Sample records for absolute neutron spectrum

  1. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF

    DOE PAGES

    Casey, D. T.; Frenje, J. A.; Gatu Johnson, M.; ...

    2013-04-18

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, iontemperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describesmore » ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.« less

  2. The magnetic recoil spectrometer for measurements of the absolute neutron spectrum at OMEGA and the NIF.

    PubMed

    Casey, D T; Frenje, J A; Johnson, M Gatu; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Katz, J; Magoon, J; Meyerhofer, D D; Sangster, T C; Shoup, M; Ulreich, J; Ashabranner, R C; Bionta, R M; Carpenter, A C; Felker, B; Khater, H Y; LePape, S; MacKinnon, A; McKernan, M A; Moran, M; Rygg, J R; Yeoman, M F; Zacharias, R; Leeper, R J; Fletcher, K; Farrell, M; Jasion, D; Kilkenny, J; Paguio, R

    2013-04-01

    The neutron spectrum produced by deuterium-tritium (DT) inertial confinement fusion implosions contains a wealth of information about implosion performance including the DT yield, ion-temperature, and areal-density. The Magnetic Recoil Spectrometer (MRS) has been used at both the OMEGA laser facility and the National Ignition Facility (NIF) to measure the absolute neutron spectrum from 3 to 30 MeV at OMEGA and 3 to 36 MeV at the NIF. These measurements have been used to diagnose the performance of cryogenic target implosions to unprecedented accuracy. Interpretation of MRS data requires a detailed understanding of the MRS response and background. This paper describes ab initio characterization of the system involving Monte Carlo simulations of the MRS response in addition to the commission experiments for in situ calibration of the systems on OMEGA and the NIF.

  3. Measuring the absolute deuterium-tritium neutron yield using the magnetic recoil spectrometer at OMEGA and the NIF.

    PubMed

    Casey, D T; Frenje, J A; Gatu Johnson, M; Séguin, F H; Li, C K; Petrasso, R D; Glebov, V Yu; Katz, J; Knauer, J P; Meyerhofer, D D; Sangster, T C; Bionta, R M; Bleuel, D L; Döppner, T; Glenzer, S; Hartouni, E; Hatchett, S P; Le Pape, S; Ma, T; MacKinnon, A; McKernan, M A; Moran, M; Moses, E; Park, H-S; Ralph, J; Remington, B A; Smalyuk, V; Yeamans, C B; Kline, J; Kyrala, G; Chandler, G A; Leeper, R J; Ruiz, C L; Cooper, G W; Nelson, A J; Fletcher, K; Kilkenny, J; Farrell, M; Jasion, D; Paguio, R

    2012-10-01

    A magnetic recoil spectrometer (MRS) has been installed and extensively used on OMEGA and the National Ignition Facility (NIF) for measurements of the absolute neutron spectrum from inertial confinement fusion implosions. From the neutron spectrum measured with the MRS, many critical implosion parameters are determined including the primary DT neutron yield, the ion temperature, and the down-scattered neutron yield. As the MRS detection efficiency is determined from first principles, the absolute DT neutron yield is obtained without cross-calibration to other techniques. The MRS primary DT neutron measurements at OMEGA and the NIF are shown to be in excellent agreement with previously established yield diagnostics on OMEGA, and with the newly commissioned nuclear activation diagnostics on the NIF.

  4. 237Np absolute delayed neutron yield measurements

    NASA Astrophysics Data System (ADS)

    Doré, D.; Ledoux, X.; Nolte, R.; Gagnon-Moisan, F.; Thulliez, L.; Litaize, O.; Roettger, S.; Serot, O.

    2017-09-01

    237Np absolute delayed neutron yields have been measured at different incident neutron energies from 1.5 to 16 MeV. The experiment was performed at the Physikalisch-Technische Bundesanstalt (PTB) facility where the Van de Graaff accelerator and the cyclotron CV28 delivered 9 different neutron energy beams using p+T, d+D and d+T reactions. The detection system is made up of twelve 3He tubes inserted into a polyethylene cylinder. In this paper, the experimental setup and the data analysis method are described. The evolution of the absolute DN yields as a function of the neutron incident beam energies are presented and compared to experimental data found in the literature and data from the libraries.

  5. 242Pu absolute neutron-capture cross section measurement

    NASA Astrophysics Data System (ADS)

    Buckner, M. Q.; Wu, C. Y.; Henderson, R. A.; Bucher, B.; Chyzh, A.; Bredeweg, T. A.; Baramsai, B.; Couture, A.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Ullmann, J. L.

    2017-09-01

    The absolute neutron-capture cross section of 242Pu was measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. During target fabrication, a small amount of 239Pu was added to the active target so that the absolute scale of the 242Pu(n,γ) cross section could be set according to the known 239Pu(n,f) resonance at En,R = 7.83 eV. The relative scale of the 242Pu(n,γ) cross section covers four orders of magnitude for incident neutron energies from thermal to ≈ 40 keV. The cross section reported in ENDF/B-VII.1 for the 242Pu(n,γ) En,R = 2.68 eV resonance was found to be 2.4% lower than the new absolute 242Pu(n,γ) cross section.

  6. Absolute measurements of fast neutrons using yttrium.

    PubMed

    Roshan, M V; Springham, S V; Rawat, R S; Lee, P; Krishnan, M

    2010-08-01

    Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be f(n) approximately 4.1x10(-4) with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 10(8) neutrons per discharge.

  7. The 235U Prompt Fission Neutron Spectrum in the BR1 Reactor at SCK•CEN

    NASA Astrophysics Data System (ADS)

    Wagemans, Jan; Malambu, Edouard; Borms, Luc; Fiorito, Luca

    2016-02-01

    The BR1 research reactor at SCK•CEN has a spherical cavity in the graphite above the reactor core. In this cavity an accurately characterised Maxwellian thermal neutron field is present. Different converters can be loaded in the cavity in order to obtain other types of neutron (and gamma) irradiation fields. Inside the so-called MARK III converter a fast 235U(n,f) prompt fission neutron field can be obtained. With the support of MCNP calculations, irradiations in MARK III can be directly related to the pure 235U(n,f) prompt fission neutron spectrum. For this purpose MARK III spectrum averaged cross sections for the most relevant fluence dosimetry reactions have been determined. A calibration factor for absolute measurements has been determined applying activation dosimetry following ISO/IEC 17025 standards.

  8. A measurement of the absolute neutron beam polarization produced by an optically pumped 3He neutron spin filter

    NASA Astrophysics Data System (ADS)

    Rich, D. R.; Bowman, J. D.; Crawford, B. E.; Delheij, P. P. J.; Espy, M. A.; Haseyama, T.; Jones, G.; Keith, C. D.; Knudson, J.; Leuschner, M. B.; Masaike, A.; Masuda, Y.; Matsuda, Y.; Penttilä, S. I.; Pomeroy, V. R.; Smith, D. A.; Snow, W. M.; Szymanski, J. J.; Stephenson, S. L.; Thompson, A. K.; Yuan, V.

    2002-04-01

    The capability of performing accurate absolute measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with an absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically pumped polarized 3He spin filter and a relative transmission measurement technique. 3He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method.

  9. Measurements of the absolute neutron fluence spectrum emitted at 0/sup 0/ and 90/sup 0/ from the Little-Boy replica

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roberts, J.H.; Gold, R.; Preston, C.C.

    Nuclear research emulsions (NRE) have been used to characterize the neutron spectrum emitted by the Little-Boy replica. NRE were irradiated at the Little-Boy surface as well as approximately 2m from the center of the Little-Boy replica using polar angles of 0/sup 0/, 30/sup 0/, 60/sup 0/ and 90/sup 0/. For the NRE exposed at 2m, neutron background was determined using shadow shields of borated polyethylene. Emulsion scanning to date has concentrated exclusively on the 2m, 0/sup 0/ and 2m, 90/sup 0/ locations. Approximately 5000 proton-recoil tracks have been measured in NRE irradiated at each of these locations. At the 2m,more » 90/sup 0/ location the NRE neutron spectrum extends from 0.37 up to 8.2 MeV, whereas the NRE neutron spectrum at the 2m, 0/sup 0/ location is much softer and extends only up to 2.7 MeV. NRE neutron spectrometry results at these two locations are compared with both liquid scintillator neutron spectrometry and Monte Carlo calculations. 7 refs., 3 figs.« less

  10. The Absolute Spectrum Polarimeter (ASP)

    NASA Technical Reports Server (NTRS)

    Kogut, A. J.

    2010-01-01

    The Absolute Spectrum Polarimeter (ASP) is an Explorer-class mission to map the absolute intensity and linear polarization of the cosmic microwave background and diffuse astrophysical foregrounds over the full sky from 30 GHz to 5 THz. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r much greater than 1O(raised to the power of { -3}) and Compton distortion y < 10 (raised to the power of{-6}). We describe the ASP instrument and mission architecture needed to detect the signature of an inflationary epoch in the early universe using only 4 semiconductor bolometers.

  11. Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter

    NASA Astrophysics Data System (ADS)

    Musgrave, M. M.; Baeßler, S.; Balascuta, S.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Chupp, T. E.; Cianciolo, V.; Crawford, C.; Craycraft, K.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Grammer, K.; Greene, G. L.; Hamblen, J.; Hayes, C.; Huffman, P.; Jiang, C.; Kucuker, S.; McCrea, M.; Mueller, P. E.; Penttilä, S. I.; Snow, W. M.; Tang, E.; Tang, Z.; Tong, X.; Wilburn, W. S.

    2018-07-01

    Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of ∼ 109 neutrons per second per cm2 and a cross sectional area of 10 × 12 cm2. The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured by neutron transmission through a polarized 3He neutron spin-filter. The pulsed nature of the SNS enabled us to employ an absolute measurement technique for both quantities which does not depend on accurate knowledge of the phase space of the neutron beam or the 3He polarization in the spin filter and is therefore of interest for any experiments on slow neutron beams from pulsed neutron sources which require knowledge of the absolute value of the neutron polarization. The polarization and spin-reversal efficiency measured in this work were done for the NPDGamma experiment, which measures the parity violating γ-ray angular distribution asymmetry with respect to the neutron spin direction in the capture of polarized neutrons on protons. The experimental technique, results, systematic effects, and applications to neutron capture targets are discussed.

  12. Strategy for the absolute neutron emission measurement on ITER.

    PubMed

    Sasao, M; Bertalot, L; Ishikawa, M; Popovichev, S

    2010-10-01

    Accuracy of 10% is demanded to the absolute fusion measurement on ITER. To achieve this accuracy, a functional combination of several types of neutron measurement subsystem, cross calibration among them, and in situ calibration are needed. Neutron transport calculation shows the suitable calibration source is a DT/DD neutron generator of source strength higher than 10(10) n/s (neutron/second) for DT and 10(8) n/s for DD. It will take eight weeks at the minimum with this source to calibrate flux monitors, profile monitors, and the activation system.

  13. On the energy spectrum of cosmogenic neutrons

    NASA Astrophysics Data System (ADS)

    Malgin, A. S.

    2017-11-01

    The processes of the generation of cosmogenic neutrons (cg-neutrons) underground are considered. The neutrons produced by cosmic-ray muons in their interactions with matter are called cosmogenic. Deep-inelastic π A-collisions of pions in muon-induced hadronic showers are mainly their source at energies above 30 MeV. The characteristics of the energy spectrum for the generation of cg-neutrons have been determined by invoking the additive quark model of deep-inelastic soft processes and the mechanism for the interactions of high-energy nucleons in a nucleus. The three-component shape of the spectrum is explained, and the energy of the "knee" in the spectrum has been found to depend on the mass number A. The peculiarities of deep-inelastic π A-scattering lead to the conclusion that the spectrum of cg-neutrons steepens sharply at energies above 1 GeV. The calculated quantitative characteristics of the spectrum are compared with those obtained in measurements.

  14. Neutron spectrum from the little boy mock-up

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Robba, A.A.

    1986-01-01

    Most of the human exposure data used for setting radiation protection guidelines have been obtained by following the survivors of the nuclear explosions at Hiroshima and Nagasaki. Proper evaluation of these data requires estimates of the radiation exposure received by those survivors. Until now neutron dose estimates have relied primarily on calculations as no measurements of the leakage neutron flux or neutron spectrum were available. We have measured the high-energy leakage neutron spectrum from a mock-up of the Little Boy device operating at delayed critical. The measurements are compared with Monte Carlo calculations of the leakage neutron spectrum.

  15. Neutron activation analysis of certified samples by the absolute method

    NASA Astrophysics Data System (ADS)

    Kadem, F.; Belouadah, N.; Idiri, Z.

    2015-07-01

    The nuclear reactions analysis technique is mainly based on the relative method or the use of activation cross sections. In order to validate nuclear data for the calculated cross section evaluated from systematic studies, we used the neutron activation analysis technique (NAA) to determine the various constituent concentrations of certified samples for animal blood, milk and hay. In this analysis, the absolute method is used. The neutron activation technique involves irradiating the sample and subsequently performing a measurement of the activity of the sample. The fundamental equation of the activation connects several physical parameters including the cross section that is essential for the quantitative determination of the different elements composing the sample without resorting to the use of standard sample. Called the absolute method, it allows a measurement as accurate as the relative method. The results obtained by the absolute method showed that the values are as precise as the relative method requiring the use of standard sample for each element to be quantified.

  16. Absolute configuration of a chiral CHD group via neutron diffraction: confirmation of the absolute stereochemistry of the enzymatic formation of malic acid

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bau, R.; Brewer, I.; Chiang, M.Y.

    Neutron diffraction has been used to monitor the absolute stereochemistry of an enzymatic reaction. (-)(2S)malic-3-d acid was prepared by the action of fumarase on fumaric acid in D/sub 2/O. After a large number of cations were screened, it was found that (+)(R)..cap alpha..-phenylethylamine forms the large crystals necessary for a neutron diffraction analysis. The subsequent structure determination showed that (+)(R)..cap alpha..-phenylethylammonium (-)(2S)malate-3-d has an absolute configuration of R at the CHD site. This result confirms the absolute stereochemistry of fumarate-to-malate transformation as catalyzed by the enzyme fumarase.

  17. On the Absolutely Continuous Spectrum of Stark Operators

    NASA Astrophysics Data System (ADS)

    Perelman, Galina

    The stability of the absolutely continuous spectrum of the one-dimensional Stark operator under perturbations of the potential is discussed. The focus is on proving this stability under minimal assumptions on smoothness of the perturbation. A general criterion is presented together with some applications. These include the case of periodic perturbations where we show that any perturbation vL1()∩H-1/2() preserves the a.c. spectrum.

  18. Absolute measurement of the 242Pu neutron-capture cross section

    DOE PAGES

    Buckner, M. Q.; Wu, C. Y.; Henderson, R. A.; ...

    2016-04-21

    Here, the absolute neutron-capture cross section of 242Pu was measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. The first direct measurement of the 242Pu(n,γ) cross section was made over the incident neutron energy range from thermal to ≈ 6 keV, and the absolute scale of the (n,γ) cross section was set according to the known 239Pu(n,f) resonance at E n,R = 7.83 eV. This was accomplished by adding a small quantity of 239Pu to the 242Pu sample. The relative scale of themore » cross section, with a range of four orders of magnitude, was determined for incident neutron energies from thermal to ≈ 40 keV. Our data, in general, are in agreement with previous measurements and those reported in ENDF/B-VII.1; the 242Pu(n,γ) cross section at the E n,R = 2.68 eV resonance is within 2.4% of the evaluated value. However, discrepancies exist at higher energies; our data are ≈30% lower than the evaluated data at E n ≈ 1 keV and are approximately 2σ away from the previous measurement at E n ≈ 20 keV.« less

  19. Effects of silicon cross section and neutron spectrum on the radial uniformity in neutron transmutation doping.

    PubMed

    Kim, Haksung; Ho Pyeon, Cheol; Lim, Jae-Yong; Misawa, Tsuyoshi

    2012-01-01

    The effects of silicon cross section and neutron spectrum on the radial uniformity of a Si-ingot are examined experimentally with various neutron spectrum conditions. For the cross section effect, the numerical results using silicon single crystal cross section reveal good agreements with experiments within relative difference of 6%, whereas the discrepancy is approximately 20% in free-gas cross section. For the neutron spectrum effect, the radial uniformity in hard neutron spectrum is found to be more flattening than that in soft spectrum. Copyright © 2011 Elsevier Ltd. All rights reserved.

  20. Neutron spectrum determination in a sub-critical assembly using the multi-disc neutron activation technique

    NASA Astrophysics Data System (ADS)

    Koseoglou, P.; Vagena, E.; Stoulos, S.; Manolopoulou, M.

    2016-09-01

    Neutron spectrum of the sub-critical nuclear assembly-reactor of Aristotle University of Thessaloniki was measured at three radial distances from the reactor core. The neutron activation technique was applied irradiating 15 thick foils - disc of various elements at each position. The data of 38 (n, γ), (n, p) and (n, α) reactions were analyzed for specific activity determination. Discs instead of foils were used due to the relevant low neutron flux, so the gamma self-absorption as well as the neutron self-shielding factors has been calculated using GEANT simulations in order to determine the activity induced. The specific activities calculated for all isotopes studied were the input to the SANDII code, which was built specifically for the neutron spectrum de-convolution when the neutron activation technique is used. For the optimization of the results a technique was applied in order to minimize the influence of the initial-"guessed" spectrum shape SANDII uses. The neutron spectrum estimated presents a peak in the regions of (i) thermal neutrons ranged between 0.001 and 1 eV peaking at neutron energy ∼0.1 eV and (ii) fast neutrons ranged between 0.1 and 20 MeV peaking at neutron energy ∼1.2 MeV. The reduction of thermal neutrons is higher than the fast one as the distance from the reactor core increases since thermal neutrons capture by natural U-fuel has higher cross section than the fast neutrons.

  1. Hardening neutron spectrum for advanced actinide transmutation experiments in the ATR.

    PubMed

    Chang, G S; Ambrosek, R G

    2005-01-01

    The most effective method for transmuting long-lived isotopes contained in spent nuclear fuel into shorter-lived fission products is in a fast neutron spectrum reactor. In the absence of a fast test reactor in the United States, initial irradiation testing of candidate fuels can be performed in a thermal test reactor that has been modified to produce a test region with a hardened neutron spectrum. Such a test facility, with a spectrum similar but somewhat softer than that of the liquid-metal fast breeder reactor (LMFBR), has been constructed in the INEEL's Advanced Test Reactor (ATR). The radial fission power distribution of the actinide fuel pin, which is an important parameter in fission gas release modelling, needs to be accurately predicted and the hardened neutron spectrum in the ATR and the LMFBR fast neutron spectrum is compared. The comparison analyses in this study are performed using MCWO, a well-developed tool that couples the Monte Carlo transport code MCNP with the isotope depletion and build-up code ORIGEN-2. MCWO analysis yields time-dependent and neutron-spectrum-dependent minor actinide and Pu concentrations and detailed radial fission power profile calculations for a typical fast reactor (LMFBR) neutron spectrum and the hardened neutron spectrum test region in the ATR. The MCWO-calculated results indicate that the cadmium basket used in the advanced fuel test assembly in the ATR can effectively depress the linear heat generation rate in the experimental fuels and harden the neutron spectrum in the test region.

  2. Diagnostic Application of Absolute Neutron Activation Analysis in Hematology

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    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.

  3. Use of the WNR spallation neutron source at LAMPF to determine the absolute efficiency of a neutron scintillation detector

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Staples, P.A.; Egan, J.J.; Kegel, G.H.R.

    1994-06-01

    Prompt fission neutron spectrum measurements at the University of Massachusetts Lowell 5.5 MV Van de Graaff accelerator laboratory require that the neutron detector efficiency be well known over a neutron energy range of 100 keV to 20 MeV. The efficiency of the detector, has been determined for energies greater than 5.0 MeV using the Weapons Neutron Research (WNR) white neutron source at the Los Alamos Meson Physics Facility (LAMPF) in a pulsed beam, time-of-flight (TOF) experiment. Carbon matched polyethylene and graphite scatterers were used to obtain a hydrogen spectrum. The detector efficiency was determined using the well known H(n,n) scatteringmore » cross section. Results are compared to the detector efficiency calculation program SCINFUL available from the Radiation Shielding Information Center at Oak Ridge National Laboratory.« less

  4. How to Produce a Reactor Neutron Spectrum Using a Proton Accelerator

    DOE PAGES

    Burns, Kimberly A.; Wootan, David W.; Gates, Robert O.; ...

    2015-06-18

    A method for reproducing the neutron energy spectrum present in the core of an operating nuclear reactor using an engineered target in an accelerator proton beam is proposed. The protons interact with a target to create neutrons through various (p,n) type reactions. Spectral tailoring of the emitted neutrons can be used to modify the energy of the generated neutron spectrum to represent various reactor spectra. Through the use of moderators and reflectors, the neutron spectrum can be modified to reproduce many different spectra of interest including spectra in small thermal test reactors, large pressurized water reactors, and fast reactors. Themore » particular application of this methodology is the design of an experimental approach for using an accelerator to measure the betas produced during fission to be used to reduce uncertainties in the interpretation of reactor antineutrino measurements. This approach involves using a proton accelerator to produce a neutron field representative of a power reactor, and using this neutron field to irradiate fission foils of the primary isotopes contributing to fission in the reactor, creating unstable, neutron rich fission products that subsequently beta decay and emit electron antineutrinos. A major advantage of an accelerator neutron source over a neutron beam from a thermal reactor is that the fast neutrons can be slowed down or tailored to approximate various power reactor spectra. An accelerator based neutron source that can be tailored to match various reactor neutron spectra provides an advantage for control in studying how changes in the neutron spectra affect parameters such as the resulting fission product beta spectrum.« less

  5. Absolute determination of copper and silver in ancient coins using 14 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Chalouhi, Ch.; Hourani, E.; Loos, R.; Melki, S.

    1982-09-01

    A method for absolute determination of copper and silver in ancient coins is described. Activation analysis by 14 MeV neutrons is performed. In the experimental procedure emphasis is placed on corrections for neutrons and gamma attenuation. In the analytical procedure, a multi linear-regression calculation is used to separate different contributions to the 511 keV gamma peak. The precision in the absolute determination of Cu and Ag is better than 2% in recent coins of definite shapes, whereas it is a somewhat lower in ancient coins of irregular shapes. The method was applied to ancient coins provided by the Museum of the American University of Beirut. Overall consistency and suitability of the method were obtained.

  6. Characterization of the Energy Spectrum at the Indiana University Neutron Source

    DTIC Science & Technology

    2011-03-01

    CHARACTERIZATION OF THE ENERGY SPECTRUM AT THE INDIANA UNIVERSITY NREP NEUTRON SOURCE THESIS Matthew R. Halstead, Civilian AFIT/GNE/ENP/11-M08...subject to copyright protection in the United States. AFIT/GNE/ENP/11-M08 CHARACTERIZATION OF THE ENERGY SPECTRUM AT THE INDIANA UNIVERSITY NREP NEUTRON...The neutron source at the Indiana University Cyclotron Facility produces neu- trons via proton bombardment of a natural beryllium (100% 9Be) target

  7. Analysis of neutron spectrum effects on primary damage in tritium breeding blankets

    NASA Astrophysics Data System (ADS)

    Choi, Yong Hee; Joo, Han Gyu

    2012-07-01

    The effect of neutron spectrum on primary damages in a structural material of a tritium breeding blanket is investigated with a newly established recoil spectrum estimation system. First, a recoil spectrum generation code is developed to obtain the energy spectrum of primary knock-on atoms (PKAs) for a given neutron spectrum utilizing the latest ENDF/B data. Secondly, a method for approximating the high energy tail of the recoil spectrum is introduced to avoid expensive molecular dynamics calculations for high energy PKAs using the concept of recoil energy of the secondary knock-on atoms originated by the INtegration of CAScades (INCAS) model. Thirdly, the modified spectrum is combined with a set of molecular dynamics calculation results to estimate the primary damage parameters such as the number of surviving point defects. Finally, the neutron spectrum is varied by changing the material of the spectral shifter and the result in primary damage parameters is examined.

  8. Neutron skyshine from intense 14-MeV neutron source facility

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakamura, T.; Hayashi, K.; Takahashi, A.

    1985-07-01

    The dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured with the high-efficiency rem counter, the multisphere spectrometer, and the NE-213 scintillator in the environment surrounding an intense 14-MeV neutron source facility. The dose distribution and the energy spectra of neutrons around the facility used as a skyshine source have also been measured to enable the absolute evaluation of the skyshine effect. The skyshine effect was analyzed by two multigroup Monte Carlo codes, NIMSAC and MMCR-2, by two discrete ordinates S /sub n/ codes, ANISN and DOT3.5, and by the shield structure designmore » code for skyshine, SKYSHINE-II. The calculated results show good agreement with the measured results in absolute values. These experimental results should be useful as benchmark data for shyshine analysis and for shielding design of fusion facilities.« less

  9. Corrections on energy spectrum and scatterings for fast neutron radiography at NECTAR facility

    NASA Astrophysics Data System (ADS)

    Liu, Shu-Quan; Bücherl, Thomas; Li, Hang; Zou, Yu-Bin; Lu, Yuan-Rong; Guo, Zhi-Yu

    2013-11-01

    Distortions caused by the neutron spectrum and scattered neutrons are major problems in fast neutron radiography and should be considered for improving the image quality. This paper puts emphasis on the removal of these image distortions and deviations for fast neutron radiography performed at the NECTAR facility of the research reactor FRM- II in Technische Universität München (TUM), Germany. The NECTAR energy spectrum is analyzed and established to modify the influence caused by the neutron spectrum, and the Point Scattered Function (PScF) simulated by the Monte-Carlo program MCNPX is used to evaluate scattering effects from the object and improve image quality. Good analysis results prove the sound effects of the above two corrections.

  10. Broad Energy Range Neutron Spectroscopy using a Liquid Scintillator and a Proportional Counter: Application to a Neutron Spectrum Similar to that from an Improvised Nuclear Device.

    PubMed

    Xu, Yanping; Randers-Pehrson, Gerhard; Marino, Stephen A; Garty, Guy; Harken, Andrew; Brenner, David J

    2015-09-11

    A novel neutron irradiation facility at the Radiological Research Accelerator Facility (RARAF) has been developed to mimic the neutron radiation from an Improvised Nuclear Device (IND) at relevant distances (e.g. 1.5 km) from the epicenter. The neutron spectrum of this IND-like neutron irradiator was designed according to estimations of the Hiroshima neutron spectrum at 1.5 km. It is significantly different from a standard reactor fission spectrum, because the spectrum changes as the neutrons are transported through air, and it is dominated by neutron energies from 100 keV up to 9 MeV. To verify such wide energy range neutron spectrum, detailed here is the development of a combined spectroscopy system. Both a liquid scintillator detector and a gas proportional counter were used for the recoil spectra measurements, with the individual response functions estimated from a series of Monte Carlo simulations. These normalized individual response functions were formed into a single response matrix for the unfolding process. Several accelerator-based quasi-monoenergetic neutron source spectra were measured and unfolded to test this spectroscopy system. These reference neutrons were produced from two reactions: T(p,n) 3 He and D(d,n) 3 He, generating neutron energies in the range between 0.2 and 8 MeV. The unfolded quasi-monoenergetic neutron spectra indicated that the detection system can provide good neutron spectroscopy results in this energy range. A broad-energy neutron spectrum from the 9 Be(d,n) reaction using a 5 MeV deuteron beam, measured at 60 degrees to the incident beam was measured and unfolded with the evaluated response matrix. The unfolded broad neutron spectrum is comparable with published time-of-flight results. Finally, the pair of detectors were used to measure the neutron spectrum generated at the RARAF IND-like neutron facility and a comparison is made to the neutron spectrum of Hiroshima.

  11. Calculations of Nuclear Astrophysics and Californium Fission Neutron Spectrum Averaged Cross Section Uncertainties Using ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0 and Low-fidelity Covariances

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pritychenko, B., E-mail: pritychenko@bnl.gov

    Nuclear astrophysics and californium fission neutron spectrum averaged cross sections and their uncertainties for ENDF materials have been calculated. Absolute values were deduced with Maxwellian and Mannhart spectra, while uncertainties are based on ENDF/B-VII.1, JEFF-3.1.2, JENDL-4.0 and Low-Fidelity covariances. These quantities are compared with available data, independent benchmarks, EXFOR library, and analyzed for a wide range of cases. Recommendations for neutron cross section covariances are given and implications are discussed.

  12. Broad Energy Range Neutron Spectroscopy using a Liquid Scintillator and a Proportional Counter: Application to a Neutron Spectrum Similar to that from an Improvised Nuclear Device

    PubMed Central

    Randers-Pehrson, Gerhard; Marino, Stephen A.; Garty, Guy; Harken, Andrew; Brenner, David J.

    2015-01-01

    A novel neutron irradiation facility at the Radiological Research Accelerator Facility (RARAF) has been developed to mimic the neutron radiation from an Improvised Nuclear Device (IND) at relevant distances (e.g. 1.5 km) from the epicenter. The neutron spectrum of this IND-like neutron irradiator was designed according to estimations of the Hiroshima neutron spectrum at 1.5 km. It is significantly different from a standard reactor fission spectrum, because the spectrum changes as the neutrons are transported through air, and it is dominated by neutron energies from 100 keV up to 9 MeV. To verify such wide energy range neutron spectrum, detailed here is the development of a combined spectroscopy system. Both a liquid scintillator detector and a gas proportional counter were used for the recoil spectra measurements, with the individual response functions estimated from a series of Monte Carlo simulations. These normalized individual response functions were formed into a single response matrix for the unfolding process. Several accelerator-based quasi-monoenergetic neutron source spectra were measured and unfolded to test this spectroscopy system. These reference neutrons were produced from two reactions: T(p,n)3He and D(d,n)3He, generating neutron energies in the range between 0.2 and 8 MeV. The unfolded quasi-monoenergetic neutron spectra indicated that the detection system can provide good neutron spectroscopy results in this energy range. A broad-energy neutron spectrum from the 9Be(d,n) reaction using a 5 MeV deuteron beam, measured at 60 degrees to the incident beam was measured and unfolded with the evaluated response matrix. The unfolded broad neutron spectrum is comparable with published time-of-flight results. Finally, the pair of detectors were used to measure the neutron spectrum generated at the RARAF IND-like neutron facility and a comparison is made to the neutron spectrum of Hiroshima. PMID:26273118

  13. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    DOE PAGES

    Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki; ...

    2016-07-02

    We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 10 25 n/m 2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructuremore » changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10 25 n/m 2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10 25 n/m 2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

  14. Neutron energy spectrum influence on irradiation hardening and microstructural development of tungsten

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fukuda, Makoto; Kiran Kumar, N. A. P.; Koyanagi, Takaaki

    We performed a neutron irradiation to single crystal pure tungsten in the mixed spectrum High Flux Isotope Reactor (HFIR). In order to investigate the influences of neutron energy spectrum, the microstructure and irradiation hardening were compared with previous data obtained from the irradiation campaigns in the mixed spectrum Japan Material Testing Reactor (JMTR) and the sodium-cooled fast reactor Joyo. The irradiation temperatures were in the range of ~90–~800 °C and fast neutron fluences were 0.02–9.00 × 10 25 n/m 2 (E > 0.1 MeV). Post irradiation evaluation included Vickers hardness measurements and transmission electron microscopy. Moreover, the hardness and microstructuremore » changes exhibited a clear dependence on the neutron energy spectrum. The hardness appeared to increase with increasing thermal neutron flux when fast fluence exceeds 1 × 10 25 n/m 2 (E > 0.1 MeV). Finally, irradiation induced precipitates considered to be χ- and σ-phases were observed in samples irradiated to >1 × 10 25 n/m 2 (E > 0.1 MeV), which were pronounced at high dose and due to the very high thermal neutron flux of HFIR. Although the irradiation hardening mainly caused by defects clusters in a low dose regime, the transmutation-induced precipitation appeared to impose additional significant hardening of the tungsten.« less

  15. Little Boy neutron spectrum below 3 MeV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

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

    The leakage neutron spectrum from the Little Boy replica has been measured from 12 keV to 3 MeV using a high-resolution /sup 3/He ionization chamber, and from 1 keV to 3 MeV using proton-recoil proportional counters. The /sup 3/He-spectrometer measurements were made at distances of 0.75 and 2.0 m from the active center and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly. Proton-recoil measurments were made at 90/sup 0/ to the assembly axis at distances of 0.75 and 2.0 m, with a shielded measurement made at 2.0 m to estimatemore » background due to scattering. The /sup 3/He spectrometer was calibrated at Los Alamos using monoenergetic /sup 7/Li(p,n)/sup 7/Be neutrons to generate a family of response functions. The proton-recoil counters were calibrated at Argonne by studying the capture of thermal neutrons by nitrogen in the counters, by observation of the 24-keV neutron resonance in iron, and by relating to the known hydrogen content of the counters. The neutron spectrum from Little Boy was found to be highly structured, with peaks corresponding to minima in the iron total neutron cross section. In particular, influence of the 24-keV iron window was evident in both sets of spectra. The measurements provide information for dosimetry calculations and also a valuable intercomparison of neutron spectrometry using the two different detector types. Spectra measured with both detectors are in essential agreement. 8 references, 7 figures, 2 tables.« less

  16. Measurement of prompt fission neutron spectrum for spontaneous fission of 252Cf using γ multiplicity tagging

    NASA Astrophysics Data System (ADS)

    Blain, E.; Daskalakis, A.; Block, R. C.; Danon, Y.

    2017-06-01

    The prompt fission neutron spectrum from spontaneous fission of 252Cf is an integral part of several aspects of nuclear data. Not only is the spectrum itself of interest, but neutron detectors often use the spectrum for calibration, and other prompt fission neutron spectra are measured as a ratio to 252Cf. Therefore, reducing the uncertainties in this spectrum will allow for more accurate nuclear data to be available across a wide range of fields. The prompt fission neutron spectrum for the spontaneous fission of 252Cf was measured at Rensselaer Polytechnic Institute using the multiple γ tagging method with a 18.4-ng fission sample. An EJ-301 liquid scintillator fast neutron detector was used to measure the high energy portion of the spectrum, 0.5-7 MeV, and a thin EJ-204 plastic scintillator was used to measure the low energy portion of the spectrum, from 50 keV to 2 MeV. These spectra both show good agreement with the current evaluation of 252Cf and have low associated uncertainties providing a new high precision measurement that helps reduce the uncertainties in the prompt fission neutron spectrum for the spontaneous fission of 252Cf.

  17. Refinements in the Los Alamos model of the prompt fission neutron spectrum

    DOE PAGES

    Madland, D. G.; Kahler, A. C.

    2017-01-01

    This paper presents a number of refinements to the original Los Alamos model of the prompt fission neutron spectrum and average prompt neutron multiplicity as derived in 1982. The four refinements are due to new measurements of the spectrum and related fission observables many of which were not available in 1982. Here, they are also due to a number of detailed studies and comparisons of the model with previous and present experimental results including not only the differential spectrum, but also integal cross sections measured in the field of the differential spectrum. The four refinements are (a) separate neutron contributionsmore » in binary fission, (b) departure from statistical equilibrium at scission, (c) fission-fragment nuclear level-density models, and (d) center-of-mass anisotropy. With these refinements, for the first time, good agreement has been obtained for both differential and integral measurements using the same Los Alamos model spectrum.« less

  18. On similarity of various reactor spectra and 235U prompt fission neutron spectrum.

    PubMed

    Košťál, Michal; Matěj, Zdeněk; Losa, Evžen; Huml, Ondřej; Štefánik, Milan; Cvachovec, František; Schulc, Martin; Jánský, Bohumil; Novák, Evžen; Harutyunyan, Davit; Rypar, Vojtěch

    2018-05-01

    A well-defined neutron spectrum is an essential tool not only for calibration and testing of neutron detectors used in dosimetry and spectroscopy but also for validation and verification of evaluated cross sections. A new evaluation of thermal-neutron induced 235 U PFNS was performed by the International Atomic Energy Agency (IAEA) in the CIELO (Collaborative International Evaluated Library Organisation Project) project; new measurements of Spectral Averaged Cross sections averaged in the evaluated spectrum are to be obtained. In general, a neutron spectrum in the core is not identical to the pure fission one because fission neutrons undergo many scattering reactions, but it can be shown that PFNS and reactor spectra become undistinguishable from a certain energy boundary. This limit is important for experiments, because when the studied reaction threshold is over this limit, the spectral averaged cross sections in PFNS can be derived from the measured reactions in the reactor core. The evaluation of the neutron spectrum measurements in three different thermal-reactor cores shows that this lower limit is around the energy of 5.5 - 6 MeV. Above this energy the reactor spectra becomes identical with the 235 U PFNS. IAEA CIELO PFNS is within 5% of the measured PFNS from 10 to 14 MeV in a LR-0 reactor, while ENDF/B-VII evaluated PFNS underestimated measured neutron spectra. Copyright © 2018 Elsevier Ltd. All rights reserved.

  19. Thick-foils activation technique for neutron spectrum unfolding with the MINUIT routine-Comparison with GEANT4 simulations

    NASA Astrophysics Data System (ADS)

    Vagena, E.; Theodorou, K.; Stoulos, S.

    2018-04-01

    Neutron activation technique has been applied using a proposed set of twelve thick metal foils (Au, As, Cd, In, Ir, Er, Mn, Ni, Se, Sm, W, Zn) for off-site measurements to obtain the neutron spectrum over a wide energy range (from thermal up to a few MeV) in intense neutron-gamma mixed fields such as around medical Linacs. The unfolding procedure takes into account the activation rates measured using thirteen (n , γ) and two (n , p) reactions without imposing a guess solution-spectrum. The MINUIT minimization routine unfolds a neutron spectrum that is dominated by fast neutrons (70%) peaking at 0.3 MeV, while the thermal peak corresponds to the 15% of the total neutron fluence equal to the epithermal-resonances area. The comparison of the unfolded neutron spectrum against the simulated one with the GEANT4 Monte-Carlo code shows a reasonable agreement within the measurement uncertainties. Therefore, the proposed set of activation thick-foils could be a useful tool in order to determine low flux neutrons spectrum in intense mixed field.

  20. Little Boy neutron spectrum below 1 MeV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Evans, A.E.

    1984-01-01

    A high-resolution /sup 3/He ionization chamber of the type development by Cuttler and Shalev was used to study the neutron spectrum from the Little Boy mockup. Measurements were made at distances of 0.75 and 2.0 m and at angles of 0/sup 0/, 45/sup 0/, and 90/sup 0/ with respect to the axis of the assembly, which was operated at power levels from 8.6 to 450 mW. Detector efficiency as a function of energy as well as parameters for correction of pulse-height distributions for proton-recoil and wall effects were determined from a set of response functions for monoenergetic neutrons measured atmore » the Los Alamos 3.75-MeV Van de Graaff Accelerator Facility. Pulse-shape discrimination was used to separate /sup 3/He-recoil pulses from the pulse-height distribution. The spectrum was found to be highly structured, with peaks corresponding to minima in the total neutron cross section of iron. In particular, 15% of the neutrons above the epithermal peak in energy were found to be in the 24-keV iron window. Lesser peaks out to 700 keV are also attributable to filtering action of the weapon's heavy iron casing. Data taken using experimental proton-recoil proportional counters are compared with the high-resolution spectra.« less

  1. Evaluation of the Benjamin type proportional counter for absolute neutron spectrometry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Taeb, M.

    1985-01-01

    This evaluation has shown that the major sources of uncertainty in experimental measurements with a Benjamin detector are: (1) detector pressure, (2) hydrogen gas purity, (3) detector calibration, and (4) operating voltage. To test these operational parameters, neutron spectra were measured at the University of Missouri Research Reactor (MURR) for silicon, scandium, iron, and bismuth filtered beams and angular penetration data through an 20.3 cm water slab. Results were then critically compared with theoretical calculations and with data from other spectrometer systems in regions of energy overlap. Neutron spectra having relatively small contributions from neutrons with energies higher than themore » energy range of the Benjamin spectrometer (at a specific pressure) generally exhibit excellent results. This is particularly true for the silicon filter (which produces two quasi-monoenergetic peaks at 55 keV and 144 keV) and the scandium filter (which creates a spectrum which decreases with increasing energy). For those spectra exhibiting relatively larger high energy neutron components, the results are less satisfying.« less

  2. A note on the revised galactic neutron spectrum of the Ames collaborative study

    NASA Technical Reports Server (NTRS)

    Schaefer, H. J.

    1980-01-01

    Energy distributions of the neutron dose equivalents in the 0.1 to 300 Mev interval for the Ames and Hess spectra are compared. The Ames spectrum shows no evaporation peak, moves the bulk of the flux away from the region of elastic collision and spreads it more evenly over higher energies. The neutron spectrum in space does not seem to hear out the Ames model. Emulsion findings on all manned missions of the past consistently indicate that evaporation events are a prolific source of neutrons in space.

  3. Precision determination of absolute neutron flux

    DOE PAGES

    Yue, A. T.; Anderson, E. S.; Dewey, M. S.; ...

    2018-06-08

    A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

  4. Precision determination of absolute neutron flux

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Yue, A. T.; Anderson, E. S.; Dewey, M. S.

    A technique for establishing the total neutron rate of a highly-collimated monochromatic cold neutron beam was demonstrated using an alpha–gamma counter. The method involves only the counting of measured rates and is independent of neutron cross sections, decay chain branching ratios, and neutron beam energy. For the measurement, a target of 10B-enriched boron carbide totally absorbed the neutrons in a monochromatic beam, and the rate of absorbed neutrons was determined by counting 478 keV gamma rays from neutron capture on 10B with calibrated high-purity germanium detectors. A second measurement based on Bragg diffraction from a perfect silicon crystal was performedmore » to determine the mean de Broglie wavelength of the beam to a precision of 0.024%. With these measurements, the detection efficiency of a neutron monitor based on neutron absorption on 6Li was determined to an overall uncertainty of 0.058%. We discuss the principle of the alpha–gamma method and present details of how the measurement was performed including the systematic effects. We further describe how this method may be used for applications in neutron dosimetry and metrology, fundamental neutron physics, and neutron cross section measurements.« less

  5. Estimation of neutron spectrum in the low-level gamma spectroscopy system using unfolding procedure

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Knežević, D., E-mail: david.knezevic@df.uns.ac.rs; Jovančević, N.; Krmar, M.

    2016-03-25

    The radiation resulting from neutron interactions with Ge nuclei in active volume of HPGe detectors is one of the main concerns in low-level gamma spectroscopy measurements [1,2]. It is usually not possible to measure directly spectrum of neutrons which strike detector. This paper explore the possibility of estimation of neutron spectrum using measured activities of certain Ge(n,γ) and Ge(n,n’) reactions (obtained from low-level gamma measurements), available ENDF cross section data and unfolding procedures. In this work HPGe detector with passive shield made from commercial low background lead was used for the measurement. The most important objective of this study wasmore » to reconstruct muon induced neutron spectrum created in the shield of the HPGe detector. MAXED [3] and GRAVEL [4] algorithms for neutron spectra unfolding were used. The results of those two algorithms were compared and we analyzed the sensitivity of the unfolding procedure to the various input parameters.« less

  6. Modeling the Complete Gravitational Wave Spectrum of Neutron Star Mergers.

    PubMed

    Bernuzzi, Sebastiano; Dietrich, Tim; Nagar, Alessandro

    2015-08-28

    In the context of neutron star mergers, we study the gravitational wave spectrum of the merger remnant using numerical relativity simulations. Postmerger spectra are characterized by a main peak frequency f2 related to the particular structure and dynamics of the remnant hot hypermassive neutron star. We show that f(2) is correlated with the tidal coupling constant κ(2)^T that characterizes the binary tidal interactions during the late-inspiral merger. The relation f(2)(κ(2)^T) depends very weakly on the binary total mass, mass ratio, equation of state, and thermal effects. This observation opens up the possibility of developing a model of the gravitational spectrum of every merger unifying the late-inspiral and postmerger descriptions.

  7. Absolute calibration of neutron detectors on the C-2U advanced beam-driven FRC.

    PubMed

    Magee, R M; Clary, R; Korepanov, S; Jauregui, F; Allfrey, I; Garate, E; Valentine, T; Smirnov, A

    2016-11-01

    In the C-2U fusion energy experiment, high power neutral beam injection creates a large fast ion population that sustains a field-reversed configuration (FRC) plasma. The diagnosis of the fast ion pressure in these high-performance plasmas is therefore critical, and the measurement of the flux of neutrons from the deuterium-deuterium (D-D) fusion reaction is well suited to the task. Here we describe the absolute, in situ calibration of scintillation neutron detectors via two independent methods: firing deuterium beams into a high density gas target and calibration with a 2 × 10 7 n/s AmBe source. The practical issues of each method are discussed and the resulting calibration factors are shown to be in good agreement. Finally, the calibration factor is applied to C-2U experimental data where the measured neutron rate is found to exceed the classical expectation.

  8. Evaluating the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.

    In this work the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetrymore » with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures

  9. Evaluating the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks

    NASA Astrophysics Data System (ADS)

    Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.

    2013-07-01

    In this work the performance of two neutron spectrum unfolding codes based on iterative procedures and artificial neural networks is evaluated. The first one code based on traditional iterative procedures and called Neutron spectrometry and dosimetry from the Universidad Autonoma de Zacatecas (NSDUAZ) use the SPUNIT iterative algorithm and was designed to unfold neutron spectrum and calculate 15 dosimetric quantities and 7 IAEA survey meters. The main feature of this code is the automated selection of the initial guess spectrum trough a compendium of neutron spectrum compiled by the IAEA. The second one code known as Neutron spectrometry and dosimetry with artificial neural networks (NDSann) is a code designed using neural nets technology. The artificial intelligence approach of neural net does not solve mathematical equations. By using the knowledge stored at synaptic weights on a neural net properly trained, the code is capable to unfold neutron spectrum and to simultaneously calculate 15 dosimetric quantities, needing as entrance data, only the rate counts measured with a Bonner spheres system. Similarities of both NSDUAZ and NSDann codes are: they follow the same easy and intuitive user's philosophy and were designed in a graphical interface under the LabVIEW programming environment. Both codes unfold the neutron spectrum expressed in 60 energy bins, calculate 15 dosimetric quantities and generate a full report in HTML format. Differences of these codes are: NSDUAZ code was designed using classical iterative approaches and needs an initial guess spectrum in order to initiate the iterative procedure. In NSDUAZ, a programming routine was designed to calculate 7 IAEA instrument survey meters using the fluence-dose conversion coefficients. NSDann code use artificial neural networks for solving the ill-conditioned equation system of neutron spectrometry problem through synaptic weights of a properly trained neural network. Contrary to iterative procedures, in neural

  10. Evaluating the 239Pu prompt fission neutron spectrum induced by thermal to 30 MeV neutrons

    DOE PAGES

    Neudecker, Denise; Talou, Patrick; Kawano, Toshihiko; ...

    2016-03-15

    We present a new evaluation of the 239Pu prompt fission neutron spectrum (PFNS) induced by thermal to 30 MeV neutrons. Compared to the ENDF/B-VII.1 evaluation, this one includes recently published experimental data as well as an improved and extended model description to predict PFNS. For instance, the pre-equilibrium neutron emission component to the PFNS is considered and the incident energy dependence of model parameters is parametrized more realistically. Experimental and model parameter uncertainties and covariances are estimated in detail. Also, evaluated covariances are provided between all PFNS at different incident neutron energies. In conclusion, selected evaluation results and first benchmarkmore » calculations using this evaluation are briefly discussed.« less

  11. A novel neutron energy spectrum unfolding code using particle swarm optimization

    NASA Astrophysics Data System (ADS)

    Shahabinejad, H.; Sohrabpour, M.

    2017-07-01

    A novel neutron Spectrum Deconvolution using Particle Swarm Optimization (SDPSO) code has been developed to unfold the neutron spectrum from a pulse height distribution and a response matrix. The Particle Swarm Optimization (PSO) imitates the bird flocks social behavior to solve complex optimization problems. The results of the SDPSO code have been compared with those of the standard spectra and recently published Two-steps Genetic Algorithm Spectrum Unfolding (TGASU) code. The TGASU code have been previously compared with the other codes such as MAXED, GRAVEL, FERDOR and GAMCD and shown to be more accurate than the previous codes. The results of the SDPSO code have been demonstrated to match well with those of the TGASU code for both under determined and over-determined problems. In addition the SDPSO has been shown to be nearly two times faster than the TGASU code.

  12. A neutron spectrum unfolding computer code based on artificial neural networks

    NASA Astrophysics Data System (ADS)

    Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.

    2014-02-01

    The Bonner Spheres Spectrometer consists of a thermal neutron sensor placed at the center of a number of moderating polyethylene spheres of different diameters. From the measured readings, information can be derived about the spectrum of the neutron field where measurements were made. Disadvantages of the Bonner system are the weight associated with each sphere and the need to sequentially irradiate the spheres, requiring long exposure periods. Provided a well-established response matrix and adequate irradiation conditions, the most delicate part of neutron spectrometry, is the unfolding process. The derivation of the spectral information is not simple because the unknown is not given directly as a result of the measurements. The drawbacks associated with traditional unfolding procedures have motivated the need of complementary approaches. Novel methods based on Artificial Intelligence, mainly Artificial Neural Networks, have been widely investigated. In this work, a neutron spectrum unfolding code based on neural nets technology is presented. This code is called Neutron Spectrometry and Dosimetry with Artificial Neural networks unfolding code that was designed in a graphical interface. The core of the code is an embedded neural network architecture previously optimized using the robust design of artificial neural networks methodology. The main features of the code are: easy to use, friendly and intuitive to the user. This code was designed for a Bonner Sphere System based on a 6LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. The main feature of the code is that as entrance data, for unfolding the neutron spectrum, only seven rate counts measured with seven Bonner spheres are required; simultaneously the code calculates 15 dosimetric quantities as well as the total flux for radiation protection purposes. This code generates a full report with all information of the unfolding in

  13. The Gamow-state description of the decay energy spectrum of neutron-unbound 25O

    NASA Astrophysics Data System (ADS)

    Id Betan, R. M.; de la Madrid, R.

    2018-02-01

    We show the feasibility of calculating the decay energy spectrum of neutron emitting nuclei within the Gamow-state description of resonances by obtaining the decay energy spectrum of 25O. We model this nucleus as a valence neutron interacting with an 24O inert core, and we obtain the resulting resonant energies, widths and decay energy spectra for the ground and first excited states. We also discuss the similarities and differences between the decay energy spectrum of a Gamow state and the Breit-Wigner distribution with energy-dependent width.

  14. Stabilization of Particle Discrimination Efficiencies for Neutron Spectrum Unfolding With Organic Scintillators

    NASA Astrophysics Data System (ADS)

    Lawrence, Chris C.; Polack, J. K.; Febbraro, Michael; Kolata, J. J.; Flaska, Marek; Pozzi, S. A.; Becchetti, F. D.

    2017-02-01

    The literature discussing pulse-shape discrimination (PSD) in organic scintillators dates back several decades. However, little has been written about PSD techniques that are optimized for neutron spectrum unfolding. Variation in n-γ misclassification rates and in γ/n ratio of incident fields can distort the neutron pulse-height response of scintillators and these distortions can in turn cause large errors in unfolded spectra. New applications in arms-control verification call for detection of lower-energy neutrons, for which PSD is particularly problematic. In this article, we propose techniques for removing distortions on pulse-height response that result from the merging of PSD distributions in the low-pulse-height region. These techniques take advantage of the repeatable shapes of PSD distributions that are governed by the counting statistics of scintillation-photon populations. We validate the proposed techniques using accelerator-based time-of-flight measurements and then demonstrate them by unfolding the Watt spectrum from measurement with a 252Cf neutron source.

  15. Absolute calibration of neutron detectors on the C-2U advanced beam-driven FRC

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Magee, R. M., E-mail: rmagee@trialphaenergy.com; Clary, R.; Korepanov, S.

    2016-11-15

    In the C-2U fusion energy experiment, high power neutral beam injection creates a large fast ion population that sustains a field-reversed configuration (FRC) plasma. The diagnosis of the fast ion pressure in these high-performance plasmas is therefore critical, and the measurement of the flux of neutrons from the deuterium-deuterium (D-D) fusion reaction is well suited to the task. Here we describe the absolute, in situ calibration of scintillation neutron detectors via two independent methods: firing deuterium beams into a high density gas target and calibration with a 2 × 10{sup 7} n/s AmBe source. The practical issues of each methodmore » are discussed and the resulting calibration factors are shown to be in good agreement. Finally, the calibration factor is applied to C-2U experimental data where the measured neutron rate is found to exceed the classical expectation.« less

  16. Characterization of a deuterium-deuterium plasma fusion neutron generator

    NASA Astrophysics Data System (ADS)

    Lang, R. F.; Pienaar, J.; Hogenbirk, E.; Masson, D.; Nolte, R.; Zimbal, A.; Röttger, S.; Benabderrahmane, M. L.; Bruno, G.

    2018-01-01

    We characterize the neutron output of a deuterium-deuterium plasma fusion neutron generator, model 35-DD-W-S, manufactured by NSD/Gradel-Fusion. The measured energy spectrum is found to be dominated by neutron peaks at 2.2 MeV and 2.7 MeV. A detailed GEANT4 simulation accurately reproduces the measured energy spectrum and confirms our understanding of the fusion process in this generator. Additionally, a contribution of 14 . 1 MeV neutrons from deuterium-tritium fusion is found at a level of 3 . 5%, from tritium produced in previous deuterium-deuterium reactions. We have measured both the absolute neutron flux as well as its relative variation on the operational parameters of the generator. We find the flux to be proportional to voltage V 3 . 32 ± 0 . 14 and current I 0 . 97 ± 0 . 01. Further, we have measured the angular dependence of the neutron emission with respect to the polar angle. We conclude that it is well described by isotropic production of neutrons within the cathode field cage.

  17. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: measurement with an extended-range Bonner sphere system.

    PubMed

    Howell, Rebecca M; Burgett, E A

    2014-09-01

    Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire energy range being measured, i.e., thermal to

  18. Secondary neutron spectrum from 250-MeV passively scattered proton therapy: Measurement with an extended-range Bonner sphere system

    PubMed Central

    Howell, Rebecca M.; Burgett, E. A.

    2014-01-01

    Purpose: Secondary neutrons are an unavoidable consequence of proton therapy. While the neutron dose is low compared to the primary proton dose, its presence and contribution to the patient dose is nonetheless important. The most detailed information on neutrons includes an evaluation of the neutron spectrum. However, the vast majority of the literature that has reported secondary neutron spectra in proton therapy is based on computational methods rather than measurements. This is largely due to the inherent limitations in the majority of neutron detectors, which are either not suitable for spectral measurements or have limited response at energies greater than 20 MeV. Therefore, the primary objective of the present study was to measure a secondary neutron spectrum from a proton therapy beam using a spectrometer that is sensitive to neutron energies over the entire neutron energy spectrum. Methods: The authors measured the secondary neutron spectrum from a 250-MeV passively scattered proton beam in air at a distance of 100 cm laterally from isocenter using an extended-range Bonner sphere (ERBS) measurement system. Ambient dose equivalent H*(10) was calculated using measured fluence and fluence-to-ambient dose equivalent conversion coefficients. Results: The neutron fluence spectrum had a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate energy continuum between the thermal and evaporation peaks. The H*(10) was dominated by the neutrons in the evaporation peak because of both their high abundance and the large quality conversion coefficients in that energy interval. The H*(10) 100 cm laterally from isocenter was 1.6 mSv per proton Gy (to isocenter). Approximately 35% of the dose equivalent was from neutrons with energies ≥20 MeV. Conclusions: The authors measured a neutron spectrum for external neutrons generated by a 250-MeV proton beam using an ERBS measurement system that was sensitive to neutrons over the entire

  19. A compact proton spectrometer for measurement of the absolute DD proton spectrum from which yield and ρR are determined in thin-shell inertial-confinement-fusion implosions.

    PubMed

    Rosenberg, M J; Zylstra, A B; Frenje, J A; Rinderknecht, H G; Johnson, M Gatu; Waugh, C J; Séguin, F H; Sio, H; Sinenian, N; Li, C K; Petrasso, R D; Glebov, V Yu; Hohenberger, M; Stoeckl, C; Sangster, T C; Yeamans, C B; LePape, S; Mackinnon, A J; Bionta, R M; Talison, B; Casey, D T; Landen, O L; Moran, M J; Zacharias, R A; Kilkenny, J D; Nikroo, A

    2014-10-01

    A compact, step range filter proton spectrometer has been developed for the measurement of the absolute DD proton spectrum, from which yield and areal density (ρR) are inferred for deuterium-filled thin-shell inertial confinement fusion implosions. This spectrometer, which is based on tantalum step-range filters, is sensitive to protons in the energy range 1-9 MeV and can be used to measure proton spectra at mean energies of ∼1-3 MeV. It has been developed and implemented using a linear accelerator and applied to experiments at the OMEGA laser facility and the National Ignition Facility (NIF). Modeling of the proton slowing in the filters is necessary to construct the spectrum, and the yield and energy uncertainties are ±<10% in yield and ±120 keV, respectively. This spectrometer can be used for in situ calibration of DD-neutron yield diagnostics at the NIF.

  20. Sensitivity studies of beam directionality, beam size, and neutron spectrum for a fission converter-based epithermal neutron beam for boron neutron capture therapy.

    PubMed

    Sakamoto, S; Kiger, W S; Harling, O K

    1999-09-01

    Sensitivity studies of epithermal neutron beam performance in boron neutron capture therapy are presented for realistic neutron beams with varying filter/moderator and collimator/delimiter designs to examine the relative importance of neutron beam spectrum, directionality, and size. Figures of merit for in-air and in-phantom beam performance are calculated via the Monte Carlo technique for different well-optimized designs of a fission converter-based epithermal neutron beam with head phantoms as the irradiation target. It is shown that increasing J/phi, a measure of beam directionality, does not always lead to corresponding monotonic improvements in beam performance. Due to the relatively low significance, for most configurations, of its effect on in-phantom performance and the large intensity losses required to produce beams with very high J/phi, beam directionality should not be considered an important figure of merit in epithermal neutron beam design except in terms of its consequences on patient positioning and collateral dose. Hardening the epithermal beam spectrum, while maintaining the specific fast neutron dose well below the inherent hydrogen capture dose, improves beam penetration and advantage depth and, as a desirable by-product, significantly increases beam intensity. Beam figures of merit are shown to be strongly dependent on beam size relative to target size. Beam designs with J/phi approximately 0.65-0.7, specific fast neutron doses of 2-2.6x10(-13) Gy cm2/n and beam sizes equal to or larger than the size of the head target produced the deepest useful penetration, highest therapeutic ratios, and highest intensities.

