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1

Gamma ray spectra and sensitivities for 14 MeV neutron activation analysis  

Microsoft Academic Search

The purpose of this study was to define experimentally the sensitivity of determination for 63 different elements by 14 MeV\\u000a neutron activation, with a 150 kV Cockroft-Walton accelerator at a neutron flux of 2·108 n·cm?2·sec?1 on the sample. The obtained gamma ray spectra are given, and the origin of the photopeaks observed are explained. A maximum\\u000a irradiation time of five

M. Cuypers; J. Cuypers

1968-01-01

2

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

3

THERMAL NEUTRON SPECTRA IN GRAPHITE  

Microsoft Academic Search

A pulsed, high-current, electron linear accelerator is used to excite ; thermal-neutron spectra in a graphite asemmbly. The steady-state energy spectra ; of neutrons are measured at several temperatures by pulsed-beam time-of-flight ; techniques. The measured spectra are compared with theoretical predictions which ; use free- and bound-carbon scattering kernels. The scattering kernel for carbon ; bound in graphite is

D. E. Parks; J. R. Beyster; N. F. Wikner

1962-01-01

4

Analysis of the errors in the reconstruction of neutron spectra measured by an activation method  

SciTech Connect

The authors conducted an investigation of nonuniqueness and the errors arising in the process of reconstruction of the neutron spectrum with the aid of an iterative algorithm proposed previously, called ITER. The results of the numerical experiment show that when reconstructing smooth spectra of the fission-spectrum type, as the initial approximation, more rigid spectra can be used. The error caused by the indeterminancy of the a priority information will not exceed 10% in the energy range well covered by the sensitivity functions of the reactions.

Voitov, A.I.; Poyarkov, V.A.; Sadovnikova, T.S.

1986-11-01

5

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

6

Mechanical approach to the neutrons spectra collimation and detection  

NASA Astrophysics Data System (ADS)

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

Sadeghi, H.; Roshan, M. V.

2014-11-01

7

Neutron sources and spectra from cold fusion  

Microsoft Academic Search

Deterministic methods are used to calculate the neutron and photon sources and spectra that would develop if fusion reactions were occurring in cold fusion experimental devices. The results from the calculations give the neutron and gamma spectra resulting from a 2.45-MeV and a 14.1 MeV neutron source. The neutron source strength from certain (gamma,n) and (alpha,n) reactions are also determined.

T. A. Parish; R. T. Perry; W. B. Wilson

1990-01-01

8

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

9

Spectra and Neutron Dosimetry Inside a PET Cyclotron Vault Room  

NASA Astrophysics Data System (ADS)

The neutron field around a PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Pairs of thermoluminescent dosemeters, TLD600 and TLD700, were used as thermal neutron detector inside a Bonner Spheres Spectrometer to measure the neutron spectra at three different positions inside the cyclotron's vault room. Neutron spectra were also determined by Monte Carlo calculations. The hardest spectrum was observed in front of cyclotron target and the softest was noticed at the antipode of target. Neutron doses derived from the measured spectra vary between 11 and 377 mSv/?A-h of proton integrated current, Doses were also measured with a single-moderator remmeter, with an active thermal neutron detector, whose response in affected by the radiation field in the vault room.

Vega-Carrillo, Héctor René; Méndez, Roberto; Iñiguez, María Pilar; Martí-Climent, Joseph; Peñuelas, Iván; Barquero, Raquel

2006-09-01

10

Spectra and Neutron Dosimetry Inside a PET Cyclotron Vault Room  

SciTech Connect

The neutron field around a PET cyclotron was investigated during 18F radioisotope production with an 18 MeV proton beam. Pairs of thermoluminescent dosemeters, TLD600 and TLD700, were used as thermal neutron detector inside a Bonner Spheres Spectrometer to measure the neutron spectra at three different positions inside the cyclotron's vault room. Neutron spectra were also determined by Monte Carlo calculations. The hardest spectrum was observed in front of cyclotron target and the softest was noticed at the antipode of target. Neutron doses derived from the measured spectra vary between 11 and 377 mSv/{mu}A-h of proton integrated current, Doses were also measured with a single-moderator remmeter, with an active thermal neutron detector, whose response in affected by the radiation field in the vault room.

Vega-Carrillo, Hector Rene [Unidades Academicas: Estudios Nucleares e Ing. Electrica. Universidad Autonoma de Zacatecas, A.P. 336, 98000 Zacatecas, Zac. Mexico (Mexico); Mendez, Roberto [Universidad Europea Miguel de Cervantes, Valladolid (Spain); Iniguez, Maria Pilar [Facultad de Ciencias de la Universidad de Valladolid, Valladolid (Spain); Marti-Climent, Joseph; Penuelas, Ivan [Servicio de Medicina Nuclear, Clinica Universitaria de la Universidad de Navarra (Spain); Barquero, Raquel [Hospital Universitario Rio Hortega, Valladolid (Spain)

2006-09-08

11

Gravitational effects on planetary neutron flux spectra  

NASA Astrophysics Data System (ADS)

The effects of gravity on the planetary neutron flux spectra for planet Mars, and the lifetime of the neutron, were investigated using a modified one-dimensional diffusion accelerated neutral-particle transport code, coupled with a multigroup cross-section library tailored specifically for Mars. The results showed the presence of a qualitatively new feature in planetary neutron leakage spectra in the form of a component of returning neutrons with kinetic energies less than the gravitational binding energy (0.132 eV for Mars). The net effect is an enhancement in flux at the lowest energies that is largest at and above the outermost layer of planetary matter.

Feldman, W. C.; Drake, D. M.; O'dell, R. D.; Brinkley, F. W.; Anderson, R. C.

1989-01-01

12

Neutron interactions and atomic recoil spectra  

SciTech Connect

This chapters presents a discussion of neutron interactions with materials that lead to activation, transmutation, and atomic displacements. The emphasis will be on current applications including neutron irradiation facilities, neutron dosimetry techniques, and computer codes for spectral adjustment and radiation damage calculations.

Greenwood, L.R.

1993-08-01

13

Dose spectra from energetic particles and neutrons  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

14

Hardness ratios of different neutron spectra.  

PubMed

Extensive data have been gathered in the past on the response of different detectors, based on the registration of neutron-induced fissions in bismuth, gold, tantalum and thorium by the spark-replica counter and the thin film breakdown counter. These detectors make it possible to exploit the excellent characteristics of the fission reactions for the measurements of high-energy neutrons. Most of the investigations have been carried out at the quasi-monoenergetic neutron beam facility at The Svedberg Laboratory-TSL of the Uppsala University in cooperation with the Khlopin Radium Institute (KRI). The responses of different fission detectors in the neutron energy range 35-180 MeV have been evaluated: a region where the predictive power of available nuclear reaction models and codes is not reliable yet. For neutron energy >200 MeV, the fission-detector responses have been derived from the data of the proton fission cross sections. By using the ratio of the responses of these detectors, a simple and accurate way to evaluate the spectrum hardness can be obtained, thus providing a tool to obtain spectral information needed for neutron dosimetry without the need to know the entire spectrum. Extensive data have been already obtained for the high-energy neutron spectrum from the CERN concrete facility. In the present paper, the measured values of the response ratios for different fissile detectors exposed at the CERN facility are compared with those calculated for the spectra from the same facility and from different altitudes in the atmosphere, respectively. PMID:15353650

Tommasino, L; Tripathy, S P

2004-01-01

15

Measured Delayed Neutron Spectra from the Fission of U-235 and Np237  

Microsoft Academic Search

Texas A&M University, in collaboration with Oak Ridge National Laboratory \\/ the Japan Atomic Energy Research Institute, have been actively studying the delayed neutron emission characteristics of the higher actinide isotopes for several years. 1-3 Recently, a proton recoil detector system was designed, built, and characterized for use in measuring delayed neutron energy spectra following neutron induced fission. The system

W. S. Charlton; C. Comfort; T. A. Parish; S. Raman

1998-01-01

16

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

17

Delayed Neutron Energy Spectra Following Fast Fission of Uranium  

NASA Astrophysics Data System (ADS)

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 neutrons for inducing fission in a ^{238} U lined fission chamber. The fission fragments were flushed via a helium jet stream to a well-shielded counting room where they were deposited onto a moving tape (magnetic audio tape) and transferred to a beta-neutron time-of-flight spectrometer. By adjusting the tape speed, composite delayed neutron time-of-flight spectra were measured for several different delay-time intervals. These measurements involved beta-neutron coincidences with ^6 Li-loaded glass scintillators for neutron energies from 10 keV to 450 keV and Bicron BC 501 liquid scintillators for the neutron energy range 200 keV-4 MeV. The measured composite delayed neutron energy spectra for ^{238}U are compared to the composite spectra for ^ {235}U and ^{239} Pu, and also to composite spectra derived for ^{238}U from the ENDF/B-VI database, which is based on summation calculations of individual precursor data supplemented by theoretical estimates. The composite spectra of ^{235}U and ^{239}Pu were obtained from previous measurements of delayed neutron spectra at this laboratory. The composite spectra are also decomposed into Keepin six-group spectra and compared with those for ^{239}Pu and ^{235}U. In addition, an equilibrium spectrum has been calculated from the measured composite spectra using several different analytical techniques and is also compared with the equilibrium spectrum of ^{238}U measured in an earlier study at this laboratory.

Villani, Marcel Franklin

18

DRAFT Deconvolution of Neutron Depth Profiling Spectra with Entropic Priors  

E-print Network

DRAFT Deconvolution of Neutron Depth Profiling Spectra with Entropic Priors Carlos C. Rodr@omega.albany.edu March 18, 1992 Abstract An iterative algorithm to deconvolve neutron depth profiling spectra is derived of impurities in a sample. General guidelines for computational experiments, to be designed in close contact

Rodriguez, Carlos

19

Neutron spectra around medical treatment facilities  

Microsoft Academic Search

The neutron field condition in and around the treatment room of the neutron therapy facility at the research reactor FRM in Garching-München was studied for radiation protection purposes. Neutron spectrometry was conducted by using a 15-channel multisphere spectrometer. From the unfolded spectral shapes, averaged dose conversion coefficients were derived and correction factors for the reading of two neutron monitors obtained.

H. Schraube; P. Kneschaurek; G. Schraube; F. M Wagner; E. Weitzenegger

2002-01-01

20

Activation neutron detector  

Microsoft Academic Search

An activation neutron detector made as a moulded and cured composition of a material capable of being neutron-activated is described. The material is selected from a group consisting of at least two chemical elements, a compound of at least two chemical elements and their mixture, each of the chemical elements and their mixture, each of the chemical elements being capable

T. S. Ambardanishvili; M. A. Kolomiitsev; T. Y. Zakharina; V. J. Dundua; N. V. Chikhladze

1976-01-01

21

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

PubMed

A method of experimentally obtaining both neutron and gamma-ray spectra in a scattering medium is described. The method utilizes a liquid-organic scintillator (NE-213) coupled with a pulse-shape discrimination circuit. This allows the separation of the neutron-induced pulse-height data from the gamma-ray pulse-height data. Using mathematical unfolding techniques, the two sets of pulse-height data were transformed to obtain the neutron and gamma-ray energy spectra. A small spherical detector was designed and constructed to reduce the errors incurred by attempting spectral measurements in a scattering medium. Demonstration of the utility of the system to obtain the neutron and gamma-ray spectra in a scattering medium was performed by characterizing the neutron and gamma-ray spectra at various sites about a 3.7-microgram (1.5 cm active length) californium-252 source in a tissue-equivalent medium. PMID:492077

Elson, H R; Stupar, T A; Shapiro, A; Kereiakes, J G

1979-01-01

22

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

23

Gamma-ray spectra from neutron capture on Sr  

Microsoft Academic Search

The gamma-ray spectrum following neutron capture on Sr was measured at 3 neutron energies: E\\/sub n\\/ = thermal, 2 keV, and 24 keV. Gamma rays were detected in a three-crystal Ge(Li)-NaI-NaI pair spectrometer. Gamma-ray intensities deduced from these spectra by spectral unfolding are presented.

R. E. Sullivan; J. A. Becker; M. L. Stelts

1981-01-01

24

Relativistically correct DD and DT neutron spectra  

NASA Astrophysics Data System (ADS)

We use relativistic kinematics to derive an expression for the energy spectrum of neutrons produced by fusion reactions in deuterium and deuterium-tritium thermal plasmas. The derivation does not require approximations and the obtained expression gives the exact shape of the spectrum. It is shown that the high-energy tail of the neutron spectrum is highly sensitive to the plasma temperature. Simple expressions for the plasma temperature as a function of the neutron spectrum full width at half maximum (FWHM) are given.

Appelbe, B.; Chittenden, J.

2014-06-01

25

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

PubMed Central

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

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

2009-01-01

26

Neutron Spectra and Dose Equivalent Inside Nuclear Power Reactor Containment.  

National Technical Information Service (NTIS)

The study was conducted to determine absorbed dose, dose-equivalent rates, and neutron spectra inside containment at nuclear power plants. The purpose of this study was: (1) measure dose-equivalent rates with various commercial types of rem meters, such a...

J. M. Aldrich

1981-01-01

27

THERMAL HYDRAULICS KEYWORDS: neutron activation,  

E-print Network

as a neutron source, and the detection of the induced 16 N activity in the flow was performed by two bismuth portable is the pulsed-neutron activation ~PNA! method. This method is based on the detection of radiationTHERMAL HYDRAULICS KEYWORDS: neutron activation, flow measurements, evaluation methods FLOWACT

Pázsit, Imre

28

Neutron emission profiles and energy spectra measurements at JET  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

29

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

30

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

31

Multisphere neutron spectra measurements near a high energy medical accelerator.  

PubMed

Photoneutron spectral measurements in the vicinity of a high energy medical accelerator have been performed. A LiI (Eu) scintillator and paired thermoluminescent dosimeters were used in conjunction with moderating multispheres to measure the neutron spectra. The photoneutron fluence rate, fluence lethargy, average energy, and quality factors have been calculated using a recursive unfolding algorithm. The dose rates and dose equivalent rates received by the patient and operators due to these neutrons have been estimated from these unfolded spectra. Doses predicted by a semi-empirical dose-equivalent model were compared to the measured values at each point. The dose equivalent rate to operators was found to be 1.9 x 10(-11) Sv MU(-1). PMID:9721837

Veinot, K G; Hertel, N E; Brooks, K W; Sweezy, J E

1998-09-01

32

The JET Neutron Activation System  

Microsoft Academic Search

The JET activation system provides the absolute value of the neutron yields as well as a check on the linearity of other neutron detector systems. The total neutron yield is standardized to one irradiation end reentrant in the top of the vessel, while the results from the other seven irradiation ends are normalized to this standard end and provide redundancy

A. L. Roquemore; L. Bertalot; B. Esposito; O. N. Jarvis; M. J. Loughlin; G. Sadler; P. van Belle

1997-01-01

33

Neutron activation for ITER  

SciTech Connect

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

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

1996-04-29

34

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

E-print Network

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

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

2014-01-01

35

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

E-print Network

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

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

2014-09-05

36

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

37

Emission Spectra of Fallback Disks Around Young Neutron Stars  

E-print Network

The nature of the energy source powering anomalous X-ray pulsars is uncertain. Proposed scenarios involve either an ultramagnetized neutron star, or accretion onto a neutron star. We consider the accretion model proposed recently by Chatterjee, Hernquist & Narayan, in which a disk is fed by fallback material following a supernova. We compute the optical, infrared, and submillimeter emission expected from such a disk, including both viscous dissipation and reradiation of X-ray flux impinging on the disk from the pulsar. We find that it is possible with current instruments to put serious constraints on this and on other accretion models of AXPs. Fallback disks could also be found around isolated radio pulsars and we compute the corresponding spectra. We show that the excess emission in the R and I bands observed for the pulsar PSR 0656+14 is broadly consistent with emission from a disk.

Rosalba Perna; Lars Hernquist; Ramesh Narayan

1999-12-15

38

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

39

Applications of neutron activation spectroscopy  

E-print Network

Since the discovery in 1932, neutrons became a basis of many methods used not only in research, but also in industry and engineering. Among others, the exceptional role in the modern nuclear engineering is played by the neutron activation spectroscopy, based on the interaction of neutron flux with atomic nuclei. In this article we shortly describe application of this method in medicine and detection of hazardous substances.

Silarski, M

2013-01-01

40

Absolute measurements of neutron spectra in high- and low-enriched uranium materials test reactor fuel  

Microsoft Academic Search

In this paper in-core absolute neutron spectra are measured for high-enriched uranium (HEU) and low-enriched uranium (LEU) materials which test reactor fuel using multiple foil activation. The measurements were made in special fuel elements configured to simulate a regular fuel element but that permitted reproducible insertion of a wide range of samples. The measured subcadmium LEU flux was 14% less

D. K. Wehe; J. Schmidt; J. S. King

1992-01-01

41

Absolute measurements of neutron spectra in high- and low-enriched uranium materials test reactor fuel  

SciTech Connect

In this paper in-core absolute neutron spectra are measured for high-enriched uranium (HEU) and low-enriched uranium (LEU) materials which test reactor fuel using multiple foil activation. The measurements were made in special fuel elements configured to simulate a regular fuel element but that permitted reproducible insertion of a wide range of samples. The measured subcadmium LEU flux was 14% less than the HEU fuel, which is within the experimental uncertainty of the 19% calculated value. There was no observed difference between the fast spectra. A separate spectral unfolding of just the LEU fast flux yielded reasonable agreement with proton-recoil measurements.

Wehe, D.K.; Schmidt, J.; King, J.S. (Univ. of Michigan, Dept. of Nuclear Engineering, Ann Arbor, MI (US))

1992-01-01

42

Experimental characterization of the neutron spectra generated by a high-energy clinical LINAC  

NASA Astrophysics Data System (ADS)

The production of unwanted neutrons by electron linear accelerators (LINACs) has attracted a special attention since the early 50s. The renewed interest in this topic during the last years is due mainly to the increased use of such machines in radiotherapy. Specially, in most of developing countries where many old teletherapy irradiators, based on 60Co and 137Cs radioactive sources, are being replaced with new LINAC units. The main objective of this work is to report the results of an experimental characterization of the neutron spectra generated by a high-energy clinical LINAC. Measurements were carried out, considering four irradiation configurations, by means of our recently developed passive Bonner sphere spectrometer (BSS) using pure gold activation foils as central detectors. This system offers the possibility to measure neutrons over a wide energy range (from thermal up to a few MeV) at pulsed, intense and complex mixed n-? fields. A two-step unfolding method that combines the NUBAY and MAXED codes was applied to derive the final neutron spectra as well as their associated integral quantities (in terms of total neutron fluence and ambient dose equivalent rates) and fluence-averaged energies.

Amgarou, K.; Lacoste, V.; Martin, A.

2011-02-01

43

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

NASA Astrophysics Data System (ADS)

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

Langford, Thomas J.

44

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

45

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

46

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

47

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

48

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

SciTech Connect

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

Kroc, T.K.; /Fermilab

2009-10-01

49

Measurement of neutron fluence spectra up to 150 MeV using a stacked scintillator neutron spectrometer.  

PubMed

A stacked scintillator neutron spectrometer (S3N) consisting of three slabs of liquid organic scintillator is described. A pulsed beam providing a broad spectrum of neutron energies is used to determine the detection efficiency of the spectrometer as a function of incident neutron energy and to measure the pulse height response matrix of the system. Neutron spectra can then be determined for beams with any kind of time structure by unfolding pulse height spectra measured by the S3N. Examples of fluence spectrum measurements in the energy range 20-150 MeV are presented. PMID:15353638

Brooks, F D; Allie, M S; Buffler, A; Dangendorf, V; Herbert, M S; Makupula, S A; Nolte, R; Smit, F D

2004-01-01

50

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

NASA Astrophysics Data System (ADS)

The energy spectra of neutrons were measured by a time-of-flight method for 120 GeV protons on thick graphite, aluminum, copper, and tungsten targets with an NE213 scintillator at the Fermilab Test Beam Facility. Neutron energy spectra were obtained between 25 and 3000 MeV at emission angles of 30°, 45°, 120°, and 150°. The spectra were parameterized as neutron emissions from three moving sources and then compared with theoretical spectra calculated by PHITS and FLUKA codes. The yields of the theoretical spectra were substantially underestimated compared with the yields of measured spectra. The integrated neutron yields from 25 to 3000 MeV calculated with PHITS code were 16-36% of the experimental yields and those calculated with FLUKA code were 26-57% of the experimental yields for all targets and emission angles.

Kajimoto, T.; Shigyo, N.; Sanami, T.; Iwamoto, Y.; Hagiwara, M.; Lee, H. S.; Soha, A.; Ramberg, E.; Coleman, R.; Jensen, D.; Leveling, A.; Mokhov, N. V.; Boehnlein, D.; Vaziri, K.; Sakamoto, Y.; Ishibashi, K.; Nakashima, H.

2014-10-01

51

Spectra  

NSDL National Science Digital Library

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

Exploratorium, The

2012-06-26

52

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

Microsoft Academic Search

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

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

1996-01-01

53

Neutron multiplicities and continuum neutron spectra from 200-MeV proton bombardment of carbon, aluminum, iron, lead, and uranium  

SciTech Connect

Double differential continuum neutron spectra from 200-MeV proton bombardment of carbon, aluminum, iron, lead, and uranium were measured at angles of 30, 45, 90, and 135 deg using pulse-shape discrimination (PSD) techniques. Data were obtained using different sizes of BC 501 detectors, 2 {times} 2, 5 {times} 5, and 5 {times} 10 in. Thin and thick data were compared with intranuclear cascade calculations and with the high-energy transport code (HETC). The total neutron yields were calculated from these neutron spectra. Comparison of experimental double differential neutron spectra results with the Monte Carlo calculation is good in general. However, noticeable differences are present at the high neutron energy region for some angles. The uncertainty in the experimental results is a combination of the statistical uncertainty in the neutron pulse height distribution measurement and errors introduced by the unfolding process, which resulted in spurious oscillations and some unphysical negative values during iteration that are in the acceptable range. The neutron multiplicities per incident proton are given in Table I. The double differential data were integrated by energy to obtain the angular distributions for the various angular data sets and for the angle integrated to give the total cross sections or neutron yields per proton for the various targets.

Nimnual, S.; Divadeenam, M.; Porter, R.; Tsoupas, N.; Ward, T.; Zucker, M. (Brookhaven National Laboratory, Upton, NY (USA)); Castaneda, C. (Univ. of California, Davis (USA)); Karowski, H.; Laird, C.

1989-11-01

54

Modifications to recursion unfolding algorithms to find more appropriate neutron spectra.  

PubMed

Modifications were made to recursion unfolding algorithms which allow the incorporation of prior knowledge, such as cutoff energy or preferred spectral shape, into the solution. Using these modifications, more appropriate neutron spectra are obtained. PMID:6548987

Lowry, K A; Johnson, T L

1984-10-01

55

Investigation of elemental analysis using neutron-capture gamma ray spectra  

E-print Network

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

Hamawi, John Nicholas

1969-01-01

56

Delayed neutron energy spectra following fast fission of [sup 238]U  

Microsoft Academic Search

Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of [sup 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 Graff accelerator to produce

Villani

1992-01-01

57

Spallation neutron spectra measurements Part II: Proton recoil spectrometer  

NASA Astrophysics Data System (ADS)

We present the experimental method conceived to measure high energy neutrons in the range (200 ? E ? 1600 MeV). The neutrons produce recoil protons in a liquid hydrogen converter. Momentum evaluation and identification of these protons are made by using a magnetic spectrometer equipped with plastic scintillators and three double-plane ( X- Y) wire chambers. The response functions of the apparatus are determined using quasi-monoenergetic neutron beams produced by the break-up of deuterons or 3He on a Be target. The performance of the apparatus is illustrated in the form of a preliminary neutron spectrum.

Martinez, E.; Thun, J.; Patin, Y.; Leray, S.; Beau, M.; Boudard, A.; Boué, F.; Bouyer, P.; Boyard, J. L.; Brochard, F.; Crespin, S.; Drake, D.; Duchazeaubeneix, J. C.; Durand, J. M.; Fréhaut, J.; Kowalski, L.; Legrain, R.; Lochard, J. P.; Ménard, S.; Milleret, G.; Petibon, E.; Plouin, F.; Terrien, Y.; Uematsu, M.; Vuillier, S.; Whittal, D. M.

1997-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

59

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

60

Calculation of neutron and gamma ray energy spectra for fusion reactor shield design: comparison with experiment  

Microsoft Academic Search

Integral experiments that measure the transport of approx. 14 MeV D-T neutrons through laminated slabs of proposed fusion reactor shield materials have been carried out. Measured and calculated neutron and gamma ray energy spectra are compared as a function of the thickness and composition of stainless steel type 304, borated polyethylene, and Hevimet (a tungsten alloy), and as a function

R. T. Santoro; R. G. Jr. Alsmiller; J. M. Barnes; G. T. Chapman

1980-01-01

61

Delayed neutron energy spectra following fast fission of [sup 238]U  

SciTech Connect

Delayed neutron energy spectra have been measured for six delay-time intervals following the fast fission of [sup 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 Graff accelerator to produce fast neutrons for inducing fission in a [sup 238]U lined fission chamber. The fission fragments were flushed via a helium jet stream to a well-shielded counting room where they were deposited onto a moving tape (magnetic audio tape) and transferred to a beta-neutron time-of-flight spectrometer. By adjusting the tape speed, composite delayed neutron time-of-flight spectra were measured for several different delay-time intervals. These measurements involved beta-neutron coincidences with [sup 6]Li-loaded glass scintillators for neutron energies from 10 keV to 450 keV and Bicron BC 501 liquid scintillators for the neutron energy range 200 keV-4 MeV. The measured composite delayed neutron energy spectra for [sup 238]U are compared to the composite spectra for [sup 235]U and [sup 239]Pu, and also to composite spectra derived for [sup 238]U from the ENDF/B-VI database, which is based on summation calculations of individual precursor data supplemented by theoretical estimates. The composite spectra of [sup 235]U and [sup 239]Pu were obtained from previous measurements of delayed neutron spectra at this laboratory. The composite spectra are also decomposed into Keepin six-group spectra and compared with those for [sup 239]Pu and [sup 235]U. In addition, an equilibrium spectrum has been calculated from the measured composite spectra using several different analytical techniques and is also compared with the equilibrium spectrum of [sup 238]U measured in an earlier study at this lab.

