Science.gov

Sample records for activation neutron spectra

  1. Neutron Unfolding Code System for Calculating Neutron Flux Spectra from Activation Data of Dosimeter Foils.

    1982-04-30

    Version 00 As a part of the measurement and analysis plan for the Dosimetry Experiment at the "JOYO" experimental fast reactor, neutron flux spectral analysis is performed using the NEUPAC (Neutron Unfolding Code Package) code system. NEUPAC calculates the neutron flux spectra and other integral quantities from the activation data of the dosimeter foils.

  2. Neutron Flux Spectra Determination by Multiple Foil Activation - Iterative Method.

    1994-07-08

    Version 00 Neutron energy spectra are determined by an analysis of experimental activation detector data. As with the original CCC-112/SAND-II program, which was developed at Air Force Weapons Laboratory, this code system consists of four modules, CSTAPE, SLACTS, SLATPE, and SANDII. The first three modules pre-process the dosimetry cross sections and the trial function spectrum library. The last module, SANDII, actually performs the iterative spectrum characterization.

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

    PubMed

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

    2004-01-01

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

  4. Evaluation of Am-Li neutron spectra data for active well type neutron multiplicity measurements of uranium

    NASA Astrophysics Data System (ADS)

    Goddard, Braden; Croft, Stephen; Lousteau, Angela; Peerani, Paolo

    2016-09-01

    Safeguarding nuclear material is an important and challenging task for the international community. One particular safeguards technique commonly used for uranium assay is active neutron correlation counting. This technique involves irradiating unused uranium with (α, n) neutrons from an Am-Li source and recording the resultant neutron pulse signal which includes induced fission neutrons. Although this non-destructive technique is widely employed in safeguards applications, the neutron energy spectra from an Am-Li sources is not well known. Several measurements over the past few decades have been made to characterize this spectrum; however, little work has been done comparing the measured and theoretical spectra of various Am-Li sources to each other. This paper examines fourteen different Am-Li spectra, focusing on how these spectra affect simulated neutron multiplicity results using the code Monte Carlo N-Particle eXtended (MCNPX). Two measurement and simulation campaigns were completed using Active Well Coincidence Counter (AWCC) detectors and uranium standards of varying enrichment. The results of this work indicate that for standard AWCC measurements, the fourteen Am-Li spectra produce similar doubles and triples count rates. The singles count rates varied by as much as 20% between the different spectra, although they are usually not used in quantitative analysis, being dominated by scattering which is highly dependent on item placement.

  5. Evaluation of Am–Li neutron spectra data for active well type neutron multiplicity measurements of uranium

    DOE PAGES

    Goddard, Braden; Croft, Stephen; Lousteau, Angela; Peerani, Paolo

    2016-05-25

    Safeguarding nuclear material is an important and challenging task for the international community. One particular safeguards technique commonly used for uranium assay is active neutron correlation counting. This technique involves irradiating unused uranium with ( α,n) neutrons from an Am-Li source and recording the resultant neutron pulse signal which includes induced fission neutrons. Although this non-destructive technique is widely employed in safeguards applications, the neutron energy spectra from an Am-Li sources is not well known. Several measurements over the past few decades have been made to characterize this spectrum; however, little work has been done comparing the measured spectra ofmore » various Am-Li sources to each other. This paper examines fourteen different Am-Li spectra, focusing on how these spectra affect simulated neutron multiplicity results using the code Monte Carlo N-Particle eXtended (MCNPX). Two measurement and simulation campaigns were completed using Active Well Coincidence Counter (AWCC) detectors and uranium standards of varying enrichment. The results of this work indicate that for standard AWCC measurements, the fourteen Am-Li spectra produce similar doubles and triples count rates. Finally, the singles count rates varied by as much as 20% between the different spectra, although they are usually not used in quantitative analysis.« less

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

    SciTech Connect

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

    1987-12-01

    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.

  7. ANDI-03: a genetic algorithm tool for the analysis of activation detector data to unfold high-energy neutron spectra.

    PubMed

    Mukherjee, Bhaskar

    2004-01-01

    The thresholds of (n,xn) reactions in various activation detectors are commonly used to unfold the neutron spectra covering a broad energy span, i.e. from thermal to several hundreds of MeV. The saturation activities of the daughter nuclides (i.e. reaction products) serve as the input data of specific spectra unfolding codes, such as SAND-II and LOUHI-83. However, most spectra unfolding codes, including the above, require an a priori (guess) spectrum to starting up the unfolding procedure of an unknown spectrum. The accuracy and exactness of the resulting spectrum primarily depends on the subjectively chosen guess spectrum. On the other hand, the Genetic Algorithm (GA)-based spectra unfolding technique ANDI-03 (Activation-detector Neutron DIfferentiation) presented in this report does not require a specific starting parameter. The GA is a robust problem-solving tool, which emulates the Darwinian Theory of Evolution prevailing in the realm of biological world and is ideally suited to optimise complex objective functions globally in a large multidimensional solution space. The activation data of the 27Al(n,alpha)24Na, 116In(n,gamma)116mIn, 12C(n,2n)11C and 209Bi(n,xn)(210-x)Bi reactions recorded at the high-energy neutron field of the ISIS Spallation source (Rutherford Appleton Laboratory, UK) was obtained from literature and by applying the ANDI-03 GA tool, these data were used to unfold the neutron spectra. The total neutron fluence derived from the neutron spectrum unfolded using GA technique (ANDI-03) agreed within +/-6.9% (at shield top level) and +/-27.2% (behind a 60 cm thick concrete shield) with the same unfolded with the SAND-II code.

  8. ANDI-03: a genetic algorithm tool for the analysis of activation detector data to unfold high-energy neutron spectra.

    PubMed

    Mukherjee, Bhaskar

    2004-01-01

    The thresholds of (n,xn) reactions in various activation detectors are commonly used to unfold the neutron spectra covering a broad energy span, i.e. from thermal to several hundreds of MeV. The saturation activities of the daughter nuclides (i.e. reaction products) serve as the input data of specific spectra unfolding codes, such as SAND-II and LOUHI-83. However, most spectra unfolding codes, including the above, require an a priori (guess) spectrum to starting up the unfolding procedure of an unknown spectrum. The accuracy and exactness of the resulting spectrum primarily depends on the subjectively chosen guess spectrum. On the other hand, the Genetic Algorithm (GA)-based spectra unfolding technique ANDI-03 (Activation-detector Neutron DIfferentiation) presented in this report does not require a specific starting parameter. The GA is a robust problem-solving tool, which emulates the Darwinian Theory of Evolution prevailing in the realm of biological world and is ideally suited to optimise complex objective functions globally in a large multidimensional solution space. The activation data of the 27Al(n,alpha)24Na, 116In(n,gamma)116mIn, 12C(n,2n)11C and 209Bi(n,xn)(210-x)Bi reactions recorded at the high-energy neutron field of the ISIS Spallation source (Rutherford Appleton Laboratory, UK) was obtained from literature and by applying the ANDI-03 GA tool, these data were used to unfold the neutron spectra. The total neutron fluence derived from the neutron spectrum unfolded using GA technique (ANDI-03) agreed within +/-6.9% (at shield top level) and +/-27.2% (behind a 60 cm thick concrete shield) with the same unfolded with the SAND-II code. PMID:15353654

  9. Measuring neutron spectra in radiotherapy using the nested neutron spectrometer

    SciTech Connect

    Maglieri, Robert Evans, Michael; Seuntjens, Jan; Kildea, John; Licea, Angel

    2015-11-15

    Purpose: Out-of-field neutron doses resulting from photonuclear interactions in the head of a linear accelerator pose an iatrogenic risk to patients and an occupational risk to personnel during radiotherapy. To quantify neutron production, in-room measurements have traditionally been carried out using Bonner sphere systems (BSS) with activation foils and TLDs. In this work, a recently developed active detector, the nested neutron spectrometer (NNS), was tested in radiotherapy bunkers. Methods: The NNS is designed for easy handling and is more practical than the traditional BSS. Operated in current-mode, the problem of pulse pileup due to high dose-rates is overcome by measuring current, similar to an ionization chamber. In a bunker housing a Varian Clinac 21EX, the performance of the NNS was evaluated in terms of reproducibility, linearity, and dose-rate effects. Using a custom maximum-likelihood expectation–maximization algorithm, measured neutron spectra at various locations inside the bunker were then compared to Monte Carlo simulations of an identical setup. In terms of dose, neutron ambient dose equivalents were calculated from the measured spectra and compared to bubble detector neutron dose equivalent measurements. Results: The NNS-measured spectra for neutrons at various locations in a treatment room were found to be consistent with expectations for both relative shape and absolute magnitude. Neutron fluence-rate decreased with distance from the source and the shape of the spectrum changed from a dominant fast neutron peak near the Linac head to a dominant thermal neutron peak in the moderating conditions of the maze. Monte Carlo data and NNS-measured spectra agreed within 30% at all locations except in the maze where the deviation was a maximum of 40%. Neutron ambient dose equivalents calculated from the authors’ measured spectra were consistent (one standard deviation) with bubble detector measurements in the treatment room. Conclusions: The NNS may

  10. Self-Shielding Correlation of Foil Activation Neutron Spectra Analysis by SAND-II.

    2008-11-21

    Version 00 SELFS-3 corrects for the influence of the self-shielding effect in neutron spectrum determinations by means of the multifoil activation method. It is used in combination with the SAND-II program for unfolding the responses of an irradiated set of activation detectors in 620 groups. The program SELFS can calculate a corrected 620 group cross section data set for specified reactions used in the SAND-II library, and for specified foil thicknesses. This procedure requires nomore » additional assumption on the shape of the neutron spectrum and on other experimental conditions, but only some foil characteristics (reaction type, material composition, foil thickness). Application of this procedure is possible when multigroup unfolding programs are used with suitably small energy intervals. This code system was developed in the 1970’s at Reactor Centrum Nederland, Petten, The Netherlands, and was contributed to RSICC through the NEA Data Bank. No changes were made to the package when it was released by RSICC in 2008. Modifications will be required to run SELFS-3 on current computer systems.« less

  11. Mechanical approach to the neutrons spectra collimation and detection

    SciTech Connect

    Sadeghi, H.; Roshan, M. V.

    2014-11-15

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

  12. Mechanical approach to the neutrons spectra collimation and detection.

    PubMed

    Sadeghi, H; Roshan, M V

    2014-11-01

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

  13. Gravitational effects on planetary neutron flux spectra

    NASA Astrophysics Data System (ADS)

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

    1989-01-01

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

  14. Prompt fission neutron spectra of actinides

    DOE PAGES

    Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; Kornilov, N. V.; Lestone, J. P.; Litaize, O.; Morillon, B.; Neudecker, D.; Oberstedt, S.; Ohsawa, T.; et al

    2016-01-06

    Here, the energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) "Evaluation of Prompt Fission Neutron Spectra of Actinides" was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei.

  15. Interpreting inertial fusion neutron spectra

    NASA Astrophysics Data System (ADS)

    Munro, David H.

    2016-03-01

    A burning laser fusion plasma produces a neutron spectrum first described by Brysk (1973 Plasma Phys. Control. Fusion 15 611). This and more recent work deals with the spectrum produced by a single fluid element. The distribution of temperatures and velocities in multiple fluid elements combine in any real spectrum; we derive formulas for how the neutron spectrum averages these contributions. The single element momentum spectrum is accurately Gaussian, but the multi-element spectrum exhibits higher moments. In particular, the skew and kurtosis are likely to be large enough to measure. Even the single fluid element spectrum may exhibit measurable directional anisotropy, so that instruments with different lines of sight should see different yields, mean velocities, mean temperatures, and higher moments. Finally, we briefly discuss how scattering in the imploded core modifies the neutron spectrum by changing the relative weighting of fuel regions with different temperatures and velocities.

  16. Neutron Spectra in a 15 MV LINAC

    SciTech Connect

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

    2010-12-07

    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.

  17. Uncertainty Quantification on Prompt Fission Neutrons Spectra

    SciTech Connect

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

    2008-12-15

    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.

  18. Dose spectra from energetic particles and neutrons

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  19. Slow neutron leakage spectra from spallation neutron sources

    SciTech Connect

    Das, S G; Carpenter, J M; Prael, R E

    1980-02-01

    An efficient technique is described for Monte Carlo simulation of neutron beam spectra from target-moderator-reflector assemblies typical of pulsed spallation neutron sources. The technique involves the scoring of the transport-theoretical probability that a neutron will emerge from the moderator surface in the direction of interest, at each collision. An angle-biasing probability is also introduced which further enhances efficiency in simple problems. These modifications were introduced into the VIM low energy neutron transport code, representing the spatial and energy distributions of the source neutrons approximately as those of evaporation neutrons generated through the spallation process by protons of various energies. The intensity of slow neutrons leaking from various reflected moderators was studied for various neutron source arrangements. These include computations relating to early measurements on a mockup-assembly, a brief survey of moderator materials and sizes, and a survey of the effects of varying source and moderator configurations with a practical, liquid metal cooled uranium source Wing and slab, i.e., tangential and radial moderator arrangements, and Be vs CH/sub 2/ reflectors are compared. Results are also presented for several complicated geometries which more closely represent realistic arrangements for a practical source, and for a subcritical fission multiplier such as might be driven by an electron linac. An adaptation of the code was developed to enable time dependent calculations, and investigated the effects of the reflector, decoupling and void liner materials on the pulse shape.

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

    SciTech Connect

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

    2010-12-07

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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.

  2. Prompt Fission Neutron Spectra of Actinides

    SciTech Connect

    Capote, R; Chen, Y J; Hambsch, F J; Kornilov, N V; Lestone, J P; Litaize, O; Morillon, B; Neudecker, D; Oberstedt, S; Ohsawa, T; Smith, D. L.

    2016-01-01

    The energy spectrum of prompt neutrons emitted in fission (PFNS) plays a very important role in nuclear science and technology. A Coordinated Research Project (CRP) “Evaluation of Prompt Fission Neutron Spectra of Actinides”was established by the IAEA Nuclear Data Section in 2009, with the major goal to produce new PFNS evaluations with uncertainties for actinide nuclei. The following technical areas were addressed: (i) experiments and uncertainty quantification (UQ): New data for neutron-induced fission of 233U, 235U, 238U, and 239Pu have been measured, and older data have been compiled and reassessed. There is evidence from the experimental work of this CRP that a very small percentage of neutrons emitted in fission are actually scission neutrons; (ii) modeling: The Los Alamos model (LAM) continues to be the workhorse for PFNS evaluations. Monte Carlo models have been developed that describe the fission phenomena microscopically, but further development is needed to produce PFNS evaluations meeting the uncertainty targets; (iii) evaluation methodologies: PFNS evaluations rely on the use of the least-squares techniques for merging experimental and model data. Considerable insight was achieved on how to deal with the problem of too small uncertainties in PFNS evaluations. The importance of considering that all experimental PFNS data are “shape” data was stressed; (iv) PFNS evaluations: New evaluations, including covariance data, were generated for major actinides including 1) non-model GMA evaluations of the 235U(nth,f), 239Pu(nth,f), and 233U(nth,f) PFNS based exclusively on experimental data (0.02 ≤ E ≤ 10 MeV), which resulted in PFNS average energies E of 2.00±0.01, 2.073±0.010, and 2.030±0.013 MeV, respectively; 2) LAM evaluations of neutron-induced fission spectra on uranium and plutonium targets with improved UQ for incident energies from thermal up to 30 MeV; and 3) Point-by-Point calculations for 232Th, 234U and 237Np targets; and (v) data

  3. Arsenic activation neutron detector

    DOEpatents

    Jacobs, E.L.

    1980-01-28

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

  4. Arsenic activation neutron detector

    DOEpatents

    Jacobs, Eddy L.

    1981-01-01

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

  5. Neutron activation analysis system

    DOEpatents

    Taylor, M.C.; Rhodes, J.R.

    1973-12-25

    A neutron activation analysis system for monitoring a generally fluid media, such as slurries, solutions, and fluidized powders, including two separate conduit loops for circulating fluid samples within the range of radiation sources and detectors is described. Associated with the first loop is a neutron source that emits s high flux of slow and thermal neutrons. The second loop employs a fast neutron source, the flux from which is substantially free of thermal neutrons. Adjacent to both loops are gamma counters for spectrographic determination of the fluid constituents. Other gsmma sources and detectors are arranged across a portion of each loop for deterMining the fluid density. (Official Gazette)

  6. Fission neutron spectra measurements at LANSCE - status and plans

    SciTech Connect

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

    2009-01-01

    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.

  7. Calculating fusion neutron energy spectra from arbitrary reactant distributions

    NASA Astrophysics Data System (ADS)

    Eriksson, J.; Conroy, S.; Andersson Sundén, E.; Hellesen, C.

    2016-02-01

    The Directional Relativistic Spectrum Simulator (DRESS) code can perform Monte-Carlo calculations of reaction product spectra from arbitrary reactant distributions, using fully relativistic kinematics. The code is set up to calculate energy spectra from neutrons and alpha particles produced in the D(d, n)3He and T(d, n)4He fusion reactions, but any two-body reaction can be simulated by including the corresponding cross section. The code has been thoroughly tested. The kinematics calculations have been benchmarked against the kinematics module of the ROOT Data Analysis Framework. Calculated neutron energy spectra have been validated against tabulated fusion reactivities and against an exact analytical expression for the thermonuclear fusion neutron spectrum, with good agreement. The DRESS code will be used as the core of a detailed synthetic diagnostic framework for neutron measurements at the JET and MAST tokamaks.

  8. Sci—Fri PM: Dosimetry—02: A Nested Neutron Spectrometer to Measure Neutron Spectra in Radiotherapy

    SciTech Connect

    Maglieri, R; Seuntjens, J; Kildea, J; Licea, A

    2014-08-15

    During high-energy radiotherapy treatments, neutrons are produced in the head of the linac through photonuclear interactions. This has been a concern for many years as photoneutrons contribute to the accepted, yet unwanted, out-of-field doses that pose an iatrogenic risk to patients and an occupational risk to personnel. Presently, in-room neutron measurements are difficult and time-consuming and have traditionally been carried out using Bonner spheres with activation foils and TLDs. In this work, a new detector, the Nested Neutron Spectrometer (NNS) is tested for use in radiotherapy bunkers. The NNS is designed for easy handling and is more practical than the traditional Bonner spheres. The NNS, operated in current mode, was used to measure the dose equivalent, average energy and energy spectrum at several positions in a radiotherapy bunker. The average energy and spectra were compared to Monte Carlo simulations while the dose equivalent was compared to bubble detector measurements. The average energies, as measured by the NNS and Monte Carlo simulations, differed by approximately 30% across the bunker. Measurements of the dose equivalent using the NNS and the bubble detectors agreed within 50% in the maze and less than 10% close to the linac head. Apart from some discrepancies at thermal energies, we also found reasonable agreement between NNS-measured and Monte Carlo-simulated spectra at a number of locations within our radiotherapy bunker. Our results demonstrate that the NNS is a suitable detector to be used in high dose-rate radiotherapy environments.

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

    SciTech Connect

    James W. Sterbentz

    2008-05-01

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

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

    PubMed

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

    2015-05-01

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

  11. Neutron activation analysis of a penny

    NASA Astrophysics Data System (ADS)

    Stevens, Richard E.

    2000-04-01

    Neutron activation analysis has been used for many years as an analysis tool and as an educational tool to teach students about nuclear properties. This article presents an exercise in the neutron activation analysis of a penny which, due to the simplicity of the resulting gamma-ray spectra, is appropriate for general physics classes. Students express a great deal of interest both in seeing the reactor in use as well as determining the composition of something that is familiar to them.

  12. High-Energy Neutron Spectra and Flux Measurements Below Ground

    NASA Astrophysics Data System (ADS)

    Roecker, Caleb; Bernstein, Adam; Marleau, Peter; Vetter, Kai

    2016-03-01

    High-energy neutrons are a ubiquitous and often poorly measured background. Below ground, these neutrons could potentially interfere with antineutrino based reactor monitoring experiments as well as other rare-event neutral particle detectors. We have designed and constructed a transportable fast neutron detection system for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The spectrometer uses a multiplicity technique in order to have a higher effective area than traditional transportable high-energy neutron spectrometers. Transportability ensures a common detector-related systematic bias for future measurements. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. A high-energy neutron may interact in the lead producing many secondary neutrons. The detector records the correlated secondary neutron multiplicity. Over many events, the response can be used to infer the incident neutron energy spectrum and flux. As a validation of the detector response, surface measurements have been performed; results confirm agreement with previous experiments. Below ground measurements have been performed at 3 depths (380, 600, and 1450 m.w.e.); results from these measurements will be presented.

  13. Neutron emission profiles and energy spectra measurements at JET

    SciTech Connect

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

    2014-08-21

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

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

    NASA Astrophysics Data System (ADS)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2000-10-01

    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 5 min by remote control under a continuous reactor operation. This feature is advantageous not only to medical science such as NCT, but also to the other research fields such as physics, engineering, biology, etc. The performance of the updated facility as a neutron irradiation field with variable energy spectra, was characterized. Thermal neutron flux, cadmium ratio, gamma-ray dose rate, etc., at the normal irradiation position for various irradiation modes were determined, mainly on the basis of the measurement using gold activation foils and thermo-luminescent dosimeters (TLDs). The emphasis was on the performance of the new neutron energy spectrum shifter and cadmium thermal neutron filter, that control the mixing ratio of thermal and epi-thermal neutrons, through the change in the heavy water thickness of the spectrum shifter and the aperture size of the cadmium filter. The evaluation of neutron energy spectra at the normal irradiation position was also performed for three representative irradiation modes, in which the neutron intensities are largest of all the irradiation modes. In addition, the irradiation characteristics of two irradiation devices, namely the Irradiation Rail Device and the Remote Patient Carrier, which were updated concurrently with the facility update, were evaluated.

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

    PubMed

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

    2009-07-01

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

  16. X-ray spectra from convective photospheres of neutron stars

    SciTech Connect

    Zavlin, V.E.; Pavlov, G.G. |; Shibanov, Yu.A.; Rogers, F.J.; Iglesias, C.A.

    1996-01-17

    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.

  17. Characterization of neutron yield and x-ray spectra of a High Flux Neutron Generator (HFNG)

    NASA Astrophysics Data System (ADS)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

    The High Flux Neutron Generator (HFNG) is a DD plasma-based source, with a self-loading target intended for fundamental science and engineering applications, including 40 Ar/39 Ar geochronology, neutron cross section measurements, and radiation hardness testing of electronics. Our first estimate of the neutron yield, based on the population of the 4.486 hour 115 In isomer gave a neutron yield of the order 108 n/sec; optimization is ongoing to achieve the design target of 1011 n/sec. Preliminary x-ray spectra showed prominent energy peaks which are likely due to atomic line-emission from back-streaming electrons accelerated up to 100 keV impinging on various components of the HFNG chamber. Our x-ray and neutron diagnostics will aid us as we continue to evolve the design to suppress back-streaming electrons, necessary to achieve higher plasma beam currents, and thus higher neutron flux. This talk will focus on the characterization of the neutron yield and x-ray spectra during our tests. A collimation system is being installed near one of the chamber ports for improved observation of the x-ray spectra. This work is supported by NSF Grant No. EAR-0960138, U.S. DOE LBNL Contract No. DE-AC02-05CH11231, U.S. DOE LLNL Contract No. DE-AC52-07NA27344, and the UC Office of the President Award 12-LR-238745.

  18. European Neutron Activation System.

    2013-01-11

    Version 03 EASY-2010 (European Activation System) consists of a wide range of codes, data and documentation all aimed at satisfying the objective of calculating the response of materials irradiated in a neutron flux. The main difference from the previous version is the upper energy limit, which has increased from 20 to 60 MeV. It is designed to investigate both fusion devices and accelerator based materials test facilities that will act as intense sources of high-energymore » neutrons causing significant activation of the surrounding materials. The very general nature of the calculational method and the data libraries means that it is applicable (with some reservations) to all situations (e.g. fission reactors or neutron sources) where materials are exposed to neutrons below 60 MeV. EASY can be divided into two parts: data and code development tools and user tools and data. The former are required to develop the latter, but EASY users only need to be able to use the inventory code FISPACT and be aware of the contents of the EAF library (the data source). The complete EASY package contains the FISPACT-2007 inventory code, the EAF-2003, EAF-2005, EAF-2007 and EAF-2010 libraries, and the EASY User Interface for the Window version. The activation package EASY-2010 is the result of significant development to extend the upper energy range from 20 to 60 MeV so that it is capable of being used for IFMIF calculations. The EAF-2010 library contains 66,256 reactions, almost five times more than in EAF-2003 (12,617). Deuteron-induced and proton-induced cross section libraries are also included, and can be used with EASY to enable calculations of the activation due to deuterons and proton [2].« less

  19. Physical basis for prompt-neutron activation analysis

    SciTech Connect

    Chrien, R.E.

    1982-01-01

    The technique called prompt ..gamma..-ray neutron activation analysis has been applied to rapid materials analysis. The radiation following the neutron radiation capture is prompt in the sense that the nuclear decay time is on the order of 10/sup -15/ second, and thus the technique is not strictly activation, but should be called radiation neutron capture spectroscopy or neutron capture ..gamma..-ray spectroscopy. This paper reviews the following: sources and detectors, theory of radiative capture, nonstatistical capture, giant dipole resonance, fast neutron capture, and thermal neutron capture ..gamma..-ray spectra. 14 figures.

  20. Variable spectra of active galaxies

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1988-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

  3. Neutron activation for ITER

    SciTech Connect

    Barnes, C.W.; Loughlin, M.J.; Nishitani, Takeo

    1996-04-29

    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.

  4. X-ray spectra from convective photospheres of neutron stars

    NASA Technical Reports Server (NTRS)

    Zavlin, V. E.; Pavlov, G. G.; Shibanov, Yu. A.; Rogers, F. J.; Iglesias, C. A.

    1996-01-01

    The preliminary results from the simulation of convective photospheres of neutron stars are presented. It is shown that in photospheres composed of light elements, convection arises at relatively low effective temperatures of between 3 x 10(exp 4) and 5 x 10(exp 4) K, whereas, in the case of iron composition, it arises at temperatures of less than or equal to 3 x 10(exp 5) K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. It is concluded that depth should be taken into account for the correct interpretation of extreme ultraviolet/soft X-ray observations of the thermal radiation from neutron stars.

  5. Absorption Features in Spectra of Magnetized Neutron Stars

    SciTech Connect

    Suleimanov, V.; Hambaryan, V.; Neuhaeuser, R.; Potekhin, A. Y.; Pavlov, G. G.; Adelsberg, M. van; Werner, K.

    2011-09-21

    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.

  6. Spectra of solar proton ground level events using neutron monitor and neutron moderated detector recordings

    NASA Technical Reports Server (NTRS)

    Stoker, P. H.

    1985-01-01

    Recordings on relativistic solar flare protons observed at Sanae, Antarctic, show that the percentage increase in counting rates of the neutron moderated detector (4NMD) is larger than the percentage increase in counting rates of the 3NM64 neutron monitor. These relative increases are described by solar proton differential spectra j sub s(P) = AP(beta). The power beta is determined for each event and the hardnesses of the temporal variations of beta, found for the ground level events (GLE) of 7 May, 1978 and 22 November, 1977.

  7. Neutron Activation Analysis: Techniques and Applications

    NASA Astrophysics Data System (ADS)

    MacLellan, Ryan

    2011-04-01

    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.

  8. Neutron Activation Analysis: Techniques and Applications

    SciTech Connect

    MacLellan, Ryan

    2011-04-27

    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.

  9. U, Np, Pu and Am Prompt Fission Neutron Spectra

    SciTech Connect

    Maslov, Vladimir M.

    2008-05-12

    Prompt fission neutron spectra (PFNS) components due to soft and hard pre-fission neutrons are revealed in PFNS data of {sup 232}Th(n,F), {sup 238}U(n,F), {sup 235}U(n,F) and {sup 239}Pu(n,F) reactions for E{sub n}{<=}20 MeV. Average energies of these PFNS are systematically shifted to higher values, so that Th fission fragments look least heated, while those of Pu--most heated. The average energy is correlated with the emissive fission chances contributions to the observed fission cross sections. The predicted contribution of (n,xnf) neutrons is most pronounced in case of {sup 232}Th(n,F) reaction. The approach, based on the consistent description of {sup 237}Np(n,F), {sup 237}Np(n,2n){sup 236s}Np and {sup 241}Am(n,F), {sup 241}Am(n,2n) is used to predict the PFNS of the {sup 237}Np(n,F) and {sup 241}Am(n,F) reactions.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    SciTech Connect

    Kroc, T.K.; /Fermilab

    2009-10-01

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

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

    PubMed

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

    2012-08-01

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

  13. Model Atmospheres and X-Ray Spectra of Bursting Neutron Stars: Hydrogen-Helium Comptonized Spectra

    NASA Astrophysics Data System (ADS)

    Madej, J.; Joss, P. C.; Różańska, A.

    2004-02-01

    Compton scattering plays a crucial role in determining the structure of the atmosphere of an X-ray burster and its theoretical spectrum. Our paper presents a description of the plane-parallel model atmosphere of a very hot neutron star and its theoretical flux spectrum of outgoing radiation. Our model equations take into account all bound-free and free-free monochromatic opacities relevant to hydrogen-helium chemical composition and take into account the effects of Compton scattering of radiation in thermal plasma with fully relativistic thermal velocities. We use Compton scattering terms in the equation of transfer, which precisely describe photon-electron energy and momentum exchange for photons with initial energies exceeding the electron rest mass of 511 keV. Model atmosphere equations are solved with the variable Eddington factors technique. The grid of H-He model atmospheres and flux spectra is computed on a dense mesh of 107K<=Teff<=3×107K and a surface gravity of logg. In many cases, the assumed logg approached the critical gravity loggcr, i.e., the Eddington limit. We confirm that H-He spectra of X-ray bursters deviate from blackbody spectra and discuss their shapes. The table of color to effective temperature ratios shows that theoretical values of Tc/Teff do not exceed 1.9 in H-He atmospheres in hydrostatic and radiative equilibrium.

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

    SciTech Connect

    Kawano, Toshihiko; Moller, Peter; Wilson, William B

    2008-01-01

    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.

  15. Neutron activated switch

    DOEpatents

    Barton, David M.

    1991-01-01

    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.

  16. Improved Fission Neutron Data Base for Active Interrogation of Actinides

    SciTech Connect

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

    2013-11-06

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

  17. A new fission chamber dedicated to Prompt Fission Neutron Spectra measurements

    NASA Astrophysics Data System (ADS)

    Taieb, J.; Laurent, B.; Bélier, G.; Sardet, A.; Varignon, C.

    2016-10-01

    New fission chambers dedicated to Prompt Fission Neutron Spectra measurements with the time-of-flight technique have been developed. The actinide mass embedded in the chamber was maximized, while the alpha-fission discrimination and the time resolution were optimized. Moreover, to reduce the neutron background and spectra distortions, neutron scattering with the materials were minimized by the choice of material and structure. These chambers were then tested and validated during tests and in-beam experiments.

  18. Enhanced NIF neutron activation diagnostics

    SciTech Connect

    Yeamans, C. B.; Bleuel, D. L.; Bernstein, L. A.

    2012-10-15

    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.

  19. Enhanced NIF neutron activation diagnostics.

    PubMed

    Yeamans, C B; Bleuel, D L; Bernstein, L A

    2012-10-01

    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 (89)Zr/(89 m)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.

  20. Enhanced NIF neutron activation diagnosticsa)

    NASA Astrophysics Data System (ADS)

    Yeamans, C. B.; Bleuel, D. L.; Bernstein, L. A.

    2012-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  2. Neutron and gamma dose and spectra measurements on the Little Boy replica

    SciTech Connect

    Hoots, S.; Wadsworth, D.

    1984-06-01

    The radiation-measurement team of the Weapons Engineering Division at Lawrence Livermore National Laboratory (LLNL) measured neutron and gamma dose and spectra on the Little Boy replica at Los Alamos National Laboratory (LANL) in April 1983. This assembly is a replica of the gun-type atomic bomb exploded over Hiroshima in 1945. These measurements support the National Academy of Sciences Program to reassess the radiation doses due to atomic bomb explosions in Japan. Specifically, the following types of information were important: neutron spectra as a function of geometry, gamma to neutron dose ratios out to 1.5 km, and neutron attenuation in the atmosphere. We measured neutron and gamma dose/fission from close-in to a kilometer out, and neutron and gamma spectra at 90 and 30/sup 0/ close-in. This paper describes these measurements and the results. 12 references, 13 figures, 5 tables.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  4. The dynamic method for time-of-flight measurement of thermal neutron spectra from pulsed sources

    NASA Astrophysics Data System (ADS)

    Pepyolyshev, Yu. N.; Chukiyaev, S. V.; Tulaev, A. B.; Bobrakov, V. F.

    1995-02-01

    A time-of-flight method for measurement of thermal neutron spectra in pulsed neutron sources with an efficiency more than 10 5 times higher than the standard method is described. The main problems associated with the electric current technique for time-of-flight spectra measurement are examined. The methodical errors, problems of special neutron detector design and other questions are discussed. Some experimental results for spectra from the surfaces of water and solid methane moderators obtained at the IBR-2 pulsed reactor (Dubna, Russia) are presented.

  5. Measurement of low to middle energy neutron spectra in aircraft at aviation altitude

    NASA Astrophysics Data System (ADS)

    Yajima, Kazuaki; Goka, Tateo; Yasuda, Hiroshi; Takada, Masashi; Nakamura, Takashi

    Neutron energy spectra ranging from thermal to 10 MeV were measured at aviation altitude (9.1-11 km) with Bonner-Boll-type neutron spectral measurement system named BBND which has been developed for use on board the International Space Station (ISS) by NASDA (currently JAXA). The BBND was set and manipulated in a business jet chartered for observation experiments, and 4 flights were carried out around the Nagoya Airport, which located in the middle of Japan. It is found that the variation of neutron flux on the flight traced the altitude variation. The estimated energy spectra will be incorporated into the determination of whole energy spectra of cosmic neutrons from thermal to hundreds MeV using the prototype neutron monitor based on the phoswich-type detector.

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

    PubMed

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

    2014-01-01

    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.