  1. Determining the wavelength spectrum of neutrons on the NG6 beam line at NCNR

    NASA Astrophysics Data System (ADS)

    Ivanov, Juliet

    2016-09-01

    Historically, in-beam experiments and bottle experiments have been performed to determine the lifetime of a free neutron. However, these two different experimental techniques have provided conflicting results. It is crucial to precisely and accurately elucidate the neutron lifetime for Big Bang Nucleosynthesis calculations and to investigate physics beyond the Standard Model. Therefore, we aimed to understand and minimize systematic errors present in the neutron beam experiment at the NIST Center for Neutron Research (NCNR). In order to reduce the uncertainty related to wavelength dependent corrections present in previous beam experiments, the wavelength spectrum of the NCNR reactor cold neutron beam must be known. We utilized a beam chopper and lithium detector to characterize the wavelength spectrum on the NG6 beam line at the NCNR. The experimental design and techniques employed will be discussed, and our results will be presented. Future plans to utilize our findings to improve the neutron lifetime measurement at NCNR will also be described.

  2. Toward a fractal spectrum approach for neutron and gamma pulse shape discrimination

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Zhe; Liu, Bing-Qi; Zuo, Zhuo; Wang, Lei; Zan, Gui-Bin; Tuo, Xian-Guo

    2016-06-01

    Accurately selecting neutron signals and discriminating γ signals from a mixed radiation field is a key research issue in neutron detection. This paper proposes a fractal spectrum discrimination approach by means of different spectral characteristics of neutrons and γ rays. Figure of merit and average discriminant error ratio are used together to evaluate the discrimination effects. Different neutron and γ signals with various noise and pulse pile-up are simulated according to real data in the literature. The proposed approach is compared with the digital charge integration and pulse gradient methods. It is found that the fractal approach exhibits the best discrimination performance, followed by the digital charge integration method and the pulse gradient method, respectively. The fractal spectrum approach is not sensitive to high frequency noise and pulse pile-up. This means that the proposed approach has superior performance for effective and efficient anti-noise and high discrimination in neutron detection. Supported by the National Natural Science Foundation of China (41274109), Sichuan Youth Science and Technology Innovation Research Team (2015TD0020), Scientific and Technological Support Program of Sichuan Province (2013FZ0022), and the Creative Team Program of Chengdu University of Technology.

  3. Sustainable Thorium Nuclear Fuel Cycles: A Comparison of Intermediate and Fast Neutron Spectrum Systems

    DOE PAGES

    Brown, Nicholas R.; Powers, Jeffrey J.; Feng, B.; ...

    2015-05-21

    This paper presents analyses of possible reactor representations of a nuclear fuel cycle with continuous recycling of thorium and produced uranium (mostly U-233) with thorium-only feed. The analysis was performed in the context of a U.S. Department of Energy effort to develop a compendium of informative nuclear fuel cycle performance data. The objective of this paper is to determine whether intermediate spectrum systems, having a majority of fission events occurring with incident neutron energies between 1 eV and 10 5 eV, perform as well as fast spectrum systems in this fuel cycle. The intermediate spectrum options analyzed include tight latticemore » heavy or light water-cooled reactors, continuously refueled molten salt reactors, and a sodium-cooled reactor with hydride fuel. All options were modeled in reactor physics codes to calculate their lattice physics, spectrum characteristics, and fuel compositions over time. Based on these results, detailed metrics were calculated to compare the fuel cycle performance. These metrics include waste management and resource utilization, and are binned to accommodate uncertainties. The performance of the intermediate systems for this selfsustaining thorium fuel cycle was similar to a representative fast spectrum system. However, the number of fission neutrons emitted per neutron absorbed limits performance in intermediate spectrum systems.« less

  4. Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Weilacher, F.; Radha, P. B.; Forrest, C.

    Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium–tritium (D–T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. Here, it is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [T. R.more » Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D–D and D–T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D–D reaction, whereas they insignificantly influence the inferred D–T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. Finally, this code will continue to be used for

  5. Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

    DOE PAGES

    Weilacher, F.; Radha, P. B.; Forrest, C.

    2018-04-26

    Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium–tritium (D–T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. Here, it is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [T. R.more » Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [M. M. Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D–D and D–T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D–D reaction, whereas they insignificantly influence the inferred D–T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. Finally, this code will continue to be used for

  6. Three-dimensional modeling of the neutron spectrum to infer plasma conditions in cryogenic inertial confinement fusion implosions

    NASA Astrophysics Data System (ADS)

    Weilacher, F.; Radha, P. B.; Forrest, C.

    2018-04-01

    Neutron-based diagnostics are typically used to infer compressed core conditions such as areal density and ion temperature in deuterium-tritium (D-T) inertial confinement fusion (ICF) implosions. Asymmetries in the observed neutron-related quantities are important to understanding failure modes in these implosions. Neutrons from fusion reactions and their subsequent interactions including elastic scattering and neutron-induced deuteron breakup reactions are tracked to create spectra. It is shown that background subtraction is important for inferring areal density from backscattered neutrons and is less important for the forward-scattered neutrons. A three-dimensional hydrodynamic simulation of a cryogenic implosion on the OMEGA Laser System [Boehly et al., Opt. Commun. 133, 495 (1997)] using the hydrodynamic code HYDRA [Marinak et al., Phys. Plasmas 8, 2275 (2001)] is post-processed using the tracking code IRIS3D. It is shown that different parts of the neutron spectrum from the view can be mapped into different regions of the implosion, enabling an inference of an areal-density map. It is also shown that the average areal-density and an areal-density map of the compressed target can be reconstructed with a finite number of detectors placed around the target chamber. Ion temperatures are inferred from the width of the D-D and D-T fusion neutron spectra. Backgrounds can significantly alter the inferred ion temperatures from the D-D reaction, whereas they insignificantly influence the inferred D-T ion temperatures for the areal densities typical of OMEGA implosions. Asymmetries resulting in fluid flow in the core are shown to influence the absolute inferred ion temperatures from both reactions, although relative inferred values continue to reflect the underlying asymmetry pattern. The work presented here is part of the wide range of the first set of studies performed with IRIS3D. This code will continue to be used for post-processing detailed hydrodynamic simulations

  7. Calibration of time of flight detectors using laser-driven neutron source

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mirfayzi, S. R.; Kar, S., E-mail: s.kar@qub.ac.uk; Ahmed, H.

    2015-07-15

    Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

  8. Calibration of time of flight detectors using laser-driven neutron source.

    PubMed

    Mirfayzi, S R; Kar, S; Ahmed, H; Krygier, A G; Green, A; Alejo, A; Clarke, R; Freeman, R R; Fuchs, J; Jung, D; Kleinschmidt, A; Morrison, J T; Najmudin, Z; Nakamura, H; Norreys, P; Oliver, M; Roth, M; Vassura, L; Zepf, M; Borghesi, M

    2015-07-01

    Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

  9. Calibration of time of flight detectors using laser-driven neutron source

    NASA Astrophysics Data System (ADS)

    Mirfayzi, S. R.; Kar, S.; Ahmed, H.; Krygier, A. G.; Green, A.; Alejo, A.; Clarke, R.; Freeman, R. R.; Fuchs, J.; Jung, D.; Kleinschmidt, A.; Morrison, J. T.; Najmudin, Z.; Nakamura, H.; Norreys, P.; Oliver, M.; Roth, M.; Vassura, L.; Zepf, M.; Borghesi, M.

    2015-07-01

    Calibration of three scintillators (EJ232Q, BC422Q, and EJ410) in a time-of-flight arrangement using a laser drive-neutron source is presented. The three plastic scintillator detectors were calibrated with gamma insensitive bubble detector spectrometers, which were absolutely calibrated over a wide range of neutron energies ranging from sub-MeV to 20 MeV. A typical set of data obtained simultaneously by the detectors is shown, measuring the neutron spectrum emitted from a petawatt laser irradiated thin foil.

  10. Neutron-scattering spectrum of cesium hydrogen dinitrate

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roziere, J.; Berney, C.V.

    1976-03-17

    The neutron-scattering spectrum of cesium hydrogen dinitrate was obtained in order to complete previously reported structural chemical studies obtained by x-ray diffraction and infrared-Raman spectra. The proton position was of particular interest. Satellite peak intensities suggested proton coupling to motions of the NO/sub 3//sup -/ groups, and therefore not located at the center of the distorted tetrahedron formed by four of the oxygen groups. The precise position of the proton was not established. (DDA)

  11. A compact proton spectrometer for measurement of the absolute DD proton spectrum from which yield and pR are determined in thin-shell inertial-confinement-fusion implosions

    DOE PAGES

    Rosenberg, M. J.; Zylstra, A. B.; Frenje, J. A.; ...

    2014-10-10

    A compact, step range filter proton spectrometer has been developed for the measurement of the absolute DD proton spectrum, from which yield and areal density (ρR) are inferred for deuterium-filled thin-shell inertial confinement fusion implosions. This spectrometer, which is based on tantalum step-range filters, is sensitive to protons in the energy range 1-9 MeV and can be used to measure proton spectra at mean energies of ~1-3 MeV. It has been developed and implemented using a linear accelerator and applied to experiments at the OMEGA laser facility and the National Ignition Facility (NIF). Modeling of the proton slowing in themore » filters is necessary to construct the spectrum, and the yield and energy uncertainties are ±<10% in yield and ±120 keV, respectively. This spectrometer can be used for in situ calibration of DD-neutron yield diagnostics at the NIF« less

  12. A compact proton spectrometer for measurement of the absolute DD proton spectrum from which yield and ρR are determined in thin-shell inertial-confinement-fusion implosions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rosenberg, M. J., E-mail: mrosenbe@mit.edu; Zylstra, A. B.; Frenje, J. A.

    2014-10-01

    A compact, step range filter proton spectrometer has been developed for the measurement of the absolute DD proton spectrum, from which yield and areal density (ρR) are inferred for deuterium-filled thin-shell inertial confinement fusion implosions. This spectrometer, which is based on tantalum step-range filters, is sensitive to protons in the energy range 1-9 MeV and can be used to measure proton spectra at mean energies of ~1-3 MeV. It has been developed and implemented using a linear accelerator and applied to experiments at the OMEGA laser facility and the National Ignition Facility (NIF). Modeling of the proton slowing in themore » filters is necessary to construct the spectrum, and the yield and energy uncertainties are ±<10% in yield and ±120 keV, respectively. This spectrometer can be used for in situ calibration of DD-neutron yield diagnostics at the NIF.« less

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

    PubMed

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

    2015-11-01

    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. 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. 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. The NNS may be used to reliably measure the neutron

  14. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-05-15

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  15. Absolute nuclear material assay

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2010-07-13

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  16. Evaluation of a new neutron energy spectrum unfolding code based on an Adaptive Neuro-Fuzzy Inference System (ANFIS).

    PubMed

    Hosseini, Seyed Abolfazl; Esmaili Paeen Afrakoti, Iman

    2018-01-17

    The purpose of the present study was to reconstruct the energy spectrum of a poly-energetic neutron source using an algorithm developed based on an Adaptive Neuro-Fuzzy Inference System (ANFIS). ANFIS is a kind of artificial neural network based on the Takagi-Sugeno fuzzy inference system. The ANFIS algorithm uses the advantages of both fuzzy inference systems and artificial neural networks to improve the effectiveness of algorithms in various applications such as modeling, control and classification. The neutron pulse height distributions used as input data in the training procedure for the ANFIS algorithm were obtained from the simulations performed by MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). Taking into account the normalization condition of each energy spectrum, 4300 neutron energy spectra were generated randomly. (The value in each bin was generated randomly, and finally a normalization of each generated energy spectrum was performed). The randomly generated neutron energy spectra were considered as output data of the developed ANFIS computational code in the training step. To calculate the neutron energy spectrum using conventional methods, an inverse problem with an approximately singular response matrix (with the determinant of the matrix close to zero) should be solved. The solution of the inverse problem using the conventional methods unfold neutron energy spectrum with low accuracy. Application of the iterative algorithms in the solution of such a problem, or utilizing the intelligent algorithms (in which there is no need to solve the problem), is usually preferred for unfolding of the energy spectrum. Therefore, the main reason for development of intelligent algorithms like ANFIS for unfolding of neutron energy spectra is to avoid solving the inverse problem. In the present study, the unfolded neutron energy spectra of 252Cf and 241Am-9Be neutron sources using the developed computational code were

  17. First measurement of the VESUVIO neutron spectrum in the 30-80 MeV energy range using a Proton Recoil Telescope technique

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Tardocchi, M.; Croci, G.; Frost, C.; Giacomelli, L.; Grosso, G.; Hjalmarsson, A.; Rebai, M.; Rhodes, N. J.; Schooneveld, E. M.; Gorini, G.

    2013-11-01

    Measurements of the fast neutron energy spectrum at the ISIS spallation source are reported. The measurements were performed with a Proton Recoil Telescope consisting of a thin plastic foil placed in the neutron beam and two scintillator detectors. Results in the neutron energy range 30 MeV < En < 80 MeV are in good agreement with Monte Carlo simulations of the neutron spectrum.

  18. 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.

  19. Use of Apollo 17 Epoch Neutron Spectrum as a Benchmark in Testing LEND Collimated Sensor

    NASA Technical Reports Server (NTRS)

    Chin, Gordon; Sagdeev, R.; Milikh, G.

    2011-01-01

    The Apollo 17 neutron experiment LPNE provided a unique set of data on production of neutrons in the Lunar soil bombarded by Galactic Cosmic Rays (GCR). It serves as valuable "ground-truth" in the age of orbital remote sensing. We used the neutron data attributed to Apollo 17 epoch as a benchmark for testing the LEND's collimated sensor, as introduced by the geometry of collimator and efficiency of He3 counters. The latter is defined by the size of gas counter and pressure inside it. The intensity and energy spectrum of neutrons escaping the lunar surface are dependent on incident flux of Galactic Cosmic Rays (GCR) whose variability is associated with Solar Cycle and its peculiarities. We obtain first the share of neutrons entering through the field of view of collimator as a fraction of the total neutron flux by using the angular distribution of neutron exiting the Moon described by our Monte Carlo code. We computed next the count rate of the 3He sensor by using the neutron energy spectrum from McKinney et al. [JGR, 2006] and by consider geometry and gas pressure of the LEND sensor. Finally the neutron count rate obtained for the Apollo 17 epoch characterized by intermediate solar activity was adjusted to the LRO epoch characterized by low solar activity. It has been done by taking into account solar modulation potential, which affects the GCR flux, and in turn changes the neutron albedo flux.

  20. Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activationa)

    NASA Astrophysics Data System (ADS)

    Ruiz, C. L.; Chandler, G. A.; Cooper, G. W.; Fehl, D. L.; Hahn, K. D.; Leeper, R. J.; McWatters, B. R.; Nelson, A. J.; Smelser, R. M.; Snow, C. S.; Torres, J. A.

    2012-10-01

    The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the 63Cu(n,2n)62Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)4He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced 62Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given.

  1. Progress in obtaining an absolute calibration of a total deuterium-tritium neutron yield diagnostic based on copper activation.

    PubMed

    Ruiz, C L; Chandler, G A; Cooper, G W; Fehl, D L; Hahn, K D; Leeper, R J; McWatters, B R; Nelson, A J; Smelser, R M; Snow, C S; Torres, J A

    2012-10-01

    The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the (63)Cu(n,2n)(62)Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)(4)He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced (62)Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given.

  2. The lunar neutron energy spectrum inferred from the isotope compositions of rare-earth elements and hafnium in Apollo samples

    NASA Astrophysics Data System (ADS)

    Albalat, Emmanuelle; Blichert-Toft, Janne; Telouk, Philippe; Albarède, Francis

    2015-11-01

    The isotopic abundances of Sm, Gd, Dy, Er, Yb, and Hf have been measured in nine lunar samples by MC-ICP-MS. The data were corrected for both instrumental mass bias and natural isotope fractionation. We used the data to calculate the total flux and energy spectrum of the neutrons absorbed by the rocks. We write the constitutive equations of the isotopic changes for these elements induced by neutrons and solve the inverse problem by computing local energy averages. Resonant absorption peaks can be used as convenient kernels to define the spectrum of epithermal neutrons. We find that 149Sm and 157Gd anomalies correlate with neutron flux density for E < 0.015 eV (r2 > 0.98) and E ≈ 0.13 eV (r2 > 0.85), while no significant correlation exists between the ratio of these anomalies and the epithermal/thermal flux ratio at any value of energy. Neutron flux density variations can be used to trace the proportions of neutrons scattered out of the samples. The spectrum in the thermal region follows the expected E - 1 / 2 dependence but with 'notches' corresponding to neutron absorption. A major notch at the lowest end of the epithermal neutron spectrum (0.2-0.8 eV) is possibly due to absorption of neutrons by 151Eu, 167Er, and 149Sm. In general, we find a rather good correlation between the neutron flux density at specific energies and the exposure age, which suggests a mean residence time of the samples at the surface of the regolith of 2-300 Ma. Another correlation of epithermal neutrons with sample wt% FeO + TiO2 is consistent with orbital reflectance observations.

  3. Evaluated Mean Values and Covariances for the Prompt Fission Neutron Spectrum of 239Pu induced by neutrons of 500 keV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Neudecker, Denise

    2014-07-10

    This document provides the numerical values of the evaluated prompt fission neutron spectrum for 239Pu induced by neutrons of 500 keV as well as relative uncertainties and correlations. This document also contains a short description how these data were obtained and shows plots comparing the evaluated results to experimental information as well as the corresponding ENDF/B-VII.1 evaluation.

  4. Measurements of the neutron spectrum on the Martian surface with MSL/RAD

    NASA Astrophysics Data System (ADS)

    Köhler, J.; Zeitlin, C.; Ehresmann, B.; Wimmer-Schweingruber, R. F.; Hassler, D. M.; Reitz, G.; Brinza, D. E.; Weigle, G.; Appel, J.; Böttcher, S.; Böhm, E.; Burmeister, S.; Guo, J.; Martin, C.; Posner, A.; Rafkin, S.; Kortmann, O.

    2014-03-01

    The Radiation Assessment Detector (RAD), onboard the Mars Science Laboratory (MSL) rover Curiosity, measures the energetic charged and neutral particles and the radiation dose rate on the surface of Mars. An important factor for determining the biological impact of the Martian surface radiation is the specific contribution of neutrons, with their deeper penetration depth and ensuing high biological effectiveness. This is very difficult to measure quantitatively, resulting in considerable uncertainties in the total radiation dose. In contrast to charged particles, neutral particles (neutrons and gamma rays) are generally only measured indirectly. Measured spectra are a complex convolution of the incident particle spectrum with the detector response function and must be unfolded. We apply an inversion method (based on a maximum likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. Here we show the first spectra on the surface of Mars and compare them to theoretical predictions. The measured neutron spectrum (ranging from 8 to 740 MeV) translates into a radiation dose rate of 14±4μGy/d and a dose equivalent rate of 61±15μSv/d. This corresponds to 7% of the measured total surface dose rate and 10% of the biologically relevant surface dose equivalent rate on Mars. Measuring the Martian neutron and gamma spectra is an essential step for determining the mutagenic influences to past or present life at or beneath the Martian surface as well as the radiation hazard for future human exploration, including the shielding design of a potential habitat.

  5. Study of muon-induced neutron production using accelerator muon beam at CERN

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nakajima, Y.; Lin, C. J.; Ochoa-Ricoux, J. P.

    2015-08-17

    Cosmogenic muon-induced neutrons are one of the most problematic backgrounds for various underground experiments for rare event searches. In order to accurately understand such backgrounds, experimental data with high-statistics and well-controlled systematics is essential. We performed a test experiment to measure muon-induced neutron production yield and energy spectrum using a high-energy accelerator muon beam at CERN. We successfully observed neutrons from 160 GeV/c muon interaction on lead, and measured kinetic energy distributions for various production angles. Works towards evaluation of absolute neutron production yield is underway. This work also demonstrates that the setup is feasible for a future large-scale experimentmore » for more comprehensive study of muon-induced neutron production.« less

  6. On the solar cycle variation in the barometer coefficients of high latitude neutron monitors

    NASA Technical Reports Server (NTRS)

    Kusunose, M.; Ogita, N.

    1985-01-01

    Evaluation of barometer coefficients of neutron monitors located at high latitudes has been performed by using the results of the spherical harmonic analysis based on the records from around twenty stations for twelve years from January 1966 to December 1977. The average of data at eight stations, where continuous records are available for twelve years, show that the absolute value of barometer coefficient is in positive correlation with the cosmic ray neutron intensity. The variation rate of the barometer coefficient to the cosmic ray neutron intensity is influenced by the changes in the cutoff rigidity and in the primary spectrum.

  7. Investigation of the influence of the neutron spectrum in determinations of integral cross-section ratios

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Smith, D.L.

    1987-11-01

    Ratio measurements are routinely employed in studies of neutron interaction processes in order to generate new differential cross-section data or to test existing differential cross-section information through examination of the corresponding response in integral neutron spectra. Interpretation of such data requires that careful attention be given to details of the neutron spectra involved in these measurements. Two specific tasks are undertaken in the present investigation: (1) Using perturbation theory, a formula is derived which permits one to relate the ratio measured in a realistic quasimonoenergetic spectrum to the desired pure monoenergetic ratio. This expression involves only the lowest-order moments ofmore » the neutron energy distribution and corresponding parameters which serve to characterize the energy dependence of the differential cross sections, quantities which can generally be estimated with reasonable precision from the uncorrected data or from auxiliary information. (2) Using covariance methods, a general formalism is developed for calculating the uncertainty of a measured integral cross-section ratio which involves an arbitrary neutron spectrum. This formalism is employed to further examine the conditions which influence the sensitivity of such measured ratios to details of the neutron spectra and to their uncertainties. Several numerical examples are presented in this report in order to illustrate these principles, and some general conclusion are drawn concerning the development and testing of neutron cross-section data by means of ratio experiments. 16 refs., 1 fig., 4 tabs.« less

  8. Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory.

    PubMed

    Köhler, J; Ehresmann, B; Zeitlin, C; Wimmer-Schweingruber, R F; Hassler, D M; Reitz, G; Brinza, D E; Appel, J; Böttcher, S; Böhm, E; Burmeister, S; Guo, J; Lohf, H; Martin, C; Posner, A; Rafkin, S

    2015-04-01

    The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) measured the radiation environment inside the spacecraft during most of the 253-day, 560-million-kilometer cruise to Mars. An important factor for determining the biological impact of the radiation environment inside the spacecraft is the specific contribution of neutrons with their high biological effectiveness. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. The measured neutron spectrum (12-436 MeV) translates into a radiation dose rate of 3.8±1.2 μGy/day and a dose equivalent of 19±5 μSv/day. Extrapolating the measured spectrum (0.1-1000 MeV), we find that the total neutron-induced dose rate is 6±2 μGy/day and the dose equivalent rate is 30±10 μSv/day. For a 360 day round-trip from Earth to Mars with comparable shielding, this translates into a neutron induced dose equivalent of about 11±4 mSv. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

  9. The 235U prompt fission neutron spectrum measured by the Chi-Nu project at LANSCE

    DOE PAGES

    Gomez, J. A.; Devlin, M.; Haight, R. C.; ...

    2017-09-13

    The Chi-Nu experiment aims to accurately measure the prompt fission neutron spectrum for the major actinides. At the Los Alamos Neutron Science Center (LANSCE), fission can be induced with neutrons ranging from 0.7 MeV and above. Using a two arm time-of-flight (TOF) technique, the fission neutrons are measured in one of two arrays: a 22- 6Li glass array for lower energies, or a 54-liquid scintillator array for outgoing energies of 0.5 MeV and greater. Presented here are the collaboration's preliminary efforts at measuring the 235U PFNS.

  10. The 235U prompt fission neutron spectrum measured by the Chi-Nu project at LANSCE

    NASA Astrophysics Data System (ADS)

    Gomez, J. A.; Devlin, M.; Haight, R. C.; O'Donnell, J. M.; Lee, H. Y.; Mosby, S. M.; Taddeucci, T. N.; Kelly, K. J.; Fotiades, N.; Neudecker, D.; White, M. C.; Talou, P.; Rising, M. E.; Solomon, C. J.; Wu, C. Y.; Bucher, B.; Buckner, M. Q.; Henderson, R. A.

    2017-09-01

    The Chi-Nu experiment aims to accurately measure the prompt fission neutron spectrum for the major actinides. At the Los Alamos Neutron Science Center (LANSCE), fission can be induced with neutrons ranging from 0.7 MeV and above. Using a two arm time-of-flight (TOF) technique, the fission neutrons are measured in one of two arrays: a 22-6Li glass array for lower energies, or a 54-liquid scintillator array for outgoing energies of 0.5 MeV and greater. Presented here are the collaboration's preliminary efforts at measuring the 235U PFNS.

  11. The Prompt Fission Neutron Spectrum of 235U for Einc 0.7-5.0 MeV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gomez, Jaime A.; Devlin, Matthew James; Haight, Robert Cameron

    2017-03-23

    The Chi-Nu experiment aims to accurately measure the prompt fission neutron spectrum (PFNS) for the major actinides. At the Los Alamos Neutron Science Center (LANSCE), fission can be induced using the white neutron source. Using a two arm time of flight (T.O.F) technique; Chi-Nu presents a preliminary result of the low energy component of the 235U PFNS measured using an array of 22-Lithium glass scintillators.

  12. Microstructural evolution of pure tungsten neutron irradiated with a mixed energy spectrum

    DOE PAGES

    Koyanagi, Takaaki; Kumar, N. A. P. Kiran; Hwang, Taehyun; ...

    2017-04-13

    Here, microstructures of single-crystal bulk tungsten (W) and polycrystalline W foil with a strong grain texture were investigated using transmission electron microscopy following neutron irradiation at ~90–800 °C to 0.03–4.6 displacements per atom (dpa) in the High Flux Isotope Reactor with a mixed energy spectrum. The dominant irradiation defects were dislocation loops and small clusters at ~90 °C. Additional voids were formed in W irradiated at above 460 °C. Voids and precipitates involving transmutation rhenium and osmium were the dominant defects at more than ~1 dpa. We found a new phenomenon of microstructural evolution in irradiated polycrystalline W: Re- andmore » Os-rich precipitation along grain boundaries. Comparison of results between this study and previous studies using different irradiation facilities revealed that the microstructural evolution of pure W is highly dependent on the neutron energy spectrum in addition to the irradiation temperature and dose.« less

  13. Microstructural evolution of pure tungsten neutron irradiated with a mixed energy spectrum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koyanagi, Takaaki; Kumar, N. A. P. Kiran; Hwang, Taehyun

    Here, microstructures of single-crystal bulk tungsten (W) and polycrystalline W foil with a strong grain texture were investigated using transmission electron microscopy following neutron irradiation at ~90–800 °C to 0.03–4.6 displacements per atom (dpa) in the High Flux Isotope Reactor with a mixed energy spectrum. The dominant irradiation defects were dislocation loops and small clusters at ~90 °C. Additional voids were formed in W irradiated at above 460 °C. Voids and precipitates involving transmutation rhenium and osmium were the dominant defects at more than ~1 dpa. We found a new phenomenon of microstructural evolution in irradiated polycrystalline W: Re- andmore » Os-rich precipitation along grain boundaries. Comparison of results between this study and previous studies using different irradiation facilities revealed that the microstructural evolution of pure W is highly dependent on the neutron energy spectrum in addition to the irradiation temperature and dose.« less

  14. Microstructural evolution of pure tungsten neutron irradiated with a mixed energy spectrum

    NASA Astrophysics Data System (ADS)

    Koyanagi, Takaaki; Kumar, N. A. P. Kiran; Hwang, Taehyun; Garrison, Lauren M.; Hu, Xunxiang; Snead, Lance L.; Katoh, Yutai

    2017-07-01

    Microstructures of single-crystal bulk tungsten (W) and polycrystalline W foil with a strong grain texture were investigated using transmission electron microscopy following neutron irradiation at ∼90-800 °C to 0.03-4.6 displacements per atom (dpa) in the High Flux Isotope Reactor with a mixed energy spectrum. The dominant irradiation defects were dislocation loops and small clusters at ∼90 °C. Additional voids were formed in W irradiated at above 460 °C. Voids and precipitates involving transmutation rhenium and osmium were the dominant defects at more than ∼1 dpa. We found a new phenomenon of microstructural evolution in irradiated polycrystalline W: Re- and Os-rich precipitation along grain boundaries. Comparison of results between this study and previous studies using different irradiation facilities revealed that the microstructural evolution of pure W is highly dependent on the neutron energy spectrum in addition to the irradiation temperature and dose.

  15. Energy spectrum and flux of 3- to 20-Mev neutrons and 1- to 10-Mev gamma rays in the atmosphere

    NASA Technical Reports Server (NTRS)

    Klumpar, D. M.; Lockwood, J. A.; Saint Onge, R. N.; Friling, L. A.

    1973-01-01

    An experiment is described which was designed to measure the neutron and gamma ray energy spectrums and fluxes in the energy intervals 3 to 20 MeV and 1 to 10 MeV, respectively. In addition, from the 3 to 20-MeV proton recoil spectrums it is possible to infer the shape of the neutron energy spectrum from 20 to 50 MeV. The detecting system utilized a separate charged particle rejection scheme and a two-parameter display system for the output from the pulse shape discrimination which separated gamma rays from neutrons (n). Two long-duration flights were made with this detector in 1970 at Palestine, Tex. (P sub c = 4.6 Gv) and at Ft. Churchill, Canada (P sub c = 0.3 Gv).

  16. Unfolding neutron spectrum with Markov Chain Monte Carlo at MIT research Reactor with He-3 Neutral Current Detectors [Measuring neutron spectrum at MIT research reactor utilizing He-3 Bonner Cylinder Approach with an unfolding analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leder, A.; Anderson, A. J.; Billard, J.

    Here, the Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 10 18 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 3 2He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to producemore » a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.« less

  17. Unfolding neutron spectrum with Markov Chain Monte Carlo at MIT research Reactor with He-3 Neutral Current Detectors [Measuring neutron spectrum at MIT research reactor utilizing He-3 Bonner Cylinder Approach with an unfolding analysis

    DOE PAGES

    Leder, A.; Anderson, A. J.; Billard, J.; ...

    2018-02-02

    Here, the Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 10 18 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 3 2He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to producemore » a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.« less

  18. Doppler broadening of neutron-induced resonances using ab initio phonon spectrum

    NASA Astrophysics Data System (ADS)

    Noguere, G.; Maldonado, P.; De Saint Jean, C.

    2018-05-01

    Neutron resonances observed in neutron cross section data can only be compared with their theoretical analogues after a correct broadening of the resonance widths. This broadening is usually carried out by two different theoretical models, namely the Free Gas Model and the Crystal Lattice Model, which, however, are only applicable under certain assumptions. Here, we use neutron transmission experiments on UO2 samples at T=23.7 K and T=293.7 K, to investigate the limitations of these models when an ab initio phonon spectrum is introduced in the calculations. Comparisons of the experimental and theoretical transmissions highlight the underestimation of the energy transferred at low temperature and its impact on the accurate determination of the radiation widths Γ_{γ_{λ}} of the 238U resonances λ. The observed deficiency of the model represents an experimental evidence that the Debye-Waller factor is not correctly calculated at low temperature near the Neel temperature ( TN=30.8 K).

  19. Statistical Model Analysis of (n,p) Cross Sections and Average Energy For Fission Neutron Spectrum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Odsuren, M.; Khuukhenkhuu, G.

    2011-06-28

    Investigation of charged particle emission reaction cross sections for fast neutrons is important to both nuclear reactor technology and the understanding of nuclear reaction mechanisms. In particular, the study of (n,p) cross sections is necessary to estimate radiation damage due to hydrogen production, nuclear heating and transmutations in the structural materials of fission and fusion reactors. On the other hand, it is often necessary in practice to evaluate the neutron cross sections of the nuclides for which no experimental data are available.Because of this, we carried out the systematical analysis of known experimental (n,p) and (n,a) cross sections for fastmore » neutrons and observed a systematical regularity in the wide energy interval of 6-20 MeV and for broad mass range of target nuclei. To explain this effect using the compound, pre-equilibrium and direct reaction mechanisms some formulae were deduced. In this paper, in the framework of the statistical model known experimental (n,p) cross sections averaged over the thermal fission neutron spectrum of U-235 are analyzed. It was shown that the experimental data are satisfactorily described by the statistical model. Also, in the case of (n,p) cross sections the effective average neutron energy for fission spectrum of U-235 was found to be around 3 MeV.« less

  20. A Measurement of the Absolute Reactor Antineutrino Flux and Spectrum at Daya Bay

    NASA Astrophysics Data System (ADS)

    An, Fengpeng

    2017-12-01

    The Daya Bay Reactor Neutrino Experiment uses an array of eight underground detectors to study antineutrinos from six reactor cores with different baselines. Since the start of data-taking from late 2011, Daya Bay has collected the largest sample of reactor antineutrino events to date, and has made the most precise measurement of the neutrino oscillation parameters sin22θ13 and Δm2ee. Using the data from the four detectors in the near experimental halls, Daya Bay has made a high statistics measurement of the absolute reactor antineutrino flux and spectrum. In this paper we will present this measurement and its comparison to predictions based on different flux models.

  1. Use of boron nitride for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements

    NASA Astrophysics Data System (ADS)

    Radulović, Vladimir; Trkov, Andrej; Jaćimović, Radojko; Gregoire, Gilles; Destouches, Christophe

    2016-12-01

    A recent experimental irradiation and measurement campaign using containers made from boron nitride (BN) at the Jožef Stefan Institute (JSI) TRIGA Mark II reactor in Ljubljana, Slovenia, has shown the applicability of BN for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements. The first part of the paper focuses on the determination of the transmission function of a BN container through Monte Carlo calculations and experimental measurements. The second part presents the process of tayloring the sensitivity of integral activation measurements to specific needs and a selection of suitable radiative capture reactions for neutron spectrum characterization in the epithermal range. A BN container used in our experiments and its qualitative effect on the neutron spectrum in the irradiation position employed is displayed in the Graphical abstract.

  2. The Prompt Fission Neutron Spectrum of 235U(n,f) below 2.5 MeV for Incident Neutrons from 0.7 to 20 MeV

    NASA Astrophysics Data System (ADS)

    Devlin, M.; Gomez, J. A.; Kelly, K. J.; Haight, R. C.; O'Donnell, J. M.; Taddeucci, T. N.; Lee, H. Y.; Mosby, S. M.; Perdue, B. A.; Fotiades, N.; Ullmann, J. L.; Wu, C. Y.; Bucher, B.; Buckner, M. Q.; Henderson, R. A.; Neudecker, D.; White, M. C.; Talou, P.; Rising, M. E.; Solomon, C. J.

    2018-02-01

    New prompt fission neutron spectrum measurements are reported for 235U(n , f) reactions induced by neutrons with energies from 0.7 to 20 MeV. These measurements cover outgoing neutron energies from 2.5 MeV down to 10 keV, using an array of 6Li-glass scintillators for neutron detection and a double time-of-flight technique. The neutrons were produced at the Weapons Neutron Research facility of the Los Alamos Neutron Science Center. A detailed MCNP® model of the experimental equipment and the surrounding room was used to interpret the experimental results. Backgrounds were measured in situ, making use of the time-dependent singles rates of the various detectors with asynchronous readout from waveform digitizers. The results presented here have been included in a re-evaluation of the fission neutron spectra for this fissioning system, a description of which is presented elsewhere in this issue.

  3. Absolute instabilities of travelling wave solutions in a Keller-Segel model

    NASA Astrophysics Data System (ADS)

    Davis, P. N.; van Heijster, P.; Marangell, R.

    2017-11-01

    We investigate the spectral stability of travelling wave solutions in a Keller-Segel model of bacterial chemotaxis with a logarithmic chemosensitivity function and a constant, sublinear, and linear consumption rate. Linearising around the travelling wave solutions, we locate the essential and absolute spectrum of the associated linear operators and find that all travelling wave solutions have parts of the essential spectrum in the right half plane. However, we show that in the case of constant or sublinear consumption there exists a range of parameters such that the absolute spectrum is contained in the open left half plane and the essential spectrum can thus be weighted into the open left half plane. For the constant and sublinear consumption rate models we also determine critical parameter values for which the absolute spectrum crosses into the right half plane, indicating the onset of an absolute instability of the travelling wave solution. We observe that this crossing always occurs off of the real axis.

  4. Unfolding the neutron spectrum of a NE213 scintillator using artificial neural networks.

    PubMed

    Sharghi Ido, A; Bonyadi, M R; Etaati, G R; Shahriari, M

    2009-10-01

    Artificial neural networks technology has been applied to unfold the neutron spectra from the pulse height distribution measured with NE213 liquid scintillator. Here, both the single and multi-layer perceptron neural network models have been implemented to unfold the neutron spectrum from an Am-Be neutron source. The activation function and the connectivity of the neurons have been investigated and the results have been analyzed in terms of the network's performance. The simulation results show that the neural network that utilizes the Satlins transfer function has the best performance. In addition, omitting the bias connection of the neurons improve the performance of the network. Also, the SCINFUL code is used for generating the response functions in the training phase of the process. Finally, the results of the neural network simulation have been compared with those of the FORIST unfolding code for both (241)Am-Be and (252)Cf neutron sources. The results of neural network are in good agreement with FORIST code.

  5. Neutron range spectrometer

    DOEpatents

    Manglos, S.H.

    1988-03-10

    A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are colliminated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. 1 fig.

  6. Absolute limit on rotation of gravitationally bound stars

    NASA Astrophysics Data System (ADS)

    Glendenning, N. K.

    1994-03-01

    The authors seek an absolute limit on the rotational period for a neutron star as a function of its mass, based on the minimal constraints imposed by Einstein's theory of relativity, Le Chatelier's principle, causality, and a low-density equation of state, uncertainties which can be evaluated as to their effect on the result. This establishes a limiting curve in the mass-period plane below which no pulsar that is a neutron star can lie. For example, the minimum possible Kepler period, which is an absolute limit on rotation below which mass-shedding would occur, is 0.33 ms for a M = 1.442 solar mass neutron star (the mass of PSR1913+16). If the limit were found to be broken by any pulsar, it would signal that the confined hadronic phase of ordinary nucleons and nuclei is only metastable.

  7. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors.

    PubMed

    Waugh, C J; Rosenberg, M J; Zylstra, A B; Frenje, J A; Séguin, F H; Petrasso, R D; Glebov, V Yu; Sangster, T C; Stoeckl, C

    2015-05-01

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition, comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.

  8. The Prompt Fission Neutron Spectrum of 235U(n,f) below 2.5 MeV for Incident Neutrons from 0.7 to 20 MeV

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Devlin, Matthew James; Gomez, Jaime A.; Kelly, Keegan John

    New prompt fission neutron spectrum measurements are reported for 235U(n,f) reactions induced by neutrons with energies from 0.7 to 20 MeV. These measurements cover outgoing neutron energies from 2.5 MeV down to 10 keV, using an array of 6Li-glass scintillators for neutron detection and a double time-of-flight technique. The neutrons were produced at the Weapons Neutron Research facility of the Los Alamos Neutron Science Center. A detailed MCNP ® model of the experimental equipment and the surrounding room was used to interpret the experimental results. Backgrounds were measured in situ, making use of the time-dependent singles rates of the variousmore » detectors with asynchronous readout from waveform digitizers. The results presented here have been included in a re-evaluation of the fission neutron spectra for this fissioning system, a description of which is presented elsewhere in this issue.« less

  9. The Prompt Fission Neutron Spectrum of 235U(n,f) below 2.5 MeV for Incident Neutrons from 0.7 to 20 MeV

    DOE PAGES

    Devlin, Matthew James; Gomez, Jaime A.; Kelly, Keegan John; ...

    2018-02-01

    New prompt fission neutron spectrum measurements are reported for 235U(n,f) reactions induced by neutrons with energies from 0.7 to 20 MeV. These measurements cover outgoing neutron energies from 2.5 MeV down to 10 keV, using an array of 6Li-glass scintillators for neutron detection and a double time-of-flight technique. The neutrons were produced at the Weapons Neutron Research facility of the Los Alamos Neutron Science Center. A detailed MCNP ® model of the experimental equipment and the surrounding room was used to interpret the experimental results. Backgrounds were measured in situ, making use of the time-dependent singles rates of the variousmore » detectors with asynchronous readout from waveform digitizers. The results presented here have been included in a re-evaluation of the fission neutron spectra for this fissioning system, a description of which is presented elsewhere in this issue.« less

  10. Measuring Neutron Spectrum at MIT Research Reactor Utilizing He-3 Bonner Cylinder Approach with an Unfolding Analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leder, A.; Anderson, A. J.; Billard, J.

    2017-10-02

    The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2e18 neutrinos/second at the core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped a Bonner cylinder around a He-3 thermal neutron detector, whose data was then unfolded to produce a neutron energy spectrum across several orders of magnitude.more » We discuss the resulting spectrum and its implications for deploying Ricochet in the future at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.« less

  11. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    DOE PAGES

    Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.; ...

    2015-05-27

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

  12. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Waugh, C. J.; Rosenberg, M. J.; Zylstra, A. B.

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

  13. A method for in situ absolute DD yield calibration of neutron time-of-flight detectors on OMEGA using CR-39-based proton detectors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Waugh, C. J., E-mail: cjwaugh@mit.edu; Zylstra, A. B.; Frenje, J. A.

    2015-05-15

    Neutron time of flight (nTOF) detectors are used routinely to measure the absolute DD neutron yield at OMEGA. To check the DD yield calibration of these detectors, originally calibrated using indium activation systems, which in turn were cross-calibrated to NOVA nTOF detectors in the early 1990s, a direct in situ calibration method using CR-39 range filter proton detectors has been successfully developed. By measuring DD neutron and proton yields from a series of exploding pusher implosions at OMEGA, a yield calibration coefficient of 1.09 ± 0.02 (relative to the previous coefficient) was determined for the 3m nTOF detector. In addition,more » comparison of these and other shots indicates that significant reduction in charged particle flux anisotropies is achieved when bang time occurs significantly (on the order of 500 ps) after the trailing edge of the laser pulse. This is an important observation as the main source of the yield calibration error is due to particle anisotropies caused by field effects. The results indicate that the CR-39-nTOF in situ calibration method can serve as a valuable technique for calibrating and reducing the uncertainty in the DD absolute yield calibration of nTOF detector systems on OMEGA, the National Ignition Facility, and laser megajoule.« less

  14. Measurement of Fission Neutron Spectrum and Multiplicity using a Gamma Tag Double Time-of-flight Setup

    NASA Astrophysics Data System (ADS)

    Blain, E.; Daskalakis, A.; Danon, Y.

    2014-05-01

    Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer Polytechnic Institute (RPI) utilizing an array of EJ-301 liquid scintillators as well as lithium glass and plastic scintillators to experimentally determine these values. An array of BaF2 detectors was recently obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The system uses a novel gamma tagging method for fission which can offer an improvement over conventional fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing. Additionally, a 252Cf fission chamber was designed and constructed at RPI which allowed for optimization and testing of the system without the need for an external neutron source. The characteristics of the gamma tagging method such as false detection rate and detection efficiency were determined using this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of the various detectors. Plastic scintillators were found to offer a significant improvement over traditional liquid scintillators allowing energy measurements down to 50 keV. Background was also characterized for all detectors and will be discussed.

  15. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Prasad, Mano K.; Snyderman, Neal J.; Rowland, Mark S.

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  16. Absolute nuclear material assay using count distribution (LAMBDA) space

    DOEpatents

    Prasad, Manoj K [Pleasanton, CA; Snyderman, Neal J [Berkeley, CA; Rowland, Mark S [Alamo, CA

    2012-06-05

    A method of absolute nuclear material assay of an unknown source comprising counting neutrons from the unknown source and providing an absolute nuclear material assay utilizing a model to optimally compare to the measured count distributions. In one embodiment, the step of providing an absolute nuclear material assay comprises utilizing a random sampling of analytically computed fission chain distributions to generate a continuous time-evolving sequence of event-counts by spreading the fission chain distribution in time.

  17. Optimization of Neutron Spectrum in Northwest Beam Tube of Tehran Research Reactor for BNCT, by MCNP Code

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zamani, M.; End of North Kargar st, Atomic Energy Organization of Iran, P.O. Box: 14155-1339, Tehran; Kasesaz, Y.

    2015-07-01

    In order to gain the neutron spectrum with proper components specification for BNCT, it is necessary to design a Beam Shape Assembling (BSA), include of moderator, collimator, reflector, gamma filter and thermal neutrons filter, in front of the initial radiation beam from the source. According to the result of MCNP4C simulation, the Northwest beam tube has the most optimized neuron flux between three north beam tubes of Tehran Research Reactor (TRR). So, it has been chosen for this purpose. Simulation of the BSA has been done in four above mentioned phases. In each stage, ten best configurations of materials withmore » different length and width were selected as the candidates for the next stage. The last BSA configuration includes of: 78 centimeters of air as an empty space, 40 centimeters of Iron plus 52 centimeters of heavy-water as moderator, 30 centimeters of water or 90 centimeters of Aluminum-Oxide as a reflector, 1 millimeters of lithium (Li) as thermal neutrons filter and finally 3 millimeters of Bismuth (Bi) as a filter of gamma radiation. The result of Calculations shows that if we use this BSA configuration for TRR Northwest beam tube, then the best neutron flux and spectrum will be achieved for BNCT. (authors)« less

  18. A Neutron Diffractometer for a Long Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Sokol, Paul; Wang, Cailin

    Long pulsed neutron sources are being actively developed as small university based sources and are being considered for the next generation of high powered sources, such as the European Neutron Source (ESS) and the Spallation Neutron Source (SNS) second target station. New instrumentation concepts will be required to effectively utilize the full spectrum of neutrons generated by these sources. Neutron diffractometers, which utilize time-of-flight (TOF) techniques for wavelength resolution, are particularly problematic. We describe an instrument for a long pulsed source that provides resolution comparable to that obtained on short pulsed sources without the need of long incident flight paths. We accomplish this by utilizing high speed choppers to impose a time structure on the spectrum of incident neutrons. By strategically positioning these choppers the response matrix assumes a convenient form that can be deconvoluted from the measured TOF spectrum to produce the diffraction pattern of the sample. We compare the performance of this instrument to other possible diffraction instruments that could be utilized on a long pulsed source.

  19. Unfolding Neutron Spectrum with Markov Chain Monte Carlo at MIT Research Reactor with He-3 Neutral Current Detectors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Leder, A.; Anderson, A. J.; Billard, J.

    2018-02-02

    The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 1018 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 32He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to produce a neutron energymore » spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.« less

  20. Unfolding neutron spectrum with Markov Chain Monte Carlo at MIT research Reactor with He-3 Neutral Current Detectors

    NASA Astrophysics Data System (ADS)

    Leder, A.; Anderson, A. J.; Billard, J.; Figueroa-Feliciano, E.; Formaggio, J. A.; Hasselkus, C.; Newman, E.; Palladino, K.; Phuthi, M.; Winslow, L.; Zhang, L.

    2018-02-01

    The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CEνNS) using dark-matter-style detectors with sub-keV thresholds placed near a neutrino source, such as the MIT (research) Reactor (MITR), which operates at 5.5 MW generating approximately 2.2 × 1018 ν/second in its core. Currently, Ricochet is characterizing the backgrounds at MITR, the main component of which comes in the form of neutrons emitted from the core simultaneous with the neutrino signal. To characterize this background, we wrapped Bonner cylinders around a 32He thermal neutron detector, whose data was then unfolded via a Markov Chain Monte Carlo (MCMC) to produce a neutron energy spectrum across several orders of magnitude. We discuss the resulting spectrum and its implications for deploying Ricochet at the MITR site as well as the feasibility of reducing this background level via the addition of polyethylene shielding around the detector setup.

  1. Absence of a dose-fractionation effect on neoplastic transformation induced by fission-spectrum neutrons in C3H 10T1/2 cells

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Saran, A.; Pazzaglia, S.; Coppola, M.

    1991-06-01

    We have investigated the effect of fission-spectrum neutron dose fractionation on neoplastic transformation of exponentially growing C3H 10T1/2 cells. Total doses of 10.8, 27, 54, and 108 cGy were given in single doses or in five equal fractions delivered at 24-h intervals in the biological channel of the RSV-TAPIRO reactor at CRE-Casaccia. Both cell inactivation and neoplastic transformation were more effectively induced by fission neutrons than by 250-kVp X rays. No significant effect on cell survival or neoplastic transformation was observed with split doses compared to single doses of fission-spectrum neutrons. Neutron RBE values relative to X rays determined frommore » data for survival and neoplastic transformation were comparable.« less

  2. Fission Spectrum

    DOE R&D Accomplishments Database

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  3. High-resolution measurements of the DT neutron spectrum using new CD foils in the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gatu Johnson, M., E-mail: gatu@psfc.mit.edu; Frenje, J. A.; Li, C. K.

    2016-11-15

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. This paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ∼200 keV FWHM.

  4. High-resolution measurements of the DT neutron spectrum using new CD foils in the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility

    DOE PAGES

    Gatu Johnson, M.; Frenje, J. A.; Bionta, R. M.; ...

    2016-08-09

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. Here, this paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ~200 keV FWHM.

  5. High-resolution measurements of the DT neutron spectrum using new CD foils in the Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility.

    PubMed

    Gatu Johnson, M; Frenje, J A; Bionta, R M; Casey, D T; Eckart, M J; Farrell, M P; Grim, G P; Hartouni, E P; Hatarik, R; Hoppe, M; Kilkenny, J D; Li, C K; Petrasso, R D; Reynolds, H G; Sayre, D B; Schoff, M E; Séguin, F H; Skulina, K; Yeamans, C B

    2016-11-01

    The Magnetic Recoil neutron Spectrometer (MRS) on the National Ignition Facility measures the DT neutron spectrum from cryogenically layered inertial confinement fusion implosions. Yield, areal density, apparent ion temperature, and directional fluid flow are inferred from the MRS data. This paper describes recent advances in MRS measurements of the primary peak using new, thinner, reduced-area deuterated plastic (CD) conversion foils. The new foils allow operation of MRS at yields 2 orders of magnitude higher than previously possible, at a resolution down to ∼200 keV FWHM.

  6. T-T Neutron Spectrum from Inertial Confinement Implosions

    NASA Astrophysics Data System (ADS)

    Bacher, A. D.; Casey, D. T.; Frenje, J. A.; Gatu Johnson, M. J.; Manuel, M.; Sinenian, N.; Zylstra, A. B.; Séguin, F. H.; Li, C. K.; Petrasso, R. D.; Glebov, V. Yu; Radha, P. B.; Meyerhofer, D. D.; Sangster, T. C.; McNabb, D. P.; Amendt, P. A.; Boyd, R. N.; Caggiano, J. A.; Hatchett, S. P.; Pino, J. E.; Quaglioni, S.; Rygg, J. R.; Thompson, I. J.; Herrmann, H. W.; Kim, Y. H.

    2013-08-01

    A new technique that uses inertial confinement implosions for measuring low-energy nuclear reactions important to nuclear astrophysics is described. Simultaneous measurements of n-D and n-T elastic scattering at 14.1 MeV using deuterium-tritium gas-filled capsules provide a proof of principle for this technique. Measurements have been made of D(d,p)T (dd) and T(t,2n)4He (tt) reaction yields relative to the D(t,n)4He (dt) reaction yield for deuterium-tritium mixtures with f T / f D between 0.62 and 0.75 and for a wide range of ion temperatures to test our understanding of the implosion processes. Measurements of the shape of the neutron spectrum from the T(t,2n)4He reaction have been made for each of these target configurations.

  7. Proposed low-energy absolute calibration of nuclear recoils in a dual-phase noble element TPC using D-D neutron scattering kinematics

    NASA Astrophysics Data System (ADS)

    Verbus, J. R.; Rhyne, C. A.; Malling, D. C.; Genecov, M.; Ghosh, S.; Moskowitz, A. G.; Chan, S.; Chapman, J. J.; de Viveiros, L.; Faham, C. H.; Fiorucci, S.; Huang, D. Q.; Pangilinan, M.; Taylor, W. C.; Gaitskell, R. J.

    2017-04-01

    We propose a new technique for the calibration of nuclear recoils in large noble element dual-phase time projection chambers used to search for WIMP dark matter in the local galactic halo. This technique provides an in situ measurement of the low-energy nuclear recoil response of the target media using the measured scattering angle between multiple neutron interactions within the detector volume. The low-energy reach and reduced systematics of this calibration have particular significance for the low-mass WIMP sensitivity of several leading dark matter experiments. Multiple strategies for improving this calibration technique are discussed, including the creation of a new type of quasi-monoenergetic neutron source with a minimum possible peak energy of 272 keV. We report results from a time-of-flight-based measurement of the neutron energy spectrum produced by an Adelphi Technology, Inc. DD108 neutron generator, confirming its suitability for the proposed nuclear recoil calibration.

  8. Experimental characterization of the Advanced Liquid Hydrogen Cold Neutron Source spectrum of the NBSR reactor at the NIST Center for Neutron Research

    NASA Astrophysics Data System (ADS)

    Cook, J. C.; Barker, J. G.; Rowe, J. M.; Williams, R. E.; Gagnon, C.; Lindstrom, R. M.; Ibberson, R. M.; Neumann, D. A.

    2015-08-01

    The recent expansion of the National Institute of Standards and Technology (NIST) Center for Neutron Research facility has offered a rare opportunity to perform an accurate measurement of the cold neutron spectrum at the exit of a newly-installed neutron guide. Using a combination of a neutron time-of-flight measurement, a gold foil activation measurement, and Monte Carlo simulation of the neutron guide transmission, we obtain the most reliable experimental characterization of the Advanced Liquid Hydrogen Cold Neutron Source brightness to date. Time-of-flight measurements were performed at three distinct fuel burnup intervals, including one immediately following reactor startup. Prior to the latter measurement, the hydrogen was maintained in a liquefied state for an extended period in an attempt to observe an initial radiation-induced increase of the ortho (o)-hydrogen fraction. Since para (p)-hydrogen has a small scattering cross-section for neutron energies below 15 meV (neutron wavelengths greater than about 2.3 Å), changes in the o- p hydrogen ratio and in the void distribution in the boiling hydrogen influence the spectral distribution. The nature of such changes is simulated with a continuous-energy, Monte Carlo radiation-transport code using 20 K o and p hydrogen scattering kernels and an estimated hydrogen density distribution derived from an analysis of localized heat loads. A comparison of the transport calculations with the mean brightness function resulting from the three measurements suggests an overall o- p ratio of about 17.5(±1) % o- 82.5% p for neutron energies<15 meV, a significantly lower ortho concentration than previously assumed.

  9. Characterizing ICF Neutron Diagnostics on the nTOF line at SUNY Geneseo

    NASA Astrophysics Data System (ADS)

    Simone, Angela; Padalino, Stephen; Turner, Ethan; Ginnane, Mary Kate; Dubois, Natalie; Fletcher, Kurtis; Giordano, Michael; Lawson-Keister, Patrick; Harrison, Hannah; Visca, Hannah; Sangster, Craig; Regan, Sean

    2014-10-01

    Charged particle beams from the Geneseo 1.7 MV tandem Pelletron accelerator produce nuclear reactions that emit neutrons in the range of 0.5 to 17.9 MeV via the d(d,n)3He and 11B(d,n)12C reactions. The neutron energy and flux can be adjusted by controlling the accelerator beam current and potential. This adjustable neutron source makes it possible to calibrate ICF and HEDP neutron scintillator diagnostics. However, gamma rays which are often present during an accelerator-based calibration are difficult to differentiate from neutron signals in scintillators. To identify neutrons from gamma rays and to determine their energy, a permanent neutron time-of-flight (nTOF) line is being constructed. By detecting the scintillator signal in coincidence with an associated charged particle (ACP) produced in the reaction, the identity of the neutron can be known and its energy determined by time of flight. Using a 100% efficient surface barrier detector to count the ACPs, the absolute efficiency of the scintillator as a function of neutron energy can be determined. This is done by determining the ratio of the ACP counts in the singles spectrum to coincidence counts for matched solid angles of the SBD and scintillator. Funded in part by a LLE contract through the DOE.

  10. [BIOLOGICAL EFFECTIVENESS OF FISSION SPECTRUM NEUTRONS AND PROTONS WITH ENERGIES OF 60-126 MEV DURING ACUTE AND PROLONGED IRRADIATION].

    PubMed

    Shafirkin, A V

    2015-01-01

    Neutrons of the fission spectrum are characterized by relatively high values of linear energy transfer (LET). Data about their effects on biological objects are used to evaluate the risk of delayed effects of accelerated ions within the same LET range that serve as an experimental model of the nuclei component of galactic cosmic rays (GCR). Additionally, risks of delayed consequences to cosmonaut's health and average lifetime from certain GCR fluxes and secondary neutrons can be also prognosticated. The article deals with comparative analysis of the literature on reduction of average lifespan (ALS) of animals exposed to neutron reactor spectrum, 60-126 MeV protons, and X- and γ-rays in a broad range of radiation intensity and duration. It was shown that a minimal lifespan reduction by 5% occurs due to a brief exposure to neutrons with the absorbed dose of 5 cGy, whereas same lifespan reduction due to hard X- and γ-radiation occurs after absorption of a minimal dose of 100 cGy. Therefore, according to the estimated minimal ALS reduction in mice, neutron effectiveness is 20-fold higher. Biological effectiveness of protons as regards ALS reduction is virtually equal to that of standard types of radiation. Exposure to X- and γ-radiation with decreasing daily doses, and increasing number of fractions and duration gives rise to an apparent trend toward a less dramatic ALS reduction in mice; on the contrary, exposure to neutrons of varying duration had no effect on threshold doses for the specified ALS reductions. Factors of relative biological effectiveness of neutrons reached 40.

  11. Application of the BINS superheated drop detector spectrometer to the 9Be(p,xn) neutron energy spectrum determination

    NASA Astrophysics Data System (ADS)

    Di Fulvio, A.; Ciolini, R.; Mirzajani, N.; Romei, C.; d'Errico, F.; Bedogni, R.; Esposito, J.; Zafiropoulos, D.; Colautti, P.

