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1

Use of the Foil Activation Method with Arbitrary Trial Functions to Determine Neutron Energy Spectra.  

National Technical Information Service (NTIS)

Neutron Spectra have been measured by the foil activation method in thirteen different environments in and around the Sandia Pulsed Reactor (SPR III), the White Sands Missile Range FBR, and the Annular Core Research Reactor (ACRR). The unfolded spectra we...

J. G. Kelly D. W. Vehar

1986-01-01

2

Use of the foil activation method with arbitrary trial functions to determine neutron energy spectra  

SciTech Connect

Neutron Spectra have been measured by the foil activation method in thirteen different environments in and around the Sandia Pulsed Reactor (SPR III), the White Sands Missile Range FBR, and the Annular Core Research Reactor (ACRR). The unfolded spectra were obtained by using the SANDII code in a manner which was not dependent on the initial trial. This altered technique is, therefore, 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 trail functions.

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

1986-01-01

3

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

4

Martian neutron leakage spectra  

NASA Astrophysics Data System (ADS)

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

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

1988-06-01

5

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

6

The Analysis of Cold Neutron Spectra.  

National Technical Information Service (NTIS)

The report reviews briefly several methods for interpreting neutron scattering data in terms of center frequency of infrared and Raman Spectra. In addition, a determination of elastic constants and thermodynamic properties from dispersion data for crystal...

R. A. Kromhout D. F. Burch

1969-01-01

7

Analysis of Cold Neutron Spectra of Metals.  

National Technical Information Service (NTIS)

A recently developed method for obtaining the absorbed energy spectrum, and calculating its absorption frequencies from elastic constants data, has been applied to metals, using cold neutron spectra in absence of infrared data. The emitted spectrum from i...

H. S. Plendl R. A. Kromhout

1971-01-01

8

Neutron Spectra in a 15 MV LINAC  

NASA Astrophysics Data System (ADS)

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

Vega-Carrillo, H. R.; Chu, Wei-Han; Tung, Chuan-Jong; Lan, Jen-Hong

2010-12-01

9

A neutron activation analyzer  

Microsoft Academic Search

SummaryDubbed Analyzer because of its simplicity, a neutron activation analysis facility for short-lived isomeric transitions is based on a low-cost rabbit system and an adaptive digital filter which are controlled by a software performing irradiation control, loss-free gamma-spectrometry, spectra evaluation, nuclide identification and calculation of concentrations in a fully automatic flow of operations. Designed for TRIGA reactors and constructed from

G. P. Westphal; H. Lemmel; F. Grass; P. P. De Regge; K. Burns; A. Markowicz

2005-01-01

10

Uncertainty Quantification on Prompt Fission Neutrons Spectra  

SciTech Connect

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

Talou, P. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)], E-mail: talou@lanl.gov; Madland, D.G.; Kawano, T. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)

2008-12-15

11

Activity: Graphing Spectra  

NSDL National Science Digital Library

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

12

Validation of aggregate delayed neutron spectra calculated from precursor data  

SciTech Connect

An extensive reference library of delayed neutron data has been compiled which contains fission yields and branchings, delayed neutron emission probabilities, and spectra for 271 precursors. These data have been used to calculate the aggregate behavior of delayed neutrons following a fission event in 43 fissioning systems. Least-squares techniques were used to produce fitted decay constants and abundances in the conventional six-group formalism from these calculated activity curves. A consistent set of six-group spectra have also been calculated for each of the fissioning systems. Recent measurements at the University of Lowell have produced measured energy spectra for delayed neutrons following the thermal fission (T) of {sup 235}U and {sup 239}Pu, and the fast fission (F) of {sup 238}U. These measured spectra provide data that may be used to validate the precursor data base and the fitted six-group data. This summary presents results of this validation effort. Both the individual precursor data and the six-group data have been used to calculate aggregate equilibrium spectra for {sup 235}U(T), {sup 238}U(F), and {sup 239}Pu(T) via summation techniques. The important precursors in each case are identified, and the status of their data reviewed. 8 refs., 3 figs., 3 tabs.

Brady, M. C.; England, T. R. [Oak Ridge National Lab., TN (USA); ,

1989-01-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

14

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

SciTech Connect

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

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

2010-12-07

15

Microdosimetric spectra measurements of JANUS neutrons  

SciTech Connect

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

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

1985-01-01

16

GAMMA RAY ENERGY SPECTRA FROM THERMAL NEUTRON CAPTURE  

Microsoft Academic Search

Energy spectra of gamma rays resulting from thermal neutron capture are ; compiled for 48 elements. The data are presented in both graphical and tabular ; form. Thermal-neutron-capture cross sections, isotopic abundances, binding ; energies of the extra neutron in the isotopes, and weighted-average binding ; energies are also tabulated. (auth);

Deloume

1958-01-01

17

GAMMA RAY ENERGY SPECTRA FROM THERMAL NEUTRON CAPTURE  

Microsoft Academic Search

Energy spectra of gamma rays resulting from thermal neutron capture are ; compiled for forty-nine elements. The data are presented in both graphical and ; tabular form. Thermal neutron capture cross sections, isotopic abundances, ; binding energies of the extra neutron in the isotopes, and weighted average ; binding energies are also tabulated. (auth);

Deloume

1958-01-01

18

H*(10) and neutron spectra around linacs  

Microsoft Academic Search

Neutron spectrum and ambient dose equivalent has been measured around two 10MV linear accelerators. Measurements were carried\\u000a out in Mevatron and Primus model linacs, both made by Siemens. Main differences between those models are the beam collimator\\u000a and the vault room. Here, Bonner sphere spectrometer with a passive thermal neutron detector has been utilized to measure\\u000a the neutron spectrum inside

Hector Rene Vega-Carrillo; Arturo Ortz-Hernandez; Victor Martin Hernandez-Davila; Berenice Hernndez-Almaraz; Teodoro Rivera Montalvo

2010-01-01

19

Fission neutron spectra measurements at LANSCE - status and plans  

SciTech Connect

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

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

2009-01-01

20

Measurement of inclusive neutron spectra at the ISR  

NASA Astrophysics Data System (ADS)

With a total absorption counter, inclusive neutron spectra have been measured at four ISR energies and at angles of 20, 66 and 119 mrad. The spectra show scaling behavior in the variables x and p?. Pion exchange is found to be important at large x values.

Engler, J.; Gibbard, B.; Isenbeck, W.; Mnnig, F.; Moritz, J.; Pack, K.; Scmidt, K. H.; Wegener, D.; Bartel, W.; Flauger, W.; Schopper, H.

1975-01-01

21

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

22

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

Microsoft Academic Search

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

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

2009-01-01

23

Variable spectra of active galaxies  

NASA Technical Reports Server (NTRS)

The analysis of EXOSAT spectra of active galaxies are presented. The objects examined for X-ray spectral variability were MR 2251-178 and 3C 120. The results of these investigations are described, as well as additional results on X-ray spectral variability related to EXOSAT observations of active galaxies. Additionally, the dipping X-ray source 4U1624-49 was also investigated.

Halpern, Jules P.

1988-01-01

24

Determination of neutron spectra using the programs GNSR and SPECTRIX  

NASA Astrophysics Data System (ADS)

We describe the capabilities and the application of two computer programs, which have been developed in order to facilitate common tasks in neutron spectrometry: GNSR (calculation of response matrices) and SPECTRIX (unfolding). Gas-filled Neutron Spectrometer Response calculates response functions and response matrices of various gas-filled neutron detectors. It can be configured to accommodate the appropriate gas-fillings and supports a number of different neutron beam configurations with a possibility to input calculated or measured neutron beam spectra. The program includes graphical capabilities as well as a context-sensitive help system. SPECTRIX implements several unfolding algorithms as well as support algorithms for unfolding and includes graphics capabilities and context-sensitive help. We apply both programs to a specific example: calculation of the response matrix of a 3He detector and unfolding of the neutron spectrum of a thick accelerator target using the calculated response matrix.

Weyrauch, M.; Dietz, E.; Matzke, M.

2002-01-01

25

Neutron flux spectra in the FFTF In-Reactor Thimble  

SciTech Connect

Neutron spectra measured in the FFTF In-Reactor Thimble (IRT) by proton recoil proportional counters, proton recoil emulsions, and passive dosimeters have been evaluated and compared with each other and with three-dimensionl diffusion theory calculated spectra for the purpose of validating the passive dosimeter spectrum adjustment technique. The least squares data adjustment code, FERRET, was used to combine measured reaction rates, calculated spectra, and dosimeter cross sections, resulting in adjusted spectra and cross sections with uncertainties and correlations that properly account for uncertainties and correlations on the input parameters.

Wootan, D.W.; Dobbin, K.D.; Schmittroth, F.A.; Roberts, J.H.

1982-12-01

26

Inversion of neutron/gamma spectra from scintillator measurements  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

27

Measurements of neutron spectra in HEU and LEU fuels  

Microsoft Academic Search

As part of the international Reduced Enrichment for Research and Test Reactors (RERTR) project, the Ford Nuclear Reactor (FNR) at the University of Michigan was selected as the test reactor to characterize the important differences between high (93%) and low (< 20%) enriched reactor fuels. A significant part of this program has involved comparative measurements of the neutron spectra. The

Wehe

1984-01-01

28

Inversion of neutron/gamma spectra from scintillator measurements  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

29

Neutron dose and energy spectra measurements at Savannah River Plant  

SciTech Connect

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

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

1987-08-01

30

Delayed neutron spectra from short pulse fission of uranium-235  

SciTech Connect

Delayed neutron spectra from individual short pulse (approx.50 ..mu..s) fission of small /sup 235/U samples (50 mg) were measured using a small (5 cm OD x 5 cm length) NE 213 neutron spectrometer. The irradiating fast neutron flux (approx.10/sup 13/ neutrons/cm/sup 2/) for these measurements was provided by the Godiva fast burst reactor at the Los Alamos Critical Experiment Facility (LACEF). A high speed pneumatic transfer system was used to transfer the 50 mg /sup 235/U samples from the irradiation position near the Godiva assembly to a remote shielded counting room containing the NE 213 spectrometer and associated electronics. Data were acquired in sixty-four 0.5 s time bins and over an energy range 1 to 7 MeV. Comparisons between these measurements and a detailed model calculation performed at Los Alamos is presented.

Atwater, H.F.; Goulding, C.A.; Moss, C.E.; Pederson, R.A.; Robba, A.A.; Wimett, T.F.; Reeder, P.; Warner, R.

1986-01-01

31

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

32

Neutron spectra at flight altitudes and their radiological estimation  

NASA Astrophysics Data System (ADS)

Since the publication of the ICRP-report 60, air crews and other frequently flying persons are considered as occupationally exposed people. At civil flight levels neutrons contribute the major part to the radiologically relevant dose to men. The quantification of the neutron dose, and herewith the radiation risk due to neutrons, suffers from spectral data available especially in the energy range above 20 MeV. Experimental data were recently obtained at a low flight level on top of the mountain Zugspitze at 3000 m using a modified Bonner sphere spectrometer. The resulting spectra are compared with Monte-Carlo transport calculations from top of the atmosphere down to 700 g/cm^2. These data and others from the literature are used to calculate operational and risk related quantities, i.e. ambient dose equivalent and effective dose.

Schraube, H.; Leuthold, G.; Roesler, S.; Heinrich, W.

33

Neutron spectra from deuteron and proton bombardment of thick lithium targets: potential for neutron therapy  

Microsoft Academic Search

Neutron energy spectra and yields produced by the bombardment of thick lithium targets by deuterons and protons have been measured using the time-of-flight method. Measurements were made at angles up to 45 degrees for deuteron energies of 8, 12 and 15 MeV and a proton energy of 15 MeV. The average neutron energy of the (d,n) reactions is shown to

C E Nelson; F O Purser; P Von Behren; H W Newson

1978-01-01

34

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

35

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

SciTech Connect

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

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

2006-10-15

36

The measurement of neutron and neutron induced photon spectra in fusion reactor related assemblies  

NASA Astrophysics Data System (ADS)

The spectral neutron and photon fluence (or flux) measured outside and inside of assemblies related to fusion reactor constructions are basic quantities of fusion neutronics. The comparison of measured spectra with the results of MCNP neutron and photon transport calculations allows a crucial test of evaluated nuclear data as generally used in fusion applications to be carried out. The experiments concern mixed neutron/photon fields with about the same intensity of the two components. An NE-213 scintillation spectrometer, well described by response matrices for both neutrons and photons, is used as proton-recoil and Compton spectrometer. The experiments described here in more detail address the background problematic of two applications, an iron benchmark experiment with an ns-pulsed neutron source and a deep penetration mock-up experiment for the investigation of the ITER in-board shield system. The measured spectral neutron and photon fluences are compared with spectra calculated with the MCNP code on the basis of FENDL-1 data. The agreement is better than 10% except for the photon fluence from the iron benchmark experiment, which is underestimated in the calculations by 25%.

Unholzer, S.; Freiesleben, H.; Klein, H.; Seidel, K.

2002-01-01

37

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

38

Neutron fluences and energy spectra in the Cosmos-2044 biosatellite orbit.  

PubMed

Joint Soviet-American measurements of the neutron component of space radiation (SR) were carried out during the flight of the Soviet biosatellite Cosmos-2044. Neutron flux densities and differential energy spectra were measured inside and on the external surface of the spacecraft. Three energy intervals were employed: thermal (En < or = 0.2 eV), resonance (0.2 eV < En < 1.0 MeV) and fast (En > or = 1.0 MeV) neutrons. The first two groups were measured with U.S. 6LiF detectors, while fast neutrons were recorded both by U.S. fission foils and Soviet nuclear emulsions. Estimations were made of the contributions to absorbed and equivalent doses from each neutron energy interval and a correlation was presented between fast neutron fluxes, measured outside the satellite, and the phase of solar activity (SA). Average dose equivalent rates of 0.018 and 0.14 mrem d-1 were measured for thermal and resonance neutrons, respectively, outside the spacecraft. The corresponding values for fast neutrons were 3.3 (U.S.) and 1.8 (U.S.S.R.) mrem d-1. Inside the spacecraft, a value of 3.5 mrem d-1 was found. PMID:11537526

Dudkin, V E; Potapov YuV; Akopova, A B; Melkumyan, L V; Rshtuni ShB; Benton, E V; Frank, A L

1992-01-01

39

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

40

Oscillation spectra of neutron stars with strong magnetic fields  

NASA Technical Reports Server (NTRS)

The effects of strong frozen-in vertical magnetic fields on nonradial oscillation spectra in neutron stars are investigated theoretically, focusing on the surface layers near the polar cap of a cylindrically symmetric neutron-star model with shear-supporting crust and molten-crust oceans. The pulsation equations are derived; analytical estimates are obtained; and the results of numerical experiments are presented in tables and graphs. Significant modifications in the frequencies and displacements of the modes are found when a magnetic field is present: Alfven-like g modes (designated magneto-gravity), pseudotoroidal a modes with periods less than 100 ns for a 1-TG field, p-mode displacements almost totally parallel to the field, and a mode spectrum for periods of 100 microsec or more comprising only t, s, and p modes at 1 TG.

Carroll, B. W.; Savedoff, M. P.; Zweibel, E. G.; Hansen, C. J.; Mcdermott, P. N.

1986-01-01

41

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

42

Absorption Features in Spectra of Magnetized Neutron Stars  

SciTech Connect

The X-ray spectra of some magnetized isolated neutron stars (NSs) show absorption features with equivalent widths (EWs) of 50-200 eV, whose nature is not yet well known.To explain the prominent absorption features in the soft X-ray spectra of the highly magnetized (B{approx}10{sup 14} G) X-ray dim isolated NSs (XDINSs), we theoretically investigate different NS local surface models, including naked condensed iron surfaces and partially ionized hydrogen model atmospheres, with semi-infinite and thin atmospheres above the condensed surface. We also developed a code for computing light curves and integral emergent spectra of magnetized neutron stars with various temperature and magnetic field distributions over the NS surface. We compare the general properties of the computed and observed light curves and integral spectra for XDINS RBS 1223 and conclude that the observations can be explained by a thin hydrogen atmosphere above the condensed iron surface, while the presence of a strong toroidal magnetic field component on the XDINS surface is unlikely.We suggest that the harmonically spaced absorption features in the soft X-ray spectrum of the central compact object (CCO) 1E 1207.4-5209 (hereafter 1E 1207) correspond to peaks in the energy dependence of the free-free opacity in a quantizing magnetic field, known as quantum oscillations. To explore observable properties of these quantum oscillations, we calculate models of hydrogen NS atmospheres with B{approx}10{sup 10}-10{sup 11} G(i.e., electron cyclotron energy E{sub c,e}{approx}0.1-1 keV) and T{sub eff} = 1-3 MK. Such conditions are thought to be typical for 1E 1207. We show that observable features at the electron cyclotron harmonics with EWs {approx_equal}100-200 eV can arise due to these quantum oscillations.

Suleimanov, V. [Insitute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tuebingen (Germany); Kazan Federal University, Kremlevskaya str. 18, 42008 Kazan (Russian Federation); Hambaryan, V.; Neuhaeuser, R. [Astrophysikalisches Institut und Universitaets-Sternwarte Jena, Schillergaesschen 2-3, 07745 Jena (Germany); Potekhin, A. Y. [Ioffe Physical-Technical Institute, Politekhnicheskaya str., 26, St. Petersburg 194021 (Russian Federation); Pavlov, G. G. [Pennsylvania State University, 525 Davey Lab., University Park, PA 16802 (United States); Adelsberg, M. van [Kavli Institute for Theoretical Physics, Kohn Hall, University of California, Santa Barbara, CA 93106 (United States); Werner, K. [Insitute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tuebingen (Germany)

2011-09-21

43

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

44

Neutron activated switch  

DOEpatents

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

Barton, David M. (Espanola, NM)

1991-01-01

45

Enhanced NIF neutron activation diagnostics  

NASA Astrophysics Data System (ADS)

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 89Zr/89mZr 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.

2012-10-01

46

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

47

Chemical weapons detection by fast neutron activation analysis techniques  

NASA Astrophysics Data System (ADS)

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

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

1993-06-01

48

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

SciTech Connect

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

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

2008-01-01

49

Application of a Bonner sphere spectrometer for determination of the energy spectra of neutrons generated by ?1 MJ plasma focus.  

PubMed

The spectra of neutrons outside the plasma focus device PF-1000 with an upper energy limit of ?1 MJ was measured using a Bonner spheres spectrometer in which the active detector of thermal neutrons was replaced by nine thermoluminescent chips. As an a priori spectrum for the unfolding procedure, the spectrum calculated by means of the Monte Carlo method with a simplified model of the discharge chamber was selected. Differences between unfolded and calculated spectra are discussed with respect to properties of the discharge vessel and the laboratory layout. PMID:21133467

Krlk, M; Krsa, J; Velyhan, A; Scholz, M; Ivanova-Stanik, I M; Bienkowska, B; Miklaszewski, R; Schmidt, H; ?ez?, K; Klr, D; Kravrik, J; Kube, P

2010-11-01

50

PINOa tool for simulating neutron spectra resulting from the 7Li(p,n) reaction  

NASA Astrophysics Data System (ADS)

The 7Li(p,n) reaction in combination with a 3.7 MV Van de Graaff accelerator was routinely used at FZK to perform activation as well as time-of-flight measurements with neutrons in the keV-region. Planned new setups with much higher proton currents like SARAF and FRANZ and the availability of liquid-lithium target technology will trigger a renaissance of this method. A detailed understanding of the neutron spectrum is not only important during the planning phase of an experiment, but also for the analysis of activation experiments. Therefore, the Monte-Carlo based program PINO (Protons In Neutrons Out) was developed, which allows the simulation of neutron spectra considering the geometry of the setup and the proton-energy distribution.

Reifarth, R.; Heil, M.; Kppeler, F.; Plag, R.

2009-09-01

51

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

PubMed

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

Vega-Carrillo, H R; Hernndez-Dvila, V M; Aguilar, F; Paredes, L; Rivera, T

2014-01-01

52

AFITBUNKI: A Modified Iterative Code to Unfold Neutron Spectra from Bonner Sphere Detector Data.  

National Technical Information Service (NTIS)

The neutron spectrum unfolding code BUNKI, developed at the Naval Research Laboratory in 1983, was modified to incorporate a finer energy group structure, seven initial-guess spectra, and new dose conversion factors. The modified code, AFITBUNKI, unfolds ...

S. C. Miller

1993-01-01

53

Analytical functions to predict cosmic-ray neutron spectra in the atmosphere.  

PubMed

Estimation of cosmic-ray neutron spectra in the atmosphere has been an essential issue in the evaluation of the aircrew doses and the soft-error rates of semiconductor devices. We therefore performed Monte Carlo simulations for estimating neutron spectra using the PHITS code in adopting the nuclear data library JENDL-High-Energy file. Excellent agreements were observed between the calculated and measured spectra for a wide altitude range even at the ground level. Based on a comprehensive analysis of the simulation results, we propose analytical functions that can predict the cosmic-ray neutron spectra for any location in the atmosphere at altitudes below 20 km, considering the influences of local geometries such as ground and aircraft on the spectra. The accuracy of the analytical functions was well verified by various experimental data. PMID:16953673

Sato, Tatsuhiko; Niita, Koji

2006-09-01

54

Measurement of Time-Dependent Fast Neutron Energy Spectra in a Depleted Uranium Assembly.  

National Technical Information Service (NTIS)

Time-dependent neutron energy spectra in the range 0.6 to 6.4 MeV have been measured in a depleted uranium assembly. By selecting windows in the time range 0.9 to 82 ns after the beam pulse, it was possible to observe the change of the neutron energy dist...

S. Whittlestone

1980-01-01

55

Neutron yields and energy spectra from the thick target Li(p,n) source  

Microsoft Academic Search

Angle-dependent spectra of neutrons, emitted by a thick lithium target when bombarded with protons in the energy range 1.881-3 MeV, have been evaluated from experimental and theoretical values of the angular distribution of neutrons emitted in the 7Li(p,n)7Be reaction. The variation of d2N\\/dEnd Omega with proton energy at different angles of emission, and with angle of emission for different neutron

A. I. M. Ritchie

1976-01-01

56

Neutron Activation Diagnostics for FRCHX at AFRL  

Microsoft Academic Search

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

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

2009-01-01

57

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

NASA Astrophysics Data System (ADS)

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

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

1975-01-01

58

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; Sentkerestiov, J; Holyaka, R; Lahodov, Z; Bm, P

2010-10-01

59

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

NASA Astrophysics Data System (ADS)

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

?uran, I.; Bolshakova, I.; Viererbl, L.; Sentkerestiov, J.; Holyaka, R.; Lahodov, Z.; Bm, P.

2010-10-01

60

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

61

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

SciTech Connect

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

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

1995-05-23

62

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

63

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

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

64

Activities on Nuclear Data Measurements at Pohang Neutron Facility  

NASA Astrophysics Data System (ADS)

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

Kim, Guinyun

2009-03-01

65

14 MeV neutron spectra measurements with 4% energy resolution using a type IIa diamond detector  

Microsoft Academic Search

A natural diamond detector has been used as a neutron spectrometer to measure 14 MeV neutron spectra produced by a neutron generator. The spectrometer chain was energy calibrated with a 241Am alpha source; a resolution of 1.6% FWHM was observed. The 12C(n,?0)9Be reaction which occurs in diamond was used to measure the neutron spectra and the measured energy resolution at

M. Pillon; M. Angelone; A. V. Krasilnikov

1995-01-01

66

Measurement and Analysis of Neutron and Photon Flux Spectra Inside a Tungsten Block Irradiated with 14-MeV Neutrons  

NASA Astrophysics Data System (ADS)

Tungsten was selected as material for the divertor plates of fusion reactors and is therefore the object of investigations to check the status of different nuclear data libraries for fusion applications. A benchmark was performed by irradiating a W block with 14-MeV neutrons and measuring the induced neutron and photon flux spectra inside the block at four positions. Spectra measured are compared with spectra calculated on the basis of the European Fusion File EFF-2.4, the Fusion Evaluated Nuclear Data Libraries FENDL-1 and FENDL-2 using the Monte Carlo code MCNP-4C. Experiment and calculation are compared in detail and also in C/E-ratios (calculation/experiment) of significant fluence integrals.