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

    PubMed

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

    2014-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Ján, Milčák; Michal, Košťál; Marie, Švadlenková; Michal, Koleška; Vojtěch, Rypar

    2014-11-01

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

  9. Gamma-ray spectra from neutron capture on /sup 87/Sr

    SciTech Connect

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

    1981-07-01

    The gamma-ray spectrum following neutron capture on /sup 87/Sr was measured at 3 neutron energies: E/sub n/ = thermal, 2 keV, and 24 keV. Gamma rays were detected in a three-crystal Ge(Li)-NaI-NaI pair spectrometer. Gamma-ray intensities deduced from these spectra by spectral unfolding are presented.

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

    SciTech Connect

    Duran, I.; Viererbl, L.; Lahodova, Z.; Sentkerestiova, J.; Bem, P.

    2010-10-15

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

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

    PubMed

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

    2010-10-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    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.

  13. SOURCES: a code for calculating (alpha,n), spontaneous fission, and delayed neutron sources and spectra.

    PubMed

    Wilson, W B; Perry, R T; Charlton, W S; Parish, T A; Shores, E F

    2005-01-01

    SOURCES is a computer code that determines neutron production rates and spectra from (alpha,n) reactions, spontaneous fission and delayed neutron emission owing to the decay of radionuclides in homogeneous media, interface problems and three-region interface problems. The code is also capable of calculating the neutron production rates due to (alpha,n) reactions induced by a monoenergetic beam of alpha particles incident on a slab of target material. The (alpha,n) spectra are calculated using an assumed isotropic angular distribution in the centre-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. Spontaneous fission sources and spectra are calculated with evaluated half-life, spontaneous fission branching and Watt spectrum parameters for 44 actinides. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code outputs the magnitude and spectra of the resultant neutron sources. It also provides an analysis of the contributions to that source by each nuclide in the problem. PMID:16381695

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  16. Measurement of Neutron Energy Spectra behind Shielding of a 120 GeV/c Hadron Facility

    SciTech Connect

    Nakao, N.; Rokni, S.H.; Vincke, H.; Khater, Hesham; Prinz, A.A.; Taniguchi, S.; Roesler, S.; Brugger, M.; Hagiwara, Masayuki; /Tohoku U.

    2005-12-14

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

  17. Neutron spectra from beam-target reactions in dense Z-pinches

    SciTech Connect

    Appelbe, B. Chittenden, J.

    2015-10-15

    The energy spectrum of neutrons emitted by a range of deuterium and deuterium-tritium Z-pinch devices is investigated computationally using a hybrid kinetic-MHD model. 3D MHD simulations are used to model the implosion, stagnation, and break-up of dense plasma focus devices at currents of 70 kA, 500 kA, and 2 MA and also a 15 MA gas puff. Instabilities in the MHD simulations generate large electric and magnetic fields, which accelerate ions during the stagnation and break-up phases. A kinetic model is used to calculate the trajectories of these ions and the neutron spectra produced due to the interaction of these ions with the background plasma. It is found that these beam-target neutron spectra are sensitive to the electric and magnetic fields at stagnation resulting in significant differences in the spectra emitted by each device. Most notably, magnetization of the accelerated ions causes the beam-target spectra to be isotropic for the gas puff simulations. It is also shown that beam-target spectra can have a peak intensity located at a lower energy than the peak intensity of a thermonuclear spectrum. A number of other differences in the shapes of beam-target and thermonuclear spectra are also observed for each device. Finally, significant differences between the shapes of beam-target DD and DT neutron spectra, due to differences in the reaction cross-sections, are illustrated.

  18. Measurement of cumulative-neutron and cumulative-proton spectra in 1-GeV proton-nucleus interactions

    SciTech Connect

    Baturin, V.N.; Vikhrov, V.V.; Makarov, M.M.; Nelyubin, V.V.; Naberezhnov, A.A.; Sulimov, V.V.; Uvarov, L.N.

    1982-11-20

    A comparative study has been made of the spectra of cumulative neutrons and protons produced at an angle of 114/sup 0/ in collisions of 1-GeV protons with /sup 9/Be and /sup 12/C nuclei. The slope parameters of the inclusive neutron spectra are similar to those of the proton spectra.

  19. Introducing Nuclear Data Evaluations of Prompt Fission Neutron Spectra

    SciTech Connect

    Neudecker, Denise

    2015-06-17

    Nuclear data evaluations provide recommended data sets for nuclear data applications such as reactor physics, stockpile stewardship or nuclear medicine. The evaluated data are often based on information from multiple experimental data sets and nuclear theory using statistical methods. Therefore, they are collaborative efforts of evaluators, theoreticians, experimentalists, benchmark experts, statisticians and application area scientists. In this talk, an introductions is given to the field of nuclear data evaluation at the specific example of a recent evaluation of the outgoing neutron energy spectrum emitted promptly after fission from 239Pu and induced by neutrons from thermal to 30 MeV.

  20. Neutron Activation Analysis of Water - A Review

    NASA Technical Reports Server (NTRS)

    Buchanan, John D.

    1971-01-01

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

  1. Broad-range neutron spectra identification in ultraintense laser interactions with carbon-deuterated plasma

    SciTech Connect

    Youssef, A.; Kodama, R.; Habara, H.; Tanaka, K.A.; Sentoku, Y.; Tampo, M.; Toyama, Y.

    2005-11-15

    Detailed neutron energy spectra produced from a CD2 target irradiated by a 450 fs, 20 J, 1053 nm laser at an intensity of 3x10{sup 18} W/cm{sup 2} have been studied. Wide-ranging neutron spectra were observed from two different observation angles 20 deg. and 70 deg. relative to the rear-side target normal. The experiment and numerically calculated spectra, by a three-dimensional Monte Carlo code, indicate that the range of the measured spectra is larger than that produced by the D(d,n){sup 3}He reaction. An interpretation for the measured spectra is introduced by considering the {sup 12}C(d,n){sup 13}N and D({sup 12}c,n){sup 13}N reactions. In addition, the study revealed that the neutron spectra produced by the D-C and C-D reactions can overlap that produced by the D-D reaction, and due to their high cross sections, comparing to the D-D reaction, both of them effectively participate in the neutron yield.

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

    SciTech Connect

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

    1980-08-01

    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.

  3. Prototype development for real-time monitoring of neutron energy spectra in space

    NASA Astrophysics Data System (ADS)

    Yasuda, Hiroshi; Takada, Masashi; Yajima, Kazuaki; Goka, Tateo; Sato, Tatsuhiko; Nakamura, Takashi

    A prototype instrument for real-time monitoring of neutron spectra in a spacecraft has been developed for ISS and future interplanetary missions to moon and Mars. The monitor consists of a phoswich-type scintillation detector with a photomultiplier and a data processing unit including an unfolding program running on Windows PC. The monitor detects the signals of high-energy neutrons(>5MeV) separately from other particles and can give a whole energy spectra by incorporating the low to middle energy spectra that are estimated by calculation or with another detector such as a Bonner-Ball neutron spectrometer. The prototype has been processed in calibrations at accelerator facilities in Japan and measurements on a business jet aircraft. Results of the observations were compared to model calculations using the PHITS code.

  4. 239Pu Prompt Fission Neutron Spectra Impact on a Set of Criticality and Experimental Reactor Benchmarks

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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

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

    SciTech Connect

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

    2009-04-15

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

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

    NASA Astrophysics Data System (ADS)

    Recktenwald, Geoff; Deinert, Mark

    2010-03-01

    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.

  7. Energy spectra of primary knock-on atoms under neutron irradiation

    NASA Astrophysics Data System (ADS)

    Gilbert, M. R.; Marian, J.; Sublet, J.-Ch.

    2015-12-01

    Materials subjected to neutron irradiation will suffer from a build-up of damage caused by the displacement cascades initiated by nuclear reactions. Previously, the main "measure" of this damage accumulation has been through the displacements per atom (dpa) index, which has known limitations. This paper describes a rigorous methodology to calculate the primary atomic recoil events (often called the primary knock-on atoms or PKAs) that lead to cascade damage events as a function of energy and recoiling species. A new processing code SPECTRA-PKA combines a neutron irradiation spectrum with nuclear recoil data obtained from the latest nuclear data libraries to produce PKA spectra for any material composition. Via examples of fusion relevant materials, it is shown that these PKA spectra can be complex, involving many different recoiling species, potentially differing in both proton and neutron number from the original target nuclei, including high energy recoils of light emitted particles such as α-particles and protons. The variations in PKA spectra as a function of time, neutron field, and material are explored. The application of PKA spectra to the quantification of radiation damage is exemplified using two approaches: the binary collision approximation and stochastic cluster dynamics, and the results from these different models are discussed and compared.

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

    SciTech Connect

    Roquemore, A.L.; Krasilnikov, A.V., Gorelenkov, N.N.

    1996-12-31

    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.

  9. Current Issues in Nuclear Data Evaluation Methodology: {sup 235}U Prompt Fission Neutron Spectra and Multiplicity for Thermal Neutrons

    SciTech Connect

    Trkov, A.; Capote, R.; Pronyaev, V.G.

    2015-01-15

    Issues in evaluation methodology of the prompt fission neutron spectra (PFNS) and neutron multiplicity for the thermal-neutron-induced fission of the {sup 235}U are discussed. The inconsistency between the experimental differential and integral data is addressed. By using differential data as ”shape data” good consistency was achieved between available sets of differential data. Integral dosimetry data have been used to define the PFNS slope at high outgoing neutron energies, where the quality of the differential data is poor. The inclusion into the fit of measured integral (spectrum-averaged) cross sections had a very small impact in the region where differential PFNS data are abundant and accurate, but removed the discrepancy with integral data at higher neutron emission energies. All experimental data are consistently fitted giving a PFNS average energy of 2.008 MeV. The impact on criticality prediction of the newly evaluated PFNS was tested. The highly enriched {sup 235}U solution assemblies with high leakage HEU-SOL-THERM-001 and HEU-SOL-THERM-009 benchmarks are the most sensitive to the PFNS. Criticality calculations for those solutions show a significant increase in reactivity if the average neutron energy of the fission neutrons is reduced from the ENDF/B-VI.5 value of 2.03 MeV. The proposed reduction of the PFNS average energy by 1.1% can be compensated by reducing the average number of neutrons per fission ν{sup ¯} at the thermal energy to the Gwin et al. measured value. The simple least-squares PFNS fit was confirmed by a more sophisticated combined fit of differential PFNS data for {sup 233,235}U, {sup 239}Pu and {sup 252}Cf nuclides with the generalised least-squares method using the GMA and GANDR codes.

  10. Development and testing of an active area neutron dosemeter.

    PubMed

    Brushwood, J M; Gow, J P D; Beeley, P A; Spyrou, N M

    2004-01-01

    This paper describes the design, development and testing of an active area neutron dosemeter (AAND). The classic moderator and central detector is retained but in AAND this arrangement is augmented by small thermal neutron detectors positioned within the moderating body. The outputs from these detectors are combined using an appropriately weighted linear superposition to fit both the ambient dose equivalent and the radiation weighting factor. Experimental verifications of both the modelled detector energy reponses and the overall AAND response are given. In the relatively soft D2O moderated 252Cf spectra, the AAND determined both the H*(10) and mean radiation weighting factor to better than +10%.

  11. Transport analysis of measured neutron energy spectra in a graphite stack with a collimated deuterium-tritium neutron beam

    SciTech Connect

    Tsechanski, A.; Ofek, R.; Goldfeld, A.; Shani, G.

    1989-02-01

    The Ben-Gurion University measurements of neutron energy spectra in a graphite stack, resulting from the scattering of 14.7-MeV neutrons streaming through a 6-cm-diam collimator in a 121-cm-thick paraffin wall, have been used as a benchmark for the compatability and accuracy of discrete ordinates, P/sub n/, and transport calculations and as a tool for fusion reactor neutronics. The transport analysis has been carried out with the DOT 4.2 discrete ordinates code and with cross sections processed with the NJOY code. Most of the parameters affecting the accuracy of the flux and L system scattering cross sections in the P/sub n/ approximation, the quadrature set employed, and the energy multigroup structure. First, a spectrum calculated with DOT 4.2, with a detector located on the axis of the system, was compared with a spectrum calculated with the MCNP Monte Carlo code, which was a preliminary verification of the DOT 4.2 results. Both calculated spectra were in good agreement. Next, the DOT 4.2 calculations were compared with the measured spectra. The comparison showed that the discrepancies between the measurements and the calculations increase as the distance between the detector and the system axis increases. This trend indicates that when the flux is determined mainly by multiple scatterings, a more divided multigroup structure should be employed.

  12. Distortion of pulse-height spectra of neutron capture gamma rays

    SciTech Connect

    Laptev, A.; Harada, H.; Nakamura, S.; Hori, J.; Igashira, M.; Ohsaki, T.; Ohgama, K.

    2006-03-13

    A distortion of pulse-height spectra of neutron capture {gamma}-rays caused by {gamma}-flash at neutron time-of-flight (TOF) measurement using a pulse neutron source has been investigated. Pulses from C6D6 detectors accumulated by flash-ADC were processed with both traditional analog-to-digital converter (ADC) and flash-ADC operational modes. A correction factor of {gamma}-ray yields, due to baseline shift, was quantitatively obtained by comparing the pulse-height spectra of the two data-collecting modes. The magnitude of the correction factor depends on the time, which passed after {gamma}-flash, and has complicated time dependence with a changing sign.

  13. ROTATIONAL CORRECTIONS TO NEUTRON-STAR RADIUS MEASUREMENTS FROM THERMAL SPECTRA

    SciTech Connect

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

    2015-01-20

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

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

    PubMed

    Rivard, Mark J; Zamenhof, Robert G

    2004-11-01

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

  15. Neutron spectrum measurements using proton recoil proportional counters: results of measurements of leakage spectra for the Little Boy assembly

    SciTech Connect

    Bennett, E.F.; Yule, T.J.

    1984-01-01

    Measurements of degraded fission-neutron spectra using recoil proportional counters are done routinely for studies involving fast reactor mockups. The same techniques are applicable to measurements of neutron spectra required for personnel dosimetry in fast neutron environments. A brief discussion of current applications of these methods together with the results of a measurement made on the LITTLE BOY assembly at Los Alamos are here described.

  16. Neutron spectra produced by 30, 35 and 40 MeV proton beams at KIRAMS MC-50 cyclotron with a thick beryllium target

    NASA Astrophysics Data System (ADS)

    Shin, Jae Won; Bak, Sang-In; Ham, Cheolmin; In, Eun Jin; Kim, Do Yoon; Min, Kyung Joo; Zhou, Yujie; Park, Tae-Sun; Hong, Seung-Woo; Bhoraskar, V. N.

    2015-10-01

    Neutrons over a wide range of energies are produced by bombarding a 1.05 cm thick beryllium target with protons of different energies delivered by the MC-50 Cyclotron of the Korea Institute of Radiological Medical Sciences (KIRAMS). The neutron flux Φ(En) versus neutron energy En, produced by protons of 30, 35, and 40 MeV energies, was obtained by using the GEANT4 code with a data-based hadronic model. For the experimental validation of the simulated neutron spectra, a number of pure aluminum and iron oxide samples were irradiated with the neutrons produced by 30, 35, and 40 MeV protons at 20 μA beam current. The gamma-ray activities of 24Na and 56Mn produced, respectively, through 27Al(n,α)24Na and 56Fe(n,p)56Mn reactions were measured by a HPGe detector. The neutron flux Φ(En) at each neutron energy from the simulation was multiplied with the evaluated cross-sections σ(En) of the respective nuclear reaction, and the summation ∑ Φ(En) σ(En) was calculated over the neutron spectrum for each proton energy of 30, 35, and 40 MeV. The measured gamma-ray activities of 24Na and 56Mn were found in good agreement with the activities estimated by using the summed values of ∑ Φ(En) σ(En) along with other parameters in a neutron activation method.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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 in the energy range from about 10 to the minus 8th to about 100,000 MeV at various depths in the atmosphere were calculated by 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 (Crand) mechanism is the source of the protons trapped in the inner radiation belt.

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

    SciTech Connect

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

    2013-07-14

    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.

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

    SciTech Connect

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

    1985-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1985-08-01

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

  1. MAGNETIC ENERGY SPECTRA IN SOLAR ACTIVE REGIONS

    SciTech Connect

    Abramenko, Valentyna; Yurchyshyn, Vasyl

    2010-09-01

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

  2. The LANL/LLNL Program to Measure Prompt Fission Neutron Spectra at LANSCE

    NASA Astrophysics Data System (ADS)

    Haight, Robert; Wu, Ching Yen; Lee, Hye Young; Taddeucci, Terry; Mosby, Shea; O'Donnell, John; Fotiades, Nikolaos; Devlin, Mattew; Ullmann, John; Nelson, Ronald; Wender, Stephen; White, Morgan; Solomon, Clell; Neudecker, Denise; Talou, Patrick; Rising, Michael; Bucher, Brian; Buckner, Matthew; Henderson, Roger

    2015-10-01

    Accurate data on the spectrum of neutrons emitted in neutron-induced fission are needed for applications and for a better understanding of the fission process. At LANSCE we have made important progress in understanding systematic uncertainties and in obtaining data for 235U on the low-energy part of the prompt fission neutron spectra (PFNS), a particularly difficult region because down-scattered neutrons go in this direction. We use a double time-of-flight technique to determine energies of incoming and outgoing neutrons. With data acquisition via waveform digitizers, accidental coincidences between fission chamber and neutron detector are measured to high statistical accuracy and then subtracted from measured events. Monte Carlo simulations with high performance computers have proven to be essential in the design to minimize neutron scattering and in calculating detector response. Results from one of three approaches to analyzing the data will be presented. This work is funded by the US Department of Energy, National Nuclear Security Administration and Office of Nuclear Physics.

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

    PubMed

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

    2004-01-01

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

  4. Computer-automated neutron activation analysis system

    SciTech Connect

    Minor, M.M.; Garcia, S.R.

    1983-01-01

    An automated delayed neutron counting and instrumental neutron activation analysis system has been developed at Los Alamos National Laboratory's Omega West Reactor (OWR) to analyze samples for uranium and 31 additional elements with a maximum throughput of 400 samples per day. 5 references.

  5. Effects of Magnetic Field Topology on Secondary Neutron Spectra in MagLIF

    NASA Astrophysics Data System (ADS)

    Appelbe, Brian; Chittenden, Jeremy

    2015-11-01

    Ignition in Magneto-Inertial Fusion schemes requires both inertial and magnetic confinement of the fuel and charged fusion products. Recent theoretical and experimental work has demonstrated the confinement of charged fusion products by magnetic fields in Magnetized Liner Inertial Fusion (MagLIF) experiments. This confinement can be inferred from the ratio of secondary to primary neutron yields and the shape of secondary neutron spectra. In this work we investigate the effects of magnetic field topology on the shape of secondary neutron spectra. The MagLIF design has a cylindrical geometry and includes both axial and azimuthal magnetic fields. The azimuthal field is initially in the liner surrounding the fuel but instability growth may cause it to penetrate into the fuel. Charged fusion products (such as tritons or alpha particles) that are isotropically emitted and then confined by an axial field will flow parallel and anti-parallel to the field with equal intensities. In the case of tritons, this motion results in a secondary neutron spectrum emitted in the axial direction that is symmetric. However, in an azimuthal field such particles exhibit singular orbits and there is a net ion drift along the axis. This ion drift can cause the secondary neutron spectrum to be asymmetric. We examine the effects on the spectrum shape of confinement by a combination of axial and azimuthal fields.

  6. Measurement of U-235 Fission Neutron Spectra Using a Multiple Gamma Coincidence Technique

    SciTech Connect

    Ji Chuncheng; Kegel, G.H.R.; Egan, J.J.; DeSimone, D.J.; Alimeti, A.; Roldan, C.F.; McKittrick, T.M.; Kim, D.-S.; Chen, X.; Tremblay, S.E.

    2005-05-24

    The Los Alamos Model of Madland and Nix predicts the shape of the fission neutron energy spectrum for incident primary neutrons of different energies. Verifications of the model normally are limited to measurements of the fission neutron spectra for energies higher than that of the primary neutrons because the low-energy spectrum is distorted by the admixture of elastically and inelastically scattered neutrons. This situation can be remedied by using a measuring technique that separates fission from scattering events. One solution consists of using a fissile sample so thin that fission fragments can be observed indicating the occurrence of a fission event. A different approach is considered in this paper. It has been established that a fission event is accompanied by the emission of between seven and eight gamma rays, while in a scattering interaction, between zero and two gammas are emitted, so that a gamma multiplicity detector should supply a datum to distinguish a fission event from a scattering event. We proceed as follows: A subnanosecond pulsed and bunched proton beam from the UML Van de Graaff generates nearly mono-energetic neutrons by irradiating a thin metallic lithium target. The neutrons irradiate a 235U sample. Emerging neutron energies are measured with a time-of-flight spectrometer. A set of four BaF2 detectors is located close to the 235U sample. These detectors together with their electronic components identify five different events for each neutron detected, i.e., whether four, three, two, one, or none of the BaF2 detectors received one (or more) gamma rays. We present work, preliminary to the final measurements, involving feasibility considerations based on gamma-ray coincidence measurements with four BaF2 detectors, and the design of a Fission-Scattering Discriminator under construction.

  7. Neutron Energy Spectra and Yields from the 7Li(p,n) Reaction for Nuclear Astrophysics

    NASA Astrophysics Data System (ADS)

    Tessler, M.; Friedman, M.; Schmidt, S.; Shor, A.; Berkovits, D.; Cohen, D.; Feinberg, G.; Fiebiger, S.; Krása, A.; Paul, M.; Plag, R.; Plompen, A.; Reifarth, R.

    2016-01-01

    Neutrons produced by the 7Li(p, n)7Be reaction close to threshold are widely used to measure the cross section of s-process nucleosynthesis reactions. While experiments have been performed so far with Van de Graaff accelerators, the use of RF accelerators with higher intensities is planned to enable investigations on radioactive isotopes. In parallel, high-power Li targets for the production of high-intensity neutrons at stellar energies are developed at Goethe University (Frankfurt, Germany) and SARAF (Soreq NRC, Israel). However, such setups pose severe challenges for the measurement of the proton beam intensity or the neutron fluence. In order to develop appropriate methods, we studied in detail the neutron energy distribution and intensity produced by the thick-target 7Li(p,n)7Be reaction and compared them to state-of- the-art simulation codes. Measurements were performed with the bunched and chopped proton beam at the Van de Graaff facility of the Institute for Reference Materials and Measurements (IRMM) using the time-of-flight (TOF) technique with thin (1/8") and thick (1") detectors. The importance of detailed simulations of the detector structure and geometry for the conversion of TOF to a neutron energy is stressed. The measured neutron spectra are consistent with those previously reported and agree well with Monte Carlo simulations that include experimentally determined 7Li(p,n) cross sections, two-body kinematics and proton energy loss in the Li-target.

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

    SciTech Connect

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

    2012-12-15

    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}.

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

    PubMed

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

    2012-12-01

    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 × 10(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(4) nuclear reaction, for which the required tritium originated from the primary fusion reaction, D(d,p)T(3). PMID:23277984

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

    SciTech Connect

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

    2012-10-23

    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/r{sup 2} rule, while total neutron fluence, beyond 80 cm, can be described by diffusion theory using an infinite plane as a neutron source.

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

    SciTech Connect

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

    1998-11-06

    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

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

    SciTech Connect

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

    1999-03-01

    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

  13. Measurement of neutron spectra in the AWE workplace using a Bonner sphere spectrometer.

    PubMed

    Danyluk, Peter

    2010-12-01

    A Bonner sphere spectrometer has been used to measure the neutron spectra in eight different workplace areas at AWE (Atomic Weapons Establishment). The spectra were analysed by the National Physical Laboratory using their principal unfolding code STAY'SL and the results were also analysed by AWE using a bespoke parametrised unfolding code. The bespoke code was designed specifically for the AWE workplace and is very simple to use. Both codes gave results, in good agreement. It was found that the measured fluence rate varied from 2 to 70 neutrons cm⁻² s⁻¹ (± 10%) and the ambient dose equivalent H*(10) varied from 0.5 to 57 µSv h⁻¹ (± 20%). A detailed description of the development and use of the bespoke code is presented.

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

    SciTech Connect

    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.; Casey, D. T.; Gatu-Johnson, M.; Gardner, S.

    2012-10-15

    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.

  15. Neutron counter based on beryllium activation

    SciTech Connect

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

    2014-08-21

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

  16. Neutron counter based on beryllium activation

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    PubMed

    Cottam, J; Paerels, F; Mendez, M

    2002-11-01

    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

  19. Triton Emission Spectra in Some Target Nuclei Irradiated by Ultra-Fast Neutrons

    NASA Astrophysics Data System (ADS)

    Tel, E.; Kaplan, A.; Aydın, A.; Büyükuslu, H.; Demirkol, İ.; Arasoğlu, A.

    2010-08-01

    High-current proton accelerator technologies make use of spallation neutrons produced in ( p,xn) and ( n,xn) nuclear reactions on high-Z targets. The produced neutrons are moderated by heavy water. These moderated neutrons are subsequently captured on 3He to produce tritium via the ( n,p) reaction. Tritium self-sufficiency must be maintained for a commercial power plant. So, working out the systematics of ( n,t) reaction cross sections and triton emission differential data are important for the given reaction taking place on various nuclei at different energies. In this study, triton emission spectra by using ultra-fast neutrons (incident neutron energy >50 MeV), the ( n,xt) reactions for some target nuclei as 16O, 27Al, 56Fe, 59Co, 208Pb and 209Bi have been investigated. In the calculations, the pre-equilibrium and equilibrium effects have been used. The calculated results have been compared with the experimental data taken from the literature.

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

    NASA Astrophysics Data System (ADS)

    Yücel, Haluk; Budak, Mustafa Guray; Karadag, Mustafa; Yüksel, Alptuğ Özer

    2014-11-01

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

  1. Measurement of leakage neutron spectra from graphite cylinders irradiated with D-T neutrons for validation of evaluated nuclear data.

    PubMed

    Luo, F; Han, R; Chen, Z; Nie, Y; Shi, F; Zhang, S; Lin, W; Ren, P; Tian, G; Sun, Q; Gou, B; Ruan, X; Ren, J; Ye, M

    2016-10-01

    A benchmark experiment for validation of graphite data evaluated from nuclear data libraries was conducted for 14MeV neutrons irradiated on graphite cylinder samples. The experiments were performed using the benchmark experimental facility at the China Institute of Atomic Energy (CIAE). The leakage neutron spectra from the surface of graphite (Φ13cm×20cm) at 60° and 120° and graphite (Φ13cm×2cm) at 60° were measured by the time-of-flight (TOF) method. The obtained results were compared with the measurements made by the Monte Carlo neutron transport code MCNP-4C with the ENDF/B-VII.1, CENDL-3.1 and JENDL-4.0 libraries. The results obtained from a 20cm-thick sample revealed that the calculation results with CENDL-3.1 and JENDL-4.0 libraries showed good agreements with the experiments conducted in the whole energy region. However, a large discrepancy of approximately 40% was observed below the 3MeV energy region with the ENDF/B-VII.1 library. For the 2cm-thick sample, the calculated results obtained from the abovementioned three libraries could not reproduce the experimental data in the energy range of 5-7MeV. The graphite data in CENDL-3.1 were verified for the first time and were proved to be reliable. PMID:27620063

  2. Measurement of leakage neutron spectra from graphite cylinders irradiated with D-T neutrons for validation of evaluated nuclear data.

    PubMed

    Luo, F; Han, R; Chen, Z; Nie, Y; Shi, F; Zhang, S; Lin, W; Ren, P; Tian, G; Sun, Q; Gou, B; Ruan, X; Ren, J; Ye, M

    2016-10-01

    A benchmark experiment for validation of graphite data evaluated from nuclear data libraries was conducted for 14MeV neutrons irradiated on graphite cylinder samples. The experiments were performed using the benchmark experimental facility at the China Institute of Atomic Energy (CIAE). The leakage neutron spectra from the surface of graphite (Φ13cm×20cm) at 60° and 120° and graphite (Φ13cm×2cm) at 60° were measured by the time-of-flight (TOF) method. The obtained results were compared with the measurements made by the Monte Carlo neutron transport code MCNP-4C with the ENDF/B-VII.1, CENDL-3.1 and JENDL-4.0 libraries. The results obtained from a 20cm-thick sample revealed that the calculation results with CENDL-3.1 and JENDL-4.0 libraries showed good agreements with the experiments conducted in the whole energy region. However, a large discrepancy of approximately 40% was observed below the 3MeV energy region with the ENDF/B-VII.1 library. For the 2cm-thick sample, the calculated results obtained from the abovementioned three libraries could not reproduce the experimental data in the energy range of 5-7MeV. The graphite data in CENDL-3.1 were verified for the first time and were proved to be reliable.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  4. A simple method for the analysis of neutron resonance capture spectra

    SciTech Connect

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

    2009-03-15

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

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

    PubMed

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

    2005-09-01

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

  6. Neutron and proton activation measurements from Skylab

    NASA Technical Reports Server (NTRS)

    Fishman, G. J.

    1974-01-01

    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.

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

    SciTech Connect

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

    2009-01-21

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

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  9. Miniature Neutron-Alpha Activation Spectrometer

    NASA Astrophysics Data System (ADS)

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

    2002-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

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

  11. Neutron spectra around a tandem linear accelerator in the generation of (18)F with a bonner sphere spectrometer.

    PubMed

    Lagares, J I; Araque, J E Guerrero; Méndez-Villafañe, R; Arce, P; Sansaloni, F; Vela, O; Díaz, C; Campo, Xandra; Pérez, J M

    2016-08-01

    A Bonner sphere spectrometer was used to measure the neutron spectra produced at the collision of protons with an H2(18)O target at different angles. A unique H2(18)O target to produce (18)F was designed and placed in a Tandem linear particle accelerator which produces 8.5MeV protons. The neutron count rates measured with the Bonner spheres were unfolded with the MAXED code. With the GEANT4 Monte Carlo code the neutron spectrum induced in the (p, n) reaction was estimated, this spectrum was used as initial guess during unfolding. Although the cross section of the reaction (18)O(p,n)(18)F is well known, the neutron energy spectra is not correctly defined and it is necessary to verify the simulation with measurements. For this reason, the sensitivity of the unfolding method to the initial spectrum was analyzed applying small variation to the fast neutron peak. PMID:27235889

  12. Neutron spectra around a tandem linear accelerator in the generation of (18)F with a bonner sphere spectrometer.

    PubMed

    Lagares, J I; Araque, J E Guerrero; Méndez-Villafañe, R; Arce, P; Sansaloni, F; Vela, O; Díaz, C; Campo, Xandra; Pérez, J M

    2016-08-01

    A Bonner sphere spectrometer was used to measure the neutron spectra produced at the collision of protons with an H2(18)O target at different angles. A unique H2(18)O target to produce (18)F was designed and placed in a Tandem linear particle accelerator which produces 8.5MeV protons. The neutron count rates measured with the Bonner spheres were unfolded with the MAXED code. With the GEANT4 Monte Carlo code the neutron spectrum induced in the (p, n) reaction was estimated, this spectrum was used as initial guess during unfolding. Although the cross section of the reaction (18)O(p,n)(18)F is well known, the neutron energy spectra is not correctly defined and it is necessary to verify the simulation with measurements. For this reason, the sensitivity of the unfolding method to the initial spectrum was analyzed applying small variation to the fast neutron peak.

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

    NASA Astrophysics Data System (ADS)

    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

    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 γ-ray emission spectra following capture. We present γ-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.

  14. Model atmospheres and X-ray spectra of bursting neutron stars

    NASA Technical Reports Server (NTRS)

    Madej, Jerzy

    1991-01-01

    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.

  15. Nondestructive examination using neutron activated positron annihilation

    DOEpatents

    Akers, Douglas W.; Denison, Arthur B.

    2001-01-01

    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.

  16. Detector-Response Correction of Two-Dimensional γ-Ray Spectra from Neutron Capture

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-01

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.

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

    SciTech Connect

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

    2013-09-01

    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.

  18. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    DOE PAGES

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. Themore » detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.« less

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

    PubMed

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

    2007-11-01

    Fluence spectra at several ground distances in Hiroshima and Nagasaki are provided along with associated fluence-to-kerma coefficients from the Dosimetry System 2002 (DS02). Also included are transmission factors for calculating expected responses of in situ sample measurements of neutron activation products such as (32)P,(36)Cl,(39)Ar,(41)Ca, (60)Co,(63)Ni,(152)Eu, and (154)Eu. The free-in-air (FIA) fluences calculated in 2002 are available for 240 angles, 69 energy groups, 101 ground distances, 5 heights, 4 radiation source components, 2 cities. The DS02 code uses these fluences partitioned to a prompt and delayed portion, collapsed to 58 energy groups and restricted to 97 ground distances. This is because the fluence spectra were required to be in the same format that was used in the older Dosimetry System 1986 (DS86) computer code, of which the DS02 computer code is a modification. The 2002 calculation fluences and the collapsed DS02 code fluences are presented and briefly discussed. A report on DS02, which is available on the website at the Radiation Effects Research Foundation, provides tables and figures of the A-bomb neutron and gamma-ray output used as the sources in the 2002 radiation transport calculations. While figures illustrating the fluence spectra at several ground ranges are presented in the DS02 Report, it does not include any tables of the calculated fluence spectra in the DS02 report. This paper provides, at several standard distances from the hypocenter, the numerical information which is required to translate the FIA neutron fluences given in DS02 to a neutron activation measurement or neutron and gamma-ray soft-tissue dose. PMID:17643260

  20. Neutron Yield Measurements via Aluminum Activation

    SciTech Connect

    1999-12-08

    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.

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

    PubMed

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

    2014-10-01

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

  2. A method for fast evaluation of neutron spectra for BNCT based on in-phantom figure-of-merit calculation.

    PubMed

    Martín, Guido

    2003-03-01

    In this paper a fast method to evaluate neutron spectra for brain BNCT is developed. The method is based on an algorithm to calculate dose distribution in the brain, for which a data matrix has been taken into account, containing weighted biological doses per position per incident energy and the incident neutron spectrum to be evaluated. To build the matrix, using the MCNP 4C code, nearly monoenergetic neutrons were transported into a head model. The doses were scored and an energy-dependent function to biologically weight the doses was used. To find the beam quality, dose distribution along the beam centerline was calculated. A neutron importance function for this therapy to bilaterally treat deep-seated tumors was constructed in terms of neutron energy. Neutrons in the energy range of a few tens of kilo-electron-volts were found to produce the best dose gain, defined as dose to tumor divided by maximum dose to healthy tissue. Various neutron spectra were evaluated through this method. An accelerator-based neutron source was found to be more reliable for this therapy in terms of therapeutic gain than reactors.