    2013-07-01

    In the framework of TRASCO-BNCT project, a Bubble Interactive Neutron Spectrometer (BINS) device was applied to the characterization of the angle-and energy-differential neutron spectra generated by the 9Be(p,xn)reaction. The BINS spectrometer uses two superheated emulsion detectors, sequentially operated at different temperatures and thus provides a series of six sharp threshold responses, covering the 0.1-10 MeV neutron energy range. Spectrum unfolding of the data was performed by means of MAXED code. The obtained angle, energy-differential spectra were compared with those measured with a Bonner sphere spectrometer, a silicon telescope spectrometer and literature data.

  12. PERSONNEL NEUTRON DOSIMETER

    DOEpatents

    Fitzgerald, J.J.; Detwiler, C.G. Jr.

    1960-05-24

    A description is given of a personnel neutron dosimeter capable of indicating the complete spectrum of the neutron dose received as well as the dose for each neutron energy range therein. The device consists of three sets of indium foils supported in an aluminum case. The first set consists of three foils of indium, the second set consists of a similar set of indium foils sandwiched between layers of cadmium, whereas the third set is similar to the second set but is sandwiched between layers of polyethylene. By analysis of all the foils the neutron spectrum and the total dose from neutrons of all energy levels can be ascertained.

  13. Neutron beam characterization measurements at the Manuel Lujan Jr. neutron scattering center

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mocko, Michal; Muhrer, Guenter; Daemen, Luke L

    We have measured the neutron beam characteristics of neutron moderators at the Manuel Lujan Jr. Neutron Scattering Center at LANSCE. The absolute thermal neutron flux, energy spectra and time emission spectra were measured for the high resolution and high intensity decoupled water, partially coupled liquid hydrogen and partially coupled water moderators. The results of our experimental study will provide an insight into aging of different target-moderator-reflector-shield components as well as new experimental data for benchmarking of neutron transport codes.

  14. Secondary Neutron Doses to Pediatric Patients During Intracranial Proton Therapy: Monte Carlo Simulation of the Neutron Energy Spectrum and its Organ Doses.

    PubMed

    Matsumoto, Shinnosuke; Koba, Yusuke; Kohno, Ryosuke; Lee, Choonsik; Bolch, Wesley E; Kai, Michiaki

    2016-04-01

    Proton therapy has the physical advantage of a Bragg peak that can provide a better dose distribution than conventional x-ray therapy. However, radiation exposure of normal tissues cannot be ignored because it is likely to increase the risk of secondary cancer. Evaluating secondary neutrons generated by the interaction of the proton beam with the treatment beam-line structure is necessary; thus, performing the optimization of radiation protection in proton therapy is required. In this research, the organ dose and energy spectrum were calculated from secondary neutrons using Monte Carlo simulations. The Monte Carlo code known as the Particle and Heavy Ion Transport code System (PHITS) was used to simulate the transport proton and its interaction with the treatment beam-line structure that modeled the double scattering body of the treatment nozzle at the National Cancer Center Hospital East. The doses of the organs in a hybrid computational phantom simulating a 5-y-old boy were calculated. In general, secondary neutron doses were found to decrease with increasing distance to the treatment field. Secondary neutron energy spectra were characterized by incident neutrons with three energy peaks: 1×10, 1, and 100 MeV. A block collimator and a patient collimator contributed significantly to organ doses. In particular, the secondary neutrons from the patient collimator were 30 times higher than those from the first scatter. These results suggested that proactive protection will be required in the design of the treatment beam-line structures and that organ doses from secondary neutrons may be able to be reduced.

  15. Measurement of the neutron capture resonances for platinum using the Ge spectrometer and pulsed neutron beam at the J-PARC/MLF/ANNRI

    NASA Astrophysics Data System (ADS)

    Kino, Koichi; Hasemi, Hiroyuki; Kimura, Atsushi; Kiyanagi, Yoshiaki

    2017-09-01

    The neutron capture cross-section for platinum was measured at J-PARC/MLF/ANNRI. The intense pulsed neutron beam was impinging on a natural platinum foil sample and the emitted prompt γ-rays were detected by a Ge spectrometer. The peak energies of the low energy resonances for natural platinum are consistent with those of the JEFF-3.1.2, RUSFOND2010 and next-JENDL data libraries except for the 20-eV resonance. The resonance cross-sections of the next-JENDL library do not contradict the present measurements within the uncertainty of the absolute value of the present work. We analysed the prompt γ-ray spectrum and found a clear 7921.93 keV peak that originates from the transition from the 196Pt compound state to its ground state. The neutron capture cross-section for 195Pt was obtained by choosing events of this peak. The peak energies of most of the low energy resonances are almost consistent with those of the RUSFOND2010 and next-JENDL libraries. However, there was a disagreement for the 20-eV resonance.

  16. Using an interference spectrum as a short-range absolute rangefinder with fiber and wideband source

    NASA Astrophysics Data System (ADS)

    Hsieh, Tsung-Han; Han, Pin

    2018-06-01

    Recently, a new type of displacement instrument using spectral-interference has been found, which utilizes fiber and a wideband light source to produce an interference spectrum. In this work, we develop a method that measures the absolute air-gap distance by taking wavelengths at two interference spectra minima. The experimental results agree with the theoretical calculations. It is also utilized to produce and control the spectral switch, which is much easier than other previous methods using other control mechanisms. A scanning mode of this scheme for stepped surface measurement is suggested, which is verified by a standard thickness gauge test. Our scheme is different to one available on the market that may use a curve-fitting method, and some comparisons are made between our scheme and that one.

  17. 14 MeV calibration of JET neutron detectors—phase 1: calibration and characterization of the neutron source

    NASA Astrophysics Data System (ADS)

    Batistoni, P.; Popovichev, S.; Cufar, A.; Ghani, Z.; Giacomelli, L.; Jednorog, S.; Klix, A.; Lilley, S.; Laszynska, E.; Loreti, S.; Packer, L.; Peacock, A.; Pillon, M.; Price, R.; Rebai, M.; Rigamonti, D.; Roberts, N.; Tardocchi, M.; Thomas, D.; Contributors, JET

    2018-02-01

    In view of the planned DT operations at JET, a calibration of the JET neutron monitors at 14 MeV neutron energy is needed using a 14 MeV neutron generator deployed inside the vacuum vessel by the JET remote handling system. The target accuracy of this calibration is  ±10% as also required by ITER, where a precise neutron yield measurement is important, e.g. for tritium accountancy. To achieve this accuracy, the 14 MeV neutron generator selected as the calibration source has been fully characterised and calibrated prior to the in-vessel calibration of the JET monitors. This paper describes the measurements performed using different types of neutron detectors, spectrometers, calibrated long counters and activation foils which allowed us to obtain the neutron emission rate and the anisotropy of the neutron generator, i.e. the neutron flux and energy spectrum dependence on emission angle, and to derive the absolute emission rate in 4π sr. The use of high resolution diamond spectrometers made it possible to resolve the complex features of the neutron energy spectra resulting from the mixed D/T beam ions reacting with the D/T nuclei present in the neutron generator target. As the neutron generator is not a stable neutron source, several monitoring detectors were attached to it by means of an ad hoc mechanical structure to continuously monitor the neutron emission rate during the in-vessel calibration. These monitoring detectors, two diamond diodes and activation foils, have been calibrated in terms of neutrons/counts within  ±5% total uncertainty. A neutron source routine has been developed, able to produce the neutron spectra resulting from all possible reactions occurring with the D/T ions in the beam impinging on the Ti D/T target. The neutron energy spectra calculated by combining the source routine with a MCNP model of the neutron generator have been validated by the measurements. These numerical tools will be key in analysing the results from the in

  18. The perturbation of backscattered fast neutrons spectrum caused by the resonances of C, N and O for possible use in pyromaterial detection

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Abedin, Ahmad Firdaus Zainal, E-mail: firdaus087@gmail.com; Ibrahim, Noorddin; Zabidi, Noriza Ahmad

    2015-04-29

    Neutron radiation is able to determine the signature of land mine detection based on backscattering energy spectrum of landmine. In this study, the Monte Carlo simulation of backscattered fast neutrons was performed on four basic elements of land mine; hydrogen, nitrogen, oxygen and carbon. The moderation of fast neutrons to thermal neutrons and their resonances cross-section between 0.01 eV until 14 MeV were analysed. The neutrons energies were divided into 29 groups and ten million neutrons particles histories were used. The geometries consist of four main components: neutrons source, detectors, landmine and soil. The neutrons source was placed at the originmore » coordinate and shielded with carbon and polyethylene. Americium/Beryllium neutron source was placed inside lead casing of 1 cm thick and 2.5 cm height. Polyethylene was used to absorb and disperse radiation and was placed outside the lead shield of width 10 cm and height 7 cm. Two detectors were placed between source with distance of 8 cm and radius of 1.9 cm. Detectors of Helium-3 was used for neutron detection as it has high absorption cross section for thermal neutrons. For the anomaly, the physical is in cylinder form with radius of 10 cm and 8.9 cm height. The anomaly is buried 5 cm deep in the bed soil measured 80 cm radius and 53.5 cm height. The results show that the energy spectrum for the four basic elements of landmine with specific pattern which can be used as indication for the presence of landmines.« less

  19. Calculations to Support On-line Neutron Spectrum Adjustment by Measurements with Miniature Fission Chambers in the JSI TRIGA Reactor

    NASA Astrophysics Data System (ADS)

    Kaiba, Tanja; Radulović, Vladimir; Žerovnik, Gašper; Snoj, Luka; Fourmentel, Damien; Barbot, LoÏc; Destouches, Christophe AE(; )

    2018-01-01

    Preliminary calculations were performed with the aim to establish optimal experimental conditions for the measurement campaign within the collaboration between the Jožef Stefan Institute (JSI) and Commissariat à l'Énergie Atomique et aux Énergies Alternatives (CEA Cadarache). The goal of the project is to additionally characterize the neutron spectruminside the JSI TRIGA reactor core with focus on the measurement epi-thermal and fast part of the spectrum. Measurements will be performed with fission chambers containing different fissile materials (235U, 237Np and 242Pu) covered with thermal neutron filters (Cd and Gd). The changes in the detected signal and neutron flux spectrum with and without transmission filter were studied. Additional effort was put into evaluation of the effect of the filter geometry (e.g. opening on the top end of the filter) on the detector signal. After the analysis of the scoping calculations it was concluded to position the experiment in the outside core ring inside one of the empty fuel element positions.

  20. Absolute spectrum and charge ratio of cosmic ray muons in the energy region from 0.2 GeV to 100 GeV at 600 m above sea level

    NASA Technical Reports Server (NTRS)

    De Pascale, M. P.; Morselli, A.; Picozza, P.; Golden, R. L.; Grimani, C.; Kimbell, B. L.; Stephens, S. A.; Stochaj, S. J.; Webber, W. R.; Basini, G.

    1993-01-01

    We have determined the momentum spectrum and charge ratio of muons in the region from 250 MeV/c to 100 GeV/c using a superconducting magnetic spectrometer. The absolute differential spectrum of muons obtained in this experiment at 600 m above sea level is in good agreement with the previous measurements at sea level. The differential spectrum can be represented by a power law with a varying index, which is consistent with zero below 450 MeV/c and steepens to a value of -2.7 +/- 0.1 between 20 and 100 GeV/c. The integral f1ux of muons measured in this experiment span a very large range of momentum and is in excellent agreement with the earlier results. The positive to negative muon ratio appears to be constant in the entire momentum range covered in this experiment within the errors and the mean value is 1.220 +/- 0.044. The absolute momentum spectrum and the charge ratio measured in this experiment are also consistent with the theoretical expectations. This is the only experiment which covers a wide range of nearly three decades in momentum from a very low momentum.

  1. Neutron range spectrometer

    DOEpatents

    Manglos, Stephen H.

    1989-06-06

    A neutron range spectrometer and method for determining the neutron energy spectrum of a neutron emitting source are disclosed. Neutrons from the source are collimnated along a collimation axis and a position sensitive neutron counter is disposed in the path of the collimated neutron beam. The counter determines positions along the collimation axis of interactions between the neutrons in the neutron beam and a neutron-absorbing material in the counter. From the interaction positions, a computer analyzes the data and determines the neutron energy spectrum of the neutron beam. The counter is preferably shielded and a suitable neutron-absorbing material is He-3. The computer solves the following equation in the analysis: ##EQU1## where: N(x).DELTA.x=the number of neutron interactions measured between a position x and x+.DELTA.x, A.sub.i (E.sub.i).DELTA.E.sub.i =the number of incident neutrons with energy between E.sub.i and E.sub.i +.DELTA.E.sub.i, and C=C(E.sub.i)=N .sigma.(E.sub.i) where N=the number density of absorbing atoms in the position sensitive counter means and .sigma. (E.sub.i)=the average cross section of the absorbing interaction between E.sub.i and E.sub.i +.DELTA.E.sub.i.

  2. Study of the fission spectrum of less than 1 MeV neutrons using a Lithium-glass detector

    NASA Astrophysics Data System (ADS)

    Bastola, Suraj; Rees, Lawrence; Bart, Czirr

    2011-10-01

    The fission spectrum of neutrons with kinetic energies less than 1 MeV is of considerable practical importance for the design of nuclear reactors. However, it is not as precisely known as that for higher energy neutrons. One of the major problems scientists have previously encountered is room return neutrons. These are neutrons that reflect from the walls, ceiling or floor of the lab. Another problem is finding a way to measure accurately the neutron time of flight. This is the time neutrons take to travel from a fission event to the detector. Time of flight is used to measure the neutron energy. To avoid the room return, I am going to perform an experiment about 45 feet above the ground in the BYU Indoor Practice Facility, so that neutrons from the source will not scatter from nearby surfaces and return to the detector. To find the time of flight to a greater accuracy, I have been using a Time to Amplitude Converter (TAC). A TAC has a capacitor that charges linearly as the voltage builds up. With a 12-bit digitizer system, we can measure the time to 0.1 nanoseconds, whereas the same digitizer can only measure time in steps of 4 nanoseconds. So, we will get a more accurate measurement of time of flight with the TAC.

  3. Relativistically correct DD and DT neutron spectra

    NASA Astrophysics Data System (ADS)

    Appelbe, B.; Chittenden, J.

    2014-06-01

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

  4. Where Tori Fear to Tread: Hypermassive Neutron Star Remnants and Absolute Event Horizons or Topics in Computational General Relativity

    NASA Astrophysics Data System (ADS)

    Kaplan, Jeffrey Daniel

    2014-01-01

    Computational general relativity is a field of study which has reached maturity only within the last decade. This thesis details several studies that elucidate phenomena related to the coalescence of compact object binaries. Chapters 2 and 3 recounts work towards developing new analytical tools for visualizing and reasoning about dynamics in strongly curved spacetimes. In both studies, the results employ analogies with the classical theory of electricity and magnetism, first (Ch. 2) in the post-Newtonian approximation to general relativity and then (Ch. 3) in full general relativity though in the absence of matter sources. In Chapter 4, we examine the topological structure of absolute event horizons during binary black hole merger simulations conducted with the SpEC code. Chapter 6 reports on the progress of the SpEC code in simulating the coalescence of neutron star-neutron star binaries, while Chapter 7 tests the effects of various numerical gauge conditions on the robustness of black hole formation from stellar collapse in SpEC. In Chapter 5, we examine the nature of pseudospectral expansions of non-smooth functions motivated by the need to simulate the stellar surface in Chapters 6 and 7. In Chapter 8, we study how thermal effects in the nuclear equation of state effect the equilibria and stability of hypermassive neutron stars. Chapter 9 presents supplements to the work in Chapter 8, including an examination of the stability question raised in Chapter 8 in greater mathematical detail.

  5. Experimental research of neutron yield and spectrum from deuterium gas-puff z-pinch on the GIT-12 generator at current above 2 MA

    NASA Astrophysics Data System (ADS)

    Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Shishlov, A. V.; Cikhardt, J.; Cikhardtova, B.; Klir, D.; Kravarik, J.; Kubes, P.; Rezac, K.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.

    2017-05-01

    The Z-pinch experiments with deuterium gas-puff surrounded by an outer plasma shell were carried out on the GIT-12 generator (Tomsk, Russia) at currents of 2 MA. The plasma shell consisting of hydrogen and carbon ions was formed by 48 plasma guns. The deuterium gas-puff was created by a fast electromagnetic valve. This configuration provides an efficient mode of the neutron production in DD reaction, and the neutron yield reaches a value above 1012 neutrons per shot. Neutron diagnostics included scintillation TOF detectors for determination of the neutron energy spectrum, bubble detectors BD-PND, a silver activation detector, and several activation samples for determination of the neutron yield analysed by a Sodium Iodide (NaI) and a high-purity Germanium (HPGe) detectors. Using this neutron diagnostic complex, we measured the total neutron yield and amount of high-energy neutrons.

  6. TEMPEST II--A NEUTRON THERMALIZATION CODE

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shudde, R.H.; Dyer, J.

    The TEMPEST II neutron thermalization code in Fortran for IBM 709 or 7090 calculates thermal neutron flux spectra based upon the Wigner-Wilkins equation, the Wilkins equation, or the Maxwellian distribution. When a neutron spectrum is obtained, TEMPEST II provides microscopic and macroscopic cross section averages over that spectrum. Equations used by the code and sample input and output data are given. (auth)

  7. Advancing Absolute Calibration for JWST and Other Applications

    NASA Astrophysics Data System (ADS)

    Rieke, George; Bohlin, Ralph; Boyajian, Tabetha; Carey, Sean; Casagrande, Luca; Deustua, Susana; Gordon, Karl; Kraemer, Kathleen; Marengo, Massimo; Schlawin, Everett; Su, Kate; Sloan, Greg; Volk, Kevin

    2017-10-01

    We propose to exploit the unique optical stability of the Spitzer telescope, along with that of IRAC, to (1) transfer the accurate absolute calibration obtained with MSX on very bright stars directly to two reference stars within the dynamic range of the JWST imagers (and of other modern instrumentation); (2) establish a second accurate absolute calibration based on the absolutely calibrated spectrum of the sun, transferred onto the astronomical system via alpha Cen A; and (3) provide accurate infrared measurements for the 11 (of 15) highest priority stars with no such data but with accurate interferometrically measured diameters, allowing us to optimize determinations of effective temperatures using the infrared flux method and thus to extend the accurate absolute calibration spectrally. This program is integral to plans for an accurate absolute calibration of JWST and will also provide a valuable Spitzer legacy.

  8. Improved Bonner sphere neutron spectrometry measurements for the nuclear industry

    NASA Astrophysics Data System (ADS)

    Roberts, N. J.; Thomas, D. J.; Visser, T. P. P.

    2017-11-01

    A novel, two-stage approach has been developed for producing the a priori spectrum for Bonner sphere unfolding in a case where neutrons are produced by spontaneous fission and (α,n) reactions, e.g. in UF6. The code SOURCES 4C is first used to obtain the energy spectrum of the neutrons inside the material, which is then fed into a MCNP model of the entire geometry to derive the neutron spectrum at the location of the Bonner sphere. Using this as the a priori spectrum produces a much more detailed unfolded Bonner sphere spectrum retaining fine structure from the calculation that would not be present if a simple estimated spectrum had been used as the a priori spectrum. This is illustrated using a Bonner sphere measurement of the neutron energy spectrum produced by a 48Y cylinder of UF6. From the unfolded spectrum an estimate has been made of the neutron ambient dose equivalent, i.e. the quantity which a neutron survey instrument should measure. The difference in the ambient dose equivalent of the unfolded spectrum is over 10% when using the novel approach instead of using a simpler estimate consisting of a single high energy peak, 1/E continuum, and thermal peak.

  9. Evaluation of a neutron spectrum from Bonner spheres measurements using a Bayesian parameter estimation combined with the traditional unfolding methods

    NASA Astrophysics Data System (ADS)

    Mazrou, H.; Bezoubiri, F.

    2018-07-01

    In this work, a new program developed under MATLAB environment and supported by the Bayesian software WinBUGS has been combined to the traditional unfolding codes namely MAXED and GRAVEL, to evaluate a neutron spectrum from the Bonner spheres measured counts obtained around a shielded 241AmBe based-neutron irradiator located at a Secondary Standards Dosimetry Laboratory (SSDL) at CRNA. In the first step, the results obtained by the standalone Bayesian program, using a parametric neutron spectrum model based on a linear superposition of three components namely: a thermal-Maxwellian distribution, an epithermal (1/E behavior) and a kind of a Watt fission and Evaporation models to represent the fast component, were compared to those issued from MAXED and GRAVEL assuming a Monte Carlo default spectrum. Through the selection of new upper limits for some free parameters, taking into account the physical characteristics of the irradiation source, of both considered models, good agreement was obtained for investigated integral quantities i.e. fluence rate and ambient dose equivalent rate compared to MAXED and GRAVEL results. The difference was generally below 4% for investigated parameters suggesting, thereby, the reliability of the proposed models. In the second step, the Bayesian results obtained from the previous calculations were used, as initial guess spectra, for the traditional unfolding codes, MAXED and GRAVEL to derive the solution spectra. Here again the results were in very good agreement, confirming the stability of the Bayesian solution.

  10. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Korff, S. A.; Mendell, R. B.; Merker, M.; Light, E. S.; Verschell, H. J.; Sandie, W. S.

    1979-01-01

    Contributions to fast neutron measurements in the atmosphere are outlined. The results of a calculation to determine the production, distribution and final disappearance of atmospheric neutrons over the entire spectrum are presented. An attempt is made to answer questions that relate to processes such as neutron escape from the atmosphere and C-14 production. In addition, since variations of secondary neutrons can be related to variations in the primary radiation, comment on the modulation of both radiation components is made.

  11. Determination of neutron multiplication coefficients for fuel elements irradiated by spallation neutrons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bhatia, Chitra; Kumar, V.

    2010-02-15

    A neutron multiplication coefficient, k{sub eff}, has been estimated for spallation neutron flux using the data of spectrum average cross sections of all absorption, fission, and nonelastic reaction channels of {sup 232}Th, {sup 238}U, {sup 235}U, and {sup 233}U fuel elements. It has been revealed that in spallation neutron flux (i) nonfission, nonabsorption reactions play an important role in the calculation of k{sub eff}, (ii) one can obtain a high value of k{sub eff} even for fertile {sup 232}Th fuel, which is hardly possible in a conventional fast reactor, and (iii) spectrum average absorption cross sections of neutron poisons ofmore » a conventional reactor are relatively very small.« less

  12. Analysis of standard reference materials by absolute INAA

    NASA Astrophysics Data System (ADS)

    Heft, R. E.; Koszykowski, R. F.

    1981-07-01

    Three standard reference materials: flyash, soil, and ASI 4340 steel, are analyzed by a method of absolute instrumental neutron activation analysis. Two different light water pool-type reactors were used to produce equivalent analytical results even though the epithermal to thermal flux ratio in one reactor was higher than that in the other by a factor of two.

  13. Performance analysis of fusion nuclear-data benchmark experiments for light to heavy materials in MeV energy region with a neutron spectrum shifter

    NASA Astrophysics Data System (ADS)

    Murata, Isao; Ohta, Masayuki; Miyamaru, Hiroyuki; Kondo, Keitaro; Yoshida, Shigeo; Iida, Toshiyuki; Ochiai, Kentaro; Konno, Chikara

    2011-10-01

    Nuclear data are indispensable for development of fusion reactor candidate materials. However, benchmarking of the nuclear data in MeV energy region is not yet adequate. In the present study, benchmark performance in the MeV energy region was investigated theoretically for experiments by using a 14 MeV neutron source. We carried out a systematical analysis for light to heavy materials. As a result, the benchmark performance for the neutron spectrum was confirmed to be acceptable, while for gamma-rays it was not sufficiently accurate. Consequently, a spectrum shifter has to be applied. Beryllium had the best performance as a shifter. Moreover, a preliminary examination of whether it is really acceptable that only the spectrum before the last collision is considered in the benchmark performance analysis. It was pointed out that not only the last collision but also earlier collisions should be considered equally in the benchmark performance analysis.

  14. Neutron-beam-shaping assembly for boron neutron-capture therapy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zaidi, L.; Kashaeva, E. A.; Lezhnin, S. I.

    A neutron-beam-shaping assembly consisting of a moderator, a reflector, and an absorber is used to form a therapeutic neutron beam for the boron neutron-capture therapy of malignant tumors at accelerator neutron sources. A new structure of the moderator and reflector is proposed in the present article, and the results of a numerical simulation of the neutron spectrum and of the absorbed dose in a modified Snyder head phantom are presented. The application of a composite moderator and of a composite reflector and the implementation of neutron production at the proton energy of 2.3MeV are shown to permit obtaining a high-qualitymore » therapeutic neutron beam.« less

  15. Spectral correction factors for conventional neutron dosemeters used in high-energy neutron environments.

    PubMed

    Lee, K W; Sheu, R J

    2015-04-01

    High-energy neutrons (>10 MeV) contribute substantially to the dose fraction but result in only a small or negligible response in most conventional moderated-type neutron detectors. Neutron dosemeters used for radiation protection purpose are commonly calibrated with (252)Cf neutron sources and are used in various workplace. A workplace-specific correction factor is suggested. In this study, the effect of the neutron spectrum on the accuracy of dose measurements was investigated. A set of neutron spectra representing various neutron environments was selected to study the dose responses of a series of Bonner spheres, including standard and extended-range spheres. By comparing (252)Cf-calibrated dose responses with reference values based on fluence-to-dose conversion coefficients, this paper presents recommendations for neutron field characterisation and appropriate correction factors for responses of conventional neutron dosemeters used in environments with high-energy neutrons. The correction depends on the estimated percentage of high-energy neutrons in the spectrum or the ratio between the measured responses of two Bonner spheres (the 4P6_8 extended-range sphere versus the 6″ standard sphere). © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  16. Real time spectrometer for thermal neutrons from radiotherapic accelerators

    NASA Astrophysics Data System (ADS)

    Mozzanica, A.; Bartesaghi, G.; Bolognini, D.; Conti, V.; Mascagna, V.; Prest, M.; Scazzi, S.; Cappelletti, P.; Frigerio, M.; Gelosa, S.; Monti, A.; Ostinelli, A.; Bevilacqua, R.; Giannini, G.; Totaro, P.; Vallazza, E.

    2007-10-01

    Radiotherapy accelerators can produce high energy photon beams for deep tumour treatments. Photons with energies greater than 8 MeV produce neutrons via photoproduction. The PHONES (PHOto NEutron Source) project is developing a neutron moderator to use the photoproduced neutrons for BNCT (Boron Neutron Capture Therapy) in hospital environments. In this framework we are developing a real time spectrometer for thermal neutrons exploiting the bunch structure of the beam. Since the beam is produced by a linear accelerator, in fact, particles are sent to the patient in bunches with a rate of 150-300 Hz depending on the beam type and energy. The neutron spectrum is usually measured with integrating detectors such as bubble dosimeters or TLDs, which integrate over a time interval and an energy one. We are developing a scintillator detector to measure the neutron spectrum in real time in the interval between bunches, that is in the thermal region. The signals from the scintillator are discriminated and sampled by a dedicated clock in a Cyclone II FPGA by Altera, thus obtaining the neutron time of flight spectrum. The exploited physical process in ordinary plastic scintillators is neutron capture by H with a subsequent γ emission. The measured TOF spectrum has been compared with a BF 3 counter one. A dedicated simulation with MCNP is being developed to extract the energy spectrum from the TOF one. The paper will present the results of the prototype measurements and the status of the simulation.

  17. The Thermal Neutron Beam Option for NECTAR at MLZ

    NASA Astrophysics Data System (ADS)

    Mühlbauer, M. J.; Bücherl, T.; Genreith, C.; Knapp, M.; Schulz, M.; Söllradl, S.; Wagner, F. M.; Ehrenberg, H.

    The beam port SR10 at the neutron source FRM II of Heinz Maier-Leibnitz Zentrum (MLZ) is equipped with a moveable assembly of two uranium plates, which can be placed in front of the entrance window of the beam tube via remote control. With these plates placed in their operating position the thermal neutron spectrum produced by the neutron source FRM II is converted to fission neutrons with 1.9 MeV of mean energy. This fission neutron spectrum is routinely used for medical applications at the irradiation facility MEDAPP, for neutron radiography and tomography experiments at the facility NECTAR and for materials testing. If, however, the uranium plates are in their stand-by position far off the tip of the beam tube and the so-called permanent filter for thermal neutrons is removed, thermal neutrons originating from the moderator tank enter the beam tube and a thermal spectrum becomes available for irradiation or activation of samples. By installing a temporary flight tube the beam may be used for thermal neutron radiography and tomography experiments at NECTAR. The thermal neutron beam option not only adds a pure thermal neutron spectrum to the energy ranges available for neutron imaging at MLZ instruments but it also is an unique possibility to combine two quite different neutron energy ranges at a single instrument including their respective advantages. The thermal neutron beam option for NECTAR is funded by BMBF in frame of research project 05K16VK3.

  18. Large Survey of Neutron Spectrum Moments Due to ICF Drive Asymmetry

    NASA Astrophysics Data System (ADS)

    Field, J. E.; Munro, D.; Spears, B.; Peterson, J. L.; Brandon, S.; Gaffney, J. A.; Hammer, J.; Langer, S.; Nora, R. C.; Springer, P.; ICF Workflow Collaboration Collaboration

    2016-10-01

    We have recently completed the largest HYDRA simulation survey to date ( 60 , 000 runs) of drive asymmetry on the new Trinity computer at LANL. The 2D simulations covered a large space of credible perturbations to the drive of ICF implosions on the NIF. Cumulants of the produced birth energy spectrum for DD and DT reaction neutrons were tallied using new methods. Comparison of the experimental spectra with our map of predicted spectra from simulation should provide a wealth of information about the burning plasma region. We report on our results, highlighting areas of agreement (and disagreement) with experimental spectra. We also identify features in the predicted spectra that might be amenable to measurement with improved diagnostics. Prepared by LLNL under Contract DE-AC52-07NA27344. IM release #: LLNL-PROC-697321.

  19. High energy neutrons at balloon altitudes

    NASA Technical Reports Server (NTRS)

    Klumpar, D. M.; Lockwood, J. A.

    1974-01-01

    The flux and energy spectrum of fast neutrons (3 to 20 MeV) has been measured near the top of the atmosphere with an organic liquid scintillator. The omnidirectional neutron energy spectrum from 3 to 20 MeV at 3.5 g/sq cm over Palestine, Texas can be described by a power law with an energy dependent spectral index which varies from 1.8 (plus or minus .2) between 1 and 10 MeV to 0.3 (plus or minus .3) between 15 and 20 MeV. From 20 to 50 MeV, a neutron spectrum independence of E is consistent with our data.

  20. Measurement of the Neutron Lifetime Using a Proton Trap

    NASA Astrophysics Data System (ADS)

    Dewey, M. S.; Gilliam, D. M.; Nico, J. S.; Wietfeldt, F. E.; Fei, X.; Snow, W. M.; Greene, G. L.; Pauwels, J.; Eykens, R.; Lamberty, A.; van Gestel, J.

    2003-10-01

    We report a new measurement of the neutron decay lifetime by the absolute counting of in-beam neutrons and their decay protons. Protons were confined in a quasi-Penning trap and counted with a silicon detector. The neutron beam fluence was measured by capture in a thin 6LiF foil detector with known absolute efficiency. The combination of these simultaneous measurements gives the neu­tron lifetime: τn=(886.8±1.2[stat]±3.2[syst]) s. The systematic uncertainty is dominated by uncertainties in the mass of the 6LiF deposit and the 6Li(n,t) cross section. This is the most precise measurement of the neutron lifetime to date using an in-beam method.

  1. Self-Powered Neutron Detector Qualification for Absolute On-Line In-Pile Neutron Flux Measurements in BR2

    NASA Astrophysics Data System (ADS)

    Vermeeren, L.; Wéber, M.

    2003-06-01

    A set of ten Self-Powered Neutron Detectors with Co, Rh and Ag emitters has been irradiated in several channels of the BR2 research reactor at SCK•CEN aiming at a comparison of their performance as thermal neutron flux detectors under various conditions. To allow for a correct interpretation of their signals, all detector sensitivity contributions (prompt and delayed) were calculated using a dedicated Monte Carlo model. The various contributions were also measured separately; the agreement between calculated and experimental data, including data from activation dosimetry, was excellent. Detailed neutron flux profiles were obtained from the SPND data, after correction for the finite detector lengths and for the slow response of delayed SPNDs.

  2. Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Miller, Marcelo E.; Sztejnberg, Manuel L.; Gonzalez, Sara J.

    2011-12-15

    Purpose: A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comision Nacional de Energia Atomica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. Methods: The first calibration of the detector was done with themore » well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Results: Local mixed-field thermal neutron sensitivities and

  3. Rhodium self-powered neutron detector as a suitable on-line thermal neutron flux monitor in BNCT treatments.

    PubMed

    Miller, Marcelo E; Sztejnberg, Manuel L; González, Sara J; Thorp, Silvia I; Longhino, Juan M; Estryk, Guillermo

    2011-12-01

    A rhodium self-powered neutron detector (Rh SPND) has been specifically developed by the Comisión Nacional de Energía Atómica (CNEA) of Argentina to measure locally and in real time thermal neutron fluxes in patients treated with boron neutron capture therapy (BNCT). In this work, the thermal and epithermal neutron response of the Rh SPND was evaluated by studying the detector response to two different reactor spectra. In addition, during clinical trials of the BNCT Project of the CNEA, on-line neutron flux measurements using the specially designed detector were assessed. The first calibration of the detector was done with the well-thermalized neutron spectrum of the CNEA RA-3 reactor thermal column. For this purpose, the reactor spectrum was approximated by a Maxwell-Boltzmann distribution in the thermal energy range. The second calibration was done at different positions along the central axis of a water-filled cylindrical phantom, placed in the mixed thermal-epithermal neutron beam of CNEA RA-6 reactor. In this latter case, the RA-6 neutron spectrum had been well characterized by both calculation and measurement, and it presented some marked differences with the ideal spectrum considered for SPND calibrations at RA-3. In addition, the RA-6 neutron spectrum varied with depth in the water phantom and thus the percentage of the epithermal contribution to the total neutron flux changed at each measurement location. Local (one point-position) and global (several points-positions) and thermal and mixed-field thermal neutron sensitivities were determined from these measurements. Thermal neutron flux was also measured during BNCT clinical trials within the irradiation fields incident on the patients. In order to achieve this, the detector was placed on patient's skin at dosimetric reference points for each one of the fields. System stability was adequate for this kind of measurement. Local mixed-field thermal neutron sensitivities and global thermal and mixed

  4. From Hubble's NGSL to Absolute Fluxes

    NASA Technical Reports Server (NTRS)

    Heap, Sara R.; Lindler, Don

    2012-01-01

    Hubble's Next Generation Spectral Library (NGSL) consists of R-l000 spectra of 374 stars of assorted temperature, gravity, and metallicity. Each spectrum covers the wavelength range, 0.18-1.00 microns. The library can be viewed and/or downloaded from the website, http://archive.stsci.edu/prepds/stisngsll. Stars in the NGSL are now being used as absolute flux standards at ground-based observatories. However, the uncertainty in the absolute flux is about 2%, which does not meet the requirements of dark-energy surveys. We are therefore developing an observing procedure that should yield fluxes with uncertainties less than 1 % and will take part in an HST proposal to observe up to 15 stars using this new procedure.

  5. NIST Calibration of a Neutron Spectrometer ROSPEC.

    PubMed

    Heimbach, Craig

    2006-01-01

    A neutron spectrometer was acquired for use in the measurement of National Institute of Standards and Technology neutron fields. The spectrometer included options for the measurement of low and high energy neutrons, for a total measurement range from 0.01 eV up to 17 MeV. The spectrometer was evaluated in calibration fields and was used to determine the neutron spectrum of an Americium-Beryllium neutron source. The calibration fields used included bare and moderated (252)Cf, monoenergetic neutron fields of 2.5 MeV and 14 MeV, and a thermal-neutron beam. Using the calibration values determined in this exercise, the spectrometer gives a good approximation of the neutron spectrum, and excellent values for neutron fluence, for all NIST calibration fields. The spectrometer also measured an Americium-Beryllium neutron field in a NIST exposure facility and determined the field quite well. The spectrometer measured scattering effects in neutron spectra which previously could be determined only by calculation or integral measurements.

  6. Absolute efficiency calibration of 6LiF-based solid state thermal neutron detectors

    NASA Astrophysics Data System (ADS)

    Finocchiaro, Paolo; Cosentino, Luigi; Lo Meo, Sergio; Nolte, Ralf; Radeck, Desiree

    2018-03-01

    The demand for new thermal neutron detectors as an alternative to 3He tubes in research, industrial, safety and homeland security applications, is growing. These needs have triggered research and development activities about new generations of thermal neutron detectors, characterized by reasonable efficiency and gamma rejection comparable to 3He tubes. In this paper we show the state of the art of a promising low-cost technique, based on commercial solid state silicon detectors coupled with thin neutron converter layers of 6LiF deposited onto carbon fiber substrates. A few configurations were studied with the GEANT4 simulation code, and the intrinsic efficiency of the corresponding detectors was calibrated at the PTB Thermal Neutron Calibration Facility. The results show that the measured intrinsic detection efficiency is well reproduced by the simulations, therefore validating the simulation tool in view of new designs. These neutron detectors have also been tested at neutron beam facilities like ISIS (Rutherford Appleton Laboratory, UK) and n_TOF (CERN) where a few samples are already in operation for beam flux and 2D profile measurements. Forthcoming applications are foreseen for the online monitoring of spent nuclear fuel casks in interim storage sites.

  7. OBJECT KINETIC MONTE CARLO SIMULATIONS OF RADIATION DAMAGE IN TUNGSTEN SUBJECTED TO NEUTRON FLUX WITH PKA SPECTRUM CORRESPONDING TO THE HFIR

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nandipati, Giridhar; Setyawan, Wahyu; Heinisch, Howard L.

    2015-12-31

    The objective of this work is to study the damage accumulation in pure tungsten (W) subjected to neutron bombardment with a primary knock-on atom (PKA) spectrum corresponding to the High Flux Isotope Reactor (HFIR), using the object kinetic Monte Carlo (OKMC) method.

  8. Development of An Epi-thermal Neutron Field for Fundamental Researches for BNCT with A DT Neutron Source

    NASA Astrophysics Data System (ADS)

    Osawa, Yuta; Imoto, Shoichi; Kusaka, Sachie; Sato, Fuminobu; Tanoshita, Masahiro; Murata, Isao

    2017-09-01

    Boron Neutron Capture Therapy (BNCT) is known to be a new promising cancer therapy suppressing influence against normal cells. In Japan, Accelerator Based Neutron Sources (ABNS) are being developed for BNCT. For the spread of ABNS based BNCT, we should characterize the neutron field beforehand. For this purpose, we have been developing a low-energy neutron spectrometer based on 3He position sensitive proportional counter. In this study, a new intense epi-thermal neutron field was developed with a DT neutron source for verification of validity of the spectrometer. After the development, the neutron field characteristics were experimentally evaluated by using activation foils. As a result, we confirmed that an epi-thermal neutron field was successfully developed suppressing fast neutrons substantially. Thereafter, the neutron spectrometer was verified experimentally. In the verification, although a measured detection depth distribution agreed well with the calculated distribution by MCNP, the unfolded spectrum was significantly different from the calculated neutron spectrum due to contribution of the side neutron incidence. Therefore, we designed a new neutron collimator consisting of a polyethylene pre-collimator and boron carbide neutron absorber and confirmed numerically that it could suppress the side incident neutrons and shape the neutron flux to be like a pencil beam.

  9. Deuterium-tritium neutron yield measurements with the 4.5 m neutron-time-of-flight detectors at NIF.

    PubMed

    Moran, M J; Bond, E J; Clancy, T J; Eckart, M J; Khater, H Y; Glebov, V Yu

    2012-10-01

    The first several campaigns of laser fusion experiments at the National Ignition Facility (NIF) included a family of high-sensitivity scintillator∕photodetector neutron-time-of-flight (nTOF) detectors for measuring deuterium-deuterium (DD) and DT neutron yields. The detectors provided consistent neutron yield (Y(n)) measurements from below 10(9) (DD) to nearly 10(15) (DT). The detectors initially demonstrated detector-to-detector Y(n) precisions better than 5%, but lacked in situ absolute calibrations. Recent experiments at NIF now have provided in situ DT yield calibration data that establish the absolute sensitivity of the 4.5 m differential tissue harmonic imaging (DTHI) detector with an accuracy of ± 10% and precision of ± 1%. The 4.5 m nTOF calibration measurements also have helped to establish improved detector impulse response functions and data analysis methods, which have contributed to improving the accuracy of the Y(n) measurements. These advances have also helped to extend the usefulness of nTOF measurements of ion temperature and downscattered neutron ratio (neutron yield 10-12 MeV divided by yield 13-15 MeV) with other nTOF detectors.

  10. 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.

  11. Non-destructive method for determining neutron exposure

    DOEpatents

    Gold, R.; McElroy, W.N.

    1983-11-01

    A non-destructive method for determination of neutron exposure in an object, such as a reactor pressure vessel, is based on the observation of characteristic gamma-rays emitted by activation products in the object by using a unique continuous gamma-ray spectrometer. The spectrometer views the object through appropriate collimators to determine the absolute emission rate of these characteristic gamma-rays, thereby ascertaining the absolute activity of given activation products in the object. These data can then be used to deduce the spatial and angular dependence of neutron exposure at regions of interest within the object.

  12. Evaluation of neutron skyshine from a cyclotron

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huyashi, K.; Nakamura, T.

    1984-06-01

    The dose distribution and the spectrum variation of neutrons due to the skyshine effect have been measured with various detectors in the environment surrounding the cyclotron of the Institute for Nuclear Study, University of Tokyo. The source neutrons were produced by stopping a 52-MeV proton beam into a carbon beam stopper and were extracted upward from the opening in the concrete shield surrounding the cyclotron and then leaked into the atmosphere through the cyclotron building. The dose distribution and the spectrum of neutrons near the beam stopper were also measured in order to get information on the skyshine source. Themore » measured skyshine neutron spectra and dose distribution were analyzed with two codes, MMCR2 and SKYSHINE-II, with the result that the calculated results are in good agreement with the experiment. Valuable characteristics of this experiment are the determination of the energy spectrum and dose distribution of source neutron and the measurement of skyshine neutrons from an actual large-scale accelerator building to the exclusion of direct neutrons transported through the air. This experiment must be useful as a kind of benchmark experiment on the skyshine phenomenon.« less

  13. Limiting rotational period of neutron stars

    NASA Astrophysics Data System (ADS)

    Glendenning, Norman K.

    1992-11-01

    We seek an absolute limit on the rotational period for a neutron star as a function of its mass, based on the minimal constraints imposed by Einstein's theory of relativity, Le Chatelier's principle, causality, and a low-density equation of state, uncertainties in which can be evaluated as to their effect on the result. This establishes a limiting curve in the mass-period plane below which no pulsar that is a neutron star can lie. For example, the minimum possible Kepler period, which is an absolute limit on rotation below which mass shedding would occur, is 0.33 ms for a M=1.442Msolar neutron star (the mass of PSR1913+16). A still lower curve, based only on the structure of Einstein's equations, limits any star whatsoever to lie in the plane above it. Hypothetical stars such as strange stars, if the matter of which they are made is self-bound in bulk at a sufficiently large equilibrium energy density, can lie in the region above the general-relativistic forbidden region, and in the region forbidden to neutron stars.

  14. Determination of the Spectral Index in the Fission Spectrum Energy Regime

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Amy Sarah

    2016-05-16

    Neutron reaction cross sections play a vital role in tracking the production and destruction of isotopes exposed to neutron fluence. They are central to the process of reconciling the initial and final atom inventories. Measurements of irradiated samples by radiochemical methods in tangent with an algorithm are used to evaluate the fluence a sample is exposed to over the course of the irradiation. This algorithm is the Isotope Production Code (IPC) created and used by the radiochemistry data assessment team at Los Alamos National Laboratory (LANL). An integral result is calculated by varying the total neutron fluence seen by amore » sample. A sample, irradiated in a critical assembly, will be exposed to a unique neutron flux defined by the neutron source and distance of the sample from the source. Neutron cross sections utilized are a function of the hardness of the neutron spectrum at the location of irradiation. A spectral index is used an indicator of the hardness of the neutron spectrum. Cross sections fit forms applied in IPC are collapsed from a LANL 30-group energy structure. Several decades of research and development have been performed to formalize the current IPC cross section library. Basis of the current fission spectrum neutron reaction cross section library is rooted in critical assembly experiments performed from the 1950’s through the early 1970’s at LANL. The focus of this report is development of the spectral index used an indicator of the hardness of the neutron spectrum in the fission spectrum energy regime.« less

  15. Novel neutron sources at the Radiological Research Accelerator Facility.

    PubMed

    Xu, Yanping; Garty, Guy; Marino, Stephen A; Massey, Thomas N; Randers-Pehrson, Gerhard; Johnson, Gary W; Brenner, David J

    2012-03-16

    Since the 1960s, the Radiological Research Accelerator Facility (RARAF) has been providing researchers in biology, chemistry and physics with advanced irradiation techniques, using charged particles, photons and neutrons.We are currently developing a unique facility at RARAF, to simulate neutron spectra from an improvised nuclear device (IND), based on calculations of the neutron spectrum at 1.5 km from the epicenter of the Hiroshima atom bomb. This is significantly different from a standard fission spectrum, because the spectrum changes as the neutrons are transported through air, and is dominated by neutron energies between 0.05 and 8 MeV. This facility will be based on a mixed proton/deuteron beam impinging on a thick beryllium target.A second, novel facility under development is our new neutron microbeam. The neutron microbeam will, for the first time, provide a kinematically collimated neutron beam, 10-20 micron in diameter. This facility is based on a Proton Microbeam, impinging on a thin lithium target near the threshold of the (7)Li(p,n)(7)Be reaction. This novel neutron microbeam will enable studies of neutron damage to small targets, such as single cells, individual organs within small animals or microelectronic components.

  16. Novel neutron sources at the Radiological Research Accelerator Facility

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Garty, G.; Marino, S. A.; Massey, T. N.; Randers-Pehrson, G.; Johnson, G. W.; Brenner, D. J.

    2012-03-01

    Since the 1960s, the Radiological Research Accelerator Facility (RARAF) has been providing researchers in biology, chemistry and physics with advanced irradiation techniques, using charged particles, photons and neutrons. We are currently developing a unique facility at RARAF, to simulate neutron spectra from an improvised nuclear device (IND), based on calculations of the neutron spectrum at 1.5 km from the epicenter of the Hiroshima atom bomb. This is significantly different from a standard fission spectrum, because the spectrum changes as the neutrons are transported through air, and is dominated by neutron energies between 0.05 and 8 MeV. This facility will be based on a mixed proton/deuteron beam impinging on a thick beryllium target. A second, novel facility under development is our new neutron microbeam. The neutron microbeam will, for the first time, provide a kinematically collimated neutron beam, 10-20 micron in diameter. This facility is based on a proton microbeam, impinging on a thin lithium target near the threshold of the 7Li(p,n)7Be reaction. This novel neutron microbeam will enable studies of neutron damage to small targets, such as single cells, individual organs within small animals or microelectronic components.

  17. Simulation of the neutron response matrix of an EJ309 liquid scintillator

    NASA Astrophysics Data System (ADS)

    Bai, Huaiyong; Wang, Zhimin; Zhang, Luyu; Jiang, Haoyu; Lu, Yi; Chen, Jinxiang; Zhang, Guohui

    2018-04-01

    The neutron response matrix is the basis for measuring the neutron energy spectrum through unfolding the pulse height spectrum detected with a liquid scintillator. Based on the light output of the EJ309 liquid scintillator and the related reaction cross sections, a Monte Carlo code is developed to obtain the neutron response matrix. The effects of the related reactions, the contributions of different number of neutron interactions and the wall effect of the recoil proton are discussed. With the obtained neutron response matrix and the GRAVEL iterative unfolding method, the neutron energy spectra of the 252Cf and the 241AmBe neutron sources are measured, and the results are respectively compared with the theoretical prediction of the 252Cf neutron energy spectrum and the previous results of the 241AmBe neutron energy spectra.

  18. Solid-state track recorder dosimetry device to measure absolute reaction rates and neutron fluence as a function of time

    DOEpatents

    Gold, Raymond; Roberts, James H.

    1989-01-01

    A solid state track recording type dosimeter is disclosed to measure the time dependence of the absolute fission rates of nuclides or neutron fluence over a period of time. In a primary species an inner recording drum is rotatably contained within an exterior housing drum that defines a series of collimating slit apertures overlying windows defined in the stationary drum through which radiation can enter. Film type solid state track recorders are positioned circumferentially about the surface of the internal recording drum to record such radiation or its secondary products during relative rotation of the two elements. In another species both the recording element and the aperture element assume the configuration of adjacent disks. Based on slit size of apertures and relative rotational velocity of the inner drum, radiation parameters within a test area may be measured as a function of time and spectra deduced therefrom.

  19. COMPTEL neutron response at 17 MeV

    NASA Technical Reports Server (NTRS)

    Oneill, Terrence J.; Ait-Ouamer, Farid; Morris, Joann; Tumer, O. Tumay; White, R. Stephen; Zych, Allen D.

    1992-01-01

    The Compton imaging telescope (COMPTEL) instrument of the Gamma Ray Observatory was exposed to 17 MeV d,t neutrons prior to launch. These data were analyzed and compared with Monte Carlo calculations using the MCNP(LANL) code. Energy and angular resolutions are compared and absolute efficiencies are calculated at 0 and 30 degrees incident angle. The COMPTEL neutron responses at 17 MeV and higher energies are needed to understand solar flare neutron data.

  20. Source Correlated Prompt Neutron Activation Analysis for Material Identification and Localization

    NASA Astrophysics Data System (ADS)

    Canion, Bonnie; McConchie, Seth; Landsberger, Sheldon

    2017-07-01

    This paper investigates the energy spectrum of photon signatures from an associated particle imaging deuterium tritium (API-DT) neutron generator interrogating shielded uranium. The goal is to investigate if signatures within the energy spectrum could be used to indirectly characterize shielded uranium when the neutron signature is attenuated. By utilizing the correlated neutron cone associated with each pixel of the API-DT neutron generator, certain materials can be identified and located via source correlated spectrometry of prompt neutron activation gamma rays. An investigation is done to determine if fission neutrons induce a significant enough signature within the prompt neutron-induced gamma-ray energy spectrum in shielding material to be useful for indirect nuclear material characterization. The signature deriving from the induced fission neutrons interacting with the shielding material was slightly elevated in polyethylene-shielding depleted uranium (DU), but was more evident in some characteristic peaks from the aluminum shielding surrounding DU.

  1. The possible use of a spallation neutron source for neutron capture therapy with epithermal neutrons.

    PubMed

    Grusell, E; Condé, H; Larsson, B; Rönnqvist, T; Sornsuntisook, O; Crawford, J; Reist, H; Dahl, B; Sjöstrand, N G; Russel, G

    1990-01-01

    Spallation is induced in a heavy material by 72-MeV protons. The resulting neutrons can be characterized by an evaporation spectrum with a peak energy of less than 2 MeV. The neutrons are moderated in two steps: first in iron and then in carbon. Results from neutron fluence measurements in a perspex phantom placed close to the moderator are presented. Monte Carlo calculations of neutron fluence in a water phantom are also presented under some chosen configurations of spallation source and moderator. The calculations and measurements are in good agreement and show that, for proton currents of less than 0.5 mA, useful thermal-neutron fluences are attainable in the depth of the brain. However, the dose contribution from the unavoidable gamma background component has not been included in the present investigation.

  2. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

    DOE PAGES

    Frenje, J. A.; Hilsabeck, T. J.; Wink, C. W.; ...

    2016-08-02

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T i), yield (Y n), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate datamore » with a time resolution of ~20 ps and energy resolution of ~100 keV for total neutron yields above ~10 16. Lastly, at lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ~20 ps.« less

  3. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF).

    PubMed

    Frenje, J A; Hilsabeck, T J; Wink, C W; Bell, P; Bionta, R; Cerjan, C; Gatu Johnson, M; Kilkenny, J D; Li, C K; Séguin, F H; Petrasso, R D

    2016-11-01

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T i ), yield (Y n ), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate data with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼10 16 . At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.

  4. The magnetic recoil spectrometer (MRSt) for time-resolved measurements of the neutron spectrum at the National Ignition Facility (NIF)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Frenje, J. A., E-mail: jfrenje@psfc.mit.edu; Wink, C. W.; Gatu Johnson, M.

    The next-generation magnetic recoil spectrometer for time-resolved measurements of the neutron spectrum has been conceptually designed for the National Ignition Facility. This spectrometer, called MRSt, represents a paradigm shift in our thinking about neutron spectrometry for inertial confinement fusion applications, as it will provide simultaneously information about the burn history and time evolution of areal density (ρR), apparent ion temperature (T{sub i}), yield (Y{sub n}), and macroscopic flows during burn. From this type of data, an assessment of the evolution of the fuel assembly, hotspot, and alpha heating can be made. According to simulations, the MRSt will provide accurate datamore » with a time resolution of ∼20 ps and energy resolution of ∼100 keV for total neutron yields above ∼10{sup 16}. At lower yields, the diagnostic will be operated at a higher-efficiency, lower-energy-resolution mode to provide a time resolution of ∼20 ps.« less

  5. Novel neutron sources at the Radiological Research Accelerator Facility

    PubMed Central

    Xu, Yanping; Garty, Guy; Marino, Stephen A.; Massey, Thomas N.; Randers-Pehrson, Gerhard; Johnson, Gary W.; Brenner, David J.

    2012-01-01

    Since the 1960s, the Radiological Research Accelerator Facility (RARAF) has been providing researchers in biology, chemistry and physics with advanced irradiation techniques, using charged particles, photons and neutrons. We are currently developing a unique facility at RARAF, to simulate neutron spectra from an improvised nuclear device (IND), based on calculations of the neutron spectrum at 1.5 km from the epicenter of the Hiroshima atom bomb. This is significantly different from a standard fission spectrum, because the spectrum changes as the neutrons are transported through air, and is dominated by neutron energies between 0.05 and 8 MeV. This facility will be based on a mixed proton/deuteron beam impinging on a thick beryllium target. A second, novel facility under development is our new neutron microbeam. The neutron microbeam will, for the first time, provide a kinematically collimated neutron beam, 10–20 micron in diameter. This facility is based on a Proton Microbeam, impinging on a thin lithium target near the threshold of the 7Li(p,n)7Be reaction. This novel neutron microbeam will enable studies of neutron damage to small targets, such as single cells, individual organs within small animals or microelectronic components. PMID:22545061

  6. Novel neutron sources at the Radiological Research Accelerator Facility

    DOE PAGES

    Xu, Yanping; Garty, G.; Marino, S. A.; ...

    2012-03-16

    Since the 1960s, the Radiological Research Accelerator Facility (RARAF) has been providing researchers in biology, chemistry and physics with advanced irradiation techniques, using charged particles, photons and neutrons. We are currently developing a unique facility at RARAF, to simulate neutron spectra from an improvised nuclear device (IND), based on calculations of the neutron spectrum at 1.5 km from the epicenter of the Hiroshima atom bomb. This is significantly different from a standard fission spectrum, because the spectrum changes as the neutrons are transported through air, and is dominated by neutron energies between 0.05 and 8 MeV. This facility will bemore » based on a mixed proton/deuteron beam impinging on a thick beryllium target. A second, novel facility under development is our new neutron microbeam. The neutron microbeam will, for the first time, provide a kinematically collimated neutron beam, 10-20 micron in diameter. This facility is based on a proton microbeam, impinging on a thin lithium target near the threshold of the Li-7(p,n)Be-7 reaction. Lastly, this novel neutron microbeam will enable studies of neutron damage to small targets, such as single cells, individual organs within small animals or microelectronic components.« less

  7. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    DOE PAGES

    Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen; ...

    2016-10-17

    In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states weremore » studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.« less

  8. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    NASA Astrophysics Data System (ADS)

    Fotiades, N.; Devlin, M.; Nelson, R. O.; Kawano, T.; Carroll, J. J.

    2016-10-01

    Background: In (n ,n' ) reactions on stable Ir and Au isotopes in the mass A =190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n ,2 n ) reaction channel opens up, and then decreases. Purpose: In order to check for similar behavior in the mass A =100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Methods: Excited states were studied using the (n ,n'γ ), (n ,2 n γ ), and (n ,3 n γ ) reactions on 103Rh and 109Ag. A germanium detector array for γ -ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Results: Absolute partial γ -ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. Conclusions: The opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A =190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.

  9. Feeding of Rh and Ag isomers in fast-neutron-induced reactions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Fotiades, Nikolaos; Devlin, Matthew James; Nelson, Ronald Owen

    In (n,n') reactions on stable Ir and Au isotopes in the mass A=190 region, the experimentally established feeding of the isomers relative to the feeding of the corresponding ground states increases with increasing neutron energy, up to the neutron energy where the (n,2n) reaction channel opens up, and then decreases. In order to check for similar behavior in the mass A=100 region, the feeding of isomers and ground states in fast-neutron-induced reactions on stable isotopes in this mass region was studied. This is of especial interest for Rh which can be used as a radiochemical detector. Here, excited states weremore » studied using the (n,n'γ), (n,2nγ), and (n,3nγ) reactions on 103Rh and 109Ag. A germanium detector array for γ-ray detection and the broad-spectrum pulsed neutron source of the Los Alamos Neutron Science Center's Weapons Neutron Research facility were used for the measurement. The energy of the incident neutrons was determined using the time-of-flight technique. Absolute partial γ-ray cross sections were measured for 57 transitions feeding isomers and ground states in 101,102,103Rh and 107,108,109Ag. The feeding of the isomers was found to be very similar in the corresponding reaction channels and it is compared to the feeding determined for the ground states. In conclusion, the opening of reaction channels at higher neutron energies removes angular momentum from the residual nucleus and reduces the population of the higher-spin isomers relative to the feeding of the lower-spin ground states. Similar behavior was observed in the mass A=190 region in the feeding of higher-spin isomers, but the reverse behavior was observed in 176Lu with a lower-spin isomer and a higher-spin ground state.« less

  10. Two detector arrays for fast neutrons at LANSCE

    NASA Astrophysics Data System (ADS)

    Haight, R. C.; Lee, H. Y.; Taddeucci, T. N.; O'Donnell, J. M.; Perdue, B. A.; Fotiades, N.; Devlin, M.; Ullmann, J. L.; Laptev, A.; Bredeweg, T.; Jandel, M.; Nelson, R. O.; Wender, S. A.; White, M. C.; Wu, C. Y.; Kwan, E.; Chyzh, A.; Henderson, R.; Gostic, J.