Unholzer, S.; Angelone, M.; Batistoni, P.; Fischer, U.; Freiesleben, H.; Leichtle, D.; Negoita, C.; Pillon, M.; Seidel, K.

2005-05-01

67

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

68

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

SciTech Connect

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 of detector position behind these materials. The measured data were obtained using a NE-213 liquid scintillator using pulse-shape discrimination methods to resolve neutron and gamma ray pulse height data and spectral unfolding methods to convert these data to energy spectra. The calculated data were obtained using two-dimensional discrete ordinates radiation transport methods in a complex calculational network that takes into account the energy-angle dependence of the D-T neutrons and the nonphysical anomalies of the S/sub n/ method.

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

1980-08-01

69

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

NASA Astrophysics Data System (ADS)

Considerable interest has grown in the last decade in the use of CR-39 films in routine neutron monitoring and dosimetry. In addition, work in neutron spectrometry has been undertaken by various workers ( Decossas et al., 1984; Faermann et al., 1983; Fews et al., 1984; Turner et al., 1984). In the present study metal matrix composites (MMC) samples of Pb-Li, Pb-Cd, Al-Li and Al-B 4C were prepared by using powder metallurgy and alloying elements techniques. The density was obtained for these MMC samples in the range of 80-90% of the metal density. Degraded neutron spectra were obtained by exposing these samples to a 252Cf source housed in a camera and the detector used was CR-39 films covered with a 1 mm PE radiator. These spectra have also been validated through Monte Carlo Neutron and Photon Transport Code (1983).

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

1998-06-01

70

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

NASA Astrophysics Data System (ADS)

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

Nguyen, Hung Van

1997-09-01

71

Neutrons for Science and Industry - Uppsala Neutron Beam Activities  

SciTech Connect

A wide programme on neutron-induced data for various applications is running at the 20-180 MeV neutron beam facility at the The Svedberg Laboratory, Uppsala. The main research areas are nuclear data for accelerator-driven transmutation of nuclear waste, single-event effects, and dose effects in fast-neutron cancer therapy and aviation environments. In addition, experiments on fundamental nuclear physics are undertaken. Moreover, commercial device testing motivated by single-event effects is a growing activity.

Blomgren, J. [Department of Neutron Research, Uppsala University (Sweden)

2005-05-24

72

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

73

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

74

Forensic neutron activation analysis the Japanese scene  

Microsoft Academic Search

The progress of forensic neutron activation analysis (FNAA) in Japan is described. FNAA began in 1965 and during the past 20 years many cases have been handled; these include determination of toxic materials, comparison examination of physical evidences (e.g., paints, metal fragments, plastics and inks) and drug sample differentiation. Neutron activation analysis is applied routinely to the scientific criminal investigation

T. Kishi

1987-01-01

75

X-ray spectra of bursting neutron stars and the color temperature versus luminosity diagram  

Microsoft Academic Search

Atmospheric models and emitted X-ray spectra are calculated for X-ray bursting neutron stars taking into account the effects of Comptonization and free-free and bound-free emission\\/absorption. The color temperature obtained from the calculated X-ray spectra are significantly higher than the effective temperatures. The theoretical color temperature versus luminosity diagram is in good agreement with the observational diagram for MXB 1636-536 which

T. Ebisuzaki; K. Nomoto

1986-01-01

76

Variations in Spectra of Resonance Neutron Capture Gamma Rays in Indium  

Microsoft Academic Search

Measurements are reported of the 0-350 kev portion of the gamma-ray spectra following neutron capture in the 1.46-, 3.86-, and 9.10-ev resonances of the 49In115 target nucleus. The prominent features of the spectra are significantly different for the three resonances as indicated by the ratios of relative intensities of the 67-, 98-, 188-, and 280-kev gamma rays. The 0-1600 kev

J. E. Draper; C. A. Fenstermacher; H. L. Schultz

1958-01-01

77

VARIATIONS IN SPECTRA OF RESONANCE NEUTRON CAPTURE GAMMA RAYS IN INDIUM  

Microsoft Academic Search

Measurements are reported of the 0 to 350 kev portion of the gamma-ray ; spectra following neutron capture in the 1.46-, 3.86-, and 9.10-ev resonances of ; the In¹¹⁵ target nucleus. The prominent features of the spectra ; are significantly different for the three resonances as indicated by the ratios ; of relative intensities of the 67-, 98-, 188-. and

J. E. Draper; C. A. Fenstermacher; H. L. Schultz

1958-01-01

78

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

79

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

80

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

SciTech Connect

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

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

1993-12-01

81

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

82

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

Microsoft Academic Search

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

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

2007-01-01

83

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

84

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

Microsoft Academic Search

When endoergic (p, n) reactions are used for the production of neutrons, the energy distribution of the neutron flux depends on the energy of the protons. By changing the proton energy, certain neutron reactions are selectively excited. This effect can then be used to determine particular elements in matrices that contribute overwhelming interference when the conventional techniques of thermal- or

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

1990-01-01

85

An automated facility for neutron activation analysis  

Microsoft Academic Search

A fully automated neutron activation analysis (NAA) facility has been constructed at the Whiteshell Nuclear Research Establishment. This high-capacity facility has been designed for use with a wide variety of neutron sources, including Canada's SLOWPOKE II and MAPLE research reactors. Its pneumatic transfer system is driven by a Square-D Model 500 programmable controller, linked in turn to a Nuclear Data

M. Attas; J. D. Chen; E. A. Hildebrandt

1987-01-01

86

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

87

Application of a Bonner sphere spectrometer for determination of the energy spectra of neutrons generated by {approx_equal}1 MJ plasma focus  

SciTech Connect

The spectra of neutrons outside the plasma focus device PF-1000 with an upper energy limit of {approx_equal}1 MJ was measured using a Bonner spheres spectrometer in which the active detector of thermal neutrons was replaced by nine thermoluminescent chips. As an a priori spectrum for the unfolding procedure, the spectrum calculated by means of the Monte Carlo method with a simplified model of the discharge chamber was selected. Differences between unfolded and calculated spectra are discussed with respect to properties of the discharge vessel and the laboratory layout.

Kralik, M. [Czech Metrology Institute, 102 00 Prague 10 (Czech Republic); Krasa, J.; Velyhan, A. [Institute of Physics, v.v.i., ASCR, 182 21 Prague 8 (Czech Republic); Scholz, M.; Ivanova-Stanik, I. M.; Bienkowska, B.; Miklaszewski, R.; Schmidt, H. [Institute of Plasma Physics and Laser Microfusion, 00-908 Warsaw (Poland); Rezac, K.; Klir, D.; Kravarik, J.; Kubes, P. [Czech Technical University, 166 27 Prague 6 (Czech Republic)

2010-11-15

88

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

NASA Astrophysics Data System (ADS)

A laser-induced repetitively operated fast neutron source was developed for applications in laser-driven nuclear physics research. The developed neutron source, which has a neutron yield of approximately 4 105 n/pulse and can be operated up to a pulse repetition rate of 10 Hz, was applied for a gold activation analysis. Relatively strong delayed gamma spectra of the activated gold were measured at 333 keV and 355 keV, and proved the possibility of the neutron source for activation analyses. In addition, the nuclear reactions responsible for the measured gamma spectra of gold were elucidated by the 14 MeV fast neutrons resulting from the D(t,n)He4 nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T3.

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

2012-12-01

89

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

90

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...

91

Neutron activation analysis in the life sciences  

NASA Astrophysics Data System (ADS)

Development of methods for instrumental neutron activation analysis (INAA) and their applications in the life sciences are reviewed. Emphasis is placed on epithermal activation with reactor neutrons (ENAA), and the advantages of this technique in analysis of environmental objects are shown. The results of applied INAA studies in the field of the life sciences carried out at the world's leading nuclear centers are reported. Experience in employing a radioanalytical complex at the IBR-2 reactor (Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna) for such studies is summarized.

Frontasyeva, M. V.

2011-03-01

92

Activities on Nuclear Data Measurements at Pohang Neutron Facility  

SciTech Connect

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

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

2009-03-31

93

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

94

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

NASA Astrophysics Data System (ADS)

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

Dima, M.; Pepelyshev, Yu.

2013-07-01

95

Spectra of photons and neutrons generated in a heterogeneous head of a 15 MV LINAC at differents field sizes  

NASA Astrophysics Data System (ADS)

Spectra of photons and neutrons were calculated, using the Monte Carlo code MCNP-5 using the e/p/n mode. A heterogeneous model was used to define the linac head where the collimators were modeled to produce five different treatment fields at the isocenter. Photon and neutron spectra were estimated in several points along two directions from the isocenter. The total photon fluence beyond 60 cm behaves according to 1/r2 rule, while total neutron fluence, beyond 80 cm, can be described by diffusion theory using an infinite plane as a neutron source.

Benites-Rengifo, J. L.; Vega-Carrillo, H. R.; Velazquez-Fernandez, J. B.

2012-10-01

96

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

NASA Astrophysics Data System (ADS)

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

Forrest, C. J.; Radha, P. B.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Pruyne, A.; Romanofsky, M.; Sangster, T. C.; Shoup, M. J.; Stoeckl, C.; Casey, D. T.; Gatu-Johnson, M.; Gardner, S.

2012-10-01

97

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

98

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

99

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

SciTech Connect

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

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

1998-11-06

100

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

SciTech Connect

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

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

1999-03-01

101

Measurements of Cosmic-Ray Neutron Energy Spectra from Thermal to 15 MeV with Bonner Ball Neutron Detector in Aircraft  

Microsoft Academic Search

Cosmic-ray neutron energy spectra from thermal to 15MeV were measured with a multimoderator spectrometer known as the Bonner Ball Neutron Detector (BBND) at aviation altitude (911 km). Four flights were carried out around Nagoya Airport in Japan. The measured data were unfolded using the maximum entropy deconvolution code MAXED, and the derived spectra agreed with the calculated results using the

Kazuaki YAJIMA; Hiroshi YASUDA; Masashi TAKADA; Tatsuhiko SATO; Tateo GOKA; Haruhisa MATSUMOTO; Takashi NAKAMURA

2010-01-01

102

A low-cost system for rapid automatic neutron activation analysis at small research reactors  

Microsoft Academic Search

A system for rapid automatic neutron activation analysis is governed by software performing irradiation control, neutron flux\\u000a monitoring and gamma-spectrometry with real-time correction of counting losses as well as spectra evaluation, nuclide identification\\u000a and calculation of concentrations in a fully automatic flow of operations.1,2 Elemental concentrations are derived from a list of experimentally determined specific saturation activities. To expand this

G. P. Westphal; F. Grass; H. Lemmel; J. Sterba

2007-01-01

103

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

104

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

PubMed

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

Cottam, J; Paerels, F; Mendez, M

2002-11-01

105

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

106

Relativistic neutrons in active galactic nuclei  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

107

Neutron and proton activation measurements from SKYLAB  

NASA Astrophysics Data System (ADS)

Radioactivity induced by high-energy protons and secondary neutrons (from nuclear interactions) in various samples returned from different locations in Skylab was measured directly by gamma-ray spectroscopy measurements of decay gamma rays from the samples. Incident fluxes were derived from the activation measurements, using known nuclear cross-section. Neutron and proton flux values were found to range from 0.2 to 5 particles/sq cm-sec, depending on the energy range and location in Skylab. The thermal neutron flux was less than 0.07 neutrons/sq cm-sec. The results are useful for data analysis and planning of future high-energy astronomy experiments.

Fishman, G. J.

1974-10-01

108

Neutron and proton activation measurements from Skylab  

NASA Technical Reports Server (NTRS)

Radioactivity induced by high-energy protons and secondary neutrons (from nuclear interactions) in various samples returned from different locations in Skylab was measured directly by gamma-ray spectroscopy measurements of decay gamma rays from the samples. Incident fluxes were derived from the activation measurements, using known nuclear cross-section. Neutron and proton flux values were found to range from 0.2 to 5 particles/sq cm-sec, depending on the energy range and location in Skylab. The thermal neutron flux was less than 0.07 neutrons/sq cm-sec. The results are useful for data analysis and planning of future high-energy astronomy experiments.

Fishman, G. J.

1974-01-01

109

Cross sections and differential spectra for reactions of 2-20 MeV neutrons on /sup nat/Ni  

SciTech Connect

This report summarizes product yields, secondary n,p and (alpha) spectra, and ..gamma..-ray spectra calculated for incident neutrons of 2-20 MeV on /sup nat/Ni targets. Results are all from the code ALICE, using the version ALISO which does weighting of results for targets which are a mix of isotpoes. Where natural isotopic targets are involved, yields and n,p,..cap alpha.. sepctra will be reported weighted over isotopic yeilds. Gamma-ray spectra, however, will be reported for the most abundant isotope. We present product yields versus incident neutron energy, n,p,..cap alpha.. spectra versus incident neutron energy, and calculated ..gamma..-ray spectra

Blann, M.; Komoto, T.T.

1988-01-01

110

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

Microsoft Academic Search

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

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

1996-01-01

111

Measurements and calculations of neutron spectra from 35 MeV deuterons on thick lithium for the FMIT facility  

Microsoft Academic Search

Neutron yields and energy spectra were measured for 35 MeV deuterons on a thick target of natural lithium. Data were obtained using the time-of-flight technique over an angular range of 0° the 150° and for neutron energies from about 1 to 50 MeV. A simple nuclear model that describes the differential cross sections of neutron production was adjusted to agree

D. L. Johnson; F. M. Mann; J. W. Watson; J. Ullman; W. G. Wyckoff

1978-01-01

112

Monte Carlo simulations of down-scattered neutron and knock-on deuteron spectra in deuterium-tritium capsule implosions  

NASA Astrophysics Data System (ADS)

A Monte Carlo particle tracking (MCPT) code has been developed and coupled to hydrodynamic simulations to generate and track primary and scattered neutrons in addition to scattered charged particles by post-processing. This code uses one dimensional (1-D) deuterium-tritium implosion profiles, and the computed down-scattered neutron and knock-on deuteron spectra are analyzed for different areal densities. The mixing effects on the spectra of down-scattered neutron and knock-on deuteron are also investigated. The implementation of the numerical scheme is analyzed, and the particle splitting technique is adopted, which is proven to efficiently reduce computational effort.

Zhao, Bin; Zheng, Jian

2013-12-01

113

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

114

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

115

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

116

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

117

Radiogenic argon determination by neutron activation analysis  

Microsoft Academic Search

For the determination of radiogenic argon by means of thermal neutron activation analysis, the argon extracted from the sample is purified with metallic titanium heated at 800C then slowly cooled to 200C, after the sample has melted in vacuo . The argon is then collected in a quartz vial, the gas being adsorbed on 0.240 g of charcoal which is

M. Soroiu; M. Cerei; M. Oncescu; A. Danis; C. M. Ntescu

1965-01-01

118

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

119

Neutron Activation Analysis for the Demonstration of Amphibolite Rock-Weathering Activity of a Yeast  

PubMed Central

Neutron activation analysis was employed in a survey of weathering abilities of rock surface microorganisms. A yeast isolated from an amphibolite of a megalithic grave was found actively to concentrate, in media and in or on cells, iron and other elements when grown in the presence of ground rock. This was demonstrated by comparing a spectrum of neutron-activated amphibolite powder (particle size, 50 to 100 ?m) with the spectra of neutron-activated, lyophilized yeast cells which had grown with or without amphibolite powder added to different media. The most active yeast (IFAM 1171) did not only solubilize Fe from the rock powder, but significant amounts of Co, Eu, Yb, Ca, Ba, Sc, Lu, Cr, Th, and U were also mobilized. The latter two elements occurred as natural radioactive isotopes in this amphibolite. When the yeast cells were grown with neutron-activated amphibolite, the cells contained the same elements. Furthermore, the growth medium contained Fe, Co, and Eu which had been solubilized from the amphibolite. This indicates the presence, in this yeast strain, of active rockweathering abilities as well as of uptake mechanisms for solubilized rock components.

Rades-Rohkohl, E.; Hirsch, P.; Franzle, O.

1979-01-01

120

Analysis of medicinal plant extracts by neutron activation method.  

National Technical Information Service (NTIS)

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

S. M. Vaz

1995-01-01

121

Neutron Yield Measurements via Aluminum Activation  

SciTech Connect

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

None

1999-12-08

122

Capillary neutron optics for prompt gamma activation analysis  

SciTech Connect

A neutron lens has been constructed to focus neutrons from the exit of Neutron Guide 7 (NG7), Prompt Gamma Activation Analysis (PGAA) station at the National Institute of Standards and Technology Cold Neutron Research Facility. The lens is made with polycapillary fibers drawn from lead silicate glass with a critical angle of 11.0 mrad/nm.

Chen, H. [National Institute of Standards and Technology, Gaithersburg, MD (United States); Sharov, V.A.; Xiao, Q.F. [X-Ray Optical Systems, Inc., Albany, NY (United States)] [and others

1995-12-31

123

A compilation of fast neutron interactions, cross sections, gamma spectra and gamma decay energies  

Microsoft Academic Search

Fast neutron activation analysis (FNAA) is an excellent non-destructive assay technique for selected nuclides such as Al, Cu, F, N, O, P, and Si and may be used to identify other trace elements such as Ag, Ba, Ca, Cd, Fe, Ga, Mg, Nd, Pd, Rb, Se, Sr, Th, U, Zn, and Zr when other, more sensitive methods are not available

John W. McKlveen

1981-01-01

124

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

SciTech Connect

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

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

2013-09-01

125

Isolation of Pseudomonas aeruginosa specific phages with broad activity spectra.  

PubMed

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

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

2009-08-01

126

Measurement and prediction of neutron spectra in the Kalpakkam mini reactor (KAMINI).  

PubMed

Kalpakkam mini (KAMINI) reactor is the newest research reactor built in India. Operated at the Indira Gandhi Centre for Atomic Research, Kalpakkam, it has the unique distinction of being the only operating pool-type reactor in the world at present fuelled by 233U and aluminium alloy. Neutron spectra have been measured by the multi-foil irradiation method at the beam tube ends of this reactor. The spectra unfolding have been done, by using SAND-II computer code. Thus the total and thermal flux at the beam tube ends have been measured. The theoretical spectrum generated by the computer codes SMAXY and COMESH and WIMS cross-section data library was compared with the measured spectrum for one of the beam tubes and found to match well. A new 620-group cross-section data library generated at our centre was tested with SAND-II for the same set of measurements. Use of the new library results in slightly higher measured total fluxes and smoother spectra shapes. PMID:12137023

Mohapatra, D K; Mohanakrishnan, P

2002-07-01

127

Instrumental neutron activation analysis of gunpowder residues  

Microsoft Academic Search

A procedure has been developed for the detection of gunpowder residues deposited on the hand of a person firing a gun. The\\u000a method is based on neutron activation analysis of the antimony level on the surface of the hand. The surface materials are\\u000a removed by a film made by spraying a 4% solution of cellulose acetate in acetone, which sets

A. Albu-Yaron; S. Amiel

1972-01-01

128

Neutron activation analysis of lithium niobate  

Microsoft Academic Search

A radiochemical neutron activation analysis procedure for the determination of Ta, W, Ir, Pt, Au, Cu, Cr, Co and Zn in lithium niobate has been developed. The method involves a one-step removal of radioactive nuclides of Nb, Ta and W representing the dominating radioactivity of the irradiated sample. After irradiation, the sample is fused with inactive carriers and Na2O2 in

R. Verma; J. Arunachalam; S. Gangadharan

1992-01-01

129

Instrumental and Organizational Aspects of a Neutron Activation Analysis Laboratory.  

National Technical Information Service (NTIS)

Contents: Introduction; Principles of Instrumental Neutron Activation Analysis; Big Samples Neutron Irradiation System; Carbonfiber Autonomous Facility for Irradiation and Analysis; Detectors for I.N.A.A; Process Improvement by Quality Assurance; Total Qu...

P. Bode

1996-01-01

130

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

131

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

SciTech Connect

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

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

1996-12-31

132

Dynamics of myoglobin: Comparison of simulation results with neutron scattering spectra  

SciTech Connect

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 dominant contributions to the atomic displacements on a time scale of 0.3-100 ps (100-0.3 cm{sup {minus}1}). Analysis of the simulations shows that at low temperatures a harmonic description of the molecule is appropriate and that the molecule is trapped in localized regions of conformational space. At higher temperatures the scattering arises from a combination of vibrations within wells (substrates) and transitions between them; the latter contribute to the quasi-elastic scattering.

Smith, J.; Kuczera, K.; Karplus, M. (Harvard Univ., Cambridge, MA (United States))

1990-02-01

133

A parametric model to describe neutron spectra around high-energy electron accelerators and its application in neutron spectrometry with Bonner Spheres  

NASA Astrophysics Data System (ADS)

Due to the increased interest of the scientific community in the applications of synchrotron light, there is an increasing demand of high-energy electron facilities, testified by the construction of several new facilities worldwide. The radiation protection around such facilities requires accurate experimental methods to determine the dose due to prompt radiation fields. Neutron fields, in particular, are the most complex to measure, because they extend in energy from thermal (10 -8 MeV) up to hundreds MeV and because the responses of dosemeters and survey meters usually have large energy dependence. The Bonner Spheres Spectrometer (BSS) is in practice the only instrument able to respond over the whole energy range of interest, and for this reason it is frequently used to derive neutron spectra and dosimetric quantities in accelerator workplaces. Nevertheless, complex unfolding algorithms are needed to derive the neutron spectra from the experimental BSS data. This paper presents a parametric model specially developed for the unfolding of the experimental data measured with BSS around high-energy electron accelerators. The work consists of the following stages: (1) Generation with the FLUKA code, of a set of neutron spectra representing the radiation environment around accelerators with different electron energies; (2) formulation of a parametric model able to describe these spectra, with particular attention to the high-energy component (>10 MeV), which may be responsible for a large part of the dose in workplaces; and (3) implementation of this model in an existing unfolding code.

Bedogni, Roberto; Pelliccioni, Maurizio; Esposito, Adolfo

2010-03-01

134

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

135

Updated summary of measurements and calculations of neutron and gamma-ray emission spectra from spheres pusled with 14-MeV neutrons: Revision 1  

SciTech Connect

New measurements of the neutron and gamma-ray emission spectra from materials of interest to thermonuclear reactors with a 14 MeV neutron source were done during 1986 and 1987. These measurements characterized by better resolution than those reported in the Summary published in 1982, were performed using the pulsed sphere and time-of-flight techniques. The detector used in these measurements was a NE-213 cylinder, 5.08 cm in diameter by 5.08 cm thick. The new measurements include the following materials: Be, C, N, H/sub 2/O, C/sub 2/F/sub 4/ (teflon), Al, Si, Ti, Fe, Cu, Ta, W, Au, Pb, /sup 232/Th, and /sup 238/U. For all these materials, both the neutron and gamma emission spectra were measured. A complete tabulation of all the measurements done under the Pulse Sphere Program is presented. 37 refs., 1 tab.

Hansen, L.F.; Goldberg, E.; Howerton, R.J.; Komoto, T.T.; Pohl, B.A.

1989-01-19

136

X-ray spectra and atmospheric structures of bursting neutron stars  

NASA Technical Reports Server (NTRS)

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

Ebisuzaki, Toshikazu

1987-01-01

137

Active and sterile neutrino mass effects on beta decay spectra  

SciTech Connect

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

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

2013-06-10

138

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

SciTech Connect

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

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

1999-09-01

139

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

SciTech Connect

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

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

2002-01-01

140

Neutron Energy Spectra from the Thick Target exp 9 Be(D,N) exp 10 B Reaction.  