Villani, M.F.

1992-01-01

62

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

Microsoft Academic Search

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

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

1979-01-01

63

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

64

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

65

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

SciTech Connect

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 several polyethylene moderating spheres, are commonly used as a field neutron Spectrometer. A computer code must be used in tandem with the Bonner spheres to produce some approximate neutron spectrum from the sphere data by a technique known as spectral unfolding. The unfolding technique requires at least one of several available Bonner sphere response matrices. The choice of response matrix may strongly affect the end-product spectrum. This paper describes the comparison of the several response matrices currently available.

Lemley, E.C.; West, L.

1994-12-31

66

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

67

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

PubMed

We report on irradiation tests of InSb based Hall sensors at two irradiation facilities with two distinct types of neutron spectra. One was a fission reactor neutron spectrum with a significant presence of thermal neutrons, while another one was purely fast neutron field. Total neutron fluence of the order of 10(16)?cm(-2) was accumulated in both cases, leading to significant drop of Hall sensor sensitivity in case of fission reactor spectrum, while stable performance was observed at purely fast neutron spectrum. This finding suggests that performance of this particular type of Hall sensors is governed dominantly by transmutation. Additionally, it further stresses the need to test ITER candidate Hall sensors under neutron flux with ITER relevant spectrum. PMID:21033987

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

2010-10-01

68

Validation of computational methods for treatment planning of fast-neutron therapy using activation foil techniques  

SciTech Connect

A closed-form direct method for unfolding neutron spectra from foil activation data is presented. The method is applied to measurements of the free-field neutron spectrum produced by the proton-cyclotron-based fast-neutron radiotherapy facility at the University of Washington (UW) School of Medicine. The results compare favorably with theoretical expectations based on an a-priori calculational model of the target and neutron beamline configuration of the UW facility.

Nigg, D.W.; Wemple, C.A.; Hartwell, J.K.; Harker, Y.D.; Venhuizen, J.R. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States); Risler, R. [Univ. of Washington Medical Center, Seattle, WA (United States)

1997-12-01

69

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

NASA Technical Reports Server (NTRS)

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, Roger W.; Rajagopal, Mohan; Rogers, Forrest J.; Iglesias, Carlos A.

1995-01-01

70

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

PubMed

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

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

2011-11-01

71

Neutron Activation Analysis of Water - A Review  

NASA Technical Reports Server (NTRS)

Recent developments in this field are emphasized. After a brief review of basic principles, topics discussed include sources of neutrons, pre-irradiation physical and chemical treatment of samples, neutron capture and gamma-ray analysis, and selected applications. Applications of neutron activation analysis of water have increased rapidly within the last few years and may be expected to increase in the future.

Buchanan, John D.

1971-01-01

72

Active Neutron Shielding 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. Recent studies find that the few existing underground measurements of the fast, muon-induced neutron flux disagree at the 30%-50% level with predictions. Given this level of uncertainty, it is desirable to measure the neutron flux in-situ, as well as to reduce the number of neutrons incident on a dark matter detector. Towards these ends, we are developing a neutron veto system for both active and passive shielding. The goals of this R&D are (i) a measurement of the neutron energy spectrum underground above 10 MeV neutron kinetic energies, and (ii) measurements of the attenuation vs. energy of these neutrons in 1 meter of water, concrete, and liquid scintillator. These measurements will provide valuable input for simulation and design of shields for low-background experiments underground.

Monroe, Jocelyn; Yamamoto, Richard; Fisher, Peter; Cornell, Brett; Robinson, Mareena; Cowern, Dianna; Eyers, Richard; Henderson, Shawn

2009-05-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

75

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

NASA Astrophysics Data System (ADS)

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

Recktenwald, Geoff; Deinert, Mark

2010-03-01

76

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

77

Systematic Quantification of Uncertainties for Evaluated Prompt Fission Neutron Spectra and Multiplicities  

NASA Astrophysics Data System (ADS)

Uncertainties associated with evaluated average prompt fission neutron spectra and multiplicities are obtained for a suite of actinides in the Los Alamos model formalism. Systematics for the model input parameters are taken from the literature and used as prior values in a Bayesian updating procedure. Posterior systematics as well as associated posterior uncertainties are inferred. In addition, cross-isotope correlations are evaluated for the first time. The quantification of uncertainties associated with advanced Monte Carlo Hauser-Feshbach calculations of prompt fission neutron spectra is also discussed.

Talou, Patrick; Rising, Mike; Kawano, Toshihiko; Prinja, Anil

2012-05-01

78

Comparison of neutron spectra measured with three sizes of organic liquid scintillators using differentiation analysis  

NASA Technical Reports Server (NTRS)

Proton recoil distributions were obtained by using organic liquid scintillators of different size. The measured distributions are converted to neutron spectra by differentiation analysis for comparison to the unfolded spectra of the largest scintillator. The approximations involved in the differentiation analysis are indicated to have small effects on the precision of neutron spectra measured with the smaller scintillators but introduce significant error for the largest scintillator. In the case of the smallest cylindrical scintillator, nominally 1.2 by 1.3 cm, the efficiency is shown to be insensitive to multiple scattering and to the angular distribution to the incident flux. These characteristics of the smaller scintillator make possible its use to measure scalar flux spectra within media high efficiency is not required.

Shook, D. F.; Pierce, C. R.

1972-01-01

79

Measurement of Prompt Fission ?-ray Spectra in Fast Neutron-induced Fission  

NASA Astrophysics Data System (ADS)

Knowledge of prompt fission ?-ray emission has been of major interest in reactor physics for a few years. Since very few experimental spectra were ever published until now, new measurements would be also valuable to improve our understanding of the fission process. An experimental method is currently being developed to measure the prompt fission ?-ray spectrum from some tens keV up to 10 MeV at least. The mean multiplicity and total energy could be deduced. In this method, the ?-rays are measured with a bismuth germanate (BGO) detector which has the advantage to present a high P/T ratio and a high efficiency compared to other ?-ray detectors. The prompt fission neutrons are rejected by the time of flight technique between the BGO detector and a fission trigger given by a fission chamber or a scintillating active target. Energy and efficiency calibration of the BGO detector were carried out up to 10.76 MeV by means of the 27Al(p,?) reaction. First prompt fission ?-ray spectrum measurements performed for the spontaneous fission of 252Cf and for 1.7 and 15.6 MeV neutron-induced fission of 238U at the CEA, DAM, DIF Van de Graaff accelerator, will be presented.

Laborie, J.-M.; Belier, G.; Taieb, J.

80

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

NASA Technical Reports Server (NTRS)

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

1993-01-01

81

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

82

Theoretical description of prompt fission neutron multiplicity and spectra  

E-print Network

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

Cristian Manailescu

2014-10-16

83

Study of TFTR D-T neutron spectra using natural diamond detectors  

SciTech Connect

Three Natural Diamond Detector (NDD) based spectrometers have been used for neutron spectra measurement during Deuterium-Tritium (D-T) experiments using high power Neutral Beam Injection (NBI) and Ton Cyclotron Resonance Heating (ICRH) on the Tokamak Fusion Test Reactor (TFTR) in 1996. A 2-3 % energy resolution coupled with the high radiation resistance of NDDs (5 x 10{sup 14}n/cm{sup 2}) makes them ideal for measuring the D-T neutron spectra in the high radiation environment of TFTR tritium experiments. The compact size of the NDD made it possible to insert one of the detectors into one of the center channels of the TFTR multichannel neutron collimator to provide a vertical view perpendicular to the vessel midplane, Two other detectors were placed inside shields in TFTR test cell and provide measurements of the neutrons having angles of emission of 110- 180{degrees} and 60-12-{degrees} with respect to the direction of the plasma current. By using a 0.25 {mu}s shaping time of the Ortec 673 spectroscopy amplifier we were able to accumulate useful spectrometry data at count rates up to 1.5 x 10{sup 3} counts/sec. To model the D- T neutron spectra measured by each of three NDD`s the Neutron Source post TRANSP (NST) code and semi-analytical model were developed. A set of D-T and D-D plasmas is analyzed for the dynamics of D-T neutron spectral broadening for each of three NDD cones of view. The application of three NDD based D-T neutron -spectrometer array demonstrated the anisotropy of the ion distribution function. and provided a mature of the dynamics of the effective ion temperatures for each detector view, and determined the tangential velocity of resonant tritons during ICRH.

Roquemore, A.L. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Krasilnikov, A.V., Gorelenkov, N.N. [Troitsk Institute of Innovating and Fusion Researches, Moscow (Russia)

1996-12-31

84

Atmosphere models of magnetized neutron stars: QED effects, radiation spectra and polarization signals  

Microsoft Academic Search

Observations of surface emission from isolated neutron stars (NSs) provide unique challenges to theoretical modelling of radiative transfer in magnetized NS atmospheres. Recent work has demonstrated the critical role of vacuum polarization effects in determining NS spectra and polarization signals, in particular the conversion of photon modes (due to the `vacuum resonance' between plasma and vacuum polarization) propagating in the

M. van Adelsberg; Dong Lai

2006-01-01

85

Atmosphere Models of Magnetized Neutron Stars: QED Effects, Radiation Spectra and Polarization Signals  

Microsoft Academic Search

Observations of surface emission from isolated neutron stars (NSs) provide unique challenges to theoretical modeling of radiative transfer in magnetized NS atmospheres. Recent work has demonstrated the critical role of vacuum polarization effects in determining NS spectra and polarization signals, in particular the conversion of photon modes (due to the ``vacuum resonance'' between plasma and vacuum polarization) propagating in the

Matthew van Adelsberg; Dong Lai

2008-01-01

86

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

Microsoft Academic Search

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

Jeremy Smith; Krzysztof Kuczera; Martin Karplus

1990-01-01

87

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

88

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

2012-12-01

89

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

90

Neutron multiplicities and continuum neutron spectra from 200MeV proton bombardment of carbon, aluminum, iron, lead, and uranium  

Microsoft Academic Search

Double differential continuum neutron spectra from 200-MeV proton bombardment of carbon, aluminum, iron, lead, and uranium were measured at angles of 30, 45, 90, and 135 deg using pulse-shape discrimination (PSD) techniques. Data were obtained using different sizes of BC 501 detectors, 2 Ã 2, 5 Ã 5, and 5 Ã 10 in. Thin and thick data were compared with

S. Nimnual; M. Divadeenam; R. Porter; N. Tsoupas; T. Ward; M. Zucker; C. Castaneda; H. Karowski; C. Laird

1989-01-01

91

Theoretical description of prompt fission neutron multiplicity and spectra  

E-print Network

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

Manailescu, Cristian

2014-01-01

92

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

SciTech Connect

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

Damian, J. I. Marquez; Granada, J. R. [Neutron Physics Department and Instituto Balseiro, Centro Atomico Bariloche, CNEA (Argentina); Malaspina, D. C. [Department of Biomedical Engineering and Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 (United States)

2013-07-14

93

New calculations of the atmospheric cosmic radiation field--results for neutron spectra.  

PubMed

The propagation of primary cosmic rays through the Earth's atmosphere and the energy spectra of the resulting secondary particles have been calculated using the Monte Carlo transport code FLUKA with several novel auxiliary methods. Solar-modulated primary cosmic ray spectra were determined through an analysis of simultaneous proton and helium measurements made on spacecraft or high-altitude balloon flights. Primary protons and helium ions are generated within the rigidity range of 0.5 GV-20 TV, uniform in cos2theta. For a given location, primaries above the effective angle-dependent geomagnetic cut-off rigidity, and re-entrant albedo protons, are transported through the atmosphere. Helium ions are initially transported using a separate transport code called HEAVY to simulate fragmentation. HEAVY interfaces with FLUKA to provide interaction starting points for each nucleon originating from a helium nucleus. Calculated cosmic ray neutron spectra and consequent dosimetric quantities for locations with a wide range of altitude (atmospheric depth) and geomagnetic cut-off are presented and compared with measurements made on a high-altitude aeroplane. Helium ion propagation using HEAVY and inclusion of re-entrant albedo protons with the incident primary spectra significantly improved the agreement of the calculated cosmic ray neutron spectra with measured spectra. These cosmic ray propagation calculations provide the basis for a new atmospheric ionising radiation (AIR) model for air-crew dosimetry, calculation of effects on microelectronics, production of cosmogenic radionuclides and other uses. PMID:15353685

Clem, J M; De Angelis, G; Goldhagen, P; Wilson, J W

2004-01-01

94

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

95

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

96

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...

97

Neutron irradiation of superconductors and damage energy scaling of different neutron spectra  

SciTech Connect

Three different neutron sources were used to irradiate identical sets of NbTi superconductors up to about half the lifetime dose of a superconducting magnet in a fusion reactor. Based on a careful source characterization of the TRIGA Mark-II reactor in Vienna, the spallation neutron source IPNS at Argonne and the 14 MeV neutron source RTNS-II at Livermore, the damage energy cross sections were calculated for four different types of NbTi alloys (42, 46.5, 49 and 54 wt % Ti). The experimental results on the variations of critical current densities j/sub c/ with neutron dose are found to scale within the experimental uncertainties with the appropriate damage energy cross sections. This first explicit proof of damage energy scaling for j/sub c/-variations in superconductors is considered to be most valuable for the evaluation of radiation damage in superconductors under fusion reactor conditions. 12 refs., 5 figs., 2 tabs.

Hahn, P.A.; Weber, H.W.; Guinan, M.W.; Birtcher, R.C.; Brown, B.S.; Greenwood, L.R.

1985-08-01

98

Study on the unfolding algorithm for D-T neutron energy spectra measurement using recoil proton method  

E-print Network

A proton recoil method for measuring D-T neutron energy spectra using polyethylene film and Si (Au) surface barrier detector was presented. An iteration algorithm for unfolding the recoil proton energy spectrum to the neutron energy spectrum was investigated. The response matrixes R of polyethylene film at 0 degree and 45 degree were obtained by simulating the recoil proton energy spectra from the mono-energetic neutron using MCNP code. Under an assumed D-T neutron spectrum, the recoil proton spectra from polyethylene film at 0 degree and 45 degree were also simulated using MCNP code. Based on the response matrixes R and the simulated recoil proton spectra at 0 degree and 45 degree, the unfolded neutron spectra were respectively obtained using the iteration algorithm, and compared with the assumed neutron spectrum. The results show that the iteration algorithm method can be applied to unfold the recoil proton energy spectrum to the neutron energy spectrum for D-T neutron energy spectra measurement using recoi...

Wang, Jie; Yan, Yan; Wei, Zheng; Wang, Jun-Run; Ran, Jian-Ling; Huang, Zhi-Wu; Lan, Chang-Lin; Yao, Ze-en

2014-01-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

100

Study of neutron spectra emitted by moderated 241Am-Be source for various moderating materials by using simulation technique.  

PubMed

A study was done on the tailored neutron energy spectra of (241)Am-Be neutron source due to the effect of moderators. The (241)Am-Be laboratory neutron source was used as the basic source and the emitted spectrum was modified using various neutron moderators. The various moderators used are high-density polythene, light water, heavy water, graphite, (56)Fe, BeO, Be, (6)Li and (7)Li. The absolute energy spectra and fluences in each case are calculated by using the Monte Carlo code FLUKA. This paper describes the simulation work done to design a moderated (241)Am-Be neutron source to produce various energy neutron spectra. PMID:22128358

Kumari, N Sujatha; Sathian, V; Ghodke, S S; Singh, Yashoda; Mahant, A K; Ganesan, S

2012-06-01

101

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

NASA Astrophysics Data System (ADS)

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

Benck, S.; d'Errico, F.; Denis, J.-M.; Meulders, J.-P.; Nath, R.; Pitcher, E. J.

2002-01-01

102

Neutron counter based on beryllium activation  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

103

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

PubMed Central

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

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

2009-01-01

104

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

105

Application of artificial neural networks for unfolding neutron spectra by using a scintillation detector  

NASA Astrophysics Data System (ADS)

The unfolding of neutron spectra from the pulse height distribution measured by a BC501A scintillation detector is accomplished by the application of artificial neural networks (ANN). A simple linear neural network without biases and hidden layers is adopted. A set of monoenergetic detector response functions in the energy range from 0.25 MeV to 16 MeV with an energy interval of 0.25 MeV are generated by the Monte Carlo code O5S in the training phase of the unfolding process. The capability of ANN was demonstrated successfully using the Monte Carlo data itself and experimental data obtained from the Am-Be neutron source and D-T neutron source.

Yan, Jie; Liu, Rong; Li, Cheng; Jiang, Li; Wang, Mei

2011-03-01

106

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

107

Neutron and gamma spectra in delayed neutron decay of some fission products  

Microsoft Academic Search

From spring meeting of the Deutsche Physikalische Gesellschaft. Part A, ; nuclear physics; Heidelberg, Germany (19 Feb By use of fast radiochemical ; separation methods, (separation time: 24 sec), several short-lived isotopes of ; As, Se, Br, Te, and I were isolated from ²³⁵U fission products and ; identified as emitters of delayed neutrons. With the new high pressure, high

H. Folger; H. Franz; W. Grimm; G. Hermann; J. V. Kratz; K. L. Kratz; F. Nuh; S. G. Prussin

1973-01-01

108

Importance of Compton scattering to radiation spectra of isolated neutron stars  

E-print Network

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

V. Suleimanov; K. Werner

2006-12-22

109

Modifications to iterative recursion unfolding algorithms and computer codes to find more appropriate neutron spectra. Final report  

Microsoft Academic Search

Modifications were made to iterative recursion unfolding algorithms and computer codes which allow the incorporation of prior knowledge, such as cutoff energy or preferred spectral shape, into the solution. Using these modifications, more appropriate neutron spectra are obtained.

K. A. Lowry; T. L. Johnson

1984-01-01

110

Modifications to iterative recursion unfolding algorithms and computer codes to find more appropriate neutron spectra. Final report  

SciTech Connect

Modifications were made to iterative recursion unfolding algorithms and computer codes which allow the incorporation of prior knowledge, such as cutoff energy or preferred spectral shape, into the solution. Using these modifications, more appropriate neutron spectra are obtained.

Lowry, K.A.; Johnson, T.L.

1984-06-06

111

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, h ??(10) , range from 276 down to 16 pSv cm 2. 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

112

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

113

Activation analysis of indium, KCl, and melamine by using a laser-induced neutron source  

NASA Astrophysics Data System (ADS)

A laser-induced repetitively operated fast neutron source with a neutron yield of 4 × 105 n/pulse and a pulse repetition rate of 5 Hz, which was developed using a deuterated polystyrene film target and a 24-TW femtosecond laser, was applied for laser activation analyses of indium, KCl, and melamine samples. The nuclear reactions of the measured gamma spectra for the activated samples were identified as (n, ?), (n, n'), and (n, 2n) reactions. These indicate possible usage of the neutron source for practical activation analyses of various materials.

Lee, Sungman; Lee, Kitae; Cha, Hyungki

2014-04-01

114

Carbon activation diagnostic for tertiary neutron measurements  

NASA Astrophysics Data System (ADS)

The yield of tertiary neutrons with energies greater than 20 MeV has been proposed to determine the high ?R of inertial confinement fusion targets. The activation of carbon is a valuable measurement technique because of its high reaction threshold, the availability of high-purity samples, and relatively low cost. The 12C(n,2n)11C reaction has a Q value of 18.7 MeV, well above the 14.1 MeV primary DT neutron energy. The isotope 11C decays with a half-life of 20.3 min and emits a positron, resulting in the production of two back-to-back, 511 keV gamma rays upon annihilation. The positron decay of 11C is nearly identical to the copper decay used in the activation measurements of 14.1 MeV primary DT yields; therefore, the present copper activation gamma-detection system can be used to detect the tertiary-produced carbon activation. Because the tertiary neutron yield is more than six orders of magnitude lower than primary neutron yield, the carbon activation diagnostic requires ultrapure carbon samples, free from any positron-emitting contamination. In recent years we have developed carbon purification, packaging, and handling procedures that minimize the contamination signal to a level low enough to use carbon activation for tertiary neutron measurements in direct-drive implosion experiments with DT cryogenic targets on OMEGA. Experimental results of contamination measurements in carbon samples performed on high-neutron-yield shots on OMEGA in 2001-2002 will be presented. A concept for implementing a carbon activation system on the National Ignition Facility (NIF) will be discussed.

Glebov, V. Yu.; Stoeckl, C.; Sangster, T. C.; Meyerhofer, D. D.; Radha, P. B.; Padalino, S.; Baumgart, L.; Colburn, R.; Fuschino, J.

2003-03-01

115

Neutron activation analysis of arsenic species  

SciTech Connect

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

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

1993-01-01

116

Spectra  

NSDL National Science Digital Library

Spectra is a very informative website about how astronomers use spectra to understand what stars are made of, their structures, and their evolution. The page begins with an introduction to the electromagnetic spectrum and then goes into great detail about the properties of light. Then it talks about how matter both creates and destroys radiation. Then it discusses how to interpret absorption and emission lines. The website ends with how astronomers use spectra to understand stars, galaxies, other objects in the universe.

Kaler, James

2004-07-16

117

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

118

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

119

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

120

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

122

Model atmospheres and X-ray spectra of bursting neutron stars  

NASA Technical Reports Server (NTRS)

Model atmosphere equations are derived which correspond to plane-parallel nongray atmospheres of very hot neutron stars in hydrostatic and radiative equilibrium. The nonlinear transfer equation used implements an exact photon redistribution function which precisely traces even those scattering events having large photon-electron energy exchange. The numerical results thus obtained encompass tables of the surface fluxes for 20 model atmospheres whose T(eff) ranges from 6 to 30 million K. The spectra of high gravity models are virtually identical with the blackbody spectrum shifted toward higher energies, while models approaching the Eddington limit develop a large low-energy hump.

Madej, Jerzy

1991-01-01

123

Nondestructive examination using neutron activated positron annihilation  

DOEpatents

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

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

2001-01-01

124

Aspects of Precision and Accuracy in Neutron Activation Analysis  

E-print Network

Risø-R-419 Aspects of Precision and Accuracy in Neutron Activation Analysis Kaj Heydorn Risø Activation Analysis #12;Aspects of Precision and Accuracy in Neutron Activation Analysis Kaj Heydorn Isotope distributed around their true values. Such results may be produced by means of Neutron Activation Analysis

125

Influence of neutron spectra on the radiation-induced evolution of AISI 316  

SciTech Connect

A single heat of AISI 316 stainless steel has been irradiated in both the EBR-II and HFIR reactors. These reactors have significantly different spectra, leading to differences in displacements per neutron, helium/dpa ratio, and solid transmutant generation rates. The influence of reactor spectra can be observed in the transmutation-altered elemental compositions and the void densities. At least in the range of 500 to 650/sup 0/C there does not appear to be any significant spectral-related differences in the dislocation density, phase development or total swelling. It appears that, in this temperature range, the steady-state swelling rate per displaced atom that develops in this steel will be the same in fast and thermal reactors, as well as in projected fusion devices.

Brager, H R; Garner, F A

1981-08-01

126

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

127

Measurement of neutron energy spectra behind shielding of a 120 GeV/ c hadron beam facility  

NASA Astrophysics Data System (ADS)

Neutron energy spectra were measured behind the lateral shield of the CERF (CERN-EU High Energy Reference Field) facility at CERN with a 120 GeV/ c positive hadron beam (mainly a mixture of protons and pions) on a cylindrical copper target (7-cm diameter×50-cm long). NE213 organic liquid scintillator (12.7-cm diameter×12.7-cm long) was located at various longitudinal positions behind shields of 80- and 160-cm thick concrete and 40-cm thick iron. Neutron energy spectra in the energy range between 12 and 380 MeV were obtained by unfolding the measured pulse height spectra with the detector response functions which have been experimentally verified in the neutron energy range up to 380 MeV in separate experiments. The corresponding MARS15 Monte Carlo simulations generally gave good agreements with the experimental energy spectra.

Nakao, Noriaki; Taniguchi, Shingo; Rokni, Sayed H.; Roesler, Stefan; Brugger, Markus; Hagiwara, Masayuki; Vincke, Heinz; Khater, Hesham; Prinz, Alyssa A.

2006-06-01

128

Measurements of keV-neutron Capture Cross Sections and Capture Gamma-ray Spectra of Pd Isotopes  

NASA Astrophysics Data System (ADS)

The capture cross sections and capture gamma-ray spectra of 104,105,106,108,110Pd were measured in the neutron energy region from 15 to 100 keV. A neutron time-of-flight method was utilized by means of an anti-Compton NaI(Tl) spectrometer and a 1.5 nsec pulsed neutron source via the 7Li(p,n)7Be reaction. The capture yields were obtained by applying a pulse-height weighting technique to the net gamma-ray pulse-height spectra. The capture cross sections of 104,105,106,108,110Pd were determined with uncertainties of less than 6%, using the standard capture cross sections of 197Au. The capture gamma-ray spectra of 104,105,106,108,110Pd were also derived by unfolding the respective observed capture gamma-ray pulse-height spectra.

Terada, K.; Matsuhashi, T.; Hales, B.; Katabuchi, T.; Igashira, M.