    2012-03-01

    The neutron spectrum from neutron-induced fission needs to be known in designing new fast reactors, predicting criticality for safety analyses, and developing techniques for global security application. The experimental data base of fission neutron spectra is very incomplete and most present evaluated libraries are based on the approach of the Los Alamos Model. To validate these models and to provide improved data for applications, a program is underway to measure the fission neutron spectrum for a wide range of incident neutron energies using the spallation source of fast neutrons at the Weapons Neutron Research (WNR) facility at the Los Alamos Neutron Science Center (LANSCE). In a double time-of-flight experiment, fission neutrons are detected by arrays of neutron detectors to increase the solid angle and also to investigate possible angular dependence of the fission neutrons. The challenge is to measure the spectrum from low energies, down to 100 keV or so, to energies over 10 MeV, where the evaporation-like spectrum decreases by 3 orders of magnitude from its peak around 1 MeV. For these measurements, we are developing two arrays of neutron detectors, one based on liquid organic scintillators and the other on 6Li-glass detectors. The range of fission neutrons detected by organic liquid scintillators extends from about 600 keV to well over 10 MeV, with the lower limit being defined by the limit of pulse-shape discrimination. The 6Li-glass detectors have a range from very low energies to about 1 MeV, where their efficiency then becomes small. Various considerations and tests are in progress to understand important contributing factors in designing these two arrays and they include selection and characterization of photomultiplier tubes (PM), the performance of relatively thin (1.8 cm) 6Li-glass scintillators on 12.5 cm diameter PM tubes, use of 17.5 cm diameter liquid scintillators with 12.5 cm PM tubes, measurements of detector efficiencies with tagged neutrons

  11. Design and spectrum calculation of 4H-SiC thermal neutron detectors using FLUKA and TCAD

    NASA Astrophysics Data System (ADS)

    Huang, Haili; Tang, Xiaoyan; Guo, Hui; Zhang, Yimen; Zhang, Yimeng; Zhang, Yuming

    2016-10-01

    SiC is a promising material for neutron detection in a harsh environment due to its wide band gap, high displacement threshold energy and high thermal conductivity. To increase the detection efficiency of SiC, a converter such as 6LiF or 10B is introduced. In this paper, pulse-height spectra of a PIN diode with a 6LiF conversion layer exposed to thermal neutrons (0.026 eV) are calculated using TCAD and Monte Carlo simulations. First, the conversion efficiency of a thermal neutron with respect to the thickness of 6LiF was calculated by using a FLUKA code, and a maximal efficiency of approximately 5% was achieved. Next, the energy distributions of both 3H and α induced by the 6LiF reaction according to different ranges of emission angle are analyzed. Subsequently, transient pulses generated by the bombardment of single 3H or α-particles are calculated. Finally, pulse height spectra are obtained with a detector efficiency of 4.53%. Comparisons of the simulated result with the experimental data are also presented, and the calculated spectrum shows an acceptable similarity to the experimental data. This work would be useful for radiation-sensing applications, especially for SiC detector design.

  12. NSDann2BS, a neutron spectrum unfolding code based on neural networks technology and two bonner spheres

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ortiz-Rodriguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.

    In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called ''Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres'', (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the ''Robust design of artificial neural networks methodology'' and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored atmore » synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of {sup 252}Cf, {sup 241}AmBe and {sup 239}PuBe neutron sources measured with a Bonner spheres system.« less

  13. NSDann2BS, a neutron spectrum unfolding code based on neural networks technology and two bonner spheres

    NASA Astrophysics Data System (ADS)

    Ortiz-Rodríguez, J. M.; Reyes Alfaro, A.; Reyes Haro, A.; Solís Sánches, L. O.; Miranda, R. Castañeda; Cervantes Viramontes, J. M.; Vega-Carrillo, H. R.

    2013-07-01

    In this work a neutron spectrum unfolding code, based on artificial intelligence technology is presented. The code called "Neutron Spectrometry and Dosimetry with Artificial Neural Networks and two Bonner spheres", (NSDann2BS), was designed in a graphical user interface under the LabVIEW programming environment. The main features of this code are to use an embedded artificial neural network architecture optimized with the "Robust design of artificial neural networks methodology" and to use two Bonner spheres as the only piece of information. In order to build the code here presented, once the net topology was optimized and properly trained, knowledge stored at synaptic weights was extracted and using a graphical framework build on the LabVIEW programming environment, the NSDann2BS code was designed. This code is friendly, intuitive and easy to use for the end user. The code is freely available upon request to authors. To demonstrate the use of the neural net embedded in the NSDann2BS code, the rate counts of 252Cf, 241AmBe and 239PuBe neutron sources measured with a Bonner spheres system.

  14. Inelastic neutron scattering spectrum of cyclotrimethylenetrinitramine: a comparison with solid-state electronic structure calculations.

    PubMed

    Ciezak, Jennifer A; Trevino, S F

    2006-04-20

    Solid-state geometry optimizations and corresponding normal-mode analysis of the widely used energetic material cyclotrimethylenetrinitramine (RDX) were performed using density functional theory with both the generalized gradient approximation (BLYP and BP functionals) and the local density approximation (PWC and VWN functionals). The structural results were found to be in good agreement with experimental neutron diffraction data and previously reported calculations based on the isolated-molecule approximation. The vibrational inelastic neutron scattering (INS) spectrum of polycrystalline RDX was measured and compared with simulated INS constructed from the solid-state calculations. The vibrational frequencies calculated from the solid-state methods had average deviations of 10 cm(-1) or less, whereas previously published frequencies based on an isolated-molecule approximation had deviations of 65 cm(-1) or less, illustrating the importance of including crystalline forces. On the basis of the calculations and analysis, it was possible to assign the normal modes and symmetries, which agree well with previous assignments. Four possible "doorway modes" were found in the energy range defined by the lattice modes, which were all found to contain fundamental contributions from rotation of the nitro groups.

  15. Measurements of the neutron dose and energy spectrum on the International Space Station during expeditions ISS-16 to ISS-21.

    PubMed

    Smith, M B; Akatov, Yu; Andrews, H R; Arkhangelsky, V; Chernykh, I V; Ing, H; Khoshooniy, N; Lewis, B J; Machrafi, R; Nikolaev, I; Romanenko, R Y; Shurshakov, V; Thirsk, R B; Tomi, L

    2013-01-01

    As part of the international Matroshka-R and Radi-N experiments, bubble detectors have been used on board the ISS in order to characterise the neutron dose and the energy spectrum of neutrons. Experiments using bubble dosemeters inside a tissue-equivalent phantom were performed during the ISS-16, ISS-18 and ISS-19 expeditions. During the ISS-20 and ISS-21 missions, the bubble dosemeters were supplemented by a bubble-detector spectrometer, a set of six detectors that was used to determine the neutron energy spectrum at various locations inside the ISS. The temperature-compensated spectrometer set used is the first to be developed specifically for space applications and its development is described in this paper. Results of the dose measurements indicate that the dose received at two different depths inside the phantom is not significantly different, suggesting that bubble detectors worn by a person provide an accurate reading of the dose received inside the body. The energy spectra measured using the spectrometer are in good agreement with previous measurements and do not show a strong dependence on the precise location inside the station. To aid the understanding of the bubble-detector response to charged particles in the space environment, calculations have been performed using a Monte-Carlo code, together with data collected on the ISS. These calculations indicate that charged particles contribute <2% to the bubble count on the ISS, and can therefore be considered as negligible for bubble-detector measurements in space.

  16. Interpretation of the COBE FIRAS CMBR spectrum

    NASA Technical Reports Server (NTRS)

    Wright, E. L.; Mather, J. C.; Fixsen, D. J.; Kogut, A.; Shafer, R. A.; Bennett, C. L.; Boggess, N. W.; Cheng, E. S.; Silverberg, R. F.; Smoot, G. F.

    1994-01-01

    The cosmic microwave background radiation (CMBR) spectrum measured by the Far-Infrared Absolute Spectrophotometer (FIRAS) instrument on NASA's Cosmic Background Explorer (COBE) is indistinguishable from a blackbody, implying stringent limits on energy release in the early universe later than the time t = 1 yr after the big bang. We compare the FIRAS data to previous precise measurements of the cosmic microwave background spectrum and find a reasonable agreement. We discuss the implications of the absolute value of y is less than 2.5 x 10(exp -5) and the absolute value of mu is less than 3.3 x 10(exp -4) 95% confidence limits found by Mather et al. (1994) on many processes occurring after t = 1 yr, such as explosive structure formation, reionization, and dissipation of small-scale density perturbations. We place limits on models with dust plus Population III stars, or evolving populations of IR galaxies, by directly comparing the Mather et al. spectrum to the model predictions.

  17. α and 2 p 2 n emission in fast neutron-induced reactions on 60Ni

    NASA Astrophysics Data System (ADS)

    Fotiades, N.; Devlin, M.; Haight, R. C.; Nelson, R. O.; Kunieda, S.; Kawano, T.

    2015-06-01

    Background: The cross sections for populating the residual nucleus in the reaction ZAX(n,x) Z -2 A -4Y exhibit peaks as a function of incident neutron energy corresponding to the (n ,n'α ) reaction and, at higher energy, to the (n ,2 p 3 n ) reaction. The relative magnitudes of these peaks vary with the Z of the target nucleus. Purpose: Study fast neutron-induced reactions on 60Ni. Locate experimentally the nuclear charge region along the line of stability where the cross sections for α emission and for 2 p 2 n emission in fast neutron-induced reactions are comparable as a further test of reaction models. Methods: Data were taken by using the Germanium Array for Neutron-Induced Excitations. The broad-spectrum pulsed neutron beam of the Los Alamos Neutron Science Center's Weapons Neutron Research facility provided neutrons in the energy range from 1 to 250 MeV. The time-of-flight technique was used to determine the incident-neutron energies. Results: Absolute partial cross sections for production of seven discrete Fe γ rays populated in 60Ni (n ,α /2 p x n γ ) reactions with 2 ≤x ≤5 were measured for neutron energies 1 MeVneutron energies while discrepancies appear at higher neutron energies. The cross section for producing an isotope in fast neutron-induced reactions on stable targets via α emission at the peak of the (n ,α ) and (n ,n'α ) reactions is comparable to that for 2 p 2 n and 2 p 3 n emission at higher incident energies in the nuclear charge region around Fe.

  18. Neutron flux measurements around PLT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zankl, G.; Strachan, J.D.; Lewis, R.

    1980-09-01

    Using Indium activation foils, the toroidal and poloidal neutron emission patterns were determined for PLT plasmas which include ICRF and neutral beam heating. The activities produced the /sup 115/In (n,n') /sup 115m/In reaction were determined by counting the 336 keV ..gamma.. line of the /sup 115m/In decay. This activation cross section falls just below 2.5 MeV so that the influence of scattered neutrons of degraded energies is reduced. From the magnitude of the activity, the absolute calibration of the PLT fusion neutron emission is obtained with less than or equal to 40% accuracy.

  19. The spectrum of neutrons at 60 hg m(-2)

    NASA Technical Reports Server (NTRS)

    Barton, J. C.

    1985-01-01

    The rate of neutron interactions was measured for the energy range 7.5 to 60 MeV, using a 3.85 kg cell of liquid scintillator. The neutrons are selected by pulse shape discrimination, with anticoincidence counters used to reduce interference from muons transversing the scintillator. The observed flux is interpreted in terms of neutrons produced from environmental uranium and thorium, those resulting from the capture of negative muons in nuclei and those from fast muon interactions.

  20. Application of Advanced Nuclear Emulsion Technique to Fusion Neutron Diagnostics

    NASA Astrophysics Data System (ADS)

    Nakayama, Y.; Tomita, H.; Morishima, K.; Yamashita, F.; Hayashi, S.; Cheon, MunSeong; Isobe, M.; Ogawa, K.; Naka, T.; Nakano, T.; Nakamura, M.; Kawarabayashi, J.; Iguchi, T.; Ochiai, K.

    In order to measure the 2.5 MeV neutrons produced by DD nuclear fusion reactions, we have developed a compact neutron detector based on nuclear emulsion. After optimization of development conditions, we evaluated the response of the detector to an accelerator-based DD neutron source. The absolute efficiency at an energy of 2.5 MeV was estimated to be (4.1±0.2)×10-6 tracks/neutron.

  1. Validation of absolute axial neutron flux distribution calculations with MCNP with 197Au(n,γ)198Au reaction rate distribution measurements at the JSI TRIGA Mark II reactor.

    PubMed

    Radulović, Vladimir; Štancar, Žiga; Snoj, Luka; Trkov, Andrej

    2014-02-01

    The calculation of axial neutron flux distributions with the MCNP code at the JSI TRIGA Mark II reactor has been validated with experimental measurements of the (197)Au(n,γ)(198)Au reaction rate. The calculated absolute reaction rate values, scaled according to the reactor power and corrected for the flux redistribution effect, are in good agreement with the experimental results. The effect of different cross-section libraries on the calculations has been investigated and shown to be minor. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Preliminary Analysis of the Multisphere Neutron Spectrometer

    NASA Technical Reports Server (NTRS)

    Goldhagen, P.; Kniss, T.; Wilson, J. W.; Singleterry, R. C.; Jones, I. W.; VanSteveninck, W.

    2003-01-01

    Crews working on present-day jet aircraft are a large occupationally exposed group with a relatively high average effective dose from galactic cosmic radiation. Crews of future high-speed commercial aircraft flying at higher altitudes would be even more exposed. To help reduce the significant uncertainties in calculations of such exposures, the Atmospheric Ionizing Radiation (AIR) Project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on five flights of a NASA ER-2 high-altitude aircraft. The primary AIR instrument was a highly sensitive extended-energy multisphere neutron spectrometer with lead and steel shells placed within the moderators of two of its 14 detectors to enhance response at high energies. Detector responses were calculated for neutrons and charged hadrons at energies up to 100 GeV using MCNPX. Neutron spectra were unfolded from the measured count rates using the new MAXED code. We have measured the cosmic-ray neutron spectrum (thermal to greater than 10 GeV), total neutron fluence rate, and neutron effective dose and dose equivalent rates and their dependence on altitude and geomagnetic cutoff. The measured cosmic-ray neutron spectra have almost no thermal neutrons, a large "evaporation" peak near 1 MeV and a second broad peak near 100 MeV which contributes about 69% of the neutron effective dose. At high altitude, geomagnetic latitude has very little effect on the shape of the spectrum, but it is the dominant variable affecting neutron fluence rate, which was 8 times higher at the northernmost measurement location than it was at the southernmost. The shape of the spectrum varied only slightly with altitude from 21 km down to 12 km (56 - 201 grams per square centimeter atmospheric depth), but was significantly different on the ground. In all cases, ambient dose equivalent was greater than effective dose for cosmic-ray neutrons.

  3. Measurement of the Am 242 m neutron-induced reaction cross sections

    DOE PAGES

    Buckner, M. Q.; Wu, C. Y.; Henderson, R. A.; ...

    2017-02-17

    The neutron-induced reaction cross sections of 242mAm were measured at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array along with a compact parallel-plate avalanche counter for fission-fragment detection. A new neutron-capture cross section was determined, and the absolute scale was set according to a concurrent measurement of the well-known 242mAm(n,f) cross section. The (n,γ) cross section was measured from thermal energy to an incident energy of 1 eV at which point the data quality was limited by the reaction yield in the laboratory. Our new 242mAm fission cross section was normalized to ENDF/B-VII.1 tomore » set the absolute scale, and it agreed well with the (n,f) cross section from thermal energy to 1 keV. Lastly, the average absolute capture-to-fission ratio was determined from thermal energy to E n = 0.1 eV, and it was found to be 26(4)% as opposed to the ratio of 19% from the ENDF/B-VII.1 evaluation.« less

  4. A Comparison of Fast-Spectrum and Moderated Space Fission Reactors

    NASA Astrophysics Data System (ADS)

    Poston, David I.

    2005-02-01

    The reactor neutron spectrum is one of the fundamental design choices for any fission reactor, but the implications of using a moderated spectrum are vastly different for space reactors as opposed to terrestrial reactors. In addition, the pros and cons of neutron spectra are significantly different among many of the envisioned space power applications. This paper begins with a discussion of the neutronic differences between fast-spectrum and moderated space reactors. This is followed by a discussion of the pros and cons of fast-spectrum and moderated space reactors separated into three areas—technical risk, performance, and safety/safeguards. A mix of quantitative and qualitative arguments is presented, and some conclusions generally can be made regarding neutron spectrum and space power application. In most cases, a fast-spectrum system appears to be the better alternative (mostly because of simplicity and higher potential operating temperatures); however, in some cases, such as a low-power (<100-kWt) surface reactor, a moderated spectrum could provide a better approach. In all cases, the determination of which spectrum is preferred is a strong function of the metrics provided by the "customer"— i.e., if a certain level of performance is required, it could provide a different solution than if a certain level of safeguards is required (which in some cases could produce a null solution). The views expressed in this document are those of the author and do not necessarily reflect agreement by the Government.

  5. Evaluation of the 235U prompt fission neutron spectrum including a detailed analysis of experimental data and improved model information

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Neudecker, Denise; Talou, Patrick; Kahler, Albert Comstock III

    We present an evaluation of the 235U prompt fission neutron spectrum (PFNS) induced by thermal to 20-MeV neutrons. Experimental data and associated covariances were analyzed in detail. The incident energy dependence of the PFNS was modeled with an extended Los Alamos model combined with the Hauser-Feshbach and the exciton models. These models describe prompt fission, pre-fission compound nucleus and pre-equilibrium neutron emissions. The evaluated PFNS agree well with the experimental data included in this evaluation, preliminary data of the LANL and LLNL Chi-Nu measurement and recent evaluations by Capote et al. and Rising et al. However, they are softer thanmore » the ENDF/B-VII.1 (VII.1) and JENDL-4.0 PFNS for incident neutron energies up to 2 MeV. Simulated effective multiplication factors k eff of the Godiva and Flattop-25 critical assemblies are further from the measured k eff if the current data are used within VII.1 compared to using only VII.1 data. However, if this work is used with ENDF/B-VIII.0β2 data, simulated values of k eff agree well with the measured ones.« less

  6. Evaluation of the 235U prompt fission neutron spectrum including a detailed analysis of experimental data and improved model information

    DOE PAGES

    Neudecker, Denise; Talou, Patrick; Kahler, Albert Comstock III; ...

    2017-09-13

    We present an evaluation of the 235U prompt fission neutron spectrum (PFNS) induced by thermal to 20-MeV neutrons. Experimental data and associated covariances were analyzed in detail. The incident energy dependence of the PFNS was modeled with an extended Los Alamos model combined with the Hauser-Feshbach and the exciton models. These models describe prompt fission, pre-fission compound nucleus and pre-equilibrium neutron emissions. The evaluated PFNS agree well with the experimental data included in this evaluation, preliminary data of the LANL and LLNL Chi-Nu measurement and recent evaluations by Capote et al. and Rising et al. However, they are softer thanmore » the ENDF/B-VII.1 (VII.1) and JENDL-4.0 PFNS for incident neutron energies up to 2 MeV. Simulated effective multiplication factors k eff of the Godiva and Flattop-25 critical assemblies are further from the measured k eff if the current data are used within VII.1 compared to using only VII.1 data. However, if this work is used with ENDF/B-VIII.0β2 data, simulated values of k eff agree well with the measured ones.« less

  7. Evaluation of the 235U prompt fission neutron spectrum including a detailed analysis of experimental data and improved model information

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    We present an evaluation of the 235U prompt fission neutron spectrum (PFNS) induced by thermal to 20-MeV neutrons. Experimental data and associated covariances were analyzed in detail. The incident energy dependence of the PFNS was modeled with an extended Los Alamos model combined with the Hauser-Feshbach and the exciton models. These models describe prompt fission, pre-fission compound nucleus and pre-equilibrium neutron emissions. The evaluated PFNS agree well with the experimental data included in this evaluation, preliminary data of the LANL and LLNL Chi-Nu measurement and recent evaluations by Capote et al. and Rising et al. However, they are softer than the ENDF/B-VII.1 (VII.1) and JENDL-4.0 PFNS for incident neutron energies up to 2 MeV. Simulated effective multiplication factors keff of the Godiva and Flattop-25 critical assemblies are further from the measured keff if the current data are used within VII.1 compared to using only VII.1 data. However, if this work is used with ENDF/B-VIII.0β2 data, simulated values of keff agree well with the measured ones.

  8. The Absolute Magnitude of the Sun in Several Filters

    NASA Astrophysics Data System (ADS)

    Willmer, Christopher N. A.

    2018-06-01

    This paper presents a table with estimates of the absolute magnitude of the Sun and the conversions from vegamag to the AB and ST systems for several wide-band filters used in ground-based and space-based observatories. These estimates use the dustless spectral energy distribution (SED) of Vega, calibrated absolutely using the SED of Sirius, to set the vegamag zero-points and a composite spectrum of the Sun that coadds space-based observations from the ultraviolet to the near-infrared with models of the Solar atmosphere. The uncertainty of the absolute magnitudes is estimated by comparing the synthetic colors with photometric measurements of solar analogs and is found to be ∼0.02 mag. Combined with the uncertainty of ∼2% in the calibration of the Vega SED, the errors of these absolute magnitudes are ∼3%–4%. Using these SEDs, for three of the most utilized filters in extragalactic work the estimated absolute magnitudes of the Sun are M B = 5.44, M V = 4.81, and M K = 3.27 mag in the vegamag system and M B = 5.31, M V = 4.80, and M K = 5.08 mag in AB.

  9. Prompt fission neutron multiplicity and spectrum model for 30-80 MeV neutrons incident on 238U

    NASA Astrophysics Data System (ADS)

    Tudora, Anabella; Vladuca, G.; Morillon, B.

    2004-08-01

    The improved Los Alamos model is developed for the first time in order to provide prompt fission neutron multiplicity, prompt fission neutron spectra and other quantities at high incident neutron energies where the fission of secondary compound nuclei formed by charged particle emission occurs. In this model (exemplified by the n+ 238U reaction up to 80 MeV incident energy) the fission of the secondary nuclei formed by proton emission, neutron evaporation from the nuclei formed by proton emission, deuteron emission, alpha emission and neutron evaporation from the nuclei formed by alpha emission is taken into account. Input model parameters and related excitation energy dependences are determined using available experimental information and systematics as well as total and partial neutron induced fission cross-sections and their ratios obtained separately from a recent evaluation performed up to medium energies. Our present model predictions are in good agreement with the measured prompt neutron spectra and multiplicities.

  10. Calculations to support JET neutron yield calibration: Modelling of neutron emission from a compact DT neutron generator

    NASA Astrophysics Data System (ADS)

    Čufar, Aljaž; Batistoni, Paola; Conroy, Sean; Ghani, Zamir; Lengar, Igor; Milocco, Alberto; Packer, Lee; Pillon, Mario; Popovichev, Sergey; Snoj, Luka; JET Contributors

    2017-03-01

    At the Joint European Torus (JET) the ex-vessel fission chambers and in-vessel activation detectors are used as the neutron production rate and neutron yield monitors respectively. In order to ensure that these detectors produce accurate measurements they need to be experimentally calibrated. A new calibration of neutron detectors to 14 MeV neutrons, resulting from deuterium-tritium (DT) plasmas, is planned at JET using a compact accelerator based neutron generator (NG) in which a D/T beam impinges on a solid target containing T/D, producing neutrons by DT fusion reactions. This paper presents the analysis that was performed to model the neutron source characteristics in terms of energy spectrum, angle-energy distribution and the effect of the neutron generator geometry. Different codes capable of simulating the accelerator based DT neutron sources are compared and sensitivities to uncertainties in the generator's internal structure analysed. The analysis was performed to support preparation to the experimental measurements performed to characterize the NG as a calibration source. Further extensive neutronics analyses, performed with this model of the NG, will be needed to support the neutron calibration experiments and take into account various differences between the calibration experiment and experiments using the plasma as a source of neutrons.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Barnes, C.W.

    1997-01-01

    The DT program at the Tokamak Fusion Test Reactor (TFTR) created requirements on 14 MeV neutron measurements to measure from 10{sup 6} n/cm{sup 2} (for triton burnup and Ohmic tritium plasmas) to {gt}10{sup 12} n/cm{sup 2} (characteristic of {gt}10 MW DT plasmas) with an accuracy of 7% (one-sigma).1 To maintain an absolute calibration over this dynamic range with active neutron detectors required one to go from some absolute standard at one fluence level to a measurement at a much higher fluence. Maintaining accuracy requires an extremely linear set of measurements not systematically affected over this dynamic range. Neutron activation canmore » provide such linearity when care is taken with a number of effects such as gamma-ray detection efficiency and sample contamination.2 Absolutely calibrated neutron yield measurements using dosimetric (well-known cross section) reactions with thin (low-mass) elemental foils is be described. This technique makes the detector comparison to an absolute standard of gamma-ray activity correspond to all neutron fluences by reducing the sample mass while keeping the activation detectors operating in a linear counting mode; i.e., low count rates which minimize pileup effects. The International Thermonuclear Experimental Reactor is projected to have 1000 s burn durations at fluxes of few 10{sup 13} n/cm{sup 2}s, or more neutron fluence {ital per second} than entire TFTR discharges. Extrapolating neutron activation to these higher fluences will require yet more care. Some of the issues at such high fluences will be discussed.3 The National Ignition Facility (NIF) is projected to yield 10 MJ of fusion energy, or up to 10{sup 12} n/cm{sup 2} at the vacuum vessel wall, similar to TFTR DT conditions. It is expected that much interesting physics will be performed at yields far less than those from ignition, covering an even greater dynamic range than needed on TFTR. Thin foil techniques do not have the sensitivity required at low fluences.« less

  12. Neutron skyshine measurements at Fermilab.

    PubMed

    Cossairt, J D; Coulson, L V

    1985-02-01

    Neutron skyshine has been a significant source of environmental radiation exposure at many high-energy proton accelerators. A particularly troublesome source of skyshine neutrons has existed at Fermilab during operation of the 400-GeV high-energy physics program. This paper reports on several measurements of this source made with a DePangher precision long counter at large distances. The spatial distribution of the neutron skyshine can approximately be described as an inverse square law dependence multiplied by an exponential with an approximate attenuation length of 1200 +/- 300 m. The absolute magnitude of the distributions can be matched directly to the conventionally measured absorbed dose distribution near the source.

  13. Characterization of the Medley setup for measurements of neutron-induced fission cross sections at the GANIL-NFS facility

    NASA Astrophysics Data System (ADS)

    Tarrío, Diego; Prokofiev, Alexander V.; Gustavsson, Cecilia; Jansson, Kaj; Andersson-Sundén, Erik; Al-Adili, Ali; Pomp, Stephan

    2017-09-01

    Neutron-induced fission cross sections of 235U and 238U are widely used as standards for monitoring of neutron beams and fields. An absolute measurement of these cross sections at an absolute scale, i.e., versus the H(n,p) scattering cross section, is planned with the white neutron beam under construction at the Neutrons For Science (NFS) facility in GANIL. The experimental setup, based on PPACs and ΔE-ΔE-E telescopes containing Silicon and CsI(Tl) detectors, is described. The expected uncertainties are discussed.

  14. DESCANT--The DEuterated SCintillator Array for Neutron Tagging

    NASA Astrophysics Data System (ADS)

    Bildstein, Vinzenz; Garrett, P. E.; Bandyopadhay, D.; Bangay, J.; Bianco, L.; Demand, G.; Hadinia, B.; Leach, K. G.; Sumithrarachchi, C.; Wong, J.; Ashley, S. F.; Crider, B. P.; McEllistrem, M. T.; Peters, E. E.; Prados-Estévez, F. M.; Yates, S. W.; Vanhoy, J. R.; Ball, G. C.; Garnsworthy, A. B.; Hackman, G.; Pearson, C. J.; Sarazin, F.

    2014-09-01

    The DESCANT array at TRIUMF is designed to track neutrons from RIB experiments. DESCANT is composed of 70 close-packed deuterated organic liquid scintillators coupled to digital fast read-out ADC modules. This configuration will permit online pulse-shape discrimination between neutron and γ-ray events. The anisotropy of the n - d scattering will allow distinction of higher neutron multiplicities from scattering within the array and determination of the neutron energy spectrum directly from the pulse-height spectrum without using TOF. A prototype detector has been tested with monoenergetic neutrons at the accelerator laboratory of the University of Kentucky and a 24Mg(3He, n)26Si experiment has been performed with eight DESCANT detectors and two HPGe detectors. The results of the tests and the status of DESCANT will be presented.

  15. Earth albedo neutrons from 10 to 100 MeV.

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Simnett, G. M.; White, R. S.

    1972-01-01

    We report the measurement of the energy and angular distributions of earth albedo neutrons from 10 to 100 MeV at 40 deg N geomagnetic latitude from a balloon at 120,000 ft, below 4.65 g/sq cm. The albedo-neutron omnidirectional energy distribution is flat to 50 MeV, then decreases with energy. The absolute neutron energy distribution is of the correct strength and shape for the albedo neutrons to be the source of the protons trapped in earth's inner radiation belt.

  16. Achieving Climate Change Absolute Accuracy in Orbit

    NASA Technical Reports Server (NTRS)

    Wielicki, Bruce A.; Young, D. F.; Mlynczak, M. G.; Thome, K. J; Leroy, S.; Corliss, J.; Anderson, J. G.; Ao, C. O.; Bantges, R.; Best, F.; hide

    2013-01-01

    The Climate Absolute Radiance and Refractivity Observatory (CLARREO) mission will provide a calibration laboratory in orbit for the purpose of accurately measuring and attributing climate change. CLARREO measurements establish new climate change benchmarks with high absolute radiometric accuracy and high statistical confidence across a wide range of essential climate variables. CLARREO's inherently high absolute accuracy will be verified and traceable on orbit to Système Internationale (SI) units. The benchmarks established by CLARREO will be critical for assessing changes in the Earth system and climate model predictive capabilities for decades into the future as society works to meet the challenge of optimizing strategies for mitigating and adapting to climate change. The CLARREO benchmarks are derived from measurements of the Earth's thermal infrared spectrum (5-50 micron), the spectrum of solar radiation reflected by the Earth and its atmosphere (320-2300 nm), and radio occultation refractivity from which accurate temperature profiles are derived. The mission has the ability to provide new spectral fingerprints of climate change, as well as to provide the first orbiting radiometer with accuracy sufficient to serve as the reference transfer standard for other space sensors, in essence serving as a "NIST [National Institute of Standards and Technology] in orbit." CLARREO will greatly improve the accuracy and relevance of a wide range of space-borne instruments for decadal climate change. Finally, CLARREO has developed new metrics and methods for determining the accuracy requirements of climate observations for a wide range of climate variables and uncertainty sources. These methods should be useful for improving our understanding of observing requirements for most climate change observations.

  17. "Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory", Köhler et al.

    NASA Astrophysics Data System (ADS)

    Miller, Jack

    2015-04-01

    The Mars Science Laboratory (MSL) spacecraft carried the Curiosity rover to Mars. While the dramatic, successful landing of Curiosity and its subsequent exploration of the Martian surface have justifiably generated great excitement, from the standpoint of the health of crewmembers on missions to Mars, knowledge of the environment between Earth and Mars is critical. This paper reports data taken during the cruise phase of the MSL by the Radiation Assessment Detector (RAD). The results are of great interest for several reasons. They are a direct measurement of the radiation environment during what will be a significant fraction of the duration of a proposed human mission to Mars; they were made behind the de facto shielding provided by various spacecraft components; and, in particular, they are a measurement of the contribution to radiation dose by neutrons. The neutron environment inside spacecraft is produced primarily by galactic cosmic ray ions interacting in shielding materials, and given the high biological effectiveness of neutrons and the increased contribution of neutrons to dose with increased depth in shielding, accurate knowledge of the neutron energy spectrum behind shielding is vital. The results show a relatively modest contribution from neutrons and gammas compared to that from charged particles, but also a discrepancy in both dose and dose rate between the data and simulations. The failure of the calculations to accurately reproduce the data is significant, given that future manned spacecraft will be more heavily shielded (and thus produce more secondary neutrons) and that spacecraft design will rely on simulations and model calculations of radiation transport. The methodology of risk estimation continues to evolve, and incorporates our knowledge of both the physical and biological effects of radiation. The relatively large uncertainties in the biological data, and the difficulties in reducing those uncertainties, makes it all the more important to

  18. Monitoring of the Irradiated Neutron Fluence in the Neutron Transmutation Doping Process of Hanaro

    NASA Astrophysics Data System (ADS)

    Kim, Myong-Seop; Park, Sang-Jun

    2009-08-01

    Neutron transmutation doping (NTD) for silicon is a process of the creation of phosphorus impurities in intrinsic or extrinsic silicon by neutron irradiation to obtain silicon semiconductors with extremely uniform dopant distribution. HANARO has two vertical holes for the NTD, and the irradiation for 5 and 6 inch silicon ingots has been going on at one hole. In order to achieve the accurate neutron fluence corresponding to the target resistivity, the real time neutron flux is monitored by self-powered neutron detectors. After irradiation, the total irradiation fluence is confirmed by measuring the absolute activity of activation detectors. In this work, a neutron fluence monitoring method using zirconium foils with the mass of 10 ~ 50 mg was applied to the NTD process of HANARO. We determined the proportional constant of the relationship between the resistivity of the irradiated silicon and the neutron fluence determined by using zirconium foils. The determined constant for the initially n-type silicon was 3.126 × 1019 n·Ω/cm. It was confirmed that the difference between this empirical value and the theoretical one was only 0.5%. Conclusively, the practical methodology to perform the neutron transmutation doping of silicon was established.

  19. Accelerator-Based Biological Irradiation Facility Simulating Neutron Exposure from an Improvised Nuclear Device.

    PubMed

    Xu, Yanping; Randers-Pehrson, Gerhard; Turner, Helen C; Marino, Stephen A; Geard, Charles R; Brenner, David J; Garty, Guy

    2015-10-01

    We describe here an accelerator-based neutron irradiation facility, intended to expose blood or small animals to neutron fields mimicking those from an improvised nuclear device at relevant distances from the epicenter. Neutrons are generated by a mixed proton/deuteron beam on a thick beryllium target, generating a broad spectrum of neutron energies that match those estimated for the Hiroshima bomb at 1.5 km from ground zero. This spectrum, dominated by neutron energies between 0.2 and 9 MeV, is significantly different from the standard reactor fission spectrum, as the initial bomb spectrum changes when the neutrons are transported through air. The neutron and gamma dose rates were measured using a custom tissue-equivalent gas ionization chamber and a compensated Geiger-Mueller dosimeter, respectively. Neutron spectra were evaluated by unfolding measurements using a proton-recoil proportional counter and a liquid scintillator detector. As an illustration of the potential use of this facility we present micronucleus yields in single divided, cytokinesis-blocked human peripheral lymphocytes up to 1.5 Gy demonstrating 3- to 5-fold enhancement over equivalent X-ray doses. This facility is currently in routine use, irradiating both mice and human blood samples for evaluation of neutron-specific biodosimetry assays. Future studies will focus on dose reconstruction in realistic mixed neutron/photon fields.

  20. Accelerator-Based Biological Irradiation Facility Simulating Neutron Exposure from an Improvised Nuclear Device

    PubMed Central

    Xu, Yanping; Randers-Pehrson, Gerhard; Turner, Helen C.; Marino, Stephen A.; Geard, Charles R.; Brenner, David J.; Garty, Guy

    2015-01-01

    We describe here an accelerator-based neutron irradiation facility, intended to expose blood or small animals to neutron fields mimicking those from an improvised nuclear device at relevant distances from the epicenter. Neutrons are generated by a mixed proton/deuteron beam on a thick beryllium target, generating a broad spectrum of neutron energies that match those estimated for the Hiroshima bomb at 1.5 km from ground zero. This spectrum, dominated by neutron energies between 0.2 and 9 MeV, is significantly different from the standard reactor fission spectrum, as the initial bomb spectrum changes when the neutrons are transported through air. The neutron and gamma dose rates were measured using a custom tissue-equivalent gas ionization chamber and a compensated Geiger-Mueller dosimeter, respectively. Neutron spectra were evaluated by unfolding measurements using a proton-recoil proportional counter and a liquid scintillator detector. As an illustration of the potential use of this facility we present micronucleus yields in single divided, cytokinesis-blocked human peripheral lymphocytes up to 1.5 Gy demonstrating 3- to 5-fold enhancement over equivalent X-ray doses. This facility is currently in routine use, irradiating both mice and human blood samples for evaluation of neutron-specific biodosimetry assays. Future studies will focus on dose reconstruction in realistic mixed neutron/photon fields. PMID:26414507

  1. Neutron Particle Effects on a Quad-Redundant Flight Control Computer

    NASA Technical Reports Server (NTRS)

    Eure, Kenneth; Belcastro, Celeste M.; Gray, W Steven; Gonzalex, Oscar

    2003-01-01

    This paper describes a single-event upset experiment performed at the Los Alamos National Laboratory. A closed-loop control system consisting of a Quad-Redundant Flight Control Computer (FCC) and a B737 simulator was operated while the FCC was exposed to a neutron beam. The purpose of this test was to analyze the effects of neutron bombardment on avionics control systems operating at altitudes where neutron strikes are probable. The neutron energy spectrum produced at the Los Alamos National Laboratory is similar in shape to the spectrum of atmospheric neutrons but much more intense. The higher intensity results in accelerated life tests that are representative of the actual neutron radiation that a FCC may receive over a period of years.

  2. Spectra of random operators with absolutely continuous integrated density of states

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Rio, Rafael del, E-mail: delrio@iimas.unam.mx, E-mail: delriomagia@gmail.com

    2014-04-15

    The structure of the spectrum of random operators is studied. It is shown that if the density of states measure of some subsets of the spectrum is zero, then these subsets are empty. In particular follows that absolute continuity of the integrated density of states implies singular spectra of ergodic operators is either empty or of positive measure. Our results apply to Anderson and alloy type models, perturbed Landau Hamiltonians, almost periodic potentials, and models which are not ergodic.

  3. The "neutron channel design"—A method for gaining the desired neutrons

    NASA Astrophysics Data System (ADS)

    Hu, G.; Hu, H. S.; Wang, S.; Pan, Z. H.; Jia, Q. G.; Yan, M. F.

    2016-12-01

    The neutrons with desired parameters can be obtained after initial neutrons penetrating various structure and component of the material. A novel method, the "neutron channel design", is proposed in this investigation for gaining the desired neutrons. It is established by employing genetic algorithm (GA) combining with Monte Carlo software. This method is verified by obtaining 0.01eV to 1.0eV neutrons from the Compact Accelerator-driven Neutron Source (CANS). One layer polyethylene (PE) moderator was designed and installed behind the beryllium target in CANS. The simulations and the experiment for detection the neutrons were carried out. The neutron spectrum at 500cm from the PE moderator was simulated by MCNP and PHITS software. The counts of 0.01eV to 1.0eV neutrons were simulated by MCNP and detected by the thermal neutron detector in the experiment. These data were compared and analyzed. Then this method is researched on designing the complex structure of PE and the composite material consisting of PE, lead and zirconium dioxide.

  4. Beam Characterization at the Neutron Radiography Facility

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sarah Morgan; Jeffrey King

    The quality of a neutron imaging beam directly impacts the quality of radiographic images produced using that beam. Fully characterizing a neutron beam, including determination of the beam’s effective length-to-diameter ratio, neutron flux profile, energy spectrum, image quality, and beam divergence, is vital for producing quality radiographic images. This project characterized the east neutron imaging beamline at the Idaho National Laboratory Neutron Radiography Reactor (NRAD). The experiments which measured the beam’s effective length-to-diameter ratio and image quality are based on American Society for Testing and Materials (ASTM) standards. An analysis of the image produced by a calibrated phantom measured themore » beam divergence. The energy spectrum measurements consist of a series of foil irradiations using a selection of activation foils, compared to the results produced by a Monte Carlo n-Particle (MCNP) model of the beamline. Improvement of the existing NRAD MCNP beamline model includes validation of the model’s energy spectrum and the development of enhanced image simulation methods. The image simulation methods predict the radiographic image of an object based on the foil reaction rate data obtained by placing a model of the object in front of the image plane in an MCNP beamline model.« less

  5. Concurrent Application of ANC and THM to assess the 13C(α, n)16O Absolute Cross Section at Astrophysical Energies and Possible Consequences for Neutron Production in Low-mass AGB Stars

    NASA Astrophysics Data System (ADS)

    Trippella, O.; La Cognata, M.

    2017-03-01

    The {}13{{C}}{(α ,n)}16{{O}} reaction is considered to be the main neutron source responsible for the production of heavy nuclides (from {Sr} to {Bi}) through slow n-capture nucleosynthesis (s-process) at low temperatures during the asymptotic giant branch phase of low-mass stars (≲ 3{--}4 {M}⊙ , or LMSs). In recent years, several direct and indirect measurements have been carried out to determine the cross section at the energies of astrophysical interest (around 190+/- 40 {keV}). However, they yield inconsistent results that cause a highly uncertain reaction rate and affect the neutron release in LMSs. In this work we have combined two indirect approaches, the asymptotic normalization coefficient and the Trojan horse method, to unambiguously determine the absolute value of the {}13{{C}}{(α ,n)}16{{O}} astrophysical factor. With these, we have determined a very accurate reaction rate to be introduced into astrophysical models of s-process nucleosynthesis in LMSs. Calculations using this recommended rate have shown limited variations in the production of those neutron-rich nuclei (with 86≤slant A≤slant 209) that receive contribution only by slow neutron captures.

  6. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, D.A.; Erkkila, B.H.; Vasilik, D.G.

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  7. Portable neutron spectrometer and dosimeter

    DOEpatents

    Waechter, David A.; Erkkila, Bruce H.; Vasilik, Dennis G.

    1985-01-01

    The disclosure relates to a battery operated neutron spectrometer/dosimeter utilizing a microprocessor, a built-in tissue equivalent LET neutron detector, and a 128-channel pulse height analyzer with integral liquid crystal display. The apparatus calculates doses and dose rates from neutrons incident on the detector and displays a spectrum of rad or rem as a function of keV per micron of equivalent tissue and also calculates and displays accumulated dose in millirads and millirem as well as neutron dose rates in millirads per hour and millirem per hour.

  8. Plans for a measurement of the neutron lifetime to better than 0.3s using a Penning trap and absolute measurement of neutron fluence

    NASA Astrophysics Data System (ADS)

    Mulholland, Jonathan; NBL3 Collaboration

    2014-09-01

    The decay of the free neutron is the prototypical charged current semi-leptonic weak process. A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is needed to predict the primordial He4 abundance from the theory of Big Bang Nucleosynthesis. Plans are being made for an in-beam measurement of the neutron lifetime with an anticipated 0.3s of uncertainty or better. This effort is part of a phased campaign of neutron lifetime measurements based at the NIST Center for Neutron Research, using the Sussex-ILL-NIST technique. Advances in neutron fluence measurement, used in to provide the best existing in-beam determination of the neutron lifetime, as well as new silicon detector technology, in use now at LANSCE, address the two largest contributors to the uncertainty of in-beam measurements-the statistical uncertainty associated with proton counting and the systematic uncertainty in the neutron fluence measurement. The experimental design and projected uncertainties for the 0.3s measurement will be discussed.

  9. Evaluation of the Neutron Data Standards

    NASA Astrophysics Data System (ADS)

    Carlson, A. D.; Pronyaev, V. G.; Capote, R.; Hale, G. M.; Chen, Z.-P.; Duran, I.; Hambsch, F.-J.; Kunieda, S.; Mannhart, W.; Marcinkevicius, B.; Nelson, R. O.; Neudecker, D.; Noguere, G.; Paris, M.; Simakov, S. P.; Schillebeeckx, P.; Smith, D. L.; Tao, X.; Trkov, A.; Wallner, A.; Wang, W.

    2018-02-01

    With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations of the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α1 γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.

  10. Photon attenuation and neutron moderation correction factors for the inspection of cargo containers with tagged neutrons

    NASA Astrophysics Data System (ADS)

    Carasco, C.; Perot, B.; Viesti, G.; Valkovic, V.; Sudac, D.; Bernard, S.; Mariani, A.; Szabo, J.-L.; Sannie, G.; Lunardon, M.; Bottosso, C.; Moretto, S.; Pesente, S.; Peerani, P.; Sequeira, V.; Salvato, M.

    2007-11-01

    The EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) inspection system uses 14 MeV neutrons produced by the D(T,n α) reaction to detect explosives in cargo containers. Fast-neutron-induced reactions inside the container produce gamma rays, which are detected in coincidence with the associated alpha particle. The definition of the neutron path and the time-of-flight measurement allow positioning the source of the gamma ray inside the container, while the chemical composition of the target material is correlated with the energy spectrum of the coincident gamma rays. However, in case of dense cargo, neutron moderation and photon attenuation inside the container make difficult the reconstruction of the material composition from the measured gamma-ray energy spectrum. An analytical method has been developed and validated against experimental data, which allows obtaining the chemical carbon-to-oxygen and carbon-to-nitrogen ratios of the inspected items from the gamma-ray energy spectra. The principle of the method is presented along with validation tests.

  11. Geant4 beam model for boron neutron capture therapy: investigation of neutron dose components.

    PubMed

    Moghaddasi, Leyla; Bezak, Eva

    2018-03-01

    Boron neutron capture therapy (BNCT) is a biochemically-targeted type of radiotherapy, selectively delivering localized dose to tumour cells diffused in normal tissue, while minimizing normal tissue toxicity. BNCT is based on thermal neutron capture by stable [Formula: see text]B nuclei resulting in emission of short-ranged alpha particles and recoil [Formula: see text]Li nuclei. The purpose of the current work was to develop and validate a Monte Carlo BNCT beam model and to investigate contribution of individual dose components resulting of neutron interactions. A neutron beam model was developed in Geant4 and validated against published data. The neutron beam spectrum, obtained from literature for a cyclotron-produced beam, was irradiated to a water phantom with boron concentrations of 100 μg/g. The calculated percentage depth dose curves (PDDs) in the phantom were compared with published data to validate the beam model in terms of total and boron depth dose deposition. Subsequently, two sensitivity studies were conducted to quantify the impact of: (1) neutron beam spectrum, and (2) various boron concentrations on the boron dose component. Good agreement was achieved between the calculated and measured neutron beam PDDs (within 1%). The resulting boron depth dose deposition was also in agreement with measured data. The sensitivity study of several boron concentrations showed that the calculated boron dose gradually converged beyond 100 μg/g boron concentration. This results suggest that 100μg/g tumour boron concentration may be optimal and above this value limited increase in boron dose is expected for a given neutron flux.

  12. Abrasion-ablation model for neutron production in heavy ion reactions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Wilson, John W.; Townsend, Lawrence W.

    1995-01-01

    In heavy ion reactions, neutron production at forward angles is observed to occur with a Gaussian shape that is centered near the beam energy and extends to energies well above that of the beam. This paper presents an abrasion-ablation model for making quantitative predictions of the neutron spectrum. To describe neutrons produced from the abrasion step of the reaction where the projectile and target overlap, the authors use the Glauber model and include effects of final-state interactions. They then use the prefragment mass distribution from abrasion with a statistical evaporation model to estimate the neutron spectrum resulting from ablation. Measurements of neutron production from Ne and Nb beams are compared with calculations, and good agreement is found.

  13. Improved Delayed-Neutron Spectroscopy Using Trapped Ions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Norman, Eric B.

    The neutrons emitted following the β decay of fission fragments (known as delayed neutrons because they are emitted after fission on a timescale of the β-decay half-lives) play a crucial role in reactor performance and control. Reviews of delayed-neutron properties highlight the need for high-quality data for a wide variety of delayed-neutron emitters to better understand the time dependence and energy spectrum of the neutrons as these properties are essential for a detailed understanding of reactor kinetics needed for reactor safety and to understand the behavior of these reactors under various accident and component-failure scenarios. For fast breeder reactors, criticalitymore » calculations require accurate delayed-neutron energy spectra and approximations that are acceptable for light-water reactors such as assuming the delayed-neutron and fission-neutron energy spectra are identical are not acceptable and improved β-delayed neutron data is needed for safety and accident analyses for these reactors. With improved nuclear data, the delayed neutrons flux and energy spectrum could be calculated from the contributions from individual isotopes and therefore could be accurately modeled for any fuel-cycle concept, actinide mix, or irradiation history. High-quality β-delayed neutron measurements are also critical to constrain modern nuclear-structure calculations and empirical models that predict the decay properties for nuclei for which no data exists and improve the accuracy and flexibility of the existing empirical descriptions of delayed neutrons from fission such as the six-group representation« less

  14. Preliminary On-Orbit Neutron Dose Equivalent and Energy Spectrum Results from the ISS-RAD Fast Neutron Detector (FND)

    NASA Technical Reports Server (NTRS)

    Semones, Edward; Leitgab, Martin

    2016-01-01

    The ISS-RAD instrument was activated on ISS on February 1st, 2016. Integrated in ISS-RAD, the Fast Neutron Detector (FND) performs, for the first time on ISS, routine and precise direct neutron measurements between 0.5 and 8 MeV. Preliminary results for neutron dose equivalent and neutron flux energy distributions from online/on-board algorithms and offline ground analyses will be shown, along with comparisons to simulated data and previously measured neutron spectral data. On-orbit data quality and pre-launch analysis validation results will be discussed as well.

  15. Advances in Neutron Spectroscopy with Deuterated Organic Scintillators

    NASA Astrophysics Data System (ADS)

    Febbraro, Michael; Pain, Steve; Becchetti, Frederick

    2015-10-01

    Deuterated organic scintillators have shown promise as neutron detectors for nuclear science as well as applications in nuclear non-proliferation and safeguards. In particular, they can extract neutron spectra without the use of neutron time-of-flight measurement (n-ToF) utilizing spectrum unfolding techniques. This permits the measure of cross sections of bound and unbound states with high efficiency and angular coverage. In the case of measurements with radioactive ion beams where low beam intensities limit long path n-ToF, short path n-ToF can be used to discriminate neutrons of interest from room return and background neutrons. This presentation will provide recent advances with these types of detectors. Digital pulse-shape discrimination using fast waveform digitizers, spectrum unfolding methods for extraction of neutron spectra, and a new safer deuterated-xylene formulation EJ-301D will be discussed. In addition, experimental results from measurements of discrete and continuous neutron spectra which illustrate the advantage of these detectors for certain applications in nuclear physics research and nuclear security will be shown. This work is supported by NSF and DOE.

  16. Normalization of a collimated 14.7 MeV neutron source in a neutron spectrometry system for benchmark experiments

    NASA Astrophysics Data System (ADS)

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

    1988-05-01

    In the present study a method used to normalize a collimated 14.7 MeV neutron beam is introduced. It combined a measurement of the fast neutron scalar flux passing through the collimator, using a copper foil activation, with a neutron transport calculation of the foil activation per unit source neutron, carried out by the discrete-ordinates transport code DOT 4.2. The geometry of the collimated neutron beam is composed of a D-T neutron source positioned 30 cm in front of a 6 cm diameter collimator, through a 120 cm thick paraffin wall. The neutron flux emitted from the D-T source was counted by an NE-213 scintillator, simultaneously with the irradiation of the copper foil. Thus, the determination of the normalization factor of the D-T source is used for an absolute flux calibration of the NE-213 scintillator. The major contributions to the uncertainty in the determination of the normalization factor, and their origins, are discussed.

  17. Organic Scintillator for Real-Time Neutron Dosimetry

    DOE PAGES

    Beyer, Kyle A.; Di Fulvio, Angela; Stolarczyk, Liliana; ...

    2017-11-15

    We have developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV–0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cfmore » neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.« less

  18. Organic Scintillator for Real-Time Neutron Dosimetry

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Beyer, Kyle A.; Di Fulvio, Angela; Stolarczyk, Liliana

    We have developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV–0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cfmore » neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom.« less

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. β -delayed neutron emission from 85Ga

    NASA Astrophysics Data System (ADS)

    Miernik, K.; Rykaczewski, K. P.; Grzywacz, R.; Gross, C. J.; Madurga, M.; Miller, D.; Stracener, D. W.; Batchelder, J. C.; Brewer, N. T.; Korgul, A.; Mazzocchi, C.; Mendez, A. J.; Liu, Y.; Paulauskas, S. V.; Winger, J. A.; Wolińska-Cichocka, M.; Zganjar, E. F.

    2018-05-01

    Decay of 85Ga was studied by means of β -neutron-γ spectroscopy. A pure beam of 85Ga was produced at the Holifield Radioactive Ion Beam Facility using a resonance ionization laser ion source and a high-resolution electromagnetic separator. The β -delayed neutron emission probability was measured for the first time, yielding 70(5)%. An upper limit of 0.1% for β -delayed two-neutron emission was also experimentally established for the first time. A detailed decay scheme including absolute γ -ray intensities was obtained. Results are compared with theoretical β -delayed emission models.

  1. Thermal neutron filter design for the neutron radiography facility at the LVR-15 reactor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Soltes, Jaroslav; Faculty of Nuclear Sciences and Physical Engineering, CTU in Prague,; Viererbl, Ladislav

    2015-07-01

    In 2011 a decision was made to build a neutron radiography facility at one of the unused horizontal channels of the LVR-15 research reactor in Rez, Czech Republic. One of the key conditions for operating an effective radiography facility is the delivery of a high intensity, homogeneous and collimated thermal neutron beam at the sample location. Additionally the intensity of fast neutrons has to be kept as low as possible as the fast neutrons may damage the detectors used for neutron imaging. As the spectrum in the empty horizontal channel roughly copies the spectrum in the reactor core, which hasmore » a high ratio of fast neutrons, neutron filter components have to be installed inside the channel in order to achieve desired beam parameters. As the channel design does not allow the instalment of complex filters and collimators, an optimal solution represent neutron filters made of large single-crystal ingots of proper material composition. Single-crystal silicon was chosen as a favorable filter material for its wide availability in sufficient dimensions. Besides its ability to reasonably lower the ratio of fast neutrons while still keeping high intensities of thermal neutrons, due to its large dimensions, it suits as a shielding against gamma radiation from the reactor core. For designing the necessary filter dimensions the Monte-Carlo MCNP transport code was used. As the code does not provide neutron cross-section libraries for thermal neutron transport through single-crystalline silicon, these had to be created by approximating the theory of thermal neutron scattering and modifying the original cross-section data which are provided with the code. Carrying out a series of calculations the filter thickness of 1 m proved good for gaining a beam with desired parameters and a low gamma background. After mounting the filter inside the channel several measurements of the neutron field were realized at the beam exit. The results have justified the expected calculated

  2. Calibration-free absolute frequency response measurement of directly modulated lasers based on additional modulation.

    PubMed

    Zhang, Shangjian; Zou, Xinhai; Wang, Heng; Zhang, Yali; Lu, Rongguo; Liu, Yong

    2015-10-15

    A calibration-free electrical method is proposed for measuring the absolute frequency response of directly modulated semiconductor lasers based on additional modulation. The method achieves the electrical domain measurement of the modulation index of directly modulated lasers without the need for correcting the responsivity fluctuation in the photodetection. Moreover, it doubles measuring frequency range by setting a specific frequency relationship between the direct and additional modulation. Both the absolute and relative frequency response of semiconductor lasers are experimentally measured from the electrical spectrum of the twice-modulated optical signal, and the measured results are compared to those obtained with conventional methods to check the consistency. The proposed method provides calibration-free and accurate measurement for high-speed semiconductor lasers with high-resolution electrical spectrum analysis.

  3. Evaluation of the Neutron Data Standards

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carlson, A. D.; Pronyaev, V. G.; Capote, R.

    With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations ofmore » the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α 1γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.« less

  4. Evaluation of the Neutron Data Standards

    DOE PAGES

    Carlson, A. D.; Pronyaev, V. G.; Capote, R.; ...

    2018-02-01

    With the need for improving existing nuclear data evaluations, (e.g., ENDF/B-VIII.0 and JEFF-3.3 releases) the first step was to evaluate the standards for use in such a library. This new standards evaluation made use of improved experimental data and some developments in the methodology of analysis and evaluation. In addition to the work on the traditional standards, this work produced the extension of some energy ranges and includes new reactions that are called reference cross sections. Since the effort extends beyond the traditional standards, it is called the neutron data standards evaluation. This international effort has produced new evaluations ofmore » the following cross section standards: the H(n,n), 6Li(n,t), 10B(n,α), 10B(n,α 1γ), natC(n,n), Au(n,γ), 235U(n,f) and 238U(n,f). Also in the evaluation process the 238U(n,γ) and 239Pu(n,f) cross sections that are not standards were evaluated. Evaluations were also obtained for data that are not traditional standards: the Maxwellian spectrum averaged cross section for the Au(n,γ) cross section at 30 keV; reference cross sections for prompt γ-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 252Cf spontaneous fission neutron spectrum and the 235U prompt fission neutron spectrum induced by thermal incident neutrons; and the thermal neutron constants. The data and covariance matrices of the uncertainties were obtained directly from the evaluation procedure.« less

  5. Evaluation of the 239 Pu prompt fission neutron spectrum induced by neutrons of 500 keV and associated covariances

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Neudecker, D.; Talou, P.; Kawano, T.