National Technical Information Service (NTIS)

The energy spectrum of neutrons emitted when deuterons impinge on a thick beryllium target has been measured using an NE213 scintillation detector and the time-of-flight technique. Spectra were measured at angles of 0, 30, 45, 60, 90, 120 and 150 exp 0 fo...

S. Whittlestone

1976-01-01

141

Isotopic Identification of Neutron Resonances of Cd, Sb, Os, and Pt from Capture Gamma-Ray Spectra  

Microsoft Academic Search

The Argonne fast chopper has been used in conjunction with a 3-variable magnetic-tape recording system to demonstrate the high efficiency and sensitivity of isotopic identification of neutron resonances by observation of capture gamma rays. A discussion of features of capture spectra which can be useful in isotopic assignment is presented as well as results for resonances in natural Cd, Sb,

H. E. Jackson; L. M. Bollinger

1961-01-01

142

Simultaneous Evaluation of Neutron Spectra and 1-MeV-Equivalent (Si) Fluences at SPR-III and ACRR  

Microsoft Academic Search

Simultaneous least-squares adjustment of calculated neutron spectra in the central cavity of SPR-III and in the Pb-B4C bucket at ACRR is described, and the resulting 1-MeV-equivalent fluences are compared with damage measurements in 2N2222A transistors.

John G. Williams; Patrick J. Griffin; Donald B. King; David W. Vehar; Tim Schnauber; S. Michael Luker; K. Russell De Priest

2007-01-01

143

Neutron activation analysis of inorganic fillers for polymer composites  

Microsoft Academic Search

The neutron activation analysis of inorganic fillers for organic composites has been made for the purpose of studying the radioactive nuclides produced in polymer composites by neutron irradiation. Five kinds of fillers such as glass fiber, mica flake, quartz powder, alumina fiber and silicon carbide fiber were chosen as typical samples. In the neutron-irradiated glass fiber and mica flake, various

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

1996-01-01

144

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

145

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.; Krsa, A.; Trkov, A.

2013-08-01

146

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

147

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

148

Measurement of Neutron Emission Spectra in Li(d,xn) Reaction with Thick and Thin Targets for 40-MeV Deuterons  

SciTech Connect

To improve the data accuracy of the neutron emission spectra of the {sup nat}Li(d,xn) reaction that will be used as the neutron source in the International Fusion Materials Irradiation Facility, the authors have measured the neutron emission spectra from thick and thin lithium targets bombarded by 40-MeV deuterons at the AVF cyclotron (K = 110) facility of Tohoku University. The neutron spectra were measured at nine laboratory angles between 0 and 110 deg with the time-of-flight method using a beam-swinger system and a well-collimated neutron flight channel, obtained over almost the entire energy range of secondary neutrons using a two-gain method. The data obtained revealed the shape and angular dependence of emission spectra up to the high-energy region called a 'high-energy tail'. The experimental results are compared with other experimental data and calculations.

Hagiwara, M. [Tohoku University Cyclotron and Radioisotope Center (Japan); Itoga, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Kawata, N. [Tohoku University Cyclotron and Radioisotope Center (Japan); Hirabayashi, N. [Tohoku University Cyclotron and Radioisotope Center (Japan); Oishi, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Yamauchi, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Baba, M. [Tohoku University Cyclotron and Radioisotope Center (Japan); Sugimoto, M. [Japan Atomic Energy Research Institute (Japan); Muroga, T. [National Institute for Fusion Science (Japan)

2005-11-15

149

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

150

Feasibility of Multicomponent Activation Detectors for Fusion Reactor Neutronics Measurements.  

National Technical Information Service (NTIS)

For the development of fusion reactor blankets, neutron flux spectrum measurements with activation detectors will be needed. In Multicomponent Activation Detectors (MAD) several detector materials are irradiated and measured simultaneously for gamma-activ...

J. V. Sandberg

1982-01-01

151

Transport analysis of measured neutron leakage spectra from spheres as tests of evaluated high energy cross sections  

NASA Technical Reports Server (NTRS)

Integral tests of evaluated ENDF/B high-energy cross sections have been made by comparing measured and calculated neutron leakage flux spectra from spheres of various materials. An Am-Be (alpha,n) source was used to provide fast neutrons at the center of the test spheres of Be, CH2, Pb, Nb, Mo, Ta, and W. The absolute leakage flux spectra were measured in the energy range 0.5 to 12 MeV using a calibrated NE213 liquid scintillator neutron spectrometer. Absolute calculations of the spectra were made using version 3 ENDF/B cross sections and an S sub n discrete ordinates multigroup transport code. Generally excellent agreement was obtained for Be, CH2, Pb, and Mo, and good agreement was observed for Nb although discrepancies were observed for some energy ranges. Poor comparative results, obtained for Ta and W, are attributed to unsatisfactory nonelastic cross sections. The experimental sphere leakage flux spectra are tabulated and serve as possible benchmarks for these elements against which reevaluated cross sections may be tested.

Bogart, D. D.; Shook, D. F.; Fieno, D.

1973-01-01

152

Analysis of neutron emission spectra for 30 50 MeV ?-particle induced reactions in thick targets  

NASA Astrophysics Data System (ADS)

Comparisons of calculated neutron yield distributions from ?-particle induced reactions on thick targets are made with measured data to analyze the initial reaction process in the framework of the exciton (hybrid) model code ALICE91 (M. Blann, Lawrence Livermore National Laboratory Report UCID 19614, 1982). We have considered two reaction mechanisms: dissolution of the ? in the nuclear field, and preequilibrium processes initiated by ?-nucleon collisions. Both these processes seem to contribute to the emitted neutron spectra in varying proportions depending on the incident ? energy and possibly on the target nucleus. Contributions from other processes appear to be non-negligible.

Dhar, D.; Roy, S. N.; Nandy, Maitreyee; Sarkar, P. K.

2003-06-01

153

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

154

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

PubMed Central

Hydration effects on protein dynamics were investigated by comparing the frequency dependence of the calculated neutron scattering spectra between full and minimal hydration states at temperatures between 100 and 300 K. The protein boson peak is observed in the frequency range 14 meV at 100 K in both states. The peak frequency in the minimal hydration state shifts to lower than that in the full hydration state. Protein motions with a frequency higher than 4 meV were shown to undergo almost harmonic motion in both states at all temperatures simulated, whereas those with a frequency lower than 1 meV dominate the total fluctuations above 220 K and contribute to the origin of the glass-like transition. At 300 K, the boson peak becomes buried in the quasielastic contributions in the full hydration state but is still observed in the minimal hydration state. The boson peak is observed when protein dynamics are trapped within a local minimum of its energy surface. Protein motions, which contribute to the boson peak, are distributed throughout the whole protein. The fine structure of the dynamics structure factor is expected to be detected by the experiment if a high resolution instrument (

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

2008-01-01

155

Study on the neutron activation analysis  

NASA Astrophysics Data System (ADS)

A preconcentration of trace impurities and radiochemical separation scheme for neutron activation analysis is developed for the determination of 23 elements in nuclear fuel uranium. PH 3 solution of sulfuric acid contained uranium ions(VI) is loaded on anion-exchange resin column (Dowex 1 x 8, 100 - 200 Mesh) for separation of impurities from uranium. All of uranium ions are absorped on the anion exchange resin but 23 elements of impurities are eluated over 98%. After irradiation of the eluate the radiochemical separation scheme is applied. The scheme is based on a group separation using ion-exchange resin and mineral exchanger. Present work has employed mineral acids and their partly organic mixture excluding HF as the media as well as common glass wares. For the determination, gamma-ray spectroscopy using 3 in x 3 in NaI (TI) detector and a single comparator method are used.

Yang, K. R.; Kim, N. B.; Lee, K. Y.

156

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

157

Differential neutron energy spectra measured on spacecraft in low Earth orbit.  

PubMed

Two methods for measuring neutrons in the range from thermal energies to dozens of MeV were used. In the first method, alpha-particles emitted from the 6Li(n,alpha)T reaction are detected with the help of plastic nuclear track detectors, yielding results on thermal and resonance neutrons. Also, fission foils are used to detect fast neutrons. In the second method, fast neutrons are recorded by nuclear photographic emulsions (NPE). The results of measurements on board various satellites are presented. The neutron flux density does not appear to correlate clearly with orbital parameters. Up to 50% of neutrons are due to albedo neutrons from the atmosphere while the fluxes inside the satellites are 15-20% higher than those on the outside. Estimates show that the neutron contribution to the total equivalent radiation dose reaches 20-30%. PMID:11537519

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

1990-01-01

158

Measurements and interpretation of TT and down-scattered DT neutron spectra at OMEGA and the NIF  

NASA Astrophysics Data System (ADS)

The Magnetic Recoil neutron Spectrometers (MRS) on OMEGA and the National Ignition Facility (NIF) have been used to measure inertial confinement fusion (ICF) neutron spectra above En 4 MeV from DT and THD implosions with varying fuel composition and areal density (?R). In the high-?R DT implosions at the NIF, multiple-neutron scattering in the fuel is observed for the first time. In implosions with high tritium content, the TT neutron spectrum dominates and can be distinguished from other components in the neutron spectrum. In this work, we use an ensemble of measurements with varying conditions to separate the TT and down-scattered DT contributions and to improve our understanding of the shape of the TT spectrum and the source of DT down-scatter. The work motivates the need for high-resolution measurements of the ICF neutron spectrum at low energies (En<5 MeV). This work was supported in part by the U.S. DOE, LLNL and LLE.

Gatu-Johnson, M.; Casey, D. T.; Frenje, J.; Li, C.; Sguin, F.; Petrasso, R.; Glebov, V.; Knauer, J.; Sangster, T. C.; Bionta, R.; Edwards, J.; Glenzer, S.; Hatchett, S.; Landen, O.; MacKinnon, A.; McNabb, D.; Munro, D.; Pino, J.; Sepke, S.; Springer, P.; Kilkenny, J.

2012-10-01

159

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

NASA Astrophysics Data System (ADS)

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

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

1989-06-01

160

Bayesian methods for inferring soil contamination profiles from neutron-induced gamma-ray spectra  

NASA Astrophysics Data System (ADS)

Prompt-gamma neutron-activation analysis offers a potential for noninvasive characterization of contaminated soil. In this method, neutron irradiation of the surface induces a capture-gamma-ray signature from the contaminant which can be identified in a gamma-ray energy spectrum measured at the surface. The fundamental problem is to infer the contaminant concentration profile from the measured capture-gamma-ray intensities which include gamma-ray contributions from all soil depths. Radiation-transport theory is used to simulate the neutron field and both the uncollided and first-scattered gamma-ray components in uniform soil compositions. Simulated data, generated for any assumed one-dimensional contamination profile, are used to test several methods of profile reconstruction. The methods applied to solve this inverse problem include: linear (Tikhonov) regularization with and without positivity constraints, Backus-Gilbert smoothing, maximum-entropy Bayesian optimization, and a new Bayesian approach that accepts prior information in the form of a multivariate lognormal probability density. A tutorial on inverse theory is provided to relate the seemingly disparate approaches of Bayesian optimization and regularization of a Fredholm integral equation. Particular attention is given to using Shannon-Jaynes configurational entropy as a prior constraint. In the Bayesian context, all methods seek the maximum-a-posteriori (MAP) solution lying at the mode of Bayes' posterior. Comparative inverse MAP solutions are presented for bilinear and step concentration profiles. Maximum-entropy and lognormal-prior methods, which enforce positivity and accept additional prior information, successfully locate bulk concentrations with reasonable peak estimates and minimum computation. Practical depth resolutions are limited to a range of 60 cm in nominal soil by poor neutron penetration. The variance of Bayes' posterior probability distribution is investigated to assess the utility of the MAP concentration profile inferred from a single gamma-ray spectrum. Relative-a-posteriori (RAP) probability contours are sampled to illustrate the range of alternative solutions. Then, maximum-entropy profiles from several RAP contours are used to predict the range of individual MAP solutions that would be computed for replicate data sets. This new method of exploratory variance analysis is referred to as maximum-entropy-relative-a-posteriori (MERAP) analysis. Example problems emphasize proof-of-principle demonstrations rather than development of optimized, robust algorithms.

Letellier, Bruce Clark

1998-11-01

161

Interlaboratory verification of neutron spectra used for the testing of electronic parts  

SciTech Connect

A methodology has been developed for verifying that a neutron energy spectrum measured for an environment correctly predicts the bulk displacement damage that would be observed in a silicon electronic device. The technique makes use of a package of silicon bipolar transistors (2N2222A), monitor activation foils (such as sulfur pellets), and thermoluminescence detectors (TLDs) that is placed in the test environment. The TLDs and monitors are then used to correct for the gamma-induced damage and to scale the reactor power in the test irradiation to that predicted by the neutron spectrum which is being verified. The damage predicted from the spectrum and the measured damage are then compared. In cases where the sensor set does not have sufficient sensitivity coverage to satisfactorily define the spectrum, the transistors can be used as spectrum sensors to provide sensitivity in the crucial energy region between 0.1 and 2.0 MeV. This results in the loss of the independent verification, but leads in a much higher fidelity spectrum. The technique greatly facilitates inter- and intralaboratory comparisons of effects testing and spectrum determinations.

Kelly, J.G.; Griffin, P.J. [Sandia National Labs., Albuquerque, NM (United States); Raupach, D.C.; Daubenspect, T.H. [Pennsylvania State Univ., University Park, PA (United States). Radiation Science and Engineering Center; Bennion, J.S. [Utah Univ., Salt Lake City, UT (United States). Dept. of Mechanical Engineering; Newell, D.L. [Nuclear Radiation Center, McClellan AFB, CA (United States)

1992-12-31

162

Measurement of delayed neutron yields and time spectra from 1 GeV protons interacting with thick nat Pb targets  

Microsoft Academic Search

.In this paper we present for the first time the measured delayed neutron (DN) yields and time spectra from high-energy protons\\u000a interacting with thick natPb targets. The 1GeV protons from the accelerator impinged on targets of different thicknesses producing a huge number of\\u000a spallation-fission products, some of which can be DN precursors. After the beam is switched off, the DNs

D. Ridikas; A. Barzakh; V. Blideanu; J. C. David; D. Dor; D. Fedorov; X. Ledoux; F. Moroz; V. Panteleev; R. Plukiene; A. Plukis; A. Prvost; O. Shcherbakov; A. Vorobyev

2007-01-01

163

Neutron Activation Analysis of Wolframites and Copper-Molybdenium Concentrates by Means of Epithermal Neutrons.  

National Technical Information Service (NTIS)

The results on instrumental neutron activation analysis of copper-molybdenum concentrates and wolframites by means of epithermal neutrons from IBR-30 reactor are presented. This method permitted to determine concentration of Ta and Sc on the level of 10 e...

N. A. Gundorin V. M. Nazarov B. Otgooloj

1981-01-01

164

Neutron activation diagnostics at the National Ignition Facility (invited)  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

165

Evaluation of a commercial 3He semiconductor spectrometer for measurement of external reactor neutron spectra  

NASA Astrophysics Data System (ADS)

The neutron spectrum outside a reactor beam port has been measured by using a 3He semiconductor neutron spectrometer. Only neutrons between 2 and 10 MeV can be obtained. The spectrum falls off exponentially above 6 MeV. Some characteristics, such as bias voltage versus pulse height, low signal-to-noise ratio, counting efficiency versus 3He pressure and radiation damage, have been reported. Energy calibration can be made with thermal neutrons by the characteristic peaks of 0.573 MeV protons and 0.764 MeV Q-value instead of monoenergetic neutrons from a Van de Graaff accelerator.

Yang, Teh-Li; Lin, Tieh Show

1974-12-01

166

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

167

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

168

Nondestructive neutron activation analysis of some soil clays of Egypt  

Microsoft Academic Search

Fourteen clay samples separated from calcareous, lacustrine, Nile alluvium and desert alluvium soils of Egypt were analyzed by pure instrumental neutron activation analysis. Elemental composition was determined by high resolution gamma-spectrometry on samples irradiated with reactor neutrons using the monostrandard technique. This was carried out in the nuclear research center of Karlsruhe, West Germany. As many as 17 trace elements,

R. Zaghloul; S. El-Demerdashe; M. A. Abdel-Salam; E. A. Bakhoum

1987-01-01

169

Neutron detectors for active interrogation of highly enriched uranium  

Microsoft Academic Search

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

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

2004-01-01

170

Infrared Spectra and Hydrogen Bonds of Biologically Active Benzaldehydes  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

171

Raman optical activity spectra of chiral transition metal complexes  

NASA Astrophysics Data System (ADS)

We present calculated vibrational Raman optical activity (ROA) spectra for the transition metal complexes ?-tris(acetylacetonato)cobalt(III), ?-tris(acetylacetonato)rhodium(III), dichloro-(6 R,7 S,9 S,11 S-(-)-sparteine)zinc(II) and ?( ???)-tris(ethylenediaminato)cobalt(III). For this study, it was necessary to benefit from density-fitting techniques to a large extent. Necessary implementations are described and the gauge origin problem is addressed. The importance of the electric-dipole-electric-quadrupole polarizability tensor for ROA intensity differences is investigated and found to be small, especially at lower wavenumbers where no C-H stretching vibrations occur. Furthermore, the basis set and density functional dependence is examined.

Luber, Sandra; Reiher, Markus

2008-05-01

172

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

173

Study of the accumulation of air pollution by the biological indicators, using 14 MeV neutron activation  

Microsoft Academic Search

14 MeV neutron activation analysis was used to determine air polluting elements in samples of mosses, lichens and tree barks, collected from different regions in Morocco. The analysis of spectra shows clearly that the elements Mg, Al, Si, Cl, J, Ca, Ti and Fe can easily be determined by 14 NAA with good precision, while results for Zn, Rb, Sr,

A. Senhou; T. El Khoukhi; A. Chouak; R. El Moursili Cherkaoui; A. El Yahiaoui; M. Lferde

2001-01-01

174

Energy spectra, sources, and shielding considerations for neutrons generated by a flattening filter-free Clinac  

SciTech Connect

Neutron production is an unwanted result of high-energy radiation therapy and results in secondary exposure of patients and radiation therapists to radiation. Recent studies have shown that delivering therapy using a standard medical accelerator with the flattening filter removed may reduce neutron fluence by nearly 70% over the course of prostate intensity-modulated radiation therapy (IMRT). In the current study, the {sup 197}Au Bonner sphere technique was used to compare the neutron spectrum produced when the filter is present and when it is absent. In addition, the following was calculated: (1) the neutron-shielding parameters of source strength and ambient dose equivalent (H{sub 0}) and (2) using the Monte Carlo technique, the sources of neutron production in the accelerator head. It was found that the neutron spectrum was nearly constant, regardless of the presence of the flattening filter; however, the total fluence and ambient dose equivalent over the course of prostate IMRT were more than 70% lower when the filter was removed. Similarly, shielding parameters were lower when the filter was removed. Finally, the primary collimator and jaws accounted for the majority of neutron production, both with and without the flattening filter; however, with the flattening filter removed, the upper jaw accounted for much more neutron production relative to when the filter was present. Ultimately, removal of the flattening filter may offer several clinical advantages, including a reduction in the dose from neutrons to the patient and to radiation personnel.

Kry, Stephen F.; Howell, Rebecca M.; Titt, Uwe; Salehpour, Mohammad; Mohan, Radhe; Vassiliev, Oleg N. [Department of Radiation Physics, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030 (United States)

2008-05-15

175

Active neutron multiplicity counting of bulk uranium  

SciTech Connect

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

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

1991-01-01

176

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

177

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

Microsoft Academic Search

The measurement of 0 neutron spectra and yields from deuterons incident on a thick beryllium-metal target using time-of-flight techniques is described. 235U and 238U fission ion chambers were used as neutron detectors to span the neutron-energy range above 0.05 MeV with a time resolution of <= 3 ns. Measurements were made over flight-paths of ~ 2.65 and ~ 3.75 m

James W. Meadows

1993-01-01

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=13.50.2, 14.10.2, and 14.80.2 MeV are found to be 1.300.08, 1.150.08 and 0.990.07 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

Energy spectra, sources, and shielding considerations for neutrons generated by a flattening filter-free Clinac  

Microsoft Academic Search

Neutron production is an unwanted result of high-energy radiation therapy and results in secondary exposure of patients and radiation therapists to radiation. Recent studies have shown that delivering therapy using a standard medical accelerator with the flattening filter removed may reduce neutron fluence by nearly 70% over the course of prostate intensity-modulated radiation therapy (IMRT). In the current study, the

Stephen F. Kry; Rebecca M. Howell; Uwe Titt; Mohammad Salehpour; Radhe Mohan; Oleg N. Vassiliev

2008-01-01

180

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

181

Mechanistic Analysis of Loft Pulsed Neutron Activation Data.  

National Technical Information Service (NTIS)

Pulsed Neutron Activation (PNA) is a technique for measuring mass-weighted flow velocities without perturbing the flow. Monte Carlo PNA tagging and Monte Carlo detection calculations of the irradiated fluid with the transport of the irradiated fluid are u...

M. L. Perez-Griffo R. C. Block R. T. Lahey

1981-01-01

182

Practical aspects of operating a neutron activation analysis laboratory.  

National Technical Information Service (NTIS)

This book is intended to advise in everyday practical problems related to operating a neutron activation analysis (NAA) laboratory. It gives answers to questions like ''what to use NAA for'', ''how to find relevant research problems'', ''how to find users...

1990-01-01

183

Microcomputer-Based Pneumatic Controller for Neutron Activation Analysis.  

National Technical Information Service (NTIS)

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 Re...

J. S. Byrd R. J. Sand

1976-01-01

184

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

National Technical Information Service (NTIS)

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

M. Pelliccioni A. Zanini

1988-01-01

185

Vibrational spectra and antimicrobial activity of selected bivalent cation benzoates  

NASA Astrophysics Data System (ADS)

Selected bands of FT-IR spectra of Mg(II), Ca(II), Cu(II) and Zn(II) benzoates of both solid state and water solution, were assigned to appropriate molecular vibrations. Next evaluation of electronic charge distribution in both carboxylic anion and aromatic ring of studied compounds was performed. Classical plate tests and turbidimetry measurements, monitoring growth of bacteria Escherichia coli, Bacillus subtilis and yeasts Pichia anomala and Saccharomyces cerevisiae during 24 h of incubation, in optimal growth conditions (control) and in medium with addition of studied benzoate (concentration of 0.01% expressed as the concentration of benzoic acid), proved antimicrobial activity of studied compounds against investigated micro-organisms. PLS (partially least square) and PCR (principal component regression) techniques were applied to build a model, correlating spectral data reflecting molecular structure of studied compounds, with degree of influence of those compounds on growth of studied micro-organisms. Statistically significant correlation within cross validation diagnostic of PLS-1 calibration was found, when log 1/T of selected spectral regions of water solution samples were used as input data. The correlation coefficients between predicted with PLS calibration based on created 1, 2 or 3 factor models, and actual values of antimicrobial activity were: 0.70; 0.76, 0.81 for P. anomala, B. subtilis, and E. coli, respectively. Log(PRESS) values of appropriate models were 2.10, 2,39 and 3.23 for P. anomala, B. subtilis, and E. coli, respectively.

Borawska, M. H.; Koczo?, P.; Piekut, J.; ?wis?ocka, R.; Lewandowski, W.