  3. Measurement of residual 60Co activity induced by atomic-bomb neutrons in Nagasaki and background contribution by environmental neutrons.

    PubMed

    Shizuma, Kiyoshi; Endo, Satoru; Hoshi, Masaharu; Takada, Jun; Iwatani, Kazuo; Hasai, Hiromi; Oka, Takamitsu; Shimazaki, Tatsuya; Okumura, Yutaka; Fujita, Shoichiro; Watanabe, Tadaaki; Imanaka, Tetsuji

    2002-12-01

    Residual 60Co activity in five steel samples induced by neutrons from the Nagasaki atomic bomb has been measured within about 1000 m from the hypocenter. The chemical separation of cobalt and nickel from steel samples was performed, and cobalt-enriched samples were prepared for all samples. Gamma-ray measurements were carried out with a low-background well-type germanium detector. The gamma-ray spectra for five samples were compared with the spectrum of a control sample to ensure that the observed 60Co was actually induced by A-bomb neutrons. The activation of cobalt by environmental neutrons was also investigated. It has been shown that the present 60Co data are consistent with earlier Hashizume's data. PMID:12674203

  4. Characteristics and application of spherical-type activation detectors in neutron spectrum measurements at a boron neutron capture therapy (BNCT) facility

    NASA Astrophysics Data System (ADS)

    Lin, Heng-Xiao; Chen, Wei-Lin; Liu, Yuan-Hao; Sheu, Rong-Jiun

    2016-03-01

    A set of spherical-type activation detectors was developed aiming to provide better determination of the neutron spectrum at the Tsing Hua Open-pool Reactor (THOR) BNCT facility. An activation foil embedded in a specially designed spherical holder exhibits three advantages: (1) minimizing the effect of neutron angular dependence, (2) creating response functions with broadened coverage of neutron energies by introducing additional moderators or absorbers to the central activation foil, and (3) reducing irradiation time because of improved detection efficiencies to epithermal neutron beam. This paper presents the design concept and the calculated response functions of new detectors. Theoretical and experimental demonstrations of the performance of the detectors are provided through comparisons of the unfolded neutron spectra determined using this method and conventional multiple-foil activation techniques.

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

    PubMed

    Mohapatra, D K; Mohanakrishnan, P

    2002-07-01

    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.

  6. Neutron activation analysis of an Egyptian monazite ore sample

    NASA Astrophysics Data System (ADS)

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

    1999-01-01

    The absolute sensitivity of a gamma-ray line following thermal or epithermal neutron activation is expressed as a product of four terms, namely, the intrinsic, irradiation, decay and measurement factors. The total absolute sensitivity is the sum of the absolute sensitivities due to thermal and epithermal activation. A. FORTRAN computer program was prepared on the TANDY 3000 NL PCA to calculate the total absolute sensitivity of the intensive gamma-ray lines from the thermal and epithermal neutron activation of all the naturally occurring nuclides. Another program was prepared for the determination of the total absolute sensitivity for gammarays emitted by radioactive daughters such as233Pa from233Th and239Np from239U. Long time irradiation periods (about 48 hours) for specimens of the monazite ore sample were carried out at the (ET-RR-1) reactor core periphery. The monazite ore sample was separated from the associating minerals in the sand of Abou-Khashaba of Rashied (Rosetta) area on the Mediterranean (North of Egypt). The separated monazite ore sample was provided by the Nuclear Material Authority of Egypt. The cadmium difference method was applied to thin gold foils for absolute thermal and epithermal neutron flux determination. The gamma-ray spectra were measured using a spectrometer with a HPGe coaxial detector. The evaluated absolute sensitivity tables were helpful in identifying the radioisotopes contributing to the gamma- ray spectra and in evaluating the elemental concentration of the monazite constitutents. Most of the rare earth elements were observed and their concentrations are reported. La, Ce, Nd, Sd and Th were found as major elements, U, Tb, Hf and Eu as minor elements.

  7. Neutron Fluence Monitoring by Foil Activation at the NBSR

    SciTech Connect

    Richard M. Lindstrom

    2000-11-12

    In a reactor facility such as the National Institute of Standards and Technology Center for Neutron Research, it is occasionally necessary to measure the intensity and characteristics of neutron fields, inside and outside the reactor vessel. Design of thermal- and cold-neutron beam guides and filters, neutron activation analysis, and health physics calibrations are the most common needs. To meet these requirements, routine procedures have been developed for efficient and transparent measurements of slow neutrons.

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

    PubMed Central

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

    1979-01-01

    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 μm) 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. PMID:16345472

  9. A neutron activation spectrometer and neutronic experimental platform for the National Ignition Facility (invited)

    NASA Astrophysics Data System (ADS)

    Yeamans, C. B.; Gharibyan, N.

    2016-11-01

    At the National Ignition Facility, the diagnostic instrument manipulator-based neutron activation spectrometer is used as a diagnostic of implosion performance for inertial confinement fusion experiments. Additionally, it serves as a platform for independent neutronic experiments and may be connected to fast recording systems for neutron effect tests on active electronics. As an implosion diagnostic, the neutron activation spectrometers are used to quantify fluence of primary DT neutrons, downscattered neutrons, and neutrons above the primary DT neutron energy created by reactions of upscattered D and T in flight. At a primary neutron yield of 1015 and a downscattered fraction of neutrons in the 10-12 MeV energy range of 0.04, the downscattered neutron fraction can be measured to a relative uncertainty of 8%. Significant asymmetries in downscattered neutrons have been observed. Spectrometers have been designed and fielded to measure the tritium-tritium and deuterium-tritium neutron outputs simultaneously in experiments using DT/TT fusion ratio as a direct measure of mix of ablator into the gas.

  10. In-pile and post-irradiation creep of type 304 stainless steel under different neutron spectra

    NASA Astrophysics Data System (ADS)

    Kurata, Y.; Itabashi, Y.; Mimura, H.; Kikuchi, T.; Amezawa, H.; Shimakawa, S.; Tsuji, H.; Shindo, M.

    2000-12-01

    In addition to post-irradiation creep tests, in-pile creep tests were performed using newly developed technology with in situ measurement under different neutron spectra. The in-pile creep properties of type 304 stainless steel at 550°C appear to depend on neutron spectrum, but a spectral effect on post-irradiation creep properties is not clearly seen. The rupture time of in-pile creep under a high thermal neutron flux condition is the shortest. The order of the rupture time following the high thermal flux condition is post-irradiation creep, in-pile creep with a thermal neutron shield condition and finally creep of unirradiated material, all in increasing order. It is suggested that the acceleration of creep deformation and fracture observed in irradiation creep tests may be related to enhancement of thermal creep in terms of FMD increased under a high thermal neutron flux in addition to increased helium embrittlement.

  11. IIB soliton spectra with all fluxes activated

    NASA Astrophysics Data System (ADS)

    Evslin, Jarah

    2003-05-01

    Building upon an earlier proposal for the classification of fluxes, a sequence is proposed which generalizes the AHSS by computing type IIB string theory's group of conserved RR and also NS charges, which is conjectured to be a K-theory of dual pairs. As a test of this proposal, the formalism of Maldacena, Moore and Seiberg ( arxiv:hep-th/0108100) is applied to classify D-branes, NS5-branes, F-strings and their dielectric counterparts in IIB compactified on a 3-sphere with both NS and RR background fluxes. The soliton spectra on the 3-sphere are then compared with the output of the sequence, as is the baryon spectrum in Witten's non- spinc example, AdS 5× RP5. The group of conserved charges is seen to change during Brown-Teitelboim-like phase transitions which change the effective cosmological constant.

  12. Inelastic neutron scattering spectra of alkali metal (Na, K) bifluorides: The harmonic overtone of v3

    NASA Astrophysics Data System (ADS)

    Waddington, Thomas C.; Howard, Joseph; Brierley (in part), Keith P.; Tomkinson, John

    1982-01-01

    Inelastic neutron scattering spectra of MFHF (M  Na and K) have been measured up to energy transfers of ca. 4000 cm -1 Both 0 → 1 and 0 → 2 transitions of the bending ( v2), and antisymmetric stretching ( v3) modes were observed. A normal harmonic (i.e. no quartic contribution) model for the dynamics of the bifluoride ion is entirely consistent with our observations. Evidence of phonon dispersion was observed in the band shape of v3, but no structure attributable to the LO mode could be found. The similarity of the band shapes of v3 for both NaFHF and KFHF is interpreted in terms of a very short range coupling mechanism.

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

    SciTech Connect

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

    1984-07-02

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

  14. Code System for Calculating Alpha, N; Spontaneous Fission; and Delayed Neutron Sources and Spectra.

    2002-07-18

    Version: 04 SOURCES4C is a code system that determines neutron production rates and spectra from (alpha,n) reactions, spontaneous fission, and delayed neutron emission due to radionuclide decay. In this release the three-region problem was modified to correct several bugs, and new documentation was added to the package. Details are available in the included LA-UR-02-1617 (2002) report. The code is capable of calculating (alpha,n) source rates and spectra in four types of problems: homogeneous media (i.e.,more » an intimate 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. The process of creating a SOURCES input file (tape1) is streamlined with the Los Alamos SOURCES Tape1 Creator and Library Link (LASTCALL) Version 1. Intended to supplement the SOURCES manual, LASTCALL is a simple graphical user interface designed to minimize common errors made during input. The optional application, LASTCALL, consists of a single dialog window launched from an executable (lastcall.exe) on Windows-based personal computers.« less

  15. X-ray spectra and atmospheric structures of bursting neutron stars

    NASA Technical Reports Server (NTRS)

    Ebisuzaki, Toshikazu

    1987-01-01

    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.

  16. Improved Modeling of Prompt Fission Neutron Spectra for Nuclear Data Evaluations

    NASA Astrophysics Data System (ADS)

    Neudecker, Denise; Talou, Patrick; Kawano, Toshihiko; Kahler, Albert C.; White, Morgan C.

    2015-10-01

    The prompt fission neutron spectra (PFNS) of major actinides such as 239Pu and 235U are quantities of interest for nuclear physics application areas including reactor physics and national security. Nuclear data evaluations provide recommended data for those application areas based on nuclear theory and experiments. Here, we present improvements made to the effective models predicting the PFNS up to incident neutron energies of 30 MeV and their impact on evaluations. These models describe relevant physics processes better than those used for the current US nuclear data library ENDF/B-VII.1. In addition, the use of higher-fidelity models such as Monte Carlo Hauser-Feshbach calculations will be discussed in the context of future PFNS evaluations. (LA-UR-15-24763) This work was carried out under the auspices of the US Department of Energy, National Nuclear Security Administration and Office of Science, and performed by Los Alamos National Security LLC under Contract DE-AC52-06NA25396.

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

    USGS Publications Warehouse

    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

    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.

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

    SciTech Connect

    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

    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.

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

    SciTech Connect

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

    2002-01-01

    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.

  20. Active Neutron Shielding R&D for Dark Matter Searches

    NASA Astrophysics Data System (ADS)

    Henderson, Shawn; Monroe, Jocelyn; Fisher, Peter; Dmtpc Collaboration

    2011-04-01

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

  1. A comparative study of the neutron flux spectra in the MNSR irradiation sites for the HEU and LEU cores using the MCNP4C code.

    PubMed

    Dawahra, S; Khattab, K; Saba, G

    2015-10-01

    A comparative study for fuel conversion from the HEU to LEU in the Miniature Neutron Source Reactor (MNSR) has been performed in this paper using the MCNP4C code. The neutron energy and lethargy flux spectra in the first inner and outer irradiation sites of the MNSR reactor for the existing HEU fuel (UAl4-Al, 90% enriched) and the potential LEU fuels (U3Si2-Al, U3Si-Al, U9Mo-Al, 19.75% enriched and UO2, 12.6% enriched) were investigated using the MCNP4C code. The neutron energy flux spectra for each group was calculated by dividing the neutron flux by the width of each energy group. The neutron flux spectra per unit lethargy was calculated by multiplying the neutron energy flux spectra for each energy group by the average energy of each group. The thermal neutron flux was calculated by summing the neutron fluxes from 0.0 to 0.625 eV, the fast neutron flux was calculated by summing the neutron fluxes from 0.5 MeV to 10 MeV for the existing HEU and potential LEU fuels. Good agreements have been noticed between the flux spectra for the potential LEU fuels and the existing HEU fuels with maximum relative differences less than 10% and 8% in the inner and outer irradiation sites.

  2. Electromagnetic Emission from Long-lived Binary Neutron Star Merger Remnants. II. Lightcurves and Spectra

    NASA Astrophysics Data System (ADS)

    Siegel, Daniel M.; Ciolfi, Riccardo

    2016-03-01

    Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ˜107 s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ˜102-104 s after the BNS merger with luminosities of LX ˜ 1046-1048 erg s-1. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.

  3. Total body nitrogen analysis. [neutron activation analysis

    NASA Technical Reports Server (NTRS)

    Palmer, H. E.

    1975-01-01

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

  4. Neutron activation analysis of Etruscan pottery

    SciTech Connect

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

    1992-07-01

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

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

    SciTech Connect

    Perna, Rosalba; Ho, Wynn C. G.; Verde, Licia; Jimenez, Raul; Van Adelsberg, Matthew

    2012-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  7. Photon and neutron active interrogation of highly enriched uranium.

    SciTech Connect

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

    2004-01-01

    The physics of photon and neutron active interrogation of highly enriched uranium (HEU) using the delayed neutron reinterrogation method is described in this paper. Two sets of active interrogation experiments were performed using a set of subcritical configurations of cocentric HEU metal hemishells. One set of measurements utilized a pulsed 14-MeV neutron generator as the active source. The second set of measurements utilized a linear accelerator-based bremsstrahlung photon source as an active interrogation source. The neutron responses were measured for both sets of experiments. The operational details and results for both measurement sets are described.

  8. ACTIV87: Fast Neutron Activation Cross Section File

    1993-08-01

    4. HISTORICAL BACKGROUND AND INFORMATION ACTIV87 is a compilation of fast neutron induced activation reaction cross-sections. The compilation covers energies from threshold to 20 MeV and is based on evaluated data taken from other evaluated data libraries and individual evaluations. The majority of these evaluations were performed by using available experimental data. The aforementioned available experimental data were used in the selection of needed parameters for theoretical computations and for normalizing the results of suchmore » computations. Theoretical calculations were also used for interpolation and extrapolation of experimental cross-section data. All of the evaluated data curves were compared with experimental data that had been reported over the four year period preceding 1987. Only those cross-sections not in contradiction with experimental data that was current in 1987 were retained in the activation file, ACTIV87. In cases of several conflicting evaluations, that evaluation was chosen which best corresponded to the experimental data. A few evaluated curves were renormalized in accordance with the results of the latest precision measurements. 5. APPLICATION OF THE DATA 6. SOURCE AND SCOPE OF DATA The following libraries and individual files of evaluated neutron cross-section data were used for the selection of the activation cross-sections: the BOSPOR Library, the Activation File of the Evaluated Nuclear Data Library, the Evaluated Neutron Data File (ENDF/B-V) Activation File, the International Reactor Dosimetry File (IRDF-82), and individual evaluations carried out under various IAEA research contracts. The file of selected reactions contains 206 evaluated cross-section curves of the (n,2n), (n,p) and (n,a) reactions which lead to radioactive products and may be used in many practical applications of neutron activation analysis. Some competing activation reactions, usually with low cross-section values, are given for completeness.« less

  9. Neutron activation analysis in archaeological chemistry

    SciTech Connect

    Harbottle, G.

    1987-01-01

    Neutron activation analysis has proven to be a convenient way of performing the chemical analysis of archaeologically-excavated artifacts and materials. It is fast and does not require tedious laboratory operations. It is multielement, sensitive, and can be made nondestructive. Neutron activation analysis in its instrumental form, i.e., involving no chemical separation, is ideally suited to automation and conveniently takes the first step in data flow patterns that are appropriate for many taxonomic and statistical operations. The future will doubtless see improvements in the practice of NAA in general, but in connection with archaeological science the greatest change will be the filling, interchange and widespread use of data banks based on compilations of analytical data. Since provenience-oriented data banks deal with materials (obsidian, ceramics, metals, semiprecious stones, building materials and sculptural media) that participated in trade networks, the analytical data is certain to be of interest to a rather broad group of archaeologists. It is to meet the needs of the whole archaeological community that archaeological chemistry must now turn.

  10. Development of high flux thermal neutron generator for neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Vainionpaa, Jaakko H.; Chen, Allan X.; Piestrup, Melvin A.; Gary, Charles K.; Jones, Glenn; Pantell, Richard H.

    2015-05-01

    The new model DD110MB neutron generator from Adelphi Technology produces thermal (<0.5 eV) neutron flux that is normally achieved in a nuclear reactor or larger accelerator based systems. Thermal neutron fluxes of 3-5 · 107 n/cm2/s are measured. This flux is achieved using four ion beams arranged concentrically around a target chamber containing a compact moderator with a central sample cylinder. Fast neutron yield of ∼2 · 1010 n/s is created at the titanium surface of the target chamber. The thickness and material of the moderator is selected to maximize the thermal neutron flux at the center. The 2.5 MeV neutrons are quickly thermalized to energies below 0.5 eV and concentrated at the sample cylinder. The maximum flux of thermal neutrons at the target is achieved when approximately half of the neutrons at the sample area are thermalized. In this paper we present simulation results used to characterize performance of the neutron generator. The neutron flux can be used for neutron activation analysis (NAA) prompt gamma neutron activation analysis (PGNAA) for determining the concentrations of elements in many materials. Another envisioned use of the generator is production of radioactive isotopes. DD110MB is small enough for modest-sized laboratories and universities. Compared to nuclear reactors the DD110MB produces comparable thermal flux but provides reduced administrative and safety requirements and it can be run in pulsed mode, which is beneficial in many neutron activation techniques.

  11. Utilization of the intense pulsed neutron source (IPNS) at Argonne National Laboratory for neutron activation analysis

    SciTech Connect

    Heinrich, R.R.; Greenwood, L.R.; Popek, R.J.; Schulke, A.W. Jr.

    1983-01-01

    The Intense Pulsed Neutron Source (IPNS) neutron scattering facility (NSF) has been investigated for its applicability to neutron activation analysis. A polyethylene insert has been added to the vertical hole VT3 which enhances the thermal neutron flux by a factor of two. The neutron spectral distribution at this position has been measured by the multiple-foil technique which utilized 28 activation reactions and the STAYSL computer code. The validity of this spectral measurement was tested by two irradiations of National Bureau of Standards SRM-1571 (orchard leaves), SRM-1575 (pine needles), and SRM-1645 (river sediment). The average thermal neutron flux for these irradiations normalized to 10 ..mu..amp proton beam is 4.0 x 10/sup 11/ n/cm/sup 2/-s. Concentrations of nine trace elements in each of these SRMs have been determined by gamma-ray spectrometry. Agreement of measured values to certified values is demonstrated to be within experiment error.

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

    PubMed

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

    1990-01-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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%.

  14. Neutron activation of NIF Final Optics Assemblies

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  15. Left–right asymmetry in integral spectra of γ-quanta in the interaction of nuclei with polarized thermal neutrons

    SciTech Connect

    Vesna, V. A.; Gledenov, Yu. M.; Nesvizhevsky, V. V.; Sedyshev, P. V.; Shul’gina, E. V.

    2015-10-15

    The paper presents results of preliminarymeasurements of the left–right asymmetry in integral spectra of γ-quanta emitted in the interaction of polarized thermal neutrons with nuclei. These results indicate that for all cases of measured statistically significant P-odd asymmetry, the left–right asymmetry coefficient is much smaller than the P-odd asymmetry coefficient. This observation is not consistent with the predictions of theoretical calculations.

  16. Analysis of the neutron component at high altitude mountains using active and passive measurement devices.

    PubMed

    Hajek, M; Berger, T; Schoner, W; Vana, N

    2002-01-01

    The European Council directive 96/29/Euratom requires dosimetric precautions if the effective dose exceeds 1 mSv/a. On an average, this value is exceeded by aircrew members. Roughly half of the radiation exposure at flight altitudes is caused by cosmic ray-induced neutrons. Active (6LiI(Eu)-scintillator) and passive (TLDs) Bonner sphere spectrometers were used to determine the neutron energy spectra atop Mt. Sonnblick (3105 m) and Mt. Kitzsteinhorn (3029 m). Further measurements in a mixed radiation field at CERN as well as in a proton beam of 62 MeV at Paul Scherrer Institute, Switzerland, confirmed that not only neutrons but also charged particles contribute to the readings of active detectors, whereas TLD-600 and TLD-700 in pair allow the determination of the thermal neutron flux. Unfolding of the detector data obtained atop both mountains shows two relative maxima around 1 MeV and 85 MeV, which have to be considered for the assessment of the biologically relevant dose equivalent. By convoluting the spectra with appropriate conversion functions the neutron dose equivalent rate was determined to be 150 +/- 15 nSv/h. The total dose equivalent rate determined by the HTR-method was 210 +/- 15 nSv/h. The results are in good agreement with LET-spectrometer and Sievert counter measurements carried out simultaneously.

  17. Analysis of the neutron component at high altitude mountains using active and passive measurement devices

    NASA Astrophysics Data System (ADS)

    Hajek, M.; Berger, T.; Schöner, W.; Vana, N.

    2002-01-01

    The European Council directive 96/29/Euratom requires dosimetric precautions if the effective dose exceeds 1 mSv/a. On an average, this value is exceeded by aircrew members. Roughly half of the radiation exposure at flight altitudes is caused by cosmic ray-induced neutrons. Active ( 6LiI(Eu)-scintillator) and passive (TLDs) Bonner sphere spectrometers were used to determine the neutron energy spectra atop Mt. Sonnblick (3105 m) and Mt. Kitzsteinhorn (3029 m). Further measurements in a mixed radiation field at CERN as well as in a proton beam of 62 MeV at Paul Scherrer Institute, Switzerland, confirmed that not only neutrons but also charged particles contribute to the readings of active detectors, whereas TLD-600 and TLD-700 in pair allow the determination of the thermal neutron flux. Unfolding of the detector data obtained atop both mountains shows two relative maxima around 1 MeV and 85 MeV, which have to be considered for the assessment of the biologically relevant dose equivalent. By convoluting the spectra with appropriate conversion functions the neutron dose equivalent rate was determined to be 150±15 nSv/h. The total dose equivalent rate determined by the HTR-method was 210±15 nSv/h. The results are in good agreement with LET-spectrometer and Sievert counter measurements carried out simultaneously.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    Calculations of the neutron-capture cross section at low neutron energies (10 eV through 100's of keV) are very sensitive to the nuclear level density and radiative strength function. These quantities are often poorly known, especially for radioactive targets, and actual measurements of the capture cross section are usually required. An additional constraint on the calculation of the capture cross section is provided by measurements of the cascade gamma spectrum following neutron capture. Recent measurements of 234 , 236 , 238U(n, γ) emission spectra made using the DANCE 4 π BaF2 array at the Los Alamos Neutron Science Center will be presented. Calculations of gamma-ray spectra made using the DICEBOX code and of the capture cross section made using the CoH3 code will also be presented. These techniques may be also useful for calculations of more unstable nuclides. This work was performed with the support of the U.S. Department of Energy, National Nuclear Security Administration by Los Alamos National Security, LLC (Contract DE-AC52-06NA25396) and Lawrence Livermore National Security, LLC (Contract DE-AC52-07NA2734).

  19. Mineral exploration and soil analysis using in situ neutron activation

    USGS Publications Warehouse

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

    1966-01-01

    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.

  20. QUANTUM NATURE OF CYCLOTRON HARMONICS IN THERMAL SPECTRA OF NEUTRON STARS

    SciTech Connect

    Suleimanov, V. F.; Werner, K.; Pavlov, G. G. E-mail: pavlov@astro.psu.ed

    2010-05-01

    Some isolated neutron stars (NSs) show harmonically spaced absorption features in their thermal soft X-ray spectra. The interpretation of the features as a cyclotron line and its harmonics has been suggested, but the usual explanation of the harmonics as caused by relativistic effects fails because the relativistic corrections are extremely small in this case. We suggest that the features, known as quantum oscillations, correspond to the peaks in the energy dependence of the free-free opacity in a quantizing magnetic field. The peaks arise when the transitions to new Landau levels become allowed with increasing the photon energy; they are strongly enhanced by the square-root singularities in the phase-space density of quantum states in the case when the free (non-quantized) motion is effectively one dimensional. 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 the so-called central compact objects in supernova remnants, such as 1E 1207.4-5209 in PKS 1209-51/52. We show that observable features at the electron cyclotron harmonics form at moderately large values of the quantization parameter, b{sub eff} {identical_to} E{sub c,e}/kT{sub eff} {approx_equal} 0.5-20. The equivalent widths of the features can reach {approx}100-200 eV; they grow with increasing b{sub eff} and are lower for higher harmonics.

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

    SciTech Connect

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

    2014-08-21

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

  2. Method for measuring dose-equivalent in a neutron flux with an unknown energy spectra and means for carrying out that method

    DOEpatents

    Distenfeld, Carl H.

    1978-01-01

    A method for measuring the dose-equivalent for exposure to an unknown and/or time varing neutron flux which comprises simultaneously exposing a plurality of neutron detecting elements of different types to a neutron flux and combining the measured responses of the various detecting elements by means of a function, whose value is an approximate measure of the dose-equivalent, which is substantially independent of the energy spectra of the flux. Also, a personnel neutron dosimeter, which is useful in carrying out the above method, comprising a plurality of various neutron detecting elements in a single housing suitable for personnel to wear while working in a radiation area.

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

    SciTech Connect

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

    2012-10-15

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

  4. Neutron flux spectra and radiation damage parameters for the Russian Bor-60 and SM-2 reactors

    SciTech Connect

    Karasiov, A.V.; Greenwood, L.R.

    1995-04-01

    The objective is to compare neutron irradiation conditions in Russian reactors and similar US facilities. Neutron fluence and spectral information and calculated radiation damage parameters are presented for the BOR-60 (Fast Experimental Reactor - 60 MW) and SM-2 reactors in Russia. Their neutron exposure characteristics are comparable with those of the Experimental Breeder Reactor (ERB-II), the Fast Flux Test Facility (FFTF), and the High Flux Isotope Reactor (HFIR) in the United States.

  5. Layered shielding design for an active neutron interrogation system

    NASA Astrophysics Data System (ADS)

    Whetstone, Zachary D.; Kearfott, Kimberlee J.

    2016-08-01

    The use of source and detector shields in active neutron interrogation can improve detector signal. In simulations, a shielded detector with a source rotated π/3 rad relative to the opening decreased neutron flux roughly three orders of magnitude. Several realistic source and detector shield configurations were simulated. A layered design reduced neutron and secondary photon flux in the detector by approximately one order of magnitude for a deuterium-tritium source. The shield arrangement can be adapted for a portable, modular design.

  6. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    DOE PAGES

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; et al

    2015-11-12

    For a long time, neutron time-of-flight diagnostics been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d+t→n+α (DT) and d+d→n+³He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, which is also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent Tion and DSR.

  7. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    SciTech Connect

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; Mcnaney, J. M.; Munro, D. H.

    2015-11-12

    For a long time, neutron time-of-flight diagnostics been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d+t→n+α (DT) and d+d→n+³He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, which is also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent Tion and DSR.

  8. Active and sterile neutrino mass effects on beta decay spectra

    SciTech Connect

    Boillos, Juan Manuel; Moya de Guerra, Elvira

    2013-06-10

    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.

  9. 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)

    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

    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.

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

    PubMed

    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

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

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

    SciTech Connect

    Paul, Sabyasachi; Sahoo, G. S.; Tripathy, S. P. E-mail: tripathy@barc.gov.in; Sunil, C.; Bandyopadhyay, T.; Sharma, S. C.; Ramjilal,; Ninawe, N. G.; Gupta, A. K.

    2014-06-15

    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.

  12. Prompt fission neutron spectra from fission induced by 1 to 8 MeV neutrons on {sup 235}U and {sup 239}Pu using the double time-of-flight technique

    SciTech Connect

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

    2011-03-15

    Prompt fission neutron spectra from {sup 235}U and {sup 239}Pu were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg {sup 235}U and 90 mg {sup 239}Pu detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced {gamma}-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.

  13. A method for measuring tissue-equivalent dose using a pin diode and activation foil in epithermal neutron beams with EN < 100 keV.

    PubMed

    Carolan, Martin G; Rosenfeld, Anatoly B

    2006-01-01

    Silicon (Si) pin diodes can be used for neutron dosimetry by observing the change in forward bias voltage caused by neutron induced displacement damage in the diode junction. Pin diode energy response depends on Si displacement damage KERMA (K(Si)). It is hypothesised that tissue-equivalent (TE) neutron dose could be expressed as a linear combination of K(Si) and foil activation terms. Monte Carlo simulations (MCNP) of parallel monoenergetic neutron beams incident on a cylindrical TE phantom were used to calculate TE dose, K(Si) and Au, Cu and Mn foil activations along the central axis of the phantom. For spectra with neutron energies <100 keV, it is possible to estimate the TE kerma based on silicon damage kerma and Cu or Mn foil measurements. More accurate estimates are possible for spectra where the maximum neutron energy does not exceed 30 keV. PMID:16644975

  14. A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA

    SciTech Connect

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

    2010-09-10

    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.

  15. Validation of MCNP NPP Activation Simulations for Decommissioning Studies by Analysis of NPP Neutron Activation Foil Measurement Campaigns

    NASA Astrophysics Data System (ADS)

    Volmert, Ben; Pantelias, Manuel; Mutnuru, R. K.; Neukaeter, Erwin; Bitterli, Beat

    2016-02-01

    In this paper, an overview of the Swiss Nuclear Power Plant (NPP) activation methodology is presented and the work towards its validation by in-situ NPP foil irradiation campaigns is outlined. Nuclear Research and consultancy Group (NRG) in The Netherlands has been given the task of performing the corresponding neutron metrology. For this purpose, small Aluminium boxes containing a set of circular-shaped neutron activation foils have been prepared. After being irradiated for one complete reactor cycle, the sets have been successfully retrieved, followed by gamma-spectrometric measurements of the individual foils at NRG. Along with the individual activities of the foils, the reaction rates and thermal, intermediate and fast neutron fluence rates at the foil locations have been determined. These determinations include appropriate corrections for gamma self-absorption and neutron self-shielding as well as corresponding measurement uncertainties. The comparison of the NPP Monte Carlo calculations with the results of the foil measurements is done by using an individual generic MCNP model functioning as an interface and allowing the simulation of individual foil activation by predetermined neutron spectra. To summarize, the comparison between calculation and measurement serve as a sound validation of the Swiss NPP activation methodology by demonstrating a satisfying agreement between measurement and calculation. Finally, the validation offers a chance for further improvements of the existing NPP models by ensuing calibration and/or modelling optimizations for key components and structures.

  16. Active Neutron Interrogation to Detect Shielded Fissionable Material

    SciTech Connect

    D. L. Chichester; E. H. Seabury

    2009-05-01

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

  17. Raman spectra of semiconductor nanoparticles: Disorder-activated phonons

    NASA Astrophysics Data System (ADS)

    Ingale, Alka; Rustagi, K. C.

    1998-09-01

    We present Raman spectra of four semiconductor doped glasses and a single crystal of CdS0.55Se0.45 in the range 30-800 cm-1 in the backscattering geometry. This includes the first-order Raman scattering from the disorder-activated zone-edge phonons and the LO phonons. TO phonon modes are not observed, as in bulk CdS, for the excitation well above the lowest gap. We show that the asymmetric line profile of the LO phonon structure can be understood as a composite of two phonon modes: the zone center and the zone edge phonons. Disorder-activated modes in the (30-130)-cm-1 range and the higher-order Raman spectra are also observed and found to be consistent with this assignment.

  18. Estimation of Covariances on Prompt Fission Neutron Spectra and Impact of the PFNS Model on the Vessel Fluence

    NASA Astrophysics Data System (ADS)

    Berge, Léonie; Litaize, Olivier; Serot, Olivier; Archier, Pascal; De Saint Jean, Cyrille; Pénéliau, Yannick; Regnier, David

    2016-02-01

    As the need for precise handling of nuclear data covariances grows ever stronger, no information about covariances of prompt fission neutron spectra (PFNS) are available in the evaluated library JEFF-3.2, although present in ENDF/B-VII.1 and JENDL-4.0 libraries for the main fissile isotopes. The aim of this work is to provide an estimation of covariance matrices related to PFNS, in the frame of some commonly used models for the evaluated files, such as the Maxwellian spectrum, the Watt spectrum, or the Madland-Nix spectrum. The evaluation of PFNS through these models involves an adjustment of model parameters to available experimental data, and the calculation of the spectrum variance-covariance matrix arising from experimental uncertainties. We present the results for thermal neutron induced fission of 235U. The systematic experimental uncertainties are propagated via the marginalization technique available in the CONRAD code. They are of great influence on the final covariance matrix, and therefore, on the spectrum uncertainty band width. In addition to this covariance estimation work, we have also investigated the importance on a reactor calculation of the fission spectrum model choice. A study of the vessel fluence depending on the PFNS model is presented. This is done through the propagation of neutrons emitted from a fission source in a simplified PWR using the TRIPOLI-4® code. This last study includes thermal fission spectra from the FIFRELIN Monte-Carlo code dedicated to the simulation of prompt particles emission during fission.

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

    PubMed

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

    2015-12-01

    A neutron irradiation cavity for in vivo neutron activation analysis (IVNAA) to detect manganese, aluminum, and other potentially toxic elements in human hand bone has been designed and its dosimetric specifications measured. The neutron source is a customized deuterium-deuterium neutron generator that produces neutrons at 2.45 MeV by the fusion reaction 2H(d, n)3He at a calculated flux of 7 × 10(8) ± 30% s(-1). A moderator/reflector/shielding [5 cm high density polyethylene (HDPE), 5.3 cm graphite and 5.7 cm borated (HDPE)] assembly has been designed and built to maximize the thermal neutron flux inside the hand irradiation cavity and to reduce the extremity dose and effective dose to the human subject. Lead sheets are used to attenuate bremsstrahlung x rays and activation gammas. A Monte Carlo simulation (MCNP6) was used to model the system and calculate extremity dose. The extremity dose was measured with neutron and photon sensitive film badges and Fuji electronic pocket dosimeters (EPD). The neutron ambient dose outside the shielding was measured by Fuji NSN3, and the photon dose was measured by a Bicron MicroREM scintillator. Neutron extremity dose was calculated to be 32.3 mSv using MCNP6 simulations given a 10-min IVNAA measurement of manganese. Measurements by EPD and film badge indicate hand dose to be 31.7 ± 0.8 mSv for neutrons and 4.2 ± 0.2 mSv for photons for 10 min; whole body effective dose was calculated conservatively to be 0.052 mSv. Experimental values closely match values obtained from MCNP6 simulations. These are acceptable doses to apply the technology for a manganese toxicity study in a human population. PMID:26509624

  20. A dosimetry study of deuterium-deuterium neutron generator-based in vivo neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Sowers, Daniel A.