    2015-08-01

    We present evaluations of the prompt fission neutron spectrum (PFNS) of (PU)-P-239 induced by 500 keV neutrons, and associated covariances. In a previous evaluation by Talon et al. (2010), surprisingly low evaluated uncertainties were obtained, partly due to simplifying assumptions in the quantification of uncertainties from experiment and model. Therefore, special emphasis is placed here on a thorough uncertainty quantification of experimental data and of the Los Alamos model predicted values entering the evaluation. In addition, the Los Alamos model was extended and an evaluation technique was employed that takes into account the qualitative differences between normalized model predicted valuesmore » and experimental shape data These improvements lead to changes in the evaluated PENS and overall larger evaluated uncertainties than in the previous work. However, these evaluated uncertainties are still smaller than those obtained in a statistical analysis using experimental information only, due to strong model correlations. Hence, suggestions to estimate model defect uncertainties are presented. which lead to more reasonable evaluated uncertainties. The calculated k(eff) of selected criticality benchmarks obtained with these new evaluations agree with each other within their uncertainties despite the different approaches to estimate model defect uncertainties. The k(eff) one standard deviations overlap with some of those obtained using ENDF/B-VILl, albeit their mean values are further away from unity. Spectral indexes for the Jezebel critical assembly calculated with the newly evaluated PFNS agree with the experimental data for selected (n,) and (n,f) reactions, and show improvements for highenergy threshold (n,2n) reactions compared to ENDF/B-VII.l. (C) 2015 Elsevier B.V. All rights reserved.« less

  6. Feasibility of sealed D-T neutron generator as neutron source for liver BNCT and its beam shaping assembly.

    PubMed

    Liu, Zheng; Li, Gang; Liu, Linmao

    2014-04-01

    This paper involves the feasibility of boron neutron capture therapy (BNCT) for liver tumor with four sealed neutron generators as neutron source. Two generators are placed on each side of the liver. The high energy of these emitted neutrons should be reduced by designing a beam shaping assembly (BSA) to make them useable for BNCT. However, the neutron flux decreases as neutrons pass through different materials of BSA. Therefore, it is essential to find ways to increase the neutron flux. In this paper, the feasibility of using low enrichment uranium as a neutron multiplier is investigated to increase the number of neutrons emitted from D-T neutron generators. The neutron spectrum related to our system has a proper epithermal flux, and the fast and thermal neutron fluxes comply with the IAEA recommended values. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Neutron spectroscopy of γ manganese hydride

    NASA Astrophysics Data System (ADS)

    Antonov, V. E.; Cornell, K.; Dorner, B.; Fedotov, V. K.; Grosse, G.; Kolesnikov, A. I.; Wagner, F. E.; Wipf, H.

    2000-02-01

    The vibrational spectrum of fcc γ-MnH 0.41 synthesized under high pressure of gaseous hydrogen was studied by inelastic neutron scattering at 2 K in the range of energy transfers from 25 to 400 meV. The fundamental band of optical hydrogen vibrations consists of a peak at 111 meV with a broad shoulder towards higher energies, which extends up to about 140 meV. At higher energy transfers, the spectrum originates from multiphonon neutron scattering and exhibits approximately harmonic behaviour. The results are compared with the available data for other metal hydrides.

  8. Measurement of absolute response functions and detection efficiencies of an NE213 scintillator up to 600 MeV

    NASA Astrophysics Data System (ADS)

    Kajimoto, Tsuyoshi; Shigyo, Nobuhiro; Sanami, Toshiya; Ishibashi, Kenji; Haight, Robert C.; Fotiades, Nikolaos

    2011-02-01

    Absolute neutron response functions and detection efficiencies of an NE213 liquid scintillator that was 12.7 cm in diameter and 12.7 cm in thickness were measured for neutron energies between 15 and 600 MeV at the Weapons Neutron Research facility of the Los Alamos Neutron Science Center. The experiment was performed with continuous-energy neutrons on a spallation neutron source by 800-MeV proton incidence. The incident neutron flux was measured using a 238U fission ionization chamber. Measured response functions and detection efficiencies were compared with corresponding calculations using the SCINFUL-QMD code. The calculated and experimental values were in good agreement for data below 70 MeV. However, there were discrepancies in the energy region between 70 and 150 MeV. Thus, the code was partly modified and the revised code provided better agreement with the experimental data.

  9. Dynamic frequency-domain interferometer for absolute distance measurements with high resolution

    NASA Astrophysics Data System (ADS)

    Weng, Jidong; Liu, Shenggang; Ma, Heli; Tao, Tianjiong; Wang, Xiang; Liu, Cangli; Tan, Hua

    2014-11-01

    A unique dynamic frequency-domain interferometer for absolute distance measurement has been developed recently. This paper presents the working principle of the new interferometric system, which uses a photonic crystal fiber to transmit the wide-spectrum light beams and a high-speed streak camera or frame camera to record the interference stripes. Preliminary measurements of harmonic vibrations of a speaker, driven by a radio, and the changes in the tip clearance of a rotating gear wheel show that this new type of interferometer has the ability to perform absolute distance measurements both with high time- and distance-resolution.

  10. The neutronic design and performance of the Indiana University Cyclotron Facility (IUCF) Low Energy Neutron Source (LENS)

    NASA Astrophysics Data System (ADS)

    Lavelle, Christopher M.

    Neutron scattering research is performed primarily at large-scale facilities. However, history has shown that smaller scale neutron scattering facilities can play a useful role in education and innovation while performing valuable materials research. This dissertation details the design and experimental validation of the LENS TMR as an example for a small scale accelerator driven neutron source. LENS achieves competitive long wavelength neutron intensities by employing a novel long pulse mode of operation, where the neutron production target is irradiated on a time scale comparable to the emission time of neutrons from the system. Monte Carlo methods have been employed to develop a design for optimal production of long wavelength neutrons from the 9Be(p,n) reaction at proton energies ranging from 7 to 13 MeV proton energy. The neutron spectrum was experimentally measured using time of flight, where it is found that the impact of the long pulse mode on energy resolution can be eliminated at sub-eV neutron energies if the emission time distribution of neutron from the system is known. The emission time distribution from the TMR system is measured using a time focussed crystal analyzer. Emission time of the fundamental cold neutron mode is found to be consistent with Monte Carlo results. The measured thermal neutron spectrum from the water reflector is found to be in agreement with Monte Carlo predictions if the scattering kernels employed are well established. It was found that the scattering kernels currently employed for cryogenic methane are inadequate for accurate prediction of the cold neutron intensity from the system. The TMR and neutronic modeling have been well characterized and the source design is flexible, such that it is possible for LENS to serve as an effective test bed for future work in neutronic development. Suggestions for improvements to the design that would allow increased neutron flux into the instruments are provided.

  11. Progress toward a new beam measurement of the neutron lifetime

    NASA Astrophysics Data System (ADS)

    Hoogerheide, Shannon Fogwell

    2016-09-01

    Neutron beta decay is the simplest example of nuclear beta decay. A precise value of the neutron lifetime is important for consistency tests of the Standard Model and Big Bang Nucleosysnthesis models. The beam neutron lifetime method requires the absolute counting of the decay protons in a neutron beam of precisely known flux. Recent work has resulted in improvements in both the neutron and proton detection systems that should permit a significant reduction in systematic uncertainties. A new measurement of the neutron lifetime using the beam method will be performed at the National Institute of Standards and Technology Center for Neutron Research. The projected uncertainty of this new measurement is 1 s. An overview of the measurement and the technical improvements will be discussed.

  12. Progress toward a new beam measurement of the neutron lifetime

    NASA Astrophysics Data System (ADS)

    Hoogerheide, Shannon Fogwell; BL2 Collaboration

    2017-01-01

    Neutron beta decay is the simplest example of nuclear beta decay. A precise value of the neutron lifetime is important for consistency tests of the Standard Model and Big Bang Nucleosynthesis models. The beam neutron lifetime method requires the absolute counting of the decay protons in a neutron beam of precisely known flux. Recent work has resulted in improvements in both the neutron and proton detection systems that should permit a significant reduction in systematic uncertainties. A new measurement of the neutron lifetime using the beam method is underway at the National Institute of Standards and Technology Center for Neutron Research. The projected uncertainty of this new measurement is 1 s. An overview of the measurement, its current status, and the technical improvements will be discussed.

  13. A Monte Carlo simulation and setup optimization of output efficiency to PGNAA thermal neutron using 252Cf neutrons

    NASA Astrophysics Data System (ADS)

    Zhang, Jin-Zhao; Tuo, Xian-Guo

    2014-07-01

    We present the design and optimization of a prompt γ-ray neutron activation analysis (PGNAA) thermal neutron output setup based on Monte Carlo simulations using MCNP5 computer code. In these simulations, the moderator materials, reflective materials, and structure of the PGNAA 252Cf neutrons of thermal neutron output setup are optimized. The simulation results reveal that the thin layer paraffin and the thick layer of heavy water moderating effect work best for the 252Cf neutron spectrum. Our new design shows a significantly improved performance of the thermal neutron flux and flux rate, that are increased by 3.02 times and 3.27 times, respectively, compared with the conventional neutron source design.

  14. Hot background” of the mobile inelastic neutron scattering system for soil carbon analysis

    USDA-ARS?s Scientific Manuscript database

    The problem of gamma spectrum peaks identification arises when conducting soil carbon (and other elements) analysis using the mobile inelastic neutron scattering (MINS) system. Some gamma spectrum peaks could be associated with radioisotopes appearing due to neutron activation of both the MINS syste...

  15. Large Cleaner Detectors for the UCN τ Neutron Lifetime Experiment

    NASA Astrophysics Data System (ADS)

    Gonzalez, Francisco; UCNtau Collaboration

    2017-09-01

    The UCN τ experiment at Los Alamos National Laboratory measures the neutron β-decay lifetime by storing ultracold neutrons (UCNs) in a magneto-gravitational trap for holding times longer than the neutron's lifetime. Neutrons with energies above the trapping potential can escape the trap, giving rise to a systematic error. To mitigate this effect, a large polyethylene sheet is lowered into the trap to remove the high energy unbound neutrons. High energy UCN upscatter in the polyethylene sheet and leave the trap. Such a ``UCN spectrum cleaner,'' covering half the trap top, was shown to be effective in removing high-energy neutrons in previous run cycles. During this run cycle, the UCN τ collaboration has added two thermal neutron detectors on the spectrum cleaner. The new thermal neutron detectors will monitor high-energy neutrons throughout upcoming run cycles, providing important information on the neutron normalization, spectral cleaning, and heating during storage. These detectors use LiF-ZnS sheets coupled to a wavelength-shifting plastic slab, with silicon photomultipliers attached to the edges. We will present results of the light detection simulation and performance tests of these detectors.

  16. The Los Alamos Neutron Science Center Spallation Neutron Sources

    NASA Astrophysics Data System (ADS)

    Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

    The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutrons are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ∼100 keV. The characteristics of these sources, and

  17. Measurement of D-7Li Neutron Production in Neutron Generators Using the Threshold Activation Foil Technique

    NASA Astrophysics Data System (ADS)

    Coventry, M. D.; Krites, A. M.

    Measurements to determine the absolute D-D and D-7Li neutron production rates with a neutron generator running at 100-200 kV acceleration potential were performed using the threshold activation foil technique. This technique provides a clear measure of fast neutron flux and with a suitable model, the neutron output. This approach requires little specialized equipment and is used to calibrate real-time neutron detectors and to verify neutron output. We discuss the activation foil measurement technique and describe its use in determining the relative contributions of D-D and D-7Li reactions to the total neutron yield and real-time detector response and compare to model predictions. The D-7Li reaction produces neutrons with a continuum of energies and a sharp peak around 13.5 MeV for measurement techniques outside of what D-D generators can perform. The ability to perform measurements with D-D neutrons alone, then add D-7Li neutrons for inelastic gamma production presents additional measurement modalities with the same neutron source without the use of tritium. Typically, D-T generators are employed for inelastic scattering applications but have a high regulatory burden from a radiological aspect (tritium inventory, liability concerns) and are export-controlled. D-D and D-7Li generators avoid these issues completely.

  18. Ship Effect Neutron Measurements And Impacts On Low-Background Experiments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Siciliano, Edward R.

    2013-10-01

    The primary particles entering the upper atmosphere as cosmic rays create showers in the atmosphere that include a broad spectrum of secondary neutrons, muons and protons. These cosmic-ray secondaries interact with materials at the surface of the Earth, yielding prompt backgrounds in radiation detection systems, as well as inducing long-lived activities through spallation events, dominated by the higher-energy neutron secondaries. For historical reasons, the multiple neutrons produced in spallation cascade events are referred to as “ship effect” neutrons. Quantifying the background from cosmic ray induced activities is important to low-background experiments, such as neutrino-less double beta decay. Since direct measurementsmore » of the effects of shielding on the cosmic-ray neutron spectrum are not available, Monte Carlo modeling is used to compute such effects. However, there are large uncertainties (orders of magnitude) in the possible cross-section libraries and the cosmic-ray neutron spectrum for the energy range needed in such calculations. The measurements reported here were initiated to validate results from Monte Carlo models through experimental measurements in order to provide some confidence in the model results. The results indicate that the models provide the correct trends of neutron production with increasing density, but there is substantial disagreement between the model and experimental results for the lower-density materials of Al, Fe and Cu.« less

  19. ORGANIC SCINTILLATOR FOR REAL-TIME NEUTRON DOSIMETRY.

    PubMed

    Beyer, Kyle A; Di Fulvio, Angela; Stolarczyk, Liliana; Parol, Wiktor; Mojzeszek, Natalia; Kopéc, Renata; Clarke, Shaun D; Pozzi, Sara A

    2017-11-15

    We developed a radiation detector based on an organic scintillator for spectrometry and dosimetry of out-of-field secondary neutrons from clinical proton beams. The detector consists of an EJ-299-34 crystalline organic scintillator, coupled by fiber optic cable to a silicon photomultiplier (SiPM). Proof of concept measurements were taken with 137Cs and 252Cf, and corresponding simulations were performed in MCNPX-PoliMi. Despite its small size, the detector is able to discriminate between neutron and gamma-rays via pulse shape discrimination. We simulated the response function of the detector to monoenergetic neutrons in the 100 keV-0 MeV range using MCNPX-PoliMi. The measured unfolded 252Cf neutron spectrum is in good agreement with the theoretical Watt fission spectrum. We determined the ambient dose equivalent by folding the spectrum with the fluence-to-ambient dose conversion coefficient, with a 1.4% deviation from theory. Some preliminary proton beam experiments were preformed at the Bronowice Cyclotron Center patient treatment facility using a clinically relevant proton pencil beam for brain tumor and craino-spinal treatment directed at a child phantom. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  20. Measurements of the thermal neutron flux for an accelerator-based photoneutron source.

    PubMed

    Taheri, Ali; Pazirandeh, Ali

    2016-12-01

    To have access to an appropriate neutron source is one of the most demanding requirements for neutron studies. This is important specially in laboratory and clinical applications, which need more compact and accessible sources. The most known neutron sources are fission reactors and natural isotopes, but there is an increasing interest for using accelerator based neutron sources because of their advantages. In this paper, we shall present a photo-neutron source prototype which is designed and fabricated to be used for different neutron researches including in-laboratory neutron activation analysis and neutron imaging, and also preliminary studies in boron neutron capture therapy (BNCT). Series of experimental tests were conducted to examine the intensity and quality of the neutron field produced by this source. Monte-Carlo simulations were also utilized to provide more detailed evaluation of the neutron spectrum, and determine the accuracy of the experiments. The experiments demonstrated a thermal neutron flux in the order of 10 7 (n/cm 2 .s), while simulations affirmed this flux and showed a neutron spectrum with a sharp peak at thermal energy region. According to the results, about 60 % of produced neutrons are in the range of thermal to epithermal neutrons.

  1. High-Resolution Fast-Neutron Spectrometry for Arms Control and Treaty Verification

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    David L. Chichester; James T. Johnson; Edward H. Seabury

    2012-07-01

    Many nondestructive nuclear analysis techniques have been developed to support the measurement needs of arms control and treaty verification, including gross photon and neutron counting, low- and high-resolution gamma spectrometry, time-correlated neutron measurements, and photon and neutron imaging. One notable measurement technique that has not been extensively studied to date for these applications is high-resolution fast-neutron spectrometry (HRFNS). Applied for arms control and treaty verification, HRFNS has the potential to serve as a complimentary measurement approach to these other techniques by providing a means to either qualitatively or quantitatively determine the composition and thickness of non-nuclear materials surrounding neutron-emitting materials.more » The technique uses the normally-occurring neutrons present in arms control and treaty verification objects of interest as an internal source of neutrons for performing active-interrogation transmission measurements. Most low-Z nuclei of interest for arms control and treaty verification, including 9Be, 12C, 14N, and 16O, possess fast-neutron resonance features in their absorption cross sections in the 0.5- to 5-MeV energy range. Measuring the selective removal of source neutrons over this energy range, assuming for example a fission-spectrum starting distribution, may be used to estimate the stoichiometric composition of intervening materials between the neutron source and detector. At a simpler level, determination of the emitted fast-neutron spectrum may be used for fingerprinting 'known' assemblies for later use in template-matching tests. As with photon spectrometry, automated analysis of fast-neutron spectra may be performed to support decision making and reporting systems protected behind information barriers. This paper will report recent work at Idaho National Laboratory to explore the feasibility of using HRFNS for arms control and treaty verification applications, including simulations

  2. The Los Alamos Neutron Science Center Spallation Neutron Sources

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

    The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources

  3. The Los Alamos Neutron Science Center Spallation Neutron Sources

    DOE PAGES

    Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

    2017-10-26

    The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources

  4. Experimental determination of the response functions of a Bonner sphere spectrometer to monoenergetic neutrons

    NASA Astrophysics Data System (ADS)

    Hu, Z.; Chen, Z.; Peng, X.; Du, T.; Cui, Z.; Ge, L.; Zhu, W.; Wang, Z.; Zhu, X.; Chen, J.; Zhang, G.; Li, X.; Chen, J.; Zhang, H.; Zhong, G.; Hu, L.; Wan, B.; Gorini, G.; Fan, T.

    2017-06-01

    A Bonner sphere spectrometer (BSS) plays an important role in characterizing neutron spectra and determining their neutron dose in a neutron-gamma mixed field. A BSS consisting of a set of nine polyethylene spheres with a 3He proportional counter was developed at Peking University to perform neutron spectrum and dosimetry measurements. Response functions (RFs) of the BSS were calculated with the general Monte Carlo code MCNP5 for the neutron energy range from thermal up to 20 MeV, and were experimentally calibrated with monoenergetic neutron beams from 144 keV to 14 MeV on a 4.5 MV Van de Graaff accelerator. The calculated RFs were corrected with the experimental values, and the whole response matrix was completely established. The spectrum of a 241Am-Be source was obtained after unfolding the measurement data of the BSS to the source and in fair agreement with the expected one. The integral ambient dose equivalent corresponding to the spectrum was 0.95 of the expected value. Results of the unfolded spectrum and the integral dose equivalent measured by the BSS verified that the RFs of the BSS were well established.

  5. Measurement of the lunar neutron density profile. [Apollo 17 flight

    NASA Technical Reports Server (NTRS)

    Woolum, D. S.; Burnett, D. S.; Furst, M.; Weiss, J. R.

    1974-01-01

    An in situ measurement of the lunar neutron density from 20 to 400 g/sq cm depth between the lunar surface was made by the Apollo 17 Lunar Neutron Probe Experiment using particle tracks produced by the B10(n, alpha)Li7 reaction. Both the absolute magnitude and depth profile of the neutron density are in good agreement with past theoretical calculations. The effect of cadmium absorption on the neutron density and in the relative Sm149 to Gd157 capture rates obtained experimentally implies that the true lunar Gd157 capture rate is about one half of that calculated theoretically.

  6. Simultaneous measurement of absolute strain and differential strain based on fiber Bragg grating Fabry-Perot sensor

    NASA Astrophysics Data System (ADS)

    Wang, Kuiru; Wang, Bo; Yan, Binbin; Sang, Xinzhu; Yuan, Jinhui; Peng, Gang-Ding

    2013-10-01

    We present a fiber Bragg grating Fabry-Perot (FBG-FP) sensor using the fast Fourier transform (FFT) demodulation for measuring the absolute strain and differential strain simultaneously. The amplitude and phase characteristics of Fourier transform spectrum have been studied. The relation between the amplitude of Fourier spectrum and the differential strain has been presented. We fabricate the fiber grating FP cavity sensor, and carry out the experiment on the measurement of absolute strain and differential strain. Experimental results verify the demodulation method, and show that this sensor has a good accuracy in the scope of measurement. The demodulating method can expand the number of multiplexed sensors combining with wavelength division multiplexing and time division multiplexing.

  7. Neutronic experiments with fluorine rich compounds at LR-0 reactor

    DOE PAGES

    Losa, Evzen; Kostal, Michal; Czakoj, T.; ...

    2018-06-06

    Here, research on molten salt reactor (MSR) neutronics continues in Research Centre Rez (Czech Republic) with experimental work being conducted using fluoride salt that was originally used in the Molten Salt Reactor Experiment (MSRE). Previous results identified significant variations in the neutron spectrum measured in LiF-NaF salt. These variations could originate from the fluorine description in current nuclear data sets. Subsequent experiments were performed to try to confirm this phenomenon. Therefore, another fluorine-rich compound, Teflon, was used for testing. Critical experiments showed slight discrepancies in C/E-1 for both compounds, Teflon and FLIBE, and systematic overestimation of criticality was observed inmore » calculations. Different nuclear data libraries were used for data set testing. For Teflon, the overestimation is higher when using JENDL-3.3, JENDL-4, and RUSFOND-2010 libraries, all three of which share the same inelastic-to-elastic scattering cross section ratio. Calculations using other libraries (ENDF/B-VII.1, ENDF/B-VII.0, JEFF-3.2, JEFF-3.1, and CENDL-3.1) tend to be closer to the experimental value. Neutron spectrum measurement in both substances revealed structure similar to that seen in previous measurements using LiF-NaF salt, which indicates that the neutron spectrum seems to be strongly shaped by fluorine. Discrepancies between experimental and calculational results seem to be larger in the neutron energy range of 100–1300 keV than in higher energies. In the case of neutron spectrum calculation, none of the tested libraries gives overall better results than the others.« less

  8. Neutronic experiments with fluorine rich compounds at LR-0 reactor

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Losa, Evzen; Kostal, Michal; Czakoj, T.

    Here, research on molten salt reactor (MSR) neutronics continues in Research Centre Rez (Czech Republic) with experimental work being conducted using fluoride salt that was originally used in the Molten Salt Reactor Experiment (MSRE). Previous results identified significant variations in the neutron spectrum measured in LiF-NaF salt. These variations could originate from the fluorine description in current nuclear data sets. Subsequent experiments were performed to try to confirm this phenomenon. Therefore, another fluorine-rich compound, Teflon, was used for testing. Critical experiments showed slight discrepancies in C/E-1 for both compounds, Teflon and FLIBE, and systematic overestimation of criticality was observed inmore » calculations. Different nuclear data libraries were used for data set testing. For Teflon, the overestimation is higher when using JENDL-3.3, JENDL-4, and RUSFOND-2010 libraries, all three of which share the same inelastic-to-elastic scattering cross section ratio. Calculations using other libraries (ENDF/B-VII.1, ENDF/B-VII.0, JEFF-3.2, JEFF-3.1, and CENDL-3.1) tend to be closer to the experimental value. Neutron spectrum measurement in both substances revealed structure similar to that seen in previous measurements using LiF-NaF salt, which indicates that the neutron spectrum seems to be strongly shaped by fluorine. Discrepancies between experimental and calculational results seem to be larger in the neutron energy range of 100–1300 keV than in higher energies. In the case of neutron spectrum calculation, none of the tested libraries gives overall better results than the others.« less

  9. Method and apparatus for determination of temperature, neutron absorption cross section and neutron moderating power

    DOEpatents

    Vagelatos, Nicholas; Steinman, Donald K.; John, Joseph; Young, Jack C.

    1981-01-01

    A nuclear method and apparatus determines the temperature of a medium by injecting fast neutrons into the medium and detecting returning slow neutrons in three first energy ranges by producing three respective detection signals. The detection signals are combined to produce three derived indicia each systematically related to the population of slow neutrons returning from the medium in a respective one of three second energy ranges, specifically exclusively epithermal neutrons, exclusively substantially all thermal neutrons and exclusively a portion of the thermal neutron spectrum. The derived indicia are compared with calibration indicia similarly systematically related to the population of slow neutrons in the same three second energy ranges returning from similarly irradiated calibration media for which the relationships temperature, neutron absorption cross section and neutron moderating power to such calibration indicia are known. The comparison indicates the temperature at which the calibration indicia correspond to the derived indicia and consequently the temperature of the medium. The neutron absorption cross section and moderating power of the medium can be identified at the same time.

  10. Chemical composition of French mimosa absolute oil.

    PubMed

    Perriot, Rodolphe; Breme, Katharina; Meierhenrich, Uwe J; Carenini, Elise; Ferrando, Georges; Baldovini, Nicolas

    2010-02-10

    Since decades mimosa (Acacia dealbata) absolute oil has been used in the flavor and perfume industry. Today, it finds an application in over 80 perfumes, and its worldwide industrial production is estimated five tons per year. Here we report on the chemical composition of French mimosa absolute oil. Straight-chain analogues from C6 to C26 with different functional groups (hydrocarbons, esters, aldehydes, diethyl acetals, alcohols, and ketones) were identified in the volatile fraction. Most of them are long-chain molecules: (Z)-heptadec-8-ene, heptadecane, nonadecane, and palmitic acid are the most abundant, and constituents such as 2-phenethyl alcohol, methyl anisate, and ethyl palmitate are present in smaller amounts. The heavier constituents were mainly triterpenoids such as lupenone and lupeol, which were identified as two of the main components. (Z)-Heptadec-8-ene, lupenone, and lupeol were quantified by GC-MS in SIM mode using external standards and represents 6%, 20%, and 7.8% (w/w) of the absolute oil. Moreover, odorant compounds were extracted by SPME and analyzed by GC-sniffing leading to the perception of 57 odorant zones, of which 37 compounds were identified by their odorant description, mass spectrum, retention index, and injection of the reference compound.

  11. Prompt fission neutron spectra of actinides

    DOE PAGES

    Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; ...

    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.

  12. Non-destructive method for determining neutron exposure and constituent concentrations of a body

    DOEpatents

    Gold, Raymond; McElroy, William N.

    1986-01-01

    A non-destructive method for determination of neutron exposure and constituent concentrations in an object, such as reactor pressure vessel, is based on the observation of characteristic gamma-rays emitted by activation products in the object by using a unique continuous gamma-ray spectrometer. The spectrometer views the object through appropriate collimators to determine the absolute emission rate of these characteristic gamma-rays, thereby ascertaining the absolute activity of given activation products in the object. These data can then be used to deduce the spatial and angular dependence of neutron exposure or the spatial constituent concentration at regions of interest within the object.

  13. Calibration of LiBaF3: Ce Scintillator for Fission Spectrum Neutrons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Reeder, Paul L.; Bowyer, Sonya M.

    2002-05-21

    The scintillator LiBaF3 doped with small amounts of Ce+3 has the ability to distinguish heavy charged particles (p, d, t, or a) from beta and/or gamma radiation based on the presence or absence of ns components in the scintillation light output. Because the neutron capture reaction on 6Li produces recoil alphas and tritons, this scintillator also discriminates between neutron induced events and beta or gamma interactions. An experimental technique using a time-tagged 252Cf source has been used to measure the efficiency of this scintillator for neutron capture, the calibration of neutron capture pulse height, and the pulse height resolution -more » all as a function of incident neutron energy.« less

  14. Determination of the Secondary Neutron Flux at the Massive Natural Uranium Spallation Target

    NASA Astrophysics Data System (ADS)

    Zeman, M.; Adam, J.; Baldin, A. A.; Furman, W. I.; Gustov, S. A.; Katovsky, K.; Khushvaktov, J.; Mar`in, I. I.; Novotny, F.; Solnyshkin, A. A.; Tichy, P.; Tsoupko-Sitnikov, V. M.; Tyutyunnikov, S. I.; Vespalec, R.; Vrzalova, J.; Wagner, V.; Zavorka, L.

    The flux of secondary neutrons generated in collisions of the 660 MeV proton beam with the massive natural uranium spallation target was investigated using a set of monoisotopic threshold activation detectors. Sandwiches made of thin high-purity Al, Co, Au, and Bi metal foils were installed in different positions across the whole spallation target. The gamma-ray activity of products of (n,xn) and other studied reactions was measured offline with germanium semiconductor detectors. Reaction yields of radionuclides with half-life exceeding 100 min and with effective neutron energy thresholds between 3.6 MeV and 186 MeV provided us with information about the spectrum of spallation neutrons in this energy region and beyond. The experimental neutron flux was determined using the measured reaction yields and cross-sections calculated with the TALYS 1.8 nuclear reaction program and INCL4-ABLA event generator of MCNP6. Neutron spectra in the region of activation sandwiches were also modeled with the radiation transport code MCNPX 2.7. Neutron flux based on excitation functions from TALYS provides a reasonable description of the neutron spectrum inside the spallation target and is in good agreement with Monte-Carlo predictions. The experimental flux that uses INCL4 cross-sections rather underestimates the modeled spectrum in the whole region of interest, but the agreement within few standard deviations was reached as well. The paper summarizes basic principles of the method for determining the spectrum of high-energy neutrons without employing the spectral adjustment routines and points out to the need for model improvements and precise cross-section measurements.

  15. Computational Transport Modeling of High-Energy Neutrons Found in the Space Environment

    NASA Technical Reports Server (NTRS)

    Cox, Brad; Theriot, Corey A.; Rohde, Larry H.; Wu, Honglu

    2012-01-01

    The high charge and high energy (HZE) particle radiation environment in space interacts with spacecraft materials and the human body to create a population of neutrons encompassing a broad kinetic energy spectrum. As an HZE ion penetrates matter, there is an increasing chance of fragmentation as penetration depth increases. When an ion fragments, secondary neutrons are released with velocities up to that of the primary ion, giving some neutrons very long penetration ranges. These secondary neutrons have a high relative biological effectiveness, are difficult to effectively shield, and can cause more biological damage than the primary ions in some scenarios. Ground-based irradiation experiments that simulate the space radiation environment must account for this spectrum of neutrons. Using the Particle and Heavy Ion Transport Code System (PHITS), it is possible to simulate a neutron environment that is characteristic of that found in spaceflight. Considering neutron dosimetry, the focus lies on the broad spectrum of recoil protons that are produced in biological targets. In a biological target, dose at a certain penetration depth is primarily dependent upon recoil proton tracks. The PHITS code can be used to simulate a broad-energy neutron spectrum traversing biological targets, and it account for the recoil particle population. This project focuses on modeling a neutron beamline irradiation scenario for determining dose at increasing depth in water targets. Energy-deposition events and particle fluence can be simulated by establishing cross-sectional scoring routines at different depths in a target. This type of model is useful for correlating theoretical data with actual beamline radiobiology experiments. Other work exposed human fibroblast cells to a high-energy neutron source to study micronuclei induction in cells at increasing depth behind water shielding. Those findings provide supporting data describing dose vs. depth across a water-equivalent medium. This

  16. System and method for delivery of neutron beams for medical therapy

    DOEpatents

    Nigg, David W.; Wemple, Charles A.

    1999-01-01

    A neutron delivery system that provides improved capability for tumor control during medical therapy. The system creates a unique neutron beam that has a bimodal or multi-modal energy spectrum. This unique neutron beam can be used for fast-neutron therapy, boron neutron capture therapy (BNCT), or both. The invention includes both an apparatus and a method for accomplishing the purposes of the invention.

  17. Feasibility of the Precise Energy Calibration for Fast Neutron Spectrometers

    NASA Astrophysics Data System (ADS)

    Gaganov, V. V.; Usenko, P. L.; Kryzhanovskaja, M. A.

    2017-12-01

    Computational studies aimed at improving the accuracy of measurements performed using neutron generators with a tritium target were performed. A measurement design yielding an extremely narrow peak in the energy spectrum of DT neutrons was found. The presence of such a peak establishes the conditions for precise energy calibration of fast-neutron spectrometers.

  18. Detection of fast neutrons from shielded nuclear materials using a semiconductor alpha detector.

    PubMed

    Pöllänen, R; Siiskonen, T

    2014-08-01

    The response of a semiconductor alpha detector to fast (>1 MeV) neutrons was investigated by using measurements and simulations. A polyethylene converter was placed in front of the detector to register recoil protons generated by elastic collisions between neutrons and hydrogen nuclei of the converter. The developed prototype equipment was tested with shielded radiation sources. The low background of the detector and insensitivity to high-energy gamma rays above 1 MeV are advantages when the detection of neutron-emitting nuclear materials is of importance. In the case of a (252)Cf neutron spectrum, the intrinsic efficiency of fast neutron detection was determined to be 2.5×10(-4), whereas three-fold greater efficiency was obtained for a (241)AmBe neutron spectrum. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Feasibility of the Utilization of BNCT in the Fast Neutron Therapy Beam at Fermilab

    DOE R&D Accomplishments Database

    Langen, Katja; Lennox, Arlene J.; Kroc, Thomas K.; DeLuca, Jr., Paul M.

    2000-06-01

    The Neutron Therapy Facility at Fermilab has treated cancer patients since 1976. Since then more than 2,300 patients have been treated and a wealth of clinical information accumulated. The therapeutic neutron beam at Fermilab is produced by bombarding a beryllium target with 66 MeV protons. The resulting continuous neutron spectrum ranges from thermal to 66 MeV in neutron energy. It is clear that this spectrum is not well suited for the treatment of tumors with boron neutron capture therapy (BNCT) only However, since this spectrum contains thermal and epithermal components the authors are investigating whether BNCT can be used in this beam to boost the tumor dose. There are clinical scenarios in which a selective tumor dose boost of 10 - 15% could be clinically significant. For these cases the principal treatment would still be fast neutron therapy but a tumor boost could be used either to deliver a higher dose to the tumor tissue or to reduce the dose to the normal healthy tissue while maintaining the absorbed dose level in the tumor tissue.

  20. System and method for delivery of neutron beams for medical therapy

    DOEpatents

    Nigg, D.W.; Wemple, C.A.

    1999-07-06

    A neutron delivery system that provides improved capability for tumor control during medical therapy is disclosed. The system creates a unique neutron beam that has a bimodal or multi-modal energy spectrum. This unique neutron beam can be used for fast-neutron therapy, boron neutron capture therapy (BNCT), or both. The invention includes both an apparatus and a method for accomplishing the purposes of the invention. 5 figs.

  1. Characterization of emergent leakage neutrons from multiple layers of hydrogen/water in the lunar regolith by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    SU, J.; Sagdeev, R.; Usikov, D.; Chin, G.; Boyer, L.; Livengood, T. A.; McClanahan, T. P.; Murray, J.; Starr, R. D.

    2013-12-01

    Introduction: The leakage flux of lunar neutrons produced by precipitation of galactic cosmic ray (GCR) particles in the upper layer of the lunar regolith and measured by orbital instruments such as the Lunar Exploration Neutron Detector (LEND) is investigated by Monte Carlo simulation. Previous Monte Carlo (MC) simulations have been used to investigate neutron production and leakage from the lunar surface to assess the elemental composition of lunar soil [1-6] and its effect on the leakage neutron flux. We investigate effects on the emergent flux that depend on the physical distribution of hydrogen within the regolith. We use the software package GEANT4 [7] to calculate neutron production from spallation by GCR particles [8,9] in the lunar soil. Multiple layers of differing hydrogen/water at different depths in the lunar regolith model are introduced to examine enhancement or suppression of leakage neutron flux. We find that the majority of leakage thermal and epithermal neutrons are produced in 25 cm to 75 cm deep from the lunar surface. Neutrons produced in the shallow top layer retain more of their original energy due to fewer scattering interactions and escape from the lunar surface mostly as fast neutrons. This provides a diagnostic tool in interpreting leakage neutron flux enhancement or suppression due to hydrogen concentration distribution in lunar regolith. We also find that the emitting angular distribution of thermal and epithermal leakage neutrons can be described by cos3/2(theta) where the fast neutrons emitting angular distribution is cos(theta). The energy sensitivity and angular response of the LEND detectors SETN and CSETN are investigated using the leakage neutron spectrum from GEANT4 simulations. A simplified LRO model is used to benchmark MCNPX[10] and GEANT4 on CSETN absolute count rate corresponding to neutron flux from bombardment of 120MV solar potential GCR particles on FAN lunar soil. We are able to interpret the count rates of SETN and

  2. Fission Product Yields of 233U, 235U, 238U and 239Pu in Fields of Thermal Neutrons, Fission Neutrons and 14.7-MeV Neutrons

    NASA Astrophysics Data System (ADS)

    Laurec, J.; Adam, A.; de Bruyne, T.; Bauge, E.; Granier, T.; Aupiais, J.; Bersillon, O.; Le Petit, G.; Authier, N.; Casoli, P.

    2010-12-01

    The yields of more than fifteen fission products have been carefully measured using radiochemical techniques, for 235U(n,f), 239Pu(n,f) in a thermal spectrum, for 233U(n,f), 235U(n,f), and 239Pu(n,f) reactions in a fission neutron spectrum, and for 233U(n,f), 235U(n,f), 238U(n,f), and 239Pu(n,f) for 14.7 MeV monoenergetic neutrons. Irradiations were performed at the EL3 reactor, at the Caliban and Prospero critical assemblies, and at the Lancelot electrostatic accelerator in CEA-Valduc. Fissions were counted in thin deposits using fission ionization chambers. The number of fission products of each species were measured by gamma spectrometry of co-located thick deposits.

  3. Evaluation of the ²³⁹Pu prompt fission neutron spectrum induced by neutrons of 500 keV and associated covariances

    DOE PAGES

    Neudecker, D.; Talou, P.; Kawano, T.; ...

    2015-08-01

    We present evaluations of the prompt fission neutron spectrum (PFNS) of ²³⁹Pu induced by 500 keV neutrons, and associated covariances. In a previous evaluation by Talou et al. 2010, surprisingly low evaluated uncertainties were obtained, partly due to simplifying assumptions in the quantification of uncertainties from experiment and model. Therefore, special emphasis is placed here on a thorough uncertainty quantification of experimental data and of the Los Alamos model predicted values entering the evaluation. In addition, the Los Alamos model was extended and an evaluation technique was employed that takes into account the qualitative differences between normalized model predicted valuesmore » and experimental shape data. These improvements lead to changes in the evaluated PFNS and overall larger evaluated uncertainties than in the previous work. However, these evaluated uncertainties are still smaller than those obtained in a statistical analysis using experimental information only, due to strong model correlations. Hence, suggestions to estimate model defect uncertainties are presented, which lead to more reasonable evaluated uncertainties. The calculated k eff of selected criticality benchmarks obtained with these new evaluations agree with each other within their uncertainties despite the different approaches to estimate model defect uncertainties. The k eff one standard deviations overlap with some of those obtained using ENDF/B-VII.1, albeit their mean values are further away from unity. Spectral indexes for the Jezebel critical assembly calculated with the newly evaluated PFNS agree with the experimental data for selected (n,γ) and (n,f) reactions, and show improvements for high-energy threshold (n,2n) reactions compared to ENDF/B-VII.1.« less

  4. Non-destructive method for determining neutron exposure and constituent concentrations of a body

    DOEpatents

    Gold, R.; McElroy, W.N.

    1984-02-22

    A non-destructive method for determination of neutron exposure and constituent concentrations in an object, such as a reactor pressure vessel, is based on the observation of characteristic gamma-rays emitted by activation products in the object by using a unique continuous gamma-ray spectrometer. The spectrometer views the object through appropriate collimators to determine the absolute emission rate of these characteristic gamma-rays, thereby ascertaining the absolute activity of given activation products in the object. These data can then be used to deduce the spatial and angular dependence of neutron exposure or the spatial constituent concentrations at regions of interest within the object.

  5. Fast neutron irradiation tests of flash memories used in space environment at the ISIS spallation neutron source

    NASA Astrophysics Data System (ADS)

    Andreani, C.; Senesi, R.; Paccagnella, A.; Bagatin, M.; Gerardin, S.; Cazzaniga, C.; Frost, C. D.; Picozza, P.; Gorini, G.; Mancini, R.; Sarno, M.

    2018-02-01

    This paper presents a neutron accelerated study of soft errors in advanced electronic devices used in space missions, i.e. Flash memories performed at the ChipIr and VESUVIO beam lines at the ISIS spallation neutron source. The two neutron beam lines are set up to mimic the space environment spectra and allow neutron irradiation tests on Flash memories in the neutron energy range above 10 MeV and up to 800 MeV. The ISIS neutron energy spectrum is similar to the one occurring in the atmospheric as well as in space and planetary environments, with intensity enhancements varying in the range 108- 10 9 and 106- 10 7 respectively. Such conditions are suitable for the characterization of the atmospheric, space and planetary neutron radiation environments, and are directly applicable for accelerated tests of electronic components as demonstrated here in benchmark measurements performed on flash memories.

  6. A comparative study of neutron activation analysis and proton-induced X-ray emission analysis for the determination of heavy metals in estuarine sediments

    NASA Astrophysics Data System (ADS)

    Randle, K.; Al-Jundi, J.; Mamas, C. J. V.; Sokhi, R. S.; Earwaker, L. G.

    1993-06-01

    Our work on heavy metals in the estuarine environment has involved the use of two multielement techniques: neutron activation analysis (NAA) and proton-induced X-ray emission (PIXE) analysis. As PIXE is essentially a surface analytical technique problems may arise due to sample inhomogeneity and surface roughness. In order to assess the contribution of these effects we have compared the results from PIXE analysis with those from a technique which analyzes a larger bulk sample rather than just the surface. An obvious method was NAA. A series of sediment samples containing particles of variable diameter were compared. Pellets containing a few mg of sediment were prepared from each sample and analyzed by the PIXE technique using both an absolute and a comparitive method. For INAA the rest of the sample was then irradiated with thermal neutrons and element concentrations determined from analyses of the subsequent gamma-ray spectrum. Results from the two methods are discussed.

  7. Neutron Spectroscopy for pulsed beams with frame overlap using a double time-of-flight technique

    NASA Astrophysics Data System (ADS)

    Harrig, K. P.; Goldblum, B. L.; Brown, J. A.; Bleuel, D. L.; Bernstein, L. A.; Bevins, J.; Harasty, M.; Laplace, T. A.; Matthews, E. F.

    2018-01-01

    A new double time-of-flight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron detection efficiency of the scintillator array was performed using both GEANT4 and MCNP6. The efficiency-corrected spectral shape was normalized using a foil activation technique to obtain the energy-dependent flux of the neutron beam at zero degrees with respect to the incoming deuteron beam. The dTOF neutron spectrum was compared to spectra obtained using HEPROW and GRAVEL pulse height spectrum unfolding techniques. While the unfolding and dTOF results exhibit some discrepancies in shape, the integrated flux values agree within two standard deviations. This method obviates neutron time-of-flight spectroscopy challenges posed by pulsed beams with frame overlap and opens new opportunities for pulsed white neutron source facilities.

  8. On the angular and energy distribution of solar neutrons generated in P-P reactions

    NASA Technical Reports Server (NTRS)

    Efimov, Y. E.; Kocharov, G. E.

    1985-01-01

    The problem of high energy neutron generation in P-P reactions in the solar atmosphere is reconsidered. It is shown that the angular distribution of emitted neutrons is anisotropic and the energy spectrum of neutrons depends on the angle of neutron emission.

  9. Prenatal Valproate Exposure and Risk of Autism Spectrum Disorders and Childhood Autism

    PubMed Central

    Christensen, Jakob; Grønborg, Therese Koops; Sørensen, Merete Juul; Schendel, Diana; Parner, Erik Thorlund; Pedersen, Lars Henning; Vestergaard, Mogens

    2015-01-01

    Importance Valproate is used for the treatment of epilepsy and other neuropsychological disorders and may be the only treatment option for women of childbearing potential. However, prenatal exposure to valproate may increase the risk of autism. Objective To determine whether prenatal exposure to valproate is associated with an increased risk of autism in offspring. Design, Setting, and Participants Population-based study of all children born alive in Denmark from 1996 to 2006. National registers were used to identify children exposed to valproate during pregnancy and diagnosed with autism spectrum disorders (childhood autism [autistic disorder], Asperger syndrome, atypical autism, and other or unspecified pervasive developmental disorders). We analyzed the risks associated with all autism spectrum disorders as well as childhood autism. Data were analyzed by Cox regression adjusting for potential confounders (maternal age at conception, paternal age at conception, parental psychiatric history, gestational age, birth weight, sex, congenital malformations, and parity). Children were followed up from birth until the day of autism spectrum disorder diagnosis, death, emigration, or December 31, 2010, whichever came first. Main Outcomes and Measures Absolute risk (cumulative incidence) and the hazard ratio (HR) of autism spectrum disorder and childhood autism in children after exposure to valproate in pregnancy. Results Of 655 615 children born from 1996 through 2006, 5437 were identified with autism spectrum disorder, including 2067 with childhood autism. The mean age of the children at end of follow-up was 8.84 years (range, 4-14; median, 8.85). The estimated absolute risk after 14 years of follow-up was 1.53% (95% CI, 1.47%- 1.58%) for autism spectrum disorder and 0.48% (95% CI, 0.46%-0.51%) for childhood autism. Overall, the 508 children exposed to valproate had an absolute risk of 4.42% (95% CI, 2.59%-7.46%) for autism spectrum disorder (adjusted HR, 2.9 [95% CI, 1

  10. An absolute sodium abundance for a cloud-free 'hot Saturn' exoplanet.

    PubMed

    Nikolov, N; Sing, D K; Fortney, J J; Goyal, J M; Drummond, B; Evans, T M; Gibson, N P; De Mooij, E J W; Rustamkulov, Z; Wakeford, H R; Smalley, B; Burgasser, A J; Hellier, C; Helling, Ch; Mayne, N J; Madhusudhan, N; Kataria, T; Baines, J; Carter, A L; Ballester, G E; Barstow, J K; McCleery, J; Spake, J J

    2018-05-01

    Broad absorption signatures from alkali metals, such as the sodium (Na I) and potassium (K I) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets 1-3 . However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles 4-6 . Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances 7-9 . Here we report an optical transmission spectrum for the 'hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logε Na  = [Formula: see text], and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Z p /Z ʘ  = [Formula: see text]). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets 10-12 .

  11. An absolute sodium abundance for a cloud-free `hot Saturn' exoplanet

    NASA Astrophysics Data System (ADS)

    Nikolov, N.; Sing, D. K.; Fortney, J. J.; Goyal, J. M.; Drummond, B.; Evans, T. M.; Gibson, N. P.; De Mooij, E. J. W.; Rustamkulov, Z.; Wakeford, H. R.; Smalley, B.; Burgasser, A. J.; Hellier, C.; Helling, Ch.; Mayne, N. J.; Madhusudhan, N.; Kataria, T.; Baines, J.; Carter, A. L.; Ballester, G. E.; Barstow, J. K.; McCleery, J.; Spake, J. J.

    2018-05-01

    Broad absorption signatures from alkali metals, such as the sodium (Na i) and potassium (K i) resonance doublets, have long been predicted in the optical atmospheric spectra of cloud-free irradiated gas giant exoplanets1-3. However, observations have revealed only the narrow cores of these features rather than the full pressure-broadened profiles4-6. Cloud and haze opacity at the day-night planetary terminator are considered to be responsible for obscuring the absorption-line wings, which hinders constraints on absolute atmospheric abundances7-9. Here we report an optical transmission spectrum for the `hot Saturn' exoplanet WASP-96b obtained with the Very Large Telescope, which exhibits the complete pressure-broadened profile of the sodium absorption feature. The spectrum is in excellent agreement with cloud-free, solar-abundance models assuming chemical equilibrium. We are able to measure a precise, absolute sodium abundance of logɛNa = 6.9-0.4+0.6, and use it as a proxy for the planet's atmospheric metallicity relative to the solar value (Zp/Zʘ = 2.3-1.7+8.9). This result is consistent with the mass-metallicity trend observed for Solar System planets and exoplanets10-12.

  12. Investigation of neutron interactions with Ge detectors

    NASA Astrophysics Data System (ADS)

    Baginova, Miloslava; Vojtyla, Pavol; Povinec, Pavel P.

    2018-07-01

    Interactions of neutrons with a high-purity germanium detector were studied experimentally and by simulations using the GEANT4 tool. Elastic and inelastic scattering of fast neutrons as well as neutron capture on Ge nuclei were observed. Peaks induced by inelastic scattering of neutrons on 70Ge, 72Ge, 73Ge, 74Ge and 76Ge were well visible in the γ-ray spectra. In addition, peaks due to inelastic scattering of neutrons on copper and lead nuclei, including the well-known peak of 208Pb at 2614.51 keV, were detected. The GEANT4 simulations showed that the simulated spectrum was in a good agreement with the experimental one. Differences between the simulated and the measured spectra were due to the high γ-ray intensity of the used neutron source, physics implemented in GEANT4 and contamination of the neutron source.

  13. Accidental neutron dosimetry with human hair

    NASA Astrophysics Data System (ADS)

    Ekendahl, Daniela; Bečková, Věra; Zdychová, Vlasta; Bulánek, Boris; Prouza, Zdeněk; Štefánik, Milan

    2014-11-01

    Human hair contains sulfur, which can be activated by fast neutrons. The 32S(n,p)32P reaction with a threshold of 2.5 MeV was used for fast neutron dose estimation. It is a very important parameter for individual dose reconstruction with regards to the heterogeneity of the neutron transfer to the human body. Samples of human hair were irradiated in a radial channel of a training reactor VR-1. 32P activity in hair was measured both, directly by means of a proportional counter, and as ash dispersed in a liquid scintillator. Based on neutron spectrum estimation, a relationship between the neutron dose and induced activity was derived. The experiment verified the practical feasibility of this dosimetry method in cases of criticality accidents or malevolent acts with nuclear materials.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Pozzi, Sara; Czirr, J. Bart; Haight, Robert

    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 bothmore » 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).« less

  15. Absolute neutrino mass measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wolf, Joachim

    2011-10-06

    The neutrino mass plays an important role in particle physics, astrophysics and cosmology. In recent years the detection of neutrino flavour oscillations proved that neutrinos carry mass. However, oscillation experiments are only sensitive to the mass-squared difference of the mass eigenvalues. In contrast to cosmological observations and neutrino-less double beta decay (0v2{beta}) searches, single {beta}-decay experiments provide a direct, model-independent way to determine the absolute neutrino mass by measuring the energy spectrum of decay electrons at the endpoint region with high accuracy.Currently the best kinematic upper limits on the neutrino mass of 2.2eV have been set by two experiments inmore » Mainz and Troitsk, using tritium as beta emitter. The next generation tritium {beta}-experiment KATRIN is currently under construction in Karlsruhe/Germany by an international collaboration. KATRIN intends to improve the sensitivity by one order of magnitude to 0.2eV. The investigation of a second isotope ({sup 137}Rh) is being pursued by the international MARE collaboration using micro-calorimeters to measure the beta spectrum. The technology needed to reach 0.2eV sensitivity is still in the R and D phase. This paper reviews the present status of neutrino-mass measurements with cosmological data, 0v2{beta} decay and single {beta}-decay.« less

  16. Towards an In-Beam Measurement of the Neutron Lifetime to 1 Second

    NASA Astrophysics Data System (ADS)

    Mulholland, Jonathan

    2014-03-01

    A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is an essential parameter in the theory of Big Bang Nucleosynthesis. A new measurement of the neutron lifetime using the in-beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. The systematic effects associated with the in-beam method are markedly different than those found in storage experiments utilizing ultracold neutrons. Experimental improvements, specifically recent advances in the determination of absolute neutron fluence, should permit an overall uncertainty of 1 second on the neutron lifetime. The dependence of the primordial mass fraction on the neutron lifetime, technical improvements of the in-beam technique, and the path toward improving the precision of the new measurement will be discussed.

  17. DESCANT and β-delayed neutron measurements at TRIUMF

    NASA Astrophysics Data System (ADS)

    Bildstein, V.; Garrett, P. E.; Ashley, S. F.; Ball, G. C.; Bianco, L.; Bandyopadhyay, D.; Bangay, J.; Crider, B. P.; Demand, G.; Deng, G.; Dillmann, I.; Finlay, A.; Garnsworthy, A. B.; Hackman, G.; Hadinia, B.; Krücken, R.; Leach, K. G.; Martin, J.-P.; McEllistrem, M. T.; Pearson, C. J.; Peters, E. E.; Prados-Estévez, F. M.; Radich, A.; Sarazin, F.; Sumithrarachchi, C.; Svensson, C. E.; Vanhoy, J. R.; Wong, J.; Yates, S. W.

    2015-05-01

    The DESCANT array (Deuterated Scintillator Array for Neutron Tagging) consists of up to 70 detectors, each filled with approximately 2 liters of deuterated benzene. This scintillator material o_ers pulse-shape discrimination (PSD) capabilities to distinguish between neutrons and γ-rays interacting with the scintillator material. In addition, the anisotropic nature of n - d scattering allows for the determination of the neutron energy spectrum directly from the pulse height spectrum, complementing the traditional time-of-flight (ToF) information. DESCANT can be coupled either to the TIGRESS (TRIUMF-ISAC Gamma-Ray Escape Suppressed Spectrometer) γ-ray spectrometer [1] located in the ISAC-II [2] hall of TRIUMF for in-beam experiments, or to the GRIFFIN (Gamma-Ray Infrastructure For Fundamental Investigations of Nuclei) γ-ray spectrometer [3] located in the ISAC-I hall of TRIUMF for decay spectroscopy experiments.

  18. Neutron spectroscopy for pulsed beams with frame overlap using a double time-of-flight technique

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Harrig, K. P.; Goldblum, B. L.; Brown, J. A.

    A new double time-of- ight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron detection efficiency of the scintillator array was performedmore » using both GEANT4 and MCNP6. The efficiency- corrected spectral shape was normalized using a foil activation technique to obtain the energy-dependent flux of the neutron beam at zero degrees with respect to the incoming deuteron beam. The dTOF neutron spectrum was compared to spectra obtained using HEPROW and GRAVEL pulse height spectrum unfolding techniques. While the unfolding and dTOF results exhibit some discrepancies in shape, the integrated flux values agree within two standard deviations. As a result, this method obviates neutron time-of-flight spectroscopy challenges posed by pulsed beams« less

  19. Neutron spectroscopy for pulsed beams with frame overlap using a double time-of-flight technique

    DOE PAGES

    Harrig, K. P.; Goldblum, B. L.; Brown, J. A.; ...

    2017-10-16

    A new double time-of- ight (dTOF) neutron spectroscopy technique has been developed for pulsed broad spectrum sources with a duty cycle that results in frame overlap, where fast neutrons from a given pulse overtake slower neutrons from previous pulses. Using a tunable beam at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory, neutrons were produced via thick-target breakup of 16 MeV deuterons on a beryllium target in the cyclotron vault. The breakup spectral shape was deduced from a dTOF measurement using an array of EJ-309 organic liquid scintillators. Simulation of the neutron detection efficiency of the scintillator array was performedmore » using both GEANT4 and MCNP6. The efficiency- corrected spectral shape was normalized using a foil activation technique to obtain the energy-dependent flux of the neutron beam at zero degrees with respect to the incoming deuteron beam. The dTOF neutron spectrum was compared to spectra obtained using HEPROW and GRAVEL pulse height spectrum unfolding techniques. While the unfolding and dTOF results exhibit some discrepancies in shape, the integrated flux values agree within two standard deviations. As a result, this method obviates neutron time-of-flight spectroscopy challenges posed by pulsed beams« less

  20. Solid state structure and absolute configuration of filifolinol acetate.

    PubMed

    Muñoz, Marcelo A; Urzúa, Alejandro; Echeverría, Javier; Modak, Brenda; Joseph-Nathan, Pedro

    2011-06-01

    Careful reevaluation of the 1H and 13C NMR spectroscopic data of filifolinol acetate (4) led to the reassignment of the C-10 and C-11 signals, as well as the gem-dimethyl signals. Single crystal X-ray analysis provided an independent structural confirmation of 4, and comparison of the experimental vibrational circular dichroism spectrum with calculations performed using density functional theory provided the absolute configuration of this 3H-spiro-1-benzofuran-2,1'-cyclohexane and related molecules.

  1. Improved determination of the neutron lifetime.

    PubMed

    Yue, A T; Dewey, M S; Gilliam, D M; Greene, G L; Laptev, A B; Nico, J S; Snow, W M; Wietfeldt, F E

    2013-11-27

    The most precise determination of the neutron lifetime using the beam method was completed in 2005 and reported a result of τ(n)=(886.3±1.2[stat]±3.2[syst]) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was measured with a neutron monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the evaluated nuclear data file, ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. In the current work, we measure the detection efficiency of the same monitor used in the neutron lifetime measurement with a second, totally absorbing neutron detector. This direct approach does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The detection efficiency is consistent with the value used in 2005 but is measured with a precision of 0.057%, which represents a fivefold improvement in the uncertainty. We verify the temporal stability of the neutron monitor through ancillary measurements, allowing us to apply the measured neutron monitor efficiency to the lifetime result from the 2005 experiment. The updated lifetime is τ(n)=(887.7±1.2[stat]±1.9[syst]) s.

  2. Absolute near-infrared refractometry with a calibrated tilted fiber Bragg grating.

    PubMed

    Zhou, Wenjun; Mandia, David J; Barry, Seán T; Albert, Jacques

    2015-04-15

    The absolute refractive indices (RIs) of water and other liquids are determined with an uncertainty of ±0.001 at near-infrared wavelengths by using the tilted fiber Bragg grating (TFBG) cladding mode resonances of a standard single-mode fiber to measure the critical angle for total internal reflection at the interface between the fiber and its surroundings. The necessary condition to obtain absolute RIs (instead of measuring RI changes) is a thorough characterization of the dispersion of the core mode effective index of the TFBG across the full range of its cladding mode resonance spectrum. This technique is shown to be competitive with the best available measurements of the RIs of water and NaCl solutions at wavelengths in the vicinity of 1550 nm.

  3. Assay of the Martian Regolith with Neutrons

    NASA Technical Reports Server (NTRS)

    Drake, Darrell M.

    1997-01-01

    The purpose of the research is to combine experiments and Monte Carlo transport of neutrons through volume of soil in an attempt to model neutron leakage from planetary surfaces. Emphasis is given to the change of neutron spectra as a function of water content and location. During the first stage of effort, two experiments were conducted in which leakage of neutrons from a Pu-Be source through about 30 g/cm(exp 2) of soil were measured with several counters. A Monte Carlo code, MCNP, has been used to model many of the 100 individual runs of the experiment. Hydrogen is the element that has the most dramatic effect on the neutron spectrum and its effect on the neutron spectrum is almost the same whether it is in the form of water or polyethylene. In order to simulate various water configurations, sheets of polyethylene have been used between layers of soil as well as water in several concentrations up to 18%. Comparison of experimental results to theoretical predictions made with the MCNP code were disappointing for low concentrations of water. We have made extensive calculations to see if room return could be the cause of the discrepancies. Water concentrations of the 'dry' soil were measured by two different laboratories and differed only by 0.5%. We have made calculations to optimize the next experiment and are investigating other methods of determining the water content of 'dry' soil.

  4. Accelerator driven neutron source design via beryllium target and 208Pb moderator for boron neutron capture therapy in alternative treatment strategy by Monte Carlo method.