2009-02-01

186

Design considerations for neutron activation and neutron source strength monitors for ITER  

SciTech Connect

The International Thermonuclear Experimental Reactor will require highly accurate measurements of fusion power production in time, space, and energy. Spectrometers in the neutron camera could do it all, but experience has taught us that multiple methods with redundancy and complementary uncertainties are needed. Previously, conceptual designs have been presented for time-integrated neutron activation and time-dependent neutron source strength monitors, both of which will be important parts of the integrated suite of neutron diagnostics for this purpose. The primary goals of the neutron activation system are: to maintain a robust relative measure of fusion energy production with stability and wide dynamic range; to enable an accurate absolute calibration of fusion power using neutronic techniques as successfully demonstrated on JET and TFTR; and to provide a flexible system for materials testing. The greatest difficulty is that the irradiation locations need to be close to plasma with a wide field of view. The routing of the pneumatic system is difficult because of minimum radius of curvature requirements and because of the careful need for containment of the tritium and activated air. The neutron source strength system needs to provide real-time source strength vs. time with {approximately}1 ms resolution and wide dynamic range in a robust and reliable manner with the capability to be absolutely calibrated by in-situ neutron sources as done on TFTR, JT-60U, and JET. In this paper a more detailed look at the expected neutron flux field around ITER is folded into a more complete design of the fission chamber system.

Barnes, C.W. [Los Alamos National Lab., NM (United States); Jassby, D.L.; LeMunyan, G.; Roquemore, A.L. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Walker, C. [ITER Joint Central Team, Garching (Germany)

1997-12-31

187

The application of the bubble detector to the measurement of intense neutron fluences and energy spectra  

NASA Astrophysics Data System (ADS)

A novel type of bubble detector is developed which can measure neutron fluences on the order of 10 to the 11th n/sq cm (or a few grays). These detectors use superheated droplets which are much smaller than those in conventional bubble detectors. Preliminary studies involving several types of these microdroplet detectors having different neutron energy thresholds have been performed. The goal is to develop a set of such detectors which can be used as a simple neutron spectrometer needed in connection with TREE applications.

Cousins, T.; Tremblay, K.; Ing, H.

1990-12-01

188

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

191

Delayed Neutron Spectra Decay Group for Fissioning Systems from sup 227 Th Through sup 255 Fm.  

National Technical Information Service (NTIS)

Most applications of delayed neutrons use an approximate temporal group representation of measured aggregate data. Such data have been limited to the few fissioning nuclides that have aggregate measurements, and even these have inadequate or no spectral m...

T. R. England M. C. Brady

1988-01-01

192

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

193

Planetary Geochemistry Using Active Neutron and Gamma Ray Instrumentation  

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

194

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

Microsoft Academic Search

The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures\\u000a of 1050 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the\\u000a study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the

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

2010-01-01

195

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

PubMed

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, combined with the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optic ferroelectric mode. PMID:24836255

Li, C W; Hellman, O; Ma, J; May, A F; Cao, H B; Chen, X; Christianson, A D; Ehlers, G; Singh, D J; Sales, B C; Delaire, O

2014-05-01

196

Phonon Self-Energy and Origin of Anomalous Neutron Scattering Spectra in SnTe and PbTe Thermoelectrics  

NASA Astrophysics Data System (ADS)

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, combined with the proximity to the lattice instability, is the mechanism determining the complex spectrum of the transverse-optic ferroelectric mode.

Li, C. W.; Hellman, O.; Ma, J.; May, A. F.; Cao, H. B.; Chen, X.; Christianson, A. D.; Ehlers, G.; Singh, D. J.; Sales, B. C.; Delaire, O.

2014-05-01

197

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

198

Measurements of DT and DD neutron yields by neutron activation on TFTR  

SciTech Connect

A variety of elemental foils have been activated by neutron fluence from TFTR under conditions with the DT neutron yield per shot ranging from 10{sup 12} to over 10{sup 18}, and with the DT/(DD+DT) neutron ratio varying from 0.5% (from triton burnup) to unity. Linear response over this large dynamic range is obtained by reducing the mass of the foils and increasing the cooling time, all while accepting greatly improved counting statistics. Effects on background gamma-ray lines from foil-capsule-material contaminants, and the resulting lower limits on activation foil mass, have been determined. DT neutron yields from dosimetry standard reactions on aluminum, chromium, iron, nickel, zirconium, and indium are in agreement within the {+-}9% (one-sigma) accuracy of the measurements; also agreeing are yields from silicon foils using the ACTL library cross-section, while the ENDF/B-V library has too low a cross-section. Preliminary results from a variety of other threshold reactions are presented. Use of the {sup 115}In(n.n{prime}) {sup 115m}In reaction (0.42 times as sensitive to DT neutrons as DD neutrons) in conjunction with pure-DT reactions allows a determination of the DT/(DD+DT) ratio in trace tritium or low-power tritium beam experiments.

Barnes, C.W.; Larson, A.R. [Los Alamos National Lab., NM (United States); LeMunyan, G. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Loughlin, M.J. [JET Joint Undertaking, Abingdon (United Kingdom)

1995-03-01

199

RADSAT Benchmarks for Prompt Gamma Neutron Activation Analysis Measurements  

Microsoft Academic Search

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples. High-resolution gamma-ray spectrometers are used in these applications to measure the spectrum of the emitted photon flux,

Kimberly A. Burns; Christopher J. Gesh

2011-01-01

200

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

201

Application of cold-neutron prompt gamma activation analysis at the University of Texas reactor  

Microsoft Academic Search

A cold-neutron prompt gamma activation analysis (PGAA) system is operational at the University of Texas (UT) 1 MW TRIGA research reactor. A 6 m long curved neutron guide followed by an 80 cm long converging (focusing) neutron guide transports cold neutrons from the Texas Cold Neutron Source to the PGAA chamber. The UT-PGAA system will be used to determine hydrogen

B. W. Wehring; K. nl; C. Ros-Martnez

1997-01-01

202

Neutron-capture gamma-ray data for obtaining elemental abundances from planetary spectra.  

SciTech Connect

Determination of elemental abundances is a top scientific priority of most planetary missions. Gamma-ray spectroscopy is an excellent method to determine elemental abundances using gamma rays made by nuclear reactions induced by cosmic-ray particles and by the decay of radioactive nuclides [Re73,Re78]. Many important planetary gamma rays are made by neutron-capture reactions. However, much of the data for the energies and intensities of neutron-capture gamma rays in the existing literature [e.g. Lo81] are poor [RF99,RF00]. With gamma-ray spectrometers having recently returned data from Lunar Prospector and NEAR and soon to be launch to Mars, there is a need for good data for neutron-capture gamma rays.

Reedy, Robert; Frankle, S. C. (Stephanie C.)

2001-01-01

203

MICROSCOPIC DETERMINATION OF BONE PHOSPHORUS BY QUANTITATIVE AUTORADIOGRAPHY OF NEUTRON-ACTIVATED SECTIONS  

PubMed Central

Longitudinal sections of human cortical bone were submitted to thermal neutrons. ?-ray spectra were recorded repeatedly during 15 days following irradiation. They showed that Na24 is predominant as early as 3 hours after activation and that all the ?-emitters have decayed on the 15th day. When the ?-rays have disappeared, ?-rays are still produced by the sections. It was proved by the absorption curve in aluminium that all these ?-rays are issued from the P32 induced in the sections by activation of P31. Therefore autoradiograms registered 15 days after activation reveal the distribution of P32 in the sections. ?-ray spectra and ?-ray absorption curves of neutron activated sections of ivory demonstrated a mineral composition similar to that of bone. Autoradiograms of ivory sections activated for various times were used to establish the relation between the optical density of the autoradiograms and the radioactivity in P32. When the bone autoradiograms are compared with the ivory standards of known radioactivity, the optical densities of single osteons (Haversian systems), can be related to their phosphorus contents. Autoradiograms and microradiograms of the same sections were examined side by side. The least calcified osteons, that contain 80 per cent of the calcium of the fully calcified osteons, also contain about 80 per cent of the phosphorus of the fully mineralized osteons. It is concluded that the Ca:P ratio remains constant while mineralization of bone tissue is being completed.

Vincent, Jacques; Haumont, Stanislas; Roels, Joseph

1965-01-01

204

A bismuth activation counter for high sensitivity pulsed 14 MeV neutrons  

Microsoft Academic Search

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 300neutrons\\/cm2 at 15.2cm (6in.). 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 14MeV neutrons activate

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

2011-01-01

205

Measurement of delayed neutron yields and time spectra from 1 GeV protons interacting with thick natPb targets  

NASA Astrophysics Data System (ADS)

In this paper we present for the first time the measured delayed neutron (DN) yields and time spectra from high-energy protons interacting with thick natPb targets. The 1GeV protons from the accelerator impinged on targets of different thicknesses producing a huge number of spallation-fission products, some of which can be DN precursors. After the beam is switched off, the DNs were detected with optimized 3He counter. The production yields of light DN precursors as 17N and usual fission products as 87Br and 88Br, which dominate the total DN activity, are obtained both for thin and thick targets. These new data are of great interest for the new generation high-power spallation targets based on liquid-metal technologies. Our findings also should help to constrain the physics models within the simulations codes.

Ridikas, D.; Barzakh, A.; Blideanu, V.; David, J. C.; Dor, D.; Fedorov, D.; Ledoux, X.; Moroz, F.; Panteleev, V.; Plukiene, R.; Plukis, A.; Prvost, A.; Shcherbakov, O.; Vorobyev, A.

2007-04-01

206

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

Microsoft Academic Search

The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced

J. Cottam; F. Paerels; M. Mendez

2002-01-01

207

Neutron-Capture Gamma-Ray Data for Obtaining Elemental Abundances from Planetary Spectra  

NASA Astrophysics Data System (ADS)

Newly compiled and evaluated energies and intensities of gamma rays made by the capture of thermal neutrons by elements from H to Zn plus Ge, Sm, and Gd are reported for use in determining elemental composition by planetary gamma-ray spectroscopy.

Reedy, R. C.; Frankle, S. C.

2001-03-01

208

Active Neutron Veto Shield Design for SuperCDMS-SNOLAB  

NASA Astrophysics Data System (ADS)

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

Qiu, Hang

2013-04-01

209

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

NASA Astrophysics Data System (ADS)

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, S.

2002-05-01

210

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

SciTech Connect

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

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

2001-01-01

211

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

212

Activation Energy Spectra for Relaxation in Amorphous Materials. I. Volume Relaxation in Polystyrene and Polyvinyl Acetate  

Microsoft Academic Search

A modification of the Primak analysis for activation energy distributions is presented and compared with the well-known analysis for relaxation time distributions. Mathematical and physical interrelationships between the two analyses are discussed. Activation energy spectra are derived from the data of Kovacs for volume relaxation in polystyrene and polyvinyl acetate. The energy spectra are bell shaped and cover the range

R. M. Kimmel; D. R. Uhlmann

1969-01-01

213

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

214

MITOM: a new unfolding code based on a spectra model method applied to neutron spectrometry.  

PubMed

The MITOM code was developed at UAB (Universitat Autnoma de Barcelona) for unfolding neutron spectrometric measurements with a Bonner spheres system (BSS). One of the main characteristics of this code is that an initial parameterisation of the neutron energy components (thermal, intermediate and fast) is needed. This code uses the Monte Carlo method and the Bayesian theorem to obtain a set of solutions achieving different criteria and conditions between calculated and measured count rates. The final solution is an average of the acceptable solutions. The MITOM code was tested for ISO sources and a good agreement was observed between the reference values and the unfolded ones for global magnitudes. The code was applied recently to characterise both thermal SIGMA and CANEL/T400 sources of the IRSN facilities. The results of these applications were very satisfactory as well. PMID:15353706

Toms, M; Fernndez, F; Bakali, M; Muller, H

2004-01-01

215

Neutron spectra produced by a fast pulse assembly in free field and perturbed environments  

NASA Astrophysics Data System (ADS)

The free field radiation environment produced by the White Sands Missile Range Fast Burst Reactor (FBR) was calculated. The primary ranges of interest were for positions 7 meters and 170 meters from the FBR. Calculations were also made for penetrations at ranges of 600 meters and 1000 meters. Neutron spectral shapes were also calculated for a perturbed environment produced by iron and iron + aluminum shielding materials. The radiation transport calculations were performed using the ANISN and DOT 3 discrete ordinates codes. Both codes provide solutions to the Boltzmann transport equation by the discrete ordinates method. The DOT 3 two dimensional code required the use of the GRTUNCL auxiliary code to provide a first-collision source. The use of a first-collision source minimizes the ray effect which is associated with 2 dimensional geometry. The calculated spectral shapes, integral fluences, and neutron dose agree well with experimental determinations of the FBR in a free field environment.

Flanders, T. M.

1980-12-01

216

A simplified few-group model for calculation of neutron flux spectra. [SIFAS Code  

Microsoft Academic Search

A fast, efficient perturbation model is developed for generating few-group cross sections and flux spectrum and performing fuel depletion in a light water reactor unit cell configuration. In the thermal energy region, an approximate solution of the thermal neutron spectrum is determined based on the Wigner-Wilkins free-gas hydrogen scattering model. In the epithermal region, a combination of analytical and empirical

Sinclair

1980-01-01

217

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

PubMed

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

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

2001-01-01

218

Cranking study of low lying yrast spectra and deformation systematics in some even-even neutron-deficient 130-136Nd  

NASA Astrophysics Data System (ADS)

In the present work, the results of calculations on various nuclear structure quantities in even-even neutron-deficient 130-136Nd using Cranked Hartree-Fock Bogoliubov (CHFB) technique have been presented. The various nuclear structure quantities that have been calculated in 130-136Nd isotopes are the yrast spectra, subshell occupation probabilities of various valence orbits and intrinsic quadrupole moments. Besides this, a comparative study of the calculated yrast spectra with the available experimental data as well as with the results of calculations obtained by using Variation-After-Projection (VAP) technique on these neutron - deficient 130-136Nd isotopes has also been presented.

Sharma, Arun; Bharti, Arun; Khosa, S. K.

2013-04-01

219

Analysis of neutron spectra and fluxes obtained with cold and thermal moderators at IBR-2 reactor: Experimental and computer-modeling studies  

NASA Astrophysics Data System (ADS)

The results of experimental and computer-modeling investigations of neutron spectra and fluxes obtained with cold and thermal moderators at the IBR-2 reactor (Joint Institute for Nuclear Research (JINR), Dubna) are presented. These studies are for the YuMO small-angle neutron scattering (SANS) spectrometer (IBR-2 beamline 4). The neutron spectra have been measured for two methane cold moderators for the standard configuration of the SANS instrument. The data from both moderators under different conditions of their operation are compared. The ratio of experimentally determined neutron fluxes of cold and thermal moderators is shown at different wavelengths. Monte Carlo simulations have been carried out to determine the spectra for cold-methane and thermal moderators. The results of calculations of the ratio of neutron fluxes of cold and thermal moderators at different wavelengths are demonstrated. In addition, the absorption of neutrons in the air gaps on the way from the moderator to the investigated sample is presented. SANS with the protein apoferritin was done with both cold methane and a thermal moderator and the data were compared. The prospects for the use of a cold moderator for a SANS spectrometer at IBR-2 are discussed. The advantages of using the YuMO spectrometer with a thermal moderator with respect to the tested cold moderator are shown.

Kuklin, A. I.; Rogov, A. D.; Gorshkova, Yu. E.; Utrobin, P. K.; Kovalev, Yu. S.; Rogachev, A. V.; Ivankov, O. I.; Kutuzov, S. A.; Soloviov, D. V.; Gordeliy, V. I.

2011-03-01

220

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

NASA Astrophysics Data System (ADS)

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

Chilian, Cornelia

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

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

Microsoft Academic Search

The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. ²³⁵U and ²³⁸U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV

Meadows

1991-01-01

223

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

Microsoft Academic Search

The measurement of the zero deg. neutron spectra and yields from deuterons incident on thick beryllium metal targets is described. ²³⁵U and ²³⁸U fission ion chambers were used as neutron detectors to span the neutron energy range above 0.05-MeV with a time resolution of 3 nanosec. Measurements were made for incident deuteron energies from 2.6 to 7.0-MeV, at 0.4-MeV

Meadows

1991-01-01

224

Absorption, excitation and fluorescence spectra of thallium activated cesium bromide  

Microsoft Academic Search

Absorption, excitation and fluorescence spectra of T1+ doped cesium bromide have been investigated at various thallium concentrations. At very low thallium concentration two absorption\\u000a bands are obtained at 225 nm and 264 nm. With rise of thallium concentration additional absorption bands are obtained at 230,\\u000a 244, 258, 270 and 285 nm. A single bell-shaped fluorescence band at 357 nm in

V B Sharan; D N S Srivastwa; S C Sen

1979-01-01

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

An ``exact`` treatment of self-shielding and covers in neutron spectra determinations  

SciTech Connect

Most neutron spectrum determination methodologies ignore self-shielding effects in dosimetry foils and treat covers with an exponential attenuation model. This work provides a quantitative analysis of the approximations in this approach. It also provides a methodology for improving the fidelity of the treatment of the dosimetry sensor response to a level consistent with the user`s spectrum characterization approach. A library of correction functions for the energy-dependent sensor response has been compiled that addresses dosimetry foils/configurations in use at the Sandia National Laboratories Radiation Metrology Laboratory.

Griffin, P.J.; Kelly, J.G.

1995-06-01

227

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

2011-11-01

228

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

229

Instrumental neutron activation analysis for bromine in pig tissues  

Microsoft Academic Search

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

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

1973-01-01

230

Determination of rhenium in molybdenite by neutron-activation analysis.  

PubMed

A neutron-activation method is described for the determination of rhenium in molybdenite. Radiochemical separation by a carrier technique was carried out very rapidly by means of successive liquid-liquid extraction processes. The recovery of rhenium, which was determined by a spectrophotometric method, was about 93%. About 10 samples could be analysed within 6 hr in parallel runs. PMID:18960067

Terada, K; Yoshimura, Y; Osaki, S; Kiba, T

1967-01-01

231

Neutron and gamma-Ray Spectroscopy and Activation Analysis.  

National Technical Information Service (NTIS)

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

N. C. Rasmussen T. J. Thompson

1966-01-01

232

Background and Source Term Identification in Active Neutron Interrogation Methods.  

National Technical Information Service (NTIS)

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

D. A. Anthony

2011-01-01

233

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 70C under atmospheric pressure. The samples

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

1991-01-01

234

NEUTRON-ACTIVATION STUDY OF GALLIUM ARSENIDE CONTAMINATION BY QUARTZ  

Microsoft Academic Search

Gallium arsenide crystals were synthesized by the horizontal Bridgman ; method in neutron-activated boats of natural and synthetic fused quartz. ; lnstrumental radiochemical techniques were applied to determine the silicon ; concentrations from Si³¹ radioactivity measurements and to identify other ; trace elements transferred to the gallium arsenide during the process. All ; crystals were found completely enveloped in an

Werner Kern

1962-01-01

235

A simplified few-group model for calculation of neutron flux spectra. [SIFAS Code  

SciTech Connect

A fast, efficient perturbation model is developed for generating few-group cross sections and flux spectrum and performing fuel depletion in a light water reactor unit cell configuration. In the thermal energy region, an approximate solution of the thermal neutron spectrum is determined based on the Wigner-Wilkins free-gas hydrogen scattering model. In the epithermal region, a combination of analytical and empirical techniques is used to determine resonance cross sections; group flux ratios and neutron leakage are determined by a three-group formulation of the B/sub 1/ equations. These models are combined in a perturbation scheme and incorporated as the SIFAS code. Unit cell depletion studies can be performed at a cost of less than 0.1 seconds per depletion step of The University of Michigan Amdahl 470V/7 computer, using a cross section library containing less than 500 words of information. Perturbations in lattice configuration, hydrogen/fuel atom ratio, and moderator temperature during fuel burnup can all be considered in the SIFAS code. Estimates of core reactivity obtained by the SIFAS code are generally within 0.2% of those determined by codes requiring large fine-group cross section libraries and computational time greater by at least an order of magnitude. Reaction rates of important nuclides in reactor cores can be estimated by the SIFAS code to better than 0.5% for fuel depletion studies for fuel burnup of up to 30,000 MWD/MTM.

Sinclair, A.N.

1980-01-01

236

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

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

237

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

SciTech Connect

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

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

1984-05-01

238

The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars  

NASA Astrophysics Data System (ADS)

Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by the magnetic field strength and topology at birth. Here, using state-of-the-art calculations of the coupled magnetic and thermal evolution of NSs, we compute the thermal spectra and pulse profiles expected for a variety of initial magnetic field configurations. In particular, we contrast models with purely poloidal magnetic fields to models dominated by a strong internal toroidal component. We find that, while the former displays double-peaked profiles and very low pulsed fractions, in the latter, the anisotropy in the surface temperature produced by the toroidal field often results in a single pulse profile, with pulsed fractions that can exceed the 50-60 per cent level even for perfectly isotropic local emission. We further use our theoretical results to generate simulated `observed' spectra, and show that blackbody (BB) fits result in inferred radii that can be significantly smaller than the actual NS radius, even as low as 1-2 km for old NSs with strong internal toroidal fields and a high absorption column density along their line of sight. We compute the size of the inferred BB radius for a few representative magnetic field configurations, NS ages and magnitudes of the column density. Our theoretical results are of direct relevance to the interpretation of X-ray observations of isolated NSs, as well as to the constraints on the equation of state of dense matter through radius measurements.

Perna, Rosalba; Vigan, Daniele; Pons, Jos A.; Rea, Nanda

2013-09-01

239

Calculation of thermal neutron self-shielding correction factors for aqueous bulk sample prompt gamma neutron activation analysis using the MCNP code  

Microsoft Academic Search

In this work thermal neutron self-shielding in aqueous bulk samples containing neutron absorbing materials is studied using bulk sample prompt gamma neutron activation analysis (BSPGNAA) with the MCNP code. The code was used to perform three dimensional simulations of a neutron source, neutron detector and sample of various material compositions. The MCNP model was validated against experimental measurements of the

M. N. Nasrabadi; M. Jalali; A. Mohammadi

2007-01-01

240

A time-of-flight facility for the measurement of electron-induced neutron spectra  

NASA Astrophysics Data System (ADS)

A time-of-flight facility is constructed to investigate photoneutrons in the energy range 5 MeV ? En ? 200 MeV. Photoneutrons are detected simultaneously at four angles (40.2, 90, 113.5, 142.2). The overall time resolution varies from 0.282 ns/m to 0.358 ns/m, depending on the different flight paths (18.56 m to 11.40 m). As a first check the facility is used to measure the ratio of the number of virtual photons to real photons via the photodisintegration of 2H. The measured values agree with the calculated photon spectra.

Schier, Helge; Schoch, Berthold

1974-09-01

241

Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics  

NASA Astrophysics Data System (ADS)

We present a quantum methodology for the calculation of the inelastic neutron scattering (INS) spectra of an H2 molecule confined in a nanoscale cavity. Our approach incorporates the coupled five-dimensional translation-rotation (TR) energy levels and wave functions of the guest molecule. The computed INS spectra are highly realistic and reflect in full the complexity of the coupled TR dynamics on the anisotropic potential energy surfaces of the confining environment. Utilizing this methodology, we simulate the INS spectra of p- and o-H2 in the small cage of the structure II clathrate hydrate and compare them with the experimental data.

Xu, Minzhong; Ulivi, Lorenzo; Celli, Milva; Colognesi, Daniele; Ba?i?, Zlatko

2011-06-01

242

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

243

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

244

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

245

Active Galactic Nuclei and Starved Cosmic Ray Spectra  

NASA Astrophysics Data System (ADS)

It is essential to understand the cosmic ray physics in terms of shock acceleration in relativistic astrophysical environments. One well known astrophysical application is the known process of 'Comptonization' in the disks of accreting compact objects. Since radiation spectra evolve by the Compton scattering of a number of subthermal photons in a hot gas of finite optical depth, we wish to draw here an analogy to cosmic ray spectra, by applying numerical solutions with an application to recently observed AGN jet-conical shocks. We show that the acquired maximum energy allowed by an one-shot low energy injection of particles in a relativistic oblique shock, followed by a second oblique relativistic shock acceleration phase, is a straightforward mechanism in achieving efficiently high values in terms of cosmic ray flux and energy. With this approach we show that the first conical shock establishes a power-law spectrum and the second one pushes the spectrum up to very high energies, consequently leaving a deficiency at low ones.