    A neutron irradiation cavity for in vivo Neutron Activation Analysis (IVNAA) to detect manganese, aluminum, and other potentially toxic elements in human hand bone has been designed and its dosimetric specifications measured. The neutron source is a customized deuterium-deuterium neutron generator which produces neutrons at 2.45 MeV by the fusion reaction 2H(d, n)3He at a calculated flux of 7 x 108 +/-30% s-1. A moderator/reflector/shielding (5 cm high density polyethylene (HDPE), 5.3 cm graphite & 5.7 cm borated HDPE) assembly has been designed and built to maximize the thermal neutron flux inside the hand irradiation cavity and to reduce the extremity dose and effective dose to the human subject. Lead sheets are used to attenuate bremsstrahlung x rays and activation gammas. A Monte Carlo simulation (MCNP6) was used to model the system and calculate extremity dose. The extremity dose was measured with neutron and photon sensitive film badges and Fuji electronic pocket dosimeter (EPD). The neutron ambient dose outside the shielding was measured by Fuji NSN3, and photon dose by a Bicron MicroREM scintillator. Neutron extremity dose was calculated to be 32.3 mSv using MCNP6 simulations given a 10 min IVNAA measurement of manganese. Measurements by EPD and film badge indicate hand dose to be 31.7 +/- 0.8 mSv for neutron and 4.2 +/- 0.2 mSv for photon for 10 mins; whole body effective dose was calculated conservatively to be 0.052 mSv. Experimental values closely match values obtained from MCNP6 simulations. These are acceptable doses to apply the technology for a manganese toxicity study in a human population.

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

    PubMed

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

    2015-12-01

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

  2. SWP Echelle Spectra of Chromospherically Active Dwarf Stars

    NASA Astrophysics Data System (ADS)

    Ayres, Thomas R.

    High resolution spectra of the 1150-2000 A region are enormously valuable for probing outer- atmosphere structure in cool stars. For example, such data can be used to separate blends, identify individual emission components in short-period binary systems, determine intensity ratios in close multiplets, estimate reliable emission strengths of lines superimposed on bright stellar continua, and test for the presence or absence of stellar winds at 105 K temperatures. These possibilities are not practical with IUE low-dispersion spectra. However, one must pay a steep-price to obtain useable high-dispersion IUE spectra and the additional dimension of diagnostic information, namely only a handful of the brightest UV sources are accessible even with shift-long exposures. We propose below an observing program to obtain echelle spectra of chromospherically active dwarf stars in the 1150-2000 A shortwavelength region. This program is intended to explore a particular class of objects that heretofore have not been observed at high dispersion with the SWP camera. Futhermore, this program complements previous SWP echelle studies by our group at the University of Colorado of quiet-chromosphere dwarf stars (alpha Cen A, alpha Cen B), active giants (alpha Aur A, lambda And, beta Dra), and the extreme case of the very active RS CVn-type system HR 1099. As described below, highdispersion spectra of these targets have provided a critical interpretive dimension that was lacking in previous low-dispersion studies. However, several fundamental questions have been raised in the course of our exploratory SWP work on what, in practice, are two distinct classes of chromospheric stars: the quiet dwarfs and the active giants. We feel that many of these questions can be answered by bridging the interpretive gap with a careful study of the active dwarfs. Our recent experience with shift-long SWP echelle exposures of chromospheric emission stars has suggested that our previous estimates of

  3. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    SciTech Connect

    Hatarik, R. Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Mcnaney, J. M.; Munro, D. H.; Knauer, J. P.

    2015-11-14

    Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + {sup 3}He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (T{sub ion}) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent T{sub ion}, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT T{sub ion} of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for T{sub ion} and 10% for the neutron yield.

  4. Analysis of the neutron time-of-flight spectra from inertial confinement fusion experiments

    NASA Astrophysics Data System (ADS)

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; Phillips, T.; Eckart, M. J.; Bond, E. J.; Cerjan, C.; Grim, G. P.; Hartouni, E. P.; Knauer, J. P.; Mcnaney, J. M.; Munro, D. H.

    2015-11-01

    Neutron time-of-flight diagnostics have long been used to characterize the neutron spectrum produced by inertial confinement fusion experiments. The primary diagnostic goals are to extract the d + t → n + α (DT) and d + d → n + 3He (DD) neutron yields and peak widths, and the amount DT scattering relative to its unscattered yield, also known as the down-scatter ratio (DSR). These quantities are used to infer yield weighted plasma conditions, such as ion temperature (Tion) and cold fuel areal density. We report on novel methodologies used to determine neutron yield, apparent Tion, and DSR. These methods invoke a single temperature, static fluid model to describe the neutron peaks from DD and DT reactions and a spline description of the DT spectrum to determine the DSR. Both measurements are performed using a forward modeling technique that includes corrections for line-of-sight attenuation and impulse response of the detection system. These methods produce typical uncertainties for DT Tion of 250 eV, 7% for DSR, and 9% for the DT neutron yield. For the DD values, the uncertainties are 290 eV for Tion and 10% for the neutron yield.

  5. Neutrons and Granite: Transport and Activation

    SciTech Connect

    Bedrossian, P J

    2004-04-13

    In typical ground materials, both energy deposition and radionuclide production by energetic neutrons vary with the incident particle energy in a non-monotonic way. We describe the overall balance of nuclear reactions involving neutrons impinging on granite to demonstrate these energy-dependencies. While granite is a useful surrogate for a broad range of soil and rock types, the incorporation of small amounts of water (hydrogen) does alter the balance of nuclear reactions.

  6. PHITS simulations of absorbed dose out-of-field and neutron energy spectra for ELEKTA SL25 medical linear accelerator

    NASA Astrophysics Data System (ADS)

    Puchalska, Monika; Sihver, Lembit

    2015-06-01

    Monte Carlo (MC) based calculation methods for modeling photon and particle transport, have several potential applications in radiotherapy. An essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized. It is also essential to minimize the dose to radiosensitive and critical organs. With MC technique, the dose distributions from both the primary and scattered photons can be calculated. The out-of-field radiation doses are of particular concern when high energy photons are used, since then neutrons are produced both in the accelerator head and inside the patients. Using MC technique, the created photons and particles can be followed and the transport and energy deposition in all the tissues of the patient can be estimated. This is of great importance during pediatric treatments when minimizing the risk for normal healthy tissue, e.g. secondary cancer. The purpose of this work was to evaluate 3D general purpose PHITS MC code efficiency as an alternative approach for photon beam specification. In this study, we developed a model of an ELEKTA SL25 accelerator and used the transport code PHITS for calculating the total absorbed dose and the neutron energy spectra infield and outside the treatment field. This model was validated against measurements performed with bubble detector spectrometers and Boner sphere for 18 MV linacs, including both photons and neutrons. The average absolute difference between the calculated and measured absorbed dose for the out-of-field region was around 11%. Taking into account a simplification for simulated geometry, which does not include any potential scattering materials around, the obtained result is very satisfactorily. A good agreement between the simulated and measured neutron energy spectra was observed while comparing to data found in the literature.

  7. PHITS simulations of absorbed dose out-of-field and neutron energy spectra for ELEKTA SL25 medical linear accelerator.

    PubMed

    Puchalska, Monika; Sihver, Lembit

    2015-06-21

    Monte Carlo (MC) based calculation methods for modeling photon and particle transport, have several potential applications in radiotherapy. An essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized. It is also essential to minimize the dose to radiosensitive and critical organs. With MC technique, the dose distributions from both the primary and scattered photons can be calculated. The out-of-field radiation doses are of particular concern when high energy photons are used, since then neutrons are produced both in the accelerator head and inside the patients. Using MC technique, the created photons and particles can be followed and the transport and energy deposition in all the tissues of the patient can be estimated. This is of great importance during pediatric treatments when minimizing the risk for normal healthy tissue, e.g. secondary cancer. The purpose of this work was to evaluate 3D general purpose PHITS MC code efficiency as an alternative approach for photon beam specification. In this study, we developed a model of an ELEKTA SL25 accelerator and used the transport code PHITS for calculating the total absorbed dose and the neutron energy spectra infield and outside the treatment field. This model was validated against measurements performed with bubble detector spectrometers and Boner sphere for 18 MV linacs, including both photons and neutrons. The average absolute difference between the calculated and measured absorbed dose for the out-of-field region was around 11%. Taking into account a simplification for simulated geometry, which does not include any potential scattering materials around, the obtained result is very satisfactorily. A good agreement between the simulated and measured neutron energy spectra was observed while comparing to data found in the literature.

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

    SciTech Connect

    Murphy, T. J.

    2014-07-15

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

  9. Neutron activation studies and the effect of exercise on osteoporosis

    SciTech Connect

    Harrison, J.E.

    1984-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Laird, C. E.

    1984-01-01

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

  11. Suzaku spectra of the neutron-star low-mass X-ray binary 4U 1608-52

    NASA Astrophysics Data System (ADS)

    Lei, Yajuan; Zhang, Haotong; zhang, Yanxia

    2015-08-01

    We present the spectral analysis of the neutron-star low-mass X-ray binary 4U 1608-52 using data from four Suzaku observations in 2010 March. 4U 1608-52 is a transient atoll source, and the analyzed observations contain the “island” and “banana” states, corresponding transitional, and soft states. The spectra are fitted with the hybrid model for the soft states, which consists of two thermal components (a multicolor accretion disk and a single-temperature blackbody) plus a broken power law. The fitting results show that the continuum spectra evolve during the different states. Fe emission line is often detected in low-mass X-ray binary, however, no obviously Fe line is detected in the four observations of 4U 1608-52.

  12. Dynamics of H2 adsorbed in porous materials as revealed by computational analysis of inelastic neutron scattering spectra.

    PubMed

    Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen

    2016-06-29

    The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in porous materials. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of models and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological model. Since such an analysis is dependent on the model, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various porous materials, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational modeling can provide important and detailed insights into the molecular mechanism of H2 adsorption in porous materials. PMID:27160665

  13. Dynamics of H2 adsorbed in porous materials as revealed by computational analysis of inelastic neutron scattering spectra.

    PubMed

    Pham, Tony; Forrest, Katherine A; Space, Brian; Eckert, Juergen

    2016-06-29

    The inelastic scattering of neutrons from adsorbed H2 is an effective and highly sensitive method for obtaining molecular level information on the type and nature of H2 binding sites in porous materials. While these inelastic neutron scattering (INS) spectra of the hindered rotational and translational excitations on the adsorbed H2 contain a significant amount of information, much of this can only be reliably extracted by means of a detailed analysis of the spectra through the utilization of models and theoretical calculations. For instance, the rotational tunneling transitions observed in the INS spectra can be related to a value for the barrier to rotation for the adsorbed H2 with the use of a simple phenomenological model. Since such an analysis is dependent on the model, it is far more desirable to use theoretical methods to compute a potential energy surface (PES), from which the rotational barriers for H2 adsorbed at a particular site can be determined. Rotational energy levels and transitions for the hindered rotor can be obtained by quantum dynamics calculations and compared directly with experiment with an accuracy subject only to the quality of the theoretical PES. In this paper, we review some of the quantum and classical mechanical calculations that have been performed on H2 adsorbed in various porous materials, such as clathrate hydrates, zeolites, and metal-organic frameworks (MOFs). The principal aims of these calculations have been the interpretation of the INS spectra for adsorbed H2 along with the extraction of atomic level details of its interaction with the host. We describe calculations of the PES used for two-dimensional quantum rotation as well as rigorous five-dimensional quantum coupled translation-rotation dynamics, and demonstrate that the combination of INS measurements and computational modeling can provide important and detailed insights into the molecular mechanism of H2 adsorption in porous materials.

  14. Thermal neutron imaging in an active interrogation environment

    SciTech Connect

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

    2009-03-10

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

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

    NASA Technical Reports Server (NTRS)

    Laird, C. E.

    1984-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  17. Planetary Geochemistry Using Active Neutron and Gamma Ray Instrumentation

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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,

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

    SciTech Connect

    Reedy, Robert; Frankle, S. C.

    2001-01-01

    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.

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

    SciTech Connect

    Barnes, C.W.; Larson, A.R.; LeMunyan, G.; Loughlin, M.J.

    1994-05-05

    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 {plus_minus}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) {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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  1. In vivo neutron activation facility at Brookhaven National Laboratory

    SciTech Connect

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

    1997-11-01

    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.

  2. The development of an optimized neutron proportional counter for fission spectra

    NASA Astrophysics Data System (ADS)

    Millett, Marshall Geary

    Some of the materials used to make a nuclear weapon (isotopes of uranium and plutonium) are inherently unstable and undergo radioactive decay, including spontaneous fission. This spontaneous fission results in the generation of high energy neutrons that will likely escape the nuclear device. Since neutrons in the fission energy range are not common in the environment and are relatively difficult to shield, the detection of fission neutrons is useful for arms control applications such as illicit material detection or nuclear weapon treaty verification. Although neutron detectors are currently available (and utilized) for such applications, they either are excessively heavy or have low counting efficiency. This research effort comprises the development of an optimized neutron detector and is unique in that both weight and counting efficiency have been optimized for the detection of fission neutrons. The difficulty of this optimization process lies in the fact that detector weight and counting efficiency are mutually dependent. This dissertation presents the research and conclusions that lead to the optimized design, including calculations, computer modeling, model validation, and laboratory verification. Computer modeling was conducted using the MCNP (Monte Carlo N Particle) neutron transport code. For model validation and laboratory verification, a special cylindrical detector was built, called the "USNA detector," which allowed for the changing of fill gas composition and pressure as well as moderator thickness. Using this detector, experimental data were collected in order to test the effectiveness of various fill gas combinations and to provide a benchmark for the computer code. After validating computer generated results, the development of an optimized detector design proceeded by use of computer modeling. This dissertation first presents background information and initial design considerations used to determine detector and moderator candidates. The

  3. Detector-Response Correction of Two-Dimensional γ -Ray Spectra from Neutron Capture

    SciTech Connect

    Rusev, G.; Jandel, M.; Arnold, C. W.; Bredeweg, T. A.; Couture, A.; Mosby, S. M.; Ullmann, J. L.

    2015-05-28

    The neutron-capture reaction produces a large variety of γ-ray cascades with different γ-ray multiplicities. A measured spectral distribution of these cascades for each γ-ray multiplicity is of importance to applications and studies of γ-ray statistical properties. The DANCE array, a 4π ball of 160 BaF2 detectors, is an ideal tool for measurement of neutron-capture γ-rays. The high granularity of DANCE enables measurements of high-multiplicity γ-ray cascades. The measured two-dimensional spectra (γ-ray energy, γ-ray multiplicity) have to be corrected for the DANCE detector response in order to compare them with predictions of the statistical model or use them in applications. The detector-response correction problem becomes more difficult for a 4π detection system than for a single detector. A trial and error approach and an iterative decomposition of γ-ray multiplets, have been successfully applied to the detector-response correction. Applications of the decomposition methods are discussed for two-dimensional γ-ray spectra measured at DANCE from γ-ray sources and from the 10B(n, γ) and 113Cd(n, γ) reactions.

  4. Comparison of pka energy spectra, gas-atom production and damage energy deposition in neutron irradiation at various facilities

    NASA Astrophysics Data System (ADS)

    Nishiguchi, R.; Shimomura, Y.; Hahn, P. A.; Guinan, M. W.; Kiritani, M.

    1991-03-01

    By dividing neutron-energy spectrum into four energy groups, (I) <10 eV, (II) 10 eV to 0.1 MeV, (III) 0.1 MeV to 10 MeV and (IV) > 10 MeV, contributions to damage parameters (PKA spectrum, damage energy and gas-atom production) from each of the energy group were calculated for neutron irradiations at various facilities with the SPECTER code developed by Greenwood and Smither [1]. The normalized PKA spectra and the gas-atom productions were compared to examine differences in damage parameters. Such comparisons were carried out among (1) irradiations at various positions in different fission reactors (i.e. KUR, JOYO and FFTF-MOTA), and among (2) those at various fission reactors. Damage parameters were also calculated at STARFIRE fusion reactor and RTNS-II. A possible method to correlate damages at different fission reactors is discussed. It is suggested that damages in fusion reactor can be simulated by the superposition of irradiations with fission and D-T neutrons.

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

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  7. Addressing Different Active Neutron Interrogation Signatures from Fissionable Material

    SciTech Connect

    D. L. Chichester; E. H. Seabury

    2009-10-01

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

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

    SciTech Connect

    Roesler, Stefan

    2002-09-19

    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.

  9. 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)

    Roesler, S.

    2002-05-01

    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.

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

    SciTech Connect

    Roesler, Stefan

    2002-05-06

    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.

  11. Recent re-measurement of neutron and gamma-ray spectra 1080 meters from the APRD (Army Pulse Radiation Division) critical facility

    NASA Astrophysics Data System (ADS)

    Robitaille, H. A.; Hoffarth, B. E.

    1984-01-01

    Previously reported measurements of long-range air-transported neutron and gamma-ray spectra from the fast-critical facility at the US Army Aberdeen Proving Ground have been supplemented recently at the 1080-meter position. The results of these determinations are presented herein and compared to several recent calculations from other research establishments. In addition, a summary of all dosimetric measurements obtained in the period 1979-1982 are appended, as are new determinations of APRD soil composition. Integral quantities such as neutron and gamma-ray kermas are very well predicted by the latest calculations, however there still exist significant spectral differences. At short ranges calculated neutron spectra are somewhat softer than experimental measurements, but at the farthest range of 1080 meters agreement is surprisingly good. Gamma-ray spectra remain well-calculated at all ranges.

  12. Herschel/SPIRE Submillimeter Spectra of Local Active Galaxies

    NASA Astrophysics Data System (ADS)

    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

    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.

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

    PubMed

    Tomás, M; Fernández, F; Bakali, M; Muller, H

    2004-01-01

    The MITOM code was developed at UAB (Universitat Autònoma 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.

  14. Approximations for neutron emission spectra from proton collisions between 20 and 500 MeV on nuclei of A greater than or equal to 12

    NASA Technical Reports Server (NTRS)

    Burrell, M. O.

    1973-01-01

    When high energy protons from solar proton events or trapped radiation belts impinge on spacecraft structures, secondary particles are emitted. The most pernicious secondaries, from either a biological or physical standpoint, are the cascade and evaporation neutrons because of their reaction with matter leading to radioactive materials in the spacecraft structures. Empirically determined cascade and evaporation neutron emission spectra for protons of energy between 20 and 500 MeV incident on all materials at or above carbon in mass number are presented.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

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

    SciTech Connect

    Roesler, Stefan

    2002-09-24

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-05-01

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

  19. Infrared Spectra and Hydrogen Bonds of Biologically Active Benzaldehydes

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    SciTech Connect

    Meadows, J.W.

    1991-11-01

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

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

    SciTech Connect

    Meadows, J.W.

    1991-11-01

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

  3. 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)

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

    2002-01-01

    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.

  4. Validation of the MCNP computational model for neutron flux distribution with the neutron activation analysis measurement

    NASA Astrophysics Data System (ADS)

    Tiyapun, K.; Chimtin, M.; Munsorn, S.; Somchit, S.

    2015-05-01

    The objective of this work is to demonstrate the method for validating the predication of the calculation methods for neutron flux distribution in the irradiation tubes of TRIGA research reactor (TRR-1/M1) using the MCNP computer code model. The reaction rate using in the experiment includes 27Al(n, α)24Na and 197Au(n, γ)198Au reactions. Aluminium (99.9 wt%) and gold (0.1 wt%) foils and the gold foils covered with cadmium were irradiated in 9 locations in the core referred to as CT, C8, C12, F3, F12, F22, F29, G5, and G33. The experimental results were compared to the calculations performed using MCNP which consisted of the detailed geometrical model of the reactor core. The results from the experimental and calculated normalized reaction rates in the reactor core are in good agreement for both reactions showing that the material and geometrical properties of the reactor core are modelled very well. The results indicated that the difference between the experimental measurements and the calculation of the reactor core using the MCNP geometrical model was below 10%. In conclusion the MCNP computational model which was used to calculate the neutron flux and reaction rate distribution in the reactor core can be used for others reactor core parameters including neutron spectra calculation, dose rate calculation, power peaking factors calculation and optimization of research reactor utilization in the future with the confidence in the accuracy and reliability of the calculation.

  5. MAGNETIC HELICITY AND ENERGY SPECTRA OF A SOLAR ACTIVE REGION

    SciTech Connect

    Zhang, Hongqi; Brandenburg, Axel; Sokoloff, D. D.

    2014-04-01

    We compute for the first time the magnetic helicity and energy spectra of the solar active region NOAA 11158 during 2011 February 11-15 at 20° southern heliographic latitude using observational photospheric vector magnetograms. We adopt the isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field. The sign of the magnetic helicity turns out to be predominantly positive at all wavenumbers. This sign is consistent with what is theoretically expected for the southern hemisphere. The magnetic helicity normalized to its theoretical maximum value, here referred to as relative helicity, is around 4% and strongest at intermediate wavenumbers of k ≈ 0.4 Mm{sup –1}, corresponding to a scale of 2π/k ≈ 16 Mm. The same sign and a similar value are also found for the relative current helicity evaluated in real space based on the vertical components of magnetic field and current density. The modulus of the magnetic helicity spectrum shows a k {sup –11/3} power law at large wavenumbers, which implies a k {sup –5/3} spectrum for the modulus of the current helicity. A k {sup –5/3} spectrum is also obtained for the magnetic energy. The energy spectra evaluated separately from the horizontal and vertical fields agree for wavenumbers below 3 Mm{sup –1}, corresponding to scales above 2 Mm. This gives some justification to our assumption of isotropy and places limits resulting from possible instrumental artifacts at small scales.

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

    NASA Astrophysics Data System (ADS)

    Frenje, J. A.; Casey, D. T.; Li, C. K.; Séguin, F. H.; Petrasso, R. D.; Glebov, V. Yu.; Radha, P. B.; Sangster, T. C.; Meyerhofer, D. D.; Hatchett, S. P.; Haan, S. W.; Cerjan, C. J.; Landen, O. L.; Fletcher, K. A.; Leeper, R. J.

    2010-05-01

    For the first time high areal-density (ρR) cryogenic deuterium-tritium (DT) implosions have been probed using downscattered neutron spectra measured with the magnetic recoil spectrometer (MRS) [J. A. Frenje et al., Rev. Sci. Instrum. 79, 10E502 (2008)], recently installed and commissioned on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The ρR data obtained with the MRS have been essential for understanding how the fuel is assembled and for guiding the cryogenic program at the Laboratory for Laser Energetics (LLE) to ρR values up to ˜300 mg/cm2. The ρR data obtained from well-established charged particle spectrometry techniques [C. K. Li et al., Phys. Plasmas 8, 4902 (2001)] were used to authenticate the MRS data for low-ρR plastic capsule implosions, and the ρR values inferred from these techniques are in excellent agreement, indicating that the MRS technique provides high-fidelity data. Recent OMEGA-MRS data and Monte Carlo simulations have shown that the MRS on the NIF [G. H. Miller et al., Nucl. Fusion 44, S228 (2004)] will meet most of the absolute and relative requirements for determining ρR, ion temperature (Ti) and neutron yield (Yn) in both low-yield, tritium-rich, deuterium-lean, hydrogen-doped implosions and high-yield DT implosions.

  7. Neutron activation analysis for antimetabolites. [in food samples

    NASA Technical Reports Server (NTRS)

    1973-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Zhuk, L. I.; Kist, A. A.

    1999-01-01

    Neutron activation analysis is an outstanding analytical method having very wide applications in various fields. Analysis of human hair within last decades mostly based on neutron activation analysis is a very attractive illustration of the application of nuclear analytical techniques. Very interesting question is how the elemental composition differs in different areas or cities. In this connection the present paper gives average data and maps of various localities in the vicinity of drying-out Aral Sea and of various industrial cities in Central Asia.

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

    NASA Astrophysics Data System (ADS)

    Holmes, Jesse Curtis

    Nuclear data libraries provide fundamental reaction information required by nuclear system simulation codes. The inclusion of data covariances in these libraries allows the user to assess uncertainties in system response parameters as a function of uncertainties in the nuclear data. Formats and procedures are currently established for representing covariances for various types of reaction data in ENDF libraries. This covariance data is typically generated utilizing experimental measurements and empirical models, consistent with the method of parent data production. However, ENDF File 7 thermal neutron scattering library data is, by convention, produced theoretically through fundamental scattering physics model calculations. Currently, there is no published covariance data for ENDF File 7 thermal libraries. Furthermore, no accepted methodology exists for quantifying or representing uncertainty information associated with this thermal library data. The quality of thermal neutron inelastic scattering cross section data can be of high importance in reactor analysis and criticality safety applications. These cross sections depend on the material's structure and dynamics. The double-differential scattering law, S(alpha, beta), tabulated in ENDF File 7 libraries contains this information. For crystalline solids, S(alpha, beta) is primarily a function of the material's phonon density of states (DOS). Published ENDF File 7 libraries are commonly produced by calculation and processing codes, such as the LEAPR module of NJOY, which utilize the phonon DOS as the fundamental input for inelastic scattering calculations to directly output an S(alpha, beta) matrix. To determine covariances for the S(alpha, beta) data generated by this process, information about uncertainties in the DOS is required. The phonon DOS may be viewed as a probability density function of atomic vibrational energy states that exist in a material. Probable variation in the shape of this spectrum may be

  10. Shape of spectra and mean energies of prompt fission neutrons from {sup 237}Np fission induced by primary neutrons of energy in the range E{sub n} < 20 MeV

    SciTech Connect

    Svirin, M. I.

    2008-10-15

    An analysis of the spectrum of prompt neutrons originating from {sup 237}Np fission induced by primary neutrons of energy E{sub n} = 14.7 MeV confirms the results obtained previously for {sup 232}Th (E{sub n} = 14.7, 17.7 MeV), {sup 235}U (14.7 MeV), and {sup 238}U (13.2, 14.7, 16, and 17.7 MeV) nuclei. In the experimental spectrum measured in the emissive fission of {sup 237}Np, there is also an excess of soft neutrons in the energy range E < 2 MeV in relation to what follows from a traditional theoretical description that considers two sources of prompt fission neutrons: fully accelerated fission fragments and excited nuclei prior to their separation. In just the same way as in the cases of {sup 232}Th and {sup 235,238}U, the shape of the prompt-fission-neutron spectrum for {sup 237}Np is reproduced theoretically over the entire measured range of secondary-neutron energies upon including nonaccelerated fragments as a third source of neutrons in the computational scheme. A description of the spectra and mean energies of prompt fission neutrons versus the bombarding-neutron energy is obtained on the basis of experimental data and their analysis. The results on mean energies are compared with data on the proton-induced fission of {sup 236,238}U nuclei.

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

    SciTech Connect

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

    1996-09-01

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

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

    USGS Publications Warehouse

    Devine, T.; Peterle, T.J.

    1968-01-01

    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.

  13. Vibrational spectra and antimicrobial activity of selected bivalent cation benzoates

    NASA Astrophysics Data System (ADS)

    Borawska, M. H.; Koczoń, P.; Piekut, J.; Świsłocka, R.; Lewandowski, W.

    2009-02-01

    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.

  14. Triton burnup measurements in KSTAR using a neutron activation system

    NASA Astrophysics Data System (ADS)

    Jo, Jungmin; Cheon, MunSeong; Kim, Jun Young; Rhee, T.; Kim, Junghee; Shi, Yue-Jiang; Isobe, M.; Ogawa, K.; Chung, Kyoung-Jae; Hwang, Y. S.

    2016-11-01

    Measurements of the time-integrated triton burnup for deuterium plasma in Korea Superconducting Tokamak Advanced Research (KSTAR) have been performed following the simultaneous detection of the d-d and d-t neutrons. The d-d neutrons were measured using a 3He proportional counter, fission chamber, and activated indium sample, whereas the d-t neutrons were detected using activated silicon and copper samples. The triton burnup ratio from KSTAR discharges is found to be in the range 0.01%-0.50% depending on the plasma conditions. The measured burnup ratio is compared with the prompt loss fraction of tritons calculated with the Lorentz orbit code and the classical slowing-down time. The burnup ratio is found to increase as plasma current and classical slowing-down time increase.

  15. ACTIV: Sandwich Detector Activity from In-Pile Slowing-Down Spectra Experiment

    SciTech Connect

    2013-08-01

    ACTIV calculates the activities of a sandwich detector, to be used for in-pile measurements in slowing-down spectra below a few keV. The effect of scattering with energy degradation in the filter and in the detectors has been included to a first approximation.

  16. BOREHOLE NEUTRON ACTIVATION: THE RARE EARTHS.

    USGS Publications Warehouse

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

    1987-01-01

    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.

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

    SciTech Connect

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

    1984-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    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.

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

    SciTech Connect

    Knapp, P. F.; Sinars, D. B.; Hahn, K. D.

    2013-06-15

    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.

  20. SU-E-T-543: Measurement of Neutron Activation From Different High Energy Varian Linear Accelerators

    SciTech Connect

    Thatcher, T; Madsen, S; Sudowe, R; Meigooni, A Soleimani

    2015-06-15

    Purpose: Linear accelerators producing photons above 10 MeV may induce photonuclear reactions in high Z components of the accelerator. These liberated neutrons can then activate the structural components of the accelerator and other materials in the beam path through neutron capture reactions. The induced activity within the accelerator may contribute to additional dose to both patients and personnel. This project seeks to determine the total activity and activity per activated isotope following irradiation in different Varian accelerators at energies above 10 MeV. Methods: A Varian 21IX accelerator was used to irradiate a 30 cm × 30 cm × 20 cm solid water phantom with 15 MV x-rays. The phantom was placed at an SSD of 100 cm and at the center of a 20 cm × 20 cm field. Activation induced gamma spectra were acquired over a 5 minute interval after 1 and 15 minutes from completion of the irradiation. All measurements were made using a CANBERRA Falcon 5000 Portable HPGe detector. The majority of measurements were made in scattering geometry with the detector situated at 90° to the incident beam, 30 cm from the side of the phantom and approximately 10 cm from the top. A 5 minute background count was acquired and automatically subtracted from all subsequent measurements. Photon spectra were acquired for both open and MLC fields. Results: Based on spectral signatures, nuclides have been identified and their activities calculated for both open and MLC fields. Preliminary analyses suggest that activities from the activation products in the microcurie range. Conclusion: Activation isotopes have been identified and their relative activities determined. These activities are only gross estimates since efficiencies have not been determined for this source-detector geometry. Current efforts are focused on accurate determination of detector efficiencies using Monte Carlo calculations.

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

    SciTech Connect

    Khorasanov, G. L.; Blokhin, A. I.

    2012-07-01

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

  2. Active Interrogation of Sensitive Nuclear Material Using Laser Driven Neutron Beams

    SciTech Connect

    Favalli, Andrea; Roth, Markus

    2015-05-01

    An investigation of the viability of a laser-driven neutron source for active interrogation is reported. The need is for a fast, movable, operationally safe neutron source which is energy tunable and has high-intensity, directional neutron production. Reasons for the choice of neutrons and lasers are set forth. Results from the interrogation of an enriched U sample are shown.

  3. Status report of CPHS and neutron activities at Tsinghua University

    NASA Astrophysics Data System (ADS)

    Wang, X.; Xing, Q.; Zheng, S.; Yang, Y.; Gong, H.; Xiao, Y.; Wu, H.; Guan, X.; Du, T.

    2016-11-01

    The Compact Pulsed Hadron Source (CPHS) project that was launched in September 2009 at Tsinghua University has reached a first commissioning stage in conjunction with ongoing activities to fulfill the eventual design goal of a ˜ 1013 n/s epithermal-to-cold neutron yield for education, instrumentation development, and industrial applications. Here, we report the latest progress on the commissioning and applications of 3MeV proton and neutron beam lines in the last one and half years, and the design, fabrication, engineering of the 13MeV/16kW proton accelerator system.

  4. Active helium target: Neutron scalar polarizability extraction via Compton scattering

    SciTech Connect

    Morris, Meg Hornidge, David; Annand, John; Strandberg, Bruno

    2015-12-31

    Precise measurement of the neutron scalar polarizabilities has been a lasting challenge because of the lack of a free-neutron target. Led by the University of Glasgow and the Mount Allison University groups of the A2 collaboration in Mainz, Germany, preparations have begun to test a recent theoretical model with an active helium target with the hope of determining these elusive quantities with small statistical, systematic, and model-dependent errors. Apparatus testing and background-event simulations have been carried out, with the full experiment projected to run in 2015. Once determined, these values can be applied to help understand quantum chromodynamics in the nonperturbative region.

  5. Detection sensitivities in 3-8 MeV neutron activation

    NASA Technical Reports Server (NTRS)

    Wahlgren, M. A.; Wing, J.

    1968-01-01

    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.

  6. BNL Activities in Advanced Neutron Source Development: Past and Present

    SciTech Connect

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

    1998-06-14

    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.

  7. BNL ACTIVITIES IN ADVANCED NEUTRON SOURCE DEVELOPMENT: PAST AND PRESENT

    SciTech Connect

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

    1998-06-14

    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.

  8. Neutron activation analysis; A sensitive test for trace elements

    SciTech Connect

    Hossain, T.Z. . Ward Lab.)

    1992-01-01

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

  9. Prototyping an Active Neutron Veto for SuperCDMS

    SciTech Connect

    Calkins, Robert; Loer, Ben

    2015-08-17

    Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results from our R&D and prototyping efforts.

  10. Prototyping an active neutron veto for SuperCDMS

    SciTech Connect

    Calkins, Robert; Loer, Ben

    2015-08-17

    Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results from our R&D and prototyping efforts.