2014-05-01

129

Measurements of delayed neutrons yields and time spectra from 1 GeV protons interacting with thick {sup nat}Pb targets  

SciTech Connect

This paper presents the preliminary results on measured delayed neutron (DN) yields and time spectra from 1 GeV protons interacting with thick {sup nat}Pb targets. In parallel, the MCNPX and PHTTS codes were used to predict the DN precursors and construct the theoretical DN tables. Different model parameters are examined and show significant dependence on the choice of the intra-nuclear cascade and fission-evaporation models used. These data and modeling are of great importance for the new generation spallation neutron sources based on liquid metal technologies where a significant amount of the DN precursor activity can be accumulated in the target fluid. (authors)

Ridikas, D. [CEA Saclay, DSM/DAPNIA, 91191 Gif-sur-Yvette (France); Barzakh, A. [Petersburg Nuclear Physics Inst., Leningrad district, 188350 Gatchina (Russian Federation); Blideanu, V.; David, J. C.; Dore, D. [CEA Saclay, DSM/DAPNIA, 91191 Gif-sur-Yvette (France); Fedorov, D. [Petersburg Nuclear Physics Inst., Leningrad district, 188350 Gatchina (Russian Federation); Ledoux, X. [CEA Bruyeres, DIF/DPTA, 91680 Bruyeres-le-Chatel (France); Moroz, F.; Panteleev, V. [Petersburg Nuclear Physics Inst., Leningrad district, 188350 Gatchina (Russian Federation); Plukis, A.; Plukiene, R. [Inst. of Physics, Savanoriu pr. 231, 02300 Vilnius (Lithuania); Prevost, A. [CEA Saclay, DSM/DAPNIA, 91191 Gif-sur-Yvette (France); Shcherbakov, O.; Vorobyev, A. [Petersburg Nuclear Physics Inst., Leningrad district, 188350 Gatchina (Russian Federation)

2006-07-01

130

Instrumental neutron activation analysis of Obsidian rock  

Microsoft Academic Search

An instrumental neutron activation analysis technique has been developed for the simultaneous determination of up to 30 elements\\u000a including major, minor and trace elements in Obsidian Rock (a proposed NBS-SRM-278). INAA method involves both short and long\\u000a irradiations followed by gamma-ray activity measurement with a Ge(Li) detector. The accuracy of the procedure has been checked\\u000a by analyzing IAEA Reference Materials.

S. Ahmad; M. S. Chaudhary; I. H. Qureshi

1981-01-01

131

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

132

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

NASA Astrophysics Data System (ADS)

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

Kasen, Daniel; Badnell, N. R.; Barnes, Jennifer

2013-09-01

133

Cross sections and differential spectra for reactions of 2-20 MeV neutrons of /sup 27/Al  

SciTech Connect

This report summarizes product yields, secondary n,p and ..cap alpha.. spectra, and ..gamma..-ray spectra calculated for incident neutrons of 2-20 MeV on /sup 27/Al targets. Results are all from the code ALICE, using the version ALISO which does weighting of results for targets which are a mix of isotopes. Where natural isotopic targets are involved, yields and n,p,..cap alpha.. spectra will be reported weighted over isotopic yields. Gamma-ray spectra, however, will be reported for the most abundant isotope.

Blann, M.; Komoto, T.T.

1988-01-01

134

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

Microsoft Academic Search

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 gamma spectra of short lived isotopes were interpreted with

N. Güngör; T. Tulun; A. Alemdar

1998-01-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

136

Estimated neutron-activation data for TFTR  

SciTech Connect

A systematic study has been initiated to address the overall neutron activation problem for the TFTR operation. The study consists of a sequence of investigation and calculation on (1) the specific activity for the elements; (2) the activation dose rate from isolated sample materials; (3) the global activation dose rate field; and (4) the streaming of delayed gamma-rays through penetrations during post-operational period. This report summarizes the important data essential to the first part of this sequence. A formula for calculating the specific activity for a pulsed machine is presented in an explicit form. Effective activation cross sections are tabulated using ten neutron flux distributions typical to the TFTR radiation environment. The specific activities and the delayed gamma-ray intensities for about forty naturally occurring elements are presented for the 5 days per run, 50 pulses per day operation at the TFTR vacuum vessel location. A list of specific activities for the same set of elements five years after a thousand typical TFTR pulses is also given.

Ku, L.P.; Kolibal, J.G.

1981-11-01

137

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

138

Neutron activation analysis applied to perspiration electrolytes  

E-print Network

. In the choice of the polyethylene sheeting used, nine commercial polyethylene sheets or bags were analyzed for their sodium content by neutron activation analysis. A small sax:. .pie of each material was weighed and then irradiated in the reactor for one... by the comparative analysis method must be accurately knocks. Since the required standard mass was quite small, about 30 micrograms of sodium, a direct weighing of the standard was beyond the capability of the weighing instrument available. Therefore a standard...

McAndrew, Robert Gavin

2012-06-07

139

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

PubMed

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

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

2014-10-01

140

Calibration and Unfolding of the Pulse Height Spectra of Liquid Scintillator-Based Neutron Detectors Using Photon Sources  

NASA Astrophysics Data System (ADS)

An accurate energy calibration of a 5? × 2? BC501A liquid scintillator-based neutron detector by means of photon sources and the unfolding of pulse height spectra are described. The photon responses were measured with 22Na, 137Cs and 54Mn photon sources and simulated using the GRESP code, which was developed at the Physikalisch Technische Bundesanstalt in Germany. Pulse height spectra produced by three different photon sources were employed to investigate the effects of the unfolding techniques. It was found that the four unfolding codes of the HEPRO and UMG3.3 packages, including GRAVEL, UNFANA, MIEKE and MAXED, performed well with the test spectra and produced generally consistent results. They could therefore be used to obtain neutron energy spectra in tokamak experiments.

Xie, Xufei; Yuan, Xi; Zhang, Xing; Fan, Tieshuan; Chen, Jinxiang; Li, Xiangqing

2012-06-01

141

A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA  

SciTech Connect

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

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

2010-09-10

142

Neutron-encoded signatures enable product ion annotation from tandem mass spectra.  

PubMed

We report the use of neutron-encoded (NeuCode) stable isotope labeling of amino acids in cell culture for the purpose of C-terminal product ion annotation. Two NeuCode labeling isotopologues of lysine, (13)C6(15)N2 and (2)H8, which differ by 36 mDa, were metabolically embedded in a sample proteome, and the resultant labeled proteins were combined, digested, and analyzed via liquid chromatography and mass spectrometry. With MS/MS scan resolving powers of ~50,000 or higher, product ions containing the C terminus (i.e. lysine) appear as a doublet spaced by exactly 36 mDa, whereas N-terminal fragments exist as a single m/z peak. Through theory and experiment, we demonstrate that over 90% of all y-type product ions have detectable doublets. We report on an algorithm that can extract these neutron signatures with high sensitivity and specificity. In other words, of 15,503 y-type product ion peaks, the y-type ion identification algorithm correctly identified 14,552 (93.2%) based on detection of the NeuCode doublet; 6.8% were misclassified (i.e. other ion types that were assigned as y-type products). Searching NeuCode labeled yeast with PepNovo(+) resulted in a 34% increase in correct de novo identifications relative to searching through MS/MS only. We use this tool to simplify spectra prior to database searching, to sort unmatched tandem mass spectra for spectral richness, for correlation of co-fragmented ions to their parent precursor, and for de novo sequence identification. PMID:24043425

Richards, Alicia L; Vincent, Catherine E; Guthals, Adrian; Rose, Christopher M; Westphall, Michael S; Bandeira, Nuno; Coon, Joshua J

2013-12-01

143

Atmosphere Models of Magnetized Neutron Stars: QED Effects, Radiation Spectra and Polarization Signals  

NASA Astrophysics Data System (ADS)

Observations of surface emission from isolated neutron stars (NSs) provide unique challenges to theoretical modeling of radiative transfer in magnetized NS atmospheres. Recent work has demonstrated the critical role of vacuum polarization effects in determining NS spectra and polarization signals, in particular the conversion of photon modes (due to the ``vacuum resonance'' between plasma and vacuum polarization) propagating in the density gradient of the NS atmosphere. Previous NS atmosphere models incorporated the mode conversion effect approximately, relying on transfer equations for the photon modes. Such treatments are inadequate near the vacuum resonance, particularly for magnetic field strengths around B~Bl~=7×1013 G, where the resonance occurs near the photosphere. In this proceeding, we describe our accurate treatment of the mode conversion effect in magnetized NS atmosphere models, employing both the modal radiative transfer equations coupled with the mode conversion probability at the vaccum resonance, and the full evolution equations for the photon Stokes parameters. In doing so, we are able to quantitatively calculate the effects of vacuum polarization on atmosphere structure, emission spectra, beam patterns, and polarizations for the entire range of magnetic field strengths, B = 1012-1015 G.

van Adelsberg, Matthew; Lai, Dong

2008-01-01

144

Instrumental neutron activation analysis of geological and pedological samples. Further investigation of epithermal neutron activation analysis using monostandard method  

Microsoft Academic Search

A comparative study is presented on neutron activation analysis of rock and soil samples using whole reactor neutron spectrum\\u000a and epithermal neutrons with both relative and monostandard procedures. The latter procedure used with epithermal neutron\\u000a activation analysis of soil samples necessitated the use of the “effective resonance integrals” which were determined experimentally.\\u000a The incorporation of the ? factor, representing deviation

A. Alian; B. Sansoni

1980-01-01

145

Studies of Neutron and Proton Nuclear Activation in Low-Earth Orbit 2  

NASA Technical Reports Server (NTRS)

The study of neutron and proton nuclear activation in low-Earth orbit reported in NASA CR-162051 has been continued with increasing emphasis given to primary and secondary neutron activation. The previously reported activation due to protons has been modified to include: (1) flux attenuation caused by all inelastic reactions; (2) the modification of the proton flux distribution caused by sample covering material; and (3) the activation of the sample as a function of the distance into the sample from the surface of incidence. A method has been developed for including the effects on the activation of the finite width and length of the samples. The reactant product spectra produced by proton-induced reactions has been studied. Cross sections needed for neutron induced reactions leading to long-lived (half-life 1 day) radioisotopes have been identified and, in some cases, compiled.

Laird, C. E.

1983-01-01

146

Neutron Energy Spectra in the Vicinity of a Nuclear Reactor Measured with a Liquid Scintillation Detector with Bismuth Shield  

NASA Astrophysics Data System (ADS)

A liquid scintillation spectrometer whose detector was composed of a NE213 liquid scintillator covered with a bismuth shield was constructed to estimate energy spectra of low intensity and relatively low energy neutrons around a nuclear reactor. A response matrix used for unfolding the pulse-height distributions was obtained from the matrices representing modulations of neutron energy spectra by the bismuth shield and response functions of the liquid scintillation detector. Measurements of reactor neutrons were carried out with the aid of the pulse-shape discrimination method in the vicinity of the Kinki University Reactor, UTR-KINKI. It became clear from the experiments that the pulse-height distributions by fission neutrons could be successfully obtained by the scintillation spectrometer constructed here in spite of the measurements in the low n/?ratio fields around nuclear facility and neutron energy spectra could be determined by the unfolding technique with the response matrix in the energy range from about 1 MeV to tens of MeV.

Urabe, Itsumasa; Sagawa, Hiroyuki; Ogawa, Yoshihiro; Kobayashi, Katsuhei

2003-06-01

147

Total body nitrogen analysis. [neutron activation analysis  

NASA Technical Reports Server (NTRS)

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

Palmer, H. E.

1975-01-01

148

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

NASA Astrophysics Data System (ADS)

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

Milocco, A.; Pillon, M.; Angelone, M.; Plompen, A.; Krása, A.; Trkov, A.

2013-08-01

149

Neutron activation analysis of Etruscan pottery  

SciTech Connect

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

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

1992-07-01

150

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

151

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

Microsoft Academic Search

The Heavy Water Neutron Irradiation Facility (HWNIF) of the Kyoto University Research Reactor (KUR) was updated in March 1996, mainly for the improvement in neutron capture therapy (NCT). A striking feature of the updated facility is that the energy spectrum of the neutron beam can be controlled from almost pure thermal to epi-thermal, within 5min by remote control under a

Yoshinori Sakurai; Tooru Kobayashi

2000-01-01

152

Thermal and epithermal neutron activation analysis using the monostandard method  

Microsoft Academic Search

A new approach is presented for neutron activation analysis using the monostandard (single comparator) method. Elements to\\u000a be determined are classified into two groups; those with ?o>Io are activated with whole neutron spectrum (without Cd-cover), using a standard of the same group (e.g. Sc), while elements\\u000a with Io>?o are activated with epithermal neutrons (under Cd-cover) using a standard of the

A. Alian; H.-J. Born; J. I. Kim

1973-01-01

153

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

SciTech Connect

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

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

2012-04-01

154

Neutron activation cross sections on lead isotopes  

SciTech Connect

The cross sections for the reactions {sup 204}Pb(n,n{sup '}{gamma}){sup 204}Pb{sup m}, {sup 204}Pb(n,2n){sup 203}Pb, {sup 204}Pb(n,2n){sup 203}Pb{sup m1}, {sup 204}Pb(n,3n){sup 202}Pb{sup m}, {sup 206}Pb(n,3n){sup 204}Pb{sup m}, {sup 206}Pb(n,{alpha}){sup 203}Hg, and {sup 208}Pb(n,p){sup 208}Tl 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 {sup 3}H(d,n){sup 4}He 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 {sup 27}Al(n,{alpha}){sup 24}Na reaction. Enriched samples were essential to determine the cross sections for the reactions with {sup 204}Pb{sup m} and {sup 206}Pb{sup m} isomers in the final state. Accurate results for reactions with {sup 204,206}Pb 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.; Quetel, C.; Sudar, S.; Vogl, J.; Koning, A. J.; Qaim, S. M.; Smith, D. L. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Nuclear Research and Consultancy Group NRG, P. O. Box 25, 1755 ZG Petten (Netherlands); Institut fuer Nuklearchemie, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany); Nuclear Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

2009-08-15

155

Neutron activation in EBT-P  

SciTech Connect

Neutron activation due to photoneutron production in the lead shields proposed to protect the EBT-P superconducting coils from excessive x-ray heating was investigated. The photoneutron flux distribution in various EBT-P structural components was calcualted for typical upgrade operating conditions using a standard twodimensional transport model (TWOTRAN). Activity levels were then evaluated for major structural materials using activation cross sections tabulated in the GAMMON library. Activation dose rates in the device enclosure following several days of 8h/day upgrade (90GHz) operation were found to be about6 mrem/h, decaying to <0.25 mrem/h in about3 days. This requires radition monitoring of all personnel entering the device enclosure during this time, but should not generally restrict ''hands on'' access to the device. There is thus no strong motivation to replace lead with another shield material; however, it may be desirable to borate the enclosure walls in order to reduce the effect which impurities might have on activity levels.

Driemeyer, D.E.

1983-09-01

156

Atmosphere models of magnetized neutron stars: QED effects, radiation spectra and polarization signals  

NASA Astrophysics Data System (ADS)

Observations of surface emission from isolated neutron stars (NSs) provide unique challenges to theoretical modelling of radiative transfer in magnetized NS atmospheres. Recent work has demonstrated the critical role of vacuum polarization effects in determining NS spectra and polarization signals, in particular the conversion of photon modes (due to the `vacuum resonance' between plasma and vacuum polarization) propagating in the density gradient of the NS atmosphere. Previous NS atmosphere models incorporated the mode conversion effect approximately, relying on transfer equations for the photon modes. Such treatments are inadequate near the vacuum resonance, particularly for magnetic field strengths around B ~ Bl ~= 7 × 1013 G, where the vacuum resonance occurs near the photosphere. In this paper, we provide an accurate treatment of the mode conversion effect in magnetized NS atmosphere models, employing both the modal radiative transfer equations coupled with an accurate mode conversion probability at the vacuum resonance, and the full evolution equations for the photon Stokes parameters. In doing so, we are able to quantitatively calculate the effects of vacuum polarization on atmosphere structure, emission spectra and beam patterns, and polarizations for the entire range of magnetic field strengths, B = 1012-1015 G. In agreement with previous works, we find that for NSs with magnetic field strength B >~ 2Bl, vacuum polarization reduces the widths of spectral features, and softens the hard spectral tail typical of magnetized atmosphere models. For B <~ Bl/2, vacuum polarization does not change the emission spectra, but can significantly affect the polarization signals. Our new, accurate treatment of vacuum polarization is particularly important for quantitative modelling of NS atmospheres with `intermediate' magnetic fields, B ~= (0.5-2)Bl. We provide fitting formulae for the temperature profiles for a suite of NS atmosphere models with different field strengths, effective temperatures and chemical compositions (ionized H or He). These analytical profiles are useful for direct modelling of various observed properties of NS surface emission. As an example, we calculate the observed intensity and polarization light curves from a rotating NS hotspot, taking into account the evolution of photon polarization in the magnetosphere. We show that vacuum polarization induces a unique energy-dependent linear polarization signature, and that circular polarization can be generated in the magnetosphere of rapidly rotating NSs. We discuss the implications of our results to recent observations of thermally emitting isolated NSs and magnetars, as well as the prospects of future spectral and polarization observations.

van Adelsberg, M.; Lai, D.

2006-12-01

157

Spectra of $gamma$-rays from capture of 2 eV to 9 x 10 eV neutrons by ¹¹Ta  

Microsoft Academic Search

Using new experimental techniques, the spectra of $gamma$-rays from the ; capture of neutrons by ¹¹Ta were measured at the Livermore 100-MeV linac ; for neutrons from 2 eV to 9 x 10 eV with a (Ge(Li)-NaI) three-crystal ; spectrometer. Individual primary $gamma$-ray lines were resolved to 1778-keV ; excitation in ¹²Ta. Neutron resonances were resolved to 200-eV neutron ;

Stelts

1976-01-01

158

NEUTRON ACTIVATION ANALYSIS OF ALUMINUM IN POSTMORTEM HUMAN LUNG TISSUE  

Microsoft Academic Search

Neutron activation analysis was used to assay trace quantities of aluminum in post- mortem human lung tissue samples. Dried accurately weighed lung tissue samples were activated in a 3.3 x 1()13 neutrons\\/cm2\\/sec thermal neutron flux and analyzed using a lithium- drifted germanium detector and 4096 channel gamma spectrophotometer. The 1778 kcv gamma photon emitted by Al28 was quantified using the

KELLY MANTIS; G. R. NORRIS

1973-01-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

160

Instrumental neutron activation analysis of Na in biological materials  

Microsoft Academic Search

Sodium contents in seven mixtures of biological materials from varying aliquants of wheat flour and oyster tissue were analyzed using the INAA (instrumental neutron activation analysis) method. The samples were activated in the thermal column (TC) of the 1 MW TRIGA reactor at our laboratory. To analyze and compare the measured results, the ratioa of the epithermal neutron flux to

L.-Y Sun; M. R. Conrady; R. A. Schmitt

1984-01-01

161

Trace Analysis of Ancient Gold Objects Using Radiochemical Neutron Activation  

E-print Network

Radiochemical neutron activation analysis has been applied to investigate the microelements in gold samples with archaeological importance. Chemical separation has allowed the determination of traces of Ir, Os, Sb, Zn, Co, Fe, Ni. Instrumental neutron activation analysis has been used for the determination of Cu.

Agata Olariu; Mioara Constantinescu; O. Constantinescu; T. Badica; I. V. Popescu; C. Besliu; Doina Leahu

1999-08-19

162

Herschel/SPIRE Submillimeter Spectra of Local Active Galaxies  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

163

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

SciTech Connect

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

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

2013-05-01

164

Mineral exploration and soil analysis using in situ neutron activation  

USGS Publications Warehouse

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

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

1966-01-01

165

Application of Different Orthonormal Expansion Methods to Neutron Measurements. III. Actual Measurements of Spectra and Dose Equivalent Rates  

Microsoft Academic Search

Neutron spectra and dose equivalent rates were measured with a BF3 proportional counter covered with two, three or five of 0-, 3.5-, 4.5-, 6.5-, 8.5- and 14.0-cm-thickness paraffin moderators. The dose equivalent rates were also measured with a ``Remcounter'' having two detectors, one of which consists of a BF3 counter centered in 30-cm-diameter paraffin cylinder and the other of three

Hiroshi Ryufuku; Hatsumi Tatsuta; Takashi Shirotani

1966-01-01

166

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

168

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

169

Neutron activation analysis of some building materials  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

170

Neutron activation analysis of arsenic in Greece  

SciTech Connect

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

Grimanis, A.P.

1989-11-01

171

Gamma spectra from ²³³U, ²³⁵U, and ²³⁹Pu during thermal neutron irradiation. [Reaction mechanisms not distinguished  

Microsoft Academic Search

The gamma spectra from three fissionable isotopes, ²³³U, ²³⁵U, and ²³⁹Pu, were measured during neutron irradiation in the thermal column of the Omega West Reactor. The measurements were preceded by a neutron irradiation of at least 20,000 s to build up a near-equilibrium concentration of the shorter half-life fission products. The measurements provide the total gamma spectra and do not

P. J. Bendt; E. T. Jurney

1978-01-01

172

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

173

Study of proton and neutron activation of metal samples in low Earth orbit  

NASA Technical Reports Server (NTRS)

The analysis of the gamma-ray spectra taken from samples flown in Spacelab 1; the search for and review of neutron and proton activation cross-sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; additional calculations of neutron induced activation for the LDEF samples; the data analysis plan for the LDEF and Spacelab 2 samples; the measurement of relevant cross-sections with activation of samples of V, Co, In, and Ta at the Indiana University Cyclotron Facility; and the preparation of an extended gamma-ray calibration source through the development of a proper technique to accurately deposit equal quantities of radioactive material onto a large number of point on the source are discussed.

Laird, C. E.

1984-01-01

174

Study of proton and neutron activation of metal samples in low Earth orbit  

NASA Technical Reports Server (NTRS)

Progress in the following activities has been made: the analysis of the gamma ray spectra taken from samples flown in Spacelab 2; the search for and review of neutron and proton activation cross sections needed to analyze the results of the Long Duration Exposure Facility (LDEF) activation measurements; the consideration given to data analysis of the LDEF and Spacelab 2 samples; the plan to measure relevant cross sections with nuclear accelerator measurements; and the preparation of an extended gamma ray calibration sources continues through planning and direct measurement of gamma ray efficiency for a Ge(Li) as a function of position along the surface of the detector housing.

Laird, C. E.

1984-01-01

175

Neutron activation analysis at the Californium User Facility for Neutron Science  

SciTech Connect

The Californium User Facility (CUF) for Neutron Science has been established to provide {sup 252}Cf-based neutron irradiation services and research capabilities including neutron activation analysis (NAA). A major advantage of the CUF is its accessibility and controlled experimental conditions compared with those of a reactor environment The CUF maintains the world`s largest inventory of compact {sup 252}Cf neutron sources. Neutron source intensities of {le} 10{sup 11} neutrons/s are available for irradiations within a contamination-free hot cell, capable of providing thermal and fast neutron fluxes exceeding 10{sup 8} cm{sup {minus}2} s{sup {minus}1} at the sample. Total flux of {ge}10{sup 9} cm{sup {minus}2} s{sup {minus}1} is feasible for large-volume irradiation rabbits within the {sup 252}Cf storage pool. Neutron and gamma transport calculations have been performed using the Monte Carlo transport code MCNP to estimate irradiation fluxes available for sample activation within the hot cell and storage pool and to design and optimize a prompt gamma NAA (PGNAA) configuration for large sample volumes. Confirmatory NAA irradiations have been performed within the pool. Gamma spectroscopy capabilities including PGNAA are being established within the CUF for sample analysis.

Martin, R.C.; Smith, E.H.; Glasgow, D.C. [Oak Ridge National Lab., TN (United States); Jerde, E.A. [Oak Ridge Research Inst., TN (United States); Marsh, D.L. [Univ. of Tennessee, Knoxville, TN (United States); Zhao, L. [Univ. of Texas, Austin, TX (United States)

1997-12-01

176

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

177

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

178

Activation measurements of fast neutron radiative capture for 139La  

NASA Astrophysics Data System (ADS)

The neutron capture cross section of the neutron magic isotope 139La has been measured relative to that of 27Al by means of the activation method. The fast neutrons were produced via the 3H(d,n)4He reaction on Pd-300 neutron generator. The natural high-purity La2O3 powder was used as target material. Induced gamma activities were measured by a high-resolution gamma-ray spectrometer with high-purity germanium (HPGe) detector. Measurements were corrected for gamma-ray attenuations, random coincidence (pile-up), dead time and fluctuation of neutron flux. The new values for En=13.5±0.2, 14.1±0.2, and 14.8±0.2 MeV are found to be 1.30±0.08, 1.15±0.08 and 0.99±0.07 mb, respectively. Results were discussed and compared with some corresponding values found in the literature.

Luo, Junhua; Han, Jiuning; Liu, Rong; Jiang, Li; Liu, Zhenlai; Sun, Guihua; Ge, Suhong

2013-05-01

179

Neutron ages computed from experimental activation data  

NASA Technical Reports Server (NTRS)

Computer program reduces time manually required to compute neutron age and to provide definite plan of procedural choices. Program allows convenient comparison of several fitting and error analysis procedures. Program code provides for error estimation of various integration options.

Semler, T. T.

1970-01-01

180

A new active thermal neutron detector.  

PubMed

This communication presents the main results about the design and in-house fabrication of a new solid-state neutron detector, which produces a DC output signal proportional to the thermal neutron fluence rate. The detector has been developed within the framework of the 3-y project NESCOFI@BTF of INFN (CSN V). Due to its sensitivity, photon rejection, low cost and minimum size, this device is suited to be used in moderator-based spectrometers. PMID:24345462

Bedogni, R; Bortot, D; Pola, A; Introini, M V; Gentile, A; Esposito, A; Gómez-Ros, J M; Palomba, M; Grossi, A

2014-10-01

181

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

182

Neutron-activation analysis applied to copper ores and artifacts  

NASA Technical Reports Server (NTRS)

Neutron activation analysis is used for quantitative identification of trace metals in copper. Establishing a unique fingerprint of impurities in Michigan copper would enable identification of artifacts made from this copper.

Linder, N. F.

1970-01-01

183

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

184

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

185

Instrumental Neutron Activation Analysis and Multivariate Statistics for Pottery Provenance  

Microsoft Academic Search

The application of instrumental neutron activation analysis and multivariate statistics to archaeological studies of ceramics\\u000a and clays is described. A small pottery data set from the Nasca culture in southern Peru is presented for illustration.