Meli, A.; Biermann, P. L.

246

BNL Activities in Advanced Neutron Source Development: Past and Present  

SciTech Connect

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

Hastings, J.B.; Ludewig, H.; Montanez, P.; Todosow, M.; Smith, G.C.; Larese, J.Z.

1998-06-14

247

BNL ACTIVITIES IN ADVANCED NEUTRON SOURCE DEVELOPMENT: PAST AND PRESENT  

SciTech Connect

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

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

1998-06-14

248

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

SciTech Connect

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

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

2013-06-15

249

Determination of trace impurities in platinum by neutron activation analysis  

Microsoft Academic Search

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

H. Maleszewska; R. Dybczy?ski

1976-01-01

250

Neutron activation system using water flow for ITER  

NASA Astrophysics Data System (ADS)

A neutron activation system with flowing water using the 16O(n,p)16N reaction has been designed for the International Thermonuclear Experimental Reaction (ITER) neutron yield monitor with temporal resolution, based on the experimental results carried out at the fusion neutronics source (FNS) facility of the Japan Atomic Energy Research Institute. On ITER, irradiation ends will be installed in the filler shielding module between the blanket modules at the equatorial ports. The gamma-ray counting stations will be installed on the upstairs of the pit outside the biological shield. BGO (Bi4Ge3O12) scintillation detectors will be employed to measure 6.13 MeV gamma rays emitted from 16N. The distance between the irradiation end and the counting station is ~20 m. The performance of the neutron activation system has been evaluated by using the neutron Monte Carlo code MCNP-4b with the JENDL 3.2 library. The reaction rate of 16O(n,p)16N was calculated not only at the irradiation end but also along the transfer line, which showed that the temporal resolution would be less than the ITER requirement of 100 ms including turbulent diffusion effects for the flow velocity of 10 m/s. With a flow velocity of 10 m/s, this system can measure the fusion power from 50 kW to 1 GW of the ITER operation by using two gamma-ray detectors; one detector faces the water pipe directly, and another has a collimator for higher-neutron yield. Also the calculation shows that the reaction rate is relatively insensitive to the change of the plasma position.

Nishitani, T.; Ebisawa, K.; Kasai, S.; Walker, C.

2003-03-01

251

Rigorous quantum treatment of inelastic neutron scattering spectra of a heteronuclear diatomic molecule in a nanocavity: HD in the small cage of structure II clathrate hydrate  

NASA Astrophysics Data System (ADS)

We present a novel methodology which allows rigorous quantum calculation of the inelastic neutron scattering (INS) spectra of a heteronuclear diatomic molecule confined inside a nanoscale cavity of an arbitrary shape. This generalizes the approach recently developed by us for the quantum simulation of the INS spectra of nanoconfined homonuclear diatomics. The key distinguishing feature of our approach is the use of the fully coupled 5D translation-rotation (TR) energy levels and wave functions as the initial and final states of the INS transitions. The computed INS spectra embody the full complexity of the quantum TR dynamics of the guest heteronuclear molecule in the anisotropic confinement and are therefore highly realistic. Utilizing this methodology, we compute at several temperatures the INS spectra of HD molecule in the small cage of the structure II clathrate hydrate, which are in very good overall agreement with the experimental INS spectra.

Xu, Minzhong; Ulivi, Lorenzo; Celli, Milva; Colognesi, Daniele; Ba?i?, Zlatko

2013-03-01

252

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

253

Measurement of action spectra of light-activated processes.  

PubMed

We report on a new experimental technique suitable for measurement of light-activated processes, such as fluorophore transport. The usefulness of this technique is derived from its capacity to decouple the imaging and activation processes, allowing fluorescent imaging of fluorophore transport at a convenient activation wavelength. We demonstrate the efficiency of this new technique in determination of the action spectrum of the light mediated transport of rhodamine 123 into the parasitic protozoan Giardia duodenalis. PMID:16526885

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

2006-01-01

254

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

NASA Astrophysics Data System (ADS)

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

Vaknin, David; Demmel, Franz

2014-05-01

255

A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M.

2011-02-01

256

A Study of Venus Surface Elemental Composition From 14-MeV Neutron Induced Gamma Ray Spectroscopy: Activation Analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined by using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M. L.

2010-12-01

257

A bismuth activation counter for high sensitivity pulsed 14 MeV neutrons  

Microsoft Academic Search

We have built a fast neutron bismuth activation counter that measures activation counts from pulsed 14-MeV neutron generators for incident neutron fluences between 30 and 300 neutrons\\/cm2 at 15.2 cm (6 in.). The activation counter consists of a large bismuth germanate (BGO) detector surrounded by a bismuth metal shield in front of and concentric with the cylindrical detector housing. The

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

2011-01-01

258

DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORYS ACTIVE NEUTRON INTERROGATION TEST FACILITY  

Microsoft Academic Search

A new research and development laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for DT fusion (14.1 MeV) neutron generators (2 x 108 neutrons per second), DD fusion (2.5 MeV) neutron generators (up to 2 x 106 neutrons per second), and 252Cf spontaneous fission

D. L. Chichester; E. H. Seabury; J. M. Zabriskie; J. Wharton; A. J. Caffrey

2009-01-01

259

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

260

Nondestructive neutron activation analysis of volcanic samples: Hawaii  

SciTech Connect

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

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

1986-01-01

261

Neutron energy and time-of-flight spectra behind the lateral shield of a high energy electron accelerator beam dump. Part II: Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

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 spectra 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, S.; Liu, J. C.; Rokni, S. H.; Taniguchi, S.

2003-05-01

262

BARYON LOADING OF ACTIVE GALACTIC NUCLEUS JETS MEDIATED BY NEUTRONS  

SciTech Connect

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

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

2012-08-01

263

Design of active-neutron fuel rod scanner  

NASA Astrophysics Data System (ADS)

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

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

1996-02-01

264

High-resolution scintillation spectrometers for neutron-activation analysis  

Microsoft Academic Search

The non-destructive assay of materials through neutron-activation analysis requires the use of gamma-ray detectors which are both sensitive up to ?11MeV and able to provide an adequate spectral-resolution to identify the range of materials of interest to the user. However, in many such applications, it is not practical to use a cooled HPGe spectrometer and in a number of currently

Matthew Dallimore; Grant Crossingham; David Ramsden

2003-01-01

265

Characterization of human dental enamel by epithermal neutron activation analysis.  

PubMed

Dental enamel is considered to be a biological interface depending on two phenomena the surroundings and the individual's general metabolism. The analysis of its chemical composition is becoming more and more developed. A neutron activation method has been elaborated and applied to these analyses. The results obtained and their statistical interpretation emphasize the fundamental importance of trace elements as a result of their role in the main physiopathological phenomenon peculiar to dental enamel. PMID:2535326

Vernois, V; Deschamps, N; Revel, G

1989-06-01

266

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

267

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

Microsoft Academic Search

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements\\u000a in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators\\u000a are available: D-D with 2.5 MeV and D-T with 14.2 MeV neutrons. To compare the performance of these two units in our present\\u000a PGNA system, we performed

R. J. Shypailo; K. J. Ellis

2008-01-01

268

Calculations of neutron activation response for the Tokamak Fusion Test Reactor and absolute calibrations of neutron yield  

SciTech Connect

The most accurate determination of neutron yields from fusion reactors may be obtained from neutron activation measurements of elemental foils. On the Tokamak Fusion Test Reactor (TFTR), a re-entrant irradiation end has been installed to provide a low-scattering environment close to the plasma for neutron activation measurements. The ratio of energy-dependent fluence to total fusion yield is calculated using a fully three-dimensional Monte Carlo calculation with the Monte Carlo code for neutron and photon transport (MCNP). Corrections to the `virgin` fluence from attenuation and scattering are only 10 to 20% for deuterium-tritium (D-T) reactions and 30 to 40% for deuterium-deuterium reactions. A total 1-sigma accuracy of {+-}8% is achieved for D-T neutron yields over a wide dynamic range. This paper documents the response coefficients (hits per source neutron, where hits are activated nuclei per target nuclei) for use by the neutron activation system on TFTR; describes the possible systematic corrections needed (such as major radial variations or the impact of ion temperature on reactions with high-energy thresholds); and estimates uncertainties in the response coefficients. Results from in situ use of a D-T neutron generator are also analyzed using the MCNP modeling as an approximate benchmarking experiment; only 20% accuracy in the comparison is possible because of poor counting statistics in the calibration experiment. 21 refs., 9 figs., 3 tabs.

Barnes, C.W.; Larson, A.R. [Los Alamos National Lab., NM (United States); Roquemore, A.L. [Princeton Plasma Physics Lab., NJ (United States)

1996-09-01

269

Prediction of Biological Activity Spectra via The Internet  

Microsoft Academic Search

The majority of biologically active compounds have both pharmacotherapeutic and side\\/toxic actions. To estimate general efficacy and safety of the molecules under study, their biological potential should be thoroughly evaluated. In an early stage of study, only information about structural formulae was available and was used as an input for computational prediction. Based on a structural formulae of compounds presented

A. Sadym; A. Lagunin; D. Filimonov; V. Poroikov

2003-01-01

270

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

Microsoft Academic Search

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

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

2003-01-01

271

Provenience studies using neutron activation analysis: the role of standardization  

SciTech Connect

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

Harbottle, G

1980-01-01

272

Design and construction of a facility for neutron activation analysis using the 14 MeV neutron generator at HMS Sultan  

Microsoft Academic Search

The potential for using a small, sealed tube, DT neutron generator for neutron activation analysis has been well documented\\u000a but not well demonstrated, except for 14 MeV activation analysis. This paper describes the design, construction and characterization\\u000a of a neutron irradiation facility incorporating a small sealed tube DT neutron generator producing 14 MeV neutrons with fluence\\u000a rates of 2108 s?1

S. E. Jarman; J. Pinchin; J. M. Brushwood; T. McCarthy; M. Bray; P. A. Beeley

2007-01-01

273

?? coincidence spectrometer for instrumental neutron-activation analysis  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

274

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

NASA Astrophysics Data System (ADS)

Neutron-based inspection techniques are unique in their ability to provide material specific signatures, thus offering very high performance and automatic detection of explosives and other contraband. Thermal neutron capture gamma spectroscopy provides excellent sensitivities to hydrogen, nitrogen, chlorine, and other elements, which are characteristic to most explosives, drugs and other contraband that may be smuggled into the country. Fast neutron gamma production (mostly through inelastic scattering) provides good sensitivity to carbon and oxygen. When necessary, these two types of complementary interactions can be combined to yield a more accurate material determination inside small to medium size containers. Standard pulsed 14 MeV electronic neutron generators offer an efficient way to obtain these two types of interactions. Fast (14 MeV) neutrons are produced during the pulse. After the pulse, only the decaying thermal neutron population exists, and thus pure neutron capture gamma-rays are produced. Unfortunately, during the pulse (which is normally much longer than the neutron thermalization time) the fast neutron interactions are highly "contaminated" by the interactions of thermal neutrons within the object and the nearby gamma-ray detectors. This creates high background and spectral interferences in the common medium resolution detectors, such as NaI, BGO, etc. The use of an appropriate shielding, neutron spectrum tailoring, full spectral feature analysis as well as temporal information ("die-away" time) resulted in significant performance enhancements in detection of explosives, drugs and other contraband in difficult geometries.

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

2003-06-01

275

Estimation of the activity generated by neutron activation in control rods of a BWR.  

PubMed

Control rods are activated by neutron reactions into the reactor. The activation is produced mainly in stainless steel and its impurities. The dose produced by this activity is not important inside the reactor, but it has to be taken into account when the rod is withdrawn from the reactor. Activation reactions produced have been modelled by the MCNP5 code based on the Monte Carlo method. The code gives the number of reactions that can be converted into activity. PMID:19836253

Rdenas, Jos; Gallardo, Sergio; Abarca, Agustn; Juan, Violeta

2010-01-01

276

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

277

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

SciTech Connect

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

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

2006-08-14

278

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

279

A militarily fielded thermal neutron activation sensor for landmine detection  

NASA Astrophysics Data System (ADS)

The Canadian Department of National Defence has developed a teleoperated, vehicle-mounted, multi-sensor system to detect anti-tank landmines on roads and tracks in peacekeeping operations. A key part of the system is a thermal neutron activation (TNA) sensor which is placed above a suspect location to within a 30 cm radius and confirms the presence of explosives via detection of the 10.835 MeV gamma ray associated with thermal neutron capture on 14N. The TNA uses a 100 ?g252Cf neutron source surrounded by four 7.62 cm7.62 cm NaI(Tl) detectors. The system, consisting of the TNA sensor head, including source, detectors and shielding, the high-rate, fast pulse processing electronics and the data processing methodology are described. Results of experiments to characterize detection performance are also described. The experiments have shown that anti-tank mines buried 10 cm or less can be detected in roughly a minute or less, but deeper mines and mines significantly displaced horizontally take considerably longer time. Mines as deep as 30 cm can be detected for long count times (1000 s). Four TNA detectors are now in service with the Canadian Forces as part of the four multi-sensor systems, making it the first militarily fielded TNA sensor and the first militarily fielded confirmation sensor for landmines. The ability to function well in adverse climatic conditions has been demonstrated, both in trials and operations.

Clifford, E. T. H.; McFee, J. E.; Ing, H.; Andrews, H. R.; Tennant, D.; Harper, E.; Faust, A. A.

2007-08-01

280

Coincidence Prompt Gamma-Ray Neutron Activation Analysis  

SciTech Connect

The normal prompt gamma-ray neutron activation analysis for either bulk or small beam samples inherently has a small signal-to-noise (S/N) ratio due primarily to the neutron source being present while the sample signal is being obtained. Coincidence counting offers the possibility of greatly reducing or eliminating the noise generated by the neutron source. The present report presents our results to date on implementing the coincidence counting PGNAA approach. We conclude that coincidence PGNAA yields: (1) a larger signal-to-noise (S/N) ratio, (2) more information (and therefore better accuracy) from essentially the same experiment when sophisticated coincidence electronics are used that can yield singles and coincidences simultaneously, and (3) a reduced (one or two orders of magnitude) signal from essentially the same experiment. In future work we will concentrate on: (1) modifying the existing CEARPGS Monte Carlo code to incorporate coincidence counting, (2) obtaining coincidence schemes for 18 or 20 of the common elements in coal and cement, and (3) optimizing the design of a PGNAA coincidence system for the bulk analysis of coal.

R.P. gandner; C.W. Mayo; W.A. Metwally; W. Zhang; W. Guo; A. Shehata

2002-11-10

281

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

282

A Kinematically Beamed, Low Energy Pulsed Neutron Source for Active Interrogation  

Microsoft Academic Search

We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of SNM (Special Nuclear Materials) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals, (1)

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

2004-01-01

283

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

Microsoft Academic Search

We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of special nuclear materials (SNM) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals: (1)

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

2005-01-01

284

Prompt gamma activation analysis enhanced by a neutron focusing capillary lens  

Microsoft Academic Search

A focusing neutron lens using glass polycapillary fibers has been introduced successfully into a prompt gamma activation analysis (PGAA) instrument placed at the exit of a cold neutron guide. The neutron current density gain of the lens is 80, averaged over the focused beam size of 0.53 mm diameter. PGAA measurements have been made on submillimeter particles of gadolinium and

H. Chen; V. A. Sharov; D. F. R. Mildner; R. G. Downing; R. L. Paul; R. M. Lindstrom; C. J. Zeissler; Q. F. Xiao

1995-01-01

285

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

Microsoft Academic Search

Experiments have been performed at Idaho National Laboratory to study methodology and instrumentation for performing neutron active interrogation die-away analyses for the purpose of detecting shielded fissionable material. Here we report initial work using a portable DT electronic neutron generator with a 3He neutron detector to detect shielded fissionable material including enriched uranium and reactor grade plutonium. Measurements have been

David L. Chichester; Edward H. Seabury

2009-01-01

286

Applicability of a Bonner Sphere Technique for Pulsed Neutron in 120 GeV Proton Facility.  

National Technical Information Service (NTIS)

The data on neutron spectra and intensity behind shielding are important for radiation safety design of high-energy accelerators since neutrons are capable of penetrating thick shielding and activating materials. Corresponding particle transport codes - t...

A. F. Leveling D. J. Boehnlein H. Arakawa N. Shigyo T. Sanami

2008-01-01

287

Vanadium in human serum, as determined by neutron activation analysis  

SciTech Connect

Vanadium concentrations have been measured in the serum of 23 healthy subjects by neutron activation analysis, with post-irradiation chemical separation. The values obtained fall in a fairly narrow range (260-1300 ng/L, mean 670 ng/L), which suggests a physiological role for this element. The authors checked the method by analysis of standard (U.S. National Bureau of Standards) water samples and serum samples supplemented with /sup 48/V, and found excellent agreement with expected results in both cases. They consider the reported results for human serum to be more reliable than those obtained by atomic absorption spectroscopy.

Simonoff, M.; Llabador, Y.; Peers, A.M.; Simonoff, G.N.

1984-10-01

288

Recent developments in in vivo neutron activation analysis facilities.  

PubMed

Two new facilities for in vivo activation analysis of patients have been designed, developed, and constructed at Toronto General Hospital. One of these is for the determination of body calcium for the diagnosis of osteoporosis and other diseases associated with bone loss. The other is for the measurement of total body nitrogen for the determination of protein status. These facilities replace old university facilities and take into account the comfort and management of patients. In addition, in the case of the calcium facility, the precision of the measurements has been improved because of larger detector volume and increased neutron source strength. Both the facilities are now in routine hospital clinical use. PMID:1704745

Krishnan, S S; McNeill, K G; Mernagh, J R; Harrison, J E

1990-01-01

289

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

Microsoft Academic Search

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 10MeV; importantly, it is insensitive to gamma radiation <10MeV 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,

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

2010-01-01

290

Praseodymium activation detector for measuring bursts of 14MeV neutrons  

Microsoft Academic Search

A new, accurate, neutron activation detection scheme for measuring pulsed neutrons has been designed and tested. The detection system is accurate and sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of praesodymium, an element that has a single, naturally

B. T. Meehan; E. C. Hagen; C. L. Ruiz; G. W. Cooper

2009-01-01

291

Praseodymium activation detector for measuring bursts of 14 MeV neutrons  

Microsoft Academic Search

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

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

2010-01-01

292

Responses of total and quiescent cell populations in solid tumors to boron and gadolinium neutron capture reaction using neutrons with two different energy spectra.  

PubMed

In neutron capture therapy, whose effectiveness depends on the tumor distribution of neutron capture compound and the neutron energy distribution, controlling quiescent tumor cells with clonogenic potential is critical for therapeutic gain, as is the case in conventional radio- and chemotherapy. Tumor-bearing mice were continuously given 5-bromo-2'-deoxyuridine (BrdU) to label all proliferating cells. After administration of sodium borocaptate-10B (BSH), dl-p-boronophenylalanine-10B (BPA) or gadodiamide hydrate (Omniscan), the tumors were irradiated with neutrons of different cadmium (Cd) ratio, and then isolated and incubated with cytochalasin-B (a cytokinesis blocker). The micronucleus (MN) frequency in cells without BrdU labeling (quiescent cells) was determined using immunofluorescence staining for BrdU, and that for total cells was obtained from tumors not pretreated with BrdU. Without drugs, quiescent cells showed lower MN frequencies than total cells, but neutron irradiation reduced gamma-ray sensitivity difference between the two. Relative biological effectiveness (RBE) of neutrons compared with gamma-rays was greater in quiescent cells than in total cells, and low Cd ratio neutrons tended to exhibit large RBE values. With neutron capture compounds, MN frequency for each cell population was increased, especially when high Cd ratio neutrons were used. BPA increased the MN frequency for total cells to a greater extent than BSH. However, the sensitivity of quiescent cells treated with BPA was lower than that in BSH-treated quiescent cells. This tendency was clearly observed in high Cd ratio neutrons. Omniscan only slightly increased the MN frequency in both cell populations, compared with irradiation alone, without drugs. From the viewpoint of increasing the quiescent cell sensitivity, tumors should be irradiated with high Cd ratio neutrons after BSH administration. PMID:9510480

Masunaga, S; Ono, K; Sakurai, Y; Suzuki, M; Takagaki, M; Kobayashi, T; Kinashi, Y; Akaboshi, M

1998-01-01

293

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  

Microsoft Academic Search

Second neutron yields, energy spectra, and angular distributions have been measured at seven angles from 0 to 150° for 113 and 256 MeV protons stopped in range-thick targets of aluminum and depleted uranium (²³⁸U). 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

L. R. Greenwood; A. Intasorn

1989-01-01

294

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

Microsoft Academic Search

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

C. Pioch; V. Mares; W. Rhm

2010-01-01

295

Instrumental neutron activation analysis of sectioned hair strands for arsenic  

SciTech Connect

Instrumental neutron activation analysis (INAA) is a valuable and proven method for the quantitative analysis of sectioned human head hair specimens for arsenic - and, if arsenic is found to be present at high concentrations, the approximate times when it was ingested. Reactor-flux thermal-neutron activation of the hair samples produces 26.3-h {sup 76}As, which is then detected by germanium gamma-ray spectrometry, measuring the 559.1-keV gamma-ray peak of {sup 76}As. Even normal levels of arsenic in hair, in the range of <1 ppm up to a few parts per million of arsenic can be measured - and the far higher levels associated with large internal doses of arsenic, levels approaching or exceeding 100 ppm arsenic, are readily and accurately measurable. However, all phases of forensic investigations of possible chronic (or in some cases, acute) arsenic poisoning are important, i.e., not just the analysis phase. All of these phases are discussed in this paper, based on the author`s experience and the experience of others, in criminal cases. Cases of chronic arsenic poisoning often reveal a series of two to four doses, perhaps a few months apart, with increasing doses.

Guinn, V.P. [Univ. of Maryland, College Park, MD (United States)

1996-12-31

296

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...

297

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

National Technical Information Service (NTIS)

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

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

1989-01-01

298

Microstructural origins of radiation-induced changes in mechanical properties of 316 L and 304 L austenitic stainless steels irradiated with mixed spectra of high-energy protons and spallation neutrons  

Microsoft Academic Search

A number of candidate alloys were exposed to a particle flux and spectrum at Los Alamos Neutron Science Center (LANSCE) that closely match the mixed high-energy proton\\/neutron spectra expected in accelerator production of tritium (APT) window and blanket applications. Austenitic stainless steels 316 L and 304 L are two of these candidate alloys possessing attractive strength and corrosion resistance for

B. H Sencer; G. M Bond; M. L Hamilton; F. A Garner; S. A Maloy; W. F Sommer

2001-01-01

299

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

PubMed

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

El-Taher, A

2007-04-01

300

Epithermal Neutron Activation Analysis of the Asian Herbal Plants  

SciTech Connect

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

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

2011-06-28

301

Epithermal Neutron Activation Analysis of the Asian Herbal Plants  

NASA Astrophysics Data System (ADS)

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

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

2011-06-01

302

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

303

Praseodymium activation detector for measuring bursts of 14MeV 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 accurate and sensitive to neutrons with energies above 10 MeV; importantly, it is insensitive to gamma radiation and to lower-energy (e.g., fission and thermal) neutrons. It is based upon the use of praesodymium, an element that has a single, naturally occurring isotope (Pr-141), a significant (n,2n) cross section, and decays by positron emission. Neutron fluences are measured by using the sum-peak method to count gamma-ray coincidences from the annihilation of the positron decay product. The system was tested using 14 and 2.45 MeV neutron bursts produced by NSTec Dense Plasma Focus Laboratory fusion sources. Comparisons with lead, copper, beryllium and silver activation detectors have been performed. The detection method allows measurement of 14 MeV neutrons with a total error of +/- 10%.