  11. Prototyping an active neutron veto for SuperCDMS

    NASA Astrophysics Data System (ADS)

    Calkins, Robert; Loer, Ben

    2015-08-01

    Neutrons, originating cosmogenically or from radioactive decays, can produce signals in dark matter detectors that are indistinguishable from Weakly Interacting Massive Particles (WIMPs). To combat this background for the SuperCDMS SNOLAB experiment, we are investigating designs for an active neutron veto within the constrained space of the compact SuperCDMS passive shielding. The current design employs an organic liquid scintillator mixed with an agent to enhance thermal neutron captures, with the scintillation light collected using wavelength-shifting fibers and read out by silicon photo-multipliers. We will describe the proposed veto and its predicted efficiency in detail and give some recent results from our R&D and prototyping efforts.

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

    PubMed

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

    2014-12-01

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

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

    SciTech Connect

    Vaknin, David; Demmel, Franz

    2014-05-01

    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.

  14. Active Interrogation Using Electronic Neutron Generators for Nuclear Safeguards Applications

    SciTech Connect

    Chichester, D. L.; Seabury, E. H.

    2009-03-10

    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.

  15. Active Interrogation Using Electronic Neutron Generators for Nuclear Safeguards Applications

    SciTech Connect

    David L. Chichester; Edward H. Seabury

    2008-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2001-06-01

    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, Ba and La are less precise. Curves showing correlation between Al and Mg concentrations are given for different sites.

  17. 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)

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

    2003-05-01

    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.

  18. Synthesis, characterization, and neutron activation of holmium metallofullerenes

    SciTech Connect

    Cagle, D.W.; Thrash, T.P.; Wilson, L.J.; Alford, M.; Chibante, L.P.F.; Ehrhardt, G.J.

    1996-08-28

    Isolation of the first macroscopic quantities of endohedral holmium metallofullerenes (principally Ho@C{sub 82}, Ho{sub 2}@C{sub 82}, and Ho{sub 3}@C{sub 82} by LD-TOF mass spectrometry) has been accomplished by carbon-arc and preparative HPLC methodologies. The detailed procedure for production and isolation of the metallofullerenes includes a new technique whereby holmium-impregnated electrodes are prepared simply by soaking porous graphite rods in an ethanolic solution of Ho(NO{sub 3}){sub 3}.xH{sub 2}O. Monoisotopic {sup 165}Ho offers a unique combination of advantages for neutron-activation studies of metallofullerenes, and purified samples containing {sup 165}Ho@C{sub 82}, {sup 165}Ho{sub 2}@C{sub 82}, and {sup 165}Ho{sub 3}@C{sub 82} have been activated by high-flux neutron irradiation ({Phi} = 4 x 10{sup 13}n cm{sup -2} s{sup -1}) to generate {sup 166}Ho metallofullerenes, which undergo {beta}{sup -} decay to produce stable {sup 166}Er. Chemical workup of the irradiated samples, followed by re-irradiation, has been used to demonstrate that observed decomposition of holmium metallofullerenes is due mainly to `fast` neutron damage rather than to holmium atom nuclear recoil (E{sub max} = 200 eV). This implies that metallofullerene damage can be minimized by using neutron fluxes with the highest possible thermal component. 60 refs., 4 figs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    The Large Hadron Collider forward (LHCf) experiment is designed to use the LHC to verify the hadronic-interaction models used in cosmic-ray physics. Forward baryon production is one of the crucial points to understand the development of cosmic-ray showers. We report the neutron-energy spectra for LHC √{ s} = 7 TeV proton-proton collisions with the pseudo-rapidity η ranging from 8.81 to 8.99, from 8.99 to 9.22, and from 10.76 to infinity. The measured energy spectra obtained from the two independent calorimeters of Arm1 and Arm2 show the same characteristic feature before unfolding the detector responses. We unfolded the measured spectra by using the multidimensional unfolding method based on Bayesian theory, and the unfolded spectra were compared with current hadronic-interaction models. The QGSJET II-03 model predicts a high neutron production rate at the highest pseudo-rapidity range similar to our results, and the DPMJET 3.04 model describes our results well at the lower pseudo-rapidity ranges. However, no model perfectly explains the experimental results over the entire pseudo-rapidity range. The experimental data indicate a more abundant neutron production rate relative to the photon production than any model predictions studied here.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  1. 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.

    PubMed

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

    2006-02-01

    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. PMID:16532941

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

    NASA Astrophysics Data System (ADS)

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

    2008-01-01

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

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

    SciTech Connect

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

    2009-06-09

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

  4. Diagnostic Application of Absolute Neutron Activation Analysis in Hematology

    SciTech Connect

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

    2004-10-03

    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.

  5. Determination of indium in standard rocks by neutron activation analysis.

    PubMed

    Johansen, O; Steinnes, E

    1966-08-01

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

  6. Obsidian sources characterized by neutron-activation analysis.

    PubMed

    Gordus, A A; Wright, G A; Griffin, J B

    1968-07-26

    Concentrations of elements such as manganese, scandium, lanthanum, rubidium, samarium, barium, and zirconium in obsidian samples from different flows show ranges of 1000 percent or more, whereas the variation in element content in obsidian samples from a single flow appears to be less than 40 percent. Neutron-activation analysis of these elements, as well as of sodium and iron, provides a means of identifying the geologic source of an archeological artifact of obsidian.

  7. Determination of indium in standard rocks by neutron activation analysis.

    PubMed

    Johansen, O; Steinnes, E

    1966-08-01

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

  8. The affect of industrial activities on zinc in alluvial Egyptian soil determined using neutron activation analysis.

    PubMed

    Abdel-Sabour, M F; Abdel-Basset, N

    2002-07-01

    Thirty-two surface (0-20 cm) soil samples were collected from different locations in Egypt representing non-polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Zn content in alluvial soils of Nile Delta in Egypt by using the delayed neutron activation analysis technique (DNAA), in the irradiation facilities of the first Egyptian research reactor (ET-RR-1). The gamma-ray spectra were recorded with a hyper pure germanium detection system. The well resolved gamma-ray peak at 1116.0 keV was efficiently used for 65Zn content determination. Zn content in non-polluted soil samples ranged between 74.1 and 103.8 ppm with an average of 98.5 +/- 5.1 ppm. Zn content in moderately polluted soils ranged between 136.0 and 232.5 ppm with an average of 180.1 +/- 32.6 ppm. The highest Zn levels ranging from 240.0 and 733.0 ppm with an average of 410.3 +/- 54.4 ppm, were observed in soil samples collected from, either highly polluted agricultural soils exposed to prolonged irrigation with industrial wastewater or surface soil samples from industrial sites. PMID:12211982

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

    SciTech Connect

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

    2006-08-14

    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.

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

    PubMed Central

    Vincent, Jacques; Haumont, Stanislas; Roels, Joseph

    1965-01-01

    Longitudinal sections of human cortical bone were submitted to thermal neutrons. γ-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 γ-emitters have decayed on the 15th day. When the γ-rays have disappeared, β-rays are still produced by the sections. It was proved by the absorption curve in aluminium that all these β-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. γ-ray spectra and β-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. PMID:14286295

  11. Mercury mass measurement in fluorescent lamps via neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Viererbl, L.; Vinš, M.; Lahodová, Z.; Fuksa, A.; Kučera, J.; Koleška, M.; Voljanskij, A.

    2015-11-01

    Mercury is an essential component of fluorescent lamps. Not all fluorescent lamps are recycled, resulting in contamination of the environment with toxic mercury, making measurement of the mercury mass used in fluorescent lamps important. Mercury mass measurement of lamps via instrumental neutron activation analysis (NAA) was tested under various conditions in the LVR-15 research reactor. Fluorescent lamps were irradiated in different positions in vertical irradiation channels and a horizontal channel in neutron fields with total fluence rates from 3×108 cm-2 s-1 to 1014 cm-2 s-1. The 202Hg(n,γ)203Hg nuclear reaction was used for mercury mass evaluation. Activities of 203Hg and others induced radionuclides were measured via gamma spectrometry with an HPGe detector at various times after irradiation. Standards containing an Hg2Cl2 compound were used to determine mercury mass. Problems arise from the presence of elements with a large effective cross section in luminescent material (europium, antimony and gadolinium) and glass (boron). The paper describes optimization of the NAA procedure in the LVR-15 research reactor with particular attention to influence of neutron self-absorption in fluorescent lamps.

  12. On the self-shielding factors in neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Trkov, A.; Žerovnik, G.; Snoj, L.; Ravnik, M.

    2009-11-01

    Whenever the sample size in neutron activation analysis cannot be made small enough, self-shielding effects need to be taken into account. When several resonance absorbers are present in the sample, resonance interference must also be considered. Estimation of the self-shielding factors by the Monte Carlo technique is too cumbersome for routine application. Various simplified approaches were compared to rigorous Monte Carlo calculations, pointing out their potential limitations. Good results are obtained using self-shielding factors calculated from evaluated nuclear data libraries and tabulated as a function of the dilution cross-section. The dilution cross-section depends on the material composition and the sample dimensions through the equivalence principle, which is well known in reactor physics. Resonance interference is calculated by solving the neutron spectrum slowing-down equation from cross-sections in 640-group representation. The MATSSF code was written for the purpose and is available on request.

  13. Characterization of hydrogen in concrete by cold neutron prompt gamma-ray activation analysis and neutron incoherent scattering

    SciTech Connect

    Paul, R.L.; Chen-Mayer, H.H.; Lindstrom, R.M.; Blaauw, M.

    2000-07-01

    A combination of cold neutron prompt gamma-ray activation analysis (PGAA) and neutron incoherent scattering (NIS) has been used for nondestructive characterization of hydrogen as a function of position in slabs of wet concrete of different composition. Hydrogen was determined by PGAA by scanning each sample across of 5 mm diameter neutron beam in 10 mm increments, and measuring the 2223 keV prompt gamma ray. NIS measurements were performed by scanning the samples across a 5 mm diameter neutron beam at 5 mm increments and detecting scattered neutrons. The measurements demonstrate the feasibility of the techniques for 2D compositional mapping of hydrogen and other elements in materials, and indicate the potential of these methods for monitoring the uniformity of drying concrete.

  14. Analysis of initial in-plant active neutron multiplicity measurements

    SciTech Connect

    Ensslin, N.; Krick, M.S.; Harker, W.C.

    1993-08-01

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

  15. Measurements of neutrons at JET by means of the activation methods

    NASA Astrophysics Data System (ADS)

    Prokopowicz, R.; Bienkowska, B.; Drozdowicz, K.; Jednorog, S.; Kowalska-Strzeciwilk, E.; Murari, A.; Popovichev, S.; Pytel, K.; Scholz, M.; Szydlowski, A.; Syme, B.; Tracz, G.; JET-EFDA Contributors

    2011-05-01

    The neutron diagnostics in tokamaks like Joint European Torus (JET) are essential in estimating fusion power. The neutron activation method, supported by neutron transport calculations, is particularly useful for the evaluation of the total neutron yield from a single plasma discharge. This paper presents the results of activation experiments and calculations carried out for JET plasmas, from the selection of the activation materials to their irradiations in the neutron field of JET discharges. Neutron transport calculations were performed, leading to activation coefficients for new materials. The results of the calculations were used to design new composite samples to obtain information on both the yield and the neutron spectrum. The neutron measurements using these new activation materials were performed during the last JET experimental campaigns. The results are compared with neutron transport calculations. Additionally, application of the cadmium difference method allows revelation of the part of thermal neutrons near the tokamak first wall. The advantages of new activation materials and benchmarking the activation method against neutron transport calculations are also discussed.

  16. Coincidence Prompt Gamma-Ray Neutron Activation Analysis

    SciTech Connect

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

    2002-11-10

    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.

  17. RADSAT Benchmarks for Prompt Gamma Neutron Activation Analysis Measurements

    SciTech Connect

    Burns, Kimberly A.; Gesh, Christopher J.

    2011-07-01

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

  18. A militarily fielded thermal neutron activation sensor for landmine detection

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

    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 μg252Cf neutron source surrounded by four 7.62 cm×7.62 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.

  19. 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

    Greenwood, L.R.; Intasorn, A.

    1989-07-01

    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.

  20. Study on Prompt Fission Neutron Spectra and Associated Covariances for 235U(nth,f) and 239Pu(nth,f)

    NASA Astrophysics Data System (ADS)

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

    Prompt Fission Neutron Spectra (PFNS) are very important nuclear data for reactor neutronic calculation tools. Most of the international evaluated nuclear data libraries lie on the Madland-Nix model, which is a based on evaporation theory of fission fragments. But very scarce data can be found regarding the PFNS covariance matrix associated to these evaluations. As an illustration of the impact of the PFNS on neutronic calculations, we will show a Monte-Carlo calculation of the neutron flux received by a PWR vessel, using different PFNS evaluations. The neutrons that have the highest probability to contribute to the vessel flux are those that are emitted at the highest energies; however most of the fission neutrons are emitted around 2 MeV. These results show the necessity to have very precise PFNS evaluations, and a proper estimation of associated covariances. The estimation of the PFNS covariance matrix associated to a model, after adjustment of model parameters, will be shown. This is performed by the CONRAD code, developed at CEA Cadarache. The final goal of the study is to adjust the parameters involved in fission fragments de-excitation in the FIFRELIN Monte-Carlo code, also developed at CEA Cadarache, which computes the PFNS among other fission quantities, and to provide the associated PFNS covariance matrix. However for the moment we focused the study on three historically widely used PFNS models: Maxwellian, Watt and Madland-Nix models. The covariance matrix on the adjusted spectrum comes mainly from the systematic uncertainty on some experimental parameters - namely the normalization, background, detection efficiency, etc. In order to propagate this type of uncertainties properly, the marginalization technique is used. A close knowledge of the conditions in which a particular experimental PFNS has been measured is required, in order to have a correct estimation of the PFNS uncertainties after adjustment. In this work, we propagated the uncertainty on

  1. Neutron distribution and induced activity inside a Linac treatment room.

    PubMed

    Juste, B; Miró, R; Verdú, G; Díez, S; Campayo, J M

    2015-01-01

    Induced radioactivity and photoneutron contamination inside a radiation therapy bunker of a medical linear accelerator (Linac) is investigated in this work. The Linac studied is an Elekta Precise electron accelerator which maximum treatment photon energy is 15 MeV. This energy exceeds the photonuclear reaction threshold (around 7 MeV for high atomic number metals). The Monte Carlo code MCNP6 has been used for quantifying the neutron contamination inside the treatment room for different gantry rotation configuration. Walls activation processes have also been simulated. The approach described in this paper is useful to prevent the overexposure of patients and medical staff. PMID:26737878

  2. Neutron Activation Analysis and Product Isotope Inventory Code System.

    1990-10-31

    Version 00 NAC was designed to predict the neutron-induced gamma-ray radioactivity for a wide variety of composite materials. The NAC output includes the input data, a list of all reactions for each constituent element, and the end-of-irradiation disintegration rates for each reaction. NAC also compiles a product isotope inventory containing the isotope name, the disintegration rate, the gamma-ray source strength, and the absorbed dose rate at 1 meter from an unshielded point source. The inducedmore » activity is calculated as a function of irradiation and decay times; the effect of cyclic irradiation can also be calculated.« less

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

    NASA Astrophysics Data System (ADS)

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

    2004-01-01

    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 μg 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.

  4. Measurement of action spectra of light-activated processes

    NASA Astrophysics Data System (ADS)

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

    2006-01-01

    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.

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

    SciTech Connect

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

    2011-03-15

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

  6. Development of Monte Carlo code for coincidence prompt gamma-ray neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Han, Xiaogang

    Prompt Gamma-Ray Neutron Activation Analysis (PGNAA) offers a non-destructive, relatively rapid on-line method for determination of elemental composition of bulk and other samples. However, PGNAA has an inherently large background. These backgrounds are primarily due to the presence of the neutron excitation source. It also includes neutron activation of the detector and the prompt gamma rays from the structure materials of PGNAA devices. These large backgrounds limit the sensitivity and accuracy of PGNAA. Since most of the prompt gamma rays from the same element are emitted in coincidence, a possible approach for further improvement is to change the traditional PGNAA measurement technique and introduce the gamma-gamma coincidence technique. It is well known that the coincidence techniques can eliminate most of the interference backgrounds and improve the signal-to-noise ratio. A new Monte Carlo code, CEARCPG has been developed at CEAR to simulate gamma-gamma coincidence spectra in PGNAA experiment. Compared to the other existing Monte Carlo code CEARPGA I and CEARPGA II, a new algorithm of sampling the prompt gamma rays produced from neutron capture reaction and neutron inelastic scattering reaction, is developed in this work. All the prompt gamma rays are taken into account by using this new algorithm. Before this work, the commonly used method is to interpolate the prompt gamma rays from the pre-calculated gamma-ray table. This technique works fine for the single spectrum. However it limits the capability to simulate the coincidence spectrum. The new algorithm samples the prompt gamma rays from the nucleus excitation scheme. The primary nuclear data library used to sample the prompt gamma rays comes from ENSDF library. Three cases are simulated and the simulated results are benchmarked with experiments. The first case is the prototype for ETI PGNAA application. This case is designed to check the capability of CEARCPG for single spectrum simulation. The second

  7. Activation of cobalt by neutrons from the Hiroshima bomb

    SciTech Connect

    Kerr, G.D.; Dyer, F.F.; Emery, J.F.; Pace, J.V. III ); Brodzinski, R.L. ); Marcum, J. )

    1990-02-01

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

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

    SciTech Connect

    Ullmann, John Leonard; Kawano, Toshihiko; Bredeweg, Todd Allen; Baramsai, Bayarbadrakh; Couture, Aaron Joseph; Haight, Robert Cameron; Jandel, Marian; Mosby, Shea Morgan; O'Donnell, John M.; Rundberg, Robert S.; Vieira, David J.; Wilhelmy, Jerry B.; Becker, John A.; Wu, Ching-Yen; Krticka, Milan

    2015-05-28

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

  9. Spectra and Luminosities of X-Ray Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Morgan, Windsor Anthony, Jr.

    1995-01-01

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

  10. Analyses of cosmic ray induced-neutron based on spectrometers operated simultaneously at mid-latitude and Antarctica high-altitude stations during quiet solar activity

    NASA Astrophysics Data System (ADS)

    Hubert, G.

    2016-10-01

    In this paper are described a new neutron spectrometer which operate in the Concordia station (Antarctica, Dome C) since December 2015. This instrument complements a network including neutron spectrometers operating in the Pic-du-Midi and the Pico dos Dias. Thus, this work present an analysis of cosmic ray induced-neutron based on spectrometers operated simultaneously in the Pic-du-Midi and the Concordia stations during a quiet solar activity. The both high station platforms allow for investigating the long period dynamics to analyze the spectral variation and effects of local and seasonal changes, but also the short term dynamics during solar flare events. A first part is devoted to analyze the count rates, the spectrum and the neutron fluxes, implying cross-comparisons between data obtained in the both stations. In a second part, measurements analyses were reinforced by modeling based on simulations of atmospheric cascades according to primary spectra which only depend on the solar modulation potential.

  11. Epithermal Neutron Activation Analysis of the Asian Herbal Plants

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

    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.

  12. Epithermal Neutron Activation Analysis of the Asian Herbal Plants

    SciTech Connect

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

    2011-06-28

    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.

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

    PubMed

    El-Taher, A

    2007-04-01

    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.

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

    PubMed

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

    2004-01-01

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

  15. Evaluation of the Doppler-Broadening of Gamma-Ray Spectra from Neutron Inelastic Scattering on Light Nuclei

    SciTech Connect

    Womble, Phillip C.; Barzilov, Alexander; Novikov, Ivan; Howard, Joseph; Musser, Jason

    2009-03-10

    Neutron-induced gamma-ray reactions are extensively used in the nondestructive analysis of materials and other areas where the information about the chemical composition of a substance is crucial. The common technique to find the intensity of the gamma ray is to fit gamma-ray line shape with an analytical function, for example, a Gaussian. However, the Gaussian fitting may fail if the gamma-ray peak is Doppler-broadened since this leads to the miscalculation of the area of the peak and, therefore, to misidentification of the material. Due to momentum considerations, Doppler-broadening occurs primarily with gamma rays from neutron-induced inelastic scattering reactions with light nuclei. The recoiling nucleus of interest must have excited states whose lifetimes are much smaller than the time of flight in the material. We have examined various light nuclei bombarded by 14 MeV neutrons to predict when the peak shape of a neutron-induced gamma ray emitted from these nuclei will be Doppler-broadened. We have found that nearly all the gamma rays from neutron-induced gamma-ray reactions on light elements (A<20) are Doppler-broadened with only a few exceptions. This means that utilization of resolution curves derived from isotopic sources or thermal neutron capture reactions have little value in the analysis.

  16. Computed secondary-particle energy spectra following nonelastic neutron interactions with sup 12 C for E sub n between 15 and 60 MeV: Comparisons of results from two calculational methods

    SciTech Connect

    Dickens, J.K.

    1991-04-01

    The organic scintillation detector response code SCINFUL has been used to compute secondary-particle energy spectra, d{sigma}/dE, following nonelastic neutron interactions with {sup 12}C for incident neutron energies between 15 and 60 MeV. The resulting spectra are compared with published similar spectra computed by Brenner and Prael who used an intranuclear cascade code, including alpha clustering, a particle pickup mechanism, and a theoretical approach to sequential decay via intermediate particle-unstable states. The similarities of and the differences between the results of the two approaches are discussed. 16 refs., 44 figs., 2 tabs.

  17. Indirect determination of Mn-BOPP concentrations using neutron activation analysis

    SciTech Connect

    Combs, M.J.; Oveissi, C.; Mulder, R.U.; Berr, S.

    1994-12-31

    ONe aspect of neutron capture therapy (NCT) is the determination of boron levels in tissues as a function of time. The objective of this work was the development of a simple instrumental neutron activation analysis method for the indirect determination of boron. One compound studied for use in NCT was Mn-BOPP because Mn 55 will neutron activate to Mn 56 which could serve as an indicator of boron levels. In addition, it can be used as a magnetic resonance imaging agent.

  18. NE-213-scintillator-based neutron detection system for diagnostic measurements of energy spectra for neutrons having energies greater than or equal to 0.8 MeV created during plasma operations at the Princeton Tokamak Fusion Test Reactor

    NASA Astrophysics Data System (ADS)

    Dickens, J. K.; Hill, N. W.; Hou, F. S.; McConnell, J. W.; Spencer, R. R.; Tsang, F. Y.

    1985-08-01

    A system for making diagnostic measurements of the energy spectra of greater than or equal to 0.8-MeV neutrons produced during plasma operations of the Princeton Tokamak Fusion Test Reactor (TFTR) has been fabricated and tested and is presently in operation in the TFTR Test Cell Basement. The system consists of two separate detectors, each made up of cells containing liquid NE-213 scintillator attached permanently to RCA-8850 photomultiplier tubes. Pulses obtained from each photomultiplier system are amplified and electronically analyzed to identify and separate those pulses due to neutron-induced events in the detector from those due to photon-induced events in the detector. Signals from each detector are routed to two separate Analog-to-Digital Converters, and the resulting digitized information, representing: (1) the raw neutron-spectrum data; and (2) the raw photon-spectrum data, are transmited to the CICADA data-acquisition computer system of the TFTR. Software programs have been installed on the CICADA system to analyze the raw data to provide moderate-resolution recreations of the energy spectrum of the neutron and photon fluences incident on the detector during the operation of the TFTR. A complete description of, as well as the operation of, the hardware and software is given in this report.

  19. NE-213-scintillator-based neutron detection system for diagnostic measurements of energy spectra for neutrons having energies greater than or equal to 0. 8 MeV created during plasma operations at the Princeton Tokamak Fusion Test Reactor

    SciTech Connect

    Dickens, J.K.; Hill, N.W.; Hou, F.S.; McConnell, J.W.; Spencer, R.R.; Tsang, F.Y.

    1985-08-01

    A system for making diagnostic measurements of the energy spectra of greater than or equal to 0.8-MeV neutrons produced during plasma operations of the Princeton Tokamak Fusion Test Reactor (TFTR) has been fabricated and tested and is presently in operation in the TFTR Test Cell Basement. The system consists of two separate detectors, each made up of cells containing liquid NE-213 scintillator attached permanently to RCA-8850 photomultiplier tubes. Pulses obtained from each photomultiplier system are amplified and electronically analyzed to identify and separate those pulses due to neutron-induced events in the detector from those due to photon-induced events in the detector. Signals from each detector are routed to two separate Analog-to-Digital Converters, and the resulting digitized information, representing: (1) the raw neutron-spectrum data; and (2) the raw photon-spectrum data, are transmited to the CICADA data-acquisition computer system of the TFTR. Software programs have been installed on the CICADA system to analyze the raw data to provide moderate-resolution recreations of the energy spectrum of the neutron and photon fluences incident on the detector during the operation of the TFTR. A complete description of, as well as the operation of, the hardware and software is given in this report.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    USGS Publications Warehouse

    Rowe, J.J.; Steinnes, E.

    1977-01-01

    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.

  3. Unwrapping the X-ray spectra of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Reynolds, C. S.

    2016-05-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds are seen that probably affect the evolution of the host galaxy as well as regulate the feeding of the AGN itself. In this review article, we discuss how X-ray spectroscopy can be used to study each of these components. We highlight how recent measurements of the high-energy cutoff in the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are radiatively-compact and have electron temperatures regulated by electron-positron pair production. We show that the predominance of rapidly-rotating objects in current surveys of SMBH spin is entirely unsurprising once one accounts for the observational selection bias resulting from the spin-dependence of the radiative efficiency. We review recent progress in our understanding of fast (v˜ (0.1-0.3)c, highly-ionized (mainly visible in Fe XXV and Fe XXVI lines), high-column density winds that may dominate quasar-mode galactic feedback. Finally, we end with a brief look forward to the promise of Astro-H and future X-ray spectropolarimeters.

  4. A precise method to determine the activity of a weak neutron source using a germanium detector.

    PubMed

    Duke, M J M; Hallin, A L; Krauss, C B; Mekarski, P; Sibley, L

    2016-10-01

    A standard high purity germanium (HPGe) detector was used to determine the previously unknown neutron activity of a weak americium-beryllium (AmBe) neutron source. γ rays were created through (27)Al(n,n'), (27)Al(n,γ) and (1)H(n,γ) reactions induced by the neutrons on aluminum and acrylic disks, respectively. These γ rays were measured using the HPGe detector. Given the unorthodox experimental arrangement, a Monte Carlo simulation was developed to model the efficiency of the detector system to determine the neutron activity from the measured γ rays. The activity of our neutron source was determined to be 307.4±5.0n/s and is consistent for the different neutron-induced γ rays.

  5. A precise method to determine the activity of a weak neutron source using a germanium detector.

    PubMed

    Duke, M J M; Hallin, A L; Krauss, C B; Mekarski, P; Sibley, L

    2016-10-01

    A standard high purity germanium (HPGe) detector was used to determine the previously unknown neutron activity of a weak americium-beryllium (AmBe) neutron source. γ rays were created through (27)Al(n,n'), (27)Al(n,γ) and (1)H(n,γ) reactions induced by the neutrons on aluminum and acrylic disks, respectively. These γ rays were measured using the HPGe detector. Given the unorthodox experimental arrangement, a Monte Carlo simulation was developed to model the efficiency of the detector system to determine the neutron activity from the measured γ rays. The activity of our neutron source was determined to be 307.4±5.0n/s and is consistent for the different neutron-induced γ rays. PMID:27474906

  6. Active detection of shielded SNM with 60-keV neutrons

    SciTech Connect

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

    2008-07-08

    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.

  7. CHARACTERIZATION OF A THIN SILICON SENSOR FOR ACTIVE NEUTRON PERSONAL DOSEMETERS.

    PubMed

    Takada, M; Nunomiya, T; Nakamura, T; Matsumoto, T; Masuda, A

    2016-09-01

    A thin silicon sensor has been developed for active neutron personal dosemeters for use by aircrews and first responders. This thin silicon sensor is not affected by the funneling effect, which causes detection of cosmic protons and over-response to cosmic neutrons. There are several advantages to the thin silicon sensor: a decrease in sensitivity to gamma rays, an improvement of the energy detection limit for neutrons down to 0.8 MeV and an increase in the sensitivity to fast neutrons. Neutron response functions were experimentally obtained using 2.5 and 5 MeV monoenergy neutron beams and a (252)Cf neutron source. Simulation results using the Monte Carlo N-Particle transport code agree quite well with the experimental ones when an energy deposition region shaped like a circular truncated cone is used in place of a cylindrical region. PMID:27150515

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

    SciTech Connect

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

    2004-10-07

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

  9. Calculation of Raman optical activity spectra for vibrational analysis.

    PubMed

    Mutter, Shaun T; Zielinski, François; Popelier, Paul L A; Blanch, Ewan W

    2015-05-01

    By looking back on the history of Raman Optical Activity (ROA), the present article shows that the success of this analytical technique was for a long time hindered, paradoxically, by the deep level of detail and wealth of structural information it can provide. Basic principles of the underlying theory are discussed, to illustrate the technique's sensitivity due to its physical origins in the delicate response of molecular vibrations to electromagnetic properties. Following a short review of significant advances in the application of ROA by UK researchers, we dedicate two extensive sections to the technical and theoretical difficulties that were overcome to eventually provide predictive power to computational simulations in terms of ROA spectral calculation. In the last sections, we focus on a new modelling strategy that has been successful in coping with the dramatic impact of solvent effects on ROA analyses. This work emphasises the role of complementarity between experiment and theory for analysing the conformations and dynamics of biomolecules, so providing new perspectives for methodological improvements and molecular modelling development. For the latter, an example of a next-generation force-field for more accurate simulations and analysis of molecular behaviour is presented. By improving the accuracy of computational modelling, the analytical capabilities of ROA spectroscopy will be further developed so generating new insights into the complex behaviour of molecules.

  10. In-vivo neutron activation analysis: principles and clinical applications

    SciTech Connect

    Cohn, S.H.

    1982-01-01

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

  11. Clinical applications of in vivo neutron-activation analysis

    SciTech Connect

    Cohn, S.H.

    1982-01-01

    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.

  12. Tables for simplifying calculations of activities produced by thermal neutrons

    USGS Publications Warehouse

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

    1954-01-01

    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.

  13. The need for precise and well-documented experimental data on prompt fission neutron spectra from neutron-induced fission of 239Pu

    DOE PAGES

    Neudecker, Denise; Taddeucci, Terry Nicholas; Haight, Robert Cameron; Lee, Hye Young; White, Morgan Curtis; Rising, Michael Evans

    2016-01-06

    The spectrum of neutrons emitted promptly after 239Pu(n,f)—a so-called prompt fission neutron spectrum (PFNS)—is a quantity of high interest, for instance, for reactor physics and global security. However, there are only few experimental data sets available that are suitable for evaluations. In addition, some of those data sets differ by more than their 1-σ uncertainty boundaries. We present the results of MCNP studies indicating that these differences are partly caused by underestimated multiple scattering contributions, over-corrected background, and inconsistent deconvolution methods. A detailed uncertainty quantification for suitable experimental data was undertaken including these effects, and test-evaluations were performed with themore » improved uncertainty information. The test-evaluations illustrate that the inadequately estimated effects and detailed uncertainty quantification have an impact on the evaluated PFNS and associated uncertainties as well as the neutron multiplicity of selected critical assemblies. A summary of data and documentation needs to improve the quality of the experimental database is provided based on the results of simulations and test-evaluations. Furthermore, given the possibly substantial distortion of the PFNS by multiple scattering and background effects, special care should be taken to reduce these effects in future measurements, e.g., by measuring the 239Pu PFNS as a ratio to either the 235U or 252Cf PFNS.« less

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

    NASA Astrophysics Data System (ADS)

    Abyar, Fatemeh; Farrokhpour, Hossein

    2014-11-01

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

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

    SciTech Connect

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

    2014-04-15

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

  16. Application of artificial neural network in precise prediction of cement elements percentages based on the neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Eftekhari Zadeh, E.; Feghhi, S. A. H.; Roshani, G. H.; Rezaei, A.

    2016-05-01

    Due to variation of neutron energy spectrum in the target sample during the activation process and to peak overlapping caused by the Compton effect with gamma radiations emitted from activated elements, which results in background changes and consequently complex gamma spectrum during the measurement process, quantitative analysis will ultimately be problematic. Since there is no simple analytical correlation between peaks' counts with elements' concentrations, an artificial neural network for analyzing spectra can be a helpful tool. This work describes a study on the application of a neural network to determine the percentages of cement elements (mainly Ca, Si, Al, and Fe) using the neutron capture delayed gamma-ray spectra of the substance emitted by the activated nuclei as patterns which were simulated via the Monte Carlo N-particle transport code, version 2.7. The Radial Basis Function (RBF) network is developed with four specific peaks related to Ca, Si, Al and Fe, which were extracted as inputs. The proposed RBF model is developed and trained with MATLAB 7.8 software. To obtain the optimal RBF model, several structures have been constructed and tested. The comparison between simulated and predicted values using the proposed RBF model shows that there is a good agreement between them.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

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

    SciTech Connect

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

    2010-08-20

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

  20. Code System for NE-213 Unfolding of Neutron Spectra up to 100 MeV with Response Function Error Propagation.

    1987-09-30

    Version 00 The REFERDOU system can be used to calculate the response function of a NE-213 scintillation detector for energies up to 100 MeV, to interpolate and spread (Gaussian) the response function, and unfold the measured spectrum of neutrons while propagating errors from the response functions to the unfolded spectrum.

  1. Neutron background in underground particle astrophysics experiments

    SciTech Connect

    Kudryavtsev, V. A.

    2007-03-28

    Neutron background for the high-sensitivity underground particle astrophysics experiments, such as dark matter searches, double-beta decay detectors, low-energy neutrino physics and astrophysics, is discussed. Neutron production via spontaneous fission and ({alpha},n) reactions from U and Th, and by cosmic-ray muons is considered. We describe the method of calculating neutron spectra from radioactivity and effects produced in the detectors. The requirements for passive neutron shielding are given and the efficiency of an active veto system is discussed. It is shown that muon-induced neutrons require complex and accurate simulations where any simplification may lead to a significant error in the result.

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

    SciTech Connect

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

    2002-11-01

    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.

  3. Active Neutron Interrogation of Non-Radiological Materials with NMIS

    SciTech Connect

    Walker, Mark E; Mihalczo, John T

    2012-02-01

    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.