    PubMed

    Khorshidi, Abdollah

    2017-01-01

    The reactor has increased its area of application into medicine especially boron neutron capture therapy (BNCT); however, accelerator-driven neutron sources can be used for therapy purposes. The present study aimed to discuss an alternative method in BNCT functions by a small cyclotron with low current protons based on Karaj cyclotron in Iran. An epithermal neutron spectrum generator was simulated with 30 MeV proton energy for BNCT purposes. A low current of 300 μA of the proton beam in spallation target concept via 9Be target was accomplished to model neutron spectrum using 208Pb moderator around the target. The graphite reflector and dual layer collimator were planned to prevent and collimate the neutrons produced from proton interactions. Neutron yield per proton, energy distribution, flux, and dose components in the simulated head phantom were estimated by MCNPX code. The neutron beam quality was investigated by diverse filters thicknesses. The maximum epithermal flux transpired using Fluental, Fe, Li, and Bi filters with thicknesses of 7.4, 3, 0.5, and 4 cm, respectively; as well as the epithermal to thermal neutron flux ratio was 161. Results demonstrated that the induced neutrons from a low energy and low current proton may be effective in tumor therapy using 208Pb moderator with average lethargy and also graphite reflector with low absorption cross section to keep the generated neutrons. Combination of spallation-based BNCT and proton therapy can be especially effective, if a high beam intensity cyclotron becomes available.

  5. SU-E-T-168: Characterization of Neutrons From the TrueBeam Treatment Head

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sawkey, D; Svatos, M

    2015-06-15

    Purpose: Calculate neutron production and transport in the TrueBeam treatment head, as input for vault design and phantom dose calculations. Methods: A detailed model of the treatment head, including shielding components off the beam axis, was created from manufacturer’s engineering drawings. Simulations were done with Geant4 for the 18X, 15X, 10X and 10FFF beams, tuned to match measured dose distributions inside the treatment field. Particles were recorded on a 70 cm radius sphere surrounding the treatment head enabling input into simulations of vaults. Results: For the 18X beam, 11×10{sup 9} neutrons/MU were observed. The energy spectrum was a broad peakmore » with average energy 0.37 MeV. With jaws closed, 48% of the neutrons were generated in the primary collimator, 18% in the jaws, 12% in the target, and 10% in the flattening filter. With wide open jaws, few neutrons were produced in the jaws and consequently total neutron production dropped to 8.5×10{sup 9} neutrons/MU. Angular distributions were greatest along the beam axis (12×10{sup 9} neutrons/MU/sr, within 2 deg of the beam axis) and antiparallel to the beam axis (7×10{sup 9} neutrons/MU/sr). Peaks were observed in the neutron energy spectrum, corresponding to elastic scattering resonances in the shielding materials. Neutron production was lower for the other beams studied: 4.1×10{sup 9} neutrons/MU for 15X, 0.38×10{sup 9} neutrons/MU for 10X, and 0.22×10{sup 9} neutrons/MU for 10FFF. Despite dissimilar treatment head geometries and materials, the neutron production and energy spectrum were similar to those reported for Clinac accelerators. Conclusion: Detailed neutron production and leakage calculations for the TrueBeam treatment head were done. Unlike other studies, results are independent of the surrounding vault, enabling vault design calculations.« less

  6. Measuring The Neutron Lifetime to One Second Using in Beam Techniques

    NASA Astrophysics Data System (ADS)

    Mulholland, Jonathan; NIST In Beam Lifetime Collaboration

    2013-10-01

    The decay of the free neutron is the simplest nuclear beta decay and is the prototype for charged current semi-leptonic weak interactions. A precise value for the neutron lifetime is required for consistency tests of the Standard Model and is an essential parameter in the theory of Big Bang Nucleosynthesis. A new measurement of the neutron lifetime using the in-beam method is planned at the National Institute of Standards and Technology Center for Neutron Research. The systematic effects associated with the in-beam method are markedly different than those found in storage experiments utilizing ultracold neutrons. Experimental improvements, specifically recent advances in the determination of absolute neutron fluence, should permit an overall uncertainty of 1 second on the neutron lifetime. The technical improvements in the in-beam technique, and the path toward improving the precision of the new measurement will be discussed.

  7. Status of the NIST Penning-Trap Neutron Lifetime Measurement

    NASA Astrophysics Data System (ADS)

    Snow, W. M.; Fei, X.; Chowdhuri, Z.; Dewey, M. S.; Gilliam, D.; Nico, J. S.; Greene, G. L.

    1998-10-01

    The decay rate of the free neutron is important input for Big-Bang Nucleosynthesis calculations of the primordial ^4He abundance in the universe(T. P. Walker et al, Astrophys. J. 376, 51 (1991).) and for tests of the electroweak model in the charged-current sector(I. S. Towner, Nucl. Phys. A540, 478 (1992).). We will describe an experiment in progress at NIST to measure the neutron decay rate. The technique uses a Penning trap to trap and count protons from in-beam neutron decay(J. Byrne et al., Phys. Rev. Lett. 65, 289 (1990).) and an absolutely calibrated beam monitor to measure the neutron density in the beam(R. D. Scott et al., Nucl. Inst. Meth. A362, 151 (1995).). We will present data taken in the spring and summer of 1998.

  8. Measurement and Interpretation of DT Neutron Emission from Tftr.

    NASA Astrophysics Data System (ADS)

    McCauley, John Scott, Jr.

    A fast-ion diffusion coefficient of 0.1 +/- 0.1 m^2s ^{-1} has been deduced from the triton burnup neutron emission profile measured by a collimated array of helium-4 spectrometers. The experiment was performed with high-power deuterium discharges produced by Princeton University's Tokamak Fusion Test Reactor (TFTR). The fast ions monitored were the 1.0 MeV tritons produced from the d(d,t)p triton burnup reaction. These tritons "burn up" with deuterons and emit a 14 MeV neutron by the d(t, alpha)n reaction. The measured radial profiles of DT emission were compared with the predictions of a computer transport code. The ratio of the measured-to -calculated DT yield is typically 70%. The measured DT profile width is typically 5 cm larger than predicted by the transport code. The radial 14 MeV neutron profile was measured by a radial array of helium-4 recoil neutron spectrometers installed in the TFTR Multichannel Neutron Collimator (MCNC). The spectrometers are capable of measuring the primary and secondary neutron fluxes from deuterium discharges. The response to 14 MeV neutrons of the array has been measured by cross calibrating with the MCNC ZnS detector array when the emission from TFTR is predominantly DT neutrons. The response was also checked by comparing a model of the recoil spectrum based on nuclear physics data to the observed spectrum from ^{252 }Cf, ^{238}Pu -Be, and DT neutron sources. Extensions of this diagnostic to deuterium-tritium plasma and the implications for fusion research are discussed.

  9. Neutron Spectroscopy on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.

    2012-10-01

    The performance of cryogenic fuel implosion experiments in progress at the National Ignition Facility (NIF) is measured by an experimental threshold factorfootnotetextM. J. Edwards et al., Phys. Plasmas 18, 051003 (2011). (ITFX) and a generalized Lawson Criterion.footnotetextC. D. Zhou and R. Betti, Phys. Plasmas 15, 102707 (2008); P. Y. Chang et al., Phys. Rev. Lett. 104, 135002 (2010); and R. Betti et al., Phys. Plasmas 17, 058102 (2010). The ITFX metric is determined by the fusion yield and the areal density of an assembled deuterium-tritium (DT) fuel mass. Typical neutron yields from NIF implosions are greater than 10^14 allowing the neutron energy spectrum to be measured with unprecedented precision. A NIF spectrum is composed of neutrons created by fusion (DT, DD, and TT reactions) and neutrons scattered by the dense, cold fuel layer. Neutron scattering is used to determine the areal density of a NIF implosion and is measured along four lines of sight by two neutron time-of-flight detectors, a neutron imaging system, and the magnetic recoil spectrometer. An accurate measurement of the instrument response function for these detectors allows for the routine production of neutron spectra showing DT fuel areal densities up to 1.3 g/cm^2. Spectra over neutron energies of 10 to 17 MeV show areal-density asymmetries of 20% that are inconsistent with simulations. New calibrations and analyses have expended the spectral coverage down to energies less than the deuterium backscatter edge (1.5 MeV for 14 MeV neutrons). These data and analyses are presented along with a compilation of other nuclear diagnostic data that show a larger-than-expected variation in the areal density over the cold fuel mass. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No DE-FC52-08NA28302. In collaboration with NIC.

  10. Distribution of thermal neutrons in a temperature gradient

    NASA Astrophysics Data System (ADS)

    Molinari, V. G.; Pollachini, L.

    A method to determine the spatial distribution of the thermal spectrum of neutrons in heterogeneous systems is presented. The method is based on diffusion concepts and has a simple mathematical structure which increases computing efficiency. The application of this theory to the neutron thermal diffusion induced by a temperature gradient, as found in nuclear reactors, is described. After introducing approximations, a nonlinear equation system representing the neutron temperature is given. Values of the equation parameters and its dependence on geometrical factors and media characteristics are discussed.

  11. Neutron Spectrum Measurements from Irradiations at NCERC

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jackman, Kevin Richard; Mosby, Michelle A.; Bredeweg, Todd Allen

    2015-04-15

    Several irradiations have been conducted on assemblies (COMET/ZEUS and Flattop) at the National Criticality Experiments Research Center (NCERC) located at the Nevada National Security Site (NNSS). Configurations of the assemblies and irradiated materials changed between experiments. Different metallic foils were analyzed using the radioactivation method by gamma-ray spectrometry to understand/characterize the neutron spectra. Results of MCNP calculations are shown. It was concluded that MCNP simulated spectra agree with experimental measurements, with the caveats that some data are limited by statistics at low-energies and some activation foils have low activities.

  12. Neutron Capture Gamma-Ray Libraries for Nuclear Applications

    NASA Astrophysics Data System (ADS)

    Sleaford, B. W.; Firestone, R. B.; Summers, N.; Escher, J.; Hurst, A.; Krticka, M.; Basunia, S.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H. D.

    2011-06-01

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

  13. Neutron-induced single event burnout in high voltage electronics

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Normand, E.; Wert, J.L.; Oberg, D.L.

    Energetic neutrons with an atmospheric neutron spectrum, which were demonstrated to induce single event burnout in power MOSFETs, have been shown to induce burnout in high voltage (>3,000V) electronics when operated at voltages as low as 50% of rated voltage. The laboratory failure rates correlate well with field failure rates measured in Europe.

  14. Efficient scalable solid-state neutron detector.

    PubMed

    Moses, Daniel

    2015-06-01

    We report on scalable solid-state neutron detector system that is specifically designed to yield high thermal neutron detection sensitivity. The basic detector unit in this system is made of a (6)Li foil coupled to two crystalline silicon diodes. The theoretical intrinsic efficiency of a detector-unit is 23.8% and that of detector element comprising a stack of five detector-units is 60%. Based on the measured performance of this detector-unit, the performance of a detector system comprising a planar array of detector elements, scaled to encompass effective area of 0.43 m(2), is estimated to yield the minimum absolute efficiency required of radiological portal monitors used in homeland security.

  15. Thermoluminescence measurements of neutron dose around a medical linac.

    PubMed

    Barquero, R; Méndez, R; Iñiguez, M P; Vega, H R; Voytchev, M

    2002-01-01

    The photoncutron ambient dose around a 18 MV medical electron lineal accelerator has been measured with LiF:Mg,Ti chips of 3 x 3 x 1 mm inside moderating spheres. During the measurements a water phantom was irradiated in a field of 40 x 40 cm2. Two methods have been considered for comparison. In the first, a TLD-600/TLD-700 pair at the centre of a 25 cm diameter paraffine sphere was used, with the system behaving as a rem meter. In the second method, TLD-600/TLD-700 pairs, bare and at the centre of 7.6, 12.7, 20.3, 25.4, and 30.5 cm diameter polyethylene Bonner spheres were used to obtain the neutron spectrum. This was unfolded using the BUNKIUT code with the SPUNIT algorithm and the UTA4 and ARKI response functions. The neutron dose was followed by multiplying the unfolded neutron spectrum by the ambient dose equivalent to neutron fluence conversion factors. Both methods result in 0.5 mSv x Gy(-1) m away from the isocentre.

  16. Towards neutron scattering experiments with sub-millisecond time resolution

    DOE PAGES

    Adlmann, F. A.; Gutfreund, Phillip; Ankner, John Francis; ...

    2015-02-01

    Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. We demonstrate that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode atmore » the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. Finally, the opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.« less

  17. A real time scintillating fiber Time of Flight spectrometer for LINAC photoproduced neutrons

    NASA Astrophysics Data System (ADS)

    Maspero, M.; Berra, A.; Conti, V.; Giannini, G.; Ostinelli, A.; Prest, M.; Vallazza, E.

    2015-03-01

    The use of high-energy (> 8 MeV) LINear ACcelerators (LINACs) for medical cancer treatments causes the photoproduction of secondary neutrons, whose unwanted dose to the patient has to be calculated. The characterization of the neutron spectra is necessary to allow the dosimetric evaluation of the neutron beam contamination. The neutron spectrum in a hospital environment is usually measured with integrating detectors such as bubble dosimeters, Thermo Luminescent Dosimeters (TLDs) or Bonner Spheres, which integrate the information over a time interval and an energy one. This paper presents the development of a neutron spectrometer based on the Time of Flight (ToF) technique in order to perform a real time characterization of the neutron contamination. The detector measures the neutron spectrum exploiting the fact that the LINAC beams are pulsed and arranged in bunches with a rate of 100-300 Hz depending on the beam type and energy. The detector consists of boron loaded scintillating fibers readout by a MultiAnode PhotoMultiplier Tube (MAPMT). A detailed description of the detector and the acquisition system together with the results in terms of ToF spectra and number of neutrons with a Varian Clinac iX are presented.

  18. Conception of a New Recoil Proton Telescope for Real-Time Neutron Spectrometry in Proton-Therapy

    NASA Astrophysics Data System (ADS)

    Combe, Rodolphe; Arbor, Nicolas; el Bitar, Ziad; Higueret, Stéphane; Husson, Daniel

    2018-01-01

    Neutrons are the main type of secondary particles emitted in proton-therapy. Because of the risk of secondary cancer and other late occurring effects, the neutron dose should be included in the out-of-field dose calculations. A neutron spectrometer has to be used to take into account the energy dependence of the neutron radiological weighting factor. Due to its high dependence on various parameters of the irradiation (beam, accelerator, patient), the neutron spectrum should be measured independently for each treatment. The current reference method for the measurement of the neutron energy, the Bonner Sphere System, consists of several homogeneous polyethylene spheres with increasing diameters equipped with a proportional counter. It provides a highresolution reconstruction of the neutron spectrum but requires a time-consuming work of signal deconvolution. New neutron spectrometers are being developed, but the main experimental limitation remains the high neutron flux in proton therapy treatment rooms. A new model of a real-time neutron spectrometer, based on a Recoil Proton Telescope technology, has been developed at the IPHC. It enables a real-time high-rate reconstruction of the neutron spectrum from the measurement of the recoil proton trajectory and energy. A new fast-readout microelectronic integrated sensor, called FastPixN, has been developed for this specific purpose. A first prototype, able to detect neutrons between 5 and 20 MeV, has already been validated for metrology with the AMANDE facility at Cadarache. The geometry of the new Recoil Proton Telescope has been optimized via extensive Geant4 Monte Carlo simulations. Uncertainty sources have been carefully studied in order to improve simultaneously efficiency and energy resolution, and solutions have been found to suppress the various expected backgrounds. We are currently upgrading the prototype for secondary neutron detection in proton therapy applications.

  19. Neutron Scattering Differential Cross Sections for 12C

    NASA Astrophysics Data System (ADS)

    Byrd, Stephen T.; Hicks, S. F.; Nickel, M. T.; Block, S. G.; Peters, E. E.; Ramirez, A. P. D.; Mukhopadhyay, S.; McEllistrem, M. T.; Yates, S. W.; Vanhoy, J. R.

    2016-09-01

    Because of the prevalence of its use in the nuclear energy industry and for our overall understanding of the interactions of neutrons with matter, accurately determining the effects of fast neutrons scattering from 12C is important. Previously measured 12C inelastic neutron scattering differential cross sections found in the National Nuclear Data Center (NNDC) show significant discrepancies (>30%). Seeking to resolve these discrepancies, neutron inelastic and elastic scattering differential cross sections for 12C were measured at the University of Kentucky Acceleratory Laboratory for incident neutron energies of 5.58, 5.83, and 6.04 MeV. Quasi mono-energetic neutrons were scattered off an enriched 12C target (>99.99%) and detected by a C6D6 liquid scintillation detector. Time-of-flight (TOF) techniques were used to determine scattered neutron energies and allowed for elastic/inelastic scattering distinction. Relative detector efficiencies were determined through direct measurements of neutrons produced by the 2H(d,n) and 3H(p,n) source reactions, and absolute normalization factors were found by comparing 1H scattering measurements to accepted NNDC values. This experimental procedure has been successfully used for prior neutron scattering measurements and seems well-suited to our current objective. Significant challenges were encountered, however, with measuring the neutron detector efficiency over the broad incident neutron energy range required for these measurements. Funding for this research was provided by the National Nuclear Security Administration (NNSA).

  20. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  1. Time-resolved neutron imaging at ANTARES cold neutron beamline

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Dangendorf, V.; Tittelmeier, K.; Schillinger, B.; Schulz, M.; Lerche, M.; Feller, W. B.

    2015-07-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and integrated over multiple cycles. A fast MCP/Timepix neutron counting detector was used to image the water distribution within a model steam engine operating at 10 Hz frequency. Within <10 minutes integration the amount of water was measured as a function of cycle time with a sub-mm spatial resolution, thereby demonstrating the capabilities of time-resolved neutron radiography for the future applications. The neutron spectrum of the ANTARES beamline as well as transmission spectra of a Fe sample were also measured with the Time Of Flight (TOF) technique in combination with a high resolution beam chopper. The energy resolution of our setup was found to be ~ 0.8% at 5 meV and ~ 1.7% at 25 meV. The background level (most likely gammas and epithermal/fast neutrons) of the ANTARES beamline was also measured in our experiments and found to be on the scale of 3% when no filters are installed in the beam. Online supplementary data available from stacks.iop.org/jinst/10

  2. Study of DD Neutrons and their Transmission in Iron Spheres

    NASA Astrophysics Data System (ADS)

    Dhakal, Sushil

    The Deuterium-Deuteron (DD) reaction has been used as a neutron source to study the transport of neutrons in natural iron. The scattering targets are used in the form of spheres and the neutron transmission measurement has been done at 7-MeV incident deuteron beam energy. The purpose of this study is to test the elastic and non-elastic neutron scattering cross sections for iron in the ENDF/B-VII data library, as some indications about the inaccuracy of those cross sections have been found from previous studies. The experiment has been carried out using the 4.5-MV tandem accelerator at Edwards Accelerator Laboratory at Ohio University, Athens, Ohio. The DD source reaction has been measured at 5- and 7-MeV deuteron beam energy. The D(d,n)3He monoenergetic reaction cross section has been measured from 0° to 135° at both 5- and 7-MeV beam energy and the D(d,np)D breakup reaction cross section has been measured up to 60° laboratory angles at 7-MeV beam energy. The target used is a deuterium gas cell of 3-cm length at approximately 2 atmosphere absolute pressure. The neutron energy is determined using the time of flight method. A NE213 liquid scintillation detector is used for neutron detection and the thick-target 27Al(d,n) reaction is used for the determination of neutron detector efficiency. The monoenergetic reaction cross section has been found to be in reasonable agreement with previous evaluations. The neutron transmission studies through iron spheres is done using two natural iron spheres with thicknesses of 3 and 8 cm. The DD source measurement (sphere-off) were repeated for the transmission studies and the neutron source was covered with the spheres for the transmission measurements. The experimental transmitted neutron spectrum is compared with the calculation done using Monte Carlo simulation code MCNP6.1 developed by Los Alamos National Laboratory. MCNP uses ENDF/B-VII.1 evaluated iron cross section for the simulation. The calculated and experimental

  3. Diffraction in neutron imaging-A review

    NASA Astrophysics Data System (ADS)

    Woracek, Robin; Santisteban, Javier; Fedrigo, Anna; Strobl, Markus

    2018-01-01

    Neutron imaging is a highly successful experimental technique ever since adequate neutron sources were available. In general, neutron imaging is performed with a wide wavelength spectrum for best flux conditions in transmission geometry. Neutrons provide outstanding features in the penetration of many structural materials, which often makes them more suited for bulk sample studies than other forms of radiation, often in particular as they are also highly sensitive to some light elements, especially Hydrogen. In contrast to neutron scattering applications, imaging resolves macroscopic structures, nowadays down to, in the best case, below 10 micrometre, directly in real space. However, since more than a decade there is a growing number of techniques and applications in neutron imaging that - supported by powerful neutron sources - are taking advantage of wavelength resolved measurements. In this review we summarize and discuss this outstanding development and how wavelength resolved transmission neutron imaging is successfully exploiting diffraction mechanisms to access crystal structure information in the Angstrom regime, which conventionally is probed in reciprocal space by diffraction techniques. In particular the combination of information gained in real space and on crystallographic length scales makes this neutron imaging technique a valuable tool for a wide range of new applications, while it also qualifies neutron imaging to fully profit from the new generation of powerful pulsed neutron sources.

  4. Apollo 16 neutron stratigraphy.

    NASA Technical Reports Server (NTRS)

    Russ, G. P., III

    1973-01-01

    The Apollo 16 soils have the largest low-energy neutron fluences yet observed in lunar samples. Variations in the isotopic ratios Gd-158/Gd-157 and Sm-150/Sm-149 (up to 1.9 and 2.0%, respectively) indicate that the low-energy neutron fluence in the Apollo 16 drill stem increases with depth throughout the section sampled. Such a variation implies that accretion has been the dominant regolith 'gardening' process at this location. The data may be fit by a model of continuous accretion of pre-irradiated material or by models involving as few as two slabs of material in which the first slab could have been deposited as long as 1 b.y. ago. The ratio of the number of neutrons captured per atom by Sm to the number captured per atom by Gd is lower than in previously measured lunar samples, which implies a lower energy neutron spectrum at this site. The variation of this ratio with chemical composition is qualitatively similar to that predicted by Lingenfelter et al. (1972). Variations are observed in the ratio Gd-152/Gd-160 which are fluence-correlated and probably result from neutron capture by Eu-151.

  5. Study on a liquid-moderator-based neutron spectrometer for BNCT-Development and experimental test of the prototype spectrometer

    NASA Astrophysics Data System (ADS)

    Tamaki, S.; Sato, F.; Murata, I.

    2017-10-01

    Boron neutron capture therapy (BNCT) is known to be an effective radiation cancer therapy that requires neutron irradiation. A neutron field generated by an accelerator-based neutron source has various energy spectra, and it is necessary to evaluate the neutron spectrum in the treatment field. However, the method used to measure the neutron spectrum in the treatment field is not well established, and many researchers are making efforts to improve the spectrometers used. In the present study, we developed a prototype of a new neutron spectrometer that can measure the neutron spectra more accurately and precisely. The spectrometer is based on the same theory as that of the Bonner sphere spectrometer, and it uses a liquid moderator and an absorber. By carrying out an experimental test of the developed spectrometer, we finally revealed the problems and necessary conditions of the prototype detector.

  6. An equivalent n-source for WGPu derived from a spectrum-shifted PuBe source

    NASA Astrophysics Data System (ADS)

    Ghita, Gabriel; Sjoden, Glenn; Baciak, James; Walker, Scotty; Cornelison, Spring

    2008-04-01

    We have designed, built, and laboratory-tested a unique shield design that transforms the complex neutron spectrum from PuBe source neutrons, generated at high energies, to nearly exactly the neutron signature leaking from a significant spherical mass of weapons grade plutonium (WGPu). This equivalent "X-material shield assembly" (Patent Pending) enables the harder PuBe source spectrum (average energy of 4.61 MeV) from a small encapsulated standard 1-Ci PuBe source to be transformed, through interactions in the shield, so that leakage neutrons are shifted in energy and yield to become a close reproduction of the neutron spectrum leaking from a large subcritical mass of WGPu metal (mean energy 2.11 MeV). The utility of this shielded PuBe surrogate for WGPu is clear, since it directly enables detector field testing without the expense and risk of handling large amounts of Special Nuclear Materials (SNM) as WGPu. Also, conventional sources using Cf-252, which is difficult to produce, and decays with a 2.7 year half life, could be replaced by this shielded PuBe technology in order to simplify operational use, since a sealed PuBe source relies on Pu-239 (T½=24,110 y), and remains viable for more than hundreds of years.

  7. Two Coils Resonant Ramsey's Method for the Measurement of Time Reversal Invariance Violation in Neutron Transmission.

    PubMed

    Loukachevitch, V V; Aldushchenkov, A V

    2005-01-01

    It is proposed within the framework of Ramsey's method to register two-dimensional spectra, depending on the neutron phase and neutron energy, for measuring parity (P) and time (T) violating amplitudes of the interaction of polarized neutrons with polarized (139)La nuclei in region of the p-wave resonance. The form of the phase spectrum and corresponding expressions for the asymmetries are obtained on the basis of a formalism of a spin density matrix. It is shown that the ratio of the P,T,-violating to P-violating imaginary amplitudes can be obtained from the measurements of the neutron phase spectrum with polarized and unpolarized (139)La target.

  8. Neutron dosimetric measurements in shuttle and MIR.

    PubMed

    Reitz, G

    2001-06-01

    Detector packages consisting of thermoluminescence detectors (TLD), nuclear emulsions and plastic track detectors were exposed at identical positions inside MIR space station and on shuttle flights inside Spacelab and Spacehab during different phases of the solar cycle. The objectives of the investigations are to provide data on charge and energy spectra of heavy ions, and the contribution of events with low-energy deposit (protons, electrons, gamma, etc.) to the dose, as well as the contribution of secondaries, such as nuclear disintegration stars and neutrons. For neutron dosimetry 6LiF (TLD600) and 7LiF (TLD700) chips were used both of which have almost the same response to gamma rays but different response to neutrons. Neutrons in space are produced mainly in evaporation and knock-on processes with energies mainly of 1-10 MeV and up to several 100 MeV, respectively. The energy spectrum undergoes continuous changes toward greater depth in the attenuating material until an equilibrium is reached. In equilibrium, the spectrum is a wide continuum extending down to thermal energies to which the 6LiF is sensitive. Based on the difference of absorbed doses in the 6LiF and 7LiF chips, thermal neutron fluxes from 1 to 2.3 cm-2 s-1 are calculated using the assumption that the maximum induced dose in TLD600 for 1 neutron cm-2 is 1.6 x 10(-10) Gy (Horowitz and Freeman, Nucl. Instr. and Meth. 157 (1978) 393). It is assumed that the flux of high-energy neutrons is at least of that quantity. Tissue doses were calculated taking as a mean ambient absorbed dose per neutron 6 x10(-12) Gy cm2 (for a10 MeV neutron). The neutron equivalent doses for the above-mentioned fluxes are 52 micro Gy d-1 and 120 micro Gy d-1. In recent experiments, a personal neutron dosimeter was integrated into the dosimeter packages. First results of this dosimeter which is based on nuclear track detectors with converter foils are reported. For future measurements, a scintillator counter with

  9. Induction of Micronuclei in Human Fibroblasts from the Los Alamos High Energy Neutron Beam

    NASA Technical Reports Server (NTRS)

    Cox, Bradley

    2009-01-01

    The space radiation field includes a broad spectrum of high energy neutrons. Interactions between these neutrons and a spacecraft, or other material, significantly contribute to the dose equivalent for astronauts. The 15 degree beam line in the Weapons Neutron Research beam at Los Alamos Nuclear Science Center generates a neutron spectrum relatively similar to that seen in space. Human foreskin fibroblast (AG1522) samples were irradiated behind 0 to 20 cm of water equivalent shielding. The cells were exposed to either a 0.05 or 0.2 Gy entrance dose. Following irradiation, micronuclei were counted to see how the water shield affects the beam and its damage to cell nuclei. Micronuclei induction was then compared with dose equivalent data provided from a tissue equivalent proportional counter.

  10. PROSPECT - A precision oscillation and spectrum experiment

    NASA Astrophysics Data System (ADS)

    Langford, T. J.; PROSPECT Collaboration

    2015-08-01

    Segmented antineutrino detectors placed near a compact research reactor provide an excellent opportunity to probe short-baseline neutrino oscillations and precisely measure the reactor antineutrino spectrum. Close proximity to a reactor combined with minimal overburden yield a high background environment that must be managed through shielding and detector technology. PROSPECT is a new experimental effort to detect reactor antineutrinos from the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, managed by UT Battelle for the U.S. Department of Energy. The detector will use novel lithium-loaded liquid scintillator capable of neutron/gamma pulse shape discrimination and neutron capture tagging. These enhancements improve the ability to identify neutrino inverse-beta decays (IBD) and reject background events in analysis. Results from these efforts will be covered along with their implications for an oscillation search and a precision spectrum measurement.

  11. D-D Neutron Generator Calibrations and Hardware in the LUX-ZEPLIN Dark Matter Search Experiment

    NASA Astrophysics Data System (ADS)

    Taylor, Will; Lux-Zeplin Collaboration

    2016-03-01

    The LUX-ZEPLIN (LZ) dark matter search experiment will be a two-phase liquid/gas xenon time projection chamber with 7 tonnes of active liquid xenon (LXe) located at the 4850 ft level of the Sanford Underground Research Facility in Lead, SD. LZ will utilize an in-situ, absolute calibration of nuclear recoils (NR) in LXe using mono-energetic 2.45 MeV neutrons produced by a D-D neutron generator. This technique was used in the LUX detector to measured the NR charge yield in LXe (Qy) to 0.7 keV recoil energy and the NR light yield in LXe (Ly) to recoil energies of 1.1 keV - both of which were the lowest energy measurements achieved in the field. These absolute, ultra-low energy calibrations of the NR signal yields in LXe provide clear measurements of the detector response used for the WIMP search analysis. The improvements made for LZ will include shorter neutron pulse times, multiple neutron conduit configurations, and lower energy neutrons. The upgrades allow for even lower energy measurements of the nuclear recoil response in LXe and an independent measurement of Ly, as well as providing less uncertainty in energy reconstruction. In addition to discussing the physics of the neutron calibrations, I will describe the hardware systems used to implement them.

  12. Improved Determination of the Neutron Lifetime

    NASA Astrophysics Data System (ADS)

    Yue, A.

    2013-10-01

    The most precise determination of the neutron lifetime using the beam method reported a result of τn = (886 . 3 +/- 3 . 4) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was determined with a monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. We have used a second, totally-absorbing neutron detector to directly measure the detection efficiency of the monitor on a monochromatic neutron beam of precisely known wavelength. This method does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The monitor detection efficiency was measured to an uncertainty of 0.06%, which represents a five-fold improvement in uncertainty. We have verified the temporal stability of the monitor with ancillary measurements, and the measured neutron monitor efficiency has been used to improve the fluence determination in the past lifetime experiment. An updated neutron lifetime based on the improved fluence determination will be presented. Work done in collaboration with M. Dewey, D. Gilliam, J. Nico, National Institute of Standards and Technology; G. Greene, University of Tennessee / Oak Ridge National Laboratory; A. Laptev, Los Alamos National Laboratory; W. Snow, Indiana University; and F. Wietfeldt, Tulane University.

  13. High efficiency proportional neutron detector with solid liner internal structures

    DOEpatents

    Kisner, Roger Allen; Holcomb, David Eugene; Brown, Gilbert M.

    2014-08-05

    A tube-style neutron detector, a panel-style neutron detector incorporating a plurality of tube-style neutron detectors, and a panel-style neutron detector including a plurality of anode wires are provided. A plurality of channels is provided in a neutron detector such that each channel has an inner surface of a coating layer including a neutron-absorbing material. A wire anode is provided at end of each channel so that electrons generated by a charged daughter particle generated by a neutron are collected to detect a neutron-matter interaction. Moderator units can be incorporated into a neutron detector to provide improved detection efficiencies and/or to determine neutron energy spectrum. Gas-based proportional response from the neutron detectors can be employed for special nuclear material (SNM) detection. This neutron detector can provide similar performance to .sup.3He-based detectors without requiring .sup.3He and without containing toxic, flammable, or high-pressure materials.

  14. Physical particularities of nuclear reactors using heavy moderators of neutrons

    NASA Astrophysics Data System (ADS)

    Kulikov, G. G.; Shmelev, A. N.

    2016-12-01

    In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using 233U as a fissile nuclide and 232Th and 231Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program package for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.

  15. Physical particularities of nuclear reactors using heavy moderators of neutrons

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kulikov, G. G., E-mail: ggkulikov@mephi.ru; Shmelev, A. N.

    2016-12-15

    In nuclear reactors, thermal neutron spectra are formed using moderators with small atomic weights. For fast reactors, inserting such moderators in the core may create problems since they efficiently decelerate the neutrons. In order to form an intermediate neutron spectrum, it is preferable to employ neutron moderators with sufficiently large atomic weights, using {sup 233}U as a fissile nuclide and {sup 232}Th and {sup 231}Pa as fertile ones. The aim of the work is to investigate the properties of heavy neutron moderators and to assess their advantages. The analysis employs the JENDL-4.0 nuclear data library and the SCALE program packagemore » for simulating the variation of fuel composition caused by irradiation in the reactor. The following main results are obtained. By using heavy moderators with small neutron moderation steps, one is able to (1) increase the rate of resonance capture, so that the amount of fertile material in the fuel may be reduced while maintaining the breeding factor of the core; (2) use the vacant space for improving the fuel-element properties by adding inert, strong, and thermally conductive materials and by implementing dispersive fuel elements in which the fissile material is self-replenished and neutron multiplication remains stable during the process of fuel burnup; and (3) employ mixtures of different fertile materials with resonance capture cross sections in order to increase the resonance-lattice density and the probability of resonance neutron capture leading to formation of fissile material. The general conclusion is that, by forming an intermediate neutron spectrum with heavy neutron moderators, one can use the fuel more efficiently and improve nuclear safety.« less

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

    NASA Astrophysics Data System (ADS)

    Murphy, T. J.

    2014-07-01

    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.

  17. Neutron spectrometry for radiation protection purposes

    NASA Astrophysics Data System (ADS)

    McDonald, J. C.; Siebert, B. R. L.; Alberts, W. G.

    2002-01-01

    Determination of the dose equivalent is required for radiation protection purposes, however such a determination is quite difficult for neutron radiation. In order to perform accurate dosimetric determinations, it is advantageous to acquire information about the neutron fluence spectrum in the workplace as well as the reference radiations used to calibrate dosimetric instruments. This information can then be used to select the appropriate dosimetric instrument, the optimum calibration condition or to establish correction factors that account for the differences in calibration and workplace conditions. For quite some time, neutron spectrometry has been used for these purposes. A brief review of the applications of spectrometers in radiation protection and some recommendations for further development are given here.

  18. [Neutron Dosimetry System Using CR-39 for High-energy X-ray Radiation Therapy].

    PubMed

    Yabuta, Kazutoshi; Monzen, Hajime; Tamura, Masaya; Tsuruta, Takao; Itou, Tetsuo; Nohtomi, Akihiro; Nishimura, Yasumasa

    2014-01-01

    Neutrons are produced during radiation treatment by megavolt X-ray energies. However, it is difficult to measure neutron dose especially just during the irradiation. Therefore, we have developed a system for measuring neutrons with the solid state track detector CR-39, which is free from the influence of the X-ray beams. The energy spectrum of the neutrons was estimated by a Monte Carlo simulation method, and the estimated neutron dose was corrected by the contribution ratio of each energy. Pit formation rates of CR-39 ranged from 2.3 x 10(-3) to 8.2 x 10(-3) for each detector studied. According to the estimated neutron energy spectrum, the energy values for calibration were 144 keV and 515keV, and the contribution ratios were approximately 40:60 for 10 MV photons and 20:70 for photons over 15 MV. Neutron doses measured in the center of a high-energy X-ray field were 0.045 mSv/Gy for a 10 MV linear accelerator and 0.85 mSv/Gy for a 20 MV linear accelerator. We successfully developed the new neutron dose measurement system using the solid track detector, CR-39. This on-time neutron measurement system allows users to measure neutron doses produced in the radiation treatment room more easily.

  19. Absolute versus convective helical magnetorotational instability in a Taylor-Couette flow.

    PubMed

    Priede, Jānis; Gerbeth, Gunter

    2009-04-01

    We analyze numerically the magnetorotational instability of a Taylor-Couette flow in a helical magnetic field [helical magnetorotational instability (HMRI)] using the inductionless approximation defined by a zero magnetic Prandtl number (Pr_{m}=0) . The Chebyshev collocation method is used to calculate the eigenvalue spectrum for small-amplitude perturbations. First, we carry out a detailed conventional linear stability analysis with respect to perturbations in the form of Fourier modes that corresponds to the convective instability which is not in general self-sustained. The helical magnetic field is found to extend the instability to a relatively narrow range beyond its purely hydrodynamic limit defined by the Rayleigh line. There is not only a lower critical threshold at which HMRI appears but also an upper one at which it disappears again. The latter distinguishes the HMRI from a magnetically modified Taylor vortex flow. Second, we find an absolute instability threshold as well. In the hydrodynamically unstable regime before the Rayleigh line, the threshold of absolute instability is just slightly above the convective one although the critical wavelength of the former is noticeably shorter than that of the latter. Beyond the Rayleigh line the lower threshold of absolute instability rises significantly above the corresponding convective one while the upper one descends significantly below its convective counterpart. As a result, the extension of the absolute HMRI beyond the Rayleigh line is considerably shorter than that of the convective instability. The absolute HMRI is supposed to be self-sustained and, thus, experimentally observable without any external excitation in a system of sufficiently large axial extension.

  20. Fusion neutron detector for time-of-flight measurements in z-pinch and plasma focus experiments.

    PubMed

    Klir, D; Kravarik, J; Kubes, P; Rezac, K; Litseva, E; Tomaszewski, K; Karpinski, L; Paduch, M; Scholz, M

    2011-03-01

    We have developed and tested sensitive neutron detectors for neutron time-of-flight measurements in z-pinch and plasma focus experiments with neutron emission times in tens of nanoseconds and with neutron yields between 10(6) and 10(12) per one shot. The neutron detectors are composed of a BC-408 fast plastic scintillator and Hamamatsu H1949-51 photomultiplier tube (PMT). During the calibration procedure, a PMT delay was determined for various operating voltages. The temporal resolution of the neutron detector was measured for the most commonly used PMT voltage of 1.4 kV. At the PF-1000 plasma focus, a novel method of the acquisition of a pulse height distribution has been used. This pulse height analysis enabled to determine the single neutron sensitivity for various neutron energies and to calibrate the neutron detector for absolute neutron yields at about 2.45 MeV.

  1. Nuclear Data Needs for the Neutronic Design of MYRRHA Fast Spectrum Research Reactor

    NASA Astrophysics Data System (ADS)

    Stankovskiy, A.; Malambu, E.; Van den Eynde, G.; Díez, C. J.

    2014-04-01

    A global sensitivity analysis of effective neutron multiplication factor to the change of nuclear data library has been performed. It revealed that the test version of JEFF-3.2 neutron-induced evaluated data library produces closer results to ENDF/B-VII.1 than JEFF-3.1.2 does. The analysis of contributions of individual evaluations into keff sensitivity resulted in the priority list of nuclides, uncertainties on cross sections and fission neutron multiplicities of which have to be improved by setting up dedicated differential and integral experiments.

  2. bcc-iron as a promising new monochromator material for thermal neutrons

    NASA Astrophysics Data System (ADS)

    Kirscht, Patrick; Sobolev, Oleg; Eckold, Götz

    2018-04-01

    The development of high-performance neutron monochromators is a long-standing and still actual topic in neutron instrumentation. Due to its high scattering cross section, iron is a particularly interesting material since it offers the possibility to obtain high reflectivities at small wavelength and good resolution. Phase transitions between bcc- and fcc-phases hindered the growth of large and high-quality single crystals in the past and only recently bcc-crystals became commercially available. We have characterized the reflecting properties of as-grown and deformed crystals using γ-rays and thermal neutrons. Absolute reflectivities well above 30% for neutron wavelengths near 1 Å could be obtained that are superior to that of all other existing monochromator materials. Hence, the progress in crystal growth along with the knowledge of directed plastic deformation makes the development of bcc-Fe neutron monochromators feasible. Their application in crystal-monochromator instruments is suitable to increase the useful neutron flux at large energies considerably.

  3. 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.

  4. A rare gas optics-free absolute photon flux and energy analyzer to provide absolute photoionization rates of inflowing interstellar neutrals

    NASA Technical Reports Server (NTRS)

    Judge, Darrell L.

    1994-01-01

    A prototype spectrometer has been developed for space applications requiring long term absolute EUV photon flux measurements. The energy spectrum of the incoming photons is transformed directly into an electron energy spectrum by taking advantage of the photoelectric effect in one of several rare gases at low pressures. Using an electron energy spectrometer, followed by an electron multiplier detector, pulses due to individual electrons are counted. The overall efficiency of this process can be made essentially independent of gain drifts in the signal path, and the secular degradation of optical components which is often a problem in other techniques is avoided. A very important feature of this approach is its freedom from the problem of overlapping spectral orders that plagues grating EUV spectrometers. An instrument with these features has not been flown before, but is essential to further advances in our understanding of solar EUV flux dynamics, and the coupled dynamics of terrestrial and planetary atmospheres. The detailed characteristics of this optics-free spectrometer are presented in the publications section.

  5. Neutron flux characterization of californium-252 Neutron Research Facility at the University of Texas - Pan American by nuclear analytical technique

    NASA Astrophysics Data System (ADS)

    Wahid, Kareem; Sanchez, Patrick; Hannan, Mohammad

    2014-03-01

    In the field of nuclear science, neutron flux is an intrinsic property of nuclear reaction facilities that is the basis for experimental irradiation calculations and analysis. In the Rio Grande Valley (Texas), the UTPA Neutron Research Facility (NRF) is currently the only neutron facility available for experimental research purposes. The facility is comprised of a 20-microgram californium-252 neutron source surrounded by a shielding cascade containing different irradiation cavities. Thermal and fast neutron flux values for the UTPA NRF have yet to be fully investigated and may be of particular interest to biomedical studies in low neutron dose applications. Though a variety of techniques exist for the characterization of neutron flux, neutron activation analysis (NAA) of metal and nonmetal foils is a commonly utilized experimental method because of its detection sensitivity and availability. The aim of our current investigation is to employ foil activation in the determination of neutron flux values for the UTPA NSRF for further research purposes. Neutron spectrum unfolding of the acquired experimental data via specialized software and subsequent comparison for consistency with computational models lends confidence to the results.

  6. Modeling the National Ignition Facility neutron imaging system.

    PubMed

    Wilson, D C; Grim, G P; Tregillis, I L; Wilke, M D; Patel, M V; Sepke, S M; Morgan, G L; Hatarik, R; Loomis, E N; Wilde, C H; Oertel, J A; Fatherley, V E; Clark, D D; Fittinghoff, D N; Bower, D E; Schmitt, M J; Marinak, M M; Munro, D H; Merrill, F E; Moran, M J; Wang, T-S F; Danly, C R; Hilko, R A; Batha, S H; Frank, M; Buckles, R

    2010-10-01

    Numerical modeling of the neutron imaging system for the National Ignition Facility (NIF), forward from calculated target neutron emission to a camera image, will guide both the reduction of data and the future development of the system. Located 28 m from target chamber center, the system can produce two images at different neutron energies by gating on neutron arrival time. The brighter image, using neutrons near 14 MeV, reflects the size and symmetry of the implosion "hot spot." A second image in scattered neutrons, 10-12 MeV, reflects the size and symmetry of colder, denser fuel, but with only ∼1%-7% of the neutrons. A misalignment of the pinhole assembly up to ±175 μm is covered by a set of 37 subapertures with different pointings. The model includes the variability of the pinhole point spread function across the field of view. Omega experiments provided absolute calibration, scintillator spatial broadening, and the level of residual light in the down-scattered image from the primary neutrons. Application of the model to light decay measurements of EJ399, BC422, BCF99-55, Xylene, DPAC-30, and Liquid A suggests that DPAC-30 and Liquid A would be preferred over the BCF99-55 scintillator chosen for the first NIF system, if they could be fabricated into detectors with sufficient resolution.

  7. Thermal neutron calibration channel at LNMRI/IRD.

    PubMed

    Astuto, A; Salgado, A P; Leite, S P; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

    2014-10-01

    The Brazilian Metrology Laboratory of Ionizing Radiations (LNMRI) standard thermal neutron flux facility was designed to provide uniform neutron fluence for calibration of small neutron detectors and individual dosemeters. This fluence is obtained by neutron moderation from four (241)Am-Be sources, each with 596 GBq, in a facility built with blocks of graphite/paraffin compound and high-purity carbon graphite. This study was carried out in two steps. In the first step, simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The quality of the resulting neutron fluence in terms of spectrum, cadmium ratio and gamma-neutron ratio was evaluated. In the second step, the system was assembled based on the results obtained on the simulations, and new measurements are being made. These measurements will validate the system, and other intercomparisons will ensure traceability to the International System of Units. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  8. Characterization of the high-energy neutron beam of the PRISMA beamline using a diamond detector

    NASA Astrophysics Data System (ADS)

    Cazzaniga, C.; Frost, C. D.; Minniti, T.; Schooneveld, E.; Perelli Cippo, E.; Tardocchi, M.; Rebai, M.; Gorini, G.

    2016-07-01

    The high-energy neutron component (En > 10 MeV) of the neutron spectrum of PRISMA, a beam-line at the ISIS spallation source, has been characterized for the first time. Neutron measurements using a Single-crystal Diamond Detector at a short-pulse source are obtained by a combination of pulse height and time of flight analysis. An XY scan provides a 2D map of the high-energy neutron beam which has a diameter of about 40 mm. The high neutron flux, that has been found to be (3.8 ± 0.7) · 105 cm-2s-1 for En > 10 MeV in the centre, opens up for a possible application of the beam-line as a high-energy neutron irradiation position. Results are of interest for the development of the ChipIR beam-line, which will feature an atmospheric-like neutron spectrum for chip irradiation experiment. Furthermore, these results demonstrate that diamond detectors can be used at spallation sources to investigate the transport of high-energy neutrons down instruments which is of interest in general to designers as high-energy neutrons are a source of background in thermal beamlines.

  9. Study of pulse shape discrimination for a neutron phoswich detector

    NASA Astrophysics Data System (ADS)

    Hartman, Jessica; Barzilov, Alexander

    2017-09-01

    A portable phoswich detector capable of differentiating between fast neutrons and thermal neutrons, and photons was developed. The detector design is based on the use of two solid-state scintillators with dissimilar scintillation time properties coupled with a single optical sensor: a 6Li loaded glass and EJ-299-33A plastic. The on-the-fly digital pulse shape discrimination and the wavelet treatment of measured waveforms were employed in the data analysis. The instrument enabled neutron spectrum evaluation.

  10. FAST NEUTRON SPECTROMETER

    DOEpatents

    Davis, F.J.; Hurst, G.S.; Reinhardt, P.W.

    1959-08-18

    An improved proton recoil spectrometer for determining the energy spectrum of a fast neutron beam is described. Instead of discriminating against and thereby"throwing away" the many recoil protons other than those traveling parallel to the neutron beam axis as do conventional spectrometers, this device utilizes protons scattered over a very wide solid angle. An ovoidal gas-filled recoil chamber is coated on the inside with a scintillator. The ovoidal shape of the sensitive portion of the wall defining the chamber conforms to the envelope of the range of the proton recoils from the radiator disposed within the chamber. A photomultiplier monitors the output of the scintillator, and a counter counts the pulses caused by protons of energy just sufficient to reach the scintillator.

  11. Measurement of the 242Pu neutron capture cross section

    NASA Astrophysics Data System (ADS)

    Buckner, M. Q.; Wu, C. Y.; Henderson, R. A.; Bucher, B.; Bredeweg, T. A.; Baramsai, B.; Couture, A.; Jandel, M.; Mosby, S.; O'Donnell, J. M.; Ullmann, J. L.; Chyzh, A.; Dance Collaboration

    2015-10-01

    Precision (n,f) and (n, γ) cross sections are important for the network calculations of the radiochemical diagnostic chain for the U.S. DOE's Stockpile Stewardship Program. 242Pu(n, γ) cross section is relevant to the network calculations of Pu and Am. Additionally, new reactor concepts have catalyzed considerable interest in the measurement of improved cross sections for neutron-induced reactions on key actinides. To date, little or no experimental data has been reported on 242Pu(n, γ) for incident neutron energy below 50 keV. A new measurement of the 242Pu(n, γ) reaction was performed with the DANCE together with an improved PPAC for fission-fragment detection at LANSCE during FY14. The relative scale of the 242Pu(n, γ) cross section spans four orders of magnitude for incident neutron energies from thermal to ~ 30 keV. The absolute scale of the 242Pu(n, γ) cross section is set according to the measured 239Pu(n,f) resonance at 7.8 eV; the target was spiked with 239Pu for this measurement. The absolute 242Pu(n, γ) neutron capture cross section is ~ 30% higher than the cross section reported in ENDF for the 2.7 eV resonance. Latest results to be reported. Funded by U.S. DOE Contract No. DE-AC52-07NA27344 (LLNL) and DE-AC52-06NA25396 (LANL). U.S. DOE/NNSA Office of Defense Nuclear Nonproliferation Research and Development. Isotopes (ORNL).

  12. Searching for X-ray Pulsations from Neutron Stars Using NICER

    NASA Astrophysics Data System (ADS)

    Ray, Paul S.; Arzoumanian, Zaven; Bogdanov, Slavko; Bult, Peter; Chakrabarty, Deepto; Guillot, Sebastien; Kust Harding, Alice; Ho, Wynn C. G.; Lamb, Frederick K.; Mahmoodifar, Simin; Miller, M. Coleman; Strohmayer, Tod E.; Wilson-Hodge, Colleen A.; Wolff, Michael Thomas

    2017-08-01

    The Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for discovering new modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for pulsations and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, LMXBs, accretion-powered millisecond pulsars, central compact objects and other sources. We will present our science plan and initial results from the first months of the NICER mission.

  13. Searching for X-ray Pulsations from Neutron Stars Using NICER

    NASA Astrophysics Data System (ADS)

    Ray, Paul S.; Arzoumanian, Zaven; Gendreau, Keith C.; Bogdanov, Slavko; Bult, Peter; Chakrabarty, Deepto; Chakrabarty, Deepto; Guillot, Sebastien; Harding, Alice; Ho, Wynn C. G.; Lamb, Frederick; Mahmoodifar, Simin; Miller, Cole; Strohmayer, Tod; Wilson-Hodge, Colleen; Wolff, Michael T.; NICER Science Team Working Group on Pulsation Searches and Multiwavelength Coordination

    2018-01-01

    The Neutron Star Interior Composition Explorer (NICER) presents an exciting new capability for discovering new modulation properties of X-ray emitting neutron stars, including large area, low background, extremely precise absolute time stamps, superb low-energy response and flexible scheduling. The Pulsation Searches and Multiwavelength Coordination working group has designed a 2.5 Ms observing program to search for pulsations and characterize the modulation properties of about 30 known or suspected neutron star sources across a number of source categories. A key early goal will be to search for pulsations from millisecond pulsars that might exhibit thermal pulsations from the surface suitable for pulse profile modeling to constrain the neutron star equation of state. In addition, we will search for pulsations from transitional millisecond pulsars, isolated neutron stars, LMXBs, accretion-powered millisecond pulsars, central compact objects and other sources. We present our science plan and initial results from the first months of the NICER mission.

  14. Neutron spectroscopy with scintillation detectors using wavelets

    NASA Astrophysics Data System (ADS)

    Hartman, Jessica

    The purpose of this research was to study neutron spectroscopy using the EJ-299-33A plastic scintillator. This scintillator material provided a novel means of detection for fast neutrons, without the disadvantages of traditional liquid scintillation materials. EJ-299-33A provided a more durable option to these materials, making it less likely to be damaged during handling. Unlike liquid scintillators, this plastic scintillator was manufactured from a non-toxic material, making it safer to use, as well as easier to design detectors. The material was also manufactured with inherent pulse shape discrimination abilities, making it suitable for use in neutron detection. The neutron spectral unfolding technique was developed in two stages. Initial detector response function modeling was carried out through the use of the MCNPX Monte Carlo code. The response functions were developed for a monoenergetic neutron flux. Wavelets were then applied to smooth the response function. The spectral unfolding technique was applied through polynomial fitting and optimization techniques in MATLAB. Verification of the unfolding technique was carried out through the use of experimentally determined response functions. These were measured on the neutron source based on the Van de Graff accelerator at the University of Kentucky. This machine provided a range of monoenergetic neutron beams between 0.1 MeV and 24 MeV, making it possible to measure the set of response functions of the EJ-299-33A plastic scintillator detector to neutrons of specific energies. The response of a plutonium-beryllium (PuBe) source was measured using the source available at the University of Nevada, Las Vegas. The neutron spectrum reconstruction was carried out using the experimentally measured response functions. Experimental data was collected in the list mode of the waveform digitizer. Post processing of this data focused on the pulse shape discrimination analysis of the recorded response functions to remove the

  15. Assay of the Martian Regolith with Neutrons

    NASA Technical Reports Server (NTRS)

    Drake, Darrell M.; Reedy, R.; Jakowsky, B.; Clark, B.; Squyres, S.

    1998-01-01

    Different aspects of assaying Martian regolith using neutrons have been investigated. The epithermal portion of moderated neutrons spectra is dramatically effected by the presence of hydrogen (usually in the form of water). A simple analytic formula has been derived to describe the amplitude of this portion of the neutron spectrum as a function of water concentration. Several demonstration experiments have been performed and modeled with a Monte Carlo code. Results of these experiments generally agreed with the calculations to within 20%. In addition to He-3 detectors, lithium-glass scintillators and U-238 fission ion chambers were investigated to determine their applicability to space experiments.

  16. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  17. Method to Reduce Long-lived Fission Products by Nuclear Transmutations with Fast Spectrum Reactors.

    PubMed

    Chiba, Satoshi; Wakabayashi, Toshio; Tachi, Yoshiaki; Takaki, Naoyuki; Terashima, Atsunori; Okumura, Shin; Yoshida, Tadashi

    2017-10-24

    Transmutation of long-lived fission products (LLFPs: 79 Se, 93 Zr, 99 Tc, 107 Pd, 129 I, and 135 Cs) into short-lived or non-radioactive nuclides by fast neutron spectrum reactors without isotope separation has been proposed as a solution to the problem of radioactive wastes disposal. Despite investigation of many methods, such transmutation remains technologically difficult. To establish an effective and efficient transmutation system, we propose a novel neutron moderator material, yttrium deuteride (YD 2 ), to soften the neutron spectrum leaking from the reactor core. Neutron energy spectra and effective half-lives of LLFPs, transmutation rates, and support ratios were evaluated with the continuous-energy Monte Carlo code MVP-II/MVP-BURN and the JENDL-4.0 cross section library. With the YD 2 moderator in the radial blanket and shield regions, effective half-lives drastically decreased from 106 to 102 years and the support ratios reached 1.0 for all six LLFPs. This successful development and implementation of a transmutation system for LLFPs without isotope separation contributes to a the ability of fast spectrum reactors to reduce radioactive waste by consuming their own LLFPs.

  18. A new method of creating high intensity neutron source

    NASA Astrophysics Data System (ADS)

    Masuda, T.; Yoshimi, A.; Yoshimura, M.

    We propose a new scheme of producing an intense neutron beam whose yields may exceed those of the existing facilities by a few to several orders of magnitude in the sub-eV region. This scheme employs a MeV gamma beam extracted from circulating quantum ions, which has been recently proposed. The gamma beam is directed to a deuteron target and the photo-disintegration process generates a neutron beam. The calculated neutron energy spectrum is nearly flat down to the neV range, and thus there exists a possibility to utilize a good quality of neutrons especially in sub-eV energy region without using a moderator.

  19. Measurement of the secondary neutron dose distribution from the LET spectrum of recoils using the CR-39 plastic nuclear track detector in 10 MV X-ray medical radiation fields

    NASA Astrophysics Data System (ADS)

    Fujibuchi, Toshioh; Kodaira, Satoshi; Sawaguchi, Fumiya; Abe, Yasuyuki; Obara, Satoshi; Yamaguchi, Masae; Kawashima, Hajime; Kitamura, Hisashi; Kurano, Mieko; Uchihori, Yukio; Yasuda, Nakahiro; Koguchi, Yasuhiro; Nakajima, Masaru; Kitamura, Nozomi; Sato, Tomoharu

    2015-04-01

    We measured the recoil charged particles from secondary neutrons produced by the photonuclear reaction in a water phantom from a 10-MV photon beam from medical linacs. The absorbed dose and the dose equivalent were evaluated from the linear energy transfer (LET) spectrum of recoils using the CR-39 plastic nuclear track detector (PNTD) based on well-established methods in the field of space radiation dosimetry. The contributions and spatial distributions of these in the phantom on nominal photon exposures were verified as the secondary neutron dose and neutron dose equivalent. The neutron dose equivalent normalized to the photon-absorbed dose was 0.261 mSv/100 MU at source to chamber distance 90 cm. The dose equivalent at the surface gave the highest value, and was attenuated to less than 10% at 5 cm from the surface. The dose contribution of the high LET component of ⩾100 keV/μm increased with the depth in water, resulting in an increase of the quality factor. The CR-39 PNTD is a powerful tool that can be used to systematically measure secondary neutron dose distributions in a water phantom from an in-field to out-of-field high-intensity photon beam.

  20. Irradiation hardening of pure tungsten exposed to neutron irradiation

    DOE PAGES

    Hu, Xunxiang; Koyanagi, Takaaki; Fukuda, Makoto; ...

    2016-08-26

    In this paper, pure tungsten samples have been neutron irradiated in HFIR at 90–850 °C to 0.03–2.2 dpa. A dispersed barrier hardening model informed by the available microstructure data has been used to predict the hardness. Comparison of the model predictions and the measured Vickers hardness reveals the dominant hardening contribution at various irradiation conditions. For tungsten samples irradiated in HFIR, the results indicate that voids and dislocation loops contributed to the hardness increase in the low dose region (<0.3 dpa), while the formation of intermetallic second phase precipitation, resulting from transmutation, dominates the radiation-induced strengthening beginning with a relativelymore » modest dose (>0.6 dpa). Finally, the precipitate contribution is most pronounced for the HFIR irradiations, whereas the radiation-induced defect cluster microstructure can rationalize the entirety of the hardness increase observed in tungsten irradiated in the fast neutron spectrum of Joyo and the mixed neutron spectrum of JMTR.« less

  1. Browns Ferry Unit-3 cavity neutron spectral analysis. Final report

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Martin, G.C.