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

2009-08-01

304

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

305

Calculated proton-induced thick-target neutron and gamma yield spectra for E sub p le 100 MeV  

Microsoft Academic Search

Medium-energy activation and shielding requirements have led to the production of libraries of evaluated nuclear data describing the reactions of charged particles and neutrons with typical accelerator materials. These libraries build mainly on results of calculations with the GNASH preequilibrium statistical nuclear model code as it has evolved during the past few years. One library describes the production of activation

W. B. Wilson; E. D. Arthur; M. Bozoian; R. T. Perry; P. G. Young

1989-01-01

306

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

307

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

308

Neutronic reactor  

DOEpatents

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

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

1983-01-01

309

180Hf energy levels deduced from thermal and average resonance neutron-capture gamma-ray spectra  

Microsoft Academic Search

An energy level diagram for 180Hf is developed on the basis of neutron-capture gamma-ray spectroscopy. Both thermal neutron capture and average resonance neutron-capture studies were made with isotopically enriched and natural Hf samples. The energies and intensities of the high-energy 7.4-4.7 MeV primary gamma transitions and the intermediate-energy 2.1-0.5 MeV gamma transitions were made with the in-pile (n ,gamma) source

D. L. Bushnell; D. J. Buss; Robert K. Smither

1974-01-01

310

MEASUREMENTS OF RADIATIVE CAPTURE CROSS SECTIONS FOR FAST NEUTRONS  

Microsoft Academic Search

Cross-section measurements of radiative capture were made both for ; monoenergetic fast neutrons and for a wide spectra of fast neutrons by means of ; an activation method, as well as by neutron halance in the spherical geometry of ; the experiment, by capture gamma rays, and by reactivity measurements. ; Measurements of capture cross sections for a number of

A. I. Leipunskii; O. D. Kazachkovskii; G. Y. Artyukov

1959-01-01

311

Estimated Neutron-Activation Data for TFTR. Part II. Biological Dose Rate from Sample-Materials Activation.  

National Technical Information Service (NTIS)

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 activa...

L. Ku J. G. Kolibal

1982-01-01

312

Clinical applications of in vivo neutron-activation analysis  

SciTech Connect

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

Cohn, S.H.

1982-01-01

313

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

314

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

Microsoft Academic Search

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

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

315

Vanadium determination in rat tissues and biological reference materials by neutron activation analysis  

Microsoft Academic Search

Vanadium was determined in adrenal gland, brain, ileum, kidney, liver, lung, muscle, myocard, skin, spleen, gonads, thyroid, and tibia of rats fed with normal diet and exposed to high vanadium doses in drinking water. Both radiochemical neutron activation analysis (RNAA) and instrumental neutron activation analysis (INAA) were employed. The RNAA procedure consisted in dry ashing samples prior to irradiation and

J. Ku?era; M. imkov; J. Lener; A. Mravcov; L. Kinova; I. Penev

1990-01-01

316

Experimental and numerical calibration of the neutron activation system on the FTU tokamak  

Microsoft Academic Search

A benchmark experiment has been performed for the absolute calibration of the FTU tokamak neutron activation system with the purpose of comparing experimental and numerical absolute reaction rates. Indium samples have been activated by a 252Cf neutron source located on the torus axis at three different toroidal angles with respect to the irradiation ends. The same experimental arrangements have been

M. Angelone; P. Batistoni; L. Bertalot; B. Esposito; M. Martone; M. Pillon; S. Podda; M. Rapisarda; S. Rollet

1990-01-01

317

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

Microsoft Academic Search

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

A. A. Smales; D. Mapper; K. F. Fouch

1967-01-01

318

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

319

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

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

320

Influence of the Deviation from the Equilibrium Deuteron Distribution on the Neutron Spectra in Linear Pinch Geometries.  

National Technical Information Service (NTIS)

In order to analyse the influence of the deviation from the equilibrium distribution of the fast deuterons on the neutron spectrum, the limiting case, corresponding to a two-dimensional mono-energetic deuteron distribution, was studied. An essential diffe...

R. Deutsch H. Herold H. J. Kaeppeler H. Schmidt

1982-01-01

321

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

322

Comparison of the gamma-ray spectra from 2. 8keV neutron capture and thermal-neutron capture in sodium-23  

Microsoft Academic Search

The gamma-ray spectrum resulting from neutron capture in the 2.8-keV resonance of ²³Na has been measured with the high-resolution annihilation pair spectrometer at the internal-target facility of the CP-5 reactor. The 2.8-keV resonance was populated by using the boron-shielded target technique: A ¹\\/-in.-thick filter of ¹°B surrounding the sodium sample selectively removes low-energy neutrons from the spectrum; the 1\\/E dependence

W. M. Wilson; H. E. Jackson; G. E. Thomas

1977-01-01

323

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

NASA Astrophysics Data System (ADS)

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

Xu, Minzhong; Ba?i?, Zlatko

2011-11-01

324

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

325

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

326

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

327

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

NASA Astrophysics Data System (ADS)

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

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

1995-03-01

328

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

PubMed

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

Guo, Shuntong; Ziemer, Paul L

2004-05-01

329

Optical Spectra of Rare Earth Activated BaTiO3  

Microsoft Academic Search

BaTiO3 has been activated with Pr, Sm, Eu, Dy, or Er ions. The fluorescence spectra were determined at 196C, 28C, room temperature, and at 130C. We looked for crystalline field effects on the energy levels of the rare earths and changes in these effects as the crystallographic phase of BaTiO3 is changed. In particular, we sought changes at the Curie

Seymour P. Keller; George D. Pettit

1959-01-01

330

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

331

Summary of measurements and calculations of neutron and gamma-ray emission spectra from spheres pulsed with 14-MeV neutrons  

NASA Astrophysics Data System (ADS)

A tabulation of the spherical assemblies for which the transport of 14 MeV neutrons have been measured using pulsed sphere and time of flight techniques is presented. The description of the measurements and their comparison with the predictions of Monte Carlo calculations using the ENDL and ENDF (III to V versions) libraries can be found in the publications listed in the references.

Hansen, L. F.; Komoto, T. T.; Pohl, B. A.; Wong, C.

1982-11-01

332

Improvement of calibration assessment for gold fast-neutron activation analysis using plasma focus devices  

Microsoft Academic Search

By exploiting the gamma detector-shielding configuration in a plasma focus (PF) device dedicated to fast-neutron activation analysis of gold, a reliable neutron counter may be established. The decay of 207Pbm induced by neutrons in the lead shielding surrounding the photon detector produces gamma photons of 569.7 and 1063.6 keV, which peaks are registered in the same spectrum containing the 279

A. Tartari; G. Verri; A. Da Re; F. Mezzetti; C. Bonifazzi; L. Rapezzi

2002-01-01

333

Determination of Hydrogen in Niobium by Cold Neutron Prompt Gamma-Ray Activation Analysis and Neutron Incoherent Scattering  

Microsoft Academic Search

The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other

Rick L. Paul; H. Heather Chen-Mayer; Ganapati Rao Myneni

2003-01-01

334

Determination of hydrogen in niobium by cold neutron prompt gamma ray activation analysis and neutron incoherent scattering  

Microsoft Academic Search

The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other

R. L. Paul; H. H. Cheu-Maya; G. R. Myneni

2002-01-01

335

Determination of Hydrogen in Niobium by Cold Neutron Prompt Gamma-Ray Activation Analysis and Neutron Incoherent Scattering  

NASA Astrophysics Data System (ADS)

The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.

Paul, Rick L.; Chen-Mayer, H. Heather; Myneni, Ganapati Rao

2003-07-01

336

Determination of hydrogen in niobium by cold neutron prompt gamma ray activation analysis and neutron incoherent scattering  

SciTech Connect

The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.

R.L. Paul; H.H. Cheu-Maya; G.R. Myneni

2002-11-01

337

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

NASA Astrophysics Data System (ADS)

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

Efimov, A. I.; Lukanina, L. A.; Samoznaev, L. N.; Rudash, V. K.; Chashei, I. V.; Bird, M. K.; Ptzold, M.; Tellmann, S.

2010-03-01

338

EChO spectra and stellar activity II. The case of dM stars  

NASA Astrophysics Data System (ADS)

EChO a dedicated mission to investigate exoplanetary atmospheres. When extracting the planetary signal, one has to take care of the variability of the hosting star, which introduces spectral distortion that can be mistaken as planetary signal. Magneticvariability has to be taken into account in particular for M stars. To this purpose, assuming a one spot dominant model for the stellar photosphere, we develop a mixed observational-theoretical tool to extract the spot's parameters from the observed optical spectrum. This method relies on a robust library of spectral M templates, which we derive using the observed spectra of quiet M dwarfs in the SDSS database. Our procedure allows to correct the observed spectra for photospheric activity in most of the analyzed cases, reducing the spectral distortion down to the noise levels. Ongoing refinements of the template library and the algorithm will improve the efficiency of our algorithm.

Scandariato, Gaetano; Micela, Giuseppina

2014-05-01

339

Analysis of neutron emission spectra for 30 50 MeV alpha-particle induced reactions in thick targets  

Microsoft Academic Search

Comparisons of calculated neutron yield distributions from alpha-particle induced reactions on thick targets are made with measured data to analyze the initial reaction process in the framework of the exciton (hybrid) model code ALICE91 (M. Blann, Lawrence Livermore National Laboratory Report UCID 19614, 1982). We have considered two reaction mechanisms: dissolution of the alpha in the nuclear field, and preequilibrium

D. Dhar; S. N. Roy; Maitreyee Nandy; P. K. Sarkar

2003-01-01

340

0-600 kev GAMMA-RAY SPECTRA FROM THERMAL NEUTRON CAPTURE IN THE REGION A = 104 TO 198  

Microsoft Academic Search

The energies and absolute intensities of prominent peaks in the 0-600 ; kev region of the gamma-ray spectrum following thermal neutron capture have been ; measured with a single NaI(T1) scintillation spectrometer. The elements ; investigated were rhodium, silver, cadmium, indium, antimony, tellurium, iodine, ; samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ; hafnium, tantalum, rhenium, iridium, platinum, and

James Draper

1959-01-01

341

0-600 kev Gamma-Ray Spectra from Thermal Neutron Capture in the Region A=104 to 198  

Microsoft Academic Search

The energies and absolute intensities of prominent peaks in the 0-600 kev region of the gamma-ray spectrum following thermal neutron capture have been measured with a single NaI(Tl) scintillation spectrometer. The elements investigated were rhodium, silver, cadmium, indium, antimony, tellurium, iodine, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, hafnium, tantalum, rhenium, iridium, platinum, and gold.

James E. Draper

1959-01-01

342

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.

343

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

SciTech Connect

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

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

1990-03-01

344

Instrumental neutron activation analysis for studying size-fractionated aerosols  

NASA Astrophysics Data System (ADS)

Instrumental neutron activation analysis (INAA) was utilized for studying aerosol samples collected into a coarse and a fine size fraction on Nuclepore polycarbonate membrane filters. As a result of the panoramic INAA, 49 elements were determined in an amount of about 200-400 ?g of particulate matter by two irradiations and four ?-spectrometric measurements. The analytical calculations were performed by the absolute ( k0) standardization method. The calibration procedures, application protocol and the data evaluation process are described and discussed. They make it possible now to analyse a considerable number of samples, with assuring the quality of the results. As a means of demonstrating the system's analytical capabilities, the concentration ranges, median or mean atmospheric concentrations and detection limits are presented for an extensive series of aerosol samples collected within the framework of an urban air pollution study in Budapest. For most elements, the precision of the analysis was found to be beyond the uncertainty represented by the sampling techniques and sample variability.

Salma, Imre; Zempln-Papp, va

1999-10-01

345

Neutron Activation Cool-down of the Tokamak Fusion Test Reactor  

SciTech Connect

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

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

1998-06-10

346

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

NASA Astrophysics Data System (ADS)

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

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

347

Calculation of Al(p,xn) and Cu(p,xn) thick-target neutron angular yields and spectra for E\\/sub p\\/. delta. 50 MeV  

Microsoft Academic Search

Present design effort of shielding for a high-current 50-MeV proton linear accelerator requires the accurate description of the neutron sources produced from proton spills at all energies of copper accelerator fixtures and from 50-MeV proton spills on aluminum beam tubes and carbon beam stops. The recent thick-target neutron spectra measurements for 30- and 52-MeV protons on carbon, iron, copper, and

E. D. Arthur; W. B. Wilson

1985-01-01

348

Thick target neutron yields and spectra from the Li(d,xn) reaction at 35 MeV  

Microsoft Academic Search

Measurements were performed using a 35 MeV deuteron beam from the isochronous cyclotron at the University of California at Davis. Data were obtained using the time-of-flight technique with an NE213 liquid scintillator. One set of measurements was used to observe the neutron spectrum from approx. 1 MeV to approx. 50 MeV, the maximum kinematically allowed energy. Observation angles were from

D. L. Johnson; F. M. Mann; J. W. Watson; F. P. Brady; J. L. Ullmann; J. L. Romero; C. M. Castaneda; C. I. Zanelli; W. G. Wyckoff

1980-01-01

349

Non-Destructive Bulk Soil Analysis for a Chlorinated Compound using Prompt Gamma-Ray Neutron Activation Analysis  

SciTech Connect

A prompt gamma-ray neutron activation analysis (PGNAA) system was evaluated for the quantification of chlorinated compounds in soil. The system evaluation was divided into two phases. In phase one, the response of an n-type HPGe detector (20 percent relative efficiency) to point sources of 60Co and 152Eu was determined experimentally and used to calibrate an MCNP4a model of the detector. The refined MCNP4a detector model can predict the absolute peak detection efficiency within 7 percent in the energy range of 120 - 1400 keV. In phase two, a PGNAA system consisting of a light-water moderated 252Cf (1.06 mg) neutron source, and the shielded and collimated HPGe detector was used to collect prompt gamma-ray spectra from Savannah River Site (SRS) soil spiked with chlorine. The experimental system response was used to calculate the minimum detectable concentration of chlorine in the SRS soil for a 1800 sec. irradiation as 2200 mg/g based on the analysis of the 788 keV gamma-ray. MCNP4a was used to predict the PGNAA system response, which was accomplished by analyzing the neutron and gamma ray transport components separately. In the energy range of 788 to 6110 keV, the MCNP4a predictions were generally within 60 percent of the calculated probability of detection of a prompt gamma ray based on the experimental data.

Sigg, R.A.

1999-04-19

350

Neutron activation analysis at the Livermore pool-type reactor for the environmental research program. [Identification of trace element contaminants  

Microsoft Academic Search

Instrumental neutron activation analysis is a technique of trace analysis using measurements of radioactivity induced in the sample by exposure to a source of neutrons. The induced activity is measured by the emitted gamma radiation. Each gamma emitter can then be identified by the energy of the photopeaks produced as the nuclide decays and by the half-life of the neutron-induced

R. C. Ragaini; R. E. Heft; D. Garvis

1976-01-01

351

Application of the Neutron Activation Analysis Method to the Multielemental Determination of Food Samples.  

National Technical Information Service (NTIS)

The thermal neutron activation analysis method was applied to the determination of elements present at low concentrations and trace levels in samples of bread and milk powder using non-destructive analyses were based on gamma ray spectrometric measurement...

V. A. Maihara

1985-01-01

352

Neutron activation analysis with k(sub 0)-standardisation : general formalism and procedure.  

National Technical Information Service (NTIS)

Instrumental neutron activation analysis (INAA) with k(sub 0)- standardisation is a powerful tool for multi-element analysis at a broad range of trace element concentrations. An overview is given of the basic principles, fundamental equations, and general...

S. Pomme F. Hardeman P. Robouch N. Etxebarria G. Arana

1997-01-01

353

Computer Program to Evaluate the Experimental Data in Instrumental Multielement Neutron Activation Analysis.  

National Technical Information Service (NTIS)

A computer code evaluating experimental data of neutron activation analysis (NAA) for determination of atomic abundancies is described. The experimental data are, beside a probe designation, the probe weight, irradiation parameters and a Ge(Li)-pulse-heig...

L. Greim K. Motamedi R. Niedergesaess

1976-01-01

354

Investigation of Trace Elements in Elbe Water by Means of Instrumental Neutron Activation Analysis.  

National Technical Information Service (NTIS)

Investigations of trace elements in Elbe water were carried out as a contribution to environmental research, hydrology, and geochemistry. The method applied - instrumental neutron activation analysis - is described, and problems connected with the course ...

K. Motamedi

1977-01-01

355

Elemental Analysis of Water and Air Solids by Neutron Activation Analysis.  

National Technical Information Service (NTIS)

Instrumental neutron activation analysis was used to determine the elemental concentrations in water and air solids samples collected on Nucleopore and Whatman filters from the Walker Branch Watershed. The results from this study show that the trace eleme...

L. C. Bate S. E. Lindberg A. W. Andren

1975-01-01

356

Determination of Metallosis after AO Plate Osteosynthesis by Means of Instrumental Neutron Activation Analysis.  

National Technical Information Service (NTIS)

The instrumental neutron activation analysis was used to determine metallosis after osteosynthesis in 11 samples of contact tissues and 6 samples of fascial tissues by means of AO-plates made of stainless steel. The concentrations of the elements specific...

G. Blettenberg

1975-01-01

357

Instrumental Neutron Activation Analysis in the Measurement of Trace Element Distribution at Two Coal Conversion Plants.  

National Technical Information Service (NTIS)

Instrumental neutron activation analysis was used to study the elemental concentration in the complex materials produced by the H-Coal process and the low Btu gasification process at the University of Minnesota at Duluth (UMD). Trace element distribution ...

L. M. Roseberry F. F. Dyer

1984-01-01

358

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

National Technical Information Service (NTIS)

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

E. Pernicka P. Krejsa

1978-01-01

359

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

360

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

361

Rare-earth elemental analysis of banded iron-formations by instrumental neutron activation analysis  

Microsoft Academic Search

Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated\\u000a by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux\\u000a of 5.11016 m?2s?1, 1.01015 m?2s?1 and 3.71015 m?2s?1, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector.\\u000a Ten rare-earth elements,

P. K. Nayak; B. Wierczinski; S. Lahiri

2008-01-01

362

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

SciTech Connect

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

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

2013-07-01

363

NAAPRO: A code for predicting results and performance of neutron activation analysis  

Microsoft Academic Search

SummaryA code is described for predicting the results and main characteristics of neutron activation analysis (NAA) on the basis of a simulated gamma-ray spectrum of activation products, calculated for the specified analysis conditions. These are analysis time mode, analyzed sample mass and elemental composition, characteristics of the irradiating neutron flux and irradiation conditions, gamma-spectrometry measurement geometry and background conditions, as

V. K. Basenko; A. N. Berlizov; I. A. Malyuk; V. V. Tryshyn

2005-01-01

364

Neutron activation analysis of biological samples at the Radiochemistry Division of IPEN-CNEN\\/SP  

Microsoft Academic Search

Neutron activation analysis is a very useful method for determination of a great number of elements in biological samples.\\u000a At the Radiochemistry Division of the IPEN-CNEN\\/SP, this method is being extensively applied to study several materials, such\\u000a as extracts from medicinal plants, human hair, snake venoms, human lungs, foodstuffs, and corn samples. Both instrumental\\u000a neutron activation analysis (INAA) and radiochemical

M. Saiki; M. B. A. Vasconcellos; V. A. Maihara; M. J. A. Armelin; D. I. T. Fvaro; S. O. Rogero

1994-01-01

365

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

366

Gammastrahlenspektrometrische Bestimmung der Aktivittsverhltnisse zwischen Th-228 und seinen Folgeprodukten II. Calculation of the activity ratios from energy- spectra  

Microsoft Academic Search

Summary A mathematical method is described which allows to determine the Ra-224 and Pb-212 activities of tissue samples containing thorotrast at the time of extirpation from results of gammaray-spectrometry by transformation of the measured pulse height spectra into energy spectra. The activities are calculated from the variation with time of the quantum rate within the 0.24 MeV energy interval. Results

J. Heyder; A. Kaul

1968-01-01

367

Importance of backbone angles versus amino acid configurations in peptide vibrational Raman optical activity spectra  

NASA Astrophysics Data System (ADS)

In this work, we investigate whether the differential scattering of right- and left-circularly polarized light in peptide Raman optical activity spectra are uniquely dominated by the backbone conformation, or whether the configurations of the individual amino acid also play a significant role. This is achieved by calculating Raman optical activity spectra using density functional theory for four structurally related peptides with a common backbone conformation, but with different sequences of amino acid configurations. Furthermore, the ROA signals of the amide normal modes are decomposed into contributions from groups of individual atoms. It is found that the amino acid configuration has a considerable influence on the ROA peaks in the amide I, II, and III regions, although the local decomposition reveals that the side-chain atoms only contribute to those peaks directly in the case of the amide II vibrations. Furthermore, small changes in the amide normal modes may lead to large and irregular modifications in the ROA intensity differences, making it difficult to establish transferable ROA intensity differences even for structurally similar vibrations.

Herrmann, Carmen; Ruud, Kenneth; Reiher, Markus

2008-01-01

368

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

SciTech Connect

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

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

1984-01-01

369

Non-destructive neutron-activation analysis for determining the chlorine content of paper-pulp.  

PubMed

Non-destructive neutron-activation analysis is used for determining chlorine in paper-pulp. Numerical data have been obtained for bleached and unbleached paper-pulps of different types and origins. The sensitivity of this method is 100 ppm for an irradiation time of 30 min and a neutron flux of 6 x 10(10) neutrons.cm(-2).sec(-1) and 10 ppm for an irradiation time of 1 min and a neutron flux of 2 x 10(12) neutrons.cm(-2).sec(-1). In both cases the amount of chlorine that can be determined depends on the presence of the interfering elements manganese and sodium in the paper-pulp. The time required for a complete analysis, after irradiation, is 5 min. PMID:18959861

Souliotis, A G; Grimanis, A P; Tsanos, N A

1966-01-01

370

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra  

NASA Astrophysics Data System (ADS)

Context. Shocks in jets and hot spots of active galactic nuclei (AGN) are one prominent class of possible sources of very high-energy cosmic-ray particles (above 1018 eV). Extrapolating their spectrum to their plausible injection energy from some shock implies an enormous hidden energy for a spectrum of index 2. Some analyses suggest the particles' injection spectrum at source to be as steep as 2.4 to 2.7, which exacerbates the problem, by a factor of 106. Nevertheless, it seems implausible that more than at the very best 1/3 of the jet energy goes into the required flux of energetic particles, thus one would need to allow for the possibility that there is an energy problem, which we would like to address in this work. Aims. Sequences of consecutive oblique shock features, or conical shocks, have been theoretically predicted and eventually observed in many AGN jets. Based on that, we use by analogy the Comptonization effect and propose a scenario of a single injection of particles consecutively accelerated by several oblique shocks along the axis of an AGN jet. Methods. We developed a test-particle approximation Monte Carlo simulations to calculate particle spectra by acceleration at such a shock pattern while monitoring the efficiency of acceleration by calculating differential spectra. Results. We find that the first shock of a sequence of oblique shocks establishes a low-energy power-law spectrum with ~E-2.7. The following consecutive shocks push the spectrum up in energy, rendering flatter distributions with steep cut-offs, and characteristic depletion at low energies, which could explain the puzzling apparent extra source power. Conclusions. Our numerical calculations show a variation of spectral indices, a general spectral flattening, and starved spectra, which connect to the relativistic nature of the shocks, the multiple shock acceleration conditions, and the steepness of the magnetic field to the shock normal. This helps in understanding the jet-magnetic field geometry and the irregular or flat spectra observed in many AGN jets (e.g., CenA, 3C 279, PKS 1510-089). Furthermore, the E-2.4 - E-2.7 ultra-high-energy cosmic-ray injected source spectra claimed by many authors might be explained by the superposition of several, perhaps many, emission sources, all of which end their particle shock-acceleration sequence with flatter, starved spectra produced by two or more consecutive oblique shocks along their jets. It might also imply a mixed component of the accelerated particles above 1019 eV. Moreover, the present acceleration model can explain the variability of inverted gamma-ray spectra observed in high redshifted flaring extragalactic sources.