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

2004-01-01

186

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

PubMed

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

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

2014-10-01

187

Epithermal neutron activation analysis using a boron carbide irradiation filter  

Microsoft Academic Search

The use of boron carbide as a thermal neutron filter in epithermal neutron activation (ENAA) analysis has been investigated.\\u000a As compared to the use of a cadmium filter, boron provides a greater reduction of activities from elements relatively abundant\\u000a in terrestrial rocks and fossil fuels, such as Na, La, Sc and Fe. These elements have excitation functions which follow the

W. D. Ehmann; J. Brückner; D. M. McKown

1980-01-01

188

Magnetospheric Birefringence Induces Unique Polarization Signatures in Neutron-Star Spectra  

E-print Network

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

R. M. Shannon; Jeremy S. Heyl

2004-10-22

189

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

190

Fast neutron detection with germanium detectors: Unfolding the 692 keV peak response for fission neutron spectra  

Microsoft Academic Search

A new method is proposed for obtaining information on the spectral distribution of fast fission neutrons in the energy range from 0.7 MeV up to about 6 MeV from the shape of the Ge 692 keV inelastic scattering peak response e.g. in the pulse-height distribution measured with a portable Ge detector. In order to reduce photon background events, a lead

G. Fehrenbacher; R. Meckbach; H. G Paretzke

1997-01-01

191

Measurement of fast neutron spectra from the interaction of 20 MeV protons with thick Be and C targets using CR-39 detector  

NASA Astrophysics Data System (ADS)

Fast neutron spectral yield from the interaction of 20 MeV protons with thick Be and C targets are measured using CR-39 detectors. An image analysing program (autoTRAK_n) dedicated for neutron spectrum generation and dose estimation is developed based on the analysis of greylevel variations within each track and is used in the present study. The most important parameters for neutron spectrometry, i.e., track depth (length) and angle of all neutron-induced recoil tracks are determined using autoTRAK_n. The methodology is tested successfully to reproduce the spectra of some standard neutron sources which was reported earlier. In this study, autoTRAK_n is applied to generate neutron spectra from the above mentioned reactions, i.e., 9Be(p, n), 12C(p, n) and the neutron yields (total number of neutrons per projectile) for both the reactions are determined by folding the track density with the detector response. The dose equivalents and H?(10)-to-fluence ratios are also estimated. All these quantities are automatically obtained from the program. The neutron yield and the dose equivalent for 9Be(p, n) reaction are found to be about 4 times higher than that for 12C(p, n) reaction. The present methodology for neutron spectrum generation is found to be simple and effective and does not involve the complex spectrum unfolding procedures.

Tripathy, S. P.; Paul, S.; Sahoo, G. S.; Suman, V.; Sunil, C.; Joshi, D. S.; Bandyopadhyay, T.

2014-01-01

192

Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics  

SciTech Connect

The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroelectric instability, phonon spectra in PbTe exhibit a more anharmonic character. This behavior is reproduced in first-principles calculations of the temperature-dependent phonon self-energy. Our simulations reveal how the nesting of phonon dispersions induces prominent features in the self-energy, which account for the measured INS spectra and their temperature dependence. We establish that the phase-space for three-phonon scattering processes, rather than just the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optical ferroelectric mode.

Li, Chen [ORNL] [ORNL; Ma, Jie [ORNL] [ORNL; May, Andrew F [ORNL] [ORNL; Cao, Huibo [ORNL] [ORNL; Christianson, Andrew D [ORNL] [ORNL; Ehlers, Georg [ORNL] [ORNL; Singh, David J [ORNL] [ORNL; Sales, Brian C [ORNL] [ORNL; Delaire, Olivier A [ORNL] [ORNL

2014-01-01

193

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

194

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

195

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

NASA Astrophysics Data System (ADS)

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

Murphy, T. J.

2014-07-01

196

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

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

197

Reactor neutron activation analysis by a triple comparator method  

Microsoft Academic Search

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

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

1969-01-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

199

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

200

Influence of defects formed by fast reactor neutrons on exciton luminescence spectra of cadmium sulfide single crystals  

SciTech Connect

The influence of clusters of defects formed by irradiation with neutrons in CdS single crystals on parameters of the spectra of exciton photoluminescence at T {approx} 4.2 K has been studied. It is experimentally established that irradiation of the samples with fast reactor neutrons with energies E {approx} 1 MeV and dose {Phi} = 3 x 10{sup 18} cm{sup -2} brings about a decrease (by approximately 50 times) in the intensity of lines of exciton photoluminescence I{sub 1} ({lambda}{sub m} = 488.7 nm), I{sub 2} ({lambda}{sub m} = 486.9 nm), and I{sub 3} ({lambda}{sub m} = 486.3 nm) with redistribution of intensities in favor of the lines I{sub 1} and I{sub 3} and an increase in their half-width from 2 to 5-6 the positions of their peaks in the emission spectrum. Observed experimental facts are explained on the basis of a model of a two-phase system composed of slightly damaged region in the CdS single crystal in which clusters of defects (formed as a result of irradiation with neutrons) are embedded; these clusters are nanosized grains with a highly disordered structure.

Davidyuk, G. E.; Bogdanyuk, N. S.; Bozhko, V. V.; Kevshyn, A. H., E-mail: Kevshin_A@ukr.net [Volyn National University, Department of Solid-State Physics (Ukraine); Manzhara, V. S. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine); Kazukauskas, V. [Institute of Applied Research and Vilnius University (Department of Semiconductor Physics) (Lithuania)

2010-09-15

201

Neutron Spectra Measured with Time-of-Flight Detectors at the National Ignition Facility  

NASA Astrophysics Data System (ADS)

Neutron time-of-fight (nTOF) instruments are used to provide data on the performance of National Ignition Facility fusion experiments. nTOF detectors are used to measure the total neutron emission, temperature of the fuel, time of peak emission (bang time), and areal density of the compressed fuel (?R). These instruments are precision diagnostics with sufficient dynamic range and high signal-to-noise so that the neutron spectrum from inertial confinement fusion implosions can be measured. This talk will focus on data from the scintillation detectors located at 20 m. Analysis techniques using both time-domain and energy-domain data are discussed. The next-generation detector based on an organic crystal scintillator show that improvements to scintillator decay, recording fidelity, and reduced scattering from the housing improve the precision of the neutron spectral measurement. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC52-08NA28302.

Knauer, J. P.; Glebov, V. Yu.; Stoeckl, C.; Sangster, T. C.; Meyerhofer, D. D.; Caggiano, J. A.; Moran, M. J.; Hatarik, R.; McNaney, J. M.; Friedrich, S.; Bond, E. J.; Eckart, M. J.; Padalino, S. J.; Kilkenny, J. D.

2011-11-01

202

Measurement of the Thick Target Be(p,n) Neutron Energy Spectra W. B. Howard  

E-print Network

as a treatment for various types of cancer including glioblastoma multiforme, a form of brain cancer, and metastatic melanoma in the brain [1]. More recently, the potential for treating rheumatoid arthritis that is the target with this treatment modality. Both BNCT and BNCS require a large flux of thermal neutrons

Massey, Thomas N.

203

THERMAL AND EPITHERMAL NEUTRON ACTIVATION IN A THICK STEEL SLAB  

Microsoft Academic Search

The activation of gold, indium, and nickel foils by neutrons originating ; in a fission source was investigated within a nine-inch steel slab and in water ; and polyethylene following the steel. The measurements indicate a large ; epithermal activation in the steel so that the insertion of layers containing ; boron at thc boundaries of the steel effected only

R. D. Schamberger; A. N. Fasano

1957-01-01

204

INTRODUCTION Neutron activation analysis was applied to the problem  

E-print Network

#12;#12;#12;#12;INTRODUCTION Neutron activation analysis was applied to the problem frequent drainage operations, secondly, the work done by Mejia (2) indicated that activation analysis might analysis for manganese in several thousands samples from along the nowthwest coastline of Europe. In order

Gilbes, Fernando

205

Activation of high- T c superconductors with neutron irradiation  

Microsoft Academic Search

Activation due to nuclear transmutation is a very important factor for feasibility evaluation on the improvement of superconducting property by neutron irradiation. In this paper, the activation of Bi2Sr2CaCu2O8+x (Bi-2212) superconductor was evaluated by the activation analysis and calculation using ORIGEN-JR computer code. The activation analysis was carried out to determine the composition and impurity concentrations of the specimen. Then,

Makito Nakano; Kouji Ogikubo; Takayuki Terai; Michio Yamawaki; Taiji Hoshiya

2002-01-01

206

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

207

Surface-enhanced Raman scattering spectra of tomato epidermis on gold/ silver sol active substrate  

NASA Astrophysics Data System (ADS)

In this paper, tomato epidermis' surface-enhanced Raman scattering spectra were measured on gold and silver active substrates and analyzed. Preparing and using gold sol and silver sol in similar particle diameters (about 50-60nm), three comparable Raman spectra were obtained. Silver sol and gold sol can both increase Raman scattering signal of tomato epidermis. Through the Raman spectra, silver sol has greater enhancement ability than gold sol to tomato epidermis.

Zhang, Wei; Chen, Zhenyi; Chen, Na; Hu, Ling; Zhu, Hongfei; Liu, Shupeng; Guo, Qiang

2011-12-01

208

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

209

Workplace testing of the new single sphere neutron spectrometer based on Dysprosium activation foils (Dy-SSS)  

NASA Astrophysics Data System (ADS)

A photon insensitive passive neutron spectrometer consisting of a single moderating polyethylene sphere with Dysprosium activation foils arranged along three perpendicular axes was designed by CIEMAT and INFN. The device is called Dy-SSS (Dy foil-based Single Sphere Spectrometer). It shows nearly isotropic response in terms of neutron fluence up to 20 MeV. The first prototype, previously calibrated with 14 MeV neutrons, has been recently tested in workplaces having different energy and directional distributions. These are a 2.5 MeV nearly mono-chromatic and mono-directional beam available at the ENEA Frascati Neutron Generator (FNG) and the photo-neutron field produced in a 15 MV Varian CLINAC DHX medical accelerator, located in the Ospedale S. Chiara (Pisa). Both neutron spectra are known through measurements with a Bonner Sphere Spectrometer. In both cases the experimental response of the Dy-SSS agrees with the reference data. Moreover, it is demonstrated that the spectrometric capability of the new device are independent from the directional distribution of the neutron field. This opens the way to a new generation of moderation-based neutron instruments, presenting all advantages of the Bonner sphere spectrometer without the disadvantage of the repeated exposures. This concept is being developed within the NESCOFI@BTF project of INFN (Commissione Scientifica Nazionale 5).

Bedogni, R.; Gómez-Ros, J. M.; Esposito, A.; Gentile, A.; Chiti, M.; Palacios-Pérez, L.; Angelone, M.; Tana, L.

2012-08-01

210

Neutron Energy and Time-of-flight Spectra Behind the Lateral Shield of a High Energy Electron Accelerator Beam Dump, Part II: Monte Carlo Simulations  

SciTech Connect

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

Roesler, Stefan

2002-09-19

211

Calculation of Neutron Time-of-Flight and Energy Spectra Behind Thick Shielding of an Electron Accelerator and Comparison to Experimental Data  

SciTech Connect

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

Roesler, Stefan

2002-05-06

212

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)] [Medical Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)

1996-02-01

213

Statistical methods for the chemical compound identification from neutron-induced gamma-ray spectra  

Microsoft Academic Search

The paper presents a list correlation method to identify specific high explosive (HE) compounds from the spectra derived from reconstructed images of a gamma- ray camera. The correlation method uses all the information of the characteristic gamma rays for the associated elements of a compound. We show that the method is able to identify HE material at the compound level

Randy C. Stevenson; Joonki Noh; Mark D. Hammig

2009-01-01

214

Accelerator measurement of the energy spectra of neutrons emitted in the interaction of 3-GeV protons with several elements  

NASA Technical Reports Server (NTRS)

The application of time of flight techniques for determining the shapes of the energy spectra of neutrons between 20 and 400 MeV is discussed. The neutrons are emitted at 20, 34, and 90 degrees in the bombardment of targets by 3 GeV protons. The targets used are carbon, aluminum, cobalt, and platinum with cylindrical cross section. Targets being bombarded are located in the internal circulating beam of a particle accelerator.

Nalesnik, W. J.; Devlin, T. J.; Merker, M.; Shen, B. S. P.

1972-01-01

215

Potential model for tetrathiafulvalene based on inelastic neutron scattering and Raman spectra  

NASA Astrophysics Data System (ADS)

Tetrathiafulvalene (TTF) is a key molecule in the family of charge-transfer salts of interest for their novel transport properties. The correspondence between transport property and electron-molecular vibration coupling requires that we understand the phonon density of states for these materials. Here we report the results of a low temperature study of neutral TTF using both inelastic neutron scattering spectroscopy and Raman spectroscopy. The new data has been interpreted using the CLIMAX code to calculate the neutron spectral profile which has also been calculated based on a set of force constants derived using Density Functional Theory to calculate the ground state energy of neutral TTF. The two approaches lead to a concordant set of harmonic force constants for the in-plane and out-of-plane normal modes of TTF.

Burns, Gary R.; Favier, Frederic; Jones, Deborah J.; Rozière, Jacques; Kearley, Gordon J.

2003-09-01

216

The determination of phosphorus by fast neutron activation analysis  

E-print Network

of Seef Sample 2 General Layout of Mark ZZfSystem 3 Mark ZXZ Pneumatic Tube System for Past, Neutron 20b Activation Analysis 4. Block Diagram of Mark ZXX System 5. Assembly of Tvo 3" x 3" MaZ(Tl) Crystals 6. Target Depletion curve 7, cal, Q... neutron activation analysis has been found to be feasible. The technique utilizes ''the reaction P31(n, u)Al . The half life of Al S is 2. 3 minutesf and the 1?78 Nev gamma was detected by scintillation spectrometry. Possible interferences are the Si2S...

To-On, Maen

2012-06-07

217

Neutron energy and time-of-flight spectra behind the lateral shield of a high energy electron accelerator beam dump. Part I: measurements  

NASA Astrophysics Data System (ADS)

Neutron energy and time-of-flight spectra were measured behind the lateral shield of the electron beam dump at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were produced by a 28.7 GeV electron beam hitting the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shield. The measurements were performed using an NE213 organic liquid scintillator behind different thicknesses of the concrete shield of 274, 335, and 396 cm, respectively. The neutron energy spectra between 6 and 800 MeV were obtained by unfolding the measured pulse height spectrum with the detector response function. The attenuation length of neutrons in concrete was then derived. The spectra of neutron time-of-flight between beam on dump and neutron detection by NE213 were also measured. The corresponding experimental results were simulated with the FLUKA Monte Carlo code. The experimental results show good agreement with the simulated results.

Taniguchi, S.; Nakamura, T.; Nunomiya, T.; Iwase, H.; Yonai, S.; Sasaki, M.; Rokni, S. H.; Liu, J. C.; Kase, K. R.; Roesler, S.

2003-05-01

218

Neutron Energy and Time-of-flight Spectra Behind the Lateral Shield of a High Energy Electron Accelerator Beam Dump,Part I: Measurements  

SciTech Connect

Neutron energy and time-of-flight spectra were measured behind the lateral shield of the electron beam dump at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were produced by a 28.7 GeV electron beam hitting the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shield. The measurements were performed using a NE213 organic liquid scintillator behind different thicknesses of the concrete shield of 274 cm, 335 cm, and 396 cm, respectively. The neutron energy spectra between 6 and 800 MeV were obtained by unfolding the measured pulse height spectrum with the detector response function. The attenuation length of neutrons in concrete was then derived. The spectra of neutron time-of-flight between beam on dump and neutron detection by NE213 were also measured. The corresponding experimental results were simulated with the FLUKA Monte Carlo code. The experimental results show good agreement with the simulated results.

Roesler, Stefan

2002-09-24

219

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

E-print Network

Rainbow-Like Spectra with a CD: An Active-Learning Exercise G. Planins v ic v , University, México R ainbow-like spectra, produced by reflexive diffraction of white light on a CD, offer in this journal,1 Ouseph provided detailed instructions on how to use a CD to demon- strate spectacular reflection

Planin�iè, Gorazd

220

Current Spectra Translation in Single Phase Rectifiers: Implications to Active Power Factor Corrections  

E-print Network

fEs(? 9t Current Spectra Translation in Single Phase Rectifiers: Implications to Active Power spectra translation of a line commutated single phase full wave rectifier. Analytical expressions systems. The proposed theory is supported by computer simulation. harmonic contentof the rectified side

221

BOREHOLE NEUTRON ACTIVATION: THE RARE EARTHS.  

USGS Publications Warehouse

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

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

1987-01-01

222

Extraction of nuclear level densities from neutron spectra emitted in proton-induced reactions on lead isotopes and Bi  

NASA Astrophysics Data System (ADS)

Neutron-production spectra from (p,n) reactions on 204,206,207,208Pb and 209Bi measured previously by a Russian group were analyzed to extract numerical values for the level densities of the residual nuclei up to excitation energies of 5-6 MeV with uncertainties of 20-50%. Comparisons with the Gilbert-Cameron form and various parametrizations of the Ignatyuk formulation indicate that the Ignatyuk model with original parameters describes the results well whereas the other forms yield lower level densities. The agreement with the results of the first analysis by the experimenters themselves varies over the range of nuclei considered, being poorest for 204,206Bi.

Wallner, A.; Strohmaier, B.; Vonach, H.

1995-02-01

223

Study of neutron activation yields in spallation reaction of 400 MeV/u carbon on a thick lead target  

NASA Astrophysics Data System (ADS)

The spallation-neutron yield was studied experimentally by bombarding a thick lead target with 400 MeV/u carbon beam. The data were obtained with the activation analysis method using foils of Au, Mn, Al, Fe and In. The yields of produced isotopes were deduced by analyzing the measured ? spectra of the irradiated foils. According to the isotopes yields, the spatial and energy distributions of the neutron field were discussed. The experimental results were compared with Monte Carlo simulations performed by the GEANT4+FLUKA code.

Ma, Fei; Ge, Hong-Lin; Zhang, Xue-Ying; Zhang, Hong-Bin; Ju, Yong-Qin; Chen, Liang; Yang, Lei; Fu, Fen; Zhang, Ya-Ling; Li, Jian-Yang; Liang, Tian-Jiao; Zhou, Bin; Wang, Song-Lin; Li, Jin-Yang; Xu, Jun-Kui; Lei, Xiang-Guo; Qin, Zhi; Gu, Long

2014-07-01

224

Neutron spectra in thorium and depleted uranium-plutonium-loaded light water reactors  

SciTech Connect

The technical feasibility of using plutonium mixed with natural uranium in one-third of the cores of light water reactors (LWRs) has been sufficiently demonstrated. A number of reactors in Europe are currently operated with one-third mixed-oxide cores. If the option of burning excess plutonium in conventional LWR reactors in this country is selected, it has been estimated that the long-term disposition of the excess plutonium would take many decades. This time can be significantly reduced if the plutonium is burned in a fast breeder reactor. However, in the present economic and political climate, such an approach is difficult to implement. On the other hand, if the neutron spectrum in an LWR core is hardened, the well-developed and well-understood LWR can accomplish the goal of effectively burning excess plutonium to convert to proliferation-resistive fuel such as {sup 233}U. The authors present some fundamental characteristics of thorium and depleted uranium-plutonium-fueled LWRs. High fuel burnup levels can be achieved by tightening the lattice of an LWR loaded with thorium and depleted uranium and plutonium (nitride or oxide) and increasing the plutonium content. The neutron spectrum in such a reactor is very hard and tends to approach that of a Na-cooled fast reactor. Instead of Zircaloy, stainless steel can be used as fuel cladding and structural material since it has a low fast neutron capture cross section. Supercritical steam, generated at high pressures, can be used as coolant. If the cladding and structural materials used in this reactor can withstand corrosion in water under high-irradiation conditions, high conversion ratios of thermal heat to electricity will be possible.

Takahashi, H.; Zhang, J.; Cokinos, D.; Rohatgi, U.

1999-07-01

225

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

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

226

Extraction of polychromatic thermal neutrons by Bragg diffraction to use for prompt gamma neutron activation analysis  

NASA Astrophysics Data System (ADS)

Extraction method of thermal neutron beam by Bragg diffraction is investigated. A thermal neutron beam is used for the Prompt Gamma Neutron Activation Analysis system at HANARO, a 30 MW research reactor in the Korea Atomic Energy Research Institute. Polychromatic beam including all orders of diffraction is obtained by setting a pair of pyrolytic graphite crystals with a Bragg angle of 45° on a horizontal white beam line. Diffracted neutron flux at the sample position is calculated by considering the integrated reflectivity and mosaic spread of crystals. Due to the divergence effect, the mosaic spread of crystals is optimized to give the maximum and flat flux at the sample position. An experiment has been performed to verify the reflectivities for high order diffractions from pyrolytic graphite. When the focusing technique of bending the crystals is adopted, a design value of 1.0×108n/cm2s is expected at the sample position. Hence Bragg diffraction is a promising method of extracting thermal neutrons for PGNAA.

Byun, S. H.; Choi, H. D.; Jun, B. J.; Kim, M. S.

2000-07-01

227

Compilation of detection sensitivities in thermal-neutron activation  

NASA Technical Reports Server (NTRS)

Detection sensitivities of the chemical elements following thermal-neutron activation have been compiled from the available experimental cross sections and nuclear properties and presented in a concise and usable form. The report also includes the equations and nuclear parameters used in the calculations.

Wahlgren, M. A.; Wing, J.

1967-01-01

228

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

229

Neutron activation analysis of Hellenistic pottery from Boeotia, Greece  

Microsoft Academic Search

A set of 122 ceramic vessels found mostly in Hellenistic tombs in Boeotia, Greece, has been analysed using neutron activation analysis. The samples had been found during excavations of ancient cemeteries in the towns of Akraiphnion and Aliartos situated, respectively, at the eastern and south-western shores of the ancient lake of Copais (north-western part of Boeotia), as well as at

A. Schwedt; V. Aravantinos; A. Harami; V. Kilikoglou; M. Kylafi; H. Mommsen; N. Zacharias

2006-01-01

230

Neutron activation analysis of ivory of African elephants  

Microsoft Academic Search

Instrumental neutron activation analysis was applied to 61 ivory samples of which origin countries are known. 12 elements such as Br, Ca, Cl, Co, Cs, Fe, Mg, Mn, Na, Sc, Sr and Zn, were determined in all samples. The factor score of each sample was calculated for each factor by making use of principal component analysis in order to determine

T. Takeuchi; Y. Nakano; H. Koike

1996-01-01

231

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

232

Evaluation of a system for routine instrumental neutron activation analysis  

Microsoft Academic Search

The system for routine instrumental neutron activation analysis, in use for several years at the IRI at Delft, has been evaluated.\\u000a Basis of this evaluation are: quality of the results, costs per analysis, capacity and ease of operation. A comprehensive\\u000a description of the analysis system and associated hardware and software is included.

M. de Bruin; P. J. M. Korthoven; P. Bode

1982-01-01

233

Neutron activation analysis and provenance research in archaeology  

Microsoft Academic Search

Neutron activation analysis is a powerful quantitative analytical technique with application in a broad range of disciplines such as agriculture, archaeology, geochemistry, health and human nutrition, environmental monitoring and semiconductor technology. Due to its excellent sensitivity, great accuracy and precision, and versatility, the technique is a suitable method for analysing many different types of samples. Archaeologists, in particular, have made

Michael D Glascock; Hector Neff

2003-01-01

234

Analysis by neutron activation analysis a some ancient Dacian ceramics  

E-print Network

Ancient Dacian ceramics, from three different establishments from Romanian territory have been analyzed by neutron activation analysis. A series of elements has been determined: Ba, Eu, K, La, Mn, Na, Sc, Sm. Ba is the element that could be considered to differentiate relatively the three groups of ceramics.

Agata Olariu

1999-08-30

235

Neutron activation analysis of some Neolithic copper objects  

E-print Network

93 items of Neolithic copper from National Museum of History from Bucharest, with the provenance from Moldavia region have been analyzed by neutron activation analysis. The results of the analysis provide the values of the concentrations for the series of the determined elements: Au, Ag, As, Cr, Co, Fe, Hg, Ni, Sb, Se, Sn and Zn.

Agata Olariu

1999-08-31

236

Opacities and spectra of hydrogen atmospheres of moderately magnetized neutron stars  

E-print Network

There is observational evidence that central compact objects (CCOs) in supernova remnants have moderately strong magnetic fields $B\\sim10^{11}$ G. Meanwhile, available models of partially ionized hydrogen atmospheres of neutron stars with strong magnetic fields are restricted to $B\\gtrsim10^{12}$ G. We extend the equation of state and radiative opacities, presented in previous papers for $10^{12}\\mbox{ G}\\lesssim B \\lesssim 10^{15}$ G, to weaker fields. An equation of state and radiative opacities for a partially ionized hydrogen plasma are obtained at magnetic fields $B$, temperatures $T$, and densities $\\rho$ typical for atmospheres of CCOs and other isolated neutron stars with moderately strong magnetic fields. The first- and second-order thermodynamic functions, monochromatic radiative opacities, and Rosseland mean opacities are calculated and tabulated, taking account of partial ionization, for $3\\times10^{10}\\mbox{ G}\\lesssim B\\lesssim 10^{12}$ G, $10^5$ K $\\lesssim T\\lesssim 10^7$ K, and a wide range o...