    1981-08-01

    This report describes neutron dosimetry measurements performed in the Browns Ferry Unit-3 reactor cavity using multiple dosimeter and spectrum unfolding techniques to assess radiation-induced degradation of nuclear plant pressure vessels. Test results and conclusions indicating the feasibility of determining neutron flux spectra and the densities in the pressure vessel cavity region via dosimetric measurements are presented.

  2. Neutron Depth Profiling: Overview and Description of NIST Facilities

    PubMed Central

    Downing, R. G.; Lamaze, G. P.; Langland, J. K.; Hwang, S. T.

    1993-01-01

    The Cold Neutron Depth Profiling (CNDP) instrument at the NIST Cold Neutron Research Facility (CNRF) is now operational. The neutron beam originates from a 16 L D2O ice cold source and passes through a filter of 135 mm of single crystal sapphire. The neutron energy spectrum may be described by a 65 K Maxwellian distribution. The sample chamber configuration allows for remote controlled scanning of 150 × 150 mm sample areas including the varying of both sample and detector angle. The improved sensitivity over the current thermal depth profiling instrument has permitted the first nondestructive measurements of 17O profiles. This paper describes the CNDP instrument, illustrates the neutron depth profiling (NDP) technique with examples, and gives a separate bibliography of NDP publications. PMID:28053461

  3. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

  4. Poster - 25: Neutron Spectral Measurements around a Scanning Proton Beam

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kildea, John; Enger, Shirin; Maglieri, Robert

    We describe the measurements of neutron spectra that we undertook around a scanning proton beam at the Skandion proton therapy clinic in Uppsala, Sweden. Measurements were undertaken using an extended energy range Nested Neutron Spectrometer (NNS, Detec Inc., Gatineau, QC) operated in pulsed and current mode. Spectra were measured as a function of location in the treatment room and for various Bragg peak depths. Our preliminary unfolded data clearly show the direct, evaporation and thermal neutron peaks and we can show the effect on the neutron spectrum of a water phantom in the primary proton beam.

  5. Improved neutron-gamma discrimination for a 6Li-glass neutron detector using digital signal analysis methods

    DOE PAGES

    Wang, Cai -Lin; Riedel, Richard A.

    2016-01-14

    A 6Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at SNS. Traditional pulse-height analysis (PHA) for neutron-gamma discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10 4. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, five digital signal analysis methods of individual waveforms from PMTs were proposed using: i). pulse-amplitude histogram; ii). power spectrum analysis combined with the maximum pulse amplitude; iii). two event parameters (a 1, b 0) obtained from Wiener filter; iv). anmore » effective amplitude (m) obtained from an adaptive least-mean-square (LMS) filter; and v). a cross-correlation (CC) coefficient between an individual waveform and a reference. The NGD ratios can be 1-102 times those from traditional PHA method. A brighter scintillator GS2 has better NGD ratio than GS20, but lower neutron detection efficiency. The ultimate NGD ratio is related to the ambient, high-energy background events. Moreover, our results indicate the NGD capability of neutron Anger cameras can be improved using digital signal analysis methods and brighter neutron scintillators.« less

  6. Neutron-induced reaction cross-sections of 93Nb with fast neutron based on 9Be(p,n) reaction

    NASA Astrophysics Data System (ADS)

    Naik, H.; Kim, G. N.; Kim, K.; Zaman, M.; Nadeem, M.; Sahid, M.

    2018-02-01

    The cross-sections of the 93Nb (n , 2 n)92mNb, 93Nb (n , 3 n)91mNb and 93Nb (n , 4 n)90Nb reactions with the average neutron energies of 14.4 to 34.0 MeV have been determined by using an activation and off-line γ-ray spectrometric technique. The fast neutrons were produced using the 9Be (p , n) reaction with the proton energies of 25-, 35- and 45-MeV from the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences (KIRAMS). The neutron flux-weighted average cross-sections of the 93Nb(n , xn ; x = 2- 4) reactions were also obtained from the mono-energetic neutron-induced reaction cross-sections of 93Nb calculated using the TALYS 1.8 code, and the neutron flux spectrum based on the MCNPX 2.6.0 code. The present results for the 93Nb(n , xn ; x = 2- 4) reactions are compared with the calculated neutron flux-weighted average values and found to be in good agreement.

  7. Precise determination of neutron binding energy of 64Cu

    NASA Astrophysics Data System (ADS)

    Telezhnikov, S. A.; Granja, C.; Honzatko, J.; Pospisil, S.; Tomandl, I.

    2016-05-01

    The neutron binding energy in 64Cu has been accurately measured in thermal neutron capture. A composite target of natural Cu and NaCl was used on a high flux neutron beam using a large measuring time. The γ-ray spectrum emitted in the ( n, γ) reaction was measured with a HPGe detector in large statistics (up to 106 events per channel). Intrinsic limitations of HPGe detectors, which restrict the accuracy of energy calibration, were determined. The value B n of 64Cu was determined as 7915.867(24) keV.

  8. Signal and background considerations for the MRSt on the National Ignition Facility (NIF).

    PubMed

    Wink, C W; Frenje, J A; Hilsabeck, T J; Bionta, R; Khater, H Y; Gatu Johnson, M; Kilkenny, J D; Li, C K; Séguin, F H; Petrasso, R D

    2016-11-01

    A Magnetic Recoil Spectrometer (MRSt) has been conceptually designed for time-resolved measurements of the neutron spectrum at the National Ignition Facility. Using the MRSt, the goals are to measure the time-evolution of the spectrum with a time resolution of ∼20-ps and absolute accuracy better than 5%. To meet these goals, a detailed understanding and optimization of the signal and background characteristics are required. Through ion-optics, MCNP simulations, and detector-response calculations, it is demonstrated that the goals and a signal-to background >5-10 for the down-scattered neutron measurement are met if the background, consisting of ambient neutrons and gammas, at the MRSt is reduced 50-100 times.

  9. Signal and background considerations for the MRSt on the National Ignition Facility (NIF)

    DOE PAGES

    Wink, C. W.; Frenje, J. A.; Hilsabeck, T. J.; ...

    2016-08-03

    A Magnetic Recoil Spectrometer (MRSt) has been conceptually designed for time-resolved measurements of the neutron spectrum at the National Ignition Facility. Using the MRSt, the goals are to measure the time-evolution of the spectrum with a time resolution of ~20-ps and absolute accuracy better than 5%. To meet these goals, a detailed understanding and optimization of the signal and background characteristics are required. Through ion-optics, MCNP simulations, and detector-response calculations, we demonstrate that the goals and a signal-to background >5-10 for the down-scattered neutron measurement are met if the background, consisting of ambient neutrons and gammas, at the MRSt ismore » reduced 50-100 times.« less

  10. Neutron production mechanism in a plasma focus.

    NASA Technical Reports Server (NTRS)

    Lee, J. H.; Shomo, L. P.; Williams, M. D.; Hermansdorfer, H.

    1971-01-01

    The neutrons emitted by a plasma focus were analyzed by using a time-of-flight method. Flight paths as large as 80 m were used to obtain better than 10% energy resolution. The energy spectrum of neutrons from d-d reactions in the plasma focus shows a sharp onset with average maximum energies of 2.8 and 3.2 MeV in the radial and the axial directions, respectively. The average half-width of the energy spectrum was 270 keV with a shot-to-shot variation between 150 and 400 keV. Simultaneous measurements in the axial and radial directions showed no appreciable difference in the half-widths and thus indicated randomly oriented ion velocities in the plasma. A converging ion model is described which is found to be in agreement with the measured quantities.

  11. Energy spectra unfolding of fast neutron sources using the group method of data handling and decision tree algorithms

    NASA Astrophysics Data System (ADS)

    Hosseini, Seyed Abolfazl; Afrakoti, Iman Esmaili Paeen

    2017-04-01

    Accurate unfolding of the energy spectrum of a neutron source gives important information about unknown neutron sources. The obtained information is useful in many areas like nuclear safeguards, nuclear nonproliferation, and homeland security. In the present study, the energy spectrum of a poly-energetic fast neutron source is reconstructed using the developed computational codes based on the Group Method of Data Handling (GMDH) and Decision Tree (DT) algorithms. The neutron pulse height distribution (neutron response function) in the considered NE-213 liquid organic scintillator has been simulated using the developed MCNPX-ESUT computational code (MCNPX-Energy engineering of Sharif University of Technology). The developed computational codes based on the GMDH and DT algorithms use some data for training, testing and validation steps. In order to prepare the required data, 4000 randomly generated energy spectra distributed over 52 bins are used. The randomly generated energy spectra and the simulated neutron pulse height distributions by MCNPX-ESUT for each energy spectrum are used as the output and input data. Since there is no need to solve the inverse problem with an ill-conditioned response matrix, the unfolded energy spectrum has the highest accuracy. The 241Am-9Be and 252Cf neutron sources are used in the validation step of the calculation. The unfolded energy spectra for the used fast neutron sources have an excellent agreement with the reference ones. Also, the accuracy of the unfolded energy spectra obtained using the GMDH is slightly better than those obtained from the DT. The results obtained in the present study have good accuracy in comparison with the previously published paper based on the logsig and tansig transfer functions.

  12. Application of the coincidence counting technique to DD neutron spectrometry data at the NIF, OMEGA, and Z

    DOE PAGES

    Lahmann, B.; Milanese, L. M.; Han, W.; ...

    2016-07-20

    A compact neutron spectrometer, based on a CH foil for the production of recoil protons and CR-39 detection, is being developed for the measurements of the DD-neutron spectrum at the NIF, OMEGA, and Z facilities. As a CR-39 detector will be used in the spectrometer, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). To reject the background to the required level for measurements of the down-scattered and primary DD-neutron components in the spectrum, the Coincidence Counting Technique (CCT) must be applied to the data. Using a piece of CR-39 exposed to 2.5-MeV protonsmore » at the MIT HEDP accelerator facility and DD-neutrons at Z, a significant improvement of a DD-neutron signal-to-background level has been demonstrated for the first time using the CCT. In conclusion, these results are in excellent agreement with previous work applied to DT neutrons.« less

  13. Application of the coincidence counting technique to DD neutron spectrometry data at the NIF, OMEGA, and Z.

    PubMed

    Lahmann, B; Milanese, L M; Han, W; Gatu Johnson, M; Séguin, F H; Frenje, J A; Petrasso, R D; Hahn, K D; Jones, B

    2016-11-01

    A compact neutron spectrometer, based on a CH foil for the production of recoil protons and CR-39 detection, is being developed for the measurements of the DD-neutron spectrum at the NIF, OMEGA, and Z facilities. As a CR-39 detector will be used in the spectrometer, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). To reject the background to the required level for measurements of the down-scattered and primary DD-neutron components in the spectrum, the Coincidence Counting Technique (CCT) must be applied to the data. Using a piece of CR-39 exposed to 2.5-MeV protons at the MIT HEDP accelerator facility and DD-neutrons at Z, a significant improvement of a DD-neutron signal-to-background level has been demonstrated for the first time using the CCT. These results are in excellent agreement with previous work applied to DT neutrons.

  14. Application of the coincidence counting technique to DD neutron spectrometry data at the NIF, OMEGA, and Z

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lahmann, B.; Milanese, L. M.; Han, W.

    A compact neutron spectrometer, based on a CH foil for the production of recoil protons and CR-39 detection, is being developed for the measurements of the DD-neutron spectrum at the NIF, OMEGA, and Z facilities. As a CR-39 detector will be used in the spectrometer, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). To reject the background to the required level for measurements of the down-scattered and primary DD-neutron components in the spectrum, the Coincidence Counting Technique (CCT) must be applied to the data. Using a piece of CR-39 exposed to 2.5-MeV protonsmore » at the MIT HEDP accelerator facility and DD-neutrons at Z, a significant improvement of a DD-neutron signal-to-background level has been demonstrated for the first time using the CCT. In conclusion, these results are in excellent agreement with previous work applied to DT neutrons.« less

  15. Application of the coincidence counting technique to DD neutron spectrometry data at the NIF, OMEGA, and Z

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lahmann, B., E-mail: lahmann@mit.edu; Milanese, L. M.; Han, W.

    A compact neutron spectrometer, based on a CH foil for the production of recoil protons and CR-39 detection, is being developed for the measurements of the DD-neutron spectrum at the NIF, OMEGA, and Z facilities. As a CR-39 detector will be used in the spectrometer, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). To reject the background to the required level for measurements of the down-scattered and primary DD-neutron components in the spectrum, the Coincidence Counting Technique (CCT) must be applied to the data. Using a piece of CR-39 exposed to 2.5-MeV protonsmore » at the MIT HEDP accelerator facility and DD-neutrons at Z, a significant improvement of a DD-neutron signal-to-background level has been demonstrated for the first time using the CCT. These results are in excellent agreement with previous work applied to DT neutrons.« less

  16. Moderator design studies for a new neutron reference source based on the D-T fusion reaction

    NASA Astrophysics Data System (ADS)

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.; McDonald, Joseph C.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramatically in recent years. Neutron generators based on deuteriumtritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2-5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.

  17. Absolute reactivity calibration of accelerator-driven systems after RACE-T experiments

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Jammes, C. C.; Imel, G. R.; Geslot, B.

    2006-07-01

    The RACE-T experiments that were held in november 2005 in the ENEA-Casaccia research center near Rome allowed us to improve our knowledge of the experimental techniques for absolute reactivity calibration at either startup or shutdown phases of accelerator-driven systems. Various experimental techniques for assessing a subcritical level were inter-compared through three different subcritical configurations SC0, SC2 and SC3, about -0.5, -3 and -6 dollars, respectively. The area-ratio method based of the use of a pulsed neutron source appears as the most performing. When the reactivity estimate is expressed in dollar unit, the uncertainties obtained with the area-ratio method were lessmore » than 1% for any subcritical configuration. The sensitivity to measurement location was about slightly more than 1% and always less than 4%. Finally, it is noteworthy that the source jerk technique using a transient caused by the pulsed neutron source shutdown provides results in good agreement with those obtained from the area-ratio technique. (authors)« less

  18. IMPROVEMENTS IN THE THERMAL NEUTRON CALIBRATION UNIT, TNF2, AT LNMRI/IRD.

    PubMed

    Astuto, A; Fernandes, S S; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

    2018-02-21

    The standard thermal neutron flux unit, TNF2, in the Brazilian National Ionizing Radiation Metrology Laboratory was rebuilt. Fluence is still achieved by moderating of four 241Am-Be sources with 0.6 TBq each. The facility was again simulated and redesigned with graphite core and paraffin added graphite blocks surrounding it. Simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The resulting neutron fluence quality in terms of intensity, spectrum and cadmium ratio was evaluated. After this step, the system was assembled based on the results obtained from the simulations and measurements were performed with equipment existing in LNMRI/IRD and by simulated equipment. This work focuses on the characterization of a central chamber point and external points around the TNF2 in terms of neutron spectrum, fluence and ambient dose equivalent, H*(10). This system was validated with spectra measurements, fluence and H*(10) to ensure traceability.

  19. A neutron spectrum unfolding code based on generalized regression artificial neural networks.

    PubMed

    Del Rosario Martinez-Blanco, Ma; Ornelas-Vargas, Gerardo; Castañeda-Miranda, Celina Lizeth; Solís-Sánchez, Luis Octavio; Castañeda-Miranada, Rodrigo; Vega-Carrillo, Héctor René; Celaya-Padilla, Jose M; Garza-Veloz, Idalia; Martínez-Fierro, Margarita; Ortiz-Rodríguez, José Manuel

    2016-11-01

    The most delicate part of neutron spectrometry, is the unfolding process. The derivation of the spectral information is not simple because the unknown is not given directly as a result of the measurements. Novel methods based on Artificial Neural Networks have been widely investigated. In prior works, back propagation neural networks (BPNN) have been used to solve the neutron spectrometry problem, however, some drawbacks still exist using this kind of neural nets, i.e. the optimum selection of the network topology and the long training time. Compared to BPNN, it's usually much faster to train a generalized regression neural network (GRNN). That's mainly because spread constant is the only parameter used in GRNN. Another feature is that the network will converge to a global minimum, provided that the optimal values of spread has been determined and that the dataset adequately represents the problem space. In addition, GRNN are often more accurate than BPNN in the prediction. These characteristics make GRNNs to be of great interest in the neutron spectrometry domain. This work presents a computational tool based on GRNN capable to solve the neutron spectrometry problem. This computational code, automates the pre-processing, training and testing stages using a k-fold cross validation of 3 folds, the statistical analysis and the post-processing of the information, using 7 Bonner spheres rate counts as only entrance data. The code was designed for a Bonner Spheres System based on a 6 LiI(Eu) neutron detector and a response matrix expressed in 60 energy bins taken from an International Atomic Energy Agency compilation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Observation of the Goos-Hänchen shift with neutrons.

    PubMed

    de Haan, Victor-O; Plomp, Jeroen; Rekveldt, Theo M; Kraan, Wicher H; van Well, Ad A; Dalgliesh, Robert M; Langridge, Sean

    2010-01-08

    The Goos-Hänchen effect is a spatial shift along an interface resulting from an interference effect that occurs for total internal reflection. This phenomenon was suggested by Sir Isaac Newton, but it was not until 1947 that the effect was experimentally observed by Goos and Hänchen. We provide the first direct, absolute, experimental determination of the Goos-Hänchen shift for a particle experiencing a potential well as required by quantum mechanics: namely, wave-particle duality. Here, the particle is a spin-polarized neutron reflecting from a film of magnetized material. We detect the effect through a subtle change in polarization of the neutron. Here, we demonstrate, through experiment and theory, that neutrons do exhibit the Goos-Hänchen effect and postulate that the associated time shift should also be observable.

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

    PubMed

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

    2014-04-01

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

  2. Selective Deuteron Acceleration and Neutron Production on the Vulcan PW Laser

    NASA Astrophysics Data System (ADS)

    Krygier, A. G.; Morrison, J. T.; Freeman, R. R.; Ahmed, H.; Green, J. A.; Alejo, A.; Kar, S.; Vassura, L.

    2014-10-01

    Fast neutron sources are important for a variety of applications including radiography and the detection of sensitive materials. Here we report on the results of an experiment using the Vulcan PW laser at Rutherford Appleton Laboratory to produce a nearly pure deuterium ion beam via Target Normal Sheath Acceleration. The typical contaminants are suppressed by freezing a μ m's thick layer of heavy water vapor (D2 O) onto a cryogenic target during the shot sequence. Neutrons were generated by colliding the accelerated deuterons were into secondary targets made of deuterated plastic in the pitcher-catcher arrangement. Absolute yields for deuterium ions and neutrons are reported. This work is supported by DOE Contract DE-FC02-04ER54789.

  3. Cosmology with negative absolute temperatures

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vieira, J.P.P.; Byrnes, Christian T.; Lewis, Antony, E-mail: J.Pinto-Vieira@sussex.ac.uk, E-mail: ctb22@sussex.ac.uk, E-mail: antony@cosmologist.info

    Negative absolute temperatures (NAT) are an exotic thermodynamical consequence of quantum physics which has been known since the 1950's (having been achieved in the lab on a number of occasions). Recently, the work of Braun et al. [1] has rekindled interest in negative temperatures and hinted at a possibility of using NAT systems in the lab as dark energy analogues. This paper goes one step further, looking into the cosmological consequences of the existence of a NAT component in the Universe. NAT-dominated expanding Universes experience a borderline phantom expansion ( w < -1) with no Big Rip, and their contractingmore » counterparts are forced to bounce after the energy density becomes sufficiently large. Both scenarios might be used to solve horizon and flatness problems analogously to standard inflation and bouncing cosmologies. We discuss the difficulties in obtaining and ending a NAT-dominated epoch, and possible ways of obtaining density perturbations with an acceptable spectrum.« less

  4. EFPI sensor utilizing optical spectrum analyzer with tunable laser: detection of baseline oscillations faster than spectrum acquisition rate

    NASA Astrophysics Data System (ADS)

    Ushakov, Nikolai; Liokumovich, Leonid

    2014-05-01

    A novel approach for extrinsic Fabry-Perot interferometer baseline measurement has been developed. The principles of frequency-scanning interferometry are utilized for registration of the interferometer spectral function, from which the baseline is demodulated. The proposed approach enables one to capture the absolute baseline variations at frequencies much higher than the spectral acquisition rate. Despite the conventional approaches, associating a single baseline indication to the registered spectrum, in the proposed method a modified frequency detection procedure is applied to the spectrum. This provides an ability to capture the baseline variations which took place during the spectrum acquisition. The limitations on the parameters of the possibly registered baseline variations are formulated. The experimental verification of the proposed approach for different perturbations has been performed.

  5. Spallation Neutron Source Materials Studies

    NASA Astrophysics Data System (ADS)

    Sommer, W. F.

    1998-04-01

    Operation of accelerator facilities such as Los Alamos Neutron Science Center (LANSCE), ISIS at Rutherford Appleton Laboratory, the Swiss Institute Neutron Source (SINQ) at Paul Scherrer Institute, and others has provided valuable information on materials performance in high energy particle beams and high energy neutron environments. The Accelerator Production of Tritium (APT) project is sponsoring an extensive series of tests on the effect of spallation neutron source environments to physical and mechanical properties of candidate materials such as nickel-based alloys, stainless steel alloys, aluminum alloys and solid target materials such as tungsten. Measurements of corrosion rates of these candidate materials during irradiation and while in contact with flowing coolant water are being made. The APT tests use the irradiation facility in the beam stop area of the LANSCE accelerator using 800 MeV protons as well as the neutron flux-spectrum generated as these protons interact with targets. The initial irradiations were completed in summer 1997, exposing materials to a fluence approaching 4-6 x 10^21 protons/cm^2. Sample retrieval is now underway. Mechanical properties measurements are being conducted at several laboratories. Studies on components used in service have also been initiated.

  6. First XMM-Newton Observations of an Isolated Neutron Star: RXJ0720.4-3125

    NASA Technical Reports Server (NTRS)

    Paerels, Frits; Mori, Kaya; Motch, Christian; Haberl, Frank; Zavlin, Vyacheslav E.; Zane, Silvia; Ramsay, Gavin; Cropper, Mark

    2000-01-01

    We present the high resolution spectrum of the isolated neutron star RXJ0720.4-3125, obtained with the Reflection Grating Spectrometer on XMM-Newton, complemented with the broad band spectrum observed with the EPIC PN camera. The spectrum appears smooth, with no evidence for strong photospheric absorption or emission features. We briefly discuss the implications of our failure to detect structure in the spectrum.

  7. The energy spectrum of neutrons from 7Li(d,n)8Be reaction at deuteron energy 2.9 MeV

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Konstantin V.; Piksaikin, Vladimir M.; Zolotarev, Konstantin I.; Egorov, Andrey S.; Gremyachkin, Dmitrii E.

    2017-09-01

    The neutron beams generated at the electrostatic accelerators using nuclear reactions T(p,n)3He, D(d,n)3He, 7Li(p,n)7Be, T(d,n)4He, 7Li(d,n)8Be, 9Be(d,n)10B are widely used in neutron physics and in many practical applications. Among these reactions the least studied reactions are 7Li(d,n)8Be and 9Be(d,n)10B. The present work is devoted to the measurement of the neutron spectrum from 7Li(d,n)8Be reaction at 0∘ angle to the deuteron beam axis on the electrostatic accelerator Tandetron (JSC "SSC RF - IPPE") using activation method and a stilbene crystal scintillation detector. The first time ever 7Li(d,n)8Be reaction was measured by activation method. The target was a thick lithium layer on metallic backing. The energy of the incident deuteron was 2.9 MeV. As activation detectors a wide range of nuclear reactions were used: 27Al(n,p)27Mg, 27Al(n,α)24Na, 113In(n,n')113mIn, 115In(n,n')115mIn, 115In(n,γ)116mIn, 58Ni(n,p)58mCo, 58Ni(n,2n)57Ni, 197Au(n,γ)198Au, 197Au(n,2n)196Au, 59Co(n,p)59Fe, 59Co(n,2n)58m+gCo, 59Co (n,g)60Co. Measurement of the induced gamma-activity was carried out using HPGe detector Canberra GX5019 [1]. The up-to-date evaluations of the cross sections for these reactions were used in processing of the data. The program STAYSL was used to unfold the energy spectra. The neutron spectra obtained by activation detectors is consistent with the corresponding data measured by a stilbene crystal scintillation detector within their uncertainties.

  8. General relativistic spectra of accretion discs around rapidly rotating neutron stars: effect of light bending

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Sudip; Bhattacharya, Dipankar; Thampan, Arun V.

    2001-08-01

    We present computed spectra, as seen by a distant observer, from the accretion disc around a rapidly rotating neutron star. Our calculations are carried out in a fully general relativistic framework, with an exact treatment of rotation. We take into account the Doppler shift, gravitational redshift and light-bending effects in order to compute the observed spectrum. We find that light bending significantly modifies the high-energy part of the spectrum. Computed spectra for slowly rotating neutron stars are also presented. These results would be important for modelling the observed X-ray spectra of low-mass X-ray binaries containing fast-spinning neutron stars.

  9. Development of Measurement Methods for Detection of Special Nuclear Materials using D-D Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Misawa, Tsuyoshi; Takahashi, Yoshiyuki; Yagi, Takahiro; Pyeon, Cheol Ho; Kimura, Masaharu; Masuda, Kai; Ohgaki, Hideaki

    2015-10-01

    For detection of hidden special nuclear materials (SNMs), we have developed an active neutron-based interrogation system combined with a D-D fusion pulsed neutron source and a neutron detection system. In the detection scheme, we have adopted new measurement techniques simultaneously; neutron noise analysis and neutron energy spectrum analysis. The validity of neutron noise analysis method has been experimentally studied in the Kyoto University Critical Assembly (KUCA), and was applied to a cargo container inspection system by simulation.

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hatarik, R., E-mail: hatarik1@llnl.gov; Sayre, D. B.; Caggiano, J. A.

    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,more » 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.« less

  11. Prompt γ rays and neutrons from fission

    NASA Astrophysics Data System (ADS)

    Kwan, E.; Wu, C. Y.; Chyzh, A.; Gostic, J.; Henderson, R.; Haight, R. C.; Lee, H. Y.; O'Donnell, J. M.; Perdue, B. A.; Taddeucci, T. N.

    2011-10-01

    Nuclear data are needed to test the accuracy of calculations from nuclear reaction codes. Information on the prompt γ-ray distributions from fission is sparse and only a handful of published experiments data that measured the prompt γ-ray distribution above incident neutron energies of 1 MeV can be found. In addition, improvement on the accuracy and shape of neutron spectrum from the fission of actinides been requested by the nuclear data community. An investigation on the shapes of the neutron and γ-ray distributions from the spontaneous fission of 252Cf and the neutron-induced fission of 235U was undertaken using the Chi-Nu detector array at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. Preliminary results will be presented. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and the Los Alamos National Laboratory under Contract DE-AC52-06NA25396.

  12. Neutron Reference Benchmark Field Specification: ACRR Free-Field Environment (ACRR-FF-CC-32-CL).

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vega, Richard Manuel; Parma, Edward J.; Griffin, Patrick J.

    2015-07-01

    This report was put together to support the International Atomic Energy Agency (IAEA) REAL- 2016 activity to validate the dosimetry community’s ability to use a consistent set of activation data and to derive consistent spectral characterizations. The report captures details of integral measurements taken in the Annular Core Research Reactor (ACRR) central cavity free-field reference neutron benchmark field. The field is described and an “a priori” calculated neutron spectrum is reported, based on MCNP6 calculations, and a subject matter expert (SME) based covariance matrix is given for this “a priori” spectrum. The results of 31 integral dosimetry measurements in themore » neutron field are reported.« less

  13. Improved neutron-gamma discrimination for a {sup 6}Li-glass neutron detector using digital signal analysis methods

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, C. L., E-mail: wangc@ornl.gov; Riedel, R. A.

    2016-01-15

    A {sup 6}Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at Spallation Neutron Source. Traditional Pulse-Height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10{sup 4}. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, six digital signal analysis methods of individual waveforms acquired from photomultiplier tubes were proposed using (i) charge integration, (ii) pulse-amplitude histograms, (iii) power spectrum analysis combined with the maximum pulse-amplitude, (iv) two event parameters (a{sub 1}, b{submore » 0}) obtained from a Wiener filter, (v) an effective amplitude (m) obtained from an adaptive least-mean-square filter, and (vi) a cross-correlation coefficient between individual and reference waveforms. The NGD ratios are about 70 times those from the traditional PHA method. Our results indicate the NGD capabilities of neutron Anger cameras based on GS20 scintillators can be significantly improved with digital signal analysis methods.« less

  14. In-Situ Spectrometry of Neutrons

    NASA Technical Reports Server (NTRS)

    Maurer, Richard H.

    1999-01-01

    High energy charged particles of extra-galactic, galactic and solar origin collide with spacecraft structures in Earth orbit outside the atmosphere and in interplanetary travel beyond the Earth's magnetosphere. These primaries create a number of secondary particles inside the structures that can produce a significant ionizing radiation environment. This radiation is a threat to long term inhabitants or travelers for space missions and produces an increased risk of cancer and DNA damage. The primary high energy cosmic rays and trapped protons collide with common spacecraft materials such as aluminum and silicon and create secondary particles inside structures that are mostly protons and neutrons. Charged protons are readily detected and instruments are already in existence for this task. Neutrons are electrically neutral and therefore much more difficult to measure and detect. These neutrons are reported to contribute 30-60% of the dose inside space structures and cannot be ignored. Currently there is no compact, portable and real time neutron detector instrumentation available for use inside spacecraft or on planetary surfaces where astronauts will live and work. We propose to design and build a portable, low power and robust neutron spectrometer that will measure the neutron spectrum from 10 KeV to 500 MeV with at least 10% energy resolution in the various energy intervals. This instrument will monitor the existing neutron environment both inside spacecraft structures and on planetary surfaces to determine the safest living areas, warn of high fluxes associated with solar storms and assist the NSBRI Radiation Effects Team in making an accurate assessment of increased cancer risk and DNA damage to astronauts. The instrument uses a highly efficient proportional counter Helium 3 tube at the lowest energy intervals where .equivalent damage factors for tissue are the highest (10 KeV-2 MeV). The Helium 3 tube may be shielded with a cadmium absorber to eliminate the much

  15. Event-Based Processing of Neutron Scattering Data

    DOE PAGES

    Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; ...

    2015-09-16

    Many of the world's time-of-flight spallation neutrons sources are migrating to the recording of individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode that preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final errors, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniquesmore » will be shown for comparison.« less

  16. Axial quasinormal modes of static neutron stars in the nonminimal derivative coupling sector of Horndeski gravity: Spectrum and universal relations for realistic equations of state

    NASA Astrophysics Data System (ADS)

    Blázquez-Salcedo, Jose Luis; Eickhoff, Kevin

    2018-05-01

    We study axial quasinormal modes of static neutron stars in the nonminimal derivative coupling sector of Horndeski theory. We focus on the fundamental curvature mode, which we analyze for 10 different equations of state with different matter content. A comparison with the results obtained in pure general relativity reveals that, apart from modifying the spectrum of the frequencies and the damping times of the stars, this theory modifies several universal relations between the modes and physical parameters of the stars that are otherwise matter independent.

  17. Analysis of neutron and gamma-ray streaming along the maze of NRCAM thallium production target room.

    PubMed

    Raisali, G; Hajiloo, N; Hamidi, S; Aslani, G

    2006-08-01

    Study of the shield performance of a thallium-203 production target room has been investigated in this work. Neutron and gamma-ray equivalent dose rates at various points of the maze are calculated by simulating the transport of streaming neutrons, and photons using Monte Carlo method. For determination of neutron and gamma-ray source intensities and their energy spectrum, we have applied SRIM 2003 and ALICE91 computer codes to Tl target and its Cu substrate for a 145 microA of 28.5 MeV protons beam. The MCNP/4C code has been applied with neutron source term in mode n p to consider both prompt neutrons and secondary gamma-rays. Then the code is applied for the prompt gamma-rays as the source term. The neutron-flux energy spectrum and equivalent dose rates for neutron and gamma-rays in various positions in the maze have been calculated. It has been found that the deviation between calculated and measured dose values along the maze is less than 20%.

  18. First direct constraints on Fierz interference in free-neutron β decay

    NASA Astrophysics Data System (ADS)

    Hickerson, K. P.; Sun, X.; Bagdasarova, Y.; Bravo-Berguño, D.; Broussard, L. J.; Brown, M. A.-P.; Carr, R.; Currie, S.; Ding, X.; Filippone, B. W.; García, A.; Geltenbort, P.; Hoagland, J.; Holley, A. T.; Hong, R.; Ito, T. M.; Knecht, A.; Liu, C.-Y.; Liu, J. L.; Makela, M.; Mammei, R. R.; Martin, J. W.; Melconian, D.; Mendenhall, M. P.; Moore, S. D.; Morris, C. L.; Pattie, R. W.; Pérez Galván, A.; Picker, R.; Pitt, M. L.; Plaster, B.; Ramsey, J. C.; Rios, R.; Saunders, A.; Seestrom, S. J.; Sharapov, E. I.; Sondheim, W. E.; Tatar, E.; Vogelaar, R. B.; VornDick, B.; Wrede, C.; Young, A. R.; Zeck, B. A.; UCNA Collaboration

    2017-10-01

    Precision measurements of free-neutron β decay have been used to precisely constrain our understanding of the weak interaction. However, the neutron Fierz interference term bn, which is particularly sensitive to beyond-standard-model tensor currents at the TeV scale, has thus far eluded measurement. Here we report the first direct constraints on this term, finding bn=0.067 ±0 .005stat-0.061+0.090sys , consistent with the standard model. The uncertainty is dominated by absolute energy reconstruction and the linearity of the β spectrometer energy response.

  19. Warhead verification as inverse problem: Applications of neutron spectrum unfolding from organic-scintillator measurements

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lawrence, Chris C.; Flaska, Marek; Pozzi, Sara A.

    2016-08-14

    Verification of future warhead-dismantlement treaties will require detection of certain warhead attributes without the disclosure of sensitive design information, and this presents an unusual measurement challenge. Neutron spectroscopy—commonly eschewed as an ill-posed inverse problem—may hold special advantages for warhead verification by virtue of its insensitivity to certain neutron-source parameters like plutonium isotopics. In this article, we investigate the usefulness of unfolded neutron spectra obtained from organic-scintillator data for verifying a particular treaty-relevant warhead attribute: the presence of high-explosive and neutron-reflecting materials. Toward this end, several improvements on current unfolding capabilities are demonstrated: deuterated detectors are shown to have superior response-matrixmore » condition to that of standard hydrogen-base scintintillators; a novel data-discretization scheme is proposed which removes important detector nonlinearities; and a technique is described for re-parameterizing the unfolding problem in order to constrain the parameter space of solutions sought, sidestepping the inverse problem altogether. These improvements are demonstrated with trial measurements and verified using accelerator-based time-of-flight calculation of reference spectra. Then, a demonstration is presented in which the elemental compositions of low-Z neutron-attenuating materials are estimated to within 10%. These techniques could have direct application in verifying the presence of high-explosive materials in a neutron-emitting test item, as well as other for treaty verification challenges.« less

  20. Warhead verification as inverse problem: Applications of neutron spectrum unfolding from organic-scintillator measurements

    NASA Astrophysics Data System (ADS)

    Lawrence, Chris C.; Febbraro, Michael; Flaska, Marek; Pozzi, Sara A.; Becchetti, F. D.

    2016-08-01

    Verification of future warhead-dismantlement treaties will require detection of certain warhead attributes without the disclosure of sensitive design information, and this presents an unusual measurement challenge. Neutron spectroscopy—commonly eschewed as an ill-posed inverse problem—may hold special advantages for warhead verification by virtue of its insensitivity to certain neutron-source parameters like plutonium isotopics. In this article, we investigate the usefulness of unfolded neutron spectra obtained from organic-scintillator data for verifying a particular treaty-relevant warhead attribute: the presence of high-explosive and neutron-reflecting materials. Toward this end, several improvements on current unfolding capabilities are demonstrated: deuterated detectors are shown to have superior response-matrix condition to that of standard hydrogen-base scintintillators; a novel data-discretization scheme is proposed which removes important detector nonlinearities; and a technique is described for re-parameterizing the unfolding problem in order to constrain the parameter space of solutions sought, sidestepping the inverse problem altogether. These improvements are demonstrated with trial measurements and verified using accelerator-based time-of-flight calculation of reference spectra. Then, a demonstration is presented in which the elemental compositions of low-Z neutron-attenuating materials are estimated to within 10%. These techniques could have direct application in verifying the presence of high-explosive materials in a neutron-emitting test item, as well as other for treaty verification challenges.

  1. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. © 2013 John Wiley & Sons Ltd.

  2. Detailed characterisation of the incident neutron beam on the TOSCA spectrometer

    NASA Astrophysics Data System (ADS)

    Pinna, Roberto S.; Rudić, Svemir; Capstick, Matthew J.; McPhail, David J.; Pooley, Daniel E.; Howells, Gareth D.; Gorini, Giuseppe; Fernandez-Alonso, Felix

    2017-10-01

    We report a detailed characterisation of the incident neutron beam on the TOSCA spectrometer. A bespoke time-of-flight neutron monitor has been designed, constructed and used to perform extensive spatially resolved measurements of the absolute neutron flux and its underlying time structure at the instrument sample position. The obtained data give a quantitative understanding of the current instrument beyond neutronic simulations and provide a baseline in order to assess the performance of the upgraded instrument. At an average proton current-on-target of 153 μA (ISIS Target Station 1; at the time of measurements) we have found that the wavelength-integrated neutron flux (from 0.28 Å to 4.65 Å) at the position of the TOSCA instrument sample (spatially averaged across the 3 × 3cm2 surface centred around (0,0) position) is approximately 1 . 2 × 106 neutrons cm-2s-1, while the whole beam has a homogeneous distribution across the 3 . 0 × 3 . 5cm2 sample surface. The spectra reproduced the well-known shape of the neutrons moderated by the room temperature water moderator and exhibit a neutron flux of 7 . 3 × 105 neutrons cm-2s-1Å-1 at 1 Å.

  3. A portable neutron spectroscope (NSPECT) for detection, imaging and identification of nuclear material

    NASA Astrophysics Data System (ADS)

    Ryan, James M.; Bancroft, Christopher; Bloser, Peter; Bravar, Ulisse; Fourguette, Dominique; Frost, Colin; Larocque, Liane; McConnell, Mark L.; Legere, Jason; Pavlich, Jane; Ritter, Greg; Wassick, Greg; Wood, Joshua; Woolf, Richard

    2010-08-01

    We have developed, fabricated and tested a prototype imaging neutron spectrometer designed for real-time neutron source location and identification. Real-time detection and identification is important for locating materials. These materials, specifically uranium and transuranics, emit neutrons via spontaneous or induced fission. Unlike other forms of radiation (e.g. gamma rays), penetrating neutron emission is very uncommon. The instrument detects these neutrons, constructs images of the emission pattern, and reports the neutron spectrum. The device will be useful for security and proliferation deterrence, as well as for nuclear waste characterization and monitoring. The instrument is optimized for imaging and spectroscopy in the 1-20 MeV range. The detection principle is based upon multiple elastic neutron-proton scatters in organic scintillator. Two detector panel layers are utilized. By measuring the recoil proton and scattered neutron locations and energies, the direction and energy spectrum of the incident neutrons can be determined and discrete and extended sources identified. Event reconstruction yields an image of the source and its location. The hardware is low power, low mass, and rugged. Its modular design allows the user to combine multiple units for increased sensitivity. We will report the results of laboratory testing of the instrument, including exposure to a calibrated Cf-252 source. Instrument parameters include energy and angular resolution, gamma rejection, minimum source identification distances and times, and projected effective area for a fully populated instrument.

  4. Transport of Neutrons and Photons Through Iron and Water Layers

    NASA Astrophysics Data System (ADS)

    Košťál, Michal; Cvachovec, František; Ošmera, Bohumil; Hansen, Wolfgang; Noack, Klaus

    2009-08-01

    The neutron and photon spectra were measured after iron and water plates placed at the horizontal channel of the Dresden University reactor AK-2. The measurements have been performed with the multiparameter spectrometer [1] with a stilbene cylindrical crystal, 10 × 10 mm or 45 × 45 mm; the neutron and photon spectra have been measured simultaneously. The calculations were performed with the MCNP code and nuclear data libraries ENDF/B VI.2, ENDF/BVII.0, JENDL 3.3 and JEFF 3.1. The measured channel leakage spectrum was used as the input spectrum for the transport calculation. Photons, the primary photons from the reactor - as well as the ones induced by neutron interaction - were calculated. The comparison of the measurements and calculations through 10 cm of iron and 20 cm thickness of water are presented. Besides that, the attenuation of the radiation mixed field by iron layers from 5 to 30 cm is presented; the measured and calculated data are compared.

  5. The Spectrum of Single Bubble Sonoluminescence.

    NASA Astrophysics Data System (ADS)

    Hiller, Robert Anthony

    1995-01-01

    An acoustically levitated bubble in a liquid may be driven to produce short flashes of light synchronous with the sound field in a process called sonoluminescence. The spectrum of the emitted light is measured with a grating monochromator and calibrated for absolute spectral radiance. The spectrum has been measured for various gases dissolved in pure water and heavy water, and alcohols and other hydrocarbon liquids. At a bandpass of 10nm EWHM the spectra are broad -band, showing no sign of lines or absorptions, with a peak in the ultraviolet. The experimental apparatus, including a system for producing sonoluminescence in a sealed container, is described.

  6. Neutron Activation Diagnostics in Deuterium Gas-Puff Experiments on the 3 MA GIT-12 Z-Pinch

    NASA Astrophysics Data System (ADS)

    Cikhardt, J.; Klir, D.; Rezac, K.; Cikhardtova, B.; Kravarik, J.; Kubes, P.; Sila, O.; Shishlov, A. V.; Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.; Turek, K.

    2016-10-01

    The experiments with a deuterium z-pinch on the GIT-12 generator at IHCE in Tomsk were performed in the frame of the Czech-Russian agreement. A set of neutron diagnostics included scintillation time-of-flight detectors, bubble detectors, and several kinds of threshold nuclear activation detectors in the order to obtain information about the yield, anisotropy, and spectrum of the neutrons produced by a deuterium gas-puff. The average neutron yield in these experiments was of the order of 1012 neutrons per a single shot. The energy spectrum of the produced neutrons was evaluated using neutron time-of-flight detectors and a set of neutron activation detectors. Because the deuterons in the pinch achieve multi-MeV energies, non-DD neutrons are produced by nuclear reactions of deuterons with a stainless steel vacuum chamber and aluminum components of diagnostics inside the chamber. An estimated number of the non-DD was of the order of 1011. GACR (Grant No. 16-07036S), CME (Grant Nos. LD14089, LG13029, and LH13283), MESRF (Grant No. RFMEFI59114X0001), IAEA (Grant No. RC17088), CTU (Grant No. SGS 16/223/OHK3/3T/13).

  7. Astroseismology of neutron stars from gravitational waves in the limit of perfect measurement

    NASA Astrophysics Data System (ADS)

    Suvorov, A. G.

    2018-04-01

    The oscillation spectrum of a perturbed neutron star is intimately related to the physical properties of the star, such as the equation of state. Observing pulsating neutron stars therefore allows one to place constraints on these physical properties. However, it is not obvious exactly how much can be learnt from such measurements. If we observe for long enough, and precisely enough, is it possible to learn everything about the star? A classical result in the theory of spectral geometry states that one cannot uniquely `hear the shape of a drum'. More formally, it is known that an eigenfrequency spectrum may not uniquely correspond to a particular geometry; some `drums' may be indistinguishable from a normal-mode perspective. In contrast, we show that the drum result does not extend to perturbations of simple neutron stars within general relativity - in the case of axial (toroidal) perturbations of static, perfect fluid stars, a quasi-normal mode spectrum uniquely corresponds to a stellar profile. We show in this paper that it is not possible for two neutron stars, with distinct fluid profiles, to oscillate in an identical manner. This result has the information-theoretic consequence that gravitational waves completely encode the properties of any given oscillating star: unique identifications are possible in the limit of perfect measurement.

  8. Astroseismology of neutron stars from gravitational waves in the limit of perfect measurement

    NASA Astrophysics Data System (ADS)

    Suvorov, A. G.

    2018-07-01

    The oscillation spectrum of a perturbed neutron star is intimately related to the physical properties of the star, such as the equation of state. Observing pulsating neutron stars therefore allows one to place constraints on these physical properties. However, it is not obvious exactly how much can be learnt from such measurements. If we observe for long enough, and precisely enough, is it possible to learn everything about the star? A classical result in the theory of spectral geometry states that one cannot uniquely `hear the shape of a drum'. More formally, it is known that an eigenfrequency spectrum may not uniquely correspond to a particular geometry; some `drums' may be indistinguishable from a normal-mode perspective. In contrast, we show that the drum result does not extend to perturbations of simple neutron stars within general relativity - in the case of axial (toroidal) perturbations of static, perfect fluid stars, a quasi-normal mode spectrum uniquely corresponds to a stellar profile. We show in this paper that it is not possible for two neutron stars, with distinct fluid profiles, to oscillate in an identical manner. This result has the information-theoretic consequence that gravitational waves completely encode the properties of any given oscillating star: unique identifications are possible in the limit of perfect measurement.

  9. Moderator design studies for a new neutron reference source based on the D–T fusion reaction

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramaticallymore » in recent years. Neutron generators based on deuterium-tritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14.6 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2 to 5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.« less

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

    DOE PAGES

    Goddard, Braden; Croft, Stephen; Lousteau, Angela; ...

    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

  11. 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.

  12. Cryostat system for investigation on new neutron moderator materials at reactor TRIGA PUSPATI

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dris, Zakaria bin, E-mail: zakariadris@gmail.com; Centre for Nuclear Energy, Universiti Tenaga Nasional; Mohamed, Abdul Aziz bin

    2016-01-22

    A simple continuous flow (SCF) cryostat was designed to investigate the neutron moderation of alumina in high temperature co-ceramic (HTCC) and polymeric materials such as Teflon under TRIGA neutron environment using a reflected neutron beam from a monochromator. Cooling of the cryostat will be carried out using liquid nitrogen. The cryostat will be built with an aluminum holder for moderator within stainless steel cylinder pipe. A copper thermocouple will be used as the temperature sensor to monitor the moderator temperature inside the cryostat holder. Initial measurements of neutron spectrum after neutron passing through the moderating materials have been carried outmore » using a neutron spectrometer.« less

  13. Stellar neutron capture cross sections of 41K and 45Sc

    NASA Astrophysics Data System (ADS)

    Heil, M.; Plag, R.; Uberseder, E.; Bisterzo, S.; Käppeler, F.; Mengoni, A.; Pignatari, M.

    2016-05-01

    The neutron capture cross sections of light nuclei (A <56 ) are important for s -process scenarios since they act as neutron poisons. We report on measurements of the neutron capture cross sections of 41K and 45Sc, which were performed at the Karlsruhe 3.7 MV Van de Graaff accelerator via the activation method in a quasistellar neutron spectrum corresponding to a thermal energy of k T =25 keV. Systematic effects were controlled by repeated irradiations, resulting in overall uncertainties of less than 3%. The measured spectrum-averaged data have been used to normalize the energy-dependent (n ,γ ) cross sections from the main data libraries JEFF-3.2, JENDL-4.0, and ENDF/B-VII.1, and a set of Maxwellian averaged cross sections was calculated for improving the s -process nucleosynthesis yields in AGB stars and in massive stars. At k T =30 keV, the new Maxwellian averaged cross sections of 41K and 45Sc are 19.2 ±0.6 mb and 61.3 ±1.8 mb, respectively. Both values are 20% lower than previously recommended. The effect of neutron poisons is discussed for nuclei with A <56 in general and for the investigated isotopes in particular.

  14. Neutron Analysis - Skylab Student Experiment ED-76

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The rate of neutron flow is commonly referred to as a flux. The measurement of neutron fluxes in Skylab was the subject of a proposal by Terry Quist of San Antonio, Texas. This chart describes Quist's experiment, Neutron Analysis, Skylab student experiment ED-76. These measurements were considered important not only by NASA but also by the scientific community for four reasons. High energy neutrons can be harmful to human tissue if they are present in significant quantities. Fluxes of neutrons can damage film and other sensitive experimental equipment in a marner similar to those produced by x-rays or other radiation. Furthermore, neutron fluxes can be used as a calibration source for other space-oriented particle physics experiments. Finally, neutron fluxes can affect sensitive x-ray and gamma-ray astronomy observations. Quist's objectives were to measure the neutron fluxes present in Skylab and, with the assistance of NASA and other physicists, to attempt determination of their origin as well as their energy range or spectrum. This experiment had stimulated interest in further studies of neutron phenomena in space. In March 1972, NASA and the National Science Teachers Association selected 25 experiment proposals for flight on Skylab. Science advisors from the Marshall Space Flight Center aided and assisted the students in developing the proposals for flight on Skylab.

  15. A study of neutron leakage through an Fe shield at an accelerator.

    PubMed

    Elwyn, A J; Cossairt, J D

    1986-12-01

    The spectrum of neutrons, produced in the interactions of hadrons with energies up to several hundred GeV, that are emitted through a large Fe electro magnet has been determined by use of a multisphere spectrometer both before and after the shielding was augmented with concrete. The existence of leakage neutrons at energies of approximately 0.005-1.0 MeV was verified in the initial configuration, and found to be completely eliminated in the spectrum obtained after the concrete was added. The quality factor of the radiation field was measured; the values are reduced from about six to three with the extra shielding. Additional fluence measurements in the environs of the magnet can be interpreted in terms of a skyshine mechanism with source and attenuation parameters consistent with the energies and intensity of the leakage neutrons.

  16. Development of neutron-monitor detector using liquid organic scintillator coupled with 6Li + ZnS(Ag) Sheet.

    PubMed

    Sato, Tatsuhiko; Endo, Akira; Yamaguchi, Yasuhiro; Takahashi, Fumiaki

    2004-01-01

    A phoswitch-type detector has been developed for monitoring neutron doses in high-energy accelerator facilities. The detector is composed of a liquid organic scintillator (BC501A) coupled with ZnS(Ag) sheets doped with 6Li. The dose from neutrons with energies above 1 MeV is evaluated from the light output spectrum of the BC501A by applying the G-function, which relates the spectrum to the neutron dose directly. The dose from lower energy neutrons, on the other hand, is estimated from the number of scintillations emitted from the ZnS(Ag) sheets. Characteristics of the phoswitch-type detector were studied experimentally in some neutron fields. It was found from the experiments that the detector has an excellent property of pulse-shape discrimination between the scintillations of BC501A and the ZnS(Ag) sheets. The experimental results also indicate that the detector is capable of reproducing doses from thermal neutrons as well as neutrons with energies from one to several tens of megaelectronvolts (MeV).

  17. Signal and background considerations for the MRSt on the National Ignition Facility (NIF)

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wink, C. W., E-mail: cwink@mit.edu; Frenje, J. A.; Gatu Johnson, M.

    2016-11-15

    A Magnetic Recoil Spectrometer (MRSt) has been conceptually designed for time-resolved measurements of the neutron spectrum at the National Ignition Facility. Using the MRSt, the goals are to measure the time-evolution of the spectrum with a time resolution of ∼20-ps and absolute accuracy better than 5%. To meet these goals, a detailed understanding and optimization of the signal and background characteristics are required. Through ion-optics, MCNP simulations, and detector-response calculations, it is demonstrated that the goals and a signal-to background >5–10 for the down-scattered neutron measurement are met if the background, consisting of ambient neutrons and gammas, at the MRStmore » is reduced 50–100 times.« less

  18. The US Spallation Neutron Source Project

    NASA Astrophysics Data System (ADS)

    Olsen, David K.

    1997-10-01

    Slow neutrons, with wavelengths between a few tenths to a few tens of angstroms, are an important probe for condensed-matter physics and are produced with either fission reactors or accelerator-based spallation sources. The Spallation Neutron Source (SNS) is a collaborative project between DOE National Laboratories including LBNL, LANL, BNL, ANL and ORNL to build the next research neutron source in the US. This source will be sited at ORNL and is being designed to serve the needs of the neutron science community well into the next century. The SNS consists of a 1.1-mA H- front end and a 1.0-GeV high-intensity pulsed proton linac. The 1-ms pulses from the linac will be compressed in a 221-m-circumference accumulator ring to produce 600-ns pulses at a 60-Hz rate. This accelerator system will produce spallation neutrons from a 1.0-MW liquid Hg target for a broad spectrum of neutron scattering research with an initial target hall containing 18 instruments. The baseline conceptual design, critical issues, upgrade possibilities, and the collaborative arrangement will be discussed. It is expected that SNS construction will commence in FY99 and, following a seven year project, start operation in 2006.

  19. Thermal-neutron capture for A=26-35

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chunmei, Z.; Firestone, R.B.

    2001-06-01

    The prompt gamma-ray data of thermal- neutron captures fornuclear mass number A=26-35 had been evaluated and published in "ATOMICDATA AND NUCLEAR DATA TABLES, 26, 511 (1981)". Since that time themanyexperimental data of the thermal-neutron captures have been measuredand published. The update of the evaluated prompt gamma-ray data is verynecessary for use in PGAA of high-resolution analytical prompt gamma-rayspectroscopy. Besides, the evaluation is also very needed in theEvaluated Nuclear Structure Data File, ENSDF, because there are no promptgamma-ray data in ENSDF. The levels, prompt gamma-rays and decay schemesof thermal-neutron captures for nuclides (26Mg, 27Al, 28Si, 29Si, 30Si,31P, 32S, 33S, 34S, andmore » 35Cl) with nuclear mass number A=26-35 have beenevaluated on the basis of all experimental data. The normalizationfactors, from which absolute prompt gamma-ray intensity can be obtained,and necessary comments are given in the text. The ENSDF format has beenadopted in this evaluation. The physical check (intensity balance andenergy balance) of evaluated thermal-neutron capture data has been done.The evaluated data have been put into Evaluated Nuclear Structure DataFile, ENSDF. This evaluation may be considered as an update of the promptgamma-ray from thermal-neutron capture data tables as published in"ATOMIC DATA AND NUCLEAR DATA TABLES, 26, 511 (1981)".« less

  20. Thermal-neutron capture for A=36-44

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Chunmei, Z.; Firestone, R.B.

    2003-01-01

    The prompt gamma-ray data of thermal- neutron captures fornuclear mass number A=26-35 had been evaluated and published in "ATOMICDATA AND NUCLEAR DATA TABLES, 26, 511 (1981)". Since that time the manyexperimental data of the thermal-neutron captures have been measured andpublished. The update of the evaluated prompt gamma-ray data is verynecessary for use in PGAA of high-resolution analytical prompt gamma-rayspectroscopy. Besides, the evaluation is also very needed in theEvaluated Nuclear Structure Data File, ENSDF, because there are no promptgamma-ray data in ENSDF. The levels, prompt gamma-rays and decay schemesof thermal-neutron captures fornuclides (26Mg, 27Al, 28Si, 29Si, 30Si,31P, 32S, 33S, 34S, andmore » 35Cl) with nuclear mass number A=26-35 have beenevaluated on the basis of all experimental data. The normalizationfactors, from which absolute prompt gamma-ray intensity can be obtained,and necessary comments are given in the text. The ENSDF format has beenadopted in this evaluation. The physical check (intensity balance andenergy balance) of evaluated thermal-neutron capture data has been done.The evaluated data have been put into Evaluated Nuclear Structure DataFile, ENSDF. This evaluation may be considered as an update of the promptgamma-ray from thermal-neutron capture data tables as published in"ATOMIC DATA AND NUCLEAR DATA TABLES, 26, 511 (1981)".« less

  1. Neutron stars: Observational diversity and evolution

    NASA Astrophysics Data System (ADS)

    Safi-Harb, S.

    2017-12-01

    Ever since the discovery of the Crab and Vela pulsars in their respective Supernova Remnants, our understanding of how neutron stars manifest themselves observationally has been dramatically shaped by the surge of discoveries and dedicated studies across the electromagnetic spectrum, particularly in the high-energy band. The growing diversity of neutron stars includes the highly magnetized neutron stars (magnetars) and the Central Compact Objects shining in X-rays and mostly lacking pulsar wind nebulae. These two subclasses of high-energy objects, however, seem to be characterized by anomalously high or anomalously low surface magnetic fields (thus dubbed as ‘magnetars’ and ‘anti-magnetars’, respectively), and have pulsar characteristic ages that are often much offset from their associated SNRs’ ages. In addition, some neutron stars act ‘schizophrenic’ in that they occasionally display properties that seem common to more than one of the defined subclasses. I review the growing diversity of neutron stars from an observational perspective, then highlight recent and on-going theoretical and observational work attempting to address this diversity, particularly in light of their magnetic field evolution, energy loss mechanisms, and supernova progenitors’ studies.

  2. Jasminum flexile flower absolute from India--a detailed comparison with three other jasmine absolutes.

    PubMed

    Braun, Norbert A; Kohlenberg, Birgit; Sim, Sherina; Meier, Manfred; Hammerschmidt, Franz-Josef

    2009-09-01

    Jasminum flexile flower absolute from the south of India and the corresponding vacuum headspace (VHS) sample of the absolute were analyzed using GC and GC-MS. Three other commercially available Indian jasmine absolutes from the species: J. sambac, J. officinale subsp. grandiflorum, and J. auriculatum and the respective VHS samples were used for comparison purposes. One hundred and twenty-one compounds were characterized in J. flexile flower absolute, with methyl linolate, benzyl salicylate, benzyl benzoate, (2E,6E)-farnesol, and benzyl acetate as the main constituents. A detailed olfactory evaluation was also performed.