Meli, A.; Biermann, P. L.

2013-08-01

371

One-Dimensional Simulation of the Effects of Unstable Mix on Neutron and Charged Particle Spectra from Laser-Driven Implosion Experiments  

NASA Astrophysics Data System (ADS)

The effects of Rayleigh--Taylor flow in recent laser-driven implosion experiments are simulated in one dimension by the hydrocode LILAC. Mix is modeled as a diffusive transport process affecting material constituents, thermal energy, and turbulent mix-motion energy within a growing mix region whose boundaries are derived from a saturable, linear multimode model of the Rayleigh--Taylor instability. The linear growth rates and the feedthrough coupling between perturbations of different unstable interfaces are obtained analytically in terms of the one- dimensional fluid profiles. Mode evolution proceeds according to equations applicable to all phases of acceleration, and the effects of geometrically converging, compressible flow are taken into account. Simulated mix-diagnostic signals include time-resolved energy spectra of neutrons from core fuel and/or embedded deuterium shell layers and the energy spectra of charged primary and secondary products of nuclear reactions. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460, the University of Rochester, and the New York State Energy Research and Development Authority.

Epstein, R.; Delettrez, J. A.; Goncharov, V. N.; McKenty, P. W.; Radha, P. B.; Skupsky, S.

1999-11-01

372

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

SciTech Connect

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

D. L. Chichester; E. H. Seabury

2008-10-01

373

DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORYS ACTIVE NEUTRON INTERROGATION TEST FACILITY  

SciTech Connect

A new research and development laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for DT fusion (14.1 MeV) neutron generators (2 x 108 neutrons per second), DD fusion (2.5 MeV) neutron generators (up to 2 x 106 neutrons per second), and 252Cf spontaneous fission neutron sources (6.7 x 107 neutrons per second, 30 micrograms). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8 m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for 252Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield wall and entrance maze and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

D. L. Chichester; E. H. Seabury; J. M. Zabriskie; J. Wharton; A. J. Caffrey

2009-06-01

374

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

PubMed

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

2011-10-01

375

SOFT GAMMA-RAY SPECTRA EMITTED AFTER CAPTURE OF THERMAL NEUTRONS BY Cu⁶³, Cu⁶⁵, Ag¹°⁷, Ag¹°⁹ AND In¹¹⁵  

Microsoft Academic Search

A scintillation spectrometer with NaI(Tl) crystal was used for measuring ; the spectra of soft gamma rays produced by a thermal neutron capture in divided ; targets of isotopes of copper, silver, and indium and natural silver and copper. ; The values of gamma -ray intensities of the latter are in good agreement with ; the results obtained for targets

V. V. Sklyarevskii; E. P. Stepanov; B. A. Obinyakov

1958-01-01

376

Delayed neutron spectra by decay group for fissioning systems from /sup 227/Th through /sup 255/Fm  

SciTech Connect

The quality and quantity of delayed neutron precursor data has greatly improved over the past approximately 15 years. Supplementation of the data with model calculations and the use of models to extend the number of precursors to 271 is now practical. These data, along with improved fission-product parameters, permit direct calculations of aggregate behavior for many fissioning nuclides. The results can even be approximated using a few (usually six) temporal groups. This paper summarizes an extensive four-year effort to provide a complete set of evaluated data and emphasizes its use to generate the temporal approximations; precursor data and group values are intended for inclusion in ENDF/B-VI. 19 refs., 8 figs., 1 tab.

England, T.R.; Brady, M.C.

1988-01-01

377

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

PubMed

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. PMID:23126830

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

2012-10-01

378

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

379

Nondestructive testing: neutron radiography and neutron activation. January 1966-February 1981 (citations from the Metals Abstracts Data Base). Report for Jan 66-Feb 81  

SciTech Connect

This retrospective bibliography contains citations concerning neutron radiographic and neutron activation testing and inspection techniques and equipment for examining and evaluating a variety of materials and objects for the detection of flaws or defects. (Contains 85 citations fully indexed and including a title list.)

Not Available

1981-03-01

380

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.

Sezgin, Necmettin

2012-01-01

381

Relativistic Electron Energy Spectra of Active Galactic Nuclei in the Thin Synchrotron Limit. I. The Method  

NASA Astrophysics Data System (ADS)

Here we present a new method called "inverse synchrotron transform" (IST) to study the spectral energy distributions of active galactic nuclei. We demonstrate that it is possible to make use of Bayes Theorem for conditional probability in order to derive a unique, self-consistent solution for the electron energy spectra (EES), departing from the observed spectral energy distributions (S ED) and the assumption that the main physical process involved is the emission of thin synchrotron radiation. We show the close relationship between the EES so derived, and the electron energy distribution (EED), which in turn, does not have a unique solution, but depends on assumptions that fix the magnetic field strength. We test the IST method and find that it is capable of distinguishing between rather different EEDs that produce SEDs that are apparently very similar.

Salas, Luis; Cruz-Gonzalez, Irene; Carrasco, Luis

1995-07-01

382

Analysis of EMG signals in aggressive and normal activities by using higher-order spectra.  

PubMed

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

383

Collisional activation mass spectra of M-. ions of azo dyes containing 2-naphthol.  

PubMed

Collisionally activated decomposition mass spectra of M-. ions of azo dyes are presented. The compounds are of general structure Ar(1)--N = N--Ar(2), where Ar(1) is substituted phenyl and Ar(2) is 2-naphthol. Characteristic fragment ions observed include m/z 157, which corresponds to the 2-naphthol substituent with cleavage of the--N = N--bond represented as [Ar(2)--N]-.. Ion of general structure [Ar(1)--NH]- are also observed. Parent ion scans of m/z 157 provide a potential screening technique for 2-naphthol-containing axo dyes. Specific results are reported for the chloroform extract of FD&C Red #8, and capillary gas chromatographic introduction is compared with direct exposure probe introduction for the identification of dyes. PMID:2765698

Brumley, W C; Brilis, G M; Calvey, R J; Sphon, J A

1989-06-01

384

Instrumental neutron activation analysis of rib bone samples and of bone reference materials  

Microsoft Academic Search

The instrumental neutron activation analysis method was used for the determination of trace elements in rib bone samples taken\\u000a from autopsies of accident victims. The elements Br, Ca, Cl, Cr, Fe, Mg, Mn, Na, P, Sr, Rb, and Zn were determined in cortical\\u000a tissues by using short and long irradiations with thermal neutron flux of the IEA-R1m nuclear reactor. The

M. Saiki; M. K. Takata; S. Kramarski; A. Borelli

1999-01-01

385

Prompt gamma-ray neutron activation analysis of boron-10 in biological materials.  

PubMed

Prompt gamma-ray neutron activation analysis of 10B concentrations in biological samples was carried out using a germanium detector and single crystal silicon filtered neutron beams from the TRIGA-II reactor. The 10B concentrations of biological samples such as tumors, tissues, blood and cultured cells were estimated from calibration curves obtained by using standard samples containing various 10B concentrations. A method of measuring absolute 10B concentrations was also presented. PMID:2176195

Matsumoto, T; Aizawa, O

1990-01-01

386

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 510?11 g can be determined reliably, rapidly and easily. A wide range

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

1970-01-01

387

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

SciTech Connect

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

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

2010-10-10

388

Ionic absorption and emission features in X-ray spectra of active galactic nuclei  

NASA Astrophysics Data System (ADS)

I present a comprehensive study of ionic absorption and emission features observed in high-resolution X-ray spectra of active galactic nuclei (AGN). AGN are galaxies that harbor a central, actively-accreting supermassive black hole. Through accretion, gravitational energy is converted into radiation, spread roughly equally (in logarithmic intervals) over the entire electromagnetic spectrum. A simple model of a cone of material irradiated by a variable, featureless power-law spectrum produced at the nucleus plus an additional constant, hard component due to reflection in distant Compton-thick material is sufficient to fit the X-ray spectra of several different AGN. Depending on the orientation of the cone to the observer, the spectrum appears either as ionic absorption of the power law (for lines of sight directly down the cone to the nucleus) or as reprocessed emission in the irradiated material (for lines of sight transverse to the cone and for which the nucleus is highly obscured by some other medium). The hard reflection component is observed in both orientations. A broad density distribution (over several orders of magnitude) at each position in the ionic absorber is also observed. For observations down the cone to the nucleus, I argue that the observed broad spectral features are more likely artifacts of absorption of the featureless power-law spectrum plus some contribution from the constant reflection component rather than relativistically-broadened emission lines arising from the inner regions of an accretion disk. In our model, all discrete and continuous ionic absorption and emission features are based on atomic data calculated using the Flexible Atomic Code (FAC).

Kinkhabwala, Ali Amir

2003-12-01

389

Prediction of mutagenic activity of nitrophenanthrene and nitroanthracene isomers by simulated IR and Raman spectra.  

PubMed

This paper expands upon our original work on nitroanthracenes in (Alparone, A., Librando, V., 2012. Spectrochim. Acta A 89, 129-136) on the series of nitrophenanthrene isomers. Geometries, electric properties, IR and Raman spectra of 1-, 2-, 3-, 4- and 9-nitrophenanthrene (1-NP, 2-NP, 3-NP, 4-NP and 9-NP) were obtained and analyzed using Density Functional Theory calculations. The balance between steric and ?-conjugative interactions determines the order of stability 4-NP<1-NP~9-NP<2-NP?3-NP. IR and Raman spectral zones between 1000 and 1600 cm(-1) show intense bands noticeably affected by the position of the substituent, being potentially useful to discriminate and monitor the investigated isomers. Dipole moments, summations of IR intensity (?I(IR)) and Raman activity (?A(Raman)) over the 3N-6 vibrational modes are sensitive to the structure, increasing steadily from the non-planar to the planar isomers. Good linear relationships between the ?I(IR) (r=0.90) and ?A(Raman) (r=0.99) against the Salmonella typhimurium strain TA98 mutagenic activity of nitrophenanthrenes and isomeric nitroanthracenes are found. On the basis of the structural and vibrational properties, 4-NP seems to have not mutagenic activity, while the unknown TA98 mutagenic potency of 1-nitroanthracene is predicted to be between that of 9-NP and 3-NP. Calculated ?I(IR) and ?A(Raman) values could be used as molecular descriptors for QSARs applications of series of isomers. PMID:22809700

Alparone, Andrea; Librando, Vito

2013-01-01

390

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

391

Iodine-129 separation and determination by neutron activation analysis  

SciTech Connect

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

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

1981-01-01

392

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

393

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

PubMed

The laser megajoule (LMJ) and the National Ignition Facility (NIF) plan to demonstrate thermonuclear ignition using inertial confinement fusion (ICF). The neutron yield is one of the most important parameters to characterize ICF experiment performance. For decades, the activation diagnostic was chosen as a reference at ICF facilities and is now planned to be the first nuclear diagnostic on LMJ, measuring both 2.45 MeV and 14.1 MeV neutron yields. Challenges for the activation diagnostic development are absolute calibration, accuracy, range requirement, and harsh environment. At this time, copper and zirconium material are identified for 14.1 MeV neutron yield measurement and indium material for 2.45 MeV neutrons. A series of calibrations were performed at Commissariat a? l'Energie Atomique (CEA) on a Van de Graff facility to determine activation diagnostics efficiencies and to compare them with results from calculations. The CEA copper activation diagnostic was tested on the OMEGA facility during DT implosion. Experiments showed that CEA and Laboratory for Laser Energetics (LLE) diagnostics agree to better than 1% on the neutron yield measurement, with an independent calibration for each system. Also, experimental sensitivities are in good agreement with simulations and allow us to scale activation diagnostics for the LMJ measurement range. PMID:21806179

Landoas, Olivier; Glebov, Vladimir Yu; Ross, Bertrand; Briat, Michelle; Disdier, Laurent; Sangster, Thomas C; Duffy, Tim; Marmouget, Jean Gabriel; Varignon, Cyril; Ledoux, Xavier; Caillaud, Tony; Thfoin, Isabelle; Bourgade, Jean-Luc

2011-07-01

394

Neutron spectrometry for radiation protection: Three examples  

SciTech Connect

Workers and the general public are exposed to neutron radiation from a variety of sources, including fission and fusion reactors, accelerators, the nuclear fuel and nuclear weapons cycles, and cosmic rays in space, in aircraft and on the earth. Because the health effects of neutrons depend strongly on their energy, neutron spectrometry is essential for accurate risk-related neutron dosimetry. In addition, the penetration of neutrons through protective shielding changes their energy and can be difficult to calculate reliably, so the measurement of energy spectra is often needed to verify neutron transport calculations. The Environmental Measurements Laboratory has been measuring neutron energy spectra for over 20 years, primarily with multisphere (or Bonner sphere) spectrometers. Because of this experience, the Laboratory has responded to a number of requests to provide reference neutron energy spectra at critical locations in or near nuclear facilities and radiation fields. This talk will describe the author`s instruments and three recent examples of their use: outside the Princeton Tokamak Fusion Test Reactor (TFTR), up to two kilometers from the Army Pulse Radiation Facility (APRF) bare reactor, and in a Canadian Forces jet aircraft at commercial aviation altitudes. All of these studies have implications beyond routine occupational radiation protection. For example, the APRF measurements are part of the broad effort to resolve the discrepancy between measured and calculated thermal neutron activation at Hiroshima, one of the most important unsolved problems in radiation dosimetry.

Goldhagen, P.

1995-12-31

395

Neutron activation analysis with [sup 252]Cf sources at Savannah River site  

Microsoft Academic Search

The Savannah River Technology Center (SRTC) has used a [sup 252]Cf neutron activation analysis (NAA) facility routinely since 1976. Methods for a much larger and more highly automated activation analysis system at the Savannah River Site (SRS) C reactor were developed at the [sup 252]Cf facility. Although the C reactor facility is no longer is use, the [sup 252]Cf facility

Sigg

1993-01-01

396

Neutron activation analysis of alternative waste forms at the Savannah River Laboratory  

Microsoft Academic Search

A remotely controlled system for neutron activation of candidate high-level waste (HLW) isolation forms was built by the Savannah River Laboratory at a Savannah River Plant reactor. With this system, samples can be irradiated for up to 24 hours and transferred through pneumatic tubing to a shielded repository unitl their activity is low enough for them to be handled in

1981-01-01

397

Trace element analysis of biological materials by thermal and epithermal neutron activation analysis  

Microsoft Academic Search

A scheme for instrumental neutron activation analysis of biological materials is proposed. The scheme is based on a combination\\u000a of thermal and epithermal activation. The accuracy is evaluated by analyzing 4 standard reference materials. Results from\\u000a the analysis of human blood serum and plasma are given.

K. Kostadinov; R. Djingova

1981-01-01

398

THE DETERMINATION OF URANIUM AND THORIUM IN ROCKS BY NEUTRON ACTIVATION ANALYSIS  

Microsoft Academic Search

A neutron activation method is described for the determination of Th and ; U in rocks at the microgram and submicrogram levels. Radiochemical separations ; are carried out using the alpha-active nuclides Pa²³¹ and Np²³⁷ as ; tracers. The method is applied to the standard granite G1 and the standard ; diabase W1. (auth);

J. W. Morgan; J. F. Lovering

1963-01-01

399

3D neutronic calculations: CAD-MCNP methodology applied to vessel activation in KOYO-F  

NASA Astrophysics Data System (ADS)

This paper presents a methodology for 3D neutronic calculations suitable for complex and extensive geometries. The geometry of the system design is first fully modelled with a CAD program, and subsequently processed through a MCNP-CAD interface in order to generate an MCNP geometry file. Neutronic irradiation results are finally achieved running the MCNPX program, where the geometry input card used is directly the MCNP-CAD interface output. This methodology enables accurate neutronic calculations for complex geometries characterised by high detail levels. This procedure will be applied to the Fast Ignition Fusion Reactor KOYO-F to determine first neutron fluxes calculations along the blanket as well as the material activation in the reduced martensitic 9Cr-1Mo steel vessel.

Herreras, Y.; Lafuente, A.; Sordo, F.; Cabellos, O.; Perlado, J. M.

2008-05-01

400

Development of advanced neutron/gamma generators for imaging and active interrogation applications  

NASA Astrophysics Data System (ADS)

We report here on the development of neutron and photon sources for use in imaging and active interrogation applications, where there is a growing urgency for more advanced interrogation tools. These devices include high yield D-D, D-T and T-T fusion reaction based neutron generators and also low energy nuclear reaction based high-energy gamma generators. One common feature in these various devices is the use of a high-efficiency, RF-induction discharge ion source. This discharge method provides high plasma density for high output current, high atomic species from molecular gases for high efficiency neutron or gamma generation and long lifetime. Predictable discharge characteristics of these plasma generators allow accurate modeling for both the beam dynamics and for the heat loads at the target spot. Current status of the neutron and gamma generator development with experimental data will be presented.

Reijonen, J.; Andresen, N.; Gicquel, F.; Gough, R.; King, M.; Kalvas, T.; Leung, K.-N.; Lou, T.-P.; Vainionpaa, H.; Antolak, A.; Morse, D.; Doyle, B.; Miller, G.; Piestrup, M.

2007-04-01

401

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

PubMed

The feasibility of accelerator-based in vivo neutron activation analysis of nitrogen has been investigated. It was found that a moderated neutron flux from approximately 10 microA of 2.5 MeV protons on a 9Be target performed as well as, and possibly slightly better than the existing isotope-based approach in terms of net counts per unit subject dose. Such a system may be an attractive alternative to the widespread use of (238,239)Pu/Be or 252Cf neutron sources, since there is more flexibility in the energy spectrum generated by accelerator-based neutron sources. From a radiation safety standpoint, accelerators have the advantage in that they only produce radiation when in operation. Furthermore, an accelerator beam can be pulsed, to reduce background detected in the prompt-gamma measurement, and such a device has a wide range of additional biological and medical applications. PMID:11761098

O'Meara, J M; Blackburn, B W; Chichester, D L; Gierga, D P; Yanch, J C

2001-12-01

402

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

SciTech Connect

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

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

1980-01-01

403

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

404

Analysis of the Rotationally-Resolved Spectra of the Vibronically-Active Molecules  

NASA Astrophysics Data System (ADS)

Rotational structure of the vibronically coupled, and specifically, Jahn-Teller active molecules in isolated vibronic states has been studied for the decades, and the corresponding Hamiltonian and relationship of its parameters to the molecular properties are well-established, at least for the e vibronic states. However, in many cases an isolated state approach, both for the ground and vibronically excited levels, does not produce satisfactory results either because the experimentally obtained parameters of such model are not physically transparent, or the model fails to predict the observed spectrum to the experimental accuracy. To circumvent these problems, we develop, from the molecular symmetry standpoint, an effective coupled state rotational Hamiltonian directly accounting for the interactions within the appropriate subset of the interacting vibronic states. This approach is expected to be useful for the analysis of the rotational level structure of the closely-spaced vibronic levels such as those occurring in the vibrationally excited manifolds of the open-shell molecules. The application of this approach to the spectra of the nitrate radical, NO_3, in the Jahn-Teller active {A}^2E'' state, will be discussed. D. G. Melnik, T. A. Miller and J. Liu, TI15, 67^th Molecular Spectroscopy Symposium, Columbus, 2012 M. Roudjane, T. J. Codd and T. A. Miller, TI03, 67^th Molecular Spectroscopy Symposium, Columbus, 2012

Melnik, Dmitry G.; Miller, Terry A.

2013-06-01

405

FUV Spectra of Evolved Late-K and M Stars: Mass Loss Revisited and Stellar Activity  

NASA Technical Reports Server (NTRS)

This is the final report for the FUSE Cycle 1 program A100: FUV Spectra of Evolved Late-K and M Stars: Mass Loss revisited and Stellar Activity. Targets alpha TrA (K3 II) and gamma Cru (M3 III) were originally assigned 25 ksec each, to be observed in the medium aperture. Once the in-flight performance and telescope alignment problems were known, the observations were reprogrammed to optimized the scientific return of the program. Alpha TrA was scheduled for 25 ksec observations in both the medium and large apertures. The principle aim of this program was to measure the stellar FUV line and continuum emission, in order to estimate the photoionization radiation field and to determine the level of stellar activity through the fluxes in the collisionally excited high temperature diagnostics: C III 977Angstroms and O VI 1032,1038Angstrom doublet. The medium aperture observations were obtained successfully while the large aperture observations were thought by Johns Hopkins University (JHU)to be lost to satellite problems. There was insufficient signal-to- noise in the medium aperture short wavelength Sic channels to do quantitative science.

Harper, Graham M.

2002-01-01

406

Rare earth elements content in geological samples from eastern desert, Egypt, determined by instrumental neutron activation analysis.  

PubMed

Twenty representative geological samples (tonalite, granodiorite, adamellite, syenogranite, rapakivi syenogranite, alkali feldspar granite and monzogranite) were collected from G. Kattar area in Eastern Desert, Egypt, for analysis by instrumental neutron activation as a sensitive nondestructive analytical tool for the determination of 14 rare earth elements (REEs) and to find out the following: (1) what information could be obtained about the REEs and distribution patterns of REEs in geological samples under investigation, (2) to estimate the accuracy, reproducibility and detection limit of the INAA method in case of the given samples. The samples were properly prepared together with standard reference material and simultaneously irradiated in a neutron flux of 7x10(11)n/cm(2)s in the TRIGA Mainz research reactor facilities. The gamma spectra were collected by an HPGe detector and the analysis was done by means of a computerized multichannel analyzer. The choice of the nuclear reaction, irradiation and decay times, and of the proper gamma radiation in counting are presented and discussed. The results are found to be in good agreement with certified values. PMID:20236830

El-Taher, A

2010-09-01

407

Comparison of calculated and experimental dosimetry activities for benchmark neutron fields  

SciTech Connect

New dosimetry cross-section evaluations have been made available to the reactor community. Most dosimetry-quality evaluations include a section (File 33) that defines the uncertainty and covariance matrix for the dosimetry reaction cross section. This paper compares the latest computed cross-section activities for benchmark neutron fields with experimental data. Uncertainty data is usually reported with experimental measurements. This work also presents uncertainty data for the calculated activities. The calculated uncertainty values include a full uncertainty propagation using the cross-section evaluation, energy-dependent covariance data as well as the uncertainty attributed to the knowledge of the neutron spectrum.

Griffin, P.J.

1997-02-01

408

State-of-the-art of computational tools and data for IFMIF neutronics and activation analyses  

NASA Astrophysics Data System (ADS)

An overview is presented of the state-of-the-art of computational tools, data and models developed for neutronics and activation analyses of the IFMIF neutron source. Significant progress has been achieved in making available computational tools for simulating the d-Li neutron (and photon) source term with the McDeLicious Monte Carlo code and associated d+ 6,7Li cross-section data, in generating neutronics Monte Carlo geometry models by the McCad conversion software, and in providing the interface programme MCDO to enable coupled 3D Monte Carlo and discrete ordinates shielding calculations. In the field of nuclear data for IFMIF, a major milestone has been achieved with the launching of the FENDL-3 research project co-ordinated by the IAEA. Another major achievement is the production of the European Activation File, version EAF-2007, which has the neutron energy range extended to the needs of IFMIF and also provides calculated data libraries for deuteron and proton induced activation reactions.

Fischer, U.; Klix, A.; Li, J.; Pereslavstev, P.; Simakov, S. P.; Forrest, R. A.; Wasastjerna, F.