  4. Characterization of indoor cooking aerosol using neutron activation analysis

    SciTech Connect

    Wu, D.; Landsberger, S.; Larson, S. )

    1993-01-01

    Suspended particles in air are potentially harmful to human health, depending on their sizes and chemical composition. Residential indoor particles mainly come from (a) outdoor sources that are transported indoors, (b) indoor dust that is resuspended, and (c) indoor combustion sources, which include cigarette smoking, cooking, and heating. Jedrychowski stated that chronic phlegm in elderly women was strongly related to the cooking exposure. Kamens et al. indicated that cooking could generate small particles (<0.1 [mu]m), and cooking one meal could contribute [approximately]5 to 18% of total daytime particle volume exposure. Although cooking is a basic human activity, there are not many data available on the properties of particles generated by this activity. Some cooking methods, such as stir-frying and frying, which are the most favored for Chinese and other Far East people, generate a large quantity of aerosols. This research included the following efforts: 1. investigating particle number concentrations, distributions, and their variations with four different cooking methods and ventilation conditions; 2. measuring the chemical composition of cooking aerosol samples by instrumental neutron activation analysis.

  5. The role of neutron activation analysis in nutritional biomonitoring programs

    SciTech Connect

    Iyengar, V.

    1988-01-01

    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.

  6. Characterisation of neutron fields around high-energy x-ray radiotherapy machines.

    PubMed

    Králík, M; Turek, K

    2004-01-01

    Photoneutron spectra around the treatment bed of a Varian Clinac 2100C machine were measured using a Bonner sphere spectrometer. To overcome problems with pulse pile-up and detection of non-neutron-induced events, the active detector of thermal neutrons normally used at the centre of the spheres was replaced by a sandwich of four CR-39 track detectors interleaved with 10B radiators. Track densities measured for the CR-39 detectors in Bonner spheres were used for the unfolding of neutron spectra. Neutron fluence and ambient dose equivalent for the whole energy range and partial energy intervals were derived from the neutron spectra.

  7. Real-Time Active Cosmic Neutron Background Reduction Methods

    SciTech Connect

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

    2013-09-01

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

  8. Real-time active cosmic neutron background reduction methods

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  9. Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data.

    PubMed

    Bogomolov, A V; Dmitriev, A V; Myagkova, I N; Ryumin, S P; Smirnova, O N; Sobolevsky, I M

    1998-01-01

    The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles. PMID:11542904

  10. Energetic neutron and gamma-ray spectra under the earth radiation belts according to "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686" orbital complex and "CORONAS-I" satellite data.

    PubMed

    Bogomolov, A V; Dmitriev, A V; Myagkova, I N; Ryumin, S P; Smirnova, O N; Sobolevsky, I M

    1998-01-01

    The spectra of neutrons >10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex "SALYUT-7" [correction of "SALUTE-7"]-"KOSMOS-1686", are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm-2 s-1 for neutrons, 0.8 cm-2 s-1 for gamma-rays at the equator and 1.2 cm-2 s-1, 1.9 cm-2 s-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from "CORONAS-1" data are near those for albedo particles.

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

    PubMed

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

    2000-03-01

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

  12. Computer programs for absolute neutron activation analysis on the nuclear data 6620 data acquisition system

    SciTech Connect

    Wade, J.W.; Emery, J.F.

    1982-03-01

    Five computer programs that provide multielement neutron activation analysis are discussed. The software package was designed for use on the Nuclear Data 6620 Data Acquisition System and interacts with existing Nuclear Data Corporation software. The programs were developed to make use of the capabilities of the 6620 system to analyze large numbers of samples and assist in a large sample workload that had begun in the neutron activation analysis facility of the Oak Ridge Research Reactor. Nuclear Data neutron activation software is unable to perform absolute activation analysis and therefore was inefficient and inadequate for our applications.

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

    SciTech Connect

    Williams, R.E.

    1981-10-12

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

  14. Search for reaction-in-flight neutrons using thulium activation at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Grim, Gary; Rundberg, Robert; Tonchev, Anton; Fowler, Malcolm; Wilhelmy, Jerry; Archuleta, Tom; Bionta, Richard; Boswell, Mitzi; Gostic, Julie; Griego, Jeff; Knittel, Kenn; Klein, Andi; Moody, Ken; Shaughnessy, Dawn; Wilde, Carl; Yeamans, Charles

    2013-10-01

    We report on measurements of reaction-in-flight (RIF) neutrons at the National Ignition Facility. RIF neutrons are produced in cryogenically layered implision by up-scattered deuterium, or tritium ions that undergo subsequent fusion reactions. The rate of RIF neutron production is proportional to the fuel areal density (| | R) and ion-stopping length in the dense fuel assembly. Thus, RIF neutrons provide information on charge particle stopping in a strongly coupled plasma, where perturbative modeling breaks down. To measure RIF neutrons, a set of thulium activation foils was placed 50 cm from layered cryogenic implosions at the NIF. The reaction 169Tm(n,3n)167Tm has a neutron kinetic energy threshold of 14.96 MeV. We will present results from initial experiments performed during the spring of 2013. Prepared by LANL under Contract DE-AC-52-06-NA25396, TSPA, LA-UR-13-22085.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  16. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    PubMed

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel. PMID:27081973

  17. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for 235U (n ,fission) at Thermal and Fast Neutron Energies

    NASA Astrophysics Data System (ADS)

    Sonzogni, A. A.; McCutchan, E. A.; Johnson, T. D.; Dimitriou, P.

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 235U 235 fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of 86Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  18. Effects of Fission Yield Data in the Calculation of Antineutrino Spectra for ^{235}U(n,fission) at Thermal and Fast Neutron Energies.

    PubMed

    Sonzogni, A A; McCutchan, E A; Johnson, T D; Dimitriou, P

    2016-04-01

    Fission yields form an integral part of the prediction of antineutrino spectra generated by nuclear reactors, but little attention has been paid to the quality and reliability of the data used in current calculations. Following a critical review of the thermal and fast ENDF/B-VII.1 ^{235}U fission yields, deficiencies are identified and improved yields are obtained, based on corrections of erroneous yields, consistency between decay and fission yield data, and updated isomeric ratios. These corrected yields are used to calculate antineutrino spectra using the summation method. An anomalous value for the thermal fission yield of ^{86}Ge generates an excess of antineutrinos at 5-7 MeV, a feature which is no longer present when the corrected yields are used. Thermal spectra calculated with two distinct fission yield libraries (corrected ENDF/B and JEFF) differ by up to 6% in the 0-7 MeV energy window, allowing for a basic estimate of the uncertainty involved in the fission yield component of summation calculations. Finally, the fast neutron antineutrino spectrum is calculated, which at the moment can only be obtained with the summation method and may be relevant for short baseline reactor experiments using highly enriched uranium fuel.

  19. Feasibility of culvert IED detection using thermal neutron activation

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  20. Stability evaluation and correction of a pulsed neutron generator prompt gamma activation analysis system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Source output stability is important for accurate measurement in prompt gamma neutron activation. This is especially true when measuring low-concentration elements such as in vivo nitrogen (~2.5% of body weight). We evaluated the stability of the compact DT neutron generator within an in vivo nitrog...

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

    NASA Astrophysics Data System (ADS)

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

    2001-07-01

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

  2. Measurement of residual 152Eu activity induced by atomic bomb neutrons in Nagasaki and the contribution of environmental neutrons to this activity.

    PubMed

    Shizuma, Kiyoshi; Endo, Satoru; Hoshi, Masaharu; Takada, Jun; Ishikawa, Masayori; Iwatani, Kazuo; Hasai, Hiromi; Oka, Takamitsu; Fujita, Shoichiro; Watanabe, Tadaaki; Yamashita, Tomoaki; Imanaka, Tetsuji

    2003-06-01

    Residual 152Eu activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 m in the slant range and one control sample at 2,850 m from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of 152Eu are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of 60Co and 36Cl. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for 152Eu are also discussed. PMID:13678342

  3. Development of active environmental and personal neutron dosemeters.

    PubMed

    Nakamura, T; Nunomiya, T; Sasaki, M

    2004-01-01

    For neutron dosimetry in the radiation environment surrounding nuclear facilities, two types of environmental neutron dosemeters, the high-sensitivity rem counter and the high-sensitivity multi-moderator, the so-called Bonner ball, have been developed and the former is commercially available from Fuji Electric Co. By using these detectors, the cosmic ray neutrons at sea level have been sequentially measured for about 3 y to investigate the time variation of neutron spectrum and ambient dose equivalent influenced by cosmic and terrestrial effects. Our Bonner ball has also been selected as the neutron detector in the International Space Station and has already been used to measure neutrons in the US experimental module. The real time wide-range personal neutron dosemeter which uses two silicon semiconductor detectors has been developed for personal dosimetry and is commercially available from Fuji Electric Co. This dosemeter has good characteristics, fitted to the fluence-to-dose conversion factor in the energy range from thermal energies to several tens of mega-electron-volts and is now widely used in various nuclear facilities.

  4. Predictive activity profiling of drugs by topological-fragment-spectra-based support vector machines.

    PubMed

    Kawai, Kentaro; Fujishima, Satoshi; Takahashi, Yoshimasa

    2008-06-01

    Aiming at the prediction of pleiotropic effects of drugs, we have investigated the multilabel classification of drugs that have one or more of 100 different kinds of activity labels. Structural feature representation of each drug molecule was based on the topological fragment spectra method, which was proposed in our previous work. Support vector machine (SVM) was used for the classification and the prediction of their activity classes. Multilabel classification was carried out by a set of the SVM classifiers. The collective SVM classifiers were trained with a training set of 59,180 compounds and validated by another set (validation set) of 29,590 compounds. For a test set that consists of 9,864 compounds, the classifiers correctly classified 80.8% of the drugs into their own active classes. The SVM classifiers also successfully performed predictions of the activity spectra for multilabel compounds. PMID:18533712

  5. Neutron Activation Analysis PRognosis and Optimization Code System.

    2004-08-20

    Version 00 NAAPRO predicts the results and main characteristics (detection limits, determination limits, measurement limits and relative precision of the analysis) of neutron activation analysis (instrumental and radiochemical). Gamma-ray dose rates for different points of time after sample irradiation and input count rate of the spectrometry system are also predicted. The code uses standard Windows user interface and extensive graphical tools for the visualization of the spectrometer characteristics (efficiency, response and background) and simulated spectrum.more » Optimization part is not included in the current version of the code. This release is designated NAAPRO, Version 01.beta. The MCNP code was used for generating detector responses. PREPRO-2000 and FCONV programs were used at the preparation of the program nuclear databases. A special program was developed for viewing, editing and updating of the program databases (not included into the present program package). The MCNP, PREPRO-2000 and FCONV software packages are not included in the NAAPRO package.« less

  6. A neutron activation technique for manganese measurements in humans.

    PubMed

    Bhatia, C; Byun, S H; Chettle, D R; Inskip, M J; Prestwich, W V

    2015-01-01

    Manganese (Mn) is an essential element for humans, animals, and plants and is required for growth, development, and maintenance of health. Studies show that Mn metabolism is similar to that of iron, therefore, increased Mn levels in humans could interfere with the absorption of dietary iron leading to anemia. Also, excess exposure to Mn dust, leads to nervous system disorders similar to Parkinson's disease. Higher exposure to Mn is essentially related to industrial pollution. Thus, there is a benefit in developing a clean non-invasive technique for monitoring such increased levels of Mn in order to understand the risk of disease and development of appropriate treatments. To this end, the feasibility of Mn measurements with their minimum detection limits (MDL) has been reported earlier from the McMaster group. This work presents improvement to Mn assessment using an upgraded system and optimized times of irradiation and counting for induced gamma activity of Mn. The technique utilizes the high proton current Tandetron accelerator producing neutrons via the (7)Li(p,n)(7)Be reaction at McMaster University and an array of nine NaI (Tl) detectors in a 4 π geometry for delayed counting of gamma rays. The neutron irradiation of a set of phantoms was performed with protocols having different proton energy, current and time of irradiation. The improved MDLs estimated using the upgraded set up and constrained timings are reported as 0.67 μgMn/gCa for 2.3 MeV protons and 0.71 μgMn/gCa for 2.0 MeV protons. These are a factor of about 2.3 times better than previous measurements done at McMaster University using the in vivo set-up. Also, because of lower dose-equivalent and a relatively close MDL, the combination of: 2.0 MeV; 300 μA; 3 min protocol is recommended as compared to 2.3 MeV; 400 μA; 45 s protocol for further measurements of Mn in vivo. PMID:25169978

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

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1984-01-01

    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.

  8. Raman Optical Activity Spectra for Large Molecules through Molecules-in-Molecules Fragment-Based Approach.

    PubMed

    Jovan Jose, K V; Raghavachari, Krishnan

    2016-02-01

    We present an efficient method for the calculation of the Raman optical activity (ROA) spectra for large molecules through the molecules-in-molecules (MIM) fragment-based method. The relevant higher energy derivatives from smaller fragments are used to build the property tensors of the parent molecule to enable the extension of the MIM method for evaluating ROA spectra (MIM-ROA). Two factors were found to be particularly important in yielding accurate results. First, the link-atom tensor components are projected back onto the corresponding host and supporting atoms through the Jacobian projection method, yielding a mathematically rigorous method. Second, the long-range interactions between fragments are taken into account by using a less computationally expensive lower level of theory. The performance of the MIM-ROA model is calibrated on the enantiomeric pairs of 10 carbohydrate benchmark molecules, with strong intramolecular interactions. The vibrational frequencies and ROA intensities are accurately reproduced relative to the full, unfragmented, results for these systems. In addition, the MIM-ROA method is employed to predict the ROA spectra of d-maltose, α-D-cyclodextrin, and cryptophane-A, yielding spectra in excellent agreement with experiment. The accuracy and performance of the benchmark systems validate the MIM-ROA model for exploring ROA spectra of large molecules.

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

    SciTech Connect

    Evans, Louise G; Goddard, Braden; Charlton, William S; Peerani, Paolo

    2012-08-13

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

  10. "Hot background" of the mobile inelastic neutron scattering system for soil carbon analysis.

    PubMed

    Kavetskiy, Aleksandr; Yakubova, Galina; Prior, Stephen A; Torbert, H Allen

    2016-01-01

    The problem of gamma spectrum peak identification arises when conducting soil carbon analysis using the inelastic neutron scattering (INS) system. Some spectral peaks could be associated with radioisotopes appearing due to neutron activation of both the measurement system and soil samples. The investigation of "hot background" gamma spectra from the construction materials, whole measurement system, and soil samples over time showed that activation of (28)Al isotope can contribute noticeable additions to the soil neutron stimulated gamma spectra. PMID:26595773

  11. Neutron intensity monitor with activation foil for p-Li neutron source for BNCT--Feasibility test of the concept.

    PubMed

    Murata, Isao; Otani, Yuki; Sato, Fuminobu

    2015-12-01

    Proton-lithium (p-Li) reaction is being examined worldwide as a candidate nuclear production reaction for accelerator based neutron source (ABNS) for BNCT. In this reaction, the emitted neutron energy is not so high, below 1 MeV, and especially in backward angles the energy is as low as about 100 keV. The intensity measurement was thus known to be difficult so far. In the present study, a simple method was investigated to monitor the absolute neutron intensity of the p-Li neutron source by employing the foil activation method based on isomer production reactions in order to cover around several hundreds keV. As a result of numerical examination, it was found that (107)Ag, (115)In and (189)Os would be feasible. Their features found out are summarized as follows: (107)Ag: The most convenient foil, since the half life is short. (115)In: The accuracy is the best at 0°, though it cannot be used for backward angles. And (189)Os: Suitable nuclide which can be used in backward angles, though the gamma-ray energy is a little too low. These would be used for p-Li source monitoring depending on measuring purposes in real BNCT scenes. PMID:26242557

  12. Present and Future Activities on Neutron Imaging in Argentina

    NASA Astrophysics Data System (ADS)

    Tartaglione, Aureliano; Blostein, Jerónimo; Cantargi, Florencia; Marín, Julio; Baruj, Alberto; Meyer, Gabriel; Santisteban, Javier; Sánchez, Fernando

    We present here a short review of the main work which has been done in the latest years in neutron imaging in Argentina, and the future plans for the development of this technique in the country, mainly focused in the design of a new neutron imaging instrument to be installed in the future research reactor RA10. We present here the results of the implementation of the technique in samples belonging to the Argentinean cultural heritage and experiments related with hydrogen storage. At the same time, the Argentinean RA10 project for the design and construction of a 30 MW multipurpose research reactor is rapidly progressing. It started to be designed by the National Atomic Energy Commission (CNEA) and the technology company INVAP SE, both from Argentina, in June 2010. The construction will start in the beginning of 2015 in the Ezeiza Atomic Center, at 36 km from Buenos Aires City, and is expected to be finished by 2020. One of the main aims of the project is to offer to the Argentinean scientific and technology system new capabilities based on neutron techniques. We present here the conceptual design of a neutron imaging facility which will use one of the cold neutron beams, and will be installed in the reactor hall. Preliminary simulation results show that at the farthest detection position, at about 17 m from the cold source, a uniform neutron beam on a detection screen with an intensity of about 108 n/cm2/s is expected.

  13. Improved mesh based photon sampling techniques for neutron activation analysis

    SciTech Connect

    Relson, E.; Wilson, P. P. H.; Biondo, E. D.

    2013-07-01

    The design of fusion power systems requires analysis of neutron activation of large, complex volumes, and the resulting particles emitted from these volumes. Structured mesh-based discretization of these problems allows for improved modeling in these activation analysis problems. Finer discretization of these problems results in large computational costs, which drives the investigation of more efficient methods. Within an ad hoc subroutine of the Monte Carlo transport code MCNP, we implement sampling of voxels and photon energies for volumetric sources using the alias method. The alias method enables efficient sampling of a discrete probability distribution, and operates in 0(1) time, whereas the simpler direct discrete method requires 0(log(n)) time. By using the alias method, voxel sampling becomes a viable alternative to sampling space with the 0(1) approach of uniformly sampling the problem volume. Additionally, with voxel sampling it is straightforward to introduce biasing of volumetric sources, and we implement this biasing of voxels as an additional variance reduction technique that can be applied. We verify our implementation and compare the alias method, with and without biasing, to direct discrete sampling of voxels, and to uniform sampling. We study the behavior of source biasing in a second set of tests and find trends between improvements and source shape, material, and material density. Overall, however, the magnitude of improvements from source biasing appears to be limited. Future work will benefit from the implementation of efficient voxel sampling - particularly with conformal unstructured meshes where the uniform sampling approach cannot be applied. (authors)

  14. Nuclear-level densities in the 49V and 57Co nuclei on the basis of evaporated-neutron spectra in ( p, n) and ( d, n) reactions

    NASA Astrophysics Data System (ADS)

    Zhuravlev, B. V.; Titarenko, N. N.

    2016-03-01

    The spectra of neutrons from the reactions 49Ti( p, n)49V and 57Fe ( p, n)57Co were measured in the range of proton energies between 8 and 11 MeV along with their counterparts from the reactions 48Ti( d, n)49V and 56Fe ( d, n)57Co at the deuteron energies of 2.7 and 3.8 MeV. These measurements were conducted with the aid of a time-of-flight fast-neutron spectrometer on the basis of the EGP-15 pulsed tandem accelerator of the Institute for Physics and Power Engineering (IPPE, Obninsk). An analysis of measured data was performed within the statistical equilibrium and preequilibrium models of nuclear reactions. The respective calculations based on the Hauser-Feshbach formalism of statistical theory were carried out with nuclear-level densities given by the generalized superfluid model of the nucleus, the backshifted Fermi-gas model, and the Gilbert-Cameron composite formula. The nuclear-level densities of 49V and 57Co and their energy dependences were determined. The results were discussed together with available experimental data and data recommended by model systematics.

  15. Analysis of fusion neutron spectra and the importance of 6 dimensional effects in ``high-foot'' implosions at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Hartouni, Edward P.; Caggiano, Joseph A.; Callahan, Debbie; Casey, Daniel T.; Cerjan, Charlie; Clarke, Dan; Doeppner, Tilo; Eckart, Mark J.; Field, John E.; Frenje, Johan; Gatu-Johnson, Maria; Grim, Gary P.; Hatarik, Robert; Hurricane, Omar A.; Kilkenny, Joseph; Knauer, James; Ma, Tammy; Mannion, Owen M.; Munro, David M.; Sayre, Daniel B.; Spears, Brian K.; Yeamans, Charles B.

    2015-11-01

    High convergence implosions introduce a number of factors having significant effects on the analysis of high precision reactant neutron time-of-flight (TOF) spectra at the NIF. Low mode perturbations of both the spatial and velocity distributions of the hot-spot and the cold-fuel are measurable in this data set. We report on the analysis performed to date including the line-of-sight (LOS) variation of ``standard observables'' (e.g. the yield and ion temperature) as well as new analysis extracting the bulk hot-spot velocity and the hot-spot velocity variance. These observations indicate that the assumption of isotropy of reactant neutrons can no longer provide an accurate description of the data. Preliminary analysis of the NIF ``high foot'' campaign data will be reported. We will describe the direction of future nuclear diagnostic techniques. Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.

  16. Response of thunderstorm activity in data of neutron monitoring at Tien Shan

    NASA Astrophysics Data System (ADS)

    Antonova, Valentina; Kryukov, Sergey; Lutsenko, Vadim

    2015-04-01

    We present results of the study of data of the monitoring of high-energy and thermal neutrons at Tien Shan at different stages of thunderstorm activity. The data of the neutron monitoring were used taking into account the barometric effect. The intensity of the neutron component of cosmic rays is recorded in seven energy ranges. The electric field has values of ~ 100 V/m under fair weather conditions. Standard deviation of minute values of the neutron monitor data at the high altitude station does not exceed 0.5-0.6 %. Found that the standard deviation of the data during thunderstorms always exceeds these values. We selected events during the passage of thunderstorm clouds over the high altitude station without lightning discharges or with a small number of them. It was found that the particle rate of the neutron monitor changes in antiphase with the electric field changes. Atmospheric electric field of positive polarity decreases the count rate of the neutron monitor, and negative polarity - increases. Change of the count rate occurs at values of electric field ≥ 10-15 kV/m and reaches 2 %. The neutron monitor at the high-altitude station has the ability to measure the energy of recorded particles through determination of their multiplicity. We experimentally established that the sensitivity of the detected particles to change in Ez increases with decreasing their energy. The upper energy threshold of sensitivity of neutrons to change electric field is ~10 GeV. The physical mechanism of effect is based on lead nucleus capture of soft negative muons with the subsequent generation of neutrons. It is known that 7% of the neutron monitor count rate caused by negative muons. Absence of this effect in thermal neutrons data confirms the conclusion since the main difference of the thermal neutrons detector from the neutron monitor is the absence of the lead. In the active phase of a thunderstorm in the formed thundercloud the picture of distribution of charges is

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

    SciTech Connect

    Robin P. Gardner

    2006-04-11

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

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 μm) 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 μm 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 ΩAGN 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

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

    SciTech Connect

    Pillalamarri, Ila

    2005-09-08

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

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

    NASA Astrophysics Data System (ADS)

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

    1999-06-01

    This study compares two independently calibrated delayed-gamma neutron activation (DGNA) facilities, one at the Brookhaven National Laboratory (BNL), Upton, New York, and the other at the Children's Nutrition Research Center (CNRC), Houston, Texas that measure total body calcium (TBCa). A set of BNL phantoms was sent to CNRC for neutron activation analysis, and a set of CNRC phantoms was measured at BNL. Both facilities showed high precision (<2%), and the results were in good agreement, within 5%.

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

    NASA Astrophysics Data System (ADS)

    Güngör, N.; Tulun, T.; Alemdar, A.

    1998-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Delgado-Correal, Camilo; Munera, Hector

    2008-03-01

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

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

    SciTech Connect

    D. L. Chichester; E. H. Seabury

    2008-10-01

    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.

  6. DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORY’S ACTIVE NEUTRON INTERROGATION TEST FACILITY

    SciTech Connect

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

    2009-06-01

    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.

  7. Determination of (n,γ) Cross Sections of 241Am by Cold Neutron Activation

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  8. SWAN - Detection of explosives by means of fast neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Gierlik, M.; Borsuk, S.; Guzik, Z.; Iwanowska, J.; Kaźmierczak, Ł.; Korolczuk, S.; Kozłowski, T.; Krakowski, T.; Marcinkowski, R.; Swiderski, L.; Szeptycka, M.; Szewiński, J.; Urban, A.

    2016-10-01

    In this work we report on SWAN, the experimental, portable device for explosives detection. The device was created as part of the EU Structural Funds Project "Accelerators & Detectors" (POIG.01.01.02-14-012/08-00), with the goal to increase beneficiary's expertise and competencies in the field of neutron activation analysis. Previous experiences and budged limitations lead toward a less advanced design based on fast neutron interactions and unsophisticated data analysis with the emphasis on the latest gamma detection and spectrometry solutions. The final device has been designed as a portable, fast neutron activation analyzer, with the software optimized for detection of carbon, nitrogen and oxygen. SWAN's performance in the role of explosives detector is elaborated in this paper. We demonstrate that the unique features offered by neutron activation analysis might not be impressive enough when confronted with practical demands and expectations of a generic homeland security customer.

  9. Comparison of Impurities in Charcoal Sorbents Found by Neutron Activation Analysis

    SciTech Connect

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

    2013-01-01

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

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

    SciTech Connect

    Blackston, Matthew A; Hausladen, Paul

    2010-04-01

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

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

    SciTech Connect

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

    2012-07-01

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

  12. A portable active interrogation system using a switchable AmBe neutron source

    NASA Astrophysics Data System (ADS)

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

    2005-09-01

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

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

    PubMed

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

    2012-10-01

    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.

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

    PubMed

    Iwatani, K; Hoshi, M; Shizuma, K; Hiraoka, M; Hayakawa, N; Oka, T; Hasai, H

    1994-10-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated 252Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate 152Eu and 60Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated 252Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen. PMID:8083048

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

    SciTech Connect

    Iwatani, Kazuo; Shizuma, Kiyoshi; Hasai, Hiromi; Hoshi, Masaharu; Hiraoka, Masayuki; Hayakawa, Norihiko; Oka, Takamitsu

    1994-10-01

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

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

    PubMed

    Iwatani, K; Hoshi, M; Shizuma, K; Hiraoka, M; Hayakawa, N; Oka, T; Hasai, H

    1994-10-01

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

  17. Calibration of the Brookhaven National Laboratory delayed gamma neutron activation facility to measure total body calcium.

    PubMed

    Ma, R; Stamatelatos, I E; Yasumura, S

    2000-05-01

    Differences in body size and shape can cause large variances in the in vivo results of neutron activation analysis. To introduce corrections for body size for the delayed gamma neutron activation facility at Brookhaven National Laboratory, "reference man"-sized and "reference woman"-sized phantoms were constructed. Simulation results using the Monte Carlo Neutron and Photon Transport code also provided correction factors for people of different sizes. For individuals with a body mass index (BMI = weight (kg)/height (m)2) between 20 and 30, no correction was required. At BMIs greater than 30, the effects of neutron attenuation were significant and a correction factor of CF = -0.0192 x BMI + 1.5635 can be applied. PMID:10865727

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

    NASA Astrophysics Data System (ADS)

    Kehayias, J. J.

    2001-07-01

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

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

    SciTech Connect

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

    2010-03-25

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

  20. Cold neutron prompt gamma-ray activation analysis at NIST - an overview

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.

    1994-12-31

    An instrument for cold neutron capture prompt gamma-ray activation analysis (CNPGAA), located in the cold neutron research facility (CNRF) at the National Institute of Standards and Technology (NIST) has proven useful for the analysis of hydrogen and other elements in a wide variety of materials. The intent of this paper is to provide an overview of the instrument, focusing on recent improvements and the impact of these improvement on measurements.

  1. Determination of hydrogen in titanium alloys by cold neutron prompt gamma activation analysis

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.; Greenberg, R.R.; Privett, H.M. III; Richards, W.J.

    1996-11-01

    Cold neutron prompt gamma-ray activation analysis (CNPGAA) has proven useful for the analysis of hydrogen in titanium alloys. The analysis is nondestructive, measures the entire sample, and the results are independent of the chemical form of hydrogen present. The authors have used the technique to measure H mass fractions as low as 50 mg/kg in titanium-alloy jet-engine compressor blades and to measure hydrogen in standards for neutron tomography.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Scandariato, Gaetano; Micela, Giuseppina

    2015-12-01

    EChO is 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.

  4. Modeling of neutron spectrum in the gamma spectroscopy measurements with Ge-detectors

    NASA Astrophysics Data System (ADS)

    Knežević, D.; Jovančević, N.; Krmar, M.; Petrović, J.

    2016-10-01

    In this study, we present a novel approach for estimation of neutron spectra that are present during gamma spectroscopy measurements performed by a Ge detector. This method is based on the calculation of the neutron spectra by using an unfolding procedure, where the activity of the Ge isotopes, produced by the neutron reactions, and the available cross section data for those reactions are the input parameters. This new approach was tested by background gamma spectroscopy measurements with a HPGe detector. Obtained results show that this method can provide useful information about the neutron spectra at the position of the Ge detectors.

  5. Simulation of a Novel Active Target for Neutron-Unbound State Measurements

    NASA Astrophysics Data System (ADS)

    Frank, Nathan; MoNA Collaboration

    2013-10-01

    Measurement of nuclei at extreme ratios of protons to neutrons is challenging due to the low production rate. New facilities will increase the production of neutron-rich isotopes, but still not reach the neutron dripline for heavier nuclei. We simulated a carbon-based active target system that could be constructed to both increase statistics while preserving the experimental resolution. This simulation is an adaptation of the in-house MoNA Collaboration C + + based simulation tool to extract the decay energy of neutron-unbound states. A number of experiments of this type have been carried out at the National Superconducting Cyclotron Laboratory (NSCL). In most experiments, we produce neutron-unbound nuclei by bombarding a Beryllium target with a radioactive beam. The nucleus of interest immediately decays into a charged particle and one or more neutrons. In this simulation, we have constructed a carbon-based active target that provides a measurement of energy loss, which is used to calculate the nuclear interaction point within the target. This additional information is used to improve the resolution or preserve the resolution of a thinner target while increasing statistics. This presentation will cover some aspects of the simulation process as well as show a resolution improvement of up to about 4 with a ~700 mg/cm2 active target compared to a Be-target. The simulation utilized experimental settings from published work. Work supported by National Science Foundation Grant #0969173.

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  7. Implementation of an enhanced, permanently installed neutron activation diagnostic hardware for NIF

    NASA Astrophysics Data System (ADS)

    Jedlovec, Donald R.; Edwards, Ellen R.; Carrera, Jorge A.; Yeamans, Charles B.

    2015-08-01

    Neutron activation diagnostics are commonly employed as baseline neutron yield and relative spatial flux measurement instruments. Much insight into implosion performance has been gained by deployment of up to 19 identical activation diagnostic samples distributed around the target chamber at unique angular locations. Their relative simplicity and traceability provide neutron facilities with a diagnostic platform that is easy to implement and verify. However, the current National Ignition Facility (NIF) implementation relies on removable activation samples, creating a 1-2 week data turn-around time and considerable labor costs. The system described here utilizes a commercially-available lanthanum bromide (cerium-doped) scintillator with an integrated MCA emulator as the counting system and a machined zirconium-702 cap as the activation medium. The device is installed within the target bay and monitored remotely. Additionally, this system allows the placement of any activation medium tailored to the specific measurement needs. We discuss the design and function of a stand-alone and permanently installed neutron activation detector unit to measure the yield and average energy of a nominal 14 MeV neutron source with a pulse length less than one nanosecond.

  8. Fission and activation of uranium by fusion-plasma neutrons

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  9. Physical and chemical limitations to preparation of beta radioactive stents by direct neutron activation.

    PubMed

    Petelenz, Barbara; Rajchel, Bogusław; Bilski, Paweł; Misiak, Ryszard; Bartyzel, Mirosław; Wilczek, Krzysztof; Alber, Dorothea

    2003-02-01

    Pure beta emitters are the sources of choice for intracoronary irradiations in restenosis prevention. In this work we reconsidered preparation of low activity 32P sources by ion-implantation of stable 31P into highly biocompatible pure titanium stents, followed by neutron activation. Gamma-spectrometrical analysis has shown that during activations with high thermal neutrons flux production of gamma-active long-lived contaminants is much beyond the dosimetrically acceptable limit, mainly due to the competing (n,p) reactions induced by the fast neutrons on isotopes of the bulk stent material, and to a lesser extent due to (n,gamma) reactions on chemical impurities. A potential applicability of this method for obtaining alternative beta radioactive stents is discussed.

  10. Neutron Activation Analysis of Soil Samples from Different Parts of Edirne in Turkey*

    NASA Astrophysics Data System (ADS)

    Zaim, N.; Dogan, C.; Camtakan, Z.

    2016-05-01

    The concentrations of constituent elements were determined in soil samples collected from different parts of the Maritza Basin, Edirne, Turkey. Neutron activation analysis, an extremely accurate technique, and the comparator method (using a standard) were applied for the first time in this region. After preparing the soil samples for neutron activation analysis, they were activated with thermal neutrons in a nuclear reactor, TRIGA-MARK II, at Istanbul Technical University. The activated samples were analyzed using a high-efficiency high-purity germanium detector, and gamma spectrometry was employed to determine the elemental concentration in the samples. Eight elements (chromium, manganese, cobalt, zinc, arsenic, molybdenum, cadmium, and barium) were qualitatively and quantitatively identified in 36 samples. The concentrations of some elements in the soil samples were high compared with values reported in the literature.

  11. Development of Enhanced, Permanently-Installed, Neutron Activation Diagnostic Hardware for NIF

    NASA Astrophysics Data System (ADS)

    Edwards, E. R.; Jedlovec, D. R.; Carrera, J. A.; Yeamans, C. B.

    2016-05-01

    Neutron activation diagnostics are baseline neutron yield and flux measurement instruments at the National Ignition Facility. Up to 19 activation samples are distributed around the target chamber. Currently the samples must be removed to be counted, creating a 1-2 week data turn-around time and considerable labor costs. An improved system consisting of a commercially available LaBr3(Ce) scintillator and Power over Ethernet electronics is under development. A machined zirconium-702 cap over the detector is the activation medium to measure the 90Zr(n,2n)89Zr reaction. The detectors are located at the current neutron activation diagnostic sites and monitored remotely. Because they collect data in real time yield values are returned within a few hours after a NIF shot.