  3. Cosmic-ray neutron simulations and measurements in Taiwan.

    PubMed

    Chen, Wei-Lin; Jiang, Shiang-Huei; Sheu, Rong-Jiun

    2014-10-01

    This study used simulations of galactic cosmic ray in the atmosphere to investigate the neutron background environment in Taiwan, emphasising its altitude dependence and spectrum variation near interfaces. The calculated results were analysed and compared with two measurements. The first measurement was a mobile neutron survey from sea level up to 3275 m in altitude conducted using a car-mounted high-sensitivity neutron detector. The second was a previous measured result focusing on the changes in neutron spectra near air/ground and air/water interfaces. The attenuation length of cosmic-ray neutrons in the lower atmosphere was estimated to be 163 g cm(-2) in Taiwan. Cosmic-ray neutron spectra vary with altitude and especially near interfaces. The determined spectra near the air/ground and air/water interfaces agree well with measurements for neutrons below 10 MeV. However, the high-energy portion of spectra was observed to be much higher than our previous estimation. Because high-energy neutrons contribute substantially to a dose evaluation, revising the annual sea-level effective dose from cosmic-ray neutrons at ground level in Taiwan to 35 μSv, which corresponds to a neutron flux of 5.30 × 10(-3) n cm(-2) s(-1), was suggested. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Measurement of the energy and multiplicity distributions of neutrons from the photofission of U 235

    DOE PAGES

    Clarke, S. D.; Wieger, B. M.; Enqvist, A.; ...

    2017-06-20

    For the first time, the complete neutron multiplicity distribution has been measured in this study from the photofission of 235U induced by high-energy spallation γ rays arriving ahead of the neutron beam at the Los Alamos Neutron Science Center. The resulting average neutron multiplicity 3.80 ± 0.08 (stat.) neutrons per photofission is in general agreement with previous measurements. In addition, unique measurements of the prompt fission energy spectrum of the neutrons from photofission and the angular correlation of two-neutron energies emitted in photofission also were made. Finally, the results are compared to calculations with the complete event fission model FREYA.

  5. Time dependent worldwide distribution of atmospheric neutrons and of their products. I, II, III.

    NASA Technical Reports Server (NTRS)

    Merker, M.; Light, E. S.; Verschell, H. J.; Mendell, R. B.; Korff, S. A.

    1973-01-01

    Review of the experimental results obtained in a series of measurements of the fast neutron cosmic ray spectrum by means of high-altitude balloons and aircraft. These results serve as a basis for checking a Monte Carlo calculation of the entire neutron distribution and its products. A calculation of neutron production and transport in the earth's atmosphere is then discussed for the purpose of providing a detailed description of the morphology of secondary neutron components. Finally, an analysis of neutron observations during solar particle events is presented. The Monte Carlo output is used to estimate the contribution of flare particles to fluctuations in the steady state neutron distributions.

  6. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    industry, from the initial fuel enrichment and fabrication processes right through to storage or reprocessing, and neutron metrology is clearly important in this area. Neutron fields do, however, occur in other areas, for example where neutron sources are used in oil well logging and moisture measurements. They also occur around high energy accelerators, including photon linear accelerators used for cancer therapy, and are expected to be a more serious problem around the new hadron radiation therapy facilities. Roughly 50% of the cosmic ray doses experienced by fliers at the flight altitudes of commercial aircraft are due to neutrons. Current research on fusion presents neutron metrology with a whole new range of challenges because of the very high fluences expected. One of the most significant features of neutron fields is the very wide range of possible neutron energies. In the nuclear industry, for example, neutrons occur with energies from those of thermal neutrons at a few meV to the upper end of the fission spectrum at perhaps 10 MeV. For cosmic ray dosimetry the energy range extends into the GeV region. This enormous range sets a challenge for designing measuring devices and a parallel challenge of developing measurement standards for characterizing these devices. One of the major considerations when deciding on topics for this special issue was agreeing on what not to include. Modelling, i.e. the use of radiation transport codes, is now a very important aspect of neutron measurements. These calculations are vital for shielding and for instrument design; nevertheless, the topic has only been included here where it has a direct bearing on metrology and the development of standards. Neutron spectrometry is an increasingly important technique for unravelling some of the problems of dose equivalent measurements and for plasma diagnostics in fusion research. However, this topic is at least one step removed from primary metrology and so it was felt that it should not be

  7. Electron volt spectroscopy on a pulsed neutron source

    NASA Astrophysics Data System (ADS)

    Newport, R. J.; Penfold, J.; Williams, W. G.

    1984-07-01

    The principal design aspects of a pulsed source neutron spectrometer in which the scattered neutron energy is determined by a resonance absorption filter difference method are discussed. Calculations of the accessible dynamic range, resolution and spectrum simulations are given for the spectrometer on a high intensity pulsed neutron source, such as the spallation neutron source (SNS) now being constructed at the Rutherford Appleton Laboratory. Special emphasis is made of the advantage gained by placing coarse and fixed energy-sensitive filters before and after the scatterer; these enhance the inelastic/elastic descrimination of the method. A brief description is given of a double difference filter method which gives a superior difference peak shape, as well as a better energy transfer resolution. Finally, some first results of scattering from zirconium hydride, obtained on a test spectrometer, are presented.

  8. THE POLARIZATION OF NEUTRONS FROM THE STRIPPING OF DEUTERONS ON C$sup 1$$sup 2$

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Budzanowski, A.; Grotowski, K.; Niewodniczanski, H.

    1961-01-01

    The neutron polarization in the reaction C/sup 12/(d,n)N/sup 13/ at 12.9 Mev is measured as a function of the neutron emission angle. In addition, the neutron energy spectrum is measured at a fixed angle, in order to find the relative numbers of neutrons associated with various energy levels of N/sup 13/. The measured data are used to induce the properties of the N/sup 13/ energy levels studied. (T.F.H.)

  9. Characterization of the CALIBAN Critical Assembly Neutron Spectra using Several Adjustment Methods Based on Activation Foils Measurement

    NASA Astrophysics Data System (ADS)

    Casoli, Pierre; Grégoire, Gilles; Rousseau, Guillaume; Jacquet, Xavier; Authier, Nicolas

    2016-02-01

    CALIBAN is a metallic critical assembly managed by the Criticality, Neutron Science and Measurement Department located on the French CEA Center of Valduc. The reactor is extensively used for benchmark experiments dedicated to the evaluation of nuclear data, for electronic hardening or to study the effect of the neutrons on various materials. Therefore CALIBAN irradiation characteristics and especially its central cavity neutron spectrum have to be very accurately evaluated. In order to strengthen our knowledge of this spectrum, several adjustment methods based on activation foils measurements are being studied for a few years in the laboratory. Firstly two codes included in the UMG package have been tested and compared: MAXED and GRAVEL. More recently, the CALIBAN cavity spectrum has been studied using CALMAR, a new adjustment tool currently under development at the CEA Center of Cadarache. The article will discuss and compare the results and the quality of spectrum rebuilding obtained with the UMG codes and with the CALMAR software, from a set of activation measurements carried out in the CALIBAN irradiation cavity.

  10. Deuterated scintillators and their application to neutron spectroscopy

    NASA Astrophysics Data System (ADS)

    Febbraro, M.; Lawrence, C. C.; Zhu, H.; Pierson, B.; Torres-Isea, R. O.; Becchetti, F. D.; Kolata, J. J.; Riggins, J.

    2015-06-01

    Deuterated scintillators have been used as a tool for neutron spectroscopy without Neutron Time-of-Flight (n-ToF) for more than 30 years. This article will provide a brief historical overview of the technique and current uses of deuterated scintillators in the UM-DSA and DESCANT arrays. Pulse-shape discrimination and spectrum unfolding with the maximum-likelihood expectation maximization algorithm will be discussed. Experimental unfolding and cross section results from measurements of (d,n), (3He,n) and (α,n) reactions are shown.

  11. Neutrons produced by known energies of ions abundant in space

    NASA Technical Reports Server (NTRS)

    Wadman, W. W., III

    1972-01-01

    Particle accelerator radiation measurements are applied to the problem of calculating biological dose from radiation produced in the walls of a spacecraft by various ions in space. Neutrons, one of the products of the interactions of energetic ions with matter, are usually quite penetrating and have large values of Q.F. or R.B.E. Ions of helium, boron, carbon, nitrogen, and oxygen were accelerated and directed onto target materials of copper or tantalum. The secondary neutron production was determined. Studies were made of the angular distribution and an inferred neutron spectrum was calculated from activities of threshold reaction detectors.

  12. Investigations on landmine detection by neutron-based techniques.

    PubMed

    Csikai, J; Dóczi, R; Király, B

    2004-07-01

    Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1m(2)/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13MeV gamma-ray emitted in the (16)O(n,n'gamma) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

  13. Tomography using monochromatic thermal neutrons with attenuation and phase contrast

    NASA Astrophysics Data System (ADS)

    Dubus, Francois; Bonse, Ulrich; Biermann, Theodor; Baron, Matthias; Beckmann, Felix; Zawisky, Michael

    2002-01-01

    Attenuation-contrast tomography with monochromatic thermal neutrons was developed and operated at guide station S18 of the institute Laue-Langevin in Grenoble. From the S18 spectrum the neutron wavelength (lambda) equals 0.18 nm was selected by employing a fore crystal with the silicon 220 reflection at a Bragg angle (Theta) equals 30 degrees. Projections were registered by a position sensitive detector (PSD) consisting of a neutron-to-visible-light converter coupled to a CCD detector. Neutron tomography and its comparison with X-ray tomography is studied. This is of special interest since the cross section for neutron attenuation ((sigma) atom) and the cross section for neutron phase shift (bc) are isotope specific and, in addition, by no means mostly monotonous functions of atomic number Z as are attenuation coefficient ((mu) x) and atomic scattering amplitude (f) in the case of X-rays. Results obtained with n-attenuation tomography will be presented. Possibilities and the setup of an instrument for neutron phase-contrast tomography based on single-crystal neutron interferometry will be described.

  14. DIII-D Neutron Measurement: Status and Plan for Simplification and Upgrade

    NASA Astrophysics Data System (ADS)

    Zhu, Y. B.; Heidbrink, W. W.; Taylor, P. L.; Finkenthal, D.

    2017-10-01

    Neutron diagnostics play key essential roles on DIII-D. Historically an 18-channel 2.45MeV D-D neutron measurement system based on 3He and BF3 proportional counters was inherited from Doublet-III including associated electronics and CAMAC data acquisition. Three fission chambers and two neutron scintillators were added in the 1980s and middle 1990s respectively. For Tritium burn-up studies, two 14MeV D-T neutron measurement systems were installed in 2009 and 2010. Operation and maintenance experience have led to a plan to simplify and upgrade these aging systems to provide a more economical and reliable solution for future DIII-D experiments. On simplification, most conventional expensive NIM and CAMAC modules will be removed. Advanced technologies like ultra-fast data acquisition and software-based pulse identification have been successfully tested. Significant data reduction and efficiency improvement will be achieved by real-time digital pulse identification with a field-programmable gate array. The partly renewed system will consist of 4 neutron counters for absolute calibration and 4 relatively calibrated neutron scintillators covering a wide measurement range. Work supported by US DOE under DE-FC02-04ER54698.

  15. A D-D/D-T fusion reaction based neutron generator system for liver tumor BNCT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Koivunoro, H.; Lou, T.P.; Leung, K. N.

    2003-04-02

    Boron-neutron capture therapy (BNCT) is an experimental radiation treatment modality used for highly malignant tumor treatments. Prior to irradiation with low energetic neutrons, a 10B compound is located selectively in the tumor cells. The effect of the treatment is based on the high LET radiation released in the {sup 10}B(n,{alpha}){sup 7}Li reaction with thermal neutrons. BNCT has been used experimentally for brain tumor and melanoma treatments. Lately applications of other severe tumor type treatments have been introduced. Results have shown that liver tumors can also be treated by BNCT. At Lawrence Berkeley National Laboratory, various compact neutron generators based onmore » D-D or D-T fusion reactions are being developed. The earlier theoretical studies of the D-D or D-T fusion reaction based neutron generators have shown that the optimal moderator and reflector configuration for brain tumor BNCT can be created. In this work, the applicability of 2.5 MeV neutrons for liver tumor BNCT application was studied. The optimal neutron energy for external liver treatments is not known. Neutron beams of different energies (1eV < E < 100 keV) were simulated and the dose distribution in the liver was calculated with the MCNP simulation code. In order to obtain the optimal neutron energy spectrum with the D-D neutrons, various moderator designs were performed using MCNP simulations. In this article the neutron spectrum and the optimized beam shaping assembly for liver tumor treatments is presented.« less

  16. Ames collaborative study of cosmic ray neutrons

    NASA Technical Reports Server (NTRS)

    Hewitt, J. E.; Hughes, L.; Mccaslin, J. B.; Stephens, L. D.; Rindi, A.; Smith, A. R.; Thomas, R. H.; Griffith, R. V.; Welles, C. G.; Baum, J. W.

    1976-01-01

    The results of a collaborative study to define both the neutron flux and the spectrum more precisely and to develop a dosimetry package that can be flown quickly to altitude for solar flare events are described. Instrumentation and analysis techniques were used which were developed to measure accelerator-produced radiation. The instruments were flown in the Ames Research Center high altitude aircraft. Neutron instrumentation consisted of Bonner spheres with both active and passive detector elements, threshold detectors of both prompt-counter and activation-element types, a liquid scintillation spectrometer based on pulse-shape discrimination, and a moderated BF3 counter neutron monitor. In addition, charged particles were measured with a Reuter-Stokes ionization chamber system and dose equivalent with another instrument. Preliminary results from the first series of flights at 12.5 km (41,000 ft) are presented, including estimates of total neutron flux intensity and spectral shape and of the variation of intensity with altitude and geomagnetic latitude.

  17. Prompt Neutron Spectrometry for Identification of SNM in Unknown Shielding Configurations: FY16 ONR YIP Final Report

    DTIC Science & Technology

    2016-05-31

    UMKC-YIP-TR-2016 May 2016 Technical Report Prompt Neutron Spectrometry for Identification of SNM in Unknown Shielding...University of Missouri – Kansas City MSND: Micro-structured Neutron Detector HRM: Handheld Radiation Monitor PHS: Pulse Height Spectrum ANI: Active... Neutron Interrogation Distribution Statement A 6 Administrative Information and Acknowledgements Members of the University of Missouri

  18. Neutron response function characterization of 4He scintillation detectors

    DOE PAGES

    Kelley, Ryan P.; Rolison, Lucas M.; Lewis, Jason M.; ...

    2015-04-15

    Time-of-flight measurements were conducted to characterize the neutron energy response of pressurized 4He fast neutron scintillation detectors for the first time, using the Van de Graaff generator at Ohio University. The time-of-flight spectra and pulse height distributions were measured. This data was used to determine the light output response function, which was found to be linear at energies below 3.5 MeV. The intrinsic efficiency of the detector as a function of incident energy was also calculated: the average efficiency up to 10 MeV was 3.1%, with a maximum efficiency of 6.6% at 1.05 MeV. Furthermore, these results will enable developmentmore » of neutron spectrum unfolding algorithms for neutron spectroscopy applications with these detectors.« less

  19. The correction of vibration in frequency scanning interferometry based absolute distance measurement system for dynamic measurements

    NASA Astrophysics Data System (ADS)

    Lu, Cheng; Liu, Guodong; Liu, Bingguo; Chen, Fengdong; Zhuang, Zhitao; Xu, Xinke; Gan, Yu

    2015-10-01

    Absolute distance measurement systems are of significant interest in the field of metrology, which could improve the manufacturing efficiency and accuracy of large assemblies in fields such as aircraft construction, automotive engineering, and the production of modern windmill blades. Frequency scanning interferometry demonstrates noticeable advantages as an absolute distance measurement system which has a high precision and doesn't depend on a cooperative target. In this paper , the influence of inevitable vibration in the frequency scanning interferometry based absolute distance measurement system is analyzed. The distance spectrum is broadened as the existence of Doppler effect caused by vibration, which will bring in a measurement error more than 103 times bigger than the changes of optical path difference. In order to decrease the influence of vibration, the changes of the optical path difference are monitored by a frequency stabilized laser, which runs parallel to the frequency scanning interferometry. The experiment has verified the effectiveness of this method.

  20. A neutron spectrometer based on temperature variations in superheated drop compositions

    NASA Astrophysics Data System (ADS)

    Apfel, Robert E.; d'Errico, Francesco

    2002-01-01

    The response of superheated drop detectors (SDDs) to neutron radiation varies in a self-consistent manner with variations in temperature and pressure, making such compositions suitable for neutron spectrometry. The advantage of this approach is that the response functions of candidate materials versus energy as the temperature or pressure is varied are nested and have distinct thresholds, with no thermal neutron response. These characteristics permit unfolding without the uncertainties associated with other spectrometry techniques, where multiple solutions are possible, thus requiring an initial guess of the spectrum. A spectrometer was developed based on the well-established technology for acoustic sensing of bubble events interfaced with a proportional-integral-derivative temperature controller. The active monitor for neutrons, called REMbrandt™, was used as the platform for controlling temperature on a SDD probe and for data acquisition, thereby automating the process of measuring the neutron energy spectrum. The new instrument, called REM-SPEC™, implements and automates the original BINS approach: it adjusts the temperature of the SDD vial in increasing steps and measures the bubble event rate at each step. By using two distinct SDD materials with overlapping responses, the 0.1-20 MeV range of energies relevant to practical spectrometry is readily covered. Initial experiments with an Am-Be source validate the operational protocols of this device.

  1. Total Kinetic Energy and Fragment Mass Distribution of Neutron-Induced Fission of U-233

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Higgins, Daniel James; Schmitt, Kyle Thomas; Mosby, Shea Morgan

    Properties of fission in U-233 were studied at the Los Alamos Neutron Science Center (LANSCE) at incident neutron energies from thermal to 40 MeV at both the Lujan Neutron Scattering Center flight path 12 and at WNR flight path 90-Left from Dec 2016 to Jan 2017. Fission fragments are observed in coincidence using a twin ionization chamber with Frisch grids. The average total kinetic energy (TKE) released from fission and fragment mass distributions are calculated from observations of energy deposited in the detector and conservation of mass and momentum. Accurate experimental measurements of these parameters are necessary to better understandmore » the fission process and obtain data necessary for calculating criticality. The average TKE released from fission has been well characterized for several isotopes at thermal neutron energy, however, few measurements have been made at fast neutron energies. This experiment expands on previous successful experiments using an ionization chamber to measure TKE and fragment mass distributions of U-235, U-238, and Pu-239. This experiment requires the full spectrum of neutron energies and can therefore only be performed at a small number of facilities in the world. The required full neutron energy spectrum is obtained by combining measurements from WNR 90L and Lujan FP12 at LANSCE.« less

  2. Characterization of the graphite pile as a source of thermal neutrons

    NASA Astrophysics Data System (ADS)

    Vykydal, Zdenek; Králík, Miloslav; Jančář, Aleš; Kopecký, Zdeněk; Dressler, Jan; Veškrna, Martin

    2015-11-01

    A new graphite pile designed to serve as a standard source of thermal neutrons has been built at the Czech Metrology Institute. Actual dimensions of the pile are 1.95 m (W)×1.95 m (L)×2.0 m (H). At its center, there is a measurement channel whose dimensions are 0.4 m×0.4 m×1.25 m (depth). The channel is equipped with a calibration bench, which allows reproducible placement of the tested/calibrated device. At a distance of 80 cm from the channel axis, six holes are symmetrically located allowing the placement of radionuclide neutron sources of Pu-Be and/or Am-Be type. Spatial distribution of thermal neutron fluence in the cavity was calculated in detail with the MCNP neutron transport code. Experimentally, it was measured with two active detectors: a small 3He proportional detector by the French company LMT, type 0.5 NH 1/1 KF, and a silicon pixel detector Timepix with 10B converter foil. The relative values of thermal neutron fluence rate obtained with active detectors were converted to absolute ones using thermal neutron fluence rates measured by means of gold foil activation. The quality of thermal neutron field was characterized by the cadmium ratio.

  3. A study on the optimum fast neutron flux for boron neutron capture therapy of deep-seated tumors.

    PubMed

    Rasouli, Fatemeh S; Masoudi, S Farhad

    2015-02-01

    High-energy neutrons, named fast neutrons which have a number of undesirable biological effects on tissue, are a challenging problem in beam designing for Boron Neutron Capture Therapy, BNCT. In spite of this fact, there is not a widely accepted criterion to guide the beam designer to determine the appropriate contribution of fast neutrons in the spectrum. Although a number of researchers have proposed a target value for the ratio of fast neutron flux to epithermal neutron flux, it can be shown that this criterion may not provide the optimum treatment condition. This simulation study deals with the determination of the optimum contribution of fast neutron flux in the beam for BNCT of deep-seated tumors. Since the dose due to these high-energy neutrons damages shallow tissues, delivered dose to skin is considered as a measure for determining the acceptability of the designed beam. To serve this purpose, various beam shaping assemblies that result in different contribution of fast neutron flux are designed. The performances of the neutron beams corresponding to such configurations are assessed in a simulated head phantom. It is shown that the previously used criterion, which suggests a limit value for the contribution of fast neutrons in beam, does not necessarily provide the optimum condition. Accordingly, it is important to specify other complementary limits considering the energy of fast neutrons. By analyzing various neutron spectra, two limits on fast neutron flux are proposed and their validity is investigated. The results show that considering these limits together with the widely accepted IAEA criteria makes it possible to have a more realistic assessment of sufficiency of the designed beam. Satisfying these criteria not only leads to reduction of delivered dose to skin, but also increases the advantage depth in tissue and delivered dose to tumor during the treatment time. The Monte Carlo Code, MCNP-X, is used to perform these simulations. Copyright © 2014

  4. Generation of 1/f noise from a broken-symmetry model for the arbitrary absolute pitch of musical melodies.

    PubMed

    Grant, Martin; Faghihi, Niloufar

    2017-11-01

    A model is presented to generate power spectrum noise with intensity proportional to 1/f  as a function of frequency f. The model arises from a broken-symmetry variable, which corresponds to absolute pitch, where fluctuations occur in an attempt to restore that symmetry, influenced by interactions in the creation of musical melodies.

  5. Indoor Fast Neutron Generator for Biophysical and Electronic Applications

    NASA Astrophysics Data System (ADS)

    Cannuli, A.; Caccamo, M. T.; Marchese, N.; Tomarchio, E. A.; Pace, C.; Magazù, S.

    2018-05-01

    This study focuses the attention on an indoor fast neutron generator for biophysical and electronic applications. More specifically, the findings obtained by several simulations with the MCNP Monte Carlo code, necessary for the realization of a shield for indoor measurements, are presented. Furthermore, an evaluation of the neutron spectrum modification caused by the shielding is reported. Fast neutron generators are a valid and interesting available source of neutrons, increasingly employed in a wide range of research fields, such as science and engineering. The employed portable pulsed neutron source is a MP320 Thermo Scientific neutron generator, able to generate 2.5 MeV neutrons with a neutron yield of 2.0 x 106 n/s, a pulse rate of 250 Hz to 20 KHz and a duty factor varying from 5% to 100%. The neutron generator, based on Deuterium-Deuterium nuclear fusion reactions, is employed in conjunction with a solid-state photon detector, made of n-type high-purity germanium (PINS-GMX by ORTEC) and it is mainly addressed to biophysical and electronic studies. The present study showed a proposal for the realization of a shield necessary for indoor applications for MP320 neutron generator, with a particular analysis of the transport of neutrons simulated with Monte Carlo code and described the two main lines of research in which the source will be used.

  6. Absolute Bunch Length Measurements at the ALS by Incoherent Synchrotron Radiation Fluctuation Analysis

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Filippetto, D.; /Frascati; Sannibale, F.

    2008-01-24

    By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.

  7. SPEAR — ToF neutron reflectometer at the Los Alamos Neutron Science Center

    NASA Astrophysics Data System (ADS)

    Dubey, M.; Jablin, M. S.; Wang, P.; Mocko, M.; Majewski, J.

    2011-11-01

    This article discusses the Surface ProfilE Analysis Reflectometer (SPEAR), a vertical scattering geometry time-of-flight reflectometer, at the Los Alamos National Laboratory Lujan Neutron Scattering Center. SPEAR occupies flight path 9 and receives spallation neutrons from a polychromatic, pulsed (20Hz) source that pass through a liquid-hydrogen moderator at 20K coupled with a Be filter to shift their energy spectrum. The spallation neutrons are generated by bombarding a tungsten target with 800MeV protons obtained from an accelerator. The process produces an integrated neutron flux of ˜ 3.4×106 cm-2 s-1 at a proton current of 100 μA. SPEAR employs choppers and frame overlap mirrors to obtain a neutron wavelength range of 4.5-16 Å. SPEAR uses a single 200mm long 3He linear position-sensitive detector with ˜ 2 mm FWHM resolution for simultaneous studies of both specular and off-specular scattering. SPEAR's moderated neutrons are collimated into a beam which impinges from above upon a level sample with an average angle of 0.9° to the horizontal, to facilitate air-liquid interface studies. In the vertical direction, the beam converges at the sample position. The neutrons can be further collimated to the desired divergence by finely slitting the beam using a set of two 10B4C slit packages. The instrument is ideally suited to study organic and inorganic thin films with total thicknesses between 5 and 3000 Å in a variety of environments. Specifically designed sample chambers available at the instrument provide the opportunity to study biological systems at the solid-liquid interface. SPEAR's unique experimental capabilities are demonstrated by specific examples in this article. Finally, an outlook for SPEAR and perspectives on future instrumentation are discussed.

  8. 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.

  9. Elastic and Inelastic Scattering of Neutrons using a CLYC array

    NASA Astrophysics Data System (ADS)

    Brown, Tristan; Doucet, E.; Chowdhury, P.; Lister, C. J.; Wilson, G. L.; Devlin, M.; Mosby, S.

    2015-10-01

    CLYC scintillators, which have dual neutron and gamma response, have recently ushered in the possibility of fast neutron spectroscopy without time-of-flight (TOF). A 16-element array of 1'' x 1'' 6Li-depleted CLYC crystals, where pulse-shape-discrimination is achieved via digital pulse processing, has been commissioned at UMass Lowell. In an experiment at LANSCE, high energy neutrons were used to bombard 56Fe and 238U targets, in order to measure elastic and inelastic neutron scattering cross sections as a function of energy and angle with the array. The array is placed very close to the targets for enhanced geometrical solid angles for scattered neutrons compared to standard neutron-TOF measurements. A pulse-height spectrum of scattered neutrons in the detectors is compared to the energy of the incident neutrons, which is measured via the TOF of the pulsed neutrons from the source to the detectors. Recoil corrections are necessary to combine the energy spectra from all the detectors to obtain angle-integrated elastic and inelastic cross-sections. The detection techniques, analysis procedures and results will be presented. Supported by NNSA-SSAA program through DOE Grant DE-NA00013008.

  10. Sensitivity Analysis of Cf-252 (sf) Neutron and Gamma Observables in CGMF

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Carter, Austin Lewis; Talou, Patrick; Stetcu, Ionel

    CGMF is a Monte Carlo code that simulates the decay of primary fission fragments by emission of neutrons and gamma rays, according to the Hauser-Feshbach equations. As the CGMF code was recently integrated into the MCNP6.2 transport code, great emphasis has been placed on providing optimal parameters to CGMF such that many different observables are accurately represented. Of these observables, the prompt neutron spectrum, prompt neutron multiplicity, prompt gamma spectrum, and prompt gamma multiplicity are crucial for accurate transport simulations of criticality and nonproliferation applications. This contribution to the ongoing efforts to improve CGMF presents a study of the sensitivitymore » of various neutron and gamma observables to several input parameters for Californium-252 spontaneous fission. Among the most influential parameters are those that affect the input yield distributions in fragment mass and total kinetic energy (TKE). A new scheme for representing Y(A,TKE) was implemented in CGMF using three fission modes, S1, S2 and SL. The sensitivity profiles were calculated for 17 total parameters, which show that the neutron multiplicity distribution is strongly affected by the TKE distribution of the fragments. The total excitation energy (TXE) of the fragments is shared according to a parameter RT, which is defined as the ratio of the light to heavy initial temperatures. The sensitivity profile of the neutron multiplicity shows a second order effect of RT on the mean neutron multiplicity. A final sensitivity profile was produced for the parameter alpha, which affects the spin of the fragments. Higher values of alpha lead to higher fragment spins, which inhibit the emission of neutrons. Understanding the sensitivity of the prompt neutron and gamma observables to the many CGMF input parameters provides a platform for the optimization of these parameters.« less

  11. Thermal neutron capture and resonance integral cross sections of 45Sc

    NASA Astrophysics Data System (ADS)

    Van Do, Nguyen; Duc Khue, Pham; Tien Thanh, Kim; Thi Hien, Nguyen; Kim, Guinyun; Kim, Kwangsoo; Shin, Sung-Gyun; Cho, Moo-Hyun; Lee, Manwoo

    2015-11-01

    The thermal neutron cross section (σ0) and resonance integral (I0) of the 45Sc(n,γ)46Sc reaction have been measured relative to that of the 197Au(n,γ)198Au reaction by means of the activation method. High-purity natural scandium and gold foils without and with a cadmium cover of 0.5 mm thickness were irradiated with moderated pulsed neutrons produced from the Pohang Neutron Facility (PNF). The induced activities in the activated foils were measured with a high purity germanium (HPGe) detector. In order to improve the accuracy of the experimental results the counting losses caused by the thermal (Gth) and resonance (Gepi) neutron self-shielding, the γ-ray attenuation (Fg) and the true γ-ray coincidence summing effects were made. In addition, the effect of non-ideal epithermal spectrum was also taken into account by determining the neutron spectrum shape factor (α). The thermal neutron cross-section and resonance integral of the 45Sc(n,γ)46Sc reaction have been determined relative to the reference values of the 197Au(n,γ)198Au reaction, with σo,Au = 98.65 ± 0.09 barn and Io,Au = 1550 ± 28 barn. The present thermal neutron cross section has been determined to be σo,Sc = 27.5 ± 0.8 barn. According to the definition of cadmium cut-off energy at 0.55 eV, the present resonance integral cross section has been determined to be Io,Sc = 12.4 ± 0.7 barn. The present results are compared with literature values and discussed.

  12. Determining the 13C(α, n)16O absolute cross section through the concurrent application of ANC and THM and astrophysical consequences for the s-process in AGB-LMSs.

    NASA Astrophysics Data System (ADS)

    Trippella, Oscar; La Cognata, Marco

    2018-01-01

    The 13C(α, n)16O reaction is considered to be the most important neutron source for the s-process main component in low-mass asymptotic giant branch stars. No direct experimental data exist at very low energies and measurements performed through direct techniques show inconsistent results, mostly in their absolute values. In this context, we reversed the usual normalization procedure combining two indirect approaches, the asymptotic normalization coefficient and the Trojan Horse Method, to unambiguously determine the absolute value of the 13C(α, n)16O astrophysical S(E)-factor in the most relevant energy-region for astrophysics. Adopting the new reaction rate for the n-source in the NEWTON s-process nucleosynthesis code, astrophysical calculations show only limited variations, less than 1%, for those nuclei whose production is considered to be totally due to slow neutron captures.

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

    DOE PAGES

    Hatarik, R.; Sayre, D. B.; Caggiano, J. A.; ...

    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 (T ion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent T ion and DSR.

  14. Neutron Reference Benchmark Field Specifications: ACRR Polyethylene-Lead-Graphite (PLG) Bucket Environment (ACRR-PLG-CC-32-CL).

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Vega, Richard Manuel; Parm, Edward J.; Griffin, Patrick J.

    2015-07-01

    This report was put together to support the International Atomic Energy Agency (IAEA) REAL- 2016 activity to validate the dosimetry community’s ability to use a consistent set of activation data and to derive consistent spectral characterizations. The report captures details of integral measurements taken in the Annular Core Research Reactor (ACRR) central cavity with the Polyethylene-Lead-Graphite (PLG) bucket, reference neutron benchmark field. The field is described and an “a priori” calculated neutron spectrum is reported, based on MCNP6 calculations, and a subject matter expert (SME) based covariance matrix is given for this “a priori” spectrum. The results of 37 integralmore » dosimetry measurements in the neutron field are reported.« less

  15. Measurement and calculation of fast neutron and gamma spectra in well defined cores in LR-0 reactor.

    PubMed

    Košťál, Michal; Matěj, Zdeněk; Cvachovec, František; Rypar, Vojtěch; Losa, Evžen; Rejchrt, Jiří; Mravec, Filip; Veškrna, Martin

    2017-02-01

    A well-defined neutron spectrum is essential for many types of experimental topics and is also important for both calibration and testing of spectrometric and dosimetric detectors. Provided it is well described, such a spectrum can also be employed as a reference neutron field that is suitable for validating selected cross sections. The present paper aims to compare calculations and measurements of such a well-defined spectra in geometrically similar cores of the LR-0 reactor with fuel containing slightly different enrichments (2%, 3.3% and 3.6%). The common feature to all cores is a centrally located dry channel which can be used for the insertion of studied materials. The calculation of neutron and gamma spectra was realized with the MCNP6 code using ENDF/B-VII.0, JEFF-3.1, JENDL-3.3, ROSFOND-2010 and CENDL-3.1 nuclear data libraries. Only minor differences in neutron and gamma spectra were found in the comparison of the presented reactor cores with different fuel enrichments. One exception is the gamma spectrum in the higher energy region (above 8MeV), where more pronounced variations could be observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Implications of an Absolute Simultaneity Theory for Cosmology and Universe Acceleration

    PubMed Central

    Kipreos, Edward T.

    2014-01-01

    An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centered non-rotating inertial reference frame, with the inference that in an ALT framework, preferred reference frames are associated with centers of gravitational mass. Applying this theoretical framework to cosmological data produces a scenario of universal time contraction in the past. In this scenario, past time contraction would be associated with increased levels of blueshifted light emissions from cosmological objects when viewed from our current perspective. The observation that distant Type Ia supernovae are dimmer than predicted by linear Hubble expansion currently provides the most direct evidence for an accelerating universe. Adjusting for the effects of time contraction on a redshift–distance modulus diagram produces a linear distribution of supernovae over the full redshift spectrum that is consistent with a non-accelerating universe. PMID:25536116

  17. Implications of an absolute simultaneity theory for cosmology and universe acceleration.

    PubMed

    Kipreos, Edward T

    2014-01-01

    An alternate Lorentz transformation, Absolute Lorentz Transformation (ALT), has similar kinematics to special relativity yet maintains absolute simultaneity in the context of a preferred reference frame. In this study, it is shown that ALT is compatible with current experiments to test Lorentz invariance only if the proposed preferred reference frame is locally equivalent to the Earth-centered non-rotating inertial reference frame, with the inference that in an ALT framework, preferred reference frames are associated with centers of gravitational mass. Applying this theoretical framework to cosmological data produces a scenario of universal time contraction in the past. In this scenario, past time contraction would be associated with increased levels of blueshifted light emissions from cosmological objects when viewed from our current perspective. The observation that distant Type Ia supernovae are dimmer than predicted by linear Hubble expansion currently provides the most direct evidence for an accelerating universe. Adjusting for the effects of time contraction on a redshift-distance modulus diagram produces a linear distribution of supernovae over the full redshift spectrum that is consistent with a non-accelerating universe.

  18. Determining the Magnitude of Neutron and Galactic Cosmic Ray (GCR) Fluxes at the Moon using the Lunar Exploration Neutron Detector during the Historic Space-Age Era of High GCR Flux

    NASA Astrophysics Data System (ADS)

    Chin, G.; Sagdeev, R.; Boynton, W. V.; Mitrofanov, I. G.; Milikh, G. M.; Su, J. J.; Livengood, T. A.; McClanahan, T. P.; Evans, L.; Starr, R. D.; litvak, M. L.; Sanin, A.

    2013-12-01

    The Lunar Reconnaissance Orbiter (LRO) was launched June 18, 2009 during an historic space-age era of minimum solar activity [1]. The lack of solar sunspot activity signaled a complex set of heliospheric phenomena [2,3,4] that also gave rise to a period of unprecedentedly high Galactic Cosmic Ray (GCR) flux [5]. These events coincided with the primary mission of the Lunar Exploration Neutron Detector (LEND, [6]), onboard LRO in a nominal 50-km circular orbit of the Moon [7]. Methods to calculate the emergent neutron albedo population using Monte Carlo techniques [8] rely on an estimate of the GCR flux and spectra calibrated at differing periods of solar activity [9,10,11]. Estimating the actual GCR flux at the Moon during the LEND's initial period of operation requires a correction using a model-dependent heliospheric transport modulation parameter [12] to adjust the GCR flux appropriate to this unique solar cycle. These corrections have inherent uncertainties depending on model details [13]. Precisely determining the absolute neutron and GCR fluxes is especially important in understanding the emergent lunar neutrons measured by LEND and subsequently in estimating the hydrogen/water content in the lunar regolith [6]. LEND is constructed with a set of neutron detectors to meet differing purposes [6]. Specifically there are two sets of detector systems that measure the flux of epithermal neutrons: a) the uncollimated Sensor for Epi-Thermal Neutrons (SETN) and b) the Collimated Sensor for Epi-Thermal Neutrons (CSETN). LEND SETN and CSETN observations form a complementary set of simultaneous measurements that determine the absolute scale of emergent lunar neutron flux in an unambiguous fashion and without the need for correcting to differing solar-cycle conditions. LEND measurements are combined with a detailed understanding of the sources of instrumental back-ground, and the performance of CSETN and SETN. This comparison allows us to calculate a constant scale factor

  19. Neutron-multiplicity experiments for enhanced fission modelling

    NASA Astrophysics Data System (ADS)

    Al-Adili, Ali; Tarrío, Diego; Hambsch, Franz-Josef; Göök, Alf; Jansson, Kaj; Solders, Andreas; Rakapoulos, Vasileios; Gustavsson, Cecilia; Lantz, Mattias; Mattera, Andrea; Oberstedt, Stephan; Prokofiev, Alexander V.; Sundén, Erik A.; Vidali, Marzio; Österlund, Michael; Pomp, Stephan

    2017-09-01

    The nuclear de-excitation process of fission fragments (FF) provides fundamental information for the understanding of nuclear fission and nuclear structure in neutron-rich isotopes. The variation of the prompt-neutron multiplicity, ν(A), as a function of the incident neutron energy (En) is one of many open questions. It leads to significantly different treatments in various fission models and implies that experimental data are analyzed based on contradicting assumptions. One critical question is whether the additional excitation energy (Eexc) is manifested through an increase of ν(A) for all fragments or for the heavy ones only. A systematic investigation of ν(A) as a function of En has been initiated. Correlations between prompt-fission neutrons and fission fragments are obtained by using liquid scintillators in conjunction with a Frisch-grid ionization chamber. The proof-of-principle has been achieved on the reaction 235U(nth,f) at the Van De Graff (VdG) accelerator of the JRC-Geel using a fully digital data acquisition system. Neutrons from 252Cf(sf) were measured separately to quantify the neutron-scattering component due to surrounding shielding material and to determine the intrinsic detector efficiency. Prelimenary results on ν(A) and spectrum in correlation with FF properties are presented.

  20. SONTRAC: A High Efficiency Solar Neutron Telescope

    NASA Astrophysics Data System (ADS)

    Wunderer, C. B.; Macri, J.; McConnell, M. L.; Ryan, J. M.; Baltgalvis, J.; Holslin, D.; Polichar, A.; Jenkins, T.

    1997-05-01

    Solar flare neutron emission between 20 and 100 MeV comes from a portion of the energetic proton spectrum that is poorly sampled by both nuclear-line and pion- decay gamma rays. SONTRAC is a new generation solar neutron telescope/spectrometer consisting of densely packed, alternating orthogonal layers of scintillating plastic fibers. The fibers in both dimensions are viewed by image intensifiers and CCD cameras. Incident neutrons scatter off hydrogen in the plastic scintillator. The resulting ionizing proton tracks can be reconstructed in three dimensions using the two planar CCD track images. Two neutron-proton scatters provide sufficient information to reconstruct the energy and direction of the incident neutron. Photomultiplier tubes view the other sides of the fiber scintillator array. The signals from the PMTs are used to give an additional measure of the proton energies and to provide a trigger for the CCD cameras. Recent technological advances have allowed us to construct an affordable working prototype instrument that consists of all the essential technical elements mentioned above. We will present images of tracks produced by minimum ionizing muons and energetic neutrons. We will also present efficiency estimates for SONTRAC's ability to detect and measure gamma rays above 10 MeV.

  1. Use of an untuned cavity for absolute power measurements of the harmonics above 100 GHz from an IMPATT oscillator

    NASA Astrophysics Data System (ADS)

    Llewellyn-Jones, D. T.; Knight, R. J.; Gebbie, H. A.

    1980-07-01

    A new technique of measuring absolute power exploiting an untuned cavity and Fourier spectroscopy has been used to examine the power spectrum of the harmonics and other overtones produced by a 95 GHz IMPATT oscillator. The conditions which favor the production of a rich harmonic spectrum are not those which maximize the fundamental power. Under some conditions of mismatch at the fundamental frequency it is possible to produce over 200 microW of harmonic power in the 100-200 GHz region comparable with the fundamental power from the oscillator.

  2. Reaction-in-Flight neutrons as a test of stopping power in degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Hayes, A. C.; Cerjan, C. J.; Jungman, G.; Fowler, M. M.; Gooden, M. E.; Grim, G. P.; Henry, E.; Rundberg, R. S.; Sepke, S. M.; Schneider, D. H. G.; Singleton, R. L.; Tonchev, A. P.; Wilhelmy, J. B.; Yeamans, C. B.

    2016-05-01

    Cryogenically cooled inertial confinement fusion capsule designs are suitable for studies of reaction-in-flight (RIF) neutrons. RIF neutrons occur when energetically up-scattered ions undergo DT reactions with a thermal ion in the plasma, producing neutrons in the energy range 9-30 MeV. The knock-on ions lose energy as they traverse the plasma, which directly affects the spectrum of the produced RIF neutrons. Here we present measurements from the National Ignition Facility (NIF) of RIF neutrons produced in cryogenic capsules, with energies above 15 MeV. We show that the measured RIFs probe stopping under previously unexplored degenerate plasma conditions and constrain stopping models in warm dense plasma conditions.

  3. Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT.

    PubMed

    Adib, M; Habib, N; Bashter, I I; El-Mesiry, M S; Mansy, M S

    2016-01-01

    Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5-7.5 keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named "QMNB-AS" was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Ionization signals from diamond detectors in fast-neutron fields

    NASA Astrophysics Data System (ADS)

    Weiss, C.; Frais-Kölbl, H.; Griesmayer, E.; Kavrigin, P.

    2016-09-01

    In this paper we introduce a novel analysis technique for measurements with single-crystal chemical vapor deposition (sCVD) diamond detectors in fast-neutron fields. This method exploits the unique electronic property of sCVD diamond sensors that the signal shape of the detector current is directly proportional to the initial ionization profile. In fast-neutron fields the diamond sensor acts simultaneously as target and sensor. The interaction of neutrons with the stable isotopes 12 C and 13 C is of interest for fast-neutron diagnostics. The measured signal shapes of detector current pulses are used to identify individual types of interactions in the diamond with the goal to select neutron-induced reactions in the diamond and to suppress neutron-induced background reactions as well as γ-background. The method is verified with experimental data from a measurement in a 14.3 MeV neutron beam at JRC-IRMM, Geel/Belgium, where the 13C(n, α)10Be reaction was successfully extracted from the dominating background of recoil protons and γ-rays and the energy resolution of the 12C(n, α)9Be reaction was substantially improved. The presented analysis technique is especially relevant for diagnostics in harsh radiation environments, like fission and fusion reactors. It allows to extract the neutron spectrum from the background, and is particularly applicable to neutron flux monitoring and neutron spectroscopy.

  5. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

    DOE PAGES

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea; ...

    2016-10-17

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  6. Neutron imaging with the short-pulse laser driven neutron source at the TRIDENT Laser Facility

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Guler, Nevzat; Volegov, Petr Lvovich; Favalli, Andrea

    Emerging approaches to short-pulse laser-driven neutron production offer a possible gateway to compact, low cost, and intense broad spectrum sources for a wide variety of applications. They are based on energetic ions, driven by an intense short-pulse laser, interacting with a converter material to produce neutrons via breakup and nuclear reactions. Recent experiments performed with the high-contrast laser at the Trident laser facility of Los Alamos National Laboratory have demonstrated a laser-driven ion acceleration mechanism operating in the regime of relativistic transparency, featuring a volumetric laser-plasma interaction. This mechanism is distinct from previously studied ones that accelerate ions at themore » laser-target surface. The Trident experiments produced an intense beam of deuterons with an energy distribution extending above 100 MeV. This deuteron beam, when directed at a beryllium converter, produces a forward-directed neutron beam with ~5x10 9 n/sr, in a single laser shot, primarily due to deuteron breakup. The neutron beam has a pulse duration on the order of a few nanoseconds with an energy distribution extending from a few hundreds of keV to almost 80 MeV. For the experiments on neutron-source spot-size measurements, our gated neutron imager was setup to select neutrons in the energy range of 2.5 to 35 MeV. The spot size of neutron emission at the converter was measured by two different imaging techniques, using a knife-edge and a penumbral aperture, in two different experimental campaigns. The neutron-source spot size is measured ~1 mm for both experiments. The measurements and analysis reported here give a spatial characterization for this type of neutron source for the first time. In addition, the forward modeling performed provides an empirical estimate of the spatial characteristics of the deuteron ion-beam. Finally, these experimental observations, taken together, provide essential yet unique data to benchmark and verify theoretical

  7. Measuring the activity of a {sup 51}Cr neutrino source based on the gamma-radiation spectrum

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gorbachev, V. V., E-mail: vvgor-gfb1@mail.ru; Gavrin, V. N.; Ibragimova, T. V.

    A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of {sup 51}Cr is presented.

  8. Neutron Imaging at LANSCE—From Cold to Ultrafast

    DOE PAGES

    Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.; ...

    2018-02-23

    In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

  9. Neutron Imaging at LANSCE—From Cold to Ultrafast

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.

    In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

  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. Carbon Atmosphere Discovered On Neutron Star

    NASA Astrophysics Data System (ADS)

    2009-11-01

    Evidence for a thin veil of carbon has been found on the neutron star in the Cassiopeia A supernova remnant. This discovery, made with NASA's Chandra X-ray Observatory, resolves a ten-year mystery surrounding this object. "The compact star at the center of this famous supernova remnant has been an enigma since its discovery," said Wynn Ho of the University of Southampton and lead author of a paper that appears in the latest issue of Nature. "Now we finally understand that it can be produced by a hot neutron star with a carbon atmosphere." By analyzing Chandra's X-ray spectrum - akin to a fingerprint of energy - and applying it to theoretical models, Ho and his colleague Craig Heinke, from the University of Alberta, determined that the neutron star in Cassiopeia A, or Cas A for short, has an ultra-thin coating of carbon. This is the first time the composition of an atmosphere of an isolated neutron star has been confirmed. The Chandra "First Light" image of Cas A in 1999 revealed a previously undetected point-like source of X-rays at the center. This object was presumed to be a neutron star, the typical remnant of an exploded star, but researchers were unable to understand its properties. Defying astronomers' expectations, this object did not show any X-ray or radio pulsations or any signs of radio pulsar activity. By applying a model of a neutron star with a carbon atmosphere to this object, Ho and Heinke found that the region emitting X-rays would uniformly cover a typical neutron star. This would explain the lack of X-ray pulsations because -- like a lightbulb that shines consistently in all directions -- this neutron star would be unlikely to display any changes in its intensity as it rotates. Scientists previously have used a neutron star model with a hydrogen atmosphere giving a much smaller emission area, corresponding to a hot spot on a typical neutron star, which should produce X-ray pulsations as it rotates. Interpreting the hydrogen atmosphere model

  12. Constraining parameters of the neutron star in the supernova remnant HESS J1731-347

    NASA Astrophysics Data System (ADS)

    Klochkov, D.; Suleimanov, V.; Puehlhofer, G.; Werner, K.; Santangelo, A.

    2014-07-01

    The Central Compact Object (CCO) in HESS J1731-347, presumably a neutron star, is one of the brightest sources in this class. Like other CCOs, it potentially provides an "undisturbed" view of thermal radiation generated at the neutron star surface. The shape and normalization of the corresponding X-ray spectrum depends on the emitting area, surface redshift, and gravity acceleration. Thus, its modeling under certain assumptions allows the mass and radius of the neutron star to be constrained. In our analysis, we model the spectrum of the CCO accumulated with XMM-Newton over ˜100 ksec exposure time in three observations. The exposure time has increased by a factor of five since our previous analysis of the source. For the spectral fitting, we use our hydrogen and carbon atmosphere models calculated assuming hydrostatic and radiative equilibria and taking into account pressure ionization and the presence of spectral lines (in case of carbon). We present the resulting constraints on the mass, radius, distance, and temperature of the neutron star.

  13. Using a fast-neutron spectrometer system to candle luggage for hidden explosives

    NASA Astrophysics Data System (ADS)

    Lefevre, Harlan W.; Rasmussen, R. J.; Chmelik, Michael S.; Schofield, R. M. S.; Sieger, G. E.; Overley, Jack C.

    1997-02-01

    A continuous spectrum of neutron switch energies up to 8.2 MeV is produced by a 4.2-MeV nanosecond-pulsed deuteron beam slowing down in a thick beryllium target. The spectrum form the locally shielded target is collimated to a horizontal fan-beam and delivered to a row of 16, 6-cm square plastic scintillators located 4 m from the neutron source. The scintillators are coupled to 12-stage photomultiplier tubes, constant-fraction discriminators, time-to-amplitude converters, analog-to-digital converters, and digital memories. Unattenuated neutron-source spectra and background spectra ar recorded. Luggage is stepped through the fan beam by an automated lift located 2 m from the neutron source. Transmission spectra are measured, and are transferred to a computer while the location is advanced one pixel width. As the next set of spectra is being measured, the computer calculates neutron attenuations for the previous set, deconvolutes attenuations into projected elemental number densities, and determines the explosive likelihood for each pixel. With a time-averaged deuteron beam current o 1(mu) A, a suitcase 60-cm long can be automatically imaged in 1600s. We will suggest that time can be reduced to 8s or less with straight-forward improvements. The following paper describes the explosives recognition algorithm and presents the results of teste with explosives.

  14. Absolute measurements of the electronic transition moments of seven band systems of the C2 molecule. Ph.D. Thesis - York Univ., Toronto

    NASA Technical Reports Server (NTRS)

    Cooper, D. M.

    1979-01-01

    Electronic transition moments of seven C2 singlet and triplet band systems in the 0.2-1.2 micron spectral region were measured. The measurements were made in emission behind incident shock waves in C2H2-argon mixtures. Narrow bandpass radiometers were used to obtain absolute measurements of shock-excited C2 radiation from which absolute electronic transition moments are derived by a synthetic spectrum analysis. New results are reported for the Ballik-Ramsay, Phillips, Swan, Deslandres-d'Azambuja, Fox-Herzberg, Mulliken, and Freymark systems.

  15. Measurement of 241Am-Be spectra (bare and Pb-covered) using TLD pairs in multi-spheres: Spectrum unfolding by different methods

    NASA Astrophysics Data System (ADS)

    Tripathy, S. P.; Bakshi, A. K.; Sathian, V.; Tripathi, S. M.; Vega-carrillo, H. R.; Nandy, M.; Sarkar, P. K.; Sharma, D. N.

    2009-01-01

    The neutron spectra from a Pb-covered and a bare (without Pb-cover) 241Am-Be (α,n) source were measured using thermoluminescent detector (TLD) pairs of 6LiF and 7LiF with high-density polyethylene (HDPE) multi-spheres of seven different diameters. A total of 8 distinct neutron response signals (including a bare mode exposure) were obtained from which the energy distribution for the entire energy range was generated with the help of different neutron spectrum unfolding methods, viz. BUNKI, BUNKIUT and Frascati unfolding interactive tool (FRUIT). Shape of these spectra are matching very well and is also comparable with the standard IAEA 241Am-Be spectrum, thus, validating the unfolding methods used in this work. The effect of Pb-cover on the spectrum and the unfolding details are reported in the paper.

  16. FRUIT: An operational tool for multisphere neutron spectrometry in workplaces

    NASA Astrophysics Data System (ADS)

    Bedogni, Roberto; Domingo, Carles; Esposito, Adolfo; Fernández, Francisco

    2007-10-01

    FRUIT (Frascati Unfolding Interactive Tool) is an unfolding code for Bonner sphere spectrometers (BSS) developed, under the Labview environment, at the INFN-Frascati National Laboratory. It models a generic neutron spectrum as the superposition of up to four components (thermal, epithermal, fast and high energy), fully defined by up to seven positive parameters. Different physical models are available to unfold the sphere counts, covering the majority of the neutron spectra encountered in workplaces. The iterative algorithm uses Monte Carlo methods to vary the parameters and derive the final spectrum as limit of a succession of spectra fulfilling the established convergence criteria. Uncertainties on the final results are evaluated taking into consideration the different sources of uncertainty affecting the input data. Relevant features of FRUIT are (1) a high level of interactivity, allowing the user to follow the convergence process, (2) the possibility to modify the convergence tolerances during the run, allowing a rapid achievement of meaningful solutions and (3) the reduced dependence of the results from the initial hypothesis. This provides a useful instrument for spectrometric measurements in workplaces, where detailed a priori information is usually unavailable. This paper describes the characteristics of the code and presents the results of performance tests over a significant variety of reference and workplace neutron spectra ranging from thermal up to hundreds MeV neutrons.

  17. Frequency spectrum of tantalum at temperatures of 293-2300 K

    NASA Astrophysics Data System (ADS)

    Semenov, V. A.; Kozlov, Zh. A.; Krachun, L.; Mateescu, G.; Morozov, V. M.; Oprea, A. I.; Oprea, K.; Puchkov, A. V.

    2010-05-01

    The temperature dependence of the frequency spectrum of tantalum in the temperature range from room temperature to 2300 K has been studied for the first time using inelastic slow-neutron scattering. The inelastic slow-neutron scattering spectra have been measured at different temperatures on a DIN-2PI time-of-flight spectrometer installed at the IBR-2 nuclear reactor (Joint Institute for Nuclear Research, Dubna, Russia) with the use of a TS3000K high-temperature thermostat. From the measured spectra, the frequency spectra of the tantalum crystal lattice have been determined at temperatures of 293, 1584, and 2300 K by the iteration method. As the temperature increases, the frequency spectrum, on the whole, is softened and the specific features manifested themselves at room temperature are smoothed. The variations observed have been explained by the increase in the role of the effects of vibration anharmonism at high temperatures.

  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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dickens, J.K.; Hill, N.W.; Hou, F.S.

    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 themore » 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.« less

  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

    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.

  20. Spectroscopic neutron detection using composite scintillators

    NASA Astrophysics Data System (ADS)

    Jovanovic, I.; Foster, A.; Kukharev, V.; Mayer, M.; Meddeb, A.; Nattress, J.; Ounaies, Z.; Trivelpiece, C.

    2016-09-01

    Shielded special nuclear material (SNM), especially highly enriched uranium, is exceptionally difficult to detect without the use of active interrogation (AI). We are investigating the potential use of low-dose active interrogation to realize simultaneous high-contrast imaging and photofission of SNM using energetic gamma-rays produced by low-energy nuclear reactions, such as 11B(d,nγ)12C and 12C(p,p‧)12C. Neutrons produced via fission are one reliable signature of the presence of SNM and are usually identified by their unique timing characteristics, such as the delayed neutron die-away. Fast neutron spectroscopy may provide additional useful discriminating characteristics for SNM detection. Spectroscopic measurements can be conducted by recoil-based or thermalization and capture-gated detectors; the latter may offer unique advantages since they facilitate low-statistics and event-by-event neutron energy measurements without spectrum unfolding. We describe the results of the development and characterization of a new type of capture-gated spectroscopic neutron detector based on a composite of scintillating polyvinyltoluene and lithium-doped scintillating glass in the form of millimeter-thick rods. The detector achieves >108 neutron-gamma discrimination resulting from its geometric properties and material selection. The design facilitates simultaneous pulse shape and pulse height discrimination, despite the fact that no materials intrinsically capable of pulse shape discrimination have been used to construct the detector. Accurate single-event measurements of neutron energy may be possible even when the energy is relatively low, such as with delayed fission neutrons. Simulation and preliminary measurements using the new composite detector are described, including those conducted using radioisotope sources and the low-dose active interrogation system based on low-energy nuclear reactions.

  1. The Berkeley Instrumental Neutron Generator (BINGE) for 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Renne, P. R.; Becker, T. A.; Bernstein, L.; Firestone, R. B.; Kirsch, L.; Leung, K. N.; Rogers, A.; Van Bibber, K.; Waltz, C.

    2014-12-01

    The Berkeley Instrumental Neutron Generator (BINGE) facility is the product of a consortium involving the Berkeley Geochronology Center (BGC), the U.C. Berkeley Nuclear Engineering Dept. (UCB/NE), and Lawrence Berkeley (LBNL) and Lawrence Livermore (LLNL) National Labs. BINGE was initially designed (and funded by NSF) for 40Ar/39Ar geochronology. BINGE uses a plasma-based deuteron ion source and a self-loading Ti-surfaced target to induce deuteron-deuterium (DD) fusion via the reaction 2H(d,n)3He, producing 2.45 MeV neutrons. The limited neutron energy spectrum is aimed at reducing recoil effects, interfering nuclear reactions, and unwanted radioactive byproducts, all of which are undesirable consequences of conventional irradiation with 235U fission spectrum neutrons. Minimization of interfering reactions such as 40Ca(n,na)36Ar greatly reduces penalties for over-irradiation, enabling improved signal/background measurement of e.g. 39Ar. BINGE will also be used for a variety of nuclear physics and engineering experiments that require a high flux of monoenergetic neutrons. Neutron energies lower than 2.45 MeV can be obtained via irradiation ports within and external to polyethylene shielding. Initial commissioning produced a neutron flux of 108 n/sec/cm2 at 1 mA source current and 100 kV anode voltage, as expected. When scaled up to the 1 A source current as planned, this indicates that BINGE will achieve the design objective neutron flux of 1011 n/sec/cm2. Further progress towards this goal will be reported. Supported by NSF (grant #EAR-0960138), BGC, UCB/NE, University of California Office of the President, and DOE through LLNL under contract #DE-AC52-07NA27344 and LBNL under contract #DE-AC02-05CH11231.

  2. Accelerator-based epithermal neutron sources for boron neutron capture therapy of brain tumors.

    PubMed

    Blue, Thomas E; Yanch, Jacquelyn C

    2003-01-01

    This paper reviews the development of low-energy light ion accelerator-based neutron sources (ABNSs) for the treatment of brain tumors through an intact scalp and skