W. E. van Eijk

223

A simple method for the analysis of neutron resonance capture spectra  

Microsoft Academic Search

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

Martijn C. Clarijs; Victor R. Bom; Carel W. E. van Eijk

2009-01-01

224

A simple method for the analysis of neutron resonance capture spectra  

Microsoft Academic Search

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

Martijn C. Clarijs; Victor R. Bom; Carel W. E. van Eijk

2009-01-01

225

Neutron threshold activation detectors (TAD) for the detection of fissions  

NASA Astrophysics Data System (ADS)

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (?3 vs. ?0.01) that are commonly used as indicators for the presence of fissionable materials.The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons.In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron "flash") where fission prompt neutrons could normally not be detected.The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator.There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF2, CaF2 and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector.The principles, applications and experimental results obtained with the fluorine based TAD are discussed.

Gozani, Tsahi; Stevenson, John; King, Michael J.

2011-10-01

226

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

227

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

228

Boron loaded plastic scintillator applied to active neutron measurements of waste drums  

Microsoft Academic Search

High efficiency neutron detectors are needed to do passive or active neutron measurement in order to characterize waste drum. In fact to measure prompt neutrons and fast neutrons, the cell should exhibit high detection efficiency and low mean lifetime of neutron inside its structures. At that time, this kind of cell uses only helium-3 gaseous detector inside a polyethylene structure.

S. Normand; P. Delacour; C. Passard; J. Loridon

2004-01-01

229

Neutron activation analysis of wheat samples.  

PubMed

The deficiency of essential micronutrients and excess of toxic metals in cereals, an important food items for human nutrition, can cause public health risk. Therefore, before their consumption and adoption of soil supplementation, concentrations of essential micronutrients and metals in cereals should be monitored. This study collected soil and two varieties of wheat samples-Triticum aestivum L. (Jordão/bread wheat), and Triticum durum L. (Marialva/durum wheat) from Elvas area, Portugal and analyzed concentrations of As, Cr, Co, Fe, K, Na, Rb and Zn using Instrumental Neutron Activation Analysis (INAA) to focus on the risk of adverse public health issues. The low variability and moderate concentrations of metals in soils indicated a lower significant effect of environmental input on metal concentrations in agricultural soils. The Cr and Fe concentrations in soils that ranged from 93-117 and 26,400-31,300mg/kg, respectively, were relatively high, but Zn concentration was very low (below detection limit <22mg/kg) indicating that soils should be supplemented with Zn during cultivation. The concentrations of metals in roots and straw of both varieties of wheat decreased in the order of K>Fe>Na>Zn>Cr>Rb>As>Co. Concentrations of As, Co and Cr in root, straw and spike of both varieties were higher than the permissible limits with exception of a few samples. The concentrations of Zn in root, straw and spike were relatively low (4-30mg/kg) indicating the deficiency of an essential micronutrient Zn in wheat cultivated in Portugal. The elemental transfer from soil to plant decreases with increasing growth of the plant. The concentrations of various metals in different parts of wheat followed the order: Root>Straw>Spike. A few root, straw and spike samples showed enrichment of metals, but the majority of the samples showed no enrichment. Potassium is enriched in all samples of root, straw and spike for both varieties of wheat. Relatively to the seed used for cultivation, Jordão presented higher transfer coefficients than Marialva, in particular for Co, Fe, and Na. The Jordão and Marialva cultivars accumulated not statistically significant different concentrations of different metals. The advantages of using INAA are the multielementality, low detection limits and use of solid samples (no need of digestion). PMID:21367605

Galinha, C; Anawar, H M; Freitas, M C; Pacheco, A M G; Almeida-Silva, M; Coutinho, J; Maçãs, B; Almeida, A S

2011-03-01

230

First Measurements of Neutron Spectra using the Magnetic Recoil Spectrometer (MRS) at OMEGA  

NASA Astrophysics Data System (ADS)

A new type of neutron spectrometer, a Magnetic Recoil Spectrometer (MRS), is being implemented at OMEGA for measurements of the scattered-DT-neutron spectrum, from which ?R can be inferred. Implementing an MRS at OMEGA is important for several reasons. First, it allows comprehensive tests of the different MRS parameters. Second, ?R of cryogenic DT implosions can be inferred from both the MRS and charged-particle spectrometry for moderate ?R implosions (?R<200 mg/cm^2); this allows for a definitive check of the MRS. Third, as there is no other way to determine ?R when it exceeds 200 mg/cm^2, the MRS will bring a required diagnostic to the OMEGA cryogenic program. Fourth, the experience with MRS implementation and resulting neutron data at OMEGA will enable us to implement an optimal MRS for the NIF. The results from the first MRS measurements performed at OMEGA are presented. This work was supported in part by the U.S. DOE (Grant No. DE-FG03-03SF22691), LLE (subcontract Grant No. 412160-001G), LLNL (subcontract Grant No. B504974).

Frenje, J. A.; Casey, D.; Li, C. K.; Rygg, J.; Seguin, F. H.; Petrasso, R. D.; Glebov, V. Yu.; Meyerhofer, D. D.; Sangster, T. C.; Fletcher, K.

2007-11-01

231

X-ray spectra from cooling neutron stars with no atmosphere  

NASA Astrophysics Data System (ADS)

Recent observations of the two ROSAT isolated neutron star candidates RX~J1856.5-3754 and RX~J0720.4-3125 with Chandra and XMM-Newton have shown that their spectrum is compatible with a featurless blackbody. This is in apparent contrast with the predictions of standard neutron star atmospheric models, according to which deviations from a blackbody shape and/or absorption features are expected. In particular, Chandra observations of RX J1856.5-3754 lead to the suggestion that this source may host a bare qua rk stars, since no atmosphere which could reprocess the thermal radiation from the deeper layers is present in this case. A s discussed by Lai &Salpeter( 1997), also neutron stars may be ``bare'', in the sense that no gaseous atmosphere sits on the top of the crust. This may happen is the star is cool (T < 10^5~K) and has a quite large magnetic field (B > 1013~G), so that a phase transition necessary occurs in the outermost layers. The expected emission, however, is not exactly a blackbody, as first discussed by Brinkmann (1980), because the plasma frequency is typically larger than the mean photon frequency. Actually both RX~J1856.5-3754 and RX~J0720.4-3125 may fall in the parameter range for which the phase transition occurs and no atmosphere is expected, at least if their surface composition is Fe rich. We discuss the thermal emission under such circumstances.

Zane, S.; Turolla, R.

232

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

233

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

2012-05-01

234

Measurements of 14 MeV Neutron Activation Cross Sections  

Microsoft Academic Search

In the neutron generator facility KORONA a neutron flux of 3 · 10 n\\/cms with an energy of 14.7 ± 0.3 MeV is available. A fast rabbit system transfers samples within 140 ms to the detector station. For activation analysis work a variety of reaction cross sections were determined:The reaction products have half-lives between 0.35 s and 64 d. For

Rudolf Pepelnik; Bernd Anders; Beni M. Bahal

1986-01-01

235

Comparison between the activation cross sections and integrated cross sections for the radiative capture of 14 MeV neutrons  

Microsoft Academic Search

Cross sections obtained by the integration of prompt gamma-ray spectra from the radiative capture of 14 MeV neutrons in a series of elements are presented and compared wilh the activation cross sections reported by different authors. In contrast to the activation cross-section values, which are scattered between 1 mb and 10 mb as a function of mass number, the integrated

F. Cvelbar; A. Hudoklin; M. Potokar

1970-01-01

236

Determination of hafnium in zirconium and its alloys by stable isotope dilution-neutron activation analysis. [Neutron reactions  

SciTech Connect

A new method, an isotope dilution method combined with neutron activation analysis, has been applied to the determination of traces of hafnium in zirconium and Zircaloys. A known amount of /sup 174/Hf-enriched hafnium solution was added to the sample as a spike. The mixture was dissolved and then irradiated in a reactor, together with natural and spike hafnium solutions. After cooling, the spiked hafnium was separated and the ..gamma..-ray spectra were measured, together with the natural and spike hafniums. The content of hafnium in the sample was calculated from the measured /sup 175/Hf//sup 181/Hf count rate ratio. A few parts-per-million of hafnium was determined with a relative standard deviation of 0.93%. The method was used to determine the value of hafnium in zirconium and Zircaloy reference materials, prepared by the National Bureau of Standards (NBS) and the Japan Atomic Energy Research Institute (JAERI). 3 figures, 4 tables.

Yonezawa, C.; Komori, T.

1983-11-01

237

The thick-target sup 9 Be(d,n) neutron spectra for deuteron energies between 2. 6 and 7. 0-MeV  

SciTech Connect

The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. {sup 235}U and {sup 238}U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of {le} 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV intervals, using time-of-flight techniques with flight paths of 2.7 and 6.8 meters. The results are presented in graphical form and in tables.

Meadows, J.W.

1991-11-01

238

The thick-target {sup 9}Be(d,n) neutron spectra for deuteron energies between 2.6 and 7.0-MeV  

SciTech Connect

The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. {sup 235}U and {sup 238}U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of {le} 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV intervals, using time-of-flight techniques with flight paths of 2.7 and 6.8 meters. The results are presented in graphical form and in tables.

Meadows, J.W.

1991-11-01

239

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

240

EU Blanket Design Activities and Neutronics Support Efforts  

SciTech Connect

An overview is provided of the design activities and the related neutronics support efforts conducted in the European Union for the development of breeder blankets for future fusion power reactors. The EU fusion programme considers two blanket lines, the Helium-Cooled Pebble Bed (HCPB) blanket with Lithium ceramics pebbles (Li{sub 4}SiO{sub 4} or Li{sub 2}TiO{sub 3}) as breeder and beryllium pebbles as neutron multiplier, and the Helium-Cooled Lithium-Lead (HCLL) blanket with the Pb-Li eutectic alloy as breeder and neutron multiplier. The blanket design and the related R and D efforts are based on the use of the same coolant and the same modular blanket structure to minimise the development costs as much as possible. The neutronic support efforts include design analyses for the layout and optimization of the modular HCPB/HCLL blankets based on detailed three-dimensional Monte Carlo calculations as well as underlying neutronics activities conducted in the frame of the European Fusion and Activation File (EFF/EAF) projects to develop qualified nuclear data and computational tools for reliable neutronics design calculations.

Fischer, U. [Forschungszentrum Karlsruhe (Germany); Batistoni, P. [ENEA Fusion Division (Italy); Boccaccini, L.V. [Forschungszentrum Karlsruhe (Germany); Giancarli, L. [CEA Saclay (France); Hermsmeyer, S. [Forschungszentrum Karlsruhe (Germany); Poitevin, Y. [CEA Saclay (France)

2005-05-15

241

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 7.5×105, 1.6×104, and 1.1×105 n/cm2/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

242

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

Microsoft Academic Search

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

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

2004-01-01

243

Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometer  

SciTech Connect

For the first time high areal-density (rhoR) cryogenic deuterium-tritium (DT) implosions have been probed using downscattered neutron spectra measured with the magnetic recoil spectrometer (MRS) [J. A. Frenje et al., Rev. Sci. Instrum. 79, 10E502 (2008)], recently installed and commissioned on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The rhoR data obtained with the MRS have been essential for understanding how the fuel is assembled and for guiding the cryogenic program at the Laboratory for Laser Energetics (LLE) to rhoR values up to approx300 mg/cm{sup 2}. The rhoR data obtained from well-established charged particle spectrometry techniques [C. K. Li et al., Phys. Plasmas 8, 4902 (2001)] were used to authenticate the MRS data for low-rhoR plastic capsule implosions, and the rhoR values inferred from these techniques are in excellent agreement, indicating that the MRS technique provides high-fidelity data. Recent OMEGA-MRS data and Monte Carlo simulations have shown that the MRS on the NIF [G. H. Miller et al., Nucl. Fusion 44, S228 (2004)] will meet most of the absolute and relative requirements for determining rhoR, ion temperature (T{sub i}) and neutron yield (Y{sub n}) in both low-yield, tritium-rich, deuterium-lean, hydrogen-doped implosions and high-yield DT implosions.

Frenje, J. A.; Casey, D. T.; Li, C. K.; Seguin, F. H.; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Glebov, V. Yu.; Radha, P. B.; Sangster, T. C.; Meyerhofer, D. D. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Hatchett, S. P.; Haan, S. W.; Cerjan, C. J.; Landen, O. L. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Fletcher, K. A. [Geneseo State University, Geneseo, New York 14454 (United States); Leeper, R. J. [Sandia National Laboratory, New Mexico 87123 (United States)

2010-05-15

244

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

245

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

246

Multiple-Coincidence Active Neutron Interrogation of Fissionable Materials  

SciTech Connect

Using a beam of tagged 14.1 MeV neutrons to probe for the presence of fissionable materials, we have measured n-?-? coincidences from depleted uranium (DU). The multiple coincidence rate is substantially above that measured from lead, tungsten, and iron. The presence of coincidences involving delayed gammas in the DU time spectra provides a signature for fissionable materials that is distinct from non-fissionable ones. In addition, the information from the tagged neutron involved in the coincidence gives the position of the fissionable material in all three dimensions. The result is an imaging probe for fissionable materials that is more compact and that produces much less radiation than other solutions.

J.P. Hurley, R.P. Keegan, J.R. Tinsley, R. Trainham, and S.C. Wilde

2008-08-06

247

Quasi-monoenergetic neutron energy spectra for 246 and 389 MeV 7Li(p,n) reactions at angles from 0° to 30°  

NASA Astrophysics Data System (ADS)

The authors measured the neutron energy spectra of a quasi-monoenergetic 7Li(p,n) neutron source with 246 and 389 MeV protons set at seven angles (0°, 2.5°, 5°, 10°, 15°, 20° and 30°), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. The energy spectra of the source neutrons were precisely deduced down to 2 MeV at 0° and 10 MeV at other angles. The cross-sections of the peak neutron production reaction at 0° were on the 35-40 mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV changed considerably with the angle. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron monitors such as DARWIN and Wendi-2, the authors showed the subtractions of H*(10) obtained at larger angles (10°, 15°, 20° and 30°) from the 0° data in the continuum part for the 246 and 389 MeV 7Li(p,n) reactions. It was found that subtracting the dose equivalent at about 20° from the 0° data almost eliminates the continuum component. This method has potential to eliminate problems associated with continuum correction for high-energy neutron monitors.

Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Iwase, Hiroshi; Yashima, Hiroshi; Itoga, Toshiro; Sato, Tatsuhiko; Nakane, Yoshihiro; Nakashima, Hiroshi; Sakamoto, Yukio; Matsumoto, Tetsuro; Masuda, Akihiko; Nishiyama, Jun; Tamii, Atsushi; Hatanaka, Kichiji; Theis, C.; Feldbaumer, E.; Jaegerhofer, L.; Pioch, C.; Mares, V.; Nakamura, Takashi

2011-02-01

248

Neutron activation analysis of an Egyptian monazite ore sample  

Microsoft Academic Search

The absolute sensitivity of a gamma-ray line following thermal or epithermal neutron activation is expressed as a product of four terms, namely, the intrinsic, irradiation, decay and measurement factors. The total absolute sensitivity is the sum of the absolute sensitivities due to thermal and epithermal activation. A. FORTRAN computer program was prepared on the TANDY 3000 NL PCA to calculate

E. A. Eissa; N. B. Rofail; L. S. Ashmawy; A. M. Hassan

1999-01-01

249

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

SciTech Connect

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

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

1984-05-01

250

Elemental analysis of some Egyptian ores and industrial iron samples by neutron activation analysis.  