Potekhin, A Y; Ho, W C G

2014-01-01

237

Monte Carlo Calculation of Thermal Neutron Inelastic Scattering Cross Section Uncertainties by Sampling Perturbed Phonon Spectra  

NASA Astrophysics Data System (ADS)

Nuclear data libraries provide fundamental reaction information required by nuclear system simulation codes. The inclusion of data covariances in these libraries allows the user to assess uncertainties in system response parameters as a function of uncertainties in the nuclear data. Formats and procedures are currently established for representing covariances for various types of reaction data in ENDF libraries. This covariance data is typically generated utilizing experimental measurements and empirical models, consistent with the method of parent data production. However, ENDF File 7 thermal neutron scattering library data is, by convention, produced theoretically through fundamental scattering physics model calculations. Currently, there is no published covariance data for ENDF File 7 thermal libraries. Furthermore, no accepted methodology exists for quantifying or representing uncertainty information associated with this thermal library data. The quality of thermal neutron inelastic scattering cross section data can be of high importance in reactor analysis and criticality safety applications. These cross sections depend on the material's structure and dynamics. The double-differential scattering law, S(alpha, beta), tabulated in ENDF File 7 libraries contains this information. For crystalline solids, S(alpha, beta) is primarily a function of the material's phonon density of states (DOS). Published ENDF File 7 libraries are commonly produced by calculation and processing codes, such as the LEAPR module of NJOY, which utilize the phonon DOS as the fundamental input for inelastic scattering calculations to directly output an S(alpha, beta) matrix. To determine covariances for the S(alpha, beta) data generated by this process, information about uncertainties in the DOS is required. The phonon DOS may be viewed as a probability density function of atomic vibrational energy states that exist in a material. Probable variation in the shape of this spectrum may be established that depends on uncertainties in the physics models and methodology employed to produce the DOS. Through Monte Carlo sampling of perturbations from the reference phonon spectrum, an S(alpha, beta) covariance matrix may be generated. In this work, density functional theory and lattice dynamics in the harmonic approximation are used to calculate the phonon DOS for hexagonal crystalline graphite. This form of graphite is used as an example material for the purpose of demonstrating procedures for analyzing, calculating and processing thermal neutron inelastic scattering uncertainty information. Several sources of uncertainty in thermal neutron inelastic scattering calculations are examined, including sources which cannot be directly characterized through a description of the phonon DOS uncertainty, and their impacts are evaluated. Covariances for hexagonal crystalline graphite S(alpha, beta) data are quantified by coupling the standard methodology of LEAPR with a Monte Carlo sampling process. The mechanics of efficiently representing and processing this covariance information is also examined. Finally, with appropriate sensitivity information, it is shown that an S(alpha, beta) covariance matrix can be propagated to generate covariance data for integrated cross sections, secondary energy distributions, and coupled energy-angle distributions. This approach enables a complete description of thermal neutron inelastic scattering cross section uncertainties which may be employed to improve the simulation of nuclear systems.

Holmes, Jesse Curtis

238

Higher-harmonics contamination in slow-neutron spectra measured with the Fourier time-of-flight method  

NASA Astrophysics Data System (ADS)

A thorough theoretical analysis is carried out in order to comprehensively assess the real significance of the higher-harmonics contamination eventually occurring in neutron Fourier time-of-flight spectra measured with standard saw-tooth choppers. The resulting general conclusion is that neither in the frequency domain nor in the actual time-of-flight domain can these distortions lead to any serious problems, even when a typical 4-channel phased detection system, representing the worst alternative in practice, is used for data acquisition. The predictions of the explicit formulae derived are found to agree well with the non-analytical and experimental evidence available of the higher-harmonics influence in both the above domains. A new result is the discovery that frame overlapping, as caused by a discrete frequency step between experimental Fourier data, can produce some negative apparent features in synthetized spectra, which may become detectable especially in certain high-accuracy diffraction applications of the standard Fourier time-of-flight method.

Pöyry, H.

1980-05-01

239

Detection sensitivities in 3-8 MeV neutron activation  

NASA Technical Reports Server (NTRS)

Study of detection sensitivities of 73 radioactive elements using fast unmoderated neutrons includes experiments for irradiation, cooling and counting conditions. The gamma ray emission spectra is used to identify the unknown material.

Wahlgren, M. A.; Wing, J.

1968-01-01

240

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

PubMed

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

Chai, Guo-Ming; Zhu, Yi-Feng

2010-04-01

241

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

Microsoft Academic Search

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

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

2006-01-01

242

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

243

Determination of noble metals by resonance neutron activation technique  

Microsoft Academic Search

Rhodium, palladium, platinum and iridium have been determined in silver matrix by nondestructive activation analysis upon\\u000a activation with cadmium- and silver-filtered resonance neutrons. Experiments with different types of filter combinations are\\u000a reported. The sensitivity of the method is 5·10?3% for rhodium, 5·10?3% for palladium, 3·10?2% for platinum and 5·10?3% for iridium.

M. Ördöch; Á. Biróné; G. Csath; E. Szabó

1976-01-01

244

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

SciTech Connect

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

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

2005-05-24

245

Magnetic Energy Spectra in Solar Active Regions Valentyna Abramenko and Vasyl Yurchyshyn  

E-print Network

Magnetic Energy Spectra in Solar Active Regions Valentyna Abramenko and Vasyl Yurchyshyn Big Bear productivity of solar active regions (ARs) and the power-law index, , of magnetic energy spectrum, E(k) k for 217 active regions (ARs) of different flare rate observed at the solar disk center from January 1997

246

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

PubMed Central

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

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

2009-01-01

247

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

248

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

SciTech Connect

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

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

2008-07-01

249

An improved prompt gamma neutron activation analysis facility using a focused diffracted neutron beam  

Microsoft Academic Search

The performance of the prompt gamma neutron activation analysis (PGNAA) facility at the MIT Research Reactor has been improved by a series of modifications. These modifications have increased the flux by a factor of three at the sample position to 1.7×107 n\\/cm2 s, and have increased the sensitivity, on average, by a factor of 2.5. The background for many samples

Kent J Riley; Otto K Harling

1998-01-01

250

Determination of trace elements by instrumental neutron activation analysis in Anatolian bentonitic clays 1 This article is dedicated to the 225 th anniversary of Istanbul Technical University. 1  

Microsoft Academic Search

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

N Güngör; T Tulun; A Alemdar

1998-01-01

251

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

252

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

253

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

254

Neutron activation analysis of uranium via 239 Np  

Microsoft Academic Search

A method is described for the analysis of uranium by neutron activation. The sample is brought into solution and the neptunium present is reduced to oxidation state (IV); quantitative extraction of239Np in the acidified aqueous phase (0.4thermal) enables determination of uranium at a lower concentration limit of 33 ng for periods of irradiation. cooling and measurement of 3 hours, 24

S. Fakhi; J. M. Paulus; S. Bouhlassa

1988-01-01

255

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

256

Multielement standards for instrumental neutron activation analysis of biological materials  

Microsoft Academic Search

Standards for instrumental neutron activation analysis (INAA) of biological materials are proposed. The standards are multielement\\u000a solid solutions in phenol-formaldehyde resole resin (PFR) moulded as pellets weighing 30 to 50 mg. The concentrations of trace\\u000a elements in the standards are selected so that, firstly, they are commensurable with their concentrations in the biological\\u000a materials and, secondly, that the analytical lines

L. M. Mosulishvili; M. A. Kolomi'tsev; V. Yu. Dundua; N. I. Shonia; O. A. Danilova

1975-01-01

257

Detection limits in epithermal neutron activation analysis of geological material  

Microsoft Academic Search

The improvement of detection limits for trace elements in geological samples by epithermal neutron activation analysis is\\u000a examined. The relative merits of cadmium, boron and composite cadmium+boron filters are compared for trace elements Ni, As,\\u000a Pd, Cd, Sb, W, Ir, Pt and Au, and interfering elements Na, K, Sc, Cr, Fe, Co and Cu. A boron filter gives optimum sensitivity

S. J. Parry

1980-01-01

258

Determination of trace elements in petroleum by neutron activation analysis  

Microsoft Academic Search

Instrumental neutron activation analysis (INAA) and Ge(Li) spectrometry have been used to determine Sc, Cr, Fe, Co, Ni, Zn,\\u000a As, Se, Sb, Eu, Au, Hg, and U in crude petroleum. The technique involves no chemical separations and no pre-concentration\\u000a of the samples by ashing is necessary, thus avoiding contamination or loss of volatile elements. The estimated detection limits\\u000a in ppb

K. R. Shah; R. H. Filby; W. A. Haller

1970-01-01

259

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

260

Instrumental neutron activation analysis of semiconductor grade silicon  

Microsoft Academic Search

The single comparator method in neutron activation analysis has been applied to the investigation of the purity of silicon\\u000a single-crystals of different origins. The following impurities were determined: Au, Sb, Co, Cu and Na. Studies were also carried\\u000a out on the surface contamination of silicon samples introduced through steps of sample preparation and irradiation. Up to\\u000a nineteen elements on the

K. Fujinaga; K. Kudo

1979-01-01

261

Instrumental neutron activation analysis of “melian”potsherds  

Microsoft Academic Search

Instrumental neutron activation analysis has been applied for the determination of 20 minor and trace elements (As, Ce, Co,\\u000a Cr, Cs, Eu, Fe, Hf, La, Lu, Na, Rb, Sb, Sc, Sm, Ta, Tb, Th, Yb and Zn) in two groups of potsherds which had been excavated\\u000a at two different sites of Greece, the islands of Thasos (Group A) and Delos

A. P. Grimanis; M. Vassilaki-Grimani; M. I. Karayannis

1977-01-01

262

Neutron activation analysis for trace elements in foods  

Microsoft Academic Search

Food samples reflecting average food consumption by an adult in the southeastern, northeastern, central, and western parts\\u000a of the United States were collected and prepared as if for consumption. The prepared foods were divided into twelve different\\u000a food categories and analyzed by instrumental neutron activation analysis. The concentration of Ca, Mn, Mg, Al, Na, K, Cu,\\u000a Cl, Sb, Hg, Se,

J. T. Tanner; M. H. Friedman

1977-01-01

263

Neutron activation analysis of an iranian cigarette and its smoke  

Microsoft Academic Search

Non-destructive neutron activation analysis, employing a high-resolution Ge(Li) detector, was applied to determine the concentration\\u000a of 24 trace elements in the tobacco of the Zarrin cigarette which is commercially made in Iran. These elements are: Na, K,\\u000a Sc, Cr, Mn, Fe, Co, Zn, Se, Br, Rb, Ag, Sb, Cs, Ba, La, Ce, Sm, Eu, Tb, Hf, Au, Hg and Th.

Z. Abedinzadeh; M. Razeghi; B. Parsa

1977-01-01

264

Determination of trace elements in petroleum by neutron activation analysis  

Microsoft Academic Search

Using thermal neutron activation and a large-volume high-resolution Ge(Li) ?-ray spectrometer, the feasibility of the determination\\u000a of the concentrations of Na, S, Cl, K, Ca, V, Mn, Cu, Ga, and Br in crude oils has been demonstrated. This instrumental method,\\u000a which requires neither a chemical separation technique nor pre-concentration or post-concentration of trace elements by ashing,\\u000a eliminates many inherent errors

K. R. Shah; R. H. Filby; W. A. Haller

1970-01-01

265

Instrumental neutron activation analysis and the characterization of granitic rocks  

Microsoft Academic Search

It has been shown that instrumental neutron activation analysis with intermediate to long-lived isotopes can be used to determine\\u000a 25 elements in granites from the Bushveld Igneous Complex, South Africa. By the use of the multivariate technique of discriminant\\u000a analysis these element concentrations were used to characterize the mineralized granite. The results indicate that because\\u000a of its ability to determine

J. I. W. Watterson; J. P. F. Sellschop

1977-01-01

266

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

NASA Astrophysics Data System (ADS)

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

Abyar, Fatemeh; Farrokhpour, Hossein

2014-11-01

267

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

268

Measurement and calculation of high-energy neutron spectra behind shielding at the CERF 120 GeV/c hadron beam facility  

NASA Astrophysics Data System (ADS)

Neutron energy spectra were measured behind the lateral shield of the CERF (CERN-EU High Energy Reference Field) facility at CERN with a 120 GeV/c positive hadron beam (a mixture of mainly protons and pions) on a cylindrical copper target (7-cm diameter by 50-cm long). An NE213 organic liquid scintillator (12.7-cm diameter by 12.7-cm long) was located at various longitudinal positions behind shields of 80- and 160-cm thick concrete and 40-cm thick iron. The measurement locations cover an angular range with respect to the beam axis between 13 and 133°. Neutron energy spectra in the energy range between 32 MeV and 380 MeV were obtained by unfolding the measured pulse height spectra with the detector response functions which have been verified in the neutron energy range up to 380 MeV in separate experiments. Since the source term and experimental geometry in this experiment are well characterized and simple and results are given in the form of energy spectra, these experimental results are very useful as benchmark data to check the accuracies of simulation codes and nuclear data. Monte Carlo simulations of the experimental set up were performed with the FLUKA, MARS and PHITS codes. Simulated spectra for the 80-cm thick concrete often agree within the experimental uncertainties. On the other hand, for the 160-cm thick concrete and iron shield differences are generally larger than the experimental uncertainties, yet within a factor of 2. Based on source term simulations, observed discrepancies among simulations of spectra outside the shield can be partially explained by differences in the high-energy hadron production in the copper target.

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

2008-01-01

269

Measurement And Calculation of High-Energy Neutron Spectra Behind Shielding at the CERF 120-GeV/C Hadron Beam Facility  

SciTech Connect

Neutron energy spectra were measured behind the lateral shield of the CERF (CERN-EU High Energy Reference Field) facility at CERN with a 120 GeV/c positive hadron beam (a mixture of mainly protons and pions) on a cylindrical copper target (7-cm diameter by 50-cm long). An NE213 organic liquid scintillator (12.7-cm diameter by 12.7-cm long) was located at various longitudinal positions behind shields of 80- and 160-cm thick concrete and 40-cm thick iron. The measurement locations cover an angular range with respect to the beam axis between 13 and 133{sup o}. Neutron energy spectra in the energy range between 32 MeV and 380 MeV were obtained by unfolding the measured pulse height spectra with the detector response functions which have been verified in the neutron energy range up to 380 MeV in separate experiments. Since the source term and experimental geometry in this experiment are well characterized and simple and results are given in the form of energy spectra, these experimental results are very useful as benchmark data to check the accuracies of simulation codes and nuclear data. Monte Carlo simulations of the experimental set up were performed with the FLUKA, MARS and PHITS codes. Simulated spectra for the 80-cm thick concrete often agree within the experimental uncertainties. On the other hand, for the 160-cm thick concrete and iron shield differences are generally larger than the experimental uncertainties, yet within a factor of 2. Based on source term simulations, observed discrepancies among simulations of spectra outside the shield can be partially explained by differences in the high-energy hadron production in the copper target.

Nakao, N.; /SLAC; Taniguchi, S.; /Japan Synch. Radiation Res. Inst.; Roesler, S.; Brugger, M.; /CERN; Hagiwara, M.; /CYRIC, Tohoku U.; Vincke, H.; /SLAC /CERN; Khater, H.; Prinz, A.A.; Rokni, S.H.; /SLAC; Kosako, K.; /Shimizu, Tokyo

2009-06-09

270

Neutron field measurements in phantom with foil-activation methods. Technical report, 29 November 1985-29 November 1986  

SciTech Connect

The threshold neutron-foil spectrometry method, utilizing the SAND II spectrum unfolding code, was evaluated by carrying out a measurement in the standard fission-source facility, simultaneous with six (6) in-phantom measurements of neutron spectra. The foil spectrometry was done with the full set of threshold foils, mid-thorax in ER1, where a 2 in. lead wall separated reactor and phantom. A five-foil set was utilized for the phantom mid-head and phantom hip measurements in ER1, as well as for mid-thorax, mid-head and hip in ER2, free field. Calculations of the mid-thorax and mid-head spectra in ER1 and ER2 were carried out, with the source term normalized to nickel foil activations at the reactor entrance window. A simple 5-foil perturbation method for neutron dosimetry, utilizing hand calculations, was developed and evaluated for the ER1 and ER2 spectra. It appears to be the order of 6% accurate versus 3-4% for SAND II, which utilizes the best (calculated) a prior data available for spectral shape information.

Verbinski, V.V.; Cassapakis, C.G.

1986-11-29

271

Install active/passive neutron examination and assay (APNEA)  

SciTech Connect

This document describes activities pertinent to the installation of the prototype Active/Passive Neutron Examination and Assay (APNEA) system built in Area 336 into its specially designed trailer. It also documents the basic theory of operation, design and protective features, basic personnel training, and the proposed characterization site location at Lockheed Martin Specialty Components, Inc., (Specialty Components) with the estimated 10 mrem/year boundary. Additionally, the document includes the Preventive Change Analysis (PCA) form, and a checklist of items for verification prior to unrestricted system use.

Not Available

1996-04-01

272

Determination of vanadium in human serum by neutron activation analysis  

Microsoft Academic Search

Vanadium in serum has been investigated by the aid of neutron activation analysis (8 min irradiation at 8·1013 n·cm?2·s?1 in the reactor FR-II of the Kernforschungszentrum in Karlsruhe). The lyophilized samples were dry-ashed before irradiation\\u000a and the52V activity extracted after irradiation. The values for V in the sera of 22 healthy males ranged from 0.029–0.939 ng V·ml?1. There is a

R. Cornelis; J. Versieck; L. Mees; J. Hoste; F. Barbier

1980-01-01

273

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

SciTech Connect

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

Greenwood, L.R.; Intasorn, A.

1989-07-01

274

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

SciTech Connect

Effective doses were calculated from the delivery of 6 MV, 15 MV, and 18 MV conventional and intensity-modulated radiation therapy (IMRT) prostate treatment plans. ICRP-60 tissue weighting factors were used for the calculations. Photon doses were measured in phantom for all beam energies. Neutron spectra were measured for 15 MV and 18 MV and ICRP-74 quality conversion factors used to calculate ambient dose equivalents. The ambient dose equivalents were corrected for each tissue using neutron depth dose data from the literature. The depth corrected neutron doses were then used as a measure of the neutron component of the ICRP protection quantity, organ equivalent dose. IMRT resulted in an increased photon dose to many organs. However, the IMRT treatments resulted in an overall decrease in effective dose compared to conventional radiotherapy. This decrease correlates to the ability of an intensity-modulated field to minimize dose to critical normal structures in close proximity to the treatment volume. In a comparison of the three beam energies used for the IMRT treatments, 6 MV resulted in the lowest effective dose, while 18 MV resulted in the highest effective dose. This is attributed to the large neutron contribution for 18 MV compared to no neutron contribution for 6 MV.

Howell, Rebecca M.; Hertel, Nolan E.; Wang Zhonglu; Hutchinson, Jesson; Fullerton, Gary D. [Emory University School of Medicine, Department of Radiation Oncology, 1365 Clifton Road AT200, Atlanta, Georgia 30322 (United States); Georgia Institute of Technology, 900 Atlantic Drive, Atlanta, Georgia 30332 (United States); Univ. Texas Health Science Center, 7703 Floyd Curl Drive, San Antonio, Texas 78229 (United States)

2006-02-15

275

Measurements and calculations of the electron recoil spectra from gamma rays emitted by nitrogen for a 14MeV neutron source  

Microsoft Academic Search

The electron recoil spectra from gamma rays produced by the interaction of 14-MeV neutrons with 0.5, 1.0, 3.0, and 7.0 mean-free-paths (mfps) of nitrogen have been measured with NE-213 scintillators positioned at 26, 30, and 120 deg at distances ranging between 7 and 10 m. Thin wall spherical Dewars filled with liquid nitrogen, with radii dimensions equivalent to the above

L. F. Hansen; T. Komoto; E. F. Plechaty; B. A. Pohl; G. S. Sidhu; C. Wong

1977-01-01

276

Neutron Emission Spectra of 104,105,106,108,110Pd Isotopes for (p,xn) Reactions at 21.6 MeV Proton Incident Energy  

NASA Astrophysics Data System (ADS)

Palladium, which is a rare and lustrous silvery-white color from precious metals, plays important role in fusion-fission reactions and different fields of nuclear technology. In addition, it is used for not only cold fusion experiments but also separation of hydrogen isotopes researches for fusion reactors. In this study, neutron-emission spectra produced by (p,xn) reactions for structural fusion material 104,105,106,108,110Pd isotopes have been investigated by a proton beam at 21.6 MeV. Moreover, multiple pre-equilibrium mean free paths constant from internal transition, and the pre-equilibrium and equilibrium level density parameters have been analyzed for some (p,xn) neutron-emission spectra calculated. New evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model were used to calculate the pre-equilibrium neutron-emission spectra. For the reaction equilibrium component, Weisskopf-Ewing model calculations were preferred. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

Büyükuslu, H.; Kaplan, A.; Tel, E.; Aydin, A.; Y?ld?r?m, G.

2010-02-01

277

Magnetar activity mediated by plastic deformations of neutron star crust  

E-print Network

We advance a "Solar flare" model of magnetar activity, whereas a slow evolution of the magnetic field in the upper crust, driven by electron MHD (EMHD) flows, twists the external magnetic flux tubes, producing persistent emission, bursts and flares. At the same time the neutron star crust plastically relieves the imposed magnetic field stress, limiting the strain $ \\epsilon_t $ to values well below the critical strain $ \\epsilon_{crit}$ of a brittle fracture, $ \\epsilon_t \\sim 10^{-2}\\epsilon_{crit} $. Magnetar-like behavior, occurring near the magnetic equator, takes place in all neutron stars, but to a different extent. The persistent luminosity is proportional to cubic power of the magnetic field (at a given age), and hence is hardly observable in most rotationally powered neutron stars. Giant flares can occur only if the magnetic field exceeds some threshold value, while smaller bursts and flares may take place in relatively small magnetic fields. Bursts and flares are magnetospheric reconnection events t...

Lyutikov, Maxim

2014-01-01

278

Activation energy spectra for annealing of ion irradiation induced defects in silica glasses  

E-print Network

Measurements were performed on 150 lm thick rectangular bulk alkali-borosilicate glass samples (6´23 mm2Activation energy spectra for annealing of ion irradiation induced defects in silica glasses T. van 407, 1098 SJ Amsterdam, The Netherlands Abstract In situ stress measurements were performed on alkali-borosilicate

Polman, Albert

279

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...

280

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 × 10 7 n/cm 2 s. 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

281

Multimode spectra and active mode locking potential of quantum dot lasers  

NASA Astrophysics Data System (ADS)

A time-frequency-domain formalism for analysis of mode-locked quantum dot laser dynamics is developed. A potential for generating subpicosecond pulses in an actively mode-locked construction is predicted. Low chirp pulses are predicted, correlating with a low linewidth enhancement factor calculated. Strong hole burning associated with quantum dot active media is shown to broaden the mode-locking spectra noticeably, leading to shorter pulses.

Xing, C.; Avrutin, E. A.

2005-05-01

282

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

283

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

NASA Astrophysics Data System (ADS)

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

El Abd, A.

2014-10-01

284

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

NASA Technical Reports Server (NTRS)

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

Kazanas, D.

1984-01-01

285

Investigations on the comparator technique used in epithermal neutron activation analysis  

Microsoft Academic Search

The possible extension of the comparator technique of reactor neutron activation analysis into the field of epithermal neutron\\u000a activation has been investigated. Ruthenium was used for multi-isotopic comparator. Experiments show that conversion of the\\u000a so-called reference k-factors—determined by irradiation with reactor neutrons—into kepi-factors usable at activation under cadmium filter, can be evaluated with fair accuracy. Sources and extent of errors

T. Bereznai; D. Bódizs; G. Keömley

1977-01-01

286

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

287

Ultra Sensitive Neutron Activation Measurements of 232Th in Copper  

NASA Astrophysics Data System (ADS)

Copper, thanks to its low content in radioactive contaminations, is a material widely used for shielding, holders and other objects close to the sensitive parts of the detectors in many experiments in rare event physics. This implies that tools able to reach sensitivity of the order of <10-12 gram of contaminants per gram of copper are of crucial importance. A methodology based in Neutron Activation Analysis (NAA) has been developed to obtain an extremely high sensitivity in the analysis of 232Th in copper samples. A detection limit of 5×10-13 g 232Th/g Cu has been achieved through the irradiation of 200 g of copper sample which subsequently was radio-chemically concentrated using nitric acid and then actinide resin from Eichrom Inc. Several elutions were performed with various inorganic acids to concentrate the 232Th activation product (233Pa) from the copper matrix and to also eliminate the radioactive background induced by the neutron bombardment to reach higher sensitivity.

Clemenza, M.; di Tigliole, A. Borio; Previtali, E.; Salvini, A.

2011-04-01

288

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

E-print Network

)b reaction is 5 2 . 6 7 Mey since the 0 value is 4 . 63 NeV. The calculation indicated that 3 5 04 channels separated the reference gamma bur st and the high energy neutrons associated with the next neutron burst . This also corresponds... )b reaction is 5 2 . 6 7 Mey since the 0 value is 4 . 63 NeV. The calculation indicated that 3 5 04 channels separated the reference gamma bur st and the high energy neutrons associated with the next neutron burst . This also corresponds...

Hertel, Nolan Elmer

2012-06-07

289

AN EXAMINATION OF THE UAPALA-USULUTÁN CERAMIC SPHERE USING INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS.  

E-print Network

??This thesis summarizes an examination of the Uapala-Usulután Ceramic Sphere using Instrumental Neutron Activation Analysis (INAA). Usulután pottery is found at sites within chiefdoms throughout… (more)

Goralski, Craig

2008-01-01

290

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

USGS Publications Warehouse

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

Rowe, J.J.; Steinnes, E.

1977-01-01

291

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

292

The X-ray spectra and the rotation-activity connection of RS CVN binaries  

NASA Technical Reports Server (NTRS)

Results from a survey of RS CVn binaries which were observed with the Imaging Proportional Counter (IPC) on board the Einstein Observatory are presented. Spectral analyses of the IPC pulse height spectra show that the coronae of RS CVn binaries always contain hot gas with temperatures 10 million K, similar to active late-type main sequence stars, and that at least 2 temperature components are necessary to account for the higher quality IPC spectra (when absorption is unimportant). It is argued that these bimodal temperature distributions indicate true distributions of emission measure vs temperature that are continuous (just as is the case for magnetically-confined coronal plasma loops observed on the Sun). It is shown that none of the derivable X-ray characteristics of RS CVn binaries depend on rotation period, implying that claims of period-activity relationships in RS CVn binaries are unfounded.