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

    PubMed

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

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Landoas, Olivier; Yu Glebov, Vladimir; Rossé, 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

    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 à 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.

  14. Benchmarking of activation reaction distribution in an intermediate energy neutron field.

    PubMed

    Ogawa, Tatsuhiko; Morev, Mikhail N; Hirota, Masahiro; Abe, Takuya; Koike, Yuya; Iwai, Satoshi; Iimoto, Takeshi; Kosako, Toshiso

    2011-07-01

    Neutron-induced reaction rate depth profiles inside concrete shield irradiated by intermediate energy neutron were calculated using a Monte-Carlo code and compared with an experiment. An irradiation field of intermediate neutron produced in the forward direction from a thick (stopping length) target bombarded by 400 MeV nucleon(-1) carbon ions was arranged at the heavy ion medical accelerator in Chiba. Ordinary concrete shield of 90 cm thickness was installed 50 cm downstream the iron target. Activation detectors of aluminum, gold and gold covered with cadmium were inserted at various depths. Irradiated samples were extracted after exposure and gamma-ray spectrometry was performed for each sample. Comparison of experimental and calculated shows good agreement for both low- and high-energy neutron-induced reaction except for (27)Al(n,X)(24)Na reaction at the surface. PMID:21515619

  15. DIVERSE ACTIVE WELL NEUTRON COINCIDENCE COUNTER UTILITY AT THE SAVANNAH RIVER NATIONAL LABORATORY

    SciTech Connect

    Dewberry, R; Saleem Salaymeh, S

    2007-01-08

    In this paper we describe use of the Aquila active well neutron coincidence counter for nuclear material assays of {sup 235}U in multiple analytical techniques at Savannah River Site (SRS), at the Savannah River National Laboratory (SRNL), and at Argonne West National Laboratory (AWNL). The uses include as a portable passive neutron counter for field measurements searching for evidence of {sup 252}Cf deposits and storage; as a portable active neutron counter using an external activation source for field measurements searching for trace {sup 235}U deposits and holdup; for verification measurements of U-Al reactor fuel elements; for verification measurements of uranium metal; and for verification measurements of process waste of impure uranium in a challenging cement matrix. The wide variety of uses described demonstrate utility of the technique for neutron coincidence verification measurements over the dynamic ranges of 100 g-5000 g for U metal, 200 g-1300 g for U-Al, and 8 g-35 g for process waste. In addition to demonstrating use of the instrument in both the passive and active modes, we also demonstrate its use in both the fast and thermal neutron modes.

  16. Investigation of the neutron activation of endohedral rare earth metallofullerenes

    SciTech Connect

    Shilin, V. A. Lebedev, V. T.; Kolesnik, S. G.; Kozlov, V. S.; Grushko, Yu. S.; Sedov, V. P.; Kukorenko, V. V.

    2011-12-15

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

  17. Testing of regolith of celestial bolides with active neutron gamma-ray spectrometry

    NASA Astrophysics Data System (ADS)

    Vostrukhin, Andrey; Mitrofanov, Igor; Golovin, Dmitry; Litvak, Maxim; Sanin, Anton

    2015-04-01

    Current space instruments for studying planet's surface include gamma ray spectrometers that detect natural radioactive isotopes as well as gamma-rays induced in subsurface by galactic cosmic rays. When measuring from celestial body's surface, statistics and amount of detected elements can be dramatically increased with active methods, where soil exposed to artificial flux of particles. One good example is the Russian Dynamic Albedo of Neutron (DAN) instrument onboard Martian Science Laboratory mission (Curiosity rover) developed in 2005-2011. It is the first active neutron spectrometer flown to another planet as part of a landed mission to investigate subsurface water distribution and which has now successfully operated for more than two years on the Martian surface. Presentation describes a number of space instruments for different landers and rovers being developed in Russian Space Research Institute for studying Moon and Mars, as well as method of active neutron and gamma spectrometry overview.

  18. Device and software used to carry out Cyclic Neutron Activation Analysis

    NASA Astrophysics Data System (ADS)

    Castro-García, M. P.; Rey-Ronco, M. A.; Alonso-Sánchez, T.

    2014-11-01

    This paper discusses the device and software used to carry out Cyclic Neutron Activation Analysis (CNAA). The aim of this investigation is defining through this device the fluorite content present on different samples from fluorspar concentration plant through the DGNAA (Delayed Gamma Neutron Activation Analysis) method. This device is made of americium-beryllium neutron source, NaI (2"×2") and BGO (2"×2") gamma rays detectors, multichannel and an automatic mechanism which moves the samples from activation and reading position. This mechanism is controlled by a software which allows moving the samples precisely and in a safe way (~ms), which it is very useful when the radioactive isotopes have to be detected with a half time less than 8s.

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

    PubMed

    El-Taher, A

    2010-09-01

    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.

  20. Elemental analysis of granite by instrumental neutron activation analysis (INAA) and X-ray fluorescence analysis (XRF).

    PubMed

    El-Taher, A

    2012-01-01

    The instrumental neutron activation analysis technique (INAA) was used for qualitative and quantitative analysis of granite samples collected from four locations in the Aswan area in South Egypt. The samples were prepared together with their standards and simultaneously irradiated in a neutron flux of 7×10(11)n/cm(2)s in the TRIGA Mainz research reactor. Gamma-ray spectra from an hyper-pure germanium detector were analyzed. The present study provides the basic data of elemental concentrations of granite rocks. The following elements have been determined Na, Mg, K, Fe, Mn, Sc, Cr, Ti, Co, Zn, Ga, Rb, Zr, Nb, Sn, Ba, Cs, La, Ce, Nd, Sm, Eu, Yb, Lu, Hf, Ta, Th and U. The X-ray fluorescence (XRF) was used for comparison and to detect elements, which can be detected only by XRF such as F, S, Cl, Co, Cu, Mo, Ni, Pb, Se and V. The data presented here are our contribution to understanding the elemental composition of the granite rocks. Because there are no existing databases for the elemental analysis of granite, our results are a start to establishing a database for the Egyptian granite. It is hoped that the data presented here will be useful to those dealing with geochemistry, granite chemistry and related fields.

  1. First principle active neutron coincidence counting measurements of uranium oxide

    NASA Astrophysics Data System (ADS)

    Goddard, Braden; Charlton, William; Peerani, Paolo

    2014-03-01

    Uranium is present in most nuclear fuel cycle facilities ranging from uranium mines, enrichment plants, fuel fabrication facilities, nuclear reactors, and reprocessing plants. The isotopic, chemical, and geometric composition of uranium can vary significantly between these facilities, depending on the application and type of facility. Examples of this variation are: enrichments varying from depleted (~0.2 wt% 235U) to high enriched (>20 wt% 235U); compositions consisting of U3O8, UO2, UF6, metallic, and ceramic forms; geometries ranging from plates, cans, and rods; and masses which can range from a 500 kg fuel assembly down to a few grams fuel pellet. Since 235U is a fissile material, it is routinely safeguarded in these facilities. Current techniques for quantifying the 235U mass in a sample include neutron coincidence counting. One of the main disadvantages of this technique is that it requires a known standard of representative geometry and composition for calibration, which opens up a pathway for potential erroneous declarations by the State and reduces the effectiveness of safeguards. In order to address this weakness, the authors have developed a neutron coincidence counting technique which uses the first principle point-model developed by Boehnel instead of the "known standard" method. This technique was primarily tested through simulations of 1000 g U3O8 samples using the Monte Carlo N-Particle eXtended (MCNPX) code. The results of these simulations showed good agreement between the simulated and exact 235U sample masses.

  2. Probing Planetary Bodies for Subsurface Volatiles: GEANT4 Models of Gamma Ray, Fast, Epithermal, and Thermal Neutron Response to Active Neutron Illumination

    NASA Astrophysics Data System (ADS)

    Chin, G.; Sagdeev, R.; Su, J. J.; Murray, J.

    2014-12-01

    Using an active source of neutrons as an in situ probe of a planetary body has proven to be a powerful tool to extract information about the presence, abundance, and location of subsurface volatiles without the need for drilling. The Dynamic Albedo of Neutrons (DAN) instrument on Curiosity is an example of such an instrument and is designed to detect the location and abundance of hydrogen within the top 50 cm of the Martian surface. DAN works by sending a pulse of neutrons towards the ground beneath the rover and detecting the reflected neutrons. The intensity and time of arrival of the reflection depends on the proportion of water, while the time the pulse takes to reach the detector is a function of the depth at which the water is located. Similar instruments can also be effective probes at the polar-regions of the Moon or on asteroids as a way of detecting sequestered volatiles. We present the results of GEANT4 particle simulation models of gamma ray, fast, epithermal, and thermal neutron responses to active neutron illumination. The results are parameterized by hydrogen abundance, stratification and depth of volatile layers, versus the distribution of neutron and gamma ray energy reflections. Models will be presented to approximate Martian, lunar, and asteroid environments and would be useful tools to assess utility for future NASA exploration missions to these types of planetary bodies.

  3. Active-Interrogation Measurements of Fast Neutrons from Induced Fission in Low-Enriched Uranium

    SciTech Connect

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

    2014-02-01

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

  4. 3D mapping of lithium in battery electrodes using neutron activation

    NASA Astrophysics Data System (ADS)

    He, Yuping; Downing, R. Gregory; Wang, Howard

    2015-08-01

    The neutron depth profiling technique based on the neutron activation reaction, 6Li (n, α) 3H, was applied with two dimensional (2D) pinhole aperture scans to spatially map lithium in 3D. The technique was used to study model LiFePO4 electrodes of rechargeable batteries for spatial heterogeneities of lithium in two cathode films that had undergone different electrochemical cycling histories. The method is useful for better understanding the functioning and failure of batteries using lithium as the active element.

  5. Determination of sodium in biological materials by instrumental neutron activation analysis.

    PubMed

    Cunningham, W C; Capar, S G; Anderson, D L

    1997-01-01

    A formalized method for determining sodium in biological materials by instrumental neutron activation analysis is presented. The method includes common procedures from the numerous options available to this historically nonformalized analytical technique. The number of procedural options is restricted to minimize the method's complexity, yet the method is still applicable to a variety of neutron activation facilities. High accuracy and precision are achieved by placing bounds on allowed uncertainty at critical stages of the analysis. Analytical results from the U.S. Food and Drug Administration laboratory and 4 other laboratories demonstrate the method's performance.

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

    SciTech Connect

    Graham, C.C.; Glascock, M.D.; Carni, J.J.; Vogt, J.R.; Spalding, T.G.

    1982-08-01

    Instrumental neutron activation analysis (INAA) and prompt gamma neutron activation analysis (PGNAA) have been used to determine elemental concentrations in two recently issued National Bureau of Standards (NBS) Standard Reference Materials (SRM's). The results obtained are in good agreement with the certified and information values reported by NBS for those elements in each material for which comparisons are available. Average concentrations of 35 elements in SRM 278 obsidian rock and 32 elements in SRM 688 basalt rock are reported for comparison with results that may be obtained by other laboratories.

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

    SciTech Connect

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

    1980-01-01

    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.

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

    SciTech Connect

    Ku, L.; Kolibal, J.G.

    1982-06-01

    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.

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

    SciTech Connect

    Krick, M.S.; Ensslin, N.; Ceo, R.N.; May, P.K.

    1996-09-01

    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.

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

    PubMed

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

    1993-09-01

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

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

    PubMed

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

    2014-01-01

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

  12. Accurate and precise measurement of selenium by instrumental neutron activation analysis.

    PubMed

    Kim, In Jung; Watson, Russell P; Lindstrom, Richard M

    2011-05-01

    An accurate and precise measurement of selenium in Standard Reference Material (SRM) 3149, a primary calibration standard for the quantitative determination of selenium, has been accomplished by instrumental neutron activation analysis (INAA) in order to resolve a question arising during the certification process of the standard. Each limiting factor of the uncertainty in the activation analysis, including the sample preparation, irradiation, and γ-ray spectrometry steps, has been carefully monitored to minimize the uncertainty in the determined mass fraction. Neutron and γ-ray self-shielding within the elemental selenium INAA standards contributed most significantly to the uncertainty of the measurement. An empirical model compensating for neutron self-shielding and reducing the self-shielding uncertainty was successfully applied to these selenium standards. The mass fraction of selenium in the new lot of SRM 3149 was determined with a relative standard uncertainty of 0.6%.

  13. Measuring neutron yield and ρR anisotropies with activation foils at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Bleuel, D. L.; Bernstein, L. A.; Bionta, R. M.; Cooper, G. W.; Drury, O. B.; Hagmann, C. A.; Knittel, K. M.; Leeper, R. J.; Ruiz, C. L.; Schneider, D. H. G.; Yeamans, C. B.

    2013-11-01

    Neutron yields at the National Ignition Facility (NIF) are measured with a suite of diagnostics, including activation of ˜20-200 g samples of materials undergoing a variety of energy-dependent neutron reactions. Indium samples were mounted on the end of a Diagnostic Instrument Manipulator (DIM), 25-50 cm from the implosion, to measure 2.45 MeV D-D fusion neutron yield. The 336.2 keV gamma rays from the 4.5 hour isomer of 115mIn produced by (n,n') reactions are counted in high-purity germanium detectors. For capsules producing D-T fusion reactions, zirconium and copper are activated via (n,2n) reactions at various locations around the target chamber and bay, measuring the 14 MeV neutron yield to accuracies on order of 7%. By mounting zirconium samples on ports at nine locations around the NIF chamber, anisotropies in the primary neutron emission due to fuel areal density asymmetries can be measured to a relative precision of 3%.

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

    NASA Technical Reports Server (NTRS)

    Laird, C. E.

    1982-01-01

    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.

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

    SciTech Connect

    Hep, J.; Konecna, A.; Krysl, V.; Smutny, V.

    2011-07-01

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

  16. Hard-X-ray spectra of active galactic nuclei in the INTEGRAL complete sample

    NASA Astrophysics Data System (ADS)

    Molina, M.; Bassani, L.; Malizia, A.; Stephen, J. B.; Bird, A. J.; Bazzano, A.; Ubertini, P.

    2013-08-01

    In this paper, we present the hard-X-ray spectral analysis of a complete sample of active galactic nuclei (AGNs) detected by INTEGRAL/IBIS. In conjunction with IBIS spectra, we make use of Swift/BAT data, with the aim of cross-calibrating the two instruments, studying source variability and constraining some important spectral parameters. We find that flux variability is present in at least 14 per cent of the sample, while spectral variability is found only in one object. There is general good agreement between BAT and IBIS spectra, despite a systematic mismatch of about 22 per cent in normalization. When fitted with a simple power-law model, type 1 and type 2 sources appear to have very similar average photon indices, suggesting that they are powered by the same mechanism. As expected, we also find that a simple power law does not always describe the data sufficiently well, thus indicating a certain degree of spectral complexity, which can be ascribed to features like a high energy cut-off and/or a reflection component. Fixing the reflection to be 0, 1 or 2, we find that our sample covers quite a large range in photon indices as well as cut-off energies; however, the spread is due only to a small number of objects, while the majority of the AGNs lie within well-defined boundaries of photon index (1 ≤ Γ ≤ 2) and cut-off energy (30 ≤ Ecut ≤ 300 keV).

  17. 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

    Osmera, B; Cvachovec, F; Kyncl, J; Smutný, V

    2005-01-01

    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 distributions have been calculated with the stochastic code MCNP and the deterministic three-dimensional code TORT. Selected results are presented and discussed in the paper. This work has been done in the frame of the EU 5th FW project REDOS REDOS, Reactor Dosimetry: Accurate determination and benchmarking of radiation field parameters, relevant for reactor pressure vessel monitoring. EURATOM Programme, Call 2000/C 294/04). All geometry and material composition data of the model as well as the available experimental data were carefully checked and revised.

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

    SciTech Connect

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

    1989-01-01

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

  19. TFT-Based Active Pixel Sensors for Large Area Thermal Neutron Detection

    NASA Astrophysics Data System (ADS)

    Kunnen, George

    Due to diminishing availability of 3He, which is the critical component of neutron detecting proportional counters, large area flexible arrays are being considered as a potential replacement for neutron detection. A large area flexible array, utilizing semiconductors for both charged particle detection and pixel readout, ensures a large detection surface area in a light weight rugged form. Such a neutron detector could be suitable for deployment at ports of entry. The specific approach used in this research, uses a neutron converter layer which captures incident thermal neutrons, and then emits ionizing charged particles. These ionizing particles cause electron-hole pair generation within a single pixel's integrated sensing diode. The resulting charge is then amplified via a low-noise amplifier. This document begins by discussing the current state of the art in neutron detection and the associated challenges. Then, for the purpose of resolving some of these issues, recent design and modeling efforts towards developing an improved neutron detection system are described. Also presented is a low-noise active pixel sensor (APS) design capable of being implemented in low temperature indium gallium zinc oxide (InGaZnO) or amorphous silicon (a-Si:H) thin film transistor process compatible with plastic substrates. The low gain and limited scalability of this design are improved upon by implementing a new multi-stage self-resetting APS. For each APS design, successful radiation measurements are also presented using PiN diodes for charged particle detection. Next, detection array readout methodologies are modeled and analyzed, and use of a matched filter readout circuit is described as well. Finally, this document discusses detection diode integration with the designed TFT-based APSs.

  20. neutron activation analysis using thermochromatography. III. analysis of samples of biological origin

    SciTech Connect

    Sattarov, G.; Davydov, A.V.; Khamatov, S.; Kist, A.A.

    1986-07-01

    The use of gas thermochromatography (GTC) in the radioactivation analysis of biological materials is discussed. A group separation of a number of highly volatile elements from sodium and bromine radionuclides has been achieved. The limit of detection of the elements by INAA and neutron activation analysis was estimated using GTC. The advantages of the procedure and the analytical parameters are discussed.

  1. Upgrade of the NIST Thermal Neutron Prompt-Gamma-Ray Activation Analysis Facility

    SciTech Connect

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

    2000-11-12

    The thermal neutron prompt-gamma-ray activation analysis facility at the National Institute of Standards and Technology (NIST) was designed and built in the late 1970s. An upgrade of the facility to reduce background and enhance analytical sensitivities is in progress, and is described in this report.

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

    USGS Publications Warehouse

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

    1963-01-01

    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.

  3. A neutron activation analysis of iridium concentration in Yamato carbonaceous chondrite

    NASA Astrophysics Data System (ADS)

    Yabushita, S.; Wada, K.; Moriyama, H.; Takeuchi, K.

    1988-09-01

    Iridium concentration in extra-terrestrial bodies is an important quantity in relation to Ir-rich geological layers. Ir concentration of a Yamato carbonaceous chondrite (Y-793321) has been measured by a neutron activation method. The measurement yields a value (0.57±0.06) μg per gramme for the chondrite.

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

    DOEpatents

    Lechtenberg, Thomas

    1985-01-01

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

  5. Radiochemical neutron activation analysis for certification of ion-implanted phosphorus in silicon.

    PubMed

    Paul, Rick L; Simons, David S; Guthrie, William F; Lu, John

    2003-08-15

    A radiochemical neutron activation analysis procedure has been developed, critically evaluated, and shown to have the necessary sensitivity, chemical specificity, matrix independence, and precision to certify phosphorus at ion implantation levels in silicon. 32P, produced by neutron capture of 31P, is chemically separated from the sample matrix and measured using a beta proportional counter. The method is used here to certify the amount of phosphorus in SRM 2133 (Phosphorus Implant in Silicon Depth Profile Standard) as (9.58 +/- 0.16) x 10(14) atoms x cm(-2). A detailed evaluation of uncertainties is given.

  6. Capability and limitation study of the DDT passive-active neutron waste assay instrument

    SciTech Connect

    Nicholas, N.J.; Coop, K.L.; Estep, R.J.

    1992-05-01

    The differential-dieaway-technique passive-active neutron assay system is widely used by transuranic waste generators to certify their drummed waste for eventual shipment to the Waste Isolation Pilot Plant (WIPP). Stricter criteria being established for waste emplacement at the WIPP site has led to a renewed interest in improvements to and a better understanding of current nondestructive assay (NDA) techniques. Our study includes the effects of source position, extreme matrices, high neutron backgrounds, and source self-shielding to explore the system`s capabilities and limitations and to establish a basis for comparison with other NDA systems. 11 refs.

  7. Capability and limitation study of the DDT passive-active neutron waste assay instrument

    SciTech Connect

    Nicholas, N.J.; Coop, K.L.; Estep, R.J.

    1992-05-01

    The differential-dieaway-technique passive-active neutron assay system is widely used by transuranic waste generators to certify their drummed waste for eventual shipment to the Waste Isolation Pilot Plant (WIPP). Stricter criteria being established for waste emplacement at the WIPP site has led to a renewed interest in improvements to and a better understanding of current nondestructive assay (NDA) techniques. Our study includes the effects of source position, extreme matrices, high neutron backgrounds, and source self-shielding to explore the system's capabilities and limitations and to establish a basis for comparison with other NDA systems. 11 refs.

  8. Innovative high pressure gas MEM's based neutron detector for ICF and active SNM detection.

    SciTech Connect

    Martin, Shawn Bryan; Derzon, Mark Steven; Renzi, Ronald F.; Chandler, Gordon Andrew

    2007-12-01

    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.

  9. A New Automated Sample Transfer System for Instrumental Neutron Activation Analysis

    PubMed Central

    Ismail, S. S.

    2010-01-01

    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

  10. Real-time measurement of low-energy-range neutron spectra on board the space shuttle STS-89 (S/MM-8).

    PubMed

    Matsumoto, H; Goka, T; Koga, K; Iwai, S; Uehara, T; Sato, O; Takagi, S

    2001-06-01

    We have developed a real-time, Bonner Ball-type (neutron energy range is from thermal to 15 MeV) neutron spectral measurement system (Bonner Ball Neutron Detector (BBND)) for use on board the International Space Station (ISS). From measurements taken inside STS-89 (S/MM-8), we successfully distinguished neutrons from protons and other particles in a mixed radiation field; a task hitherto considered difficult. Although the experimental period was short, only 3.5 days (January 24-27, 1998), we were able to obtain energy spectral data and the Earth's neutron dose-equivalent map for the ISS orbital conditions (altitude 400 km, orbit inclination angle 51.6 degrees). A method for calculating the neutron energy spectrum and compensating for the particle interaction with the sensors is also described in detail.

  11. Luminescent and scintillating properties of lanthanum fluoride nanocrystals in response to gamma/neutron irradiation: codoping with Ce activator, Yb wavelength shifter, and Gd neutron captor

    NASA Astrophysics Data System (ADS)

    Vargas, J. M.; Blostein, J. J.; Sidelnik, I.; Rondón Brito, D.; Rodríguez Palomino, L. A.; Mayer, R. E.

    2016-09-01

    A novel concept for gamma radiation detection and spectroscopy, and detection of thermal neutrons based on co-doped lanthanum fluoride nanocrystals containing gadolinium is presented. The trends of colloidal synthesis of the mentioned material, LaF3 co-doped with Ce3+ as the activator, Yb3+ as the wavelength-shifter and Gd3+ as the neutron captor, is reported. Nanocrystals of the mentioned material were characterized by transmission electron microscopy, X ray diffraction, energy dispersive X ray spectroscopy, optical absorption, and photoluminescence spectroscopy. Gamma detection and its potential spectroscopy feature have been confirmed. The neutron detection capability has been confirmed by experiments performed using a 252Cf neutron source.

  12. ANITA-2000 activation code package - updating of the decay data libraries and validation on the experimental data of the 14 MeV Frascati Neutron Generator

    NASA Astrophysics Data System (ADS)

    Frisoni, Manuela

    2016-03-01

    ANITA-2000 is a code package for the activation characterization of materials exposed to neutron irradiation released by ENEA to OECD-NEADB and ORNL-RSICC. The main component of the package is the activation code ANITA-4M that computes the radioactive inventory of a material exposed to neutron irradiation. The code requires the decay data library (file fl1) containing the quantities describing the decay properties of the unstable nuclides and the library (file fl2) containing the gamma ray spectra emitted by the radioactive nuclei. The fl1 and fl2 files of the ANITA-2000 code package, originally based on the evaluated nuclear data library FENDL/D-2.0, were recently updated on the basis of the JEFF-3.1.1 Radioactive Decay Data Library. This paper presents the results of the validation of the new fl1 decay data library through the comparison of the ANITA-4M calculated values with the measured electron and photon decay heats and activities of fusion material samples irradiated at the 14 MeV Frascati Neutron Generator (FNG) of the NEA-Frascati Research Centre. Twelve material samples were considered, namely: Mo, Cu, Hf, Mg, Ni, Cd, Sn, Re, Ti, W, Ag and Al. The ratios between calculated and experimental values (C/E) are shown and discussed in this paper.

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

    USGS Publications Warehouse

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

    1977-01-01

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

  14. Apparatus for the measurement of total body nitrogen using prompt neutron activation analysis with californium-252.

    PubMed

    Mackie, A; Hannan, W J; Smith, M A; Tothill, P

    1988-01-01

    Details of clinical apparatus designed for the measurement of total body nitrogen (as an indicator of body protein), suitable for the critically ill, intensive-care patient are presented. Californium-252 radio-isotopic neutron sources are used, enabling a nitrogen measurement by prompt neutron activation analysis to be made in 40 min with a precision of +/- 3.2% for a whole body dose equivalent of 0.145 mSv. The advantages of Californium-252 over alternative neutron sources are discussed. A comparison between two irradiation/detection geometries is made, leading to an explanation of the geometry adopted for the apparatus. The choice of construction and shielding materials to reduce the count rate at the detectors and consequently to reduce the pile-up contribution to the nitrogen background is discussed. Salient features of the gamma ray spectroscopy system to reduce spectral distortion from pulse pile-up are presented.

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

    SciTech Connect

    Ma, R.; Dilmanian, F.A..; Rarback, H.; Meron, M.; Kamen, Y.; Yasumura, S.; Weber, D.A.; Stamatelatos, I.E.; Lidofsky, L.J.; Pierson, R.N. Jr.

    1993-10-01

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

  16. Evaluation of equivalent dose from neutrons and activation products from a 15-MV X-ray LINAC.

    PubMed

    Israngkul-Na-Ayuthaya, Isra; Suriyapee, Sivalee; Pengvanich, Phongpheath

    2015-11-01

    A high-energy photon beam that is more than 10 MV can produce neutron contamination. Neutrons are generated by the [γ,n] reactions with a high-Z target material. The equivalent neutron dose and gamma dose from activation products have been estimated in a LINAC equipped with a 15-MV photon beam. A Monte Carlo simulation code was employed for neutron and photon dosimetry due to mixed beam. The neutron dose was also experimentally measured using the Optically Stimulated Luminescence (OSL) under various conditions to compare with the simulation. The activation products were measured by gamma spectrometer system. The average neutron energy was calculated to be 0.25 MeV. The equivalent neutron dose at the isocenter obtained from OSL measurement and MC calculation was 5.39 and 3.44 mSv/Gy, respectively. A gamma dose rate of 4.14 µSv/h was observed as a result of activations by neutron inside the treatment machine. The gamma spectrum analysis showed (28)Al, (24)Na, (54)Mn and (60)Co. The results confirm that neutrons and gamma rays are generated, and gamma rays remain inside the treatment room after the termination of X-ray irradiation. The source of neutrons is the product of the [γ,n] reactions in the machine head, whereas gamma rays are produced from the [n,γ] reactions (i.e. neutron activation) with materials inside the treatment room. The most activated nuclide is (28)Al, which has a half life of 2.245 min. In practice, it is recommended that staff should wait for a few minutes (several (28)Al half-lives) before entering the treatment room after the treatment finishes to minimize the dose received.

  17. Evaluation of equivalent dose from neutrons and activation products from a 15-MV X-ray LINAC.

    PubMed

    Israngkul-Na-Ayuthaya, Isra; Suriyapee, Sivalee; Pengvanich, Phongpheath

    2015-11-01

    A high-energy photon beam that is more than 10 MV can produce neutron contamination. Neutrons are generated by the [γ,n] reactions with a high-Z target material. The equivalent neutron dose and gamma dose from activation products have been estimated in a LINAC equipped with a 15-MV photon beam. A Monte Carlo simulation code was employed for neutron and photon dosimetry due to mixed beam. The neutron dose was also experimentally measured using the Optically Stimulated Luminescence (OSL) under various conditions to compare with the simulation. The activation products were measured by gamma spectrometer system. The average neutron energy was calculated to be 0.25 MeV. The equivalent neutron dose at the isocenter obtained from OSL measurement and MC calculation was 5.39 and 3.44 mSv/Gy, respectively. A gamma dose rate of 4.14 µSv/h was observed as a result of activations by neutron inside the treatment machine. The gamma spectrum analysis showed (28)Al, (24)Na, (54)Mn and (60)Co. The results confirm that neutrons and gamma rays are generated, and gamma rays remain inside the treatment room after the termination of X-ray irradiation. The source of neutrons is the product of the [γ,n] reactions in the machine head, whereas gamma rays are produced from the [n,γ] reactions (i.e. neutron activation) with materials inside the treatment room. The most activated nuclide is (28)Al, which has a half life of 2.245 min. In practice, it is recommended that staff should wait for a few minutes (several (28)Al half-lives) before entering the treatment room after the treatment finishes to minimize the dose received. PMID:26265661

  18. Evaluation of equivalent dose from neutrons and activation products from a 15-MV X-ray LINAC

    PubMed Central

    Israngkul-Na-Ayuthaya, Isra; Suriyapee, Sivalee; Pengvanich, Phongpheath

    2015-01-01

    A high-energy photon beam that is more than 10 MV can produce neutron contamination. Neutrons are generated by the [γ,n] reactions with a high-Z target material. The equivalent neutron dose and gamma dose from activation products have been estimated in a LINAC equipped with a 15-MV photon beam. A Monte Carlo simulation code was employed for neutron and photon dosimetry due to mixed beam. The neutron dose was also experimentally measured using the Optically Stimulated Luminescence (OSL) under various conditions to compare with the simulation. The activation products were measured by gamma spectrometer system. The average neutron energy was calculated to be 0.25 MeV. The equivalent neutron dose at the isocenter obtained from OSL measurement and MC calculation was 5.39 and 3.44 mSv/Gy, respectively. A gamma dose rate of 4.14 µSv/h was observed as a result of activations by neutron inside the treatment machine. The gamma spectrum analysis showed 28Al, 24Na, 54Mn and 60Co. The results confirm that neutrons and gamma rays are generated, and gamma rays remain inside the treatment room after the termination of X-ray irradiation. The source of neutrons is the product of the [γ,n] reactions in the machine head, whereas gamma rays are produced from the [n,γ] reactions (i.e. neutron activation) with materials inside the treatment room. The most activated nuclide is 28Al, which has a half life of 2.245 min. In practice, it is recommended that staff should wait for a few minutes (several 28Al half-lives) before entering the treatment room after the treatment finishes to minimize the dose received. PMID:26265661

  19. neutron activation analysis using thermochromatography. II. thermochromatographic separation of elements in the analysis of geological samples

    SciTech Connect

    Sattarov, G.; Davydov, A.V.; Khamatov, S.; Kist, A.A.

    1986-07-01

    The use of gas thermochromatography (GTC) in the radioactivation analysis of difficulty soluble samples with a strongly activating substrate is discussed. The effect of sample coarseness and ore type on the rate of extraction of gold and accompanying elements was studied. The limits of detection of 22 elements were compared using neutron activation analysis with GTC and INAA. The analytical parameters of the procedure were estimated.

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    The Pulsed Neutron Generator-Gamma Ray And Neutron Detectors (PNG-GRAND) experiment is an innovative application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA-GSFC) is to bring the PNG-GRAND instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Menus, asteroids, comets and the satellites of the outer planets. Gamma-Ray Spectrometers (GRS) have been incorporated into numerous orbital planetary science missions and, especially its the case of the Mars Odyssey GRS, have contributed detailed maps of the elemental composition over the entire surface of Mars. However, orbital gamma ray measurements have low spatial sensitivity (100's of km) due to their low surface emission rates from cosmic rays and subsequent need to be averaged over large surface areas. PNG-GRAND overcomes this impediment by incorporating a powerful neutron excitation source that permits high sensitivity surface and subsurface measurements of bulk elemental compositions. PNG-GRAND combines a pulsed neutron generator (PNG) with gamma ray and neutron detectors to produce a landed instrument to determine subsurface elemental composition without needing to drill into a planet's surface a great advantage in mission design. We are currently testing PNG-GRAND prototypes at a unique outdoor neutron instrumentation test facility recently constructed at NASA/GSFC that consists of a 2 m x 2 in x 1 m granite structure placed outdoors in an empty field. Because an independent trace elemental analysis has been performed on the material, this granite sample is a known standard with which to compare both Monte Carlo simulations and our experimentally measured elemental composition data. We will present data from operating PNG-GRAND in various experimental configurations on a

  1. Gamma/neutron analysis for SNM signatures at high-data rates(greater than 107 cps) for single-pulse active interrogation

    SciTech Connect

    Forman L.; Dioszegi, I.; Salwen, C.

    2011-04-26

    We are developing a high data gamma/neutron spectrometer suitable for active interrogation of special nuclear materials (SNM) activated by a single burst from an intense source. We have tested the system at Naval Research Laboratory's (NRL) Mercury pulsed-power facility at distances approaching 10 meters from a depleted uranium (DU) target. We have found that the gamma-ray field in the target room 'disappears' 10 milliseconds after the x-ray flash, and that gamma ray spectroscopy will then be dominated by isomeric states/beta decay of fission products. When a polyethylene moderator is added to the DU target, a time-dependent signature of the DU is produced by thermalized neutrons. We observe this signature in gamma-spectra measured consecutively in the 0.1-1.0 ms time range. These spectra contain the Compton edge line (2.2 MeV) from capture in hydrogen, and a continuous high energy gamma-spectrum from capture or fission in minority constituents of the DU.

  2. Neutron-emission measurements at a white neutron source

    SciTech Connect

    Haight, Robert C

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  3. Energy spectra of protons, deuterium, and helium nuclei during quiet solar activity periods in 1996-97

    NASA Astrophysics Data System (ADS)

    Kecskemety, Karoly

    A background reduction method based on pulse-height analysis (see accompanying paper by Valtonen et al.) is applied for the data of the ERNE and EPHIN energetic particle telescopes aboard SOHO. Energy spectra of protons, deuterons, 3He and 4He nuclei have been obtained during very low activity periods in 1996-97 in the energy range of 1.3 to 22 MeV/n. The proton spectra are comparable to the lowest spectra of the Ulysses (COSPIN/LET, 1996) and near-Earth IMP-8 (1985-87) measurements. Deuterons and 3He are only significantly seen above about 10 MeV/n, their spectra are consistent with an increase proportional to kinetic energy, expected for purely galactic origin.

  4. Neutron-induced nucleation inside bubble chambers using Freon 115 as the active medium

    NASA Astrophysics Data System (ADS)

    Ghilea, M. C.; Meyerhofer, D. D.; Sangster, T. C.

    2011-08-01

    Neutron imaging is used in inertial confinement fusion (ICF) experiments to measure the core symmetry of imploded targets. Liquid bubble chambers have the potential to obtain higher resolution images of the targets for a shorter source-target distance than typical scintillator arrays. Due to the fact that nucleation models used in gel detectors research cannot always give correct estimates for the neutron-induced bubble density inside a liquid bubble chamber, an improved theoretical model to describe the mechanism of bubble formation for Freon 115 as the active medium has been developed. It shows that the size of the critical radius for the nucleation process determines the mechanism of bubble formation and the sensitivity of the active medium to the 14.1-MeV incident neutrons resulting from ICF implosions. The bubble-growth mechanism is driven by the excitation of the medium electronic levels and not by electrons ejected from the medium's atoms as happens for the bubble chambers used to detect charged particles. The model accurately predicts the neutron-induced bubble density measured on OMEGA with both liquid bubble chambers and gel detectors.

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

    NASA Astrophysics Data System (ADS)

    Melnik, Dmitry G.; Miller, Terry A.

    2013-06-01

    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

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

    NASA Technical Reports Server (NTRS)

    Harper, Graham M.

    2002-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    1990-11-01

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

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

    SciTech Connect

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

    2010-07-15

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

  9. Benchmark test of transport calculations of gold and nickel activation with implications for neutron kerma at Hiroshima.

    PubMed

    Hoshi, M; Hiraoka, M; Hayakawa, N; Sawada, S; Munaka, M; Kuramoto, A; Oka, T; Iwatani, K; Shizuma, K; Hasai, H

    1992-11-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a 252Cf fission neutron source to validate the use of the code for the energy spectrum analyses of Hiroshima atomic bomb neutrons. Nuclear data libraries used in the Monte Carlo neutron and photon transport code calculation were ENDF/B-III, ENDF/B-IV, LASL-SUB, and ENDL-73. The neutron moderators used were granite (the main component of which is SiO2, with a small fraction of hydrogen), Newlight [polyethylene with 3.7% boron (natural)], ammonium chloride (NH4Cl), and water (H2O). Each moderator was 65 cm thick. The neutron detectors were gold and nickel foils, which were used to detect thermal and epithermal neutrons (4.9 eV) and fast neutrons (> 0.5 MeV), respectively. Measured activity data from neutron-irradiated gold and nickel foils in these moderators decreased to about 1/1,000th or 1/10,000th, which correspond to about 1,500 m ground distance from the hypocenter in Hiroshima. For both gold and nickel detectors, the measured activities and the calculated values agreed within 10%. The slopes of the depth-yield relations in each moderator, except granite, were similar for neutrons detected by the gold and nickel foils. From the results of these studies, the Monte Carlo neutron and photon transport code was verified to be accurate enough for use with the elements hydrogen, carbon, nitrogen, oxygen, silicon, chlorine, and cadmium, and for the incident 252Cf fission spectrum neutrons. PMID:1399639

  10. Benchmark test of transport calculations of gold and nickel activation with implications for neutron kerma at Hiroshima.

    PubMed

    Hoshi, M; Hiraoka, M; Hayakawa, N; Sawada, S; Munaka, M; Kuramoto, A; Oka, T; Iwatani, K; Shizuma, K; Hasai, H

    1992-11-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a 252Cf fission neutron source to validate the use of the code for the energy spectrum analyses of Hiroshima atomic bomb neutrons. Nuclear data libraries used in the Monte Carlo neutron and photon transport code calculation were ENDF/B-III, ENDF/B-IV, LASL-SUB, and ENDL-73. The neutron moderators used were granite (the main component of which is SiO2, with a small fraction of hydrogen), Newlight [polyethylene with 3.7% boron (natural)], ammonium chloride (NH4Cl), and water (H2O). Each moderator was 65 cm thick. The neutron detectors were gold and nickel foils, which were used to detect thermal and epithermal neutrons (4.9 eV) and fast neutrons (> 0.5 MeV), respectively. Measured activity data from neutron-irradiated gold and nickel foils in these moderators decreased to about 1/1,000th or 1/10,000th, which correspond to about 1,500 m ground distance from the hypocenter in Hiroshima. For both gold and nickel detectors, the measured activities and the calculated values agreed within 10%. The slopes of the depth-yield relations in each moderator, except granite, were similar for neutrons detected by the gold and nickel foils. From the results of these studies, the Monte Carlo neutron and photon transport code was verified to be accurate enough for use with the elements hydrogen, carbon, nitrogen, oxygen, silicon, chlorine, and cadmium, and for the incident 252Cf fission spectrum neutrons.

  11. Analysis of the size, shape, and spatial distribution of microinclusions by neutron-activation autoradiography

    SciTech Connect

    Flitsiyan, E.S.; Romanovskii, A.V.; Gurvich, L.G.; Kist, A.A.

    1987-02-01

    The local concentration and spatial distribution of some elements in minerals, rocks, and ores can be determined by means of neutron-activation autoradiography. The local element concentration is measured in this method by placing an activated section of the rock to be analyzed, together with an irradiated standard, against a photographic emulsion which acts as a radiation detector. The photographic density of the exposed emulsion varies as a function of the tested element content in the part of the sample next to the detector. In order to assess the value of neutron-activation autoradiography in the analysis of element distribution, we considered the main factors affecting the production of selective autoradiographs, viz., resolution, detection limit, and optimal irradiation conditions, holding time, and exposure.

  12. New models for carrying out cyclic neutron activation. Discussion of the theoretical response

    NASA Astrophysics Data System (ADS)

    Castro-García, M. P.; Rey-Ronco, M. A.; Alonso-Sánchez, T.

    2014-11-01

    This paper studies two specific procedures for analyzing mining samples through a neutron activation technique called DGNAA (Delayed Gamma Neutron Activation Analysis). This particular study is part of a broader line of research, whose overall objective is to find the optimal procedure for analyzing the fluorite content of samples taken from different parts of a fluorite concentration plant, using the DGNAA method [1-2]. The mining sample is fluorspar, which contains other minerals in addition to fluorite, such as silica, barite, iron oxides and silicates. The main contribution of the article is the development of a new method for determining the fluorite content in minerals and the increase of sensitivity in respect to the symmetrical method and single-cycle activation.

  13. Chromospheric activity and lithium line variations in the spectra of the spotted star LQ Hydrae

    NASA Astrophysics Data System (ADS)

    Flores Soriano, M.; Strassmeier, K. G.; Weber, M.

    2015-03-01

    Context. Although the relationship between lithium abundance in stars and their magnetic activity is commonly accepted, it is still unclear how the different phenomena related to it can increase the amount of Li, reduce its depletion, or be a source of bias for the measurements. Aims: We study the rotational modulation of chromospheric and photospheric parameters of the young, active, single K2 dwarf LQ Hya and their connection with the variability of the Li i 6708 Å line. Methods: A total of 199 high-resolution STELLA spectra and quasi-simultaneous photometry were used to compute effective temperature, gravity, and chromospheric activity indicators such as Hα and Hβ emission, Balmer decrement, and chromospheric electron density, as a function of the rotational phase. The variation of the Li i 6708 Å line was characterized in terms of equivalent width, abundance, and of 6Li/7Li isotopic ratio in the form of line shifts. Results: Photospheric and chromospheric parameters show clear rotational modulation. Effective temperatures and continuum variations reveal a higher concentration of cool spots on the side of the star on which we also detect stronger chromospheric activity. Increased electron densities and the modulation of the He i D3 line suggest that the source of this activity can be a combination of plages and repeated low-intensity flares. The Li line and other temperature-sensitive lines are clearly enhanced by the spots located on the most active side of the star. Li abundances calculated taking into account the temperature variations simultaneously show, although with high dispersion, a small overabundance of this element that correlates well with the surface magnetic activity. In addition, the Li line center is more intensely redshifted than in the other hemisphere, which might be interpreted as a weak enrichment of 6Li. Based on data obtained with the STELLA robotic telescope in Tenerife, an AIP facility jointly operated by AIP and IAC, and the Vienna

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

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    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.

  15. A History of In Vivo Neutron Activation Analysis in Measurement of Aluminum in Human Subjects.

    PubMed

    Mohseni, Hedieh K; Chettle, David R

    2016-01-01

    Aluminum, as an abundant metal, has gained widespread use in human life, entering the body predominantly as an additive to various foods and drinking water. Other major sources of exposure to aluminum include medical, cosmetic, and occupational routes. As a common environmental toxin, with well-known roles in several medical conditions such as dialysis encephalopathy, aluminum is considered a potential candidate in the causality of Alzheimer's disease. Aluminum mostly accumulates in the bone, which makes bone an indicator of the body burden of aluminum and an ideal organ as a proxy for the brain. Most of the techniques developed for measuring aluminum include bone biopsy, which requires invasive measures, causing inconvenience for the patients. There has been a considerable effort in developing non-invasive approaches, which allow for monitoring aluminum levels for medical and occupational purposes in larger populations. In vivo neutron activation analysis, a method based on nuclear activation of isotopes of elements in the body and their subsequent detection, has proven to be an invaluable tool for this purpose. There are definite challenges in developing in vivo non-invasive techniques capable of detecting low levels of aluminum in healthy individuals and aluminum-exposed populations. The following review examines the method of in vivo neutron activation analysis in the context of aluminum measurement in humans focusing on different neutron sources, interference from other activation products, and the improvements made in minimum detectable limits and patient dose over the past few decades.

  16. Consequences of Relativistic Neutron Outflow beyond the Accretion Disks of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Ekejiuba, I. E.; Okeke, P. N.

    1993-05-01

    Three channels of relativistic electron injection in the jets of extragalactic radio sources (EGRSs) are discussed. With the assumption that an active galactic nucleus (AGN) is powered by a spinning supermassive black hole of mass ~ 10(8) M_⊙ which sits at the center of the nucleus and ingests matter and energy through an accretion disk, a model for extracting relativistic neutrons from the AGN is forged. In this model, the inelastic proton--proton and proton--photon interactions within the accretion disk, of relativistic protons with background thermal protons and photons, respectively, produce copious amounts of relativistic neutrons. These neutrons travel ballistically for ~ 10(3gamma_n ) seconds and escape from the disk before they decay. The secondary particles produced from the neutron decays then interact with the ambient magnetic field and/or other particles to produce the radio emissions observed in the jets of EGRSs. IEE acknowledges the support of the World Bank and the Federal University of Technology, Yola, Nigeria as well as the hospitality of Georgia State University.

  17. Active and passive mode calibration of the Combined Thermal Epithermal Neutron (CTEN) system

    SciTech Connect

    Veilleux, J. M.

    2002-06-01

    The Combined Thermal/Epithermal Neutron (CTEN) non-destructive assay (NDA) system was designed to assay transuranic waste by employing an induced active neutron interrogation and/or a spontaneous passive neutron measurement. This is the second of two papers, and focuses on the passive mode, relating the net double neutron coincidence measurement to the plutonium mass via the calibration constant. National Institute of Standards and Technology (NIST) calibration standards were used and the results verified with NIST-traceable verification standards. Performance demonstration program (PDP) 'empty' 208-L matrix drum was used for the calibration. The experimentally derived calibration constant was found to be 0.0735 {+-} 0.0059 g {sup 240}Pu effective per unit response. Using this calibration constant, the Waste Isolation Pilot Plant (WIPP) criteria was satisfied with five minute waste assays in the range from 3 to 177g Pu. CTEN also participated in the PDP Cycle 8A blind assay with organic sludge and metal matrices and passed the criteria for accuracy and precision in both assay modes. The WIPP and EPA audit was completed March 1, 2002 and full certification is awaiting the closeout of one finding during the audit. With the successful closeout of the audit, the CTEN system will have shown that it can provide very fast assays (five minutes or less) of waste in the range from the minimum detection limit (about 2 mg Pu) to 177 g Pu.

  18. Transitions, cross sections and neutron binding energy in 186Re by Prompt Gamma Activation Analysis

    NASA Astrophysics Data System (ADS)

    Lerch, A. G.; Hurst, A. M.; Firestone, R. B.; Revay, Zs.; Szentmiklosi, L.; McHale, S. R.; McClory, J. W.; Detwiler, B.; Carroll, J. J.

    2014-03-01

    The nuclide 186Re possesses an isomer with 200,000 year half-life while its ground state has a half-life of 3.718 days. It is also odd-odd and well-deformed nucleus, so should exhibit a variety of other interesting nuclear-structure phenomena. However, the available nuclear data is rather sparse; for example, the energy of the isomer is only known to within + 7 keV and, with the exception of the J?=1- ground state, every proposed level is tentative in the ENSDF. Previously, Prompt Gamma Activation Analysis (PGAA) was utilized to study natRe with 186,188Re being produced via thermal neutron capture. Recently, an enriched 185Re target was irradiated by thermal neutrons at the Budapest Research Reactor to build on those results. Prompt (primary and secondary) and delayed gamma-ray transitions were measured with a large-volume, Compton-suppressed HPGe detector. Absolute cross sections for each gamma transition were deduced and corrected for self attenuation within the sample. Fifty-two primary gamma-ray transitions were newly identified and used to determine a revised value of the neutron binding energy. DICEBOX was used to simulate the decay scheme and the total radiative thermal neutron capture cross section was found to be 97+/-3 b Supported by DTRA (Detwiler) through HDTRA1-08-1-0014.

  19. X-ray spectra and time variability of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.

    1984-01-01

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

  20. A neutron activation analysis procedure for the determination of uranium, thorium and potassium in geologic samples

    USGS Publications Warehouse

    Aruscavage, P. J.; Millard, H.T.

    1972-01-01

    A neutron activation analysis procedure was developed for the determination of uranium, thorium and potassium in basic and ultrabasic rocks. The three elements are determined in the same 0.5-g sample following a 30-min irradiation in a thermal neutron flux of 2??1012 n??cm-2??sec-1. Following radiochemical separation, the nuclides239U (T=23.5 m),233Th (T=22.2 m) and42K (T=12.36 h) are measured by ??-counting. A computer program is used to resolve the decay curves which are complex owing to contamination and the growth of daughter activities. The method was used to determine uranium, throium and potassium in the U. S. Geological Survey standard rocks DTS-1, PCC-1 and BCR-1. For 0.5-g samples the limits of detection for uranium, throium and potassium are 0.7, 1.0 and 10 ppb, respectively. ?? 1972 Akade??miai Kiado??.

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

    SciTech Connect

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

    1983-01-01

    Ceramic specimens from the excavations of the Agora of ancient Athens, Greece, including material from factories, i.e., trial firing pieces, pottery and figurine wasters, datable to the Protogeometric, Subgeometric, and Classical Periods, and stylistically related figurines and pottery were analyzed by neutron activation. The factory material from the three distinct chronological periods separated respectively into three significantly different compositional groups, indicating either that separate sources of clay were used during each of these periods or that some other significant changes in the traditions of fabrication had occurred. Many of the figurines and sherds analyzed coincided in composition with one of these three groups and therefore were shown to be consistent with the output of Athenian workshops. Some specimens of Corinthian style formed a separate compositional group as did some other specimens that agreed in composition with a clay from Aegina. Comparison of these results with previous analyses on file in the Brookhaven Data Bank revealed a number of specimens that corresponded both in style and composition to the Agora material. Most significant was a sizable amount of Classical Greek pottery excavated in southern France, in Israel, and in Cyprus that conformed in composition to the Attic Classical Group. 6 figures, 2 tables.

  2. Determination of thorium in seawater by neutron activation analysis and mass spectrometry

    SciTech Connect

    Huh, Chih-An

    1987-01-01

    The recent development of neutron activation analysis and mass spectrometric methods for the determination of /sup 232/Th in seawater has made possible rapid sampling and analysis of this long-lived, non-radiogenic thorium isotope on small-volume samples. The marine geochemical utility of /sup 232/Th, whose concentration in seawater is extremely low, warrants the development of these sensitive techniques. The analytical methods and some results are presented and discussed in this article. 24 refs., 3 figs.

  3. Survey of trace elements in coals and coal-related materials by neutron activation analysis

    USGS Publications Warehouse

    Ruch, R.R.; Cahill, R.A.; Frost, J.K.; Camp, L.R.; Gluskoter, H.J.

    1977-01-01

    Utilizing primarily instrumental neutron activation analysis (INAA) and other analytical methods as many as 61 elements were quantitatively surveyed in 170 U.S. whole coals, 70 washed coals, and 40 bench samples. Data on areal and vertical distributions in various regions were obtained along with extensive information on the mode of occurrence of various elements in the coal matrix itself. ?? 1977 Akade??miai Kiado??.

  4. Instrumental neutron activation analysis of soil and sediment samples from Siwa Oasis, Egypt

    NASA Astrophysics Data System (ADS)

    Badawy, Wael M.; Ali, Khaled; El-Samman, Hussein M.; Frontasyeva, Marina V.; Gundorina, Svetlana F.; Duliu, Octavian G.

    2015-07-01

    Instrumental neutron activation analysis was used to study geochemical peculiarities of the Siwa Oasis in the Western Egyptian Desert. A total of 34 elements were determined in soil and sediment samples (Na, Mg, Al, Cl, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, As, Br, Rb, Sr, Zr, Sb, I, Cs, Ba, La, Ce, Nd, Eu, Tb, Dy, Tm, Yb, Hf, Ta, Th, and U). For data interpretation Cluster analysis was applied. Comparison with the available literature data was carried out.

  5. Neutron activation analysis of modern pottery: Insights for archaeological provenance research

    SciTech Connect

    Neff, H.; Arnold, D.E.; Benco, N.L.; Thieme, M.S.

    1996-12-31

    Neutron activation analysis has been employed to characterize ceramics and raw material samples from modern pottery-making communities. The original study focused on several villages in the central highlands of Guatemala. More recently, NAA data have been collected from communities in the Valley of Oaxaca, Mexico, the northern Yucatan Peninsula, and northern Morocco. The results from all four studies can now be combined to yield a comparative perspective on paste preparation effects in archaeological provenance research.

  6. Epithermal Neutron Activation Analysis of Some Geological Samples of Different Origin

    SciTech Connect

    Duliu, O. G.; Cristache, C. I.; Oaie, G.; Ricman, C.; Culicov, O. A.; Frontasyeva, M. V.

    2010-01-21

    Instrumental Epithermal Neutron Activation Analysis was used to investigate the distribution of six major elements and 34 trace elements in a set of eight igneous and metamorphic rocks collected from Carpathian and Macin Mountainsas well as unconsolidated sediments collected from anoxic zone of the Black Sea. All experimental data were interpreted within the Upper Continental Core and Mid Ocean Ridge Basalt model system that allowed getting more information concerning samples origin as well as the environmental peculiarities.

  7. Determination of selected trace elements in foodstuffs and biological materials by destructive neutron activation analysis.

    PubMed

    Bayat, I; Etehadiyan, M; Ansar, M

    1995-01-01

    Concentration of trace elements in Nescafé, Fariman sugar, and Sadaf turmeric and mercury content in cancerous blood were determined by radiochemical, neutron activation analysis. By this separation method levels of 110mAg, 198Au, 203Hg, 76Se, 51Cr, 24Na, 42K, 99Mo, 122Sb, 82Br, 59Fe, 60Co were measured without interference in the gamma spectroscopy. A nondestructive method has also been used for the analysis of sodium, potassium, and bromine. PMID:8748216

  8. Neutron activation analysis for reference determination of the implantation dose of cobalt ions

    SciTech Connect

    Garten, R.P.H.; Bubert, H.; Palmetshofer, L.

    1992-05-15

    The authors prepared depth profilling reference materials by cobalt ion implantation at an ion energy of 300 keV into n-type silicon. The implanted Co dose was then determined by instrumental neutron activation analysis (INAA) giving an analytical dynamic range of almost 5 decades and uncertainty of 1.5%. This form of analysis allows sources of error (beam spreading, misalignment) to be corrected. 70 refs., 3 tabs.

  9. HPGe well-type detectors for neutron activation measurements on the Frascati Tokamak Upgrade tokamak

    SciTech Connect

    Bertalot, L.; Damiani, M.; Esposito, B.; Lagamba, L.; Podda, S.; Batistoni, P.; De Felice, P.; Biagini, R.

    1997-01-01

    We describe an improvement of the neutron activation system in operation on the Frascati Tokamak Upgrade (FTU) tokamak for the measurement of the total neutron yield. A HPGe well-type detector (200 cm{sup 3} active volume) is used to detect the photoemission from neutron activated samples ({sup 115m}In336.2 keV {gamma} rays from DD neutrons on indium for FTU). Due to their high geometrical efficiency, HPGe well-type detectors are particularly suited to the FTU low-level activity measurements. A particular effort has been devoted to the calibration of the measuring system. In particular, a multi-{gamma} calibration source (59{endash}1332 keV energy range) with a density of 7.31 g/cm{sup 3} consisting of a stack of indium foils has been prepared. This assures that the shape and volume of the calibration source are the same as those of the samples used in the actual measurements. The full-energy-peak efficiency at the {sup 115m}In336.2 keV line is 0.197 with an overall uncertainty of 2{percent} (1{sigma}). For a better characterization of the detector response as a function of the sample density, a further calibration source with the same geometry has been prepared in a gel aqueous solution (density {approximately}1 g/cm{sup 3}). The calibration curves for the well-type detector at the two different density values are compared. {copyright} {ital 1997 American Institute of Physics.}

  10. A study of neutron radiation quality with a tissue-equivalent proportional counter for a low-energy accelerator-based in vivo neutron activation facility.

    PubMed

    Aslam; Waker, A J

    2011-02-01

    The accelerator-based in vivo neutron activation facility at McMaster University has been used successfully for the measurement of several minor and trace elements in human hand bones due to their importance to health. Most of these in vivo measurements have been conducted at a proton beam energy (E(p)) of 2.00 MeV to optimise the activation of the selected element of interest with an effective dose of the same order as that received in chest X rays. However, measurement of other elements at the same facility requires beam energies other than 2.00 MeV. The range of energy of neutrons produced at these proton beam energies comes under the region where tissue-equivalent proportional counters (TEPCs) are known to experience difficulty in assessing the quality factor and dose equivalent. In this study, the response of TEPCs was investigated to determine the quality factor of neutron fields generated via the (7)Li(p, n)(7)Be reaction as a function of E(p) in the range 1.884-2.56 MeV at the position of hand irradiation in the facility. An interesting trend has been observed in the quality factor based on ICRP 60, Q(ICRP60), such that the maximum value was observed at E(p)=1.884 MeV (E(n)=33±16 keV) and then continued to decline with increasing E(p) until achieving a minimum value at E(p)=2.0 MeV despite a continuous increase in the mean neutron energy with E(p). This observation is contrary to what has been observed with direct fast neutrons where the quality factor was found to increase continuously with an increase in E(p) (i.e. increasing E(n)). The series of measurements conducted with thermal and fast neutron fields demonstrate that the (14)N(n, p)(14)C produced 580 keV protons in the detector play an important role in the response of the counter under 2.0 MeV proton energy (E(n) ≤ 250 keV). In contrast to the lower response of TEPCs to low-energy neutrons, the quality factor is overestimated in the range 1-2 depending on beam energy <2.0 MeV. This study provides

  11. FY15 Status Report on NEAMS Neutronics Activities

    SciTech Connect

    Lee, C. H.; Shemon, E. R.; Smith, M. A.; Connaway, H. M.; Aliberti, G.

    2015-09-30

    This report summarizes the current status of NEAMS activities in FY2015. The tasks this year are (1) to improve solution methods for steady-state and transient conditions, (2) to develop features and user friendliness to increase the usability and applicability of the code, (3) to improve and verify the multigroup cross section generation scheme, (4) to perform verification and validation tests of the code using SFRs and thermal reactor cores, and (5) to support early users of PROTEUS and update the user manuals.

  12. Facility for Ground Tests with Active Neutron Instrumentation for the Planetary Science Missions

    NASA Astrophysics Data System (ADS)

    Litvak, Maxim; Jun, Insoo; Kozyrev, Alexander; Mitrofanov, Igor; Sanin, Anton; Shvetsov, Valery; Starr, Richard; Timoshenko, Gennady

    2015-04-01

    To conduct a feasibility study of active neutron and gamma spectrometers a special radiation test facility has been developed and built at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia. It has total area of about 62 m2 and with height from floor to roof up to 3.5 m. To provide measurements with prototypes of space instruments developed for the nuclear planetology applications and to test capabilities of such instruments we have designed and constructed special soil targets similar to planetary material with known elemental composition, appropriate geometry and layered structure. Here we also present results of first experimental work performed with a spare flight model of the DAN/MSL instrument selected as a flight prototype of an active neutron spectrometer applicable for the future landed missions to various solid solar system bodies. In our experiment we have tested the capability of neutron activation methods to detect thin layers of water/water ice lying on top of planetary dry regolith or buried within a dry regolith at different depths.

  13. Radiography apparatus using gamma rays emitted by water activated by fusion neutrons

    DOEpatents

    Smith, D.L.; Ikeda, Yujiro; Uno, Yoshitomo

    1996-11-05

    Radiography apparatus includes an arrangement for circulating pure water continuously between a location adjacent a source of energetic neutrons, such as a tritium target irradiated by a deuteron beam, and a remote location where radiographic analysis is conducted. Oxygen in the pure water is activated via the {sup 16}O(n,p){sup 16}N reaction using {sup 14}N-MeV neutrons produced at the neutron source via the {sup 3}H(d,n){sup 4}He reaction. Essentially monoenergetic gamma rays at 6.129 (predominantly) and 7.115 MeV are produced by the 7.13-second {sup 16}N decay for use in radiographic analysis. The gamma rays have substantial penetrating power and are useful in determining the thickness of materials and elemental compositions, particularly for metals and high-atomic number materials. The characteristic decay half life of 7.13 seconds of the activated oxygen is sufficient to permit gamma ray generation at a remote location where the activated water is transported, while not presenting a chemical or radioactivity hazard because the radioactivity falls to negligible levels after 1--2 minutes. 15 figs.

  14. Radiography apparatus using gamma rays emitted by water activated by fusion neutrons

    DOEpatents

    Smith, Donald L.; Ikeda, Yujiro; Uno, Yoshitomo

    1996-01-01

    Radiography apparatus includes an arrangement for circulating pure water continuously between a location adjacent a source of energetic neutrons, such as a tritium target irradiated by a deuteron beam, and a remote location where radiographic analysis is conducted. Oxygen in the pure water is activated via the .sup.16 O(n,p).sup.16 N reaction using .sup.14 -MeV neutrons produced at the neutron source via the .sup.3 H(d,n).sup.4 He reaction. Essentially monoenergetic gamma rays at 6.129 (predominantly) and 7.115 MeV are produced by the 7.13-second .sup.16 N decay for use in radiographic analysis. The gamma rays have substantial penetrating power and are useful in determining the thickness of materials and elemental compositions, particularly for metals and high-atomic number materials. The characteristic decay half life of 7.13 seconds of the activated oxygen is sufficient to permit gamma ray generation at a remote location where the activated water is transported, while not presenting a chemical or radioactivity hazard because the radioactivity falls to negligible levels after 1-2 minutes.

  15. Impurities analysis of polycrystalline silicon substrates: Neutronic Activation Analysis (NAA) and Secondary Ion Mass Spectrometry (SIMS)

    NASA Astrophysics Data System (ADS)

    Lounis, A.; Lenouar, K.; Gritly, Y.; Abbad, B.; Azzaz, M.; Taïbi, K.

    2010-01-01

    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 mm×100 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 2.1012neutron cm-2 s-1 during 15 min. The energetic profile of incidental flux is constituted of fast neutrons (ΦR = 3.1012n.cm-2 s-1; E = 2 Mev), thermal neutrons (ΦTH = 1013n.cm-2 s-1; E = 0.025 ev) and epithermal neutrons (Φepi = 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.

  16. Residual Nuclide Production from Iron, Lead, and Uranium by Neutron-Induced Reactions up to 180 MeV

    SciTech Connect

    Michel, R.; Glasser, W.; Herpers, U.; Schuhmacher, H.; Brede, H.J.; Dangendorf, V.; Nolte, R.; Malmborg, P.; Prokofiev, A.V.; Smirnov, A.N.; Rishkov, I.; Kollar, D.; Meulders, J.P.; Duijvestijn, M.; Koning, A.

    2005-05-24

    Within the HINDAS project, activation experiments with quasi mono-energetic neutrons were performed at UCL and TSL. Cross sections for the production of residual radionuclides were derived from the measured activities by unfolding, based on the neutron spectra inside the target stacks and starting from 'guess' excitation functions. Exemplary results are presented and are compared with theoretical calculations using the TALYS code.

  17. Neutron activation analysis of airborne thorium liberated during welding operations

    SciTech Connect

    Glasgow, D.C.; Robinson, L.; Janjovic, J.T.

    1996-02-01

    Typically, reactive metals such as aluminum are welded using a thoriated tungsten welding electrode which is attached to a source of argon gas such that the local atmosphere around the weld is inert. The metal is heated by the arc formed between the electrode and the grounded component to be welded. During this process, some of the electrode is vaporized in the arc and is potentially liberated to the surrounding air. This situation may result in a hazardous airborne thorium level. Because the electrode is consumed during welding, the electrode tip must be repeatedly dressed by grinding the tip to a fine point so that the optimal welding conditions are maintained. These grinding activities may also release thorium to the air. Data generated in the 1950s suggested that these electrodes posed no significant health hazard and seemed to justify their exemption from licensing requirements for source material. Since that time, other studies have been performed and present conflicting results as to the level of risk. Values both above and below the health protection limit in use in the United States, have been reported in the literature recently. This study is being undertaken to provide additional data which may be useful in evaluating both the chemical toxicity risk and radiological dose assessment criteria associated with thoriated tungsten welding operations.

  18. Neutron activation analysis of airborne thorium liberated during welding operations

    SciTech Connect

    Glasgow, D.C.; Robinson, L.; Jankovic, J.T.

    1996-12-31

    Typically, reactive metals such as aluminum are welded using a thoriated tungsten welding electrode that is attached to a source of argon gas such that the local atmosphere around the weld is inert. The metal is heated by the arc formed between the electrode and the grounded component to be welded. During this process, some of the electrode is vaporized in the arc and may be liberated to the surrounding air. This situation may result in a hazardous airborne thorium level. Because the electrode is consumed during welding, the electrode tip must be repeatedly dressed by grinding the tip to a fine point so that the optimal welding conditions are maintained. These grinding activities may also release thorium to the air. Data generated in the 1950s suggested that these electrodes posed no significant health hazard and seemed to justify their exemption from licensing requirements for source material. Since that time, other studies have been performed and present conflicting results as to the level of risk. Values both above and below the health protection limit in use in the United States have been reported in the literature recently. This study is being undertaken to provide additional data that may be useful in evaluating both the chemical toxicity risk and radiological dose assessment criteria associated with thoriated tungsten welding operations.

  19. Spatially resolved spectra of the 'teacup' active galactic nucleus: tracing the history of a dying quasar

    SciTech Connect

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

    2014-09-01

    The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number of spectacular galaxies possessing extended emission-line regions (EELRs), the most famous being Hanny's Voorwerp galaxy. We present another EELR object discovered in the SDSS endeavor: the Teacup active galactic nucleus (AGN). Nicknamed for its EELR, which has a 'handle'-like structure protruding 15 kpc into the northeast quadrant of the galaxy. We analyze the physical conditions of this galaxy with long-slit, ground-based spectroscopy from the Lowell, Lick, and KPNO observatories. With the Lowell 1.8 m Perkin's telescope we took multiple observations at different offset positions, allowing us to recover spatially resolved spectra across the galaxy. Line diagnostics indicate the ionized gas is photoionized primarily by the AGN. Additionally we are able to derive the hydrogen density from the [S II] λ6716/λ6731 ratio. We generated two-component photoionization models for each spatially resolved Lowell spectrum. These models allow us to calculate the AGN bolometric luminosity seen by the gas at different radii from the nuclear center of the Teacup. Our results show a drop in bolometric luminosity by more than two orders of magnitude from the EELR to the nucleus, suggesting that the AGN has decreased in luminosity by this amount in a continuous fashion over 46,000 yr, supporting the case for a dying AGN in this galaxy independent of any IR based evidence. We demonstrate that spatially resolved photoionization modeling could be applied to EELRs to investigate long timescale variability.

  20. Revisiting the infrared spectra of active galactic nuclei with a new torus emission model

    NASA Astrophysics Data System (ADS)

    Fritz, J.; Franceschini, A.; Hatziminaoglou, E.

    2006-03-01

    We describe improved modelling of the emission by dust in a toroidal-like structure heated by a central illuminating source within active galactic nuclei (AGNs). We have chosen a simple but realistic torus geometry, a flared disc, and a dust grain distribution function including a full range of grain sizes. The optical depth within the torus is computed in detail taking into account the different sublimation temperatures of the silicate and graphite grains, which solves previously reported inconsistencies in the silicate emission feature in type 1 AGNs. We exploit this model to study the spectral energy distributions (SEDs) of 58 extragalactic (both type 1 and type 2) sources using archival optical and infrared data. We find that both AGN and starburst contributions are often required to reproduce the observed SEDs, although in a few cases they are very well fitted by a pure AGN component. The AGN contribution to the far-infrared luminosity is found to be higher in type 1 sources, with all the type 2 requiring a substantial contribution from a circumnuclear starburst. Our results appear in agreement with the AGN unified scheme, because the distributions of key parameters of the torus models turn out to be compatible for type 1 and type 2 AGNs. Further support to the unification concept comes from comparison with medium-resolution infrared spectra of type 1 AGNs by the Spitzer observatory, showing evidence for a moderate silicate emission around 10 μm, which our code reproduces. From our analysis we infer accretion flows in the inner nucleus of local AGNs characterized by high equatorial optical depths (AV~= 100), moderate sizes (Rmax < 100 pc) and very high covering factors (f~= 80 per cent) on average.