PubMed

Elemental analysis of iron ore samples and first industrial iron production prepared by the Egyptian Iron and Steel Company of Helwan near Cairo were determined by instrumental neutron activation analysis technique. Five samples from each kind were irradiated for a 48 hours at a thermal neutron flux of 4 x 10(12) n/(cm2.s) in the first Egyptian research reactor ET-RR-1. Also the Pneumatic irradiation Rabbit system (PIRS) attached to the reactor in Inshass, was used to measure the elements of short-life time. The gamma-ray spectra were recorded by means of the hyper pure germanium detection system. The concentration percentage values of major, minor and trace elements are presented. The long and short lived isotopes were considered. A comparative study and a discussion on the elemental concentration values are given. PMID:11590711

Srror, A; Abdel-Basset, N; Abdel-Haleem, A S; Hassan, A M

2001-01-01

251

Improvement of the matrix effect compensation in active neutron measurement by simulated annealing algorithm (June 2009)  

Microsoft Academic Search

To answer safety authority requirements and to optimise the management of radioactive waste produced in retrieval and decommissioning activities, which contains a large variety of matrix materials, the accuracy of neutron measurement techniques has to be continuously improved. Active neutron measurements such as the Differential Die-Away (DDA) technique involving pulsed neutron generator as the neutron source, are widely applied to

A.-C. Raoux; J. Loridon; A. Mariani; C. Passard

2009-01-01

252

Neutron activation of four ferritic steels  

SciTech Connect

Four ferritic steels (Table 1) were compared using two simplified fusion reactor geometries. In the MFE geometry, a 14.1-MeV point source was centered inside a 5 m radius vessel. The 2 cm thick first wall was surrounded by a reflector consisting of 78 cm Li, 18 cm graphite, 2 cm B/sub 4/C, and a 10 cm thick outer wall. In the ICF geometry, the neutron source was in a compressed plasma (rho R = 3 g/cm/sup 2/), and the region between 0.5 and 2.0 m was filled with Li at 50% of the natural density.

Blink, J.A.

1983-06-01

253

Calibration of the delayed-gamma neutron activation facility  

SciTech Connect

The delayed-gamma neutron activation facility at Brookhaven National Laboratory was originally calibrated using an anthropomorphic hollow phantom filled with solutions containing predetermined amounts of Ca. However, 99{percent} of the total Ca in the human body is not homogeneously distributed but contained within the skeleton. Recently, an artificial skeleton was designed, constructed, and placed in a bottle phantom to better represent the Ca distribution in the human body. Neutron activation measurements of an anthropomorphic and a bottle (with no skeleton) phantom demonstrate that the difference in size and shape between the two phantoms changes the total body calcium results by less than 1{percent}. To test the artificial skeleton, two small polyethylene jerry-can phantoms were made, one with a femur from a cadaver and one with an artificial bone in exactly the same geometry. The femur was ashed following the neutron activation measurements for chemical analysis of Ca. Results indicate that the artificial bone closely simulates the real bone in neutron activation analysis and provides accurate calibration for Ca measurements. Therefore, the calibration of the delayed-gamma neutron activation system is now based on the new bottle phantom containing an artificial skeleton. This change has improved the accuracy of measurement for total body calcium. Also, the simple geometry of this phantom and the artificial skeleton allows us to simulate the neutron activation process using a Monte Carlo code, which enables us to calibrate the system for human subjects larger and smaller than the phantoms used as standards. {copyright} {ital 1996 American Association of Physicists in Medicine.}

Ma, R.; Zhao, X.; Rarback, H.M.; Yasumura, S.; Dilmanian, F.A.; Moore, R.I.; Lo Monte, A.F.; Vodopia, K.A.; Liu, H.B.; Economos, C.D.; Nelson, M.E.; Aloia, J.F.; Vaswani, A.N.; Weber, D.A.; Pierson, R.N. Jr.; Joel, D.D. [Medical Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

1996-02-01

254

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

255

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

NASA Astrophysics Data System (ADS)

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.

2013-06-01

256

Neutron activation analysis of essential elements in Multani mitti clay using miniature neutron source reactor.  

PubMed

Multani mitti clay was studied for 19 essential and other elements. Four different radio-assay schemes were adopted for instrumental neutron activation analysis (INAA) using miniature neutron source reactor. The estimated weekly intakes of Cr and Fe are high for men, women, pregnant and lactating women and children while intake of Co is higher in adult categories and Mn by pregnant women. Comparison of MM clay with other type of clays shows that it is a good source of essential elements. PMID:22871439

Waheed, S; Rahman, S; Faiz, Y; Siddique, N

2012-07-04

257

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.

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

2009-01-01

258

Borehole neutron activation: The rare earths  

SciTech Connect

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 offer the mining geologist techniques for 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 as 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 new application of the rare-earth elements to high-temperature superconductors, these elements are examined in detail as an example of how nuclear techniques can assist the mining geologist.

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

1988-02-01

259

Delayed-gamma signature calculation for neutron-induced fission and activation using MCNPX, Part I: Theory  

Microsoft Academic Search

The capability to conduct automated radiation-transport simulations of delayed-gamma emission spectra at discrete (line) energies created by the products of neutron fission and activation has been developed for MCNPX. To do so, the CINDER'90 isotopic transmutation code has been merged into MCNPX to seamlessly supply time-dependent, decay-chain atom densities for 3400 nuclides. A new dataset containing ENDF\\/B-VI emission-probability line data

Joe W. Durkee Jr.; Michael R. James; Gregg W. McKinney; Holly R. Trellue; Laurie S. Waters; William B. Wilson

2009-01-01

260

Delayed-gamma signature calculation for neutron-induced fission and activation using MCNPX. Part II: Simulations  

Microsoft Academic Search

In Part I, we presented the theory for the MCNPX Monte Carlo delayed-gamma emission feature. This feature permits the automated execution of radiation transport simulations of delayed-gamma emission spectra at discrete (line) energies created by the products of neutron fission and activation. To illustrate and help validate the new capability, calculated delayed-gamma emissions are presented in Part II for a

Joe W. Durkee Jr.; Michael R. James; Gregg W. McKinney; Holly R. Trellue; Laurie S. Waters; William B. Wilson

2009-01-01

261

Determination of fission neutron transmission through waste matrix material using neutron signal correlation from active assay of {sup 239}Pu  

SciTech Connect

The accuracy of TRU (transuranic) waste assay using the differential die-away technique depends upon significant corrections to compensate for the effects of the matrix material in which the TRU waste is located. The authors have used a new instrument, the Combined Thermal/Epithermal Neutron (CTEN) instrument for the assay of TRU waste, to develop methods to improve the accuracy of these corrections. Neutrons from a pulsed 14-MeV neutron generator are moderated in the walls of the CTEN cavity and induce fission in the TRU material. The prompt neutrons from these fission events are detected in cadmium-wrapped {sup 3}He neutron detectors. They report new methods of data acquisition and analysis to extract correlation in the neutron signals resulting form fission during active interrogation. They use the correlation information in conjunction with the total number of neutrons to determine the fraction of fission neutrons transmitted through the matrix material into the {sup 3}He detectors. This determination allows them to cleanly separate the matrix effects into two processes: matrix modification upon the neutron interrogating flux and matrix modification upon the fraction of fission neutrons transmitted to the neutron detectors. This transmission information is also directly applied in a neutron multiplicity analysis in the passive assay of {sup 240}Pu.

Hollas, C.L.; Arnone, G.; Brunson, G.; Coop, K.

1996-09-01

262

Calibration of the delayed-gamma neutron activation facility  

Microsoft Academic Search

The delayed-gamma neutron activation facility at Brookhaven National Laboratory was originally calibrated using an anthropomorphic hollow phantom filled with solutions containing predetermined amounts of Ca. However, 99% of the total Ca in the human body is not homogeneously distributed but contained within the skeleton. Recently, an artificial skeleton was designed, constructed, and placed in a bottle phantom to better represent

R. Ma; X. Zhao; H. M. Rarback; S. Yasumura; F. A. Dilmanian; R. I. Moore; A. F. Lo Monte; K. A. Vodopia; H. B. Liu; C. D. Economos; M. E. Nelson; J. F. Aloia; A. N. Vaswani; D. A. Weber; R. N. Pierson Jr.

1996-01-01

263

Neutron and gamma-Ray Spectroscopy and Activation Analysis.  

National Technical Information Service (NTIS)

The objectives of this contract were to carry out basic research in the areas of neutron spectroscopy and dosimetry, gamma-ray spectroscopy and dosimetry, and activation analysis techniques. Early work in gamma-ray spectroscopy was done mostly with the be...

N. C. Rasmussen T. J. Thompson

1966-01-01

264

Addressing different active neutron interrogation signatures from fissionable material  

Microsoft Academic Search

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

David L. Chichester; Edward H. Seabury

2009-01-01

265

Multi-Element Neutron Activation Analysis of Brazilian Coal Samples.  

National Technical Information Service (NTIS)

The elements U, Th, La, Ce, Nd, Sm, Eu, Dy, Tb, Yb, Lu, Sc, Ta, Hf, Co, Ni, Cr, Mo, Ti, V, W, In, Ga, Mn, Ba, Sr, Mg, Rb, Cs, K, Cl, Br, As, Sb, Au, Ca, Al and Fe were determined in coal samples by instrumental neutron activation analysis, by using both t...

L. T. Atalla C. S. Requejo

1982-01-01

266

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

267

Multielement determination in river water by neutron activation analysis  

Microsoft Academic Search

Concentrations of Al, Br, Ca, Ce, Co, Cr, Eu, Fe, Hf, La, Lu, Mg, Mn, Na, Rb, Sc, Sm, Sr, Tb, Th, Ti, V, Yb, Zn, and Zr have been measured in Tigris and Euphrates river water, using neutron activation analysis in combination with preconcentration technique. River water samples were preconcentrated by evaporation at 70°C under atmospheric pressure. The samples

M. B. H. Al-Bedri; S. Al-Jobori

1991-01-01

268

Background and Source Term Identification in Active Neutron Interrogation Methods.  

National Technical Information Service (NTIS)

The detection and tracking of special nuclear material (SNM) is vitally important in order to know where these materials are and prevent them from being used in a harmful manner. Active neutron interrogation is a sought after method for this since the res...

D. A. Anthony

2011-01-01

269

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

PubMed

Fast neutrons (FN) have a higher radio-biological effectiveness (RBE) compared with photons, however the mechanism of this increase remains a controversial issue. RBE variations are seen among various FN facilities and at the same facility when different tissue depths or thicknesses of hardening filters are used. These variations lead to uncertainties in dose reporting as well as in the comparisons of clinical results. Besides radiobiology and microdosimetry, another powerful method for the characterization of FN beams is the calculation of total proton and heavy ion kerma spectra. FLUKA and MCNP Monte Carlo code were used to simulate these kerma spectra following a set of microdosimetry measurements performed at the National Accelerator Centre. The calculated spectra confirmed major classical statements: RBE increase is linked to both slow energy protons and alpha particles yielded by (n,alpha) reactions on carbon and oxygen nuclei. The slow energy protons are produced by neutrons having an energy between 10 keV and 10 MeV, while the alpha particles are produced by neutrons having an energy between 10 keV and 15 MeV. Looking at the heavy ion kerma from <15 MeV and the proton kerma from neutrons <10 MeV, it is possible to anticipate y* and RBE trends. PMID:11233567

Pignol, J P; Slabbert, J

2001-02-01

270

Thin film thickness determination with neutron activation analysis.  

PubMed

Thickness determination of Ta2O5 thin films, deposited on the glass substrates and metallic indium and gold thin films on both glass and aluminum substrates, were performed by neutron activation analysis. Thickness determination of these thin films were made by comparing gamma-rays emitted from the radio-isotopes in the thin film with the substrate material followed by the neutron irradiations. The method led to determination of the film thicknesses without using any standard sample. A complementary optical transmission measurement was also applied on multi-layered Ta2O5 thin films for determining the individual layer densities. PMID:11339537

Ozben, C S; Tepehan, F Z; Güven, H H; Tepehan, G G

2001-07-01

271

MC2; fast neutron spectra and multigroup cross section. [IBM360,370; CDC7600; FORTRAN IV (99nd Assembly language (1IBM370), FORTRAN IV (99) and COMPASS (1) (CDC7600)  

Microsoft Academic Search

MC**2-2 solves the neutron slowing-down equations using basic neutron data derived from ENDF\\/B data files to determine spectra for use in generating multigroup neutron cross sections. The current edition includes the ability to treat all ENDF\\/B-V representations, high-order PL scattering representations, a free-format input processor, isotope mixing, delayed neutron processing, and flexibility in output data selection.IBM360,370;CDC7600; FORTRAN IV (99%) and

T. B. Fowler; M. L. Tobias; J. N. Fox; B. E. Lawler; J. U. Koppel; J. R. Triplett; L. L. Lynn; L. A. Waldman; I. Goldberg; P. Greebler; M. D. Kelley; R. A. Davis; C. E. Keck; J. A. Redfield; J. H. Murphy; C. G. Stenberg

2008-01-01

272

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

273

Determination of trace impurities in platinum by neutron activation analysis  

Microsoft Academic Search

Determination of trace impurities in platinum by neutron activation analysis was carried ont by combining the advantages of\\u000a ion exchange chromatography and Ge(Li spectrometry. Owing to the development of a new ion exchange separation scheme which\\u000a assures high decontamination factors with respect to matrix activities and practically quantitative yields, ppm and sub ppm\\u000a amounts of Au, Cu, Ir, K, La,

H. Maleszewska; R. Dybczy?ski

1976-01-01

274

Neutron activation analysis of an Egyptian monazite ore sample  

Microsoft Academic Search

The absolute sensitivity of a gamma-ray line following thermal or epithermal neutron activation is expressed as a product\\u000a of four terms, namely, the intrinsic, irradiation, decay and measurement factors. The total absolute sensitivity is the sum\\u000a of the absolute sensitivities due to thermal and epithermal activation. A. FORTRAN computer program was prepared on the TANDY\\u000a 3000 NL PCA to calculate

E. A. Eissa; N. B. Rofail; L. S. Ashmawy; A. M. Hassan

1999-01-01

275

A Compton suppression spectrometer for neutron activation analysis  

Microsoft Academic Search

A Compton suppression spectrometer consisting of a system of three Ge detectors surrounded by a BGO shield and a CsI(T1) active collimator has been set up for the use in neutron activation analysis. Tests of the performance of the system concerning Compton suppression, peak reduction and effects of the count rate in an energy range 300–2000 keV are described. A

E. Mauerhofer; U. Tharun; H. O. Denschlag; R. Schmidt; J. V. Kratz

1996-01-01

276

Fusion of time-dependent gamma production spectra from thermal neutron capture and fast neutron inelastic scattering to improve material detection  

Microsoft Academic Search

Neutron-based inspection techniques are unique in their ability to provide material specific signatures, thus offering very high performance and automatic detection of explosives and other contraband. Thermal neutron capture gamma spectroscopy provides excellent sensitivities to hydrogen, nitrogen, chlorine, and other elements, which are characteristic to most explosives, drugs and other contraband that may be smuggled into the country. Fast neutron

T. Gozani; M. Elsalim; D. Strellis; D. Brown

2003-01-01

277

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

278

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

279

AMERICIUM-BERYLLIUM AND PLUTONIUM-BERYLLIUM NEUTRON SOURCE RELATIVE EFFECTIVENESS IN PROMPT-GAMMA ACTIVATION ANALYSIS  

Microsoft Academic Search

S>The relative effectiveness in prompt-gamma neutron activation analysis ; of two Pu-Be isotopic neutron sources and an Am - Be neutron source is compared. ; Thermal neutron levels and the associated gamma radiation produced by these ; sources in a standard moderating system are normalized to the nominal neutron ; emission rate. The methods of measurement include a BFâ neutron

E. D. Jordan; H. E. Schierling

1962-01-01

280

Monte-Carlo simulations of neutron-induced activation in a Fast-Neutron and Gamma-Based Cargo Inspection System  

NASA Astrophysics Data System (ADS)

An air cargo inspection system combining two nuclear reaction based techniques, namely Fast-Neutron Resonance Radiography and Dual-Discrete-Energy Gamma Radiography is currently being developed. This system is expected to allow detection of standard and improvised explosives as well as special nuclear materials. An important aspect for the applicability of nuclear techniques in an airport inspection facility is the inventory and lifetimes of radioactive isotopes produced by the neutron radiation inside the cargo, as well as the dose delivered by these isotopes to people in contact with the cargo during and following the interrogation procedure. Using MCNPX and CINDER90 we have calculated the activation levels for several typical inspection scenarios. One example is the activation of various metal samples embedded in a cotton-filled container. To validate the simulation results, a benchmark experiment was performed, in which metal samples were activated by fast-neutrons in a water-filled glass jar. The induced activity was determined by analyzing the gamma spectra. Based on the calculated radioactive inventory in the container, the dose levels due to the induced gamma radiation were calculated at several distances from the container and in relevant time windows after the irradiation, in order to evaluate the radiation exposure of the cargo handling staff, air crew and passengers during flight. The possibility of remanent long-lived radioactive inventory after cargo is delivered to the client is also of concern and was evaluated.

Bromberger, B.; Bar, D.; Brandis, M.; Dangendorf, V.; Goldberg, M. B.; Kaufmann, F.; Mor, I.; Nolte, R.; Schmiedel, M.; Tittelmeier, K.; Vartsky, D.; Wershofen, H.

2012-03-01

281

Instrumental neutron activation analysis of some ancient punchmark coins from India  

Microsoft Academic Search

A nondestructive instrumental neutron activation analysis technique is applied for the analysis of precious ancient punchmark coins. Coins ranging between 8th century B.C. to 2nd century B.C. were irradiated with thermal neutrons in a252Cf neutron source facility and analyzed by comparator method of instrumental neutron activation analysis, using high purity germanium detector coupled to a multichannel analyzer, the activities being

Nilima S. Rajurkar; A. K. Jha; Ranjana P. Bhadane

1994-01-01

282

Inelastic neutron scattering and vibrational spectra of 2-( N-methyl-?-iminoethyl)-phenol and 2-( N-methyliminoethyl)-phenol: Experimental and theoretical approach  

Microsoft Academic Search

The infrared, Raman, and inelastic neutron scattering (INS) spectra of two ortho-hydroxy aryl Schiff’s bases, 2-(N-methyliminoethyl)-phenol and 2-(N-methyl-?-iminoethyl)-phenol, were recorded. Ab initio molecular orbital calculations employing the DFT (B3LYP) method with the 6-31G?? basis set for both compounds were done. Assignments of vibrational modes within the 3500–50cm?1 spectral region were carried out. On the basis of the DFT calculations, four

A. Filarowski; A. Koll; P. Lipkowski; A. Pawlukoj?

2008-01-01

283

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

Microsoft Academic Search

Within the EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) project, the gamma-ray spectra produced in a series of materials by 14-MeV tagged-neutron beams have been collected in the inspection portal equipped with large volume NaI(Tl) detectors, in order to build a database of signatures for various elements: C, N, O, Na, Al, Si, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn,

B. Perot; C. Carasco; S. Bernard; A. Mariani; J.-L. Szabo; G. Sannie; V. Valkovic; D. Sudac; G. Viesti; M. Lunardon; C. Botosso; G. Nebbia; S. Pesente; S. Moretto; A. Zenoni; A. Donzella; M. Moszynski; M. Gierlik; W. Klamra; P. Le Tourneur; M. Lhuissier; A. Colonna; C. Tintori; P. Peerani; V. Sequeira; M. Salvato

2008-01-01

284

Accelerator-based neutron fields for the mock up of workplace spectra – first experimental results and comparison with calculations  

Microsoft Academic Search

The energy dependence of the fluence response of a neutron radiation protection monitor generally deviates considerably from that of the fluence-to-dose equivalent conversion function. For the dose determination in a given neutron field such a monitor must therefore be calibrated by determining its yield and the dose equivalent in a neutron field similar to the given field. A wide class

B. Wiegel; B. R. L Siebert; S. Guldbakke; J. Wittstock

1999-01-01

285

Spectra and Luminosities of X-Ray Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

I present results of the analysis of 112 X-ray -selected and fully optically-identified quasars in four sky fields in the southern hemisphere, detected by the Rosat Position Sensitive Proportional Counters. These fields were originally studied (Boyle et al. 1990) for the ultraviolet-excess properties of objects in the fields. This is one of the largest sets of fully-identified Rosat-observed quasars. The quasars were optically identified during observing runs with the AUTOFIB multi-fiber spectrograph on the Anglo-Australian Telescope in Australia. I determine the quasars' power-law spectral index alphaE with three different methods: spectral "stacking", hardness ratios, and direct fitting, and discuss the differences between each of these methods. Both spectral stacking and the hardness ratio methods are used because several of the quasars were too dim to reliably calculate spectral indices individually. The spectral stacking method, which involves co-adding quasar spectra energy bins (after first binning the quasars themselves in redshift bins) shows that a definite change in quasar spectral index with redshift, which I have attributed to thermal bremsstrahlung emission (Morgan et al. 1992). The hardness ratio method, taken from a suggestion by Zamorani et al. (1988), uses the hardness ratios, using energy bins of 0.15-0.8 keV and 0.8-2.0 keV, and the known galactic column density N_{H } to determine the quasar power-law spectral index. I find that the hardness-ratio method yields spectral indices which do not change appreciably with redshift. I derive monochromatic X-ray and optical luminosities L_{rm x} and L opt, by using the spectral indices I found and the optical observations of the quasars. I discuss the relationship between L_{x } and Lopt, examine the optical-X-ray spectral slope alpha ox and the related L x/L_{opt } ratio and their relationship to the redshift. I finally present a model which could explain the observations.

Morgan, Windsor Anthony, Jr.

1995-01-01

286

Thermal Neutron Die-Away Studies in a 14 MeV Neutron-Based Active Interrogation System  

Microsoft Academic Search

The ability to classify cargos is a critical step in developing cargo dependent algorithms to improve the detection of threats like explosive or nuclear materials concealed in cargo. In a conventional pulsed neutron based active interrogation system, fast neutrons (e.g., 14 MeV) are thermalized as they travel through a moderating cargo. Once they are thermalized, they can be absorbed by

Ryan M. Yee; Timothy J. Shaw; Tsahi Gozani

2009-01-01

287

Nondestructive neutron activation analysis of volcanic samples: Hawaii  

SciTech Connect

Samples of volcanic emissions have been collected between and during eruptions of both Kilauea and Mauna Loa volcanoes during the last three years. Airborne particles have been collected on Teflon filters and acidic gases on base-impregnated cellulose filters. Chemically neutral gas-phase species are collected on charcoal-coated cellulose filters. The primary analytical technique used is nondestructive neutron activation analysis, which has been used to determine the quantities of up to 35 elements on the different filters. The use of neutron activation analysis makes it possible to analyze for a wide range of elements in the different matrices used for the collection and to learn about the distribution between particles and gas phases for each of the elements.

Zoller, W.H.; Finnegan, D.L.; Crowe, B.

1986-01-01

288

THORIUM IN STONE METEORITES BY NEUTRON ACTIVATION ANALYSIS  

Microsoft Academic Search

Radiochemical procedures for assay of Pa²³³ following neutron ; activation of Th²³² in stone meteorites are described in detail. Eight ; analyses of five chondrites yielded an average concentration of (3.96 plus or ; minus 0.20) x 10⁻⁸g Th\\/g which with proper assumptions, leads to a cosmic ; atomic abundance of 0.026 for thorium (per 10⁶ Si atoms). The thorium

G. L. Bate; J. R. Huizenga; H. A. Potratz

1959-01-01

289

DETERMINATION OF BROMINE IN STONY METEORITES BY NEUTRON ACTIVATION  

Microsoft Academic Search

Eighteen chondrites and seven achondrites have been analyzed for bromine by thermal neutron activation. Fourteen of the specimens were analyzed in replicate. Bromine is found to be fractionareal among the three types of chondrites: carbonaceous 3.04, enstatite 1.64, and ordinary 0.34 ppm Br. This trend is similar to the depletion pattern found by other investigators for iodine. Bromine is found

K. W. Lieberman; W. D. Ehmann

1967-01-01

290

Determination of some precious metals by neutron activation analysis  

Microsoft Academic Search

A neutron activation procedure for the determination of Ru, Pd, Os, Ir, Pt and Au in a single irradiation in silicate rocks,\\u000a meteorites and sulfide ores has been developed. An alkali fusion was used to dissolve and mix 100 to 200 mg powder samples\\u000a with appropriate carriers. The individual metals were separated and brought to a state of high radiochemical

J. H. Crocket; R. R. Keays; S. Hsieh

1968-01-01

291

Diagnostic Application of Absolute Neutron Activation Analysis in Hematology  

SciTech Connect

The Absolute Neutron Activation Analysis (ANAA) technique was used to determine element concentrations of Cl and Na in blood of healthy group (male and female blood donators), select from Blood Banks at Sao Paulo city, to provide information which can help in diagnosis of patients. This study permitted to perform a discussion about the advantages and limitations of using this nuclear methodology in hematological examinations.

Zamboni, C.B.; Oliveira, L.C.; Dalaqua, L. Jr.

2004-10-03

292

Activation of Flibe with 14 MeV DT neutrons  

Microsoft Academic Search

We have prepared and irradiated pellet-shaped Flibe (Li2BeF4) samples with 14 MeV DT neutrons. Two irradiations of 1 min and 19 hours duration were carried out and the gamma activation was measured afterwards. Lines of 19O as well as of 28Al were identified in the short-time measurement. In the longtime irradiation experiment, strong lines from 24Na generated from impurities were

Axel Klix; Hidetoshi Nishimura; Akihito Suzuki; Teruya Tanaka; Satoshi Sato; Takayuki Terai; Li Zaixin; Takeo Nishitani; Akio Sagara; Takeo Muroga

2005-01-01

293

Performance of the delayed- and prompt-gamma neutron activation systems at Brookhaven National Laboratory  

Microsoft Academic Search

Brookhaven National Laboratory (BNL) is one of the major facilities pioneering the development of In Vivo Neutron Activation (IVNA) techniques for body composition studies. The IVNA facility at BNL includes a delayed- and prompt-gamma neutron activation system (DGNA and PGNA), as well as an inelastic neutron scattering facility (INS). The BNL DGNA system was first fully established in the 1960's.

F. A. Dilmanian; D. A. Weber; S. Yasumura; J. J. Kehayias; K. J. Ellis; Y. Kamen; L. Lidofsky; S. B. Heymsfield; R. N. Jr. Pierson; J. Wang

1989-01-01

294

Determination of iodine in biological materials by epithermal neutron activation analysis  

Microsoft Academic Search

Epithermal neutron activation analysis (ENAA) has been used for the rapid, reliable nondestructive determination of iodine in foods and other biological materials. Samples are encapsulated in boron nitride containers with wall thickness of several millimeters. The boron serves to substantially absorb thermal neutrons but allows epithermal neutrons to activate the sample. Iodine is an attractive element to determine by ENAA

1986-01-01

295

Determination of pesticide residues in local vegetables by means of neutron activation technique.  

National Technical Information Service (NTIS)

Analytical methods based on neutron activation have been developed for studying pesticides residues of bromine, arsenic and mercury in local vegetables and fruits. The concentration of bromine, arsenic and mercury in samples are enriched prior to neutron ...

S. Mongkolphantha P. Karasuddhi P. Yamkate N. Serichareonsatit

1975-01-01

296

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

NASA Astrophysics Data System (ADS)

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. The experimentally determined 232Th(n, ?) and 232Th(n, 2n) reaction cross-sections were compared with the evaluated data of ENDF/B-VII, JENDL-4.0 and JEFF-3.1 and were found to be in good agreement. The present data along with literature data in a wide range of neutron energies were interpreted in terms of competition between different reaction channels including fission. The 232Th(n, ?) and 232Th(n, 2n) reaction cross-sections were also calculated theoretically using the TALYS 1.2 computer code and were found to be slightly higher than the experimental data.

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

2011-04-01

297

Provenience studies using neutron activation analysis: the role of standardization  

SciTech Connect

This paper covers the historical background of chemical analysis of archaeological artifacts which dates back to 1790 to the first application of neutron activation analysis to archaeological ceramics and goes on to elaborate on the present day status of neutron activation analysis in provenience studies, and the role of standardization. In principle, the concentrations of elements in a neutron-activated specimen can be calculated from an exact knowledge of neutron flux, its intensity, duration and spectral (energy) distribution, plus an exact gamma ray count calibrated for efficiency, corrected for branching rates, etc. However, in practice it is far easier to compare one's unknown to a standard of known or assumed composition. The practice has been for different laboratories to use different standards. With analyses being run in the thousands throughout the world, a great benefit would be derived if analyses could be exchanged among all users and/or generators of data. The emphasis of this paper is on interlaboratory comparability of ceramic data; how far are we from it, what has been proposed in the past to achieve this goal, and what is being proposed. All of this may be summarized under the general heading of Analytical Quality Control - i.e., how to achieve precise and accurate analysis. The author proposes that anyone wishing to analyze archaeological ceramics should simply use his own standard, but attempt to calibrate that standard as nearly as possible to absolute (i.e., accurate) concentration values. The relationship of Analytical Quality Control to provenience location is also examined.

Harbottle, G

1980-01-01

298

Gadolinium-neutron-activation determination with a Pu-Be source  

Microsoft Academic Search

A nondestructive neutron activation method for determining gadolinium content for reactor construction materials was developed. The method uses a Pu-Be neutron source capable of giving 10⁸ neutrons per second and the neutron reaction with a ¹⁶°Gd target. To determine the flux attenuation, induced-activity distributions were measured along the radius with artificial compacts of AlâOâ + GdâOâ specimens with varying gadolinium

A. E. Konyaev; V. F. Kositsyn; A. B. Medvedev; V. S. Rudenko

1988-01-01

299

Neutron Activation Analysis of Trace Elements in Lava  

NASA Astrophysics Data System (ADS)

The elemental compositions of lavas vary with the locations of the volcanoes from which they emerged. We have used neutron activation analysis to measure the abundances of approximately 32 different elements in lava samples collected from three different Hawaiian islands and from the summit of Mt. Kilimanjaro. Two different neutron irradiations were performed at the McClellan Nuclear Radiation Center to optimize our sensitivities to both short- and long-lived radioisotopes. Gamma-ray counting was done at McClellan, UC Berkeley, and LBNL using large-volume high-purity Ge detectors. Results from the measurements will be presented and comparisons will be made between the trace-element compositions of the lavas from these different sites.

Meyer, R. E.; Sabella, J. L.; Thomas, K. J.; Norman, E. B.; Guillamon, P. V.; Goldman, I. D.; Smith, A. R.

2012-10-01

300

?? coincidence spectrometer for instrumental neutron-activation analysis  

NASA Astrophysics Data System (ADS)

Neutron-activation analysis (NAA) is an important technique for the accurate and precise determination of trace and ultra-trace elemental compositions. The application of ?? coincidence counting to NAA in order to enhance specificity was first explored over 40 years ago but has not evolved into a regularly used technique. A ?? coincidence spectrometer has been constructed at the National Institute of Standards and Technology, using two HPGe ?-ray detectors and an all-digital data-acquisition system, for the purpose of exploring coincidence NAA and its value in characterizing reference materials. This paper describes the initial evaluation of the quantitative precision of coincidence counting versus singles spectrometry, based upon a sample of neutron-irradiated bovine liver material.

Tomlin, B. E.; Zeisler, R.; Lindstrom, R. M.

2008-05-01

301

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

302

The THz fingerprint spectra of the active ingredients of a TCM medicine: Herba Ephedrae  

NASA Astrophysics Data System (ADS)

In this paper, THz-TDS has been used to measure the spectral properties of two active ingredients of Herba Ephedrae: ephedrine and pseudoephedrine, which exist in hydrochloride salts. The THz spectra of the sole-ingredient, twoingredient and three-ingredient compounds are studied. We obtained the finger-print spectra of the net active ingredients of the medicine, and also measured the mixtures of by two or three active ingredients at the different ratios. At the same time, theoretical analysis and quantitative analysis is applied to foretell the different THz spectra, identify the ingredients and infer the contents of principal components in samples. The THz spectroscopy is a potential and promising technique in evaluating and inspecting the quality of the drugs in the TCM field.

Ma, Shihua; Liu, Guifeng; Zhang, Peng; Song, Xiyu; Ji, Te; Wang, Wenfeng

2008-12-01

303

Comparison between calculation and measured data on secondary neutron energy spectra by heavy ion reactions from different thick targets.  

PubMed

Measured neutron energy fluences from high-energy heavy ion reactions through targets several centimeters to several hundred centimeters thick were compared with calculations made using the recently developed general-purpose particle and heavy ion transport code system (PHITS). It was confirmed that the PHITS represented neutron production by heavy ion reactions and neutron transport in thick shielding with good overall accuracy. PMID:16604717

Iwase, H; Wiegel, B; Fehrenbacher, G; Schardt, D; Nakamura, T; Niita, K; Radon, T

2005-01-01

304

Influence of Bonner sphere response functions above 20 MeV on unfolded neutron spectra and doses  

Microsoft Academic Search

Monte Carlo (MC) codes for neutron transport calculations such as MCNP, MCNPX, FLUKA, PHITS, and GEANT4, crucially rely on cross sections that describe the interaction of neutrons with nuclei. For neutron energies below 20 MeV, evaluated cross sections are available that are validated against experimental data. In contrast, for high energies (above 20 MeV) experimental data are scarce and, for this reason,

C. Pioch; V. Mares; W. Rühm

2010-01-01

305

Prompt gamma activation analysis of boron in reference materials using diffracted polychromatic neutron beam  

NASA Astrophysics Data System (ADS)

Boron concentrations were analyzed for standard reference materials by prompt gamma activation analysis (PGAA). The measurements were performed at the SNU-KAERI PGAA facility installed at Hanaro, the research reactor of Korea Atomic Energy Research Institute (KAERI). The facility uses a diffracted polychromatic beam with a neutron flux of 7.9×107 n/cm2s. Elemental sensitivity for boron was calibrated from the prompt gamma-ray spectra of boric acid samples containing 2-45 ?g boron. The sensitivity of 2131 cps/mg-B was obtained from the linearity of the boron peak count rate versus the boron mass. The detection limit for boron was estimated to be 67 ng from an empty sample bag spectrum for a counting time of 10,000 s. The measured boron concentrations for standard reference materials showed good consistency with the certified or information values.

Byun, S. H.; Sun, G. M.; Choi, H. D.

2004-01-01

306

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

307

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

308

Detection and depth profiling of hazardous elements using N-SCAN prompt gamma neutron activation analysis  

Microsoft Academic Search

A low-background method of prompt gamma neutron activation analysis (PGNAA) has been developed and demonstrated. This method employs a pulsed electronic neutron generator, a high resolution, high purity germanium detector, and microsecond coordination of neutron pulsing and gamma detection through a computer-controlled acquisition interface module. The system has been used to detect trace amounts of hazardous elements in concretes and

F. H. Ruddy; T. V. Congedo; A. R. Dulloo

1995-01-01

309

MFE/ACT: a TRS-80 code for calculating neutron activation  

SciTech Connect

The MFE/ACT code, written to run on the TRS-80, can be used to calculate the neutron activation of materials used in fission and fusion reactors. Input data include the specific isotopes to be calculated, the neutron fluxes, the neutron cross sections, and the nuclear decay half-lives.

Dorn, D.W.

1982-10-01

310

Thermal Neutron Spect+a Near Absorbers.  

National Technical Information Service (NTIS)

The perturbation in a thermal neutron spectrum near an absorber immersed in a moderator has been studied using activation techniques. The results show two separate effects for pure thermal spectra, a 'transmission hardening' depending on the energy variat...

C. B. Bigham

1964-01-01

311

The investigation of fast neutron Threshold Activation Detectors (TAD)  

Microsoft Academic Search

The detection of fast neutrons is usually done by liquid hydrogenous organic scintillators, where the separation between the ever present gamma rays and neutrons is achieved by the pulse shape discrimination (PSD). In many practical situation the detection of fast neutrons has to be carried out while the intense source (be it neutrons, gamma rays or x-rays) that creates these

T Gozani; M J King; J Stevenson

2012-01-01

312

Active detection of shielded SNM with 60keV neutrons  

Microsoft Academic Search

Fissile materials, e.g. ²³U and ²³Pu, 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

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

2008-01-01

313

Active Detection of Shielded SNM With 60keV Neutrons  

Microsoft Academic Search

Fissile materials, e.g., 235U and 239Pu, 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 (E > 1 MeV) fission neutrons. One promising mode of operation subjects the object to a beam of low-energy (E < 1 MeV) neutrons, generated by a proton beam impinging on

Christian A. Hagmann; Daniel D. Dietrich; James M. Hall; Phillip L. Kerr; Leslie F. Nakae; Robert J. Newby; Mark S. Rowland; Neal J. Snyderman; Wolfgang Stoeffl

2009-01-01

314

Neutron spectrometry using artificial neural networks  

Microsoft Academic Search

An artificial neural network has been designed to obtain neutron spectra from Bonner spheres spectrometer count rates. The neural network was trained using 129 neutron spectra. These include spectra from isotopic neutron sources; reference and operational spectra from accelerators and nuclear reactors, spectra based on mathematical functions as well as few energy groups and monoenergetic spectra. The spectra were transformed

Héctor René Vega-Carrillo; Víctor Martín Hernández-Dávila; Eduardo Manzanares-Acuña; Gema A. Mercado Sánchez; Maria Pilar Iñiguez de la Torre; Raquel Barquero; Francisco Palacios; Roberto Méndez Villafañe; Tarcicio Arteaga Arteaga; José Manuel Ortiz Rodriguez

2006-01-01

315

Average cross sections for Pu-?-Be neutrons: Low-energy neutrons from ?-n sources  

Microsoft Academic Search

Average activation cross sections for a number of elements were determined using unmoderated neutrons from Pu-Be and Po-Be\\u000a sources. Applying threshold detectors it was found that 10% of Pu-Be neutrons are emitted in the energy interval 10–100 keV.\\u000a Neutron spectra from Pu-Be13 sources of different dimensions were the same within the interval 0.5–5 Ci; the majority of neutrons below 2

G. Pet?; J. Csikai; G. M. Shuriet; I. Józsa; V. Asztalos

1973-01-01

316

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...

317

Collisional Activation Mass Spectra of M(1-.) Ions of Azo Dyes Containing 2-Naphthol.  

National Technical Information Service (NTIS)

Collisionally activated decomposition mass spectra of M- ions of azo dyes are presented. The compounds are of general structure Ar(1)-N=N-Ar(2), where Ar(1) is substituted phenyl and Ar(2) is 2-naphthol. Characteristic fragment ions observed include m/z 1...

W. C. Brumley G. M. Brilis R. J. Calvey J. A. Sphon

1989-01-01

318

On the parameterization of activation spectra from cloud condensation nuclei microphysical properties  

Microsoft Academic Search

A simple parametric relationship is established between factors describing the shape of cloud condensation nuclei (CCN) activation spectra and observable properties of the aerosol population they grow on (size distribution and solubility). This is done independently for maritime and continental aerosol types because of their very different characteristics. The data used for the multiple statistical adjustments in the procedure described

Jean-Martial Cohard; Jean-Pierre Pinty; Karsten Suhre

2000-01-01

319

Enzyme hydration, activity and flexibility : A neutron scattering approach  

SciTech Connect

Recent measurements have demonstrated enzyme activity at hydrations as low as 3%. The question of whether the hydration-induced enzyme flexibility is important for activity is addressed by performing picosecond dynamic neutron scattering experiments on pig liver esterase powders at various temperatures as well as solutions. At all temperatures and hydrations investigated here, significant quasielastic scattering intensity is found in the protein, indicating the presence of anharmonic, diffusive motion. As the hydration increases a temperature-dependent dynamical transition appears and strengthens involving additional diffusive motion. At low temperature, increasing hydration resulted in lower flexibility of the enzyme. At higher temperatures, systems containing sufficient number of water molecules interacting with the protein exhibit increased flexibility. The implication of these results is that, although the additional hydration-induced diffusive motion and flexibility at high temperatures in the enzyme detected here may be related to increased activity, they are not required for the enzyme to function.

Kurkal-Siebert, V [University of Heidelberg; Finney, J.L. [University College, London; Daniel, R. M. [University of Waikato, New Zealand; Smith, Jeremy C [ORNL

2006-01-01

320

Classification of the low-energy neutron spectra behind the shield of the accelerator of the institute of high-energy physics  

SciTech Connect

The investigation and classification of neutron energy spectra is one of the most complicated and important research problems. In order to eliminate the influence of possible systematic errors upon the classification, one must make a representative sampling of data which were measured with a single technique within particular energy limits. For this purpose, on the 70-GeV proton accelerator of the Institute of High-Energy Physics, there were measured more than 100 spectra behind the shield at points which can be characterized by variations of well distinguishable parameters such as thickness and composition of the biological shield, inhomogeneities (passageways and labyrinths) in the shield, the source-shield-detector geometry, and the specific conditions of accelerator operation.

Belogorlov, E.A.; Britvich, G.I.; Krupnyi, G.I.; Lebedev, V.N.; Lukanin, V.S.; Makagonov, A.V.; Peleshko, V.N.; Rastsvetalov, Ya.N.

1987-09-01

321

Rare-earth elements in Egyptian granite by instrumental neutron activation analysis.  

PubMed

The mobilization of rare-earth elements (REEs) in the environment requires monitoring of these elements in environmental matrices, in which they are mainly present at trace levels. The similarity in REEs chemical behavior makes the separate determination of each element by chemical methods difficult; instrumental neutron activation analysis (INAA), based on nuclear properties of the elements to be determined, is a method of choice in trace analysis of REEs and related elements. Therefore, INAA was applied as a sensitive nondestructive analytical tool for the determination of REEs to find out what information could be obtained about the REEs of some Egyptian granite collected from four locations in Aswan area in south Egypt as follows wadi El-Allaqi, El-Shelal, Gabel Ibrahim Pasha and from Sehyel Island and to estimate the accuracy, reproducibility and detection limit of NAA method in case of the given samples. The samples were properly prepared together with standards and simultaneously irradiated in a neutron flux of 7 x 10(11)n/cm(2)s in the TRIGA Mainz research reactor facilities. The following elements have been determined: La, Ce, Nd, Sm, Eu, Yb and Lu. The gamma spectra was collected by HPGe detector and the analysis was done by means of computerized multichannel analyzer. The X-ray fluorescence (XRF) was also used. PMID:17208446

El-Taher, A

2007-01-08

322

Influence of Neutron Spectra and Fluence Response Data on the Determination of Dose Equivalent with Bonner Spheres.  

National Technical Information Service (NTIS)

A formalism is presented which allows a concise interpretation of measurements with Bonner spheres in order to determine dose equivalent. Five sets of response functions given in the literature are presented and intercompared. A set of nine neutron spectr...

A. V. Alevra B. R. L. Siebert

1986-01-01

323

Development of a neutron-activated concrete powder reference material.  

PubMed

In this paper, the development of a neutron-activated concrete powder reference material is described. The material originated from core samples taken from a concrete bioshield of a decommissioned nuclear reactor which ceased operation almost 30 years ago after approximately 20 years of operation. The assigned values, which were in the Bq g(-1) range, for the radionuclides in the material were determined by a 'consensus' method from measurements made by 33 organisations from 15 countries. The measurements were made within a wider test exercise (the NPL Environmental Radioactivity Proficiency Test Exercise 2008). Assigned specific activity values were obtained for (60)Co, (133)Ba, (152)Eu and (154)Eu and indicative values were obtained for (3)H (total), (3)H (leachable), (14)C, (40)K, (55)Fe and (63)Ni. PMID:20022254

Harms, Arvic; Gilligan, Chris

2009-11-18

324

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

325

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

326

Neutron threshold activation detectors (TAD) for the detection of fissions  

Microsoft Academic Search

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (?3 vs. ?0.01) that are commonly used as indicators for the presence of fissionable

Tsahi Gozani; John Stevenson; Michael J. King

2011-01-01

327

The Monte Carlo code CEARCPG for coincidence prompt gamma-ray neutron activation analysis  

Microsoft Academic Search

Prompt gamma-ray neutron activation analysis (PGNAA) is widely used to determine the elemental composition of bulk samples. The detection sensitivities of PGNAA are often restricted by the inherent poor signal-to-noise ratio (SNR). There are many sources of noise (background) including the natural background, neutron activation of the detector, gamma-rays associated with the neutron source and prompt gamma-rays from the structural

Xiaogang Han; Robin P. Gardner

2007-01-01

328

Local Luminous Infrared Galaxies. II. Active Galactic Nucleus Activity from Spitzer/Infrared Spectrograph Spectra  

NASA Astrophysics Data System (ADS)

We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 ?m) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L IR = 1011-1012 L ?). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 ?m spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is ~62%. The derived AGN bolometric luminosities are in the range L bol(AGN) = (0.4-50) × 1043 erg s-1. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L bol[AGN]/L IR <= 0.05. Only ~= 8% of local LIRGs have a significant AGN bolometric contribution L bol[AGN]/L IR > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L IR = 1012-1013 L ?), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for 5%^{+8%}_{-3%} of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of ?AGN IR = 3 × 105 L ? Mpc-3 in LIRGs. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.

Alonso-Herrero, Almudena; Pereira-Santaella, Miguel; Rieke, George H.; Rigopoulou, Dimitra

2012-01-01

329

LOCAL LUMINOUS INFRARED GALAXIES. II. ACTIVE GALACTIC NUCLEUS ACTIVITY FROM SPITZER/INFRARED SPECTROGRAPH SPECTRA  

SciTech Connect

We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 {mu}m) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L{sub IR} = 10{sup 11}-10{sup 12} L{sub Sun }). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 {mu}m spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is {approx}62%. The derived AGN bolometric luminosities are in the range L{sub bol}(AGN) = (0.4-50) Multiplication-Sign 10{sup 43} erg s{sup -1}. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L{sub bol}[AGN]/L{sub IR} {<=} 0.05. Only {approx_equal} 8% of local LIRGs have a significant AGN bolometric contribution L{sub bol}[AGN]/L{sub IR} > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L{sub IR} = 10{sup 12}-10{sup 13} L{sub Sun }), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for 5%{sub -3%}{sup +8%} of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of {Omega}{sup AGN}{sub IR} = 3 Multiplication-Sign 10{sup 5} L{sub Sun} Mpc{sup -3} in LIRGs.

Alonso-Herrero, Almudena; Pereira-Santaella, Miguel [Centro de Astrobiologia, INTA-CSIC, E-28850 Torrejon de Ardoz, Madrid (Spain); Rieke, George H. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Rigopoulou, Dimitra [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom)

2012-01-01

330

Suzaku and BeppoSAX X-ray Spectra of the Persistently Accreting Neutron-star Binary 4U 1705-44  

NASA Astrophysics Data System (ADS)

We present an analysis of the broadband spectra of 4U 1705-44 obtained with Suzaku in 2006-2008 and by BeppoSAX in 2000. The source exhibits two distinct states: the hard state shows emission from 1 to 150 keV, while the soft state is mostly confined to be <40 keV. We model soft-state continuum spectra with two thermal components, one of which is a multicolor accretion disk and the other is a single-temperature blackbody (BB) to describe the boundary layer, with additional weak Comptonization represented by either a simple power law or the SIMPL model by Steiner et al. The hard-state continuum spectra are modeled by a single-temperature BB for the boundary layer plus strong Comptonization, modeled by a cutoff power law. While we are unable to draw firm conclusions about the physical properties of the disk in the hard state, the accretion disk in the soft state appears to approximately follow L vprop T 3.2. The deviation from L vprop T 4, as expected from a constant inner disk radius, might be caused by a luminosity-dependent spectral hardening factor and/or real changes of the inner disk radius in some part of the soft state. The boundary layer apparent emission area is roughly constant from the hard to the soft states, with a value of about 1/11 of the neutron star surface. The magnetic field on the surface of the neutron star in 4U 1705-44 is estimated to be less than about 1.9 × 108 G, assuming that the disk is truncated by the innermost stable circular orbit or by the neutron star surface. Broad relativistic Fe lines are detected in most spectra and are modeled with the diskline model. The strength of the Fe lines is found to correlate well with the boundary layer emission in the soft state. In the hard state, the Fe lines are probably due to illumination of the accretion disk by the strong Comptonization emission.

Lin, Dacheng; Remillard, Ronald A.; Homan, Jeroen

2010-08-01

331

SUZAKU AND BeppoSAX X-RAY SPECTRA OF THE PERSISTENTLY ACCRETING NEUTRON-STAR BINARY 4U 1705-44  

SciTech Connect

We present an analysis of the broadband spectra of 4U 1705-44 obtained with Suzaku in 2006-2008 and by BeppoSAX in 2000. The source exhibits two distinct states: the hard state shows emission from 1 to 150 keV, while the soft state is mostly confined to be <40 keV. We model soft-state continuum spectra with two thermal components, one of which is a multicolor accretion disk and the other is a single-temperature blackbody (BB) to describe the boundary layer, with additional weak Comptonization represented by either a simple power law or the SIMPL model by Steiner et al. The hard-state continuum spectra are modeled by a single-temperature BB for the boundary layer plus strong Comptonization, modeled by a cutoff power law. While we are unable to draw firm conclusions about the physical properties of the disk in the hard state, the accretion disk in the soft state appears to approximately follow L {proportional_to} T {sup 3.2}. The deviation from L {proportional_to} T{sup 4}, as expected from a constant inner disk radius, might be caused by a luminosity-dependent spectral hardening factor and/or real changes of the inner disk radius in some part of the soft state. The boundary layer apparent emission area is roughly constant from the hard to the soft states, with a value of about 1/11 of the neutron star surface. The magnetic field on the surface of the neutron star in 4U 1705-44 is estimated to be less than about 1.9 x 10{sup 8} G, assuming that the disk is truncated by the innermost stable circular orbit or by the neutron star surface. Broad relativistic Fe lines are detected in most spectra and are modeled with the diskline model. The strength of the Fe lines is found to correlate well with the boundary layer emission in the soft state. In the hard state, the Fe lines are probably due to illumination of the accretion disk by the strong Comptonization emission.

Lin Dacheng; Remillard, Ronald A.; Homan, Jeroen, E-mail: Dacheng.Lin@cesr.f [MIT Kavli Institute for Astrophysics and Space Research, MIT, 70 Vassar Street, Cambridge, MA 02139-4307 (United States)

2010-08-20

332

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

333

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

334

Neutron Activation Analysis of Soil Samples from Different Parts of Abuja Metropolis  

Microsoft Academic Search

2 Abstract: A study was carried out on the concentrations of constituent (major, minor and trace) elements present in soil samples collected from different parts of Abuja Metropolis and their effect on the surrounding. In carrying out the analysis, the best and most convenient method being the Instrumental Neutron Activation Analysis (INAA) otherwise known as Non-Destructive Neutron Activation Analysis (NDNAA)

B. E. Kogo; E. N. Gajere; J. K. Ogunmola; J. O. Ogbole

335

Neutron Activation Analysis of Leaf Samples from Different Parts of Abuja Metropolis  

Microsoft Academic Search

2 Abstract: A study is carried out on the concentrations of constituent (major, minor and trace) elements present in Leaf Samples and their effects on the populations and surrounding of Abuja Metropolis. In carrying out the analysis, the best and most convenient method being the Instrumental Neutron Activation Analysis (INAA) otherwise known as Non-Destructi ve Neutron Activation Analysis (NDNAA) was

B. E. Kogo; E. N. Gajere; J. K. Ogunmola; J. O. Ogbole

336

NOTE: Total body-calcium measurements: comparison of two delayed-gamma neutron activation facilities  

Microsoft Academic Search

This study compares two independently calibrated delayed-gamma neutron activation (DGNA) facilities, one at the Brookhaven National Laboratory (BNL), Upton, New York, and the other at the Children's Nutrition Research Center (CNRC), Houston, Texas that measure total body calcium (TBCa). A set of BNL phantoms was sent to CNRC for neutron activation analysis, and a set of CNRC phantoms was measured

R. Ma; K. J. Ellis; S. Yasumura; R. J. Shypailo; R. N. Pierson Jr.

1999-01-01

337

The distribution of some trace elements in iron meteorites, as determined by neutron activation  

Microsoft Academic Search

The ten trace elements germanium, arsenic, antimony, copper, chromium molybdenum, silver, indium, zinc and palladium have been determined in sixty-seven different meteorites, using neutron activation and radiochemical separations. In addition the meteorites have been analysed for gallium using either neutron activation or colorimetric methods. The sulphur content of twenty-five of the meteorites has also been measured, using an evolution and

A. A. Smales; D. Mapper; K. F. Fouché

1967-01-01

338

Use of coincident and non-coincident gamma-rays in Compton suppression neutron activation analysis  

Microsoft Academic Search

Summary  In the last decade Compton suppressed neutron activation analysis has had increasing popularity as a powerful method to significantly lower backgrounds and reduce overlapping peaks caused by spectral or nuclear interferences. We give a detailed descriptive evaluation of the unique features of this technique and its usefulness in many areas of research employing non-destructive neutron activation analysis.

S. Landsberger; S. R. Biegalski; D. J. O’Kelly; M. S. Basunia

2005-01-01

339

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

340

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

Microsoft Academic Search

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

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

1990-01-01

341

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

342

Neutron activation analysis: A primary method of measurement  

NASA Astrophysics Data System (ADS)

Neutron activation analysis (NAA), based on the comparator method, has the potential to fulfill the requirements of a primary ratio method as defined in 1998 by the Comité Consultatif pour la Quantité de Matière — Métrologie en Chimie (CCQM, Consultative Committee on Amount of Substance — Metrology in Chemistry). This thesis is evidenced in this paper in three chapters by: demonstration that the method is fully physically and chemically understood; that a measurement equation can be written down in which the values of all parameters have dimensions in SI units and thus having the potential for metrological traceability to these units; that all contributions to uncertainty of measurement can be quantitatively evaluated, underpinning the metrological traceability; and that the performance of NAA in CCQM key-comparisons of trace elements in complex matrices between 2000 and 2007 is similar to the performance of Isotope Dilution Mass Spectrometry (IDMS), which had been formerly designated by the CCQM as a primary ratio method.

Greenberg, Robert R.; Bode, Peter; De Nadai Fernandes, Elisabete A.

2011-03-01

343

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

344

Neutron activation analysis detection limits using {sup 252}Cf sources  

SciTech Connect

The Savannah River Technology Center (SRTC) developed a neutron activation analysis (NAA) facility several decades ago using low-flux {sup 252}Cf neutron sources. Through this time, the facility has addressed areas of applied interest in managing the Savannah River Site (SRS). Some applications are unique because of the site's operating history and its chemical-processing facilities. Because sensitivity needs for many applications are not severe, they can be accomplished using an {approximately}6-mg {sup 252}Cf NAA facility. The SRTC {sup 252}Cf facility continues to support applied research programs at SRTC as well as other SRS programs for environmental and waste management customers. Samples analyzed by NAA include organic compounds, metal alloys, sediments, site process solutions, and many other materials. Numerous radiochemical analyses also rely on the facility for production of short-lived tracers, yielding by activation of carriers and small-scale isotope production for separation methods testing. These applications are more fully reviewed in Ref. 1. Although the flux [{approximately}2 x 10{sup 7} n/cm{sup 2}{center_dot}s] is low relative to reactor facilities, more than 40 elements can be detected at low and sub-part-per-million levels. Detection limits provided by the facility are adequate for many analytical projects. Other multielement analysis methods, particularly inductively coupled plasma atomic emission and inductively coupled plasma mass spectrometry, can now provide sensitivities on dissolved samples that are often better than those available by NAA using low-flux isotopic sources. Because NAA allows analysis of bulk samples, (a) it is a more cost-effective choice when its sensitivity is adequate than methods that require digestion and (b) it eliminates uncertainties that can be introduced by digestion processes.

DiPrete, D.P.; Sigg, R.A.

2000-07-01

345

A kinematically beamed, low energy pulsed neutron source for active interrogation  

NASA Astrophysics Data System (ADS)

We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of special nuclear materials (SNM) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals: (1) energy discrimination allows us to measure the prompt fast fission neutrons produced while the interrogation beam is on; (2) neutrons with an energy of approximately 60 100 keV do not fission 238U and Thorium, but penetrate bulk material nearly as far as high energy neutrons do and (3) below about 100 keV neutrons lose their energy by kinematical collisions rather than via the nuclear (n, 2n) or (n, n?) processes thus further simplifying the prompt neutron induced background. 60 keV neutrons create a low radiation dose and readily thermal capture in normal materials, thus providing a clean spectroscopic signature of the intervening materials. The kinematically beamed source also eliminates the need for heavy backward and sideway neutron shielding. We have designed and built a very compact pulsed neutron source, based on an RFQ proton accelerator and a lithium target. We are developing fast neutron detectors that are nearly insensitive to the ever-present thermal neutron and neutron capture induced gamma ray background. The detection of only a few high energy fission neutrons in time correlation with the linac pulse will be a clear indication of the presence of SNM.

Dietrich, Dan; Hagmann, Chris; Kerr, Phil; Nakae, Les; Rowland, Mark; Snyderman, Neal; Stoeffl, Wolfgang; Hamm, Robert

2005-12-01

346

REACTIVITY COEFFICIENTS AND NEUTRON SPECTRA IN A CLUSTERED, SLIGHTLY ENRICHED UOâ-DâO TWO-REGION LATTICE  

Microsoft Academic Search

A description is given of the facility used for the Carolinas Virginia ; Tube Reactor critical experiments. A fullsize core mockup was used. ; Experimental techniques are given for measurement of void and temperature ; coefficients of reactivity and results are compared with predictions. Kinetics ; and measurements associated with neutrons are included. (J.R.D.);

J. Jedruch; G. N. Hamilton

1962-01-01

347

Nondestructive control of chemical weapons combining neutron-activation analysis and neutron-radiography techniques  

NASA Astrophysics Data System (ADS)

A project of a transportable neutron system has been designed for nondestructive detection of weapon materials such as chemical agents or explosives. The system combines imaging and identifying techniques, and uses a sealed tube neutron generator GENIE 46. The neutron emitting module is embedded in a moderator/collimator. The resulting mixed 14 MeV and thermal neutron beam allows the user to perform neutron radiography and gamma-ray spectroscopy. Substances to be detected are imaged in a first step and then identified by comparing relative spectral line intensities with those of reference materials. The moderator provides a first level protection against radiation to the operators. This project includes only industrial sub assemblies, transportable by truck to be used in open area.

Bach, Pierre; Cluzeau, S.; Le Tourneur, P.; Jaureguy, J. C.; Guir, F.

1995-03-01

348

Neutron measurements in a Varian 2,100C LINAC facility using a Bonner sphere system based on passive gold activation detectors.  

PubMed

The use of high-energy linear electron accelerators (LINACs) for medical cancer treatments is widespread on an international scale. The associated bremsstrahlung X rays may produce neutrons as a result of subsequent photonuclear reactions with the different materials constituting the accelerator head. The generated neutron field is highly variable and depends strongly on the beam energy, on the accelerator shielding, on the flattering filter as well as on the movable collimators (jaws) design and on the irradiation field geometry. An estimate of this photoneutron component is, thus, of practical interest to quantify the radiological risk for the working staff and patients. Due to high frequency electromagnetic fields, and also to the presence of abundant leaked and scattered photons in these installations, measurements of the corresponding neutron fields by active dosemeters are extremely difficult. A modified version of the Bonner sphere system, based on passive gold activation detectors, has been used to perform neutron measurements at two points in a Varian 2,100C LINAC facility. A home-made unfolding procedure (CDM) has been utilised to determine the neutron spectra present at the measurement points. Results indicate that the giant dipole resonance process is the most adequate model to explain neutron production in the LINAC and that a thermal component is present at the measurement points. PMID:17525060

Fernández, F; Domingo, C; Amgarou, K; Castelo, J; Bouassoule, T; Garcia, M J; Luguera, E

2007-05-24

349

Active Neutron Interrogation of Non-Radiological Materials with NMIS  

SciTech Connect

The Nuclear Materials Identification System (NMIS) at Oak Ridge National Laboratory (ORNL), although primarily designed for analyzing special nuclear material, is capable of identifying nonradiological materials with a wide range of measurement techniques. This report demonstrates four different measurement methods, complementary to fast-neutron imaging, which can be used for material identification: DT transmission, DT scattering, californium transmission, and active time-tagged gamma spectroscopy. Each of the four techniques was used to evaluate how these methods can be used to identify four materials: aluminum, polyethylene, graphite, and G-10 epoxy. While such measurements have been performed individually in the past, in this project, all four measurements were performed on the same set of materials. The results of these measurements agree well with predicted results. In particular, the results of the active gamma spectroscopy measurements demonstrate the technique's applicability in a future version of NMIS which will incorporate passive and active gamma-ray spectroscopy. This system, designated as a fieldable NMIS (FNMIS), is under development by the US Department of Energy Office of Nuclear Verification.

Walker, Mark E [ORNL; Mihalczo, John T [ORNL

2012-02-01

350

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

351

Coronal Radio Sounding Experiments with Mars Express: Scintillation Spectra during Low Solar Activity  

SciTech Connect

Coronal radio sounding observations were carried out with the radio science experiment MaRS on the ESA spacecraft Mars Express during the period from 25 August to 22 October 2004. Differential frequency and log-amplitude fluctuations of the dual-frequency signals were recorded during a period of low solar activity. The data are applicable to low heliographic latitudes, i.e. to slow solar wind. The mean frequency fluctuation and power law index of the frequency fluctuation temporal spectra are determined as a function of heliocentric distance. The radial dependence of the frequency fluctuation spectral index alpha reflects the previously documented flattening of the scintillation power spectra in the solar wind acceleration region. Temporal spectra of S-band and X-band normalized log-amplitude fluctuations were investigated over the range of fluctuation frequencies 0.01 Hzactivity. Ranging measurements are presented and compared with frequency and log-amplitude scintillation data. Evidence for a weak increase in the fractional electron density turbulence level is obtained in the range 10-40 solar radii.

Efimov, A. I.; Lukanina, L. A.; Samoznaev, L. N.; Rudash, V. K. [Kotel'nikov Inst. Radio Engg. and Electronics, Russian Acad. Science, 125009 Moscow (Russian Federation); Chashei, I. V. [Lebedev Phys. Inst., Russian Acad. Science, 117924 Moscow (Russian Federation); Bird, M. K. [Argelander-Institut fuer Astronomie, Univ. Bonn, 53121 Bonn (Germany); Paetzold, M.; Tellmann, S. [Rheinisches Institut fuer Umweltforschung, Univ. Koeln, 50931 Koeln (Germany)

2010-03-25

352

Facilities of ORNL (Oak Ridge National Laboratory) for neutron activation analysis and gamma ray spectroscopy  

Microsoft Academic Search

A second pneumatic tube that was recently installed in the High Flux Isotope Reactor for neutron activation analysis is described. Although not yet tested, the system is expected to have a thermal neutron flux of about 1.5 à 10¹⁴ cm⁻² s⁻¹. A delayed neutron counter is an integral part of the pneumatic tube, and all of the hardware is present

F. F. Dyer; J. F. Emery; L. Robinson; N. A. Teasley

1989-01-01

353

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

354

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

355

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

Microsoft Academic Search

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. Spent

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

1981-01-01

356

Determination of palladium in gasoline by neutron activation analysis and automated column extraction  

Microsoft Academic Search

Palladium in gasoline was determined by means of neutron activation analysis (NAA) and selective sorbent extraction. Unleaded\\u000a gasoline consistent with DIN EN 228, RON 95 was irradiated at a thermal neutron flux of ?th = 1.68 · 1013s–1cm–2 and an epithermal neutron flux of 3.32 · 1011s–1cm–2 for tirr = 12 h. The irradiated gasoline was digested with nitric acid

Michael Schwarzer; Michael Schuster; Roger von Hentig

2000-01-01

357

Study on air pollution monitoring in Korea using instrumental neutron activation analysis  

Microsoft Academic Search

Trace elements in airborne particulate matter collected monthly at suburban and rural areas in Korea were analyzed by instrumental neutron activation analysis (INAA). Neutron irradiation of the samples was done at the irradiation hole (neutron flux 1·1013 n·cm–2·s–1) of the TRIGA Mark-III Research Reactor in the Korea Atomic Energy Research Institute. For the verification of the analytical technique, two reference

Y. S. Chung; Y. J. Chung; E. S. Jeong; S. Y. Cho

1997-01-01

358

Coincidence and anti-coincidence measurements in prompt gamma neutron activation analysis with pulsed cold neutron beams  

Microsoft Academic Search

A novel approach is implemented to alleviate some persistent problems in neutron capture prompt gamma activation analysis (PGAA). Detection sensitivities of PGAA are often restricted by the following factors: poor signal to noise ratios, interferences from background signals, and, in some cases, overlapping energy lines from different origins, namely ultra short-lived decay lines interfering with prompt decay. Timing the gamma-ray

R. Zeisler; G. P. Lamaze; H. H. Chen-Mayer

2001-01-01

359

Neutron-activation study of figurines, pottery, and workshop materials from the Athenian Agora, Greece. [Neutron reactions; France, Israel, Cyprus  

Microsoft Academic Search

Ceramic specimens from the excavations of the Agora of ancient Athens, Greece, including material from factories, i.e., trial firing pieces, pottery and figurine wasters, datable to the Protogeometric, Subgeometric, and Classical Periods, and stylistically related figurines and pottery were analyzed by neutron activation. The factory material from the three distinct chronological periods separated respectively into three significantly different compositional groups,

D. Fillieres; G. Harbottle; E. V. Sayre

1983-01-01

360

Measurements of activation induced by environmental neutrons using ultra low-level gamma-ray spectrometry.  

PubMed

The flux of environmental neutrons is being studied by activation of metal discs of selected elements. Near the earth's surface the total neutron flux is in the order of 10(-2) cm(-2)s(-1), which gives induced activities of a few mBq in the discs. Initial results from this technique, involving activation at ground level for several materials (W, Au, Ta, In, Re, Sm, Dy and Mn) and ultra low-level gamma-ray spectrometry in an underground laboratory located at 500 m.w.e., are presented. Diffusion of environmental neutrons in water is also measured by activation of gold at different depths. PMID:10724430

Martínez Canet, M J; Hult, M; Köhler, M; Johnston, P N

2000-03-01

361

Real-time active cosmic neutron background reduction methods  

NASA Astrophysics Data System (ADS)

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 lowenergy 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 manmade 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

362

Radiochemical neutron activation analysis: Status in chemical analysis  

SciTech Connect

Neutron activation analysis (NAA) is a powerful technique for determining numerous trace elements in a large variety of samples. The main advantages of NAA are (a) multielement character, (b) low level of determination for a sizeable number of elements, (c) virtual freedom of a blank, (d) generally good selectivity, and (e) absence of interferences due to differences in physical or chemical state. In addition to instrumental NAA, radiochemical NAA (RNAA) is often employed for improvement of the determination limit, accuracy, and/or precision. Radiochemical separations may be performed in various degrees of radiochemical purity, depending of the problem at hand. Since germanium detectors with large active volumes have become available as well as germanium well-type detectors with high geometric efficiency, a noticeable development has progressed in the direction of a combination of minimal post-irradiation chemical efforts with the potentials of germanium gamma spectrometry and computerized data handling, at least in cases in which no ultimate sensitivity is required. Automation has been frequently advocated as an attractive way to solve problems of lengthy and complex radiochemical procedures. In general, it can be said that, whereas instrumental NAA has a strong point in respect to costs and multielement character, RNAA scores high in analytical quality as the main feature. Areas where RNAA remains to play a role in the foreseeable future discussed.

de Goeij, J.J.M.

1988-01-01

363

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

364

Activation experiments at TFTR in deuterium-tritium neutron field  

Microsoft Academic Search

Samples of materials, of relevance to ITER and DEMO reactors, have been irradiated at TFTR in a mixed D-T and D-D neutron field over the past 3 years. The samples have been placed at various locations close to, and around, the TFTR vacuum vessel to obtain the impact of the variation of neutron energy spectrum on induced radioactivity. Intermediate measurements

A. Kumar; H. W. Kugel; G. Ascione

1998-01-01

365

Neutron flux and energy characterization of a plutonium-beryllium isotopic neutron source by monte carlo simulation with verification by neutron activation analysis  

NASA Astrophysics Data System (ADS)

The purpose of this research was to characterize the neutron energy distribution and flux emitted from the UNLV plutonium-beryllium source, serial number MRC-N-W PuBe 453. This was accomplished through the use of the MCNPX/5 Monte-Carlo particle transport code to simulate radiation interactions within the physical environment of the source and its surroundings. The moderating drum currently containing the source as well as all of the sampling ports were accurately modeled in MCNPX/5. This geometry was then used to simulate the neutron interactions taking place in these geometries. The results of the simulations were then verified by the use of specifically chosen activation detectors and threshold foils designed to accurately convey information on the energy distribution and flux of the neutrons present at multiple sampling locations.

Harvey, Zachary R.

366

Use of a TLD-based multisphere spectrometry system to measure the neutron spectra around a not-self-shielded PET cyclotron: Preliminary results.  

PubMed

In the present work, we utilized the BSS system with TLD-600 and TLD-700 to measure the neutron spectra around the GE-PETtrace 8 cyclotron of the Development Centre of Nuclear Technology (CDTN/CNEN) in Belo Horizonte, Brazil. The cyclotron is capable of accelerating protons up to 16.5 MeV, to production of fluorine-18. Four points inside the bunker of the cyclotron were studied. Two points in front of the primary radiation beam and other two opposed to the primary radiation beam. The measurements were unfolded with the BUMS and the NSDUAZ computer codes. The dosimetric quantities obtained were in agreement with the other published data and were coherent with the expected from theoretical estimates obtained from source term informed by the manufacturer of the cyclotron. PMID:22818173

Guimarães, A M; Lacerda, M A S; Santos, J A L; Maletta, P G M; Rodrigues, S L M; Andrade, R S; Vilela, E C; da Silva, T A

2012-06-09

367

Determination of uranium and thorium in solar salts by neutron activation analysis  

Microsoft Academic Search

Uranium and thorium contents of solar salts were measured by neutron activation analysis. In advance of neutron irradiation, U and Th were concentrated and separated from some interfering elements by neutralization in which they were precipitated with aluminium hydroxide from solutions obtained by dissolving the salts in water or dilute nitric acid solution. The uranium and thorium concentrations determined were

K. Ogiwara; T. OSSAKA; M. Mukaida; T. Honda

1995-01-01

368

In vivo activation analysis of spinal calcium using 25 keV neutrons  

SciTech Connect

The applicability of 25 keV neutrons to the in vivo activation analysis of spinal calcium is examined both theoretically and experimentally. It is shown that the use of this energy results in an increase in sensitivity over higher energy neutrons so that patient dose may be significantly reduced.

Cousins, T.; Kennett, T.J.; Prestwich, W.V.; Webber, C.E.

1980-11-01

369

Neutron-activation analysis of geologic samples for gold and associated elements using a power reactor  

Microsoft Academic Search

The method of neutron-activation analysis (NAA) using research reactors as neutron sources is widely used in the elemental analysis of rocks and ores. Because of the limited access to research reactors, however, it is difficult case, power reactors are promising for use in NAA. The authors investigated the possibility of using a power reactor for NAA of geological samples for

Yu. N. Burminstenko; A. A. Medvedev; V. V. Kovalenko; A. V. Markov

1987-01-01

370

Determination of boron in food and biological reference materials by neutron capture prompt-? activation  

Microsoft Academic Search

Boron concentrations were determined by in-beam neutron capture prompt-? activation analysis for 31 food and biological reference materials prepared by the National Institute of Standards and Technology, Agriculture Canada, the National Institute for Environmental Studies of Japan, and the International Atomic Energy Agency. Sensitivity and background enhancements that are consequences of neutron scattering in hydrogenous matrices such as biological reference

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

1990-01-01

371

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

372

Effects of Neutron Irradiation and X-Ray Bombardment on Actively Biased Si Avalanche Photodiodes.  

National Technical Information Service (NTIS)

The results of a study of the effects of both neutron and X-ray irradiation on Si APD's biased to M greater than or equal to 100 during irradiation are presented. The results indicate that neutron irradiation of actively biased APD's is beneficial as long...

C. E. Barnes

1978-01-01

373

Neutron activation determination of impurities in very pure silver with separation of the elements by extraction  

Microsoft Academic Search

A neutron activation method was developed for 24 microimpurities in Ag. ; In order to eliminate the matrix and to separate the impurities extraction was ; used. The shielding effect of the Ag samples on the neutron flux was evaluated ; theoretically and experimentally verified. (tr-auth);

P. I. Artyukhin; E. A. Startseva; A. V. Nikolaev

1973-01-01

374

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

375

Alpha Emission Spectra of 27Al, 50,52Cr, 55Mn, 54,56Fe, 58,60Ni Nucleus for Neutron Induced Reaction  

NASA Astrophysics Data System (ADS)

The design of novel nuclear facilities, fusion as well as fission reactors, requires the knowledge of all properties of relevant materials, including the nuclear differential cross sections for a careful selection. The nuclear cross sections data for gas production via particle (neutron, proton, alpha, etc.) induced reactions are great importance in the domain in the fusion reactor technology, particularly in the calculation of nuclear transmutation rates, nuclear heating and radiation damage due to gas formation. In fusion reactor structures, a serious damage mechanism has been gas production in the metallic resulting from diverse nuclear reactions, mainly through (n, p) and (n, ?), (n, d), (n, t). In the present study, by using equilibrium reaction mechanisms, the (n, x?) reaction alpha emission spectra for 27Al, 50,52Cr, 55Mn, 54,56Fe, 58,60Ni isotopes were investigated from 9 to 15 MeV incident neutron energy. The equilibrium results have been calculated by using the hybrid model, the geometry dependent hybrid model. Calculation results have been also compared with the available measurements in literature.

Tel, E.; Gokce, A. A.; Ugur, F. A.; Kara, A.

2013-06-01

376

Manufacture and properties of erythromycin beads containing neutron-activated erbium-171  

SciTech Connect

To evaluate the effects of a neutron activation radiolabeling technique on an enteric-coated multiparticulate formulation of erythromycin, test quantities were produced under industrial pilot scale conditions. The pellets contained the stable isotope erbium oxide (Er-170), which was later converted by neutron activation into the short-lived gamma ray-emitting radionuclide, erbium-171. In vitro studies indicated that the dissolution profile, acid resistance, and enteric-coated surface of the pellets were minimally affected by the irradiation procedure. Antimicrobial potency was also unaffected, as determined by microbiological assay. Neutron activation thus appears to simplify the radiolabeling of complex pharmaceutical dosage forms for in vivo study by external gamma scintigraphy.

Parr, A.F.; Digenis, G.A.; Sandefer, E.P.; Ghebre-Sellassie, I.; Iyer, U.; Nesbitt, R.U.; Scheinthal, B.M. (Univ. of Kentucky, Lexington (USA))

1990-03-01

377

Thermal and 14.4 MeV neutron activation cross sections of argon  

Microsoft Academic Search

Thermal and 14.4 MeV neutron activation cross sections of argon were measured with argon quinol-clathrate powder as target material. The thermal neutron activation cross section of the 40Ar(n, gamma)41Ar reaction was measured to be 510+\\/-25 mb. The 14.4+\\/-0.3 MeV neutron activation cross sections for the reactions 38Ar(n,p)38Cl, 40Ar(n,p)40Cl(1.4 min), 40Ar (n, np+n, pn+n, d)39Cl and 40Ar(n, alpha)37S were measured to

N. Ranakumar; E. Karttunen; R. W. Fink

1969-01-01

378

Neutron Activation Cool-down of the Tokamak Fusion Test Reactor  

SciTech Connect

Tokamak Fusion Test Reactor (TFTR) final operations and post-shutdown neutron activation measurements were made. Ionization chambers were used to follow TFTR activation during operations and after shutdown. Gamma-ray energy spectroscopy measurements were performed to characterize TFTR activation at accessible vessel-bays and on sample hardware removed from structures at various distances from the vessel. The results demonstrate long-lived activations from common, commercially available materials used in the fabrication and field engineering of TFTR. The measurements allow characterization of residual TFTR neutron activation, the projection of residual activation decay, and benchmarking of low activation issues simulations.

Ascione, G.; Kugel, H.W.; Kumar, A.; Tilson, Jr, C.

1998-06-10

379

Determination of some macro and micro nutrients in soils of Maharashtra State by instrumental neutron activation analysis using 252 Cf as a thermal neutron source  

Microsoft Academic Search

Some macro and micronutrients in soils from some districts of Maharashtra State have been determined by instrumental neutron\\u000a activation analysis. Neutrons from 252Cf have been used for irradiation. The activity induced was measured by a HPGe detector coupled to a MCA unit. The statistical\\u000a evaluation of the method has been explained.

U. K. Baviskar; Z. R. Turel

2004-01-01

380

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

381

Active Neutron Interrogation to Detect Shielded Fissionable Material  

Microsoft Academic Search

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

D. L. Chichester; E. H. Seabury

2009-01-01

382

Delayed Gamma-Rays from Uranium Activated by Neutrons  

Microsoft Academic Search

A cloud chamber in a magnetic field was operated in conjunction with a source of neutrons in such a way as to observe gamma-rays emitted during the bombardment of uranium by neutrons and the number emitted about 1\\/2 second after bombardment in alternate expansions of the chamber. Although the energy distribution of the gamma-rays seems to be about the same

J. C. Mouzon; R. D. Park

1939-01-01

383

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

384

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

SciTech Connect

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. 44 references.

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

1986-01-01

385

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

386

3He neutron detector design for active detection of cargo containers  

NASA Astrophysics Data System (ADS)

We report on the design of a neutron detector using industry standard 3He tubes to count delayed neutrons during the interrogation of cargo containers for the presence of Special Nuclear Material (SNM). Simulations of the detector design were run for delayed neutron spectra for a variety of cargos containing SNM using the Monte Carlo computer code COG. The simulations identified parameters crucial to optimize the detector design. These choices include moderating material type and thickness, tube spacing, tube pressure and number of tubes. An experimental prototype was also constructed based on the simulated design specifications. This paper discusses the parameters that lead up to the optimized detector design. It also compares the performance of the Monte Carlo simulated design and the experimental detector when exposed to a 239Pu-Be source.

McDevitt, Daniel B.; Eberhard, J. W.; Zelakiewicz, Scott; Maschinot, Aaron

2008-05-01

387

Quantitation of the Degree of Osteoporosis by Measure of Total-Body Calcium Employing Neutron Activation.  

National Technical Information Service (NTIS)

Two techniques for measuring the amount of Ca in the total skeleton were employed: total-body neutron activation analysis (TBNAA) and the determination of the mineral content of a bone of the appendicular skeleton (absorptiometric measurement of the radiu...

S. H. Cohn I. Zanzi A. Vaswani S. Wallach J. Aloia

1975-01-01

388

Analytical Investigations of Glazed Islamic Pottery. 2. Instrumental Neutron Activation Analysis.  

National Technical Information Service (NTIS)

42 fragments of medieval glazed pottery from seven sites in Iran, Afghanistan and India were analyzed by instrumental neutron activation analysis (INAA). In addition a secondary clay standard and some samples were analyzed by X-ray fluorescence for their ...

E. Pernicka P. Krejsa

1978-01-01

389

Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) for Elemental Analysis  

SciTech Connect

This research project was to improve the prompt gamma-ray neutron activation analysis (PGNAA) measurement approach for bulk analysis, oil well logging, and small sample thermal enutron bean applications.

Robin P. Gardner

2006-04-11

390

Dosimetric optimization of postproduction neutron-activated Erbium-170-oxide-enriched pancreatin  

SciTech Connect

The feasibility of postproduction neutron activation of an enteric-coated pancreatic enzyme preparation for in vivo gastric emptying studies has been investigated. During production of this multicomponent preparation, small amounts of {sup 170}Er-enriched erbium oxide, suitable for neutron activation, were added. Postproduction neutron irradiation of the labeled preparation resulted in short-lived (7.5 hr) gamma-emitting {sup 171}Er. Various radiocontaminants, however, are produced also. Because of variations in activation yields, half-lives, decay schemes and radiotoxicities, both major and trace consitituents were considered for optimization of both dosimetry and the diagnostic measurement. Conditions were optimized for the best ratio of the committed dose equivalent due to {sup 171}Er to the total committed dose equivalent. The results show that postproduction neutron activation of a {sup 170}Er-enriched multicomponent preparation can be performed safely within the guidelines set by the WHO for experiments in humans involving radioactive materials. 9 refs., 3 tabs.

Borm, J.J.J.; Bruno, M.J.; Goeij, J.J.M. de [Academic Medical Center, Amsterdam (Netherlands)]|[Delft Univ. of Technology, Mekelweg (Netherlands)]|[Nordmark Arzneimittel GmbH, Uetersen (Germany)] [and others

1995-05-01

391

Elemental Analysis of Human Serum and Serum Protein Fractions by Thermal Neutron Activation.  

National Technical Information Service (NTIS)

Some acplications of thermal neutron activation for the determination of elemental contents in human serum and human serum protein fractions are presented. First total serum is dealt with; second serum protein fractions obtained by gel filtration are desc...

J. R. W. Woittiez

1984-01-01

392

Dynamic Albedo of Neutrons (DAN): Active Nuclear Experiment Onboard NASA Mars Science Laboratory  

NASA Astrophysics Data System (ADS)

In our presentation we describe instrument DAN based on neutron activation technique and selected for NASA/MSL mission. The main task of this experiment is local measuruments of water distribution in martian subsurface around MSL rover.

Mitrofanov, I. G.; Litvak, M. L.; Kozyrev, A. S.; Mokrousov, M. I.; Sanin, A. B.; Tretyakov, V. I.

2005-03-01

393

Determination of isotopic thorium in biological samples by combined alpha spectrometry and neutron activation analysis.  

SciTech Connect

Thorium is a naturally occurring element for whom all isotopes are radioactive . Many of these isotopes are alpha emitting radionuclides, some of which have limits for inhalation lower than plutonium in current regulations . Neutron activation analysis can provide for the low-level determination of 232Th but can not determine other isotopes of dosimetric importance . Biological and environmental samples often have large quantities of materials which activate strongly, limiting the capabilities of instrumental neutron activiation analysis . This paper will discuss the application of a combined technique using alpha spectrometry and radiochemical neutron activiation analysis for the determination of isotopic thorium .

Glover, S. E. (Samuel E.)

2003-01-01

394

Investigation of the impurity concentrations and product activities of some targets used in radioisotope production: a neutron activation analysis study  

Microsoft Academic Search

Neutron activation analysis using the k\\u000a 0 standardization method (k\\u000a 0-NAA) and fast neutron activation analysis using reactor fission neutrons, were used to determine the impurity concentrations\\u000a in WO3, MoO3, SnO2 and TeO2 targets. The radioimpurities 124Sb, 134Cs, 60Co, 87Rb, 182Ta, 233Pa, 65Zn, 59Fe, 110mAg, 51Cr, 95Zr, 75Se and 114mIn were found in the irradiated targets and their origin either

A. El Abd; M. Mostafa

2011-01-01

395

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

Microsoft Academic Search

We describe a method for obtaining reliable activation cross-sections in the neutron energy range between 13.4 and 14.9MeV for the reactions producing short-lived nuclei with half-lives between 0.5 and 30min. We noted neutron irradiation fields and measured induced activities, including (1) the contribution of scattered low-energy neutrons, (2) the fluctuation of the neutron fluence rate during the irradiation, (3) the

K. Kawade; H. Sakane; Y. Kasugai; M. Shibata; T. Iida; A. Takahashi; T. Fukahori

2003-01-01

396

Non-destructive analysis of phosphorus by neutron activation analysis in biochemical products  

Microsoft Academic Search

A method of neutron activation analysis is described for the quantitative determination of phosporus in nucleic acids, nucleotides\\u000a and glucose-6-phosphate in amounts of 0.1 to 200 ?g, without any chemical separation. This technique may be usefully applied\\u000a to the measurement of the phosporus content in organic materials and biochemical preparations. The procedure involves a short\\u000a neutron activation in a nuclear

E. Sabbioni; L. Clerici; F. Girardi; F. Campagnari

1973-01-01

397

Neutron Activation Cross Section of Molybdenum Isotopes at 14.8 MeV  

Microsoft Academic Search

The neutron activation cross sections of Mo isotopes have been measured for the 14.8 MeV neutron. The cross sections have been determined with reference to the known A1 (n, ?)Na and the Al(n, p)Mg reactions. The cyclic activation method was employed for the ?-ray measurement of short-lived nuclei. A 55 cm Ge(Li) detector was used for the measurement of ?-ray

Susumu AMEMIYA; Kei-ichi ISHIBASHI; Toshio KATOH

1982-01-01

398

Evaluation of sodium activation distribution in the PMMA water phantom after fast neutron irradiation.  

PubMed

(24)Na produced by the neutron activation of stable sodium in the body is commonly used to assess neutron doses after criticality accidents. However, the (24)Na distribution is not uniform owing to the interaction with the human body. In this study, we experimentally evaluated the (24)Na distribution in a PMMA water phantom and 60 polyethylene vials. The vials were analyzed to evaluate the sodium activation distribution in the PMMA water phantom by employing a correction factor. PMID:23548694

Ha, Wi-Ho; Park, Seyong; Yoo, Jaeryong; Yoon, Seokwon; Lee, Seung-Sook; Kim, Jong Kyung

2013-03-16

399

Trace element analysis of K, U and Th in high purity materials by neutron activation analysis  

SciTech Connect

The concept and usage of 'high purity' are explained. Trace element analysis of K, U and Th by neutron activation analysis is described, the radio-isotopes and their corresponding gamma-rays used to identify the elements are listed. The interfering elements are described. The advantages and disadvantages of using neutron activation analysis are discussed. Some examples of trace impurity determinations in high purity materials are provided.

Pillalamarri, Ila [MIT-EAPS Neutron Activation Analysis Laboratory, Department of Earth Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

2005-09-08

400

Solar Active Region and Quiet-Sun Extreme-Ultraviolet Spectra from SERTS-95  

NASA Astrophysics Data System (ADS)

Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph was flown on 1995 May 15 (SERTS-95), carrying a multilayer-coated toroidal diffraction grating that enhanced the instrumental sensitivity in its second-order wave band (171-225 Å). Spectra and spectroheliograms of NOAA active region 7870 (N09 W22) were obtained in this wave band with a spectral resolution (instrumental FWHM) ~30 mÅ and in the first-order wave band (235-335 Å) with a spectral resolution ~55 mÅ. Spectra and spectroheliograms of quiet-Sun areas northeast of the active region were also obtained. We derived the SERTS-95 relative radiometric calibration directly from flight data by means of density- and temperature-insensitive line intensity ratios. Most theoretical values for such ratios were obtained from the CHIANTI database. A total of 44 different lines were used to derive the relative radiometric calibration in the two spectral orders, most of them coming from seven (Fe X-Fe XVI) of the nine (Fe IX-Fe XVII) observed ionization stages of iron. The resulting relatively calibrated line intensities agree well with their corresponding normalized theoretical values. This supports the overall accuracy of the atomic physics parameters and demonstrates the power of the technique. The present work extends earlier work by Brosius, Davila, & Thomas, who determined the SERTS-95 second-order response using this technique. Many of the ratios employed here can be used to carry out a similar calibration exercise on spectra from the Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric Observatory (SOHO). We placed the line intensities onto an absolute scale by forcing our quiet-Sun He II lambda303.8 + Si XI lambda303.3 intensity to match that from previous observations. The resulting active region and quietSun absolutely calibrated line lists contain 127 and 20 lines, respectively. Active region densities derived from density-sensitive line intensity ratios of Fe X, XI, XIII, and XIV are mutually consistent with log n_e ~ 9.4 +/- 0.2; densities derived from Fe XII are significantly greater (log n_e ~ 10).

Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.

1998-12-01

401

Determination of a deuteron-beryllium neutron source spectrum by multifoil activation  

SciTech Connect

The spectral neutron flux from a deuteron-beryllium neutron source, which is driven by a 19-MeV cyclotron deuteron beam and serves mainly for integral activation tests of fusion reactor structural materials, was determined by the multifoil activation method. Twenty-two selected threshold activation reactions were employed. An initial guess spectrum calculated by a Monte Carlo simulation was adjusted using the SAND-II code to be consistent with the measured reaction rates. The total neutron flux averaged over a 5 x 5 mm sample was found to be 2.52 {times} 10{sup 11} n/s{center_dot}cm{sup {minus}2} at 10 {micro}A of deuteron beam with uncertainty of {approximately}10%. The activation cross sections used were based on the FENDL/A-2.0 library. However, they were extrapolated beyond 20 MeV, the upper energy limit of that library, to the maximum neutron energy of 23.4 MeV and were modified where necessary. As a result, a self-consistent set of activation cross sections was obtained, which may also be used for the characterization of other neutron fields. The determined spectral neutron flux is to be used for analyses of integral activation tests of fusion reactor-relevant materials.

Maekawa, Fujio; Ikeda, Yujiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan); Moellendorff, U. von; Wilson, P.P.H. [Forschungszentrum Karlsruhe (Germany). Inst. fuer Kern- and Energietechnik

1999-09-01

402

Application of active and passive neutron non destructive assay methods to concrete radioactive waste drums  

NASA Astrophysics Data System (ADS)

This paper deals with the application of non-destructive neutron measurement methods to control and characterize 200 l radioactive waste drums filled with a concrete matrix. Due to its composition, and particularly to hydrogen, concrete penalizes the use of such methods to quantify uranium (U) and plutonium (Pu) components, which are mainly responsible of the ?-activity of the waste. The determination of the alpha activity is the main objective of neutron measurements, in view to verify acceptance criteria in surface storage. Calibration experiments of the Active Neutron Interrogation (ANI) method lead to Detection Limit Masses (DLM) of about 1 mg of 239Pueff in the total counting mode, and of about 10 mg of 239Pueff in the coincidence counting mode, in case of a homogeneous Pu source and measurement times between one and two hours. Monte Carlo calculation results show a very satisfactory agreement between experimental values and calculated ones. Results of the application of passive and active neutron methods to control two real drums are presented in the last part of the paper. They show a good agreement between measured data and values declared by the waste producers. The main difficulties that had to be overcome are the low neutron signal in passive and active coincidence counting modes due to concrete, the analysis of the passive neutron signal in presence of 244Cm in the drum, which is a strong spontaneous fission neutron emitter, the variation of the active background with the concrete composition, and the analysis of the active prompt neutron signal due to the simultaneous presence of U and Pu in the drums.

Jallu, F.; Passard, C.; Brackx, E.

2011-09-01

403

Neutron induced background gamma activity in low-level Ge-spectroscopy systems  

NASA Astrophysics Data System (ADS)

Two high purity germanium (HPGe) detectors were located in two different passive shields: one in pre-WW II iron and the second in commercial low background lead. Gamma lines emitted after neutron capture, as well as after inelastic scattering on the germanium crystal were detected and then analyzed. The thermal and fast neutron fluxes were calculated and their values were compared for the two different kinds of detector shield. Several materials having different neutron slowing-down properties were packed in Marinelli geometry, positioned on the lead shielded detector and measured for around 106 s. The main goal was to estimate a possible influence of the sample on the intensity of the neutron induced Ge gamma lines. On the iron-shielded detector a massive (3 in. thick) NaI Compton suppression system showed a measurable activity from neutron capture and inelastic scattering on sodium and iodine nuclei.

Jovan?evi?, N.; Krmar, M.; Mrda, D.; Slivka, J.; Bikit, I.

2010-01-01

404

Determination of impurities in technical cobalt by instrumental neutron activation analysis  

NASA Astrophysics Data System (ADS)

Instrumental neutron activation techniques for the determination of 13 impurities with limit detection 0.1-100 mg/kg in technical cobalt have been developed using thermal and epithermal neutrons of a nuclear reactor. Self-shielding and disturbance of neutron flux (59Co has a high neutron capture cross-section) by a sample were taken into account by using some references and from the results obtained in preliminary experiments. Samples and standards have been arranged in such a way, that neutron flux disturbance was less than 2-3%. The Al-Pb-Cd-Cu filter was used for absorption of low-energy ?-rays of 60mCo and 61Co.

Mukhamedshina, N. M.; Mirsagatova, A. A.; Zinov'ev, V. G.

2003-01-01

405

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

406

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

407

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

408

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

409

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

410

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

411

Utilization of recycled neutron source to teach prompt gamma analysis activation-PGNA  

NASA Astrophysics Data System (ADS)

Neutron activation analysis based on prompt gamma ray emission has significantly developed during the past twenty years. The technique is particularly suited for the identification of low atomic number elements, as nitrogen that is a main component of drugs and explosives. Identification of these substances is important in the context of humanitarian demining, and in the control of illicit traffic of drugs and explosives. As a good example of recycling of radioactive sources, a ^241Am-Be neutron source emitting 10^7neutron/s, that was not longer in use for other purposes at Ingeominas, was used to build a neutron irradiator that can be used to teach prompt gamma ray analysis, and other nuclear techniques. We irradiated individual samples, each about 4 gram, of three different elements: nitrogen in urea, silicon in milled rock, and cadmium in cadmium oxide. The prompt gamma rays emitted in the nuclear reactions ^112Cd (neutron,gamma) ^113Cd, ^28Si (neutron,gamma) ^29Si and ^14N (neutron,gamma) ^15N were identified using a well-type NaI (Tl) detector, connected to a multi-channel analyzer.

Delgado-Correal, Camilo; Munera, Hector

2008-03-01

412

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

413

Measurement of the Neutron Activity of a exp 252 Cf Source Relative to the Average Number of Prompt Neutrons Emitted Per Fission for the Spontaneous Fission.  

National Technical Information Service (NTIS)

A method was developed for measuring the absolute neutron activity of a large exp 252 Cf source. The neutron counting assembly is composed of eight BF3 counters mounted in a large tank filled with water which is used as a moderator. The detection efficien...

J. Frehaut M. Beau

1980-01-01

414

Analysis of Different Uncertainty Activation Cross Section Data Libraries for LWR, ADS and DEMO Neutron Spectr  

NASA Astrophysics Data System (ADS)

This work is aimed to present the main differences of nuclear data uncertainties among three different nuclear data libraries: EAF-2007, EAF-2010 and SCALE-6.0, under different neutron spectra: LWR, ADS and DEMO (fusion). To take into account the neutron spectrum, the uncertainty data are collapsed to onegroup. That is a simple way to see the differences among libraries for one application. Also, the neutron spectrum effect on different applications can be observed. These comparisons are presented only for (n,fission), (n,gamma) and (n,p) reactions, for the main transuranic isotopes (234,235,236,238U, 237Np, 238,239,240,241Pu, 241,242m,243Am, 242,243,244,245,246,247,248Cm, 249Bk, 249,250,251,252Cf). But also general comparisons among libraries are presented taking into account all included isotopes. In other works, target accuracies are presented for nuclear data uncertainties; here, these targets are compared with uncertainties on the above libraries. The main results of these comparisons are that EAF-2010 has reduced their uncertainties for many isotopes from EAF-2007 for (n,gamma) and (n,fission) but not for (n,p); SCALE-6.0 gives lower uncertainties for (n,fission) reactions for ADS and PWR applications, but gives higher uncertainties for (n,p) reactions in all applications. For the (n,gamma) reaction, the amount of isotopes which have higher uncertainties is quite similar to the amount of isotopes which have lower uncertainties when SCALE-6.0 and EAF-2010 are compared. When the effect of neutron spectra is analysed, the ADS neutron spectrum obtained the highest uncertainties for (n,gamma) and (n,fission) reactions of all libraries.

Díez, C. J.; Cabellos, O.; Martínez, J. S.

2012-05-01

415

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

416

Activation cross-section for reactions induced by 14 MeV neutrons on natural silver  

Microsoft Academic Search

Cross-sections for (n,2n), (n,p), and (n,?) reactions have been measured on silver isotopes at the neutron energies from 13.5 to 14.8MeV using the activation technique in combination with high-resolution ?-ray spectroscopy. Corrections were made for the literature cross-sections of 109Ag(n,2n) 108mAg reaction with incorrect half-life of product 108mAg. Neutrons were produced via the 3H(d,n)4He reaction using solid TiT. The neutron

Junhua Luo; Fei Tuo; Xiangzhong Kong; Rong Liu; Li Jiang

2009-01-01

417

Passive and Active Fast-Neutron Imaging in Support of Advanced Fuel Cycle Initiative Safeguards Campaign  

SciTech Connect

Results from safeguards-related passive and active coded-aperture fast-neutron imaging measurements of plutonium and highly enriched uranium (HEU) material configurations performed at Idaho National Laboratory s Zero Power Physics Reactor facility are presented. The imaging measurements indicate that it is feasible to use fast neutron imaging in a variety of safeguards-related tasks, such as monitoring storage, evaluating holdup deposits in situ, or identifying individual leached hulls still containing fuel. The present work also presents the first demonstration of imaging of differential die away fast neutrons.

Blackston, Matthew A [ORNL; Hausladen, Paul [ORNL

2010-04-01

418

Development of a prompt gamma activation analysis facility using diffracted polychromatic neutron beam  

NASA Astrophysics Data System (ADS)

A prompt gamma activation analysis facility has recently been developed at Hanaro, the 24MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic thermal neutrons are extracted by setting pyrolytic graphite crystals at a Bragg angle of 45°. The detection system comprises a large single n-type HPGe detector, signal electronics and a fast ADC. Neutron beam characterization was performed both theoretically and experimentally. The neutron flux was measured to be 7.9×107n/cm2s in a 1×1cm2 beam area at the sample position with a uniformity of 12%. The corresponding Cd-ratio for gold was found to be 266. The beam quality was compared with other representative thermal neutron prompt gamma activation analysis. The detection efficiency was calibrated up to 11MeV using a set of radionuclides and the (n,?) reactions of N and Cl. Finally, the sensitivities and the detection limits were obtained for several elements.

Byun, S. H.; Sun, G. M.; Choi, H. D.

2002-07-01

419

Diverse activity spectra of bacteriocin-like inhibitory substances having activity against mutans streptococci.  

PubMed

Mutans streptococci (MS) are known to be causative agents of dental caries. It has been suggested that these cariogenic bacteria could be eliminated from dental plaque by application of bacteriocins or bacteriocin-like inhibitory substances (BLIS). In the present study 272 bacterial strains of the genera Streptococcus, Enterococcus and Staphylococcus were tested for their production of BLIS activity against MS by use of a deferred antagonism test on agar media supplemented with either whole blood or yeast extract. Although only 14.3% of the test strains displayed anti-MS activity, the inhibitory agents produced by these strains were characterised by considerable diversity in the range of their inhibitory action against both MS and other common oral streptococcal species. It is suggested that combinations of relatively specifically targeted anti-MS BLIS may have potential application to the prevention of dental caries. PMID:11125201

Balakrishnan, M; Simmonds, R S; Tagg, J R

420

Determination of gold in two Egyptian gold ores using instrumental neutron activation analysis  

Microsoft Academic Search

The applicability of thermal neutron activation analysis for the determination of gold and other elements in two Egyptian gold ores has been studied. Ten samples collected from El Sukari and Atud in the Eastern Desert-Egypt have been analyzed. The samples were properly prepared together with their standards and simultaneously irradiated in a neutron flux of the order 7×1011n\\/cm2s using the

A. El-Taher; K.-L. Kratz; A. Nossair; A. H. Azzam

2003-01-01

421

Effective neutron activation cross-sections of some chlorine and sulphur reactions in NRX  

Microsoft Academic Search

Summary  Reaction rates have been measured in the lattice and reflector of NRX for those neutron activation reactions of chlorine and\\u000a sulphur that lead to the production of38Cl,32P and35S. The effective cross-sections of these reactions for reactor neutrons have been calculated from cobalt monitors enclosed\\u000a with the irradiated samples.

R. W. Durham; F. Girardi

1961-01-01

422

A prompt gamma neutron activation analysis facility using a diffracted beam  

Microsoft Academic Search

A prompt gamma neutron activation analysis facility has been constructed at the MIT Research Reactor using a diffracted beam from a multilayered graphite monochromator. A beam of 0.0143 eV neutrons of intensity 6 × 106n\\/cm2s is available at the sample position. Backgrounds are low due to the use of the diffracted beam and are further improved by a sapphire crystal

Otto K. Harling; Jean-Michel Chabeuf; Frédérique Lambert; Gopika Yasuda

1993-01-01

423

The feasibility of accelerator-based in vivo neutron activation analysis of nitrogen  

Microsoft Academic Search

The feasibility of accelerator-based in vivo neutron activation analysis of nitrogen has been investigated. It was found that a moderated neutron flux from ?10?A of 2.5MeV 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

J. M. O’Meara; B. W. Blackburn; D. L. Chichester; D. P. Gierga; J. C. Yanch

2001-01-01

424

Effects of hydration on elemental sensitivities in neutron activation analysis using prompt and delayed gamma rays  

Microsoft Academic Search

A 1.85×1011 Bq (5Ci) Am\\/Be neutron source is being used to investigate the feasibility of applying the absolute method in the elemental analysis of bulk samples by instrumental neutron activation making use of prompt and delayed gamma rays. Among the different factors which might contribute to variations in sensitivity or in the uncertainly associated with the elemental concentration is the

M. B. Alamin; N. M. Spyrou

1995-01-01

425

Measurement of k 0 Factors in Prompt Gamma-Ray Neutron Activation Analysis  

Microsoft Academic Search

The guided thermal neutron beam at 100 MW Dhruva research reactor facility of Bhabha Atomic Research Centre (BARC) was used to carry out prompt gamma-ray neutron activation analysis (PGNAA). The prompt k\\u000a0-factors have been determined for the isotopes of the elements H, B, K, Co, Cu, Ca, Ti, Cr, Cd, Ba, Hg and Gd with respect to 1951 keV

R. N. Acharya; K. Sudarshan; A. G. C. Nair; Y. M. Scindia; A. Goswami; A. V. R. Reddy; S. B. Manohar

2001-01-01

426

Composite spectra Paper 13: 93 Leonis, a chromospherically-active binary  

NASA Astrophysics Data System (ADS)

We isolate the spectrum of the secondary component of the composite-binary system 93 Leonis by spectrum subtraction, classify it, and measure the mass ratio of the system. An accurate visual orbit and a well-determined parallax provide reliable measurements of orbital inclination and distance, enabling us to determine precisely the individual masses and other stellar parameters. The primary star is of type ~G7 III, and the secondary is a rapidly rotating star of type A7 IV. Our photographic spectra at 10 Å mm-1 are invaluable for accurate spectral classification in such cases. By combining 23 measurements of the secondary's velocity with 102 of the primary's and deriving a double-lined orbit, we determine the mass ratio (q=M1/M2) of 93 Leo to be 1.09 +/- 0.04. The same value is derived by cross-correlating high-dispersion spectra of 93 Leo B extracted from opposite nodal phases. That value of q is consonant with previous research, but its precision is considerably improved. We show that random errors arising from the cross-correlation of broad, weak features constitute a natural limit to that precision. The derived masses of M1= 2.2 Msolar, M2= 2.0 Msolar for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (logTeff, logL) plane. The giant is almost certainly on its first ascent of the red giant branch, and the dwarf has evolved significantly from the main sequence. The stars fit an isochrone for log(age) = 8.95, about 0.9 Gyr. Metallicity near to solar is suggested by the close correspondence between the component spectra and those of the respective solar-abundance standards. The primary in 93 Leo displays a marked level of chromospheric activity. By combining our high-dispersion spectra we are able to isolate emission in the Ca II K line. The chromospheric material has a small infall velocity, giving rise to a disc-averaged redshift of about 4 km s-1, and an unchanging velocity profile which can be attributed to a large number of small, active events like prominences across the surface. While we can say that there was no perceptible change in the emission strength over an interval of 4 months, we have not made systematic observations to monitor its long-term stability. We contrast the components of 93 Leo with those of ? Equ, whose analysis was the subject of Paper 11 in this series. The primary components are very similar, but the two secondary components are extremely different in nature: whereas 93 Leo B is a broad-lined, apparently normal A star, the secondary of ? Equ is a sharp-lined Am star of type ~kA3hA4mA9. We question why that should be, and recommend that a greater emphasis be placed on extracting accurate stellar parameters from the components of spectroscopic binaries as a means towards a better understanding of the vagaries of stellar evolution. 93 Leo has a 9-mag visual companion which appears to be a physical member of the system and to be a single-lined spectroscopic binary with a period of the order of a century.

Griffin, R. E. M.; Griffin, R. F.

2004-05-01

427

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

428

Infrared Spectra and Spectral Energy Distributions for Dusty Starbursts and Active Galactic Nuclei  

NASA Astrophysics Data System (ADS)

We present spectroscopic results for all galaxies observed with the Spitzer Infrared Spectrograph (IRS) that also have total infrared fluxes f IR measured with the Infrared Astronomical Satellite (IRAS), also using AKARI photometry when available. Infrared luminosities and spectral energy distributions (SEDs) from 8 ?m to 160 ?m are compared to polycyclic aromatic hydrocarbon emission from starburst galaxies or mid-infrared dust continuum from active galactic nuclei (AGNs) at rest-frame wavelengths ~8 ?m. A total of 301 spectra are analyzed for which IRS and IRAS include the same unresolved source, as measured by the ratio f ?(IRAS 25 ?m)/f ?(IRS 25 ?m). Sources have 0.004 < z < 0.34 and 42.5 < log L IR < 46.8 (erg s-1) and cover the full range of starburst galaxy and AGN classifications. Individual spectra are provided electronically, but averages and dispersions are presented. We find that log [L IR/?L ?(7.7 ?m)] = 0.74 ± 0.18 in starbursts, log [L IR/?L ?(7.7 ?m)] = 0.96 ± 0.26 in composite sources (starburst plus AGN), log [L IR/?L ?(7.9 ?m)] = 0.80 ± 0.25 in AGNs with silicate absorption, and that log [L IR/?L ?(7.9 ?m)] = 0.51 ± 0.21 in AGNs with silicate emission. L IR for the most luminous absorption and emission AGNs are similar and 2.5 times larger than for the most luminous starbursts. AGNs have systematically flatter SEDs than starbursts or composites, but their dispersion in SEDs overlaps starbursts. Sources with the strongest far-infrared luminosity from cool dust components are composite sources, indicating that these sources may contain the most obscured starbursts.

Sargsyan, Lusine; Weedman, Daniel; Lebouteiller, Vianney; Houck, James; Barry, Donald; Hovhannisyan, Ashot; Mickaelian, Areg

2011-03-01

429

Instrumentation for Neutron Activation Analysis of Subsurface Composition of Mars and Moon  

NASA Astrophysics Data System (ADS)

The concept of instrumentation is presented, which uses the well known method of neutron activation analysis for determination of composition of subsurface material on Mars and on Moon. This instrumentation contains the pulsing neutron generator, which produces 1 microsecond long pulses of 14 MeV neutrons, the sensors of thermal and epithermal albedo neutrons and the detector of induced gamma-ray lines. Die away curves of induced neutron emission are shown to depend on the content of hydrogen in the soil, and these data allows to estimate the content of hydrogen (or water, or hydroxyl) and also to resolve the layering stratification of hydrogen bearing minerals. Data for gamma-ray lines, which could be induced either by in-elastic scattering or by capture reactions with neutrons, provides the composition of soil constituting elements of tested subsurface. The present design concept is discussed for the instrument DAN (Dynamic Albedo of Neutrons), which has been selected for NASA Mars Science Laboratory. Another similar instruments are also considered, which may be useful for studying elemental composition of Mars and Moon surfaces from the landing platforms.

Mitrofanov, I.

430

Investigation of coincidence techniques in prompt gamma neutron activation analysis  

Microsoft Academic Search

After configuring the proper electronic system to be used, the initial observations of the gamma-gamma coincidence approach were presented. These observations included hydrogen peak elimination, background and sum peak elimination, pulse pile up reduction, and two dimensional spectra. Three practical applications of the coincidence counting approach were presented in this work. The first application was performing elemental analysis for a

Walid A. Metwally

2003-01-01

431

Neutron Activation Analysis of Trace Elements in Lava  

NASA Astrophysics Data System (ADS)

The elemental compositions of lavas vary with the locations of the volcanoes from which they emerged. We have used neutron activa- tion analysis to measure the abundances of approximately 32 different elements in lava samples collected from three different Hawaiian islands and from the summit of Mt. Kilimanjaro. Two different neutron ir- radiations were performed at the McClellan Nuclear Radiation Center to optimize our sensitivities to both short- and long-lived radioisotopes. Gamma-ray counting was done at McClellan, UC Berkeley, and LBNL using large-volume high-purity Ge detectors. Results from the mea- surements will be presented and comparisons will be made between the trace-element compositions of the lavas from these different sites.

Meyer, Ross; Sabella, Jordan; Thomas, Keenan; Norman, Eric; Guillamon, P.; Goldman, I.; Smith, A.

2012-10-01

432

Electromagnetic activity of a pulsating paramagnetic neutron star  

Microsoft Academic Search

The fact that neutron star matter possesses the capability of maintaining a highly intense magnetic field has been and still\\u000a is among the most debatable issues in pulsar astrophysics. Over the years, there were several independent suggestions that\\u000a the dominant source of pulsar magnetism is either the field-induced or the spontaneous magnetic polarization of the baryon\\u000a material. The Pauli paramagnetism

S. I. Bastrukov; D. V. Podgainy; J. Yang; F. Weber

2002-01-01

433

Neutron-activation potassium-argon dating of meteorites  

Microsoft Academic Search

Argon analyses are presented for stepwise heating of nine specimens of seven neutron-irradiated meteorites, and potassium-argon ages calculated by the Ar 40 -Ar 39 method. Within the limitations of the data, it is found that the chondrites Karoonda, St. Severin and Allegan, and the aubrites Peña Bianca Spring and Bishopville, all have identical potassium-argon gas retention ages, assumed to be

Frank A. Podosek

1971-01-01

434

Iodine-129 separation and determination by neutron activation analysis  

SciTech Connect

A method is described for analysis of /sup 129/I in fission product mixtures originating from fuel reprocessing studies and low-level wastes. The method utilizes conventional iodine valence adjustment and solvent extraction techniques to chemically separate /sup 129/I from most fission products. The /sup 129/I is determined by neutron irradiation and measurement of the 12.4 h /sup 130/I produced by the neutron capture reaction. Special techniques were devised for neutron irradiation of /sup 129/I samples in the pneumatic tube irradiation facilities at the High Flux Isotope (HFIR) and Oak Ridge Research (ORR) Reactors. Chemically separated /sup 129/I is adsorbed on an anion exchange resin column made from an irradiation container. The loaded resin is then irradiated in either of the pneumatic facilities to produce /sup 130/I. Sensitivity of the analysis with the HFIR facility (flux: 5 x 10/sup 14/ n/cm/sup 2//sec) and a 100-second irradiation time is approximately 0.03 nanograms. Samples up to 250 ml in volume can be easily processed.

Bate, L.C.; Stokely, J.R.

1981-01-01

435

Determination of 232Th by neutron activation analysis using isotope-related ki factors.  

PubMed

Neutron activation analysis was applied to determine the 232Th activity in different matrices. Since in nature thorium consists of almost 100% of the long-lived 232Th, the instrumental trace element analysis method of neutron activation analysis can be applied to determine the thorium content in a sample. which can then be converted into the corresponding specitic activity. For the analysis about 100 mg of the sample was irradiated at a thermal neutron flux of phi(th) = 8 x 10(13) n.cm(-2) x s(-1). After irradiation the activity of the indicator nuclid 232Pa--produced by the (n,gamma) reaction--was measured by gamma spectrometry. The content of thorium was calculated using the activation equation and the isotope-related ki constant. Finally, the concentration of thorium in the sample was converted into the specific activity. The activities of 232Th measured by applying neutron activation analysis in different samples were compared with the results found by a spectrometry and gamma spectrometry for the daughter nuclides 228Ac and 224Ra. PMID:11843352

Küppers, G

2001-01-01

436

The Isotope Effect in Band Spectra, III. The Spectrum of Copper Iodide as Excited by Active Nitrogen  

Microsoft Academic Search

Excitation of spectra by active nitrogen.-Band spectra of CuF, CuCl, CuBr, and CuI have been obtained by the action of active nitrogen on the vapors of CuF2, CuCl and CuCl2, CuBr2, and CuI, using the method of Rayleigh and Fowler, as previously applied by them to CuCl. Certain additional heads are present in the red, probably due to CuO formed

Robert S. Mulliken

1925-01-01

437

Determinacao de hafnio e zirconio em materiais geologicos por analise por ativacao com neutrons. (Determination of hafnium and zirconium in geological materials by neutron activation analysis).  

National Technical Information Service (NTIS)

In this paper, neutron activation analysis was developed for determining hafnium and zirconium in geological materials. The USGS geological standard rocks GSP-1 (granodiorite) and W-1 (di abase). The Brazilian geological standards GB-1 (granite) and BB-1 ...

J. P. Lins

1992-01-01

438

Determination of the Capture to the Fission Cross-Sections Ratio by the Measurements of the Gamma-Rays Coincidence Multiplicity Spectra at Neutron Resonance Absorption by 235U  

NASA Astrophysics Data System (ADS)

The capture to the fission cross-sections ratio (alpha value) was investigated by the measurements of gamma-rays time-of-flight spectra from the first to fifteenth multiplicities on the 500 m flight path of the IBR-30 reactor. One has used a 16-sections scintillation detector with NaI(Tl) crystals and two metal samples of 0.00137 and 0.00411 at/b thicknesses (the content: 235U :238 U = 90% : 10%.) The multiplicity spectra of coincidence and the alpha values ? = ??/?f were obtained for 212 resolved resonances in the neutron energy region E=19-1260 eV and for energy groups over the range 20-2000 eV. The experimental alpha values were compared with the similar values calculated on a basis of evaluated data from different libraries using the model of neutron cross sections description in multilevel R-matrix approximation.

Grigoriev, Yu. V.; Sinitsa, V. V.; Mezentseva, Zh. V.; Popov, A. B.; Popov, Yu. P.; Ilchev, G.; Faikov-Stanzcyk, H.

2003-06-01

439

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

2011-04-22

440

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

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