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

1985-01-01

293

The calibration of DD neutron indium activation diagnostic for Shenguang-III facility  

E-print Network

The indium activation diagnostic was calibrated on an accelerator neutron source in order to diagnose deuterium-deuterium (DD) neutron yields of implosion experiments on Shenguang-III facility. The scattered neutron background of the accelerator room was measured by placing a polypropylene shield in front of indium sample, in order to correct the calibrated factor of this activation diagnostic. The proper size of this shield was given by Monte Carlo simulation software. The affect from some other activated nuclei on the calibration was verified by judging whether the measured curve obeys exponential decay and contrasting the half life of the activated sample. The calibration results showed that the linear range reached up to 100 cps net count rate in the full energy peak of interest, the scattered neutron background of accelerator room was about 9% of the total neutrons and the possible interferences mixed scarcely in the sample. Subtracting the portion induced by neutron background, the calibrated factor of ...

Song, Zi-Feng; Liu, Zhong-Jie; Zhan, Xia-Yu; Tang, Qi

2014-01-01

294

Monte-Carlo Simulations of Radiation-Induced Activation in a Fast-Neutron and Gamma- Based Cargo Inspection System  

E-print Network

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 and gamma 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.

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

2012-01-04

295

Tables for simplifying calculations of activities produced by thermal neutrons  

USGS Publications Warehouse

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

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

1954-01-01

296

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

297

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

NASA Astrophysics Data System (ADS)

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

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

2006-01-01

298

Soft X-ray coronal spectra at low activity levels observed by RESIK  

NASA Astrophysics Data System (ADS)

Context. The quiet-Sun X-ray emission is important for deducing coronal heating mechanisms, but it has not been studied in detail since the Orbiting Solar Observatory (OSO) spacecraft era. Bragg crystal spectrometer X-ray observations have generally concentrated on flares and active regions. The high sensitivity of the RESIK (REntgenovsky Spectrometer s Izognutymi Kristalami) instrument on the CORONAS-F solar mission has enabled the X-ray emission from the quiet corona to be studied in a systematic way for the first time. Aims: Our aim is to deduce the physical conditions of the non-flaring corona from RESIK line intensities in several spectral ranges using both isothermal and multithermal assumptions. Methods: We selected and analyzed spectra in 312 quiet-Sun intervals in January and February 2003, sorting them into 5 groups according to activity level. For each group, the fluxes in selected spectral bands have been used to calculate values of parameters for the best-fit that leads to intensities characteristic of each group. We used both isothermal and multitemperature assumptions, the latter described by differential emission measure (DEM) distributions. RESIK spectra cover the wavelength range (3.3-6.1 Å). This includes emission lines of highly ionized Si, S, Cl, Ar, and K, which are suitable for evaluating temperature and emission measure, were used. Results: The RESIK spectra during these intervals of very low solar activity for the first time provide information on the temperature structure of the quiet corona. Although most of the emission seems to arise from plasma with a temperature between 2 MK and 3 MK, there is also evidence of a hotter plasma (T ~ 10 MK) with an emission measure 3 orders smaller than the cooler component. Neither coronal nor photospheric element abundances appear to describe the observed spectra satisfactorily.

Sylwester, B.; Sylwester, J.; Phillips, K. J. H.

2010-05-01

299

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

Microsoft Academic Search

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

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

1979-01-01

300

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

PubMed

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

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

2014-10-01

301

Determination of elements in National Bureau of Standards' geological Standard Reference Materials by neutron activation analysis  

Microsoft Academic Search

Instrumental neutron activation analysis (INAA) and prompt gamma neutron activation analysis (PGNAA) have been used to determine elemental concentrations in two recently issued National Bureau of Standards (NBS) Standard Reference Materials (SRM's). The results obtained are in good agreement with the certified and information values reported by NBS for those elements in each material for which comparisons are available. Average

Christopher C. Graham; Michael D. Glascock; James J. Carni; James R. Vogt; Thomas G. Spalding

1982-01-01

302

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

303

Modeling the Power Spectra of Active Galaxies with Markov Chain Monte Carlo  

NASA Astrophysics Data System (ADS)

It is now well established that the power spectra of most active galaxies can be fit by a broken power law, with a break frequency that depends on both mass and accretion rate. Fitting the power spectrum and establishing appropriate error bars for the parameters is an intensive and time-consuming process, involving extensive Monte Carlo simulations to fit over a grid of paramters. Here we present a Markov Chain Monte Carlo (MCMC) method for fitting the power spectra, which allows for an appropriate estimation of both the best-fit values and their errors. Results are presented for the X-ray light curves of several objects, and comparisons are made to previous efforts in terms of accuracy.

Marshall, Kevin

2012-01-01

304

Simulation and preliminary experimental results for an active neutron counter using a neutron generator for a fissile material accounting  

NASA Astrophysics Data System (ADS)

An active neutron coincidence counter using a neutron generator as an interrogation source has been suggested. Because of the high energy of the interrogation neutron source, 2.5 MeV, the induced fission rate is strongly affected by the moderator design. MCNPX simulation has been performed to evaluate the performance achieved with these moderators. The side- and bottom-moderator are significantly important to thermalize neutrons to induce fission. Based on the simulation results, the moderators are designed to be adapted to the experimental system. Their preliminary performance has been tested by using natural uranium oxide powder samples. For a sample of up to 3.5 kg, which contains 21.7 g of 235U, 2.64 cps/g- 235U coincidence events have been measured. Mean background error was 9.57 cps and the resultant coincidence error was 13.8 cps. The experimental result shows the current status of an active counting using a neutron generator which still has some challenges to overcome. However, the controllability of an interrogation source makes this system more applicable for a variety of combinations with other non-destructive methods like a passive coincidence counting especially under a harsh environment such as a hot cell. More precise experimental setup and tests with higher enriched samples will be followed to develop a system to apply it to an active measurement for the safeguards of a spent fuel treatment process.

Ahn, Seong-Kyu; Lee, Tae-Hoon; Shin, Hee-Sung; Kim, Ho-Dong

2009-10-01

305

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

306

The role of neutron activation analysis in nutritional biomonitoring programs  

SciTech Connect

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

Iyengar, V.

1988-01-01

307

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

308

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

309

The investigation of spices by use of instrumental neutron activation analysis  

E-print Network

contaminants. For this research, instrumental neutron-activation analysis (INAA) was used to determine the activities of U-235 fission products in common spices. Using this information, the concentrations of natural uranium in these spices and the doses...

Wise, Jatara Rob

2008-10-10

310

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

PubMed

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r(2) decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm(2) and is ? 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects. PMID:24784607

Hahn, K D; Cooper, G W; Ruiz, C L; Fehl, D L; Chandler, G A; Knapp, P F; Leeper, R J; Nelson, A J; Smelser, R M; Torres, J A

2014-04-01

311

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

NASA Astrophysics Data System (ADS)

We present a general methodology to determine the diagnostic sensitivity that is directly applicable to neutron-activation diagnostics fielded on a wide variety of neutron-producing experiments, which include inertial-confinement fusion (ICF), dense plasma focus, and ion beam-driven concepts. This approach includes a combination of several effects: (1) non-isotropic neutron emission; (2) the 1/r2 decrease in neutron fluence in the activation material; (3) the spatially distributed neutron scattering, attenuation, and energy losses due to the fielding environment and activation material itself; and (4) temporally varying neutron emission. As an example, we describe the copper-activation diagnostic used to measure secondary deuterium-tritium fusion-neutron yields on ICF experiments conducted on the pulsed-power Z Accelerator at Sandia National Laboratories. Using this methodology along with results from absolute calibrations and Monte Carlo simulations, we find that for the diagnostic configuration on Z, the diagnostic sensitivity is 0.037% ± 17% counts/neutron per cm2 and is ˜ 40% less sensitive than it would be in an ideal geometry due to neutron attenuation, scattering, and energy-loss effects.

Hahn, K. D.; Cooper, G. W.; Ruiz, C. L.; Fehl, D. L.; Chandler, G. A.; Knapp, P. F.; Leeper, R. J.; Nelson, A. J.; Smelser, R. M.; Torres, J. A.

2014-04-01

312

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

313

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

314

Feasibility of culvert IED detection using thermal neutron activation  

NASA Astrophysics Data System (ADS)

Bulk explosives hidden in culverts pose a serious threat to the Canadian and allied armies. Culverts provide an opportunity to conceal insurgent activity, avoid the need for detectable surface disturbances, and limit the applicability of conventional sub-surface sensing techniques. Further, in spite of the large masses of explosives that can be employed, the large sensor{target separation makes detection of the bulk explosive content challeng- ing. Defence R&D Canada { Sueld and Bubble Technology Industries have been developing thermal neutron activation (TNA) sensors for detection of buried bulk explosives for over 15 years. The next generation TNA sensor, known as TNA2, incorporates a number of improvements that allow for increased sensor-to-target dis- tances, making it potentially feasible to detect large improvised explosive devices (IEDs) in culverts using TNA. Experiments to determine the ability of TNA2 to detect improvised explosive devices in culverts are described, and the resulting signal levels observed for relevant quantities of explosives are presented. Observations conrm that bulk explosives detection using TNA against a culvert-IED is possible, with large charges posing a detection challenge at least as dicult as that of a deeply buried anti-tank landmine. Because of the prototype nature of the TNA sensor used, it is not yet possible to make denitive statements about the absolute sensitivity or detection time. Further investigation is warranted.

Faust, Anthony A.; McFee, John E.; Clifford, Edward T. H.; Andrews, Hugh Robert; Mosquera, Cristian; Roberts, William C.

2012-06-01

315

Cold neutron prompt gamma activation analysis, a non-destructive technique for hydrogen level assessment in zirconium alloys  

E-print Network

Cold neutron prompt gamma activation analysis, a non-destructive technique for hydrogen level to quantitatively assess hydrogen concentration in zirconium alloys. The technique, called Cold Neutron Prompt Gamma to a neutron source such as the one at the National Institute of Technology (NIST) Center for Neutron Research

Motta, Arthur T.

316

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

2007-01-01

317

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

318

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

E-print Network

above is changed in the code so that the total neutron flux is the same as that determined by Schoenbucher (Sc77). HELIUM-3 PROPORTIONAL COUNTER The He detector used in this study was a custom detector built by Harshaw Chemical Co... above is changed in the code so that the total neutron flux is the same as that determined by Schoenbucher (Sc77). HELIUM-3 PROPORTIONAL COUNTER The He detector used in this study was a custom detector built by Harshaw Chemical Co...

Sanza, Bruce Jerome

2012-06-07

319

Imaging Neutron Activation Analysis and Multiplexed Gamma Ray Spectrometry.  

NASA Astrophysics Data System (ADS)

This work demonstrates for the first time the feasibility of Imaging Neutron Activation Analysis (Imaging NAA) and of multiplexed gamma-ray spectrometry. The two techniques are based on position sensitive beta -gamma coincidence measurement using a gamma-ray detector, a charged particle imaging detector and a coincidence system. Imaging NAA is a technique for determining the 2-dimensional elemental distributions in heterogeneous samples. With multiplexed gamma-ray spectrometry it is possible to count an array of samples simultaneously which results in a substantial reduction in total counting time and also low background because of the coincidence measurement. Two distinctly different charged particle imaging detectors were investigated for electron localization. They were: (1) an electron optics based system for low energy secondary electron imaging and (2) a Position Sensitive Photomultiplier Tube (PSPMT) coupled to a thin plastic scintillator for beta imaging. The secondary electron imaging system offers a spatial resolution of 30 ?m but its active imaging area is only 1 mm in diameter, and the beta detection efficiency is less than 10%. The PSPMT gives a spatial resolution of 2.5 mm FWHM with a 60 x 55 mm^2 active area and a beta detection efficiency of up to 36%. The secondary electron imaging system is suitable for element mapping of small continuous heterogeneous samples, while the PSPMT is suitable for multiplexed gamma-ray spectrometry of discrete samples. Results show that using the PSPMT it is possible to multiplex 100 samples, which results in up to a factor of 36 gain in total counting time compared to counting the samples individually. Experimental results that demonstrate the two techniques are presented for various radionuclides that undergo beta, alpha or EC decay followed by coincident gamma -ray emission.

Dewaraja, Yuni Kamalika

320

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

NASA Astrophysics Data System (ADS)

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

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

2004-11-01

321

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

E-print Network

Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron; published online 23 April 2010 For the first time high areal-density R cryogenic deuterium-tritium DT essential for understanding how the fuel is assembled and for guiding the cryogenic program

322

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

SciTech Connect

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

Williams, R.E.

1981-10-12

323

Neutron activation analysis of saliva: Application in clinical chemistry, environmental and occupational toxicology  

Microsoft Academic Search

The contents of 21 chemical elements (Ag, Br, Ca, Cl, Co, Cr, Cs, Fe, Hg, K, Mg, Mn, N, Na, P, Rb, Sb, Sc, Se, Sr, Zn) in mixed non-stimulated saliva of 52 relatively healthy people were assessed by activation using 14 MeV neutrons and nuclear reactor neutrons. The study included 45 women and 7 men, aged 18 to 35.

V. Zaichick; A. Tsyb; S. Bagirov

1995-01-01

324

Activation measurements of the neutron yield at the JT-60U Tokamak.  

National Technical Information Service (NTIS)

This paper describes activation measurements of the neutrons from fusion plasmas. We are primarily interested in two narrow bands of neutron energies around 2.5 and 14 MeV. The d-d reaction has two branches with nearly equal probability, one generating a ...

T. Carlsson, M. Carlsson

1994-01-01

325

Standardization of NIRR-1 irradiation and counting facilities for instrumental neutron activation analysis  

Microsoft Academic Search

The first nuclear reactor in Nigeria, the Nigeria Research Reactor-1 (NIRR-1), is a Miniature Neutron Source Reactor (MNSR). It was specifically acquired for elemental analysis by the neutron activation analysis (NAA) technique. In this work, routine experimental schemes for the determination of over 30 elements of interest in different sample matrices have been developed. In order to validate the experimental

S. A. Jonah; I. M. Umar; M. O. A. Oladipo; G. I. Balogun; D. J. Adeyemo

2006-01-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

327

Fast-Neutron Activation of Long-Lived Nuclides in Natural Pb  

E-print Network

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

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

2012-09-20

328

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.

329

Further measurements of the delayed neutron spectra of \\/sup 93 -97\\/Rb and \\/sup 143 -145\\/Cs  

Microsoft Academic Search

A further series of delayed-neutron energy spectral measurements for the fission product precursors \\/sup 93 -97\\/Rb and \\/sup 143 -145\\/Cs was made using the TRISTAN ISOL facility. The specific goal of these experiments was to improve the spectral definition for each of these isotopes both at the lower energies (below approx.20 keV) and at the higher energies (above approx.800 keV).

R. C. Greenwood; A. J. Caffrey

1987-01-01

330

A Neutron Activation Gamma Ray spectrometer for Planetary Surface Analysis  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

331

Further measurements of the delayed neutron spectra of /sup 93 -97/Rb and /sup 143 -145/Cs  

SciTech Connect

A further series of delayed-neutron energy spectral measurements for the fission product precursors /sup 93 -97/Rb and /sup 143 -145/Cs was made using the TRISTAN ISOL facility. The specific goal of these experiments was to improve the spectral definition for each of these isotopes both at the lower energies (below approx.20 keV) and at the higher energies (above approx.800 keV). To that end the following series of experiments was conducted: measurements using a H/sub 2/ gas-filled proportional counter (2.6 Atm. pressure) with pulse-shape discrimination (between beta/gammas and neutron) at a gain setting of 0.3 keV/channel, measurements using a CH/sub 4/ gas-filled proportional counter (5.3 Atm. pressure) at a gain setting of 8 keV/channel; and measurements using a 5.1-cm diameter x 1.27-cm thick BC-501 liquid scintillation detector with pulse-shape discrimination at a neutron gain setting of approx.20 keV/channel. 9 refs., 11 tabs.

Greenwood, R.C.; Caffrey, A.J.

1987-01-01

332

Neutron radiography activity in the european program cost 524: Neutron imaging techniques  

NASA Astrophysics Data System (ADS)

COST is a framework for scientific and technical cooperation, allowing the coordination of national research on a European level, including 32 member countries. Participation of institutes from non-COST countries is possible. From an initial 7 Actions in 1971, COST has grown to 200 Actions at the beginning of 2000. COST Action 524 is under materials domain, the title of which being "Neutron Imaging Techniques for the Detection of Defects in Materials", under the Chairmanship of Dr. P. Chirco (I.N.F.N.). The following countries are represented in the Management Committee of Action 524: Italy, France, Austria, Germany, United Kingdom, Hungary, Switzerland, Spain, Czech Republic, Slovenia, and Russia. The six working groups of this Action are working respectively on standardization of neutron radiography techniques, on aerospace application, on civil engineering applications, on comparison and integration of neutron imaging techniques with other NDT, on neutron tomography, and on non radiographic techniques such as neutron scattering techniques. A specific effort is devoted to standardization issues, with respect to other non European standards. Results of work performed in the COST frame are published or will be published in the review INSIGHT, edited by the British Institute of Non Destructive Testing.

Chirco, P.; Bach, P.; Lehmann, E.; Balasko, M.

2001-07-01

333

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

334

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

335

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

336

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

337

Neutron activation analysis traces copper artifacts to geographical point of origin  

NASA Technical Reports Server (NTRS)

Impurities remaining in the metallic copper are identified and quantified by spectrographic and neutron activation analysis. Determination of the type of ore used for the copper artifact places the geographic point of origin of the artifact.

Conway, M.; Fields, P.; Friedman, A.; Kastner, M.; Metta, D.; Milsted, J.; Olsen, E.

1967-01-01

338

Determination of protein fold class from Raman or Raman optical activity spectra using random forests  

PubMed Central

Knowledge of the fold class of a protein is valuable because fold class gives an indication of protein function and evolution. Fold class can be accurately determined from a crystal structure or NMR structure, though these methods are expensive, time-consuming, and inapplicable to all proteins. In contrast, vibrational spectra [infra-red, Raman, or Raman optical activity (ROA)] are rapidly obtained for proteins under wide range of biological molecules under diverse experimental and physiological conditions. Here, we show that the fold class of a protein can be determined from Raman or ROA spectra by converting a spectrum into data of 10 cm?1 bin widths and applying the random forest machine learning algorithm. Spectral data from 605 and 1785 cm?1 were analyzed, as well as the amide I, II, and III regions in isolation and in combination. ROA amide II and III data gave the best performance, with 33 of 44 proteins assigned to one of the correct four top-level structural classification of proteins (SCOP) fold class (all ?, all ?, ? and ?, and disordered). The method also shows which spectral regions are most valuable in assigning fold class. PMID:21766384

Kinalwa, Myra; Blanch, Ewan W; Doig, Andrew J

2011-01-01

339

Explosives detection using prompt-gamma neutron activation and neural networks  

Microsoft Academic Search

This work describes a study of the application of a neural network to determine the presence of explosives using the neutron capture prompt gamma-ray spectra of the substances as patterns which were simulated via Monte Carlo N-particle transport code, version 4B. After the training of the neural networks, it was possible to determine the presence of the C-4 explosive, even

W. V. Nunes; A. X. da Silva; V. R. Crispim; R. Schirru

2002-01-01

340

Galaxy and Stellar Spectra  

NSDL National Science Digital Library

In this activity students learn that galaxies shine on the basis of their intergrated stellar population, therefore, adding together different stellar spectra should reproduce the spectra of a galaxy. This activity contains an applet which allows one to add spectra of up to four different stars to produce a resultant spectra. To reproduce qualitatively a spectra of a galaxy one can add together and F main sequence star and a K Giant. The spectra are normalized by V-band luminosity.

Department, University O.

2005-06-17

341

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

NASA Astrophysics Data System (ADS)

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation <10 MeV and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of 141Pr, an element that has a single, naturally occurring isotope, a significant n,2n cross-section, and decays by positron emission that result in two coincident 511 keV photons. Neutron fluences are thus inferred by relating measured reaction product decay activity to fluence. Specific sample activity is measured using the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay products. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma Focus Laboratory fusion sources. Lead, copper, beryllium, and silver activation detectors were compared. The detection method allows measurement of 14 MeV neutron yield with a total error of ?18%.

Meehan, Tim; Hagen, E. C.; Ruiz, C. L.; Cooper, G. W.

2010-08-01

342

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

343

Neutron activation analysis of dental metals with regard to forensic odontology (dental identification)  

Microsoft Academic Search

In cases of complicated identifications the neutron activation analysis of dental metals may inform more than usual descriptions\\u000a of the teeth including X-rays. Identifications would become more effective in the field of forensic stomatology by adding\\u000a “pilot” elements into the alloys of dental metals by the factories. The neutron activation analysis of dental metals from\\u000a Halsbrücke (GDR) are discussed and

K. Rötzscher; S. Mende; J. Flachowsky; M. Geisler; H.-J. Wehran

1973-01-01

344

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

2013-11-01

345

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

E-print Network

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

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

2008-09-18

346

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

PubMed Central

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

Sezgin, Necmettin

2012-01-01

347

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 239Pu eff in the total counting mode, and of about 10 mg of 239Pu eff 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

348

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

349

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

SciTech Connect

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. It is composed of a total-body neutron activation facility (TBNAF) and a whole body counter (WBC), and is used to measure total body sodium, phosphorus, chlorine, and calcium. Body potassium is measured by counting endogenous {sup 40}K with the whole body counter. The DGNA and PGNA facilities have been upgraded and modified since they were first built. 6 refs., 4 figs.

Dilmanian, F.A.; Weber, D.A.; Yasumura, S.; Kehayias, J.J.; Ellis, K.J. (Brookhaven National Lab., Upton, NY (USA)); Kamen, Y.; Lidofsky, L. (Columbia Univ., New York, NY (USA). Dept. of Applied Physics and Nuclear Engineering); Heymsfield, S.B.; Pierson, R.N. Jr.; Wang, J. (Columbia Univ., New York, NY (USA). Coll. of Physicians and Surgeons)

1989-01-01

350

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

351

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

352

A portable active interrogation system using a switchable AmBe neutron source  

NASA Astrophysics Data System (ADS)

Active neutron interrogation is an effective technique used to locate fissionable material. This paper discusses a portable system that utilizes a AmBe neutron source. The AmBe source consists of an americium alpha source and a beryllium target that can be switched into alignment to turn the source on and out of alignment to turn the source off. This offers a battery operated backpack portable source. The detector system that has been fabricated for use with this source is a fifteen tube 3He neutron detector. The results of initial experiments with the detector and MCNP calculations are discussed.

Allen, Matthew; Hertz, Kristin; Kunz, Christopher; Mascarenhas, Nicholas

2005-09-01

353

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

354

Development of the prototype pneumatic transfer system for ITER neutron activation system  

SciTech Connect

The neutron activation system (NAS) measures neutron fluence at the first wall and the total neutron flux from the ITER plasma, providing evaluation of the fusion power for all operational phases. The pneumatic transfer system (PTS) is one of the key components of the NAS for the proper operation of the system, playing a role of transferring encapsulated samples between the capsule loading machine, irradiation stations, counting stations, and disposal bin. For the validation and the optimization of the design, a prototype of the PTS was developed and capsule transfer tests were performed with the developed system.

Cheon, M. S.; Seon, C. R.; Pak, S.; Lee, H. G. [ITER Korea, National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Bertalot, L. [ITER Organization, Route de Vinon sur Verdon, 13115 Saint Paul Lez Durance (France)

2012-10-15

355

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

356

On-line sulfur determination in coal with prompt gamma neutron activation  

NASA Astrophysics Data System (ADS)

The prompt gamma neutron activation method has been found to be a useful technique for the on-line industrial measurements of bulk media. Based on this method, a system was developed for the on-line sulfur determination in coal. A 252Cf source is used for the production of neutrons and a high purity germanium (HPGe) detector is used for the detection of the gamma rays emitted. The system has been found to be linear over the range tested (0.5-6% in weight sulfur). Neutron-absorbing trace elements in coal such as Cl, were found to have no influence on the sulfur determination of the samples.

Vourvopoulos, George; Womble, Phillip C.

1989-02-01

357

Fine Structure in the Mm-Wavelength Spectra of the Active Region  

NASA Astrophysics Data System (ADS)

RESUMEN. Faltan observaciones solares espectrosc6picas en la longitud de onda milimetrica. Hay sugerencias de que se puede superponer una fi na estructura en frecuencia a la componente-S de la regi6n solar activa, asi como a la componente del brote en las longitudes de onda milimetri- cas. Se ha desarrollado un receptor de alta sensibilidad de pasos de frecuencia que opera en el intervalo de 23-18 GHz con una resoluci6n de 1 GHz y resoluci6n de tiempo variable entre 1.2 y 96 sec, usando la an- tena de Itapetinga de 13.7-m para estudiar la estructura fina en frecuencia y tiempo. Discutimos el espectro en longitud de onda-mm en re- giones activas y su evoluci6n en el tiempo. El estudio de Ia evoluci6n en el tiempo de la regi6n activa en AR 5569 observada el 29 de junio de 1989, sugiere la existencia de estructuras finas como funci6n deltiempo. ABSTRACT. There is a lack of mm-wavelength spectroscopic solar observations. There are suggestions that a fine structure in frequency may be superimposed on the S-component of solar active region as well as on the burst component at inm-wavelengths. To study fine structure in frequency and time, a high sensitivity step frequency receiver operating in the frequency range 23-18 GHz with frequency resolution of 1 GHz and variable time resolution 1.2 to 96 sec, using 13.7 m diameter Itapetinga radome covered antenna, has been developed. Here, we discuss mm-wavelength spectra of active regions and their time evolution. Study of time evolution of an active region AR 5569 observed on 29th June, 1989 suggests existence of fine structures as a function of time. ( Ck : SUN-ACTIVITY - SUN-RADIO RADIATION

Sawant, H. S.; Cecatto, J. R.

1990-11-01

358

Herschel/SPIRE Sub-millimeter Spectra of Local Active Galaxies  

E-print Network

We present the sub-millimeter spectra from 450 GHz to 1550 GHz of eleven nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) onboard Herschel. We detect CO transitions from J_up = 4 to 12, as well as the two [CI] fine structure lines at 492 and 809 GHz and the [NII] 461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions (SLEDs). The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n_H2 ~ 10^3.2 - 10^3.9 cm^-3 and T_kin ~ 300 - 800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H2 emission. We could not determine the specific heating mechanism of the warm gas, however it is possibly related to the star-formation activity in these galaxies. Our modeling of the [CI] emission suggests that it is produced in cold (T_kin 1...

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

2013-01-01

359

Particle body neutron activation analysis in vivo: A new approach to the investigation of metabolic bone disease  

Microsoft Academic Search

A new method of detecting changes in the calcium content of a hand by neutron activation analysis is described. A 25 Ci 241Am-Be source, positioned within a perspex tube, was used to provide the neutron flux. The fast neutrons were slowed by water moderation and the bones of a hand which gripped the tube were exposed to the maximum thermal

G. R. D. Catto; J. A. R. McIntosh; M. Macleod

1973-01-01

360

Neutron activation analysis of uranium in human bone, drinking water and daily diet  

Microsoft Academic Search

Uranium in human bone, drinking water and daily diet has been determined by neutron activation analysis using the238U(n, ?)239U reaction. An improved scheme for the separation of the239U is proposed; with this scheme, after neutron irradiation in a 100 kW TRIGA reactor, a uranium content as low as 5·10?11 g can be determined reliably, rapidly and easily. A wide range

T. Nozaki; M. Ichikawa; T. Sasuga; M. Inarida

1970-01-01

361

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

362

Neutron activation analysis for 39 elements in small or precious geologic samples  

Microsoft Academic Search

A procedure has been developed for the determination of 39 elements in a single sample of rock or mineral by neutron activation\\u000a analysis. After the sample has been irradiated with neutrons, it is separated chemically into 12 groups for radioassay with\\u000a one NaI(Tl) and two Ge(Li) detectors. Three chemists can complete the separations and sample preparations within 7 hrs after

R. O. Allen; L. A. Haskin; M. R. Anderson; O. Mueller

1970-01-01

363

Benchmark test of neutron transport calculations: Indium, nickel, gold, europium, and cobalt activation with and without energy moderated fission neutrons by iron simulating the Hiroshima atomic bomb casing  

SciTech Connect

A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated {sup 252}Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate {sup 152}Eu and {sup 60}Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated {sup 252}Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen. 18 refs., 10 figs., 4 tabs.

Iwatani, Kazuo; Shizuma, Kiyoshi; Hasai, Hiromi; Hoshi, Masaharu; Hiraoka, Masayuki; Hayakawa, Norihiko [Hiroshima Univ., Higashi-Hiroshima (Japan); Oka, Takamitsu [Kure Women`s College, Hiroshima-ken (Japan)

1994-10-01

364

Fission and activation of uranium by fusion-plasma neutrons  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

365

Determination of aluminium, silicon and magnesium in geological matrices by delayed neutron activation analysis based on k0 instrumental neutron activation analysis.  

PubMed

In this work, concentrations of silicon, aluminium and magnesium in geological matrices were determined by Neutron Activation Analysis based on k0-IAEA software. The optimum activation and delay times were found to be 5 min and 15-20 min respectively for the determination of Si via (29)Si (n,p) (29)Al reaction. The adopted irradiation scheme did not work for the determination of magnesium. Each sample was irradiated under a thermal neutron flux density of 5.0 × 10(11) ncm(-2)s(-1). Cadmium covered activation indicated that a permanent epithermal irradiation site for research reactors would be very useful for routine determination of silicon in environmental samples. PMID:23999324

Baidoo, I K; Dampare, S B; Opata, N S; Nyarko, B J B; Akaho, E H K; Quagraine, R E

2013-12-01

366

Quasistellar spectrum for neutron activation measurements at kT=5keV  

NASA Astrophysics Data System (ADS)

We have measured the neutron energy spectrum of the 18O(p,n)18F reaction at a proton energy of 2582 keV, 8 keV above the reaction threshold. At this energy the resulting neutron spectrum resembles almost perfectly a Maxwellian distribution at a thermal energy of kT=5.1±0.1keV. Since all neutrons are emitted in a forward cone of 140? opening angle, this reaction can be used for neutron activation measurements similar to the 7Li(p,n)7Be reaction, which is known for producing a thermal spectrum with kT=25keV. Measured neutron capture cross sections at kT=5.1keV and kT=25keV can be used to interpolate to kT=8keV, which characterizes the dominant neutron exposure during s-process nucleosynthesis in thermally pulsing low-mass AGB stars. In a first application of this new method the Maxwellian-averaged neutron capture cross section of 138Ba was measured to be /vT=13.0±0.5mb at kT=5.1keV.

Heil, M.; Dababneh, S.; Juseviciute, A.; Käppeler, F.; Plag, R.; Reifarth, R.; O'Brien, S.

2005-02-01

367

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

368

Method for predicting whispering gallery mode spectra of active spherical microresonators  

E-print Network

A full three-dimensional Finite-Difference Time-Domain (FDTD)-based toolkit is developed to simulate the whispering gallery modes of a microsphere in the vicinity of a dipole source, placed on the surface. This provides a guide for experiments that rely on coupling to active microspheres. The resultant spectra are compared to those of analytic models used in the field. In contrast to the analytic models, the FDTD method is able to collect flux from an arbitrary collection region, such as a disk-shaped region, analogous to an optical fibre. The flux collection time may also be altered to access transient phenomena that may not appear at long collection times. The customisability of the technique allows one to consider a variety of mode excitation scenarios, such as refractive index inhomogeneity in the material, and different resonator shapes, such as shells and ellipsoids. The coupling efficiency to specific modes within wavelength regions can thus be optimized, preselecting the desired optical properties pri...

Hall, Jonathan M M; Henderson, Matthew R; Francois, Alexandre; Reynolds, Tess; Riesen, Nicolas; Monro, Tanya M

2014-01-01

369

X-ray spectra and time variability of active galactic nuclei  

NASA Technical Reports Server (NTRS)

The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales.

Mushotzky, R. F.

1984-01-01

370

Trace metal detection in aquatic environments by activation analysis of naiad shells. Completion report. [Neutrons  

Microsoft Academic Search

This study investigated the feasibility of using neutron activation analysis of aquatic mollusk shells to measure quantities of trace metals in water. A generalized approach to estimating the sensitivity of a particular metal\\/irradiation facility\\/assay system was developed. Radiation hazard to both activation analysts and subsequent users of irradiated museum specimens was investigated and found to be minimal. A sample preparation

1976-01-01

371

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

SciTech Connect

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

Ku, L.; Kolibal, J.G.

1982-06-01

372

Stable labeled microspheres to measure perfusion: validation of a neutron activation assay technique.  

PubMed

Neutron activation is an accurate analytic method in which trace quantities of isotopes of interest in a sample are activated and the emitted radiation is measured with high-resolution detection equipment. This study demonstrates the application of neutron activation for the measurement of myocardial perfusion using stable isotopically labeled microspheres. Stable labeled and standard radiolabeled microspheres (15 microm) were coinjected in an in vivo rabbit model of myocardial ischemia and reperfusion. Radiolabeled microspheres were detected with a standard gamma-well counter, and stable labeled microspheres were detected with a high-resolution Ge detection after neutron activation of the myocardial and reference blood samples. Regional myocardial blood flow was calculated from the deposition of radiolabeled and stable labeled microspheres. Both sets of microspheres gave similar measurements of regional myocardial blood flow over a wide range of flow with a high linear correlation (r = 0.95-0.99). Neutron activation is capable of detecting a single microsphere in an intact myocardial sample while providing simultaneous quantitative measurements of multiple isotope labels. This high sensitivity and capability for measuring perfusion in intact tissue are advantages over other techniques, such as optical detection of microspheres. Neutron activation also can provide an effective method for reducing the production of low-level radioactive waste generated from biomedical research. Further applications of neutron activation offer the potential for measuring other stable labeled compounds, such as fatty acids and growth factors, in conjunction with microsphere measured flow, providing the capability for simultaneous measurement of regional metabolism and perfusion. PMID:11123224

Reinhardt, C P; Dalhberg, S; Tries, M A; Marcel, R; Leppo, J A

2001-01-01

373

Investigation of the neutron activation of endohedral rare earth metallofullerenes  

SciTech Connect

Endohedral lanthanide metallofullerenes and their water-soluble biocompatible derivatives have been synthesized. The effect that fast-neutron irradiation has on the stability and nuclear physical properties of endohedral metallofullerenes that are used as magnetocontrast materials ({sup 46}Sc, {sup 140}La, {sup 141}Nd, {sup 153}Sm, {sup 152}Eu, {sup 154}Eu, {sup 153}Sm, {sup 160}Tb, {sup 169}Yb, {sup 170}Tm (isomers I and III), and {sup 177}Lu) is studied. Our hypothesis, according to which carbon-shell relaxation is based on the fast nonradiative processes of an electron shake-off type, is confirmed.

Shilin, V. A., E-mail: shilin@pnpi.spb.ru; Lebedev, V. T.; Kolesnik, S. G.; Kozlov, V. S.; Grushko, Yu. S.; Sedov, V. P.; Kukorenko, V. V. [Russian Academy of Sciences, St. Petersburg Nuclear Physics Institute (Russian Federation)

2011-12-15

374

Flux variation related uncertainty in neutron activation analysis  

NASA Astrophysics Data System (ADS)

The half-life of the product of the nuclear reaction applied to monitor the neutron flux has significant influence on the uncertainties of derived quantities of an investigated sample, such as the reaction rates, isotopic composition. If the flux is supposed to be constant during the irradiation, but its value varies between an upper and a lower limit, a so-called flux variation error occurs in the derived quantities. This error has been quantitatively analysed regarding various irradiation times, decay constants of the monitor foils and the nuclides of interest. Practical formulae have been elaborated, which can be used to handle this type of uncertainty.

Rovni, István

2013-11-01

375

The fast neutron fluence and the activation detector activity calculations using the effective source method and the adjoint function  

SciTech Connect

This paper describes the application of effective source in forward calculations and the adjoint method to the solution of fast neutron fluence and activation detector activities in the reactor pressure vessel (RPV) and RPV cavity of a VVER-440 reactor. Its objective is the demonstration of both methods on a practical task. The effective source method applies the Boltzmann transport operator to time integrated source data in order to obtain neutron fluence and detector activities. By weighting the source data by time dependent decay of the detector activity, the result of the calculation is the detector activity. Alternatively, if the weighting is uniform with respect to time, the result is the fluence. The approach works because of the inherent linearity of radiation transport in non-multiplying time-invariant media. Integrated in this way, the source data are referred to as the effective source. The effective source in the forward calculations method thereby enables the analyst to replace numerous intensive transport calculations with a single transport calculation in which the time dependence and magnitude of the source are correctly represented. In this work, the effective source method has been expanded slightly in the following way: neutron source data were performed with few group method calculation using the active core calculation code MOBY-DICK. The follow-up neutron transport calculation was performed using the neutron transport code TORT to perform multigroup calculations. For comparison, an alternative method of calculation has been used based upon adjoint functions of the Boltzmann transport equation. Calculation of the three-dimensional (3-D) adjoint function for each required computational outcome has been obtained using the deterministic code TORT and the cross section library BGL440. Adjoint functions appropriate to the required fast neutron flux density and neutron reaction rates have been calculated for several significant points within the RPV and RPV cavity of the VVER-440 reacto rand located axially at the position of maximum power and at the position of the weld. Both of these methods (the effective source and the adjoint function) are briefly described in the present paper. The paper also describes their application to the solution of fast neutron fluence and detectors activities for the VVER-440 reactor. (authors)

Hep, J.; Konecna, A.; Krysl, V.; Smutny, V. [Calculation Dept., Skoda JS plc, Orlik 266, 31606 Plzen (Czech Republic)

2011-07-01

376

Neutron activation analysis of the rare earth elements in Nasu hot springs.  

PubMed

Eleven rare earth elements (lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium, holmium, thulium, ytterbium and lutetium) in hot spring waters and sinter deposits in the Nasu area were determined by the neutron activation method. The rare earth elements in hot spring water were pre-concentrated in ferric hydroxide precipitate and neutron-irradiated. The rare earth elements were chemically separated into lighter and heavier groups and the activity of each group was measured with a Ge(Li) detector. Distribution of the rare earth elements between the hot spring water and the sinter deposit was also discussed. PMID:684229

Ikeda, N; Takahashi, N

1978-06-01

377

Active-interrogation measurements of fast neutrons from induced fission in low-enriched uranium  

NASA Astrophysics Data System (ADS)

A detection system was designed with MCNPX-PoliMi to measure induced-fission neutrons from U-235 and U-238 using active interrogation. Measurements were then performed with this system at the Joint Research Centre in Ispra, Italy on low-enriched uranium samples. Liquid scintillators measured induced fission neutrons to characterize the samples in terms of their uranium mass and enrichment. Results are presented to investigate and support the use of organic liquid scintillators with active interrogation techniques to characterize uranium containing materials.

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

2014-02-01

378

Residual 152Eu and 60Co activities induced by neutrons from the Hiroshima atomic bomb  

SciTech Connect

Specific activities of 152Eu:Eu in stone samples exposed to the Hiroshima atomic bomb were determined for 70 samples up to a 1,500-m slant range from the epicenter. The specific activities of 60Co:Co were also determined for six samples near the Hiroshima hypocenter. First, the 152Eu data were investigated to find out the directional dependence of neutron activation. Directional anisotropy was not definite; however, there was an indication that the activation in the west-southwest was lower than in other directions. Second, measured 152Eu and 60Co radioactivity data were compared with activation calculations based on DS86 neutrons. It is clearly shown that the measured data are lower than the calculation near the hypocenter and vice versa at long distances beyond 1,000 m. The calculated-to-measured ratios of 152Eu are 1.6 at the hypocenter, 1.0 at approximately 900 m, and 0.05 at a 1,500-m slant range. Present results indicate that systematic errors exist in the DS86 neutrons concerning the source-term spectrum, neutron transport calculations in air, and/or activation measurements.

Shizuma, K.; Iwatani, K.; Hasai, H.; Hoshi, M.; Oka, T.; Morishima, H. (Hiroshima Univ. (Japan))

1993-09-01

379

Residual 152Eu and 60Co activities induced by neutrons from the Hiroshima atomic bomb.  

PubMed

Specific activities of 152Eu:Eu in stone samples exposed to the Hiroshima atomic bomb were determined for 70 samples up to a 1,500-m slant range from the epicenter. The specific activities of 60Co:Co were also determined for six samples near the Hiroshima hypocenter. First, the 152Eu data were investigated to find out the directional dependence of neutron activation. Directional anisotropy was not definite; however, there was an indication that the activation in the west-southwest was lower than in other directions. Second, measured 152Eu and 60Co radioactivity data were compared with activation calculations based on DS86 neutrons. It is clearly shown that the measured data are lower than the calculation near the hypocenter and vice versa at long distances beyond 1,000 m. The calculated-to-measured ratios of 152Eu are 1.6 at the hypocenter, 1.0 at approximately 900 m, and 0.05 at a 1,500-m slant range. Present results indicate that systematic errors exist in the DS86 neutrons concerning the source-term spectrum, neutron transport calculations in air, and/or activation measurements. PMID:8244696

Shizuma, K; Iwatani, K; Hasai, H; Hoshi, M; Oka, T; Morishima, H

1993-09-01

380

Fast neutron activation of 48. 6-min /sup 111/mCd in natural cadmium  

SciTech Connect

The 48.6-min isomeric state at 0.396 MeV in /sup 111/Cd can be excited by the neutron reactions /sup 110/Cd(n,..gamma..) /SUP 111m/ Cd, /sup 111/Cd(n,n') /SUP 111m/ Cd, and /sup 112/Cd(n,2n) /SUP 111m/ Cd. When natural cadmium is bombarded with fast neutrons, the influence of these reactions on the activation response varies according to the nature of the neutron spectrum. For a predominantly low-energy spectrum, the nonthreshold reaction /sup 110/Cd(n,..gamma..) /SUP 111m/ Cd dominates, while for a relatively hard spectrum, the threshold reactions /sup 111/Cd(n,n') /SUP 111m/ Cd and /sup 112/Cd(n,2n) /SUP 111m/ Cd are the most influential. This situation offers interesting possibilities for utilization of elemental cadmium samples as neutron activation dosimeters in reactor applications. Accordingly, the elemental differential cross section for /SUP 111m/ Cd excitation has been measured for cadmium over the energy range 0.135 to 10.01 MeV using activation techniques, and the response of this excitation function has been investigated for a standard fission neutron spectrum. Some implications of these results for dosimetry applications are examined.

Smith, D.L.; Meadows, J.W.

1982-08-01

381

Spatially Resolved Spectra of the "Teacup" Active Galactic Nucleus: Tracing the History of a Dying Quasar  

NASA Astrophysics Data System (ADS)

The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number of spectacular galaxies possessing extended emission-line regions (EELRs), the most famous being Hanny's Voorwerp galaxy. We present another EELR object discovered in the SDSS endeavor: the Teacup active galactic nucleus (AGN). Nicknamed for its EELR, which has a "handle"-like structure protruding 15 kpc into the northeast quadrant of the galaxy. We analyze the physical conditions of this galaxy with long-slit, ground-based spectroscopy from the Lowell, Lick, and KPNO observatories. With the Lowell 1.8 m Perkin's telescope we took multiple observations at different offset positions, allowing us to recover spatially resolved spectra across the galaxy. Line diagnostics indicate the ionized gas is photoionized primarily by the AGN. Additionally we are able to derive the hydrogen density from the [S II] ?6716/?6731 ratio. We generated two-component photoionization models for each spatially resolved Lowell spectrum. These models allow us to calculate the AGN bolometric luminosity seen by the gas at different radii from the nuclear center of the Teacup. Our results show a drop in bolometric luminosity by more than two orders of magnitude from the EELR to the nucleus, suggesting that the AGN has decreased in luminosity by this amount in a continuous fashion over 46,000 yr, supporting the case for a dying AGN in this galaxy independent of any IR based evidence. We demonstrate that spatially resolved photoionization modeling could be applied to EELRs to investigate long timescale variability.

Gagne, J. P.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Keel, W. C.; Rafter, S.; Fischer, T. C.; Bennert, V. N.; Schawinski, K.

2014-09-01

382

A bismuth activation counter for high sensitivity pulsed 14 MeV neutrons  

NASA Astrophysics Data System (ADS)

We have built a fast neutron bismuth activation counter that measures activation counts from pulsed 14-MeV neutron generators for incident neutron fluences between 30 and 300 neutrons/cm 2 at 15.2 cm (6 in.). The activation counter consists of a large bismuth germanate (BGO) detector surrounded by a bismuth metal shield in front of and concentric with the cylindrical detector housing. The 14 MeV neutrons activate the 2.6-millisecond (ms) isomer in the shield and the detector by the reaction 209Bi (n,2n?) 208mBi. The use of millisecond isomers and activation counting times minimizes the background from other activated materials and the environment. In addition to activation, the bismuth metal shields against other outside radiation sources. We have tested the bismuth activation counter, simultaneously, with two data acquisition systems (DASs) and both give similar results. The two-dimensional (2D) DAS and three dimensional (3D) DAS both consist of pulse height analysis (PHA) systems that can be used to discriminate against gamma radiations below 300 keV photon energy, so that the detector can be used strictly as a counter. If the counting time is restricted to less than 25 ms after the neutron pulse, there are less than 10 counts of background for single pulse operation in all our operational environments tested so far. High-fluence neutron generator operations are restricted by large dead times and pulse height saturation. When we operate our 3D DAS PHA system in list mode acquisition (LIST), real-time corrections to dead time or live time can be made on the scale of 1 ms time windows or dwell times. The live time correction is consistent with nonparalyzable models for dead time of 1.0±0.2 ?s for our 3D DAS and 1.5±0.3 ?s for our 2D DAS dominated by our fixed time width analog to digital converters (ADCs). With the same solid angle, we have shown that the bismuth activation counter has a factor of 4 increase in sensitivity over our lead activation counter, because of higher counts and negligible backgrounds.

Burns, E. J. T.; Thacher, P. D.; Hassig, G. J.; Decker, R. D.; Romero, J. A.; Barrett, K. P.

2011-08-01

383

Experimental comparative study of activation of stainless steels by 14 MeV neutrons  

Microsoft Academic Search

The activities induced by D–T fusion neutrons in samples of stainless steels considered as structural materials for perspective fusion devices were experimentally investigated. The total activity of the Russian ferritic steel 10H9VFA, which is one of the candidates for the first wall structural material of the Russian Demo design, is compared with the total activities of two SS316 samples and

V. D Kovalchuk; V. V Mostovoy; V. I Tereshkin; S. I Bobrovnik; D. V Markovskij; H Freiesleben; K Seidel; S Unholzer

1998-01-01

384

A passive-active neutron device for assaying remote-handled transuranic waste  

SciTech Connect

A combined passive-active neutron assay device was constructed for assaying remote-handled transuranic waste. A study of matrix and source position effects in active assays showed that a knowledge of the source position alone is not sufficient to correct for position-related errors in highly moderating or absorbing matrices. An alternate function for the active assay of solid fuel pellets was derived, although the efficacy of this approach remains to be established. 4 refs., 7 figs., 1 tab.

Estep, R.J.; Coop, K.L.; Deane, T.M.; Lujan, J.E.

1989-01-01

385

Residual 152Eu and 60Co activities induced by neutrons from the Hiroshima atomic bomb  

Microsoft Academic Search

Specific activities of 152Eu:Eu in stone samples exposed to the Hiroshima atomic bomb were determined for 70 samples up to a 1,500-m slant range from the epicenter. The specific activities of 60Co:Co were also determined for six samples near the Hiroshima hypocenter. First, the 152Eu data were investigated to find out the directional dependence of neutron activation. Directional anisotropy was

Kiyoshi Shizuma; Kazuo Iwatani; Hiromi Hasai; Masaharu Hoshi; Takamitsu Oka; Hiroshige Morishima

1993-01-01

386

Epithermal Neutron Activation Analysis at the IBR-2 reactor of the Frank Laboratory of Neutron Physics at the Joint Institute for Nuclear Research (Dubna)  

SciTech Connect

Experience of the Neutron Activation Analysis (NAA) Department in employing epithermal activation in life sciences and materials science is summarized. The potential of a combination of epithermal activation and the suppression of Compton scattering and contributions from cascade-photon-emitting elements for raising NAA-based analytical studies up to a new level are discussed.

Frontasyeva, M. V. [Joint Institute for Nuclear Research (Russian Federation)

2008-10-15

387

Restricted active space calculations of L-edge X-ray absorption spectra: From molecular orbitals to multiplet states  

NASA Astrophysics Data System (ADS)

The metal L-edge (2p ? 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d5) model systems with well-known electronic structure, viz., atomic Fe3+, high-spin [FeCl6]3- with ligand donor bonding, and low-spin [Fe(CN)6]3- that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

Pinjari, Rahul V.; Delcey, Mickaël G.; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

2014-09-01

388

Determination of rare earth elements in hot spring and crater lake waters by epithermal neutron activation analysis  

Microsoft Academic Search

Determination of the rare earth elements (REE's) in acidic hot spring and crater lake waters by neutron activation analysis (NAA), in which activation was performed mostly by epithermal neutrons (epithermal NAA) was investigated. Nine REE's, La, Ce, Sm, Eu, Tb, Ho, Tm, Yb and Lu, out of fourteen naturally existing REE's were determined at ppb levels with satisfactory precision. The

T. Honda; T. Oi; T. Ossaka; T. Nozaki; H. Kakihana

1989-01-01

389

Neutron activation measurements over an extremely wide dynamic range (invited) (abstract)  

NASA Astrophysics Data System (ADS)

The DT program at the Tokamak Fusion Test Reactor (TFTR) created requirements on 14 MeV neutron measurements to measure from ˜106 n/cm2 (for triton burnup and Ohmic tritium plasmas) to >1012 n/cm2 (characteristic of >10 MW DT plasmas) with an accuracy of 7% (one-sigma).1 To maintain an absolute calibration over this dynamic range with active neutron detectors required one to go from some absolute standard at one fluence level to a measurement at a much higher fluence. Maintaining accuracy requires an extremely linear set of measurements not systematically affected over this dynamic range. Neutron activation can provide such linearity when care is taken with a number of effects such as gamma-ray detection efficiency and sample contamination.2 Absolutely calibrated neutron yield measurements using dosimetric (well-known cross section) reactions with thin (low-mass) elemental foils will be described. This technique makes the detector comparison to an absolute standard of gamma-ray activity correspond to all neutron fluences by reducing the sample mass while keeping the activation detectors operating in a linear counting mode; that is, one always uses low count rates to minimize pileup effects. The International Thermonuclear Experimental Reactor is projected to have 1000 s burn durations at fluxes of few 1013 n/cm2 s, or more neutron fluence per second than entire TFTR discharges. Extrapolating neutron activation to these higher fluences will require yet more care. Some of the issues at such high fluences will be discussed.3 The National Ignition Facility (NIF) is projected to yield 10 MJ of fusion energy, or up to 1012 n/cm2 at the vacuum vessel wall, similar to TFTR DT conditions. However, it is expected that much interesting physics will be performed at yields far less than those from ignition, possibly covering an even greater dynamic range than needed on TFTR. Thin foil techniques do not have the sensitivity required at low fluences. Absolutely calibrated neutron yield measurements using associated particle calibrations of thick (large mass) foils on accelerators4 will be compared. Using both thin and thick foil approaches can cover the dynamic range required for NIF.

Barnes, Cris W.

1997-01-01

390

Minimum activation martensitic alloys for surface disposal after exposure to neutron flux  

DOEpatents

Steel alloys for long-term exposure to neutron flux have a martensitic microstructure and contain chromium, carbon, tungsten, vanadium and preferably titanium. Activation of the steel is held to within acceptable limits for eventual surface disposal by stringently controlling the impurity levels of Ni, Mo, Cu, N, Co, Nb, Al and Mn.

Lechtenberg, Thomas (San Diego, CA)

1985-01-01

391

Applications of Prompt Gamma Ray Neutron Activation Analysis: Detection of Illicit Materials  

Microsoft Academic Search

Prompt gamma ray neutron activation analysis (PGNAA) is an efficient nondestructive multi-elemental detection technique for samples such as metals, coal (mineral), cement, and radioactive materials as well as for explosives, chemical warfare agents, various narcotics, land mines, etc. The technique can be used in the laboratory or for on-site analysis for various samples. In addition, the PGNAA technique in elemental

Hee-Jung Im; Kyuseok Song

2009-01-01

392

Microcomputer-based pneumatic controller for neutron activation analysis. [For analyzing uranium ore samples  

Microsoft Academic Search

A microcomputer-based pneumatic controller for neutron activation analysis was designed and built at the Savannah River Laboratory for analysis of large numbers of geologic samples for locating potential supplies of uranium ore for the National Uranium Resource Evaluation program. In this system, commercially available microcomputer logic modules are used to transport sample capsules through a network of pressurized air lines.

J. S. Byrd; R. J. Sand

1976-01-01

393

Determination of carbon, nitrogen and phosphorus in cattail using cold neutron prompt-gamma activation analysis  

Microsoft Academic Search

Summary  A method for the determination of carbon, nitrogen, and phosphorus in cattail using cold neutron prompt-gamma activation analysis (CNPGAA) has been developed and evaluated through the analysis of standard reference materials (SRM). After extensive preparation, approximately 400 mg cattail samples from the lower Apalachicola River floodplain were irradiated in the CNPGAA facility at the National Institute of Standards and Technology

L. Zhao; L. Robinson; R. L. Paul; R. R. Greenberg; S. L. Miao

2005-01-01

394

Use of neutron activation analysis in determination of total organic chlorine and bromine  

Microsoft Academic Search

Neutron activation analysis is practically the only high-sensitivy element-selective detection method for chlorine, bromine and iodine. This method is just ideal for organic halogen determination after separation of organically bound species from inorganic. In recent years we have analysed organic chlorine and bromine from thousands of different kind of samples with different separation methods. For water samples we have used

P. K. G. Manninen; E. Häsänen

1993-01-01

395

Neutron-activation analysis of chlorine-containing pesticides in soils and tobaccos  

Microsoft Academic Search

From second national conference on uses of radioisotopes and ; .ionizing radiation in biology and agriculture; Softa, Bulgaria (25 Nov 1972). ; A nondestructive method was developed for determining the total residue levels of ; chlorine-containing pesticides in soils and farm produce. For accurate ; determination of organically bound chlorine in the different ; objects, preliminary inorganic extraction, neutron activation,

T. Dimchev; Kh. Gunchev

1972-01-01

396

Determination of trace element impurities in aspirin tablets by neutron activation analysis  

Microsoft Academic Search

Twenty five trace and minor elements (aluminium, arsenic, barium, bromine, cerium, chlorine, cobalt, chromium, cesium, europium, iron, hafnium, potassium, magnesium, manganese, sodium, rubidium, antimony, scandium, selenium, strontium, thorium, titanium, vanadium and zinc) in five different Egyptian aspirin brands (Aspo, Askin, Aspocid, Aspeol and Rivo) have been determined by instrumental neutron activation analysis. It has been concluded that the concentration of

F. Y. Iskander; D. E. Klein; T. L. Bauer

1986-01-01

397

Single-crystal neutron diffraction of bio-active small molecules  

NASA Astrophysics Data System (ADS)

The structures of three bio-active small molecules, acetylcholine bromide, creatine monohydrate and paracetamol, are described. Together with a brief account of the molecular geometry and hydrogen bonding, the temperature variation of the methyl group thermal parameters are specifically discussed. The room temperature structure of paracetamol from neutron diffraction data is reported for the first time.

Wilson, C. C.; Shankland, N.; Florence, A. J.; Frampton, C. S.

1997-02-01

398

Neutron activation study of the composition of lunar surface material from the Sea of Fertility  

NASA Technical Reports Server (NTRS)

The elemental composition of samples of lunar regolith returned by Luna 16 from the Sea of Fertility was determined by a radio activation method using generator and reactor neutrons, and also by gamma spectrometry with scintillation and Ge(Li) detectors.

Surkov, Y. A.; Kirnozov, F. F.; Ivanov, I. N.; Kilesov, G. M.; Ryvkin, B. N.; Shpanov, A. P.

1974-01-01

399

Availability of essential trace elements in ayurvedic indian medicinal herbs using instrumental neutron activation analysis  

Microsoft Academic Search

Specific parts of several plants (fruits, leaves, stem, bark and roots) often used as medicines in the Indian Ayurvedic system have been analysed for 20 elements (As, Ba, Br, Ca, Cl, Co, Cr, Cu, Fe, K, Mn, Mo, Na, P, Rb, Sb, Sc, Se, Sr and Zn) by employing instrumental neutron activation analysis (INAA). The samples were irradiated with thermal

Vivek Singh; A. N. Garg

1997-01-01

400

Neutron activation analysis of stable heavy metals as multiple markers in nutritional monitoring  

Microsoft Academic Search

A method is reported by which instrumental neutron activation analysis ; of various heavy metal elements has been applied to the monitoring of nutrient ; intake of laboratory animals. Some data are presented illustrating ; reproducibility. The scope of the method may be expanded by utilization of more ; or different markers. Tables are included, listing elements which may be

D. H. Gray; J. R. Vogt

1974-01-01

401

Homogeneity tests and certification analyses of coal fly ash reference materials by instrumental neutron activation analysis  

Microsoft Academic Search

The instrumental neutron activation analysis technique (INAA) was used for homogeneity tests and certification analyses of coal fly ash reference materials ENO, ECH, and EOP prepared at the Institute of Radioecology and Nuclear Techniques (IRANT), Koice, Czechoslovakia. Quantitative estimation of a degree of inhomogeneity was suggested. The relative standard deviations due to inhomogeneity were found to be

J. Ku?era; L. Soukal

1988-01-01

402

Neutron activation analysis techniques for identifying elemental status in Alzheimer's disease  

Microsoft Academic Search

Brain tissue (hippocampus and cerebral cortex) from Alzheimer's disease and control individuals sampled from Eastern Canada and the United Kingdom were analyzed for Ag, Al, As, B, Br, Ca, Cd, Co, Cr, Cs, Cu, Fe, Hg, I, K, La, Mg, Mn, Mo, Ni, Rb, S, Sb, Sc, Se, Si, Sn, Sr, Ti, V and Zn. Neutron activation analysis (thermal and

N. I. Ward; J. A. Mason

1987-01-01

403

Neutron activation analysis of fluid inclusions for copper, manganese, and zinc  

USGS Publications Warehouse

Microgram quantities of copper, manganese, and zinc, corresponding to concentrations greater than 100 parts per million, were found in milligram quantities of primary inclusion fluid extracted from samples of quartz and fluorite from two types of ore deposits. The results indicate that neutron activation is a useful analytical method for studying the content of heavy metal in fluid inclusions.

Czamanske, G.K.; Roedder, E.; Burns, F.C.

1963-01-01

404

Detection of repeated arsenical poisoning by neutron activation analysis of foot nail segments  

Microsoft Academic Search

In one case of repeated ingestions of arsenic over a period of one year, the value of sectional toe nail analysis was investigated. The arsenic determinations were performed by instrumental neutron activation analysis. After subdividing the nail transversely into segments of 0.5 mm length, several maxima and minima of arsenic concentrations were found. Taking the nail growth into consideration, these

G. Henke; A. Nucci; L. S. Queiroz

1982-01-01

405

In vivo neutron activation analysis: State of the art and future prospects  

Microsoft Academic Search

From the inauspicious beginning arising in the aftermath of a reactor accident in 1957, in vivo analysis of body elements by neutron activation has become an important tool in medical research. In particular, it provides a much needed means to make quantitative assessments of body composition of human beings in vivo. The data are useful both for basic physiological understanding

Stanton H. Cohn

1981-01-01

406

Correcting for uranium fission in instrumental neutron activation analysis of high-uranium rocks  

Microsoft Academic Search

Failure to correct for fission products of235U is shown to result in significant errors in the measured concentrations of La, Sm, Nd, Ba, Zr, and Mo by Instrumental Neutron Activation Analysis of high uranium rocks. Measured and calculated correction factors are presented as the ratio of the fission product to parts per million by weight of uranium in the rock.

M. D. Glascock; P. I. Nabelek; D. D. Weinrich; R. M. Coveney

1986-01-01

407

Determination of trace elements in fish by instrumental neutron activation analysis  

Microsoft Academic Search

Instrumental neutron activation analysis, INAA, was utilized for the determination of Al, Au, Br, Ca, Cl, Co, Cr, Cu, Fe, I, K, Mg, Mn, Na, Rb, Sc, V and W in 12 Tilapia Nilotica samples collected from the Aswan High Dam Lake following the destructive techniques.

R. M. Awadallah; A. E. Mohamed; S. A. Gabr

1985-01-01

408

Determination of trace elements in tobacco using different techniques of neutron activation analysis  

Microsoft Academic Search

Quantitative data on trace elements in two tobacco leaf (candidate) reference materials OTL-1 and VTL-2 prepared by the Polish Academy of Sciences and the Institute of Nuclear Chemistry and Technology, Warsaw, Poland, are presented and compard to recommended values, where available. By instrumental neutron activation analysis (INAA), as well as by radiochemical technique (RNAA) 30 elements were quantitatively determined and

B. Smodiš; M. Dermelj; R. Ja?imovi?

1995-01-01

409

14 MeV neutron activation analysis of rocks and meteorites.  

NASA Technical Reports Server (NTRS)

Fourteen-MeV neutron activation analysis has certain unique advantages for the nondestructive analysis of rocks and meteorites. In this review, the principles of the method are outlined, and the techniques for the precise and accurate analyses are summarized. Some current and future applications are described.

Morgan, J. W.; Ehmann, W. D.

1971-01-01

410

Recommended nuclear data for use in the k 0 standardization of neutron activation analysis  

Microsoft Academic Search

k0 factors (composite nuclear constants) for use in the k0 standardization of reactor neutron activation analysis were experimentally measured with great care in several laboratories. The recommended values thus obtained for the relevant gamma rays of 144 analytically interesting radionuclides are tabulated, together with evaluated values for their associated parameters such as resonance integral to thermal cross-section ratios and effective

Frans De Corte; András Simonits

2003-01-01

411

Environmental, toxicological and biomedical research on trace metals: Radiochemical separations for neutron activation analysis  

Microsoft Academic Search

Twenty-two radiochemical separation procedures for neutron activation analysis (NAA) of environmental and biological samples are presented. They are currently applied in the context of trace metal research related to the protection of the environment and human health. The radiochemical procedures are related to the separations of the elements into groups which allow the determination of up to 50 elements in

R. Pietra; E. Sabbioni; M. Gallorini; E. Orvini

1986-01-01

412

ANALYSIS OF OPTICAL Fe II EMISSION IN A SAMPLE OF ACTIVE GALACTIC NUCLEUS SPECTRA  

SciTech Connect

We present a study of optical Fe II emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest Fe II multiplets into three groups according to the lower term of the transition (b{sup 4} F, a{sup 6} S, and a{sup 4} G terms). These approximately correspond to the blue, central, and red parts, respectively, of the 'iron shelf' around H{beta}. We calculate an Fe II template that takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1. This Fe II template gives a more precise fit of the Fe II lines in broad-line AGNs than other templates. We extract Fe II, H{alpha}, H{beta}, [O III], and [N II] emission parameters and investigate correlations between them. We find that Fe II lines probably originate in an intermediate line region. We note that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM H{beta}, the velocity shift of Fe II, and the H{alpha}/H{beta} flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of Fe II and [O III] on continuum luminosity. We find that there is a Baldwin effect for [O III] but an inverse Baldwin effect for the Fe II emission. The [O III]/Fe II ratio thus decreases with L {sub {lambda}5100}. Since the ratio is a major component of the Boroson and Green Eigenvector 1 (EV1), this implies a connection between the Baldwin effect and EV1 and could be connected with AGN evolution. We find that spectra are different for H{beta} FWHMs greater and less than {approx}3000 km s{sup -1}, and that there are different correlation coefficients between the parameters.

Kovacevic, Jelena; Popovic, Luka C.; Dimitrijevic, Milan S., E-mail: jkovacevic@aob.bg.ac.r [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia)

2010-07-15

413

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

PubMed

The paper presents the results of calculating the equivalent dose from and energy spectrum of neutrons in the right-hand crewquarters in module Zvezda of the ISS Russian segment. Dose measurements were made in the period between July, 2010 and November, 2012 (ISS Missions 24-34) by research equipment including the bubble dosimeter as part of experiment "Matryoshka-R". Neutron energy spectra in the crewquarters are in good agreement with what has been calculated for the ISS USOS and, earlier, for the MIR orbital station. The neutron dose rate has been found to amount to 196 +/- 23 microSv/d on Zvezda panel-443 (crewquarters) and 179 +/- 16 microSv/d on the "Shielding shutter" surface in the crewquarters. PMID:25089327

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

2014-01-01

414

Monte Carlo Modelling of the Electron Spectra of 235U- and 239Pu- Films, Irradiated by Thermal Neutrons, Due to All Possible Mechanisms Excluding b-Decay. Comparison With Experiment  

E-print Network

The electron energy spectra, not connected to b-decay, of 235U- and 239Pu-films, irradiated by thermal neutrons, obtained by a Monte Carlo method is presented in the given work. The modelling was performed with the help of a computer code MCNP4C (Monte Carlo Neutron Photon transport code system), allowing to carry out the computer experiments on joint transport of neutrons, photons and electrons. The experiment geometry and the parameters of an irradiation were the same, as in [11] (the thickness of a foil varied only). As a result of computer experiments, the electron spectra was obtained for the samples of 235U, 239Pu and uranium dioxide of 93 % enrichment representing a set of films of 22 mm in diameter and different thickness: 0,001 mm, 0,005 mm, 0,02 mm, 0,01 mm, 0,1 mm, 1,0 mm; and also for the uranium dioxide film of 93 % enrichment (diameter 22 mm and thickness 0,01mm), located between two protective 0,025 mm aluminium disks (the conditions of experiment in [11]) and the electron spectrum was fixed at the output surface of a protective disk. The comparative analysis of the experimental [11] and calculated b--spectra is carried out.

V. D. Rusova; V. N. Pavlovychb; V. A. Tarasova; S. V. Iaroshenkob; D. A. Litvinova

2004-07-05

415

Neutron field for activation experiments in horizontal channel of training reactor VR-1  

NASA Astrophysics Data System (ADS)

The experimental channels of nuclear reactors often serve for nuclear data measurement and validation. The dosimetry-foils activation technique was employed to measure neutron field parameters in the horizontal radial channel of the training reactor VR-1, and to test the possibility of using the reactor for scientific purposes. The reaction rates, energy spectral indexes, and neutron spectrum at several irradiation positions of the experimental channel were determined. The experimental results show the feasibility of the radial channel for irradiating experiments and open new possibilities for data validation by using this nuclear facility.

Stefanik, Milan; Katovsky, Karel; Vins, Miroslav; Soltes, Jaroslav; Zavorka, Lukas

2014-11-01

416

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

NSDL National Science Digital Library

This article describes how you can obtain rainbow-like spectra, by reflexive diffraction of white light on a CD. The paper also discusses how building a coherent qualitative explanation can be a challenging task that requires students to combine gained knowledge with observations and explorations.

Planinå¡ic, Gorazd; Corona, Adrian; Sliå¡ko, Josip

2008-09-03

417

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

ERIC Educational Resources Information Center

Rainbow-like spectra, produced by reflexive diffraction of white light on a CD, offer a spectacular visual effect as well as an excellent classroom opportunity for students to learn how physics works. In this paper we show that building a coherent qualitative explanation can be a challenging task that requires students to combine gained knowledge…

Planinsic, G.

2008-01-01

418

Multi-Group Transport Methods for High-Resolution Neutron Activation Analysis  

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. In these applications, high-resolution gamma-ray spectrometers are used 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 for many problems can be prohibitively long. This work explores the use of multi-group deterministic methods for the simulation of coupled neutron-photon problems.

Burns, Kimberly A.; Smith, Leon E.; Gesh, Christopher J.; Shaver, Mark W.

2009-09-24

419

Importance of neutron energy distribution in borehole activation analysis in relatively dry, low-porosity rocks  

USGS Publications Warehouse

To evaluate the importance of variations in the neutron energy distribution in borehole activation analysis, capture gamma-ray measurements were made in relatively dry, low-porosity gabbro of the Duluth Complex. Although sections of over a meter of solid rock were encountered in the borehole, there was significant fracturing with interstitial water leading to a substantial variation of water with depth in the borehole. The linear-correlation coefficients calculated for the peak intensities of several elements compared to the chemical core analyses were generally poor throughout the depth investigated. The data suggest and arguments are given which indicate that the variation of the thermal-to-intermediate-to-fast neutron flux density as a function of borehole depth is a serious source of error and is a major cause of the changes observed in the capture gamma-ray peak intensities. These variations in neutron energy may also cause a shift in the observed capture gamma-ray energy.

Senftle, F.E.; Moxham, R.M.; Tanner, A.B.; Philbin, P.W.; Boynton, G.R.; Wager, R.E.

1977-01-01

420

Recent upgrade of the in vivo neutron activation facility at Brookhaven National Laboratory  

SciTech Connect

The in vivo neutron activation facility at Brookhaven National Laboratory consists of a delayed- and a prompt-gamma neutron activation (DGNA and PGNA) system and an inelastic neutron scattering (INS) system. The total body contents of several basic elements, including potassium, calcium, chlorine, sodium, and phosphorus are measured at the DGNA system; total body carbon is measured at the INS system; and the nitrogen-tohydrogen ratio is measured at the PGNA system. Based on the elemental composition, body compartments, such as total body fat and total body protein can be computed with additional independently measured parameters, such as total body water, body size, and body weight. Information on elemental and compartmental body composition obtained through neutron activation analysis is useful, if not essential, for research on growth, malnutrition, aging diseases, such as osteoporosis and acquired immunodeficiency syndrome in which the progression of the illness is closely related to changes in major body compartments, such as bone, adipose tissue, and muscle. The DGNA system has been modified and upgraded several times since it was first built. Recently, all three systems underwent major upgrades. This upgrading and some preliminary studies carried out with the modified facilities are reported here.

Ma, R.; Dilmanian, F.A..; Rarback, H.; Meron, M.; Kamen, Y.; Yasumura, S.; Weber, D.A. [Brookhaven National Lab., Upton, NY (United States); Stamatelatos, I.E. [Ioannina Univ. (Greece). Dept. of Medical Physics; Lidofsky, L.J. [Columbia Univ., New York, NY (United States). Dept. of Applied Physics and Nuclear Engineering; Pierson, R.N. Jr. [Saint Luke`s-Roosevelt Body Composition Unit, New York, NY (United States)

1993-10-01

421

Use of the semi-absolute method in neutron activation analysis  

Microsoft Academic Search

A new standardization method has been developed for neutron activation analysis. In this method, experimental activation constants,\\u000a are determined for a given reactor power level and irradiation and counting position. The unusual feature of this technique\\u000a is the fact that no flux monitor or standards are needed due to the exceptional stability of the reactor used. The semi-absolute\\u000a method was

C. Bergerioux; G. Kennedy; L. Zikovsky

1979-01-01

422

Interference from uranium in neutron activation analysis or rare-earths in silicate rocks  

Microsoft Academic Search

Neutron activation analysis of rare-earth elements in silicate rocks containing several parts per million uranium may be complicated\\u000a by interference from235U fission products and activation products of238U. The degree of interference has been measured quatitatively for La, Ce, Nd, Sm and Lu, and a method of correcting the NAA\\u000a data for these elements is presented.

G. Kennedy; A. Fowler

1983-01-01

423

A signature of chromospheric activity in brown dwarfs revealed by 2.5-5.0 ?m AKARI spectra  

NASA Astrophysics Data System (ADS)

We propose that the 2.7-?m H2O, 3.3-?m CH4 and 4.6-?m CO absorption bands can be good tracers of chromospheric activity in brown dwarfs. In our previous study, we found that there are difficulties in explaining entire spectra between 1.0 and 5.0 ?m with the unified cloudy model (UCM), a brown dwarf atmosphere model. Based on simple radiative equilibrium, temperature in a model atmosphere usually decreases monotonically with height. However, if a brown dwarf has a chromosphere, as inferred by some observations, the temperature in the upper atmosphere is higher. We construct a simple model that takes into account heating owing to chromospheric activity by setting a temperature floor in the upper atmosphere, and find that the model spectra of three brown dwarfs with moderate H? emission, an indicator of chromospheric activity, are considerably improved to match the AKARI spectra. Because of the higher temperatures in the upper atmosphere, the number of CH4 molecules is reduced, and the absorption band strengths become weaker. The strengths of the absorption bands of H2O and CO also become weaker. On the other hand, other objects with weak H? emission cannot be fitted with our treatment. We also briefly discuss magnetic heating processes that possibly operate in the upper atmosphere, by extending our numerical simulations for the Sun and stars with surface convection to brown dwarf atmospheres.

Sorahana, S.; Suzuki, T. K.; Yamamura, I.

2014-06-01

424

Resonant Absorption in the Active Galactic Nucleus Spectra Emerging from Photoionized Gas: Differences between Steep and Flat Ionizing Continua  

NASA Astrophysics Data System (ADS)

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si, S, and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities, and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission-line type 1 active galactic nuclei (AGNs), and steep X-ray spectrum, narrow optical emission-line type 1 AGNs. We show that the ~1 keV absorption feature observed in moderate-resolution X-ray spectra of several narrow-line Seyfert 1 galaxies can be explained by photoionization models, taking into account resonance absorption, without requiring relativistic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in flat X-ray spectrum Seyfert 1 galaxies. We finally present simulations of the spectra emerging from gas illuminated by both steep and flat ionizing continua, as seen by the AXAF high-energy transmission gratings and the baseline Constellation-X calorimeter. We discuss briefly the relevant physics that can be investigated with these instruments.

Nicastro, Fabrizio; Fiore, Fabrizio; Matt, Giorgio

1999-05-01

425

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

NASA Astrophysics Data System (ADS)

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

Dillmann, Iris; Abriola, Daniel; Singh, Balraj

2014-05-01

426

Fusion neutron energies and spectra  

Microsoft Academic Search

The interaction of two Maxwellian distributions of particles will differ from the interaction of the two particles at their respective Maxwell averages if the strength of the interaction varies significantly with energy over the widths of the distributions. This effect is considered here in particular for fusion (both D-T and D-D) for the mean energy of the reacting particles as

H. Brysk

1973-01-01

427

NECTAR—A fission neutron radiography and tomography facility  

NASA Astrophysics Data System (ADS)

NECTAR (Neutron Computerized Tomography and Radiography) is a versatile facility for radiographic and tomographic investigations as well as for neutron activation experiments using fission neutrons. The radiation sources for this facility are two plates of highly enriched uranium situated in the moderator vessel in FRM II. Thermal neutrons originating from the main fuel element of the reactor generate in these plates fast neutrons. These can escape through a horizontal beam tube without moderation. The beam can be filtered and manipulated in order to reduce the accompanying gamma radiation and to match the specific experimental tasks. A summary of the main parameters required for experimental set-up and (quantitative) data evaluation is presented. The (measured) spectra of the neutron and gamma radiations are shown along with the effect of different filters on their behavior. The neutron and gamma fluxes, dose rates, L/ D-ratios, etc. and the main parameters of the actually used detection systems for neutron imaging are given, too.

Bücherl, T.; Lierse von Gostomski, Ch.; Breitkreutz, H.; Jungwirth, M.; Wagner, F. M.

2011-09-01

428

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

NASA Technical Reports Server (NTRS)

The Pulsed Neutron Generator-Gamma Ray And Neutron Detectors (PNG-GRAND) experiment is an innovative application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA-GSFC) is to bring the PNG-GRAND instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Menus, asteroids, comets and the satellites of the outer planets. Gamma-Ray Spectrometers (GRS) have been incorporated into numerous orbital planetary science missions and, especially its the case of the Mars Odyssey GRS, have contributed detailed maps of the elemental composition over the entire surface of Mars. However, orbital gamma ray measurements have low spatial sensitivity (100's of km) due to their low surface emission rates from cosmic rays and subsequent need to be averaged over large surface areas. PNG-GRAND overcomes this impediment by incorporating a powerful neutron excitation source that permits high sensitivity surface and subsurface measurements of bulk elemental compositions. PNG-GRAND combines a pulsed neutron generator (PNG) with gamma ray and neutron detectors to produce a landed instrument to determine subsurface elemental composition without needing to drill into a planet's surface a great advantage in mission design. We are currently testing PNG-GRAND prototypes at a unique outdoor neutron instrumentation test facility recently constructed at NASA/GSFC that consists of a 2 m x 2 in x 1 m granite structure placed outdoors in an empty field. Because an independent trace elemental analysis has been performed on the material, this granite sample is a known standard with which to compare both Monte Carlo simulations and our experimentally measured elemental composition data. We will present data from operating PNG-GRAND in various experimental configurations on a known sample in a geometry that is identical to that on a planetary surface. We will also illustrate the use of gamma ray timing techniques to improve sensitivity and will compare the material composition results from our experiments to both an independent laboratory elemental composition analysis and MCNPX computer modeling results.

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

2010-01-01

429

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 24 MW 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 ele