2011-10-01

409

Inclusive neutron spectra at 0/sup 0/ from the reactions Pb(Ne,n)X and NaF(Ne,n)X at 390 and 790 MeV per nucleon  

SciTech Connect

Inclusive neutron spectra at 0/sup 0/ were measured from both 390- and 790-MeV/u Ne ions on targets of Pb and NaF. A striking peak at a neutron energy slightly below the beam energy per nucleon has a width (in the projectile rest frame) of approx.58 MeV/c, which is essentially the same for these two energies and these two targets. We suggest that this narrow peak is projectile evaporation and that it is superimposed on the broader fragmentation process predicted by statistical models. The high-momentum region of the cross section may reflect collective behavior.

Madey, R.; Varga, J.; Baldwin, A.R.; Anderson, B.D.; Cecil, R.A.; Fai, G.; Tandy, P.C.; Watson, J.W.; Westfall, G.D.

1985-09-30

410

Neutron irradiation effects on electrical properties and deep-level spectra in undoped n-AlGaN/GaN heterostructures  

SciTech Connect

The effect of neutron irradiation on the electrical properties of undoped n-AlGaN/GaN heterostructures is reported. The two-dimensional electron-gas (2DEG) mobility starts to decrease at neutron doses above 10{sup 14} cm{sup -2}, while the 2DEG concentration slightly increases at low doses and decreases dramatically for doses higher than 2.5x10{sup 16} cm{sup -2}. The result is that the mobility/concentration product (a figure of merit for transistors) starts to decrease appreciably after the dose of 10{sup 15} cm{sup -2}. Capacitance-voltage and admittance spectroscopies, indicate that tunneling of electrons into the states near E{sub c}-0.21 eV in AlGaN is a serious factor when cooling down the virgin or lightly irradiated samples. For heavily irradiated samples the states in AlGaN are close to 0.3 and 0.45 eV, respectively, from the bottom of the conduction band. Deep-level spectroscopy measurements reveal the presence of hole traps with apparent activation energies of 0.18 and 0.21 eV for lightly irradiated samples and deeper hole traps with activation energies of 0.6 and 1 eV in heavily irradiated samples.

Polyakov, A.Y.; Smirnov, N.B.; Govorkov, A.V.; Markov, A.V.; Pearton, S.J.; Kolin, N.G.; Merkurisov, D.I.; Boiko, V.M. [Institute of Rare Metals, B. Tolmachevsky 5, Moscow 119017 (Russian Federation); Department of Materials Science and Engineering, University of Florida, 132 Rhines Hall, Gainesville, Florida 32611 (United States); Obninsk Branch of Federal State Unitary Enterprise, Karpov Institute of Physical Chemistry, 249033 Obninsk, Kaluga region, Kiev Avenue (Russian Federation)

2005-08-01

411

Analysis of active neutron multiplicity data for Y-12 skull oxide samples  

SciTech Connect

Previous work on active neutron multiplicity measurements and analyses is summarized. New active multiplicity measurements are described for samples of Y-12 skull oxide using an Active Well Coincidence Counter and MSR4 multiplicity electronics. Neutron multiplication values for the samples were determined from triples/doubles ratios. Neutron multiplication values were also obtained from Monte Carlo calculations using the MCNP code and the results compared with the experimental values. A calibration curve of AmLi source-sample coupling vs neutron multiplication was determined and used for active multiplicity assay of the skull oxides. The results are compared with those obtained from assay with the conventional calibration-curve technique, where the doubles rate is calibrated vs the {sup 235}U mass. The coupling-multiplication relationship determined for the skull oxides is compared with that determined earlier for pure high-enrichment uranium metal and pure uranium oxide. Conclusions are drawn about the application of active multiplicity techniques to uranium assay. Additional active multiplicity measurements and calculations are recommended.

Krick, M.S.; Ensslin, N. [Los Alamos National Lab., NM (United States); Ceo, R.N.; May, P.K. [Oak Ridge Y-12 Plant, TN (United States)

1996-09-01

412

Manifestation of structure and intermolecular interactions of biologically active brassinosteroids in infrared spectra  

NASA Astrophysics Data System (ADS)

We have analyzed the IR spectra obtained for steroidal phytohormones 24-epibrassinolide, 24-epicastasterone, 28-homobrassinolide, and 28-homocastasterone. The characteristic frequencies of the stretching vibrations of the hydrocarbon groups CH3, CH2, and CH and also the C=O groups in the spectra of brassinolides are higher than in the spectra of castasterones, which makes it possible to identify them from the IR spectra. Study of the spectra of these brassinosteroids in different media (pressed samples in KBr, films, solutions in CHCl3 and CDCl3) allowed us to establish the presence of intermolecular interactions in which C=O and OH groups, OH-OH groups participate, and also the possible formation of intramolecular hydrogen bonds between the OH groups of the molecules.

Borisevich, N. A.; Skornyakov, I. V.; Khripach, V. A.; Tolstorozhev, G. B.; Zhabinskii, V. N.

2007-09-01

413

Studies of neutron and proton nuclear activation in low-Earth orbit  

NASA Technical Reports Server (NTRS)

The expected induced radioactivity of experimental material in low Earth orbit was studied for characteristics of activating particles such as cosmic rays, high energy Earth albedo neutrons, trapped protons, and secondary protons and neutrons. The activation cross sections for the production of long lived radioisotopes and other existing nuclear data appropriate to the study of these reactions were compiled. Computer codes which are required to calculate the expected activation of orbited materials were developed. The decreased computer code used to predict the activation of trapped protons of materials placed in the expected orbits of LDEF and Spacelab II. Techniques for unfolding the fluxes of activating particles from the measured activation of orbited materials are examined.

Laird, C. E.

1982-01-01

414

Studies on the synthesis, spectra, catalytic and antibacterial activities of binuclear ruthenium(II) complexes  

NASA Astrophysics Data System (ADS)

A new series of stable binuclear ruthenium(II) carbonyl complexes of the general formula [{RuX(CO)(EPh 3) 2} 2L] (where X = H or Cl; E = P or As and L = dibasic tetradentate diacetyl resorcinol (H 2-DAR)) have been synthesised by reacting ruthenium(II) starting complexes [RuHX(CO)(EPh 3) 3] (where X = H or Cl; E = P or As) and 4,6-diacetylresorcinol (H 2-DAR) ligand in benzene medium. The structure of the new binuclear ruthenium(II) carbonyl complexes was established using elemental analysis, spectra (FT-IR, UV-vis and 1H NMR), electrochemical and thermal studies. In these reactions, the 4,6-diacetylresorcinol (H 2-DAR) ligand behaves as a binegative tetradentate chelating ligand coordinating through O,O atoms of both the carbonyl and phenolic C-O groups by replacing a molecule of PPh 3/AsPh 3 and a hydride ion from the starting complexes. Further, all these complexes were also employed as new catalysts for the oxidation of primary and secondary alcohols in the presence of N-methylmorpholine-N-oxide (NMO) as a more viable co-oxidant. The free ligand and their metal complexes have also been screened for their antibacterial activity against the growth of gram +ve and gram -ve bacterial cultures.

Krishnamoorthy, P.; Sathyadevi, P.; Deepa, K.; Dharmaraj, N.

2010-09-01

415

Damping scaling factors for vertical elastic response spectra for shallow crustal Earthquakes in active tectonic regions  

USGS Publications Warehouse

Ground-motion prediction equations (GMPEs) for elastic response spectra are typically developed at a 5% viscous damping ratio. In reality, however, structural and non-structural systems can have other damping ratios. This paper develops a new model for a Damping Scaling Factor (DSF) that can be used to adjust the 5% damped spectral ordinates predicted by a GMPE for damping ratios between 0.5 to 30%. The model is developed based on empirical data from worldwide shallow crustal earthquakes in active tectonic regions. Dependencies of the DSF on potential predictor variables such as the damping ratio, spectral period, ground motion duration, moment magnitude, source-to-site distance, and site conditions are examined. The strong influence of duration is captured by inclusion of both magnitude and distance in the DSF model. Site conditions show weak influence on the DSF. The proposed damping scaling model provides functional forms for the median and logarithmic standard deviation of DSF, and is developed for both RotD50 and GMRotI50 horizontal components. A follow-up paper develops a DSF model for vertical ground motion.

Rezaeian, Sanaz; Bozorgnia, Yousef; Idriss, I.M.; Abrahamson, Norman; Campbell, Kenneth; Silva, Walter

2013-01-01

416

Monte-carlo simulation of the prompt gamma neutron activation analysis system with a femtosecond laser  

NASA Astrophysics Data System (ADS)

The prompt gamma neutron activation analysis (PGNAA) system is a useful tool to detect the concentrations of the various composite elements of a sample by measuring the prompt gammas that are activated by neutrons. The composition in terms of the constituent elements is essential information for the identification of the material species of any unknown object. A PGNAA system initiated by a high-power laser has been designed and optimized by using a Monte-Carlo simulation. In order to improve the signal-to-background ratio, we designed an improved neutron-shielding structure and imposed a proper time window in the analysis. In particular, the yield ratio of nitrogen to carbon in a TNT sample was investigated in detail. These simulation results demonstrate that the gamma rays from an explosive sample under a vast level of background can indeed be identified.

Shim, Hyunha; Hong, Byungsik; Lee, Kyong-Sei; Lee, Sungman; Cha, Hyungki

2012-09-01

417

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

418

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

NASA Astrophysics Data System (ADS)

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.

2008-10-01

419

The tokamak as a neutron source  

Microsoft Academic Search

This paper describes the tokamak in its role as a neutron source, with emphasis on experimental results for D-D neutron production. The sections summarize tokamak operation, sources of fusion and non-fusion neutrons, principal neutron detection methods and their calibration, neutron energy spectra and fluxes outside the tokamak plasma chamber, history of neutron production in tokamaks, neutron emission and fusion power

H. W. Hendel; D. L. Jassby

1989-01-01

420

A neutron activation technique based on deferred gamma rays applied to the quantification of fluorine in fluorspar mining samples  

NASA Astrophysics Data System (ADS)

In this work the technique of deferred neutron activation to determine the fluoride content in fluorspar mining samples has been used. The results of the analysis carried out by neutron activation of samples from different points of a fluorspar mining concentration plant are shown. These results are compared with the chemical analysis results normally carried out at the plant.

Rey-Ronco, M. A.; Alonso-Snchez, T.; Castro-Garca, M. P.

2011-10-01

421

Errors in determination of total body protein by in vivo neutron activation of nitrogen due to non-uniform neutron fluence inside the patient.  

PubMed

Total body protein can be estimated by in vivo neutron activation of nitrogen. The method is based on capture of thermal neutrons in a 14N(n,g )15N reaction. Sources of error associated with this method, such as background subtraction, variations in detection efficiency, etc, are analysed. Different neutron reactions (absorption, elastic and inelastic scattering) cause the neutron fluence to decrease inside the body. The activation profile through the body is non-uniform which causes errors in the calculation of total body nitrogen. A reduction of nitrogen by 5% in a 3 cm thick volume near the body surface would result in an error in the determination of total body nitrogen of approximately 0.3%. The error induced by changes in thickness of the subcutaneous fat has also been estimated and the results show that a 5 mm change in subcutaneous fat thickness changes the count rate from nitrogen by 5%. PMID:24394281

Tlli, J; Larsson, L; Alpsten, M

1995-03-01

422

Use of Activation Technique and MCNP Calculations for Measurement of Fast Neutron Spatial Distribution at the MJ Plasma Focus Device  

SciTech Connect

In this paper Plasma-Focus (PF) neutron emission properties have been studied using Monte Carlo calculations for neutron and photon transport. A Thermal Neutron Scaling Factor as a function of angular position of silver activation detectors placed around MJ Plasma Focus (PF-1000) device has been calculated. Detector responses calculated for 2.5 MeV neutrons and neutrons produced by Am-Be calibration source have been obtained .The results have shown the detector response dependence on the kind of calibration neutron source and on local geometrical/structural characteristics of the PF-1000 devices. Thus the proper calibration procedure ought to be performed for correct measurement of neutron yield within Plasma-Focus devices.

Bienkowska, B.; Scholz, M. [Institute of Plasma Physics and Laser Microfusion, P.O. Box 49, 00-908 Warsaw (Poland); Wincel, K.; Zareba, B. [Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk (Poland)

2008-03-19

423

Measurement and analysis of activation induced in titanium with fusion peak neutrons  

NASA Astrophysics Data System (ADS)

The intense neutron flux densities in fusion reactor blankets produce activation in the blanket materials relevant to operational safety, decommissioning, etc. The aim of the present work is to check the European Activation System EASY-2007 for its capability to predict important gamma activities induced in titanium in a fusion neutron field. Many advanced low-activation materials for fusion applications contain titanium, most notably in the breeder material Li 2TiO 3. In the present work, a small sample of Ti was irradiated with the intense DT neutron generator of Technical University of Dresden. The gamma-radioactivity following irradiation was measured and nuclide activities were derived. For each of the measured gamma activities, the corresponding value was calculated with EASY, and calculation-to-experiment ratios ( C/ E) were determined. EASY predicted the induced gamma activities, isotopes of scandium, well with some overestimation for 47Sc. The results of this measurement together with available EXFOR and validated state-of-the-art activation libraries are discussed.

Klix, A.; Domula, A.; Forrest, R.; Zuber, K.

2011-10-01

424

LOFT experimental measurements uncertainty analyses. Volume XX. Fluid-velocity measurement using pulsed-neutron activation  

SciTech Connect

Analyses of uncertainty components inherent in pulsed-neutron-activation (PNA) measurements in general and the Loss-of-Fluid-Test (LOFT) system in particular are given. Due to the LOFT system's unique conditions, previously-used techniques were modified to make the volocity measurement. These methods render a useful, cost-effective measurement with an estimated uncertainty of 11% of reading.

Lassahn, G.D.; Taylor, D.J.N.

1982-08-01

425

Neutron activation analysis of deep sea sediments from the regions near Japan  

Microsoft Academic Search

Eighteen trace elements, including seven rare earth elements (REEs), and major and minor elements in the sediment samples from the Japan Sea and the northwestern Pacific near Japan were determined with instrumental neutron activation analysis (INAA). Most REE patterns (chondrite-nomalized) of the sediments were nearly identical to the patterns of terrigenous materials without cerium anomaly whereas the La\\/Yb ratio varied

Y. Minai; U. Tsunogai; H. Takahashi; J. Ishibashi; R. Matsumoto; T. Tominaga

1997-01-01

426

Applications of neutron activation to microelectronic materials research at the Cornell TRIGA reactor  

Microsoft Academic Search

We present results from our use of neutron activation analysis (NAA) for the measurement and interpretation of the elemental content of materials being researched for applications in microelectronics. Examples include characterization of silicon-germanium and nickel silicide alloys, magnesium silicate crystals and ceramics for packaging of integrated circuits. High resolution delayed X-ray spectroscopy has been successfully employed as a complement to

S. C. McGuire; T. Z. Hossain; C. Golkowski; N. D. Kerness; J. D. Sulcer

1995-01-01

427

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

428

A SIMPLE METHOD DETERMINING GOLD IN BIOLOGICAL MATERIAL BY NEUTRON ACTIVATION ANALYSIS  

Microsoft Academic Search

A method of neutron activation analysis for the determination of gold in ; biological material, based on the chemical separation of gold by doubled ; precipitation with oxalic acid and on counting with a Geiger-Muller tube, is ; described. The accuracy of this method to plus or minus 5% for determining 10\\/; sup -7\\/ to 10⁻⁶ g of gold. It

Rakovic

1963-01-01

429

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

430

The Use of Neutron Activation Analysis in Environmental and Biomedical Research  

NASA Astrophysics Data System (ADS)

Favorable features of neutron activation analysis (NAA) are highlighted and the most important modes of the technique are mentioned. Examples are given of the advantageous use of NAA for elemental characterization of ambient air and combustion aerosols, studying transfer of pollutants to agricultural plants, and the technique's applications in occupational health and nutritional studies.

Ku?era, Jan

2007-11-01

431

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. Smodi; M. Dermelj; R. Ja?imovi?

1995-01-01

432

Multielemental analysis of vegetarian human diets and dietary components by neutron activation  

Microsoft Academic Search

Two vegetarian diet samples representative of the Indian sub-continent were prepared (in raw form) by the proportionate blending method for adolescent and adult age groups. These along with its components, viz. wheat, rice flours and pulses, were analyzed for 12 minor and trace elements by instrumental neutron activation analysis (INAA) and high resolution ?-ray spectrometry. Bowen's kale was also analyzed

Dhananjay L. Samudralwar; Amar N. Garg

1994-01-01

433

Determination of the lanthanoids in a neutral hot spring water by neutron activation analysis  

Microsoft Academic Search

Determination of the lanthanoids in a neutral hot spring water has been studied by menas of neutron activation analysis. The aluminium coprecipitation process, which used aluminium as the collector of the lanthanoids, was incorporated in the preparation of a sample for irradiation. Nine lanthanoids, La, Ce, Nd, Sm, Eu, Tb, Tm, Yb and Lu, were determined at ppt levels with

T. Oi; Y. Kikawada; T. Honda; T. Ossaka; H. Kakihana

1990-01-01

434

Neutron activation determination of the oxygen content in the Luna 16 lunar surface material  

NASA Technical Reports Server (NTRS)

The O2 content in the No. 16/078 sample of lunar surface material returned by the Luna 16 automatic station was determined by activation using 14 MeV neutrons. The O2 content in the sample is 42.1 + or - 1.2 weight percent.

Nady, A.; Chekke, A.; Sabo, E.; Forsag, B.; Zemplen, E.

1974-01-01

435

Separation of antimony from synthetic cloth: Application in forensic science using neutron activation analysis  

Microsoft Academic Search

SummaryA simple ion-exchange separation procedure was developed for selective removal of antimony from synthetic cloth to facilitate determination of several trace elements frequently used to identify gunshot residues by neutron activation analysis. Radiotracers of Sb, Ba, Cu, Co, As, Zn, Hg and Ag were employed to optimize the developed procedure. The method involves the quantitative retention of the above elements,

C. A. Bhadkambekar; K. K. Swain; S. R. Kayasth; T. Mukherjee

2005-01-01

436

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

437

Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.  

SciTech Connect

An innovative helium3 high pressure gas detection system, made possible by utilizing Sandia's expertise in Micro-electrical Mechanical fluidic systems, is proposed which appears to have many beneficial performance characteristics with regards to making these neutron measurements in the high bremsstrahlung and electrical noise environments found in High Energy Density Physics experiments and especially on the very high noise environment generated on the fast pulsed power experiments performed here at Sandia. This same system may dramatically improve active WMD and contraband detection as well when employed with ultrafast (10-50 ns) pulsed neutron sources.

Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew

2007-12-01

438

A new automated sample transfer system for instrumental neutron activation analysis.  

PubMed

A fully automated and fast pneumatic transport system for short-time activation analysis was recently developed. It is suitable for small nuclear research reactors or laboratories that are using neutron generators and other neutron sources. It is equipped with a programmable logic controller, software package, and 12 devices to facilitate optimal analytical procedures. 550 ms were only necessary to transfer the irradiated capsule (diameter: 15 mm, length: 50 mm, weight: 4 gram) to the counting chamber at a distance of 20 meters using pressurized air (4 bars) as a transport gas. PMID:20369063

Ismail, S S

2010-01-01

439

A New Automated Sample Transfer System for Instrumental Neutron Activation Analysis  

PubMed Central

A fully automated and fast pneumatic transport system for short-time activation analysis was recently developed. It is suitable for small nuclear research reactors or laboratories that are using neutron generators and other neutron sources. It is equipped with a programmable logic controller, software package, and 12 devices to facilitate optimal analytical procedures. 550?ms were only necessary to transfer the irradiated capsule (diameter: 15?mm, length: 50?mm, weight: 4 gram) to the counting chamber at a distance of 20 meters using pressurized air (4 bars) as a transport gas.

Ismail, S. S.

2010-01-01

440

Impurities analysis of polycrystalline silicon substrates: Neutronic Activation Analysis (NAA) and Secondary Ion Mass Spectrometry (SIMS)  

NASA Astrophysics Data System (ADS)

In this study we have determined the concentration of some impurities such as carbon, iron, copper, titanium, nickel of the flat product (polycrystalline silicon). These impurities generate a yield decrease in the photovoltaic components. The material (polycrystalline silicon) used in this work is manufactured by the Unit of Silicon Technology Development (UDTS Algiers, Algeria). The 80 kg ingot has been cutted into 16 briquettes in order to have plates (flat product) of 100 mm100 mm dimensions. Each briquette is divided into three parts top (T), middle (M) and bottom (B). For this purpose, the following instrumental analysis techniques have been employed: neutronic analysis (neutronic activation analysis) and secondary ion mass spectrometry (SIMS). Masses of 80 mg are sampled and form of discs 18 mm in diameter, then exposed to a flux of neutron of 2.1012 neutron cm-2 s-1 during 15 min. The energetic profile of incidental flux is constituted of fast neutrons (?R = 3.1012 n.cm-2 s-1 E = 2 Mev), thermal neutrons (?TH = 1013 n.cm-2 s-1 E = 0.025 ev) and epithermal neutrons (?epi = 7.1011 n cm-2 s-1 E>4.9 ev), irradiation time 15 mn, after 20 mn of decrement, acquisitions of 300 s are carried out. The results are expressed by disintegration per second which does not exceed the 9000 Bq, 500 Bq and 2600 Bq, respectively for copper, titanium and nickel. It is observed that the impurities concentrations in the medium are higher. The impurities in the bottom of the ingots originate from the crucible. The impurities in the top originate from impurities dissolved in the liquid silicon, which have segregated to the top layer of the ingot and after solidification diffuse. Silicon corresponds to a mixture of three isotopes 28Si, 29Si and 30Si. These elements clearly appear on the mass spectrum (SIMS). The presence of iron and the one of nickel has been noticed.

Lounis, A.; Lenouar, K.; Gritly, Y.; Abbad, B.; Azzaz, M.; Tabi, K.

2010-01-01

441

Installation of a neutron bender-lens for spatially resolved prompt-gamma activation analysis  

SciTech Connect

The author have previously reported the focusing of a neutron beam by a lens composed of a bundle of glass capillary fibers using multiple grazing-angle reflection. The lens collects neutrons from a 45- x 50-mm beam from a {sup 58}Ni guide viewing a cold source and focuses them to a spot 0.53 mm full-width at half-maximum (FWHM) with a gain in flux of a factor of 80. Spatially resolved prompt-gamma activation analyses of boron, cadmium, and gadolinium have been demonstrated with submillimetre spatial resolution. The lens brings only a few percent of the incident neutrons to the focus. Because this lens is symmetrical, the high-intensity focal spot is in the shadow of the incident beam, which gives a high background. An object diaphragm of {sup 6}LiF (tapering to 1-mm aperture) is used just upstream from the sample to improve the contrast, but because this diaphragm and its support are necessarily located in the direct view of the gamma-ray detector, the gamma background is increased. Substantial background also comes from neutron scattering and capture in the lens itself, its mounting and positioning structure, and the surrounding shielding. Based on these measurements, a new neutron lens has been designed and constructed. Its installation was coordinated with a complete reconstruction of the prompt-gamma spectrometer in conjunction with the recent installation of a new liquid-H{sub 2} cold source at the NIST research reactor. To improve the signal-to-background ratio at the focal spot, a bent bundle of 3997 lead-glass fibers directs the neutrons to a focal spot 20 mm below the bottom edge of the incident beam. A motorized translation stage allows the lens to be remotely inserted into the neutron beam and removed when not needed.

Lindstrom, R.M.; Chen-Mayer, H.H. [National Inst. of Standards and Technology, Gaithersburg, MD (United States); Sharov, V.A. [X-Ray Optical Systems, Inc., Albany, NY (United States)] [and others

1996-12-31

442

Measurement and calculation of the fast-neutron and photon spectra from the core boundary to the biological shielding in the WWER-1000 reactor model.  

PubMed

The fast-neutron and photon space-energy distributions have been measured in an axially (1.25 m active height) and azimuthally (60 degree symmetry sector) shortened model of the WWER-1000 reactor assembled in the LR-0 experimental reactor. The space-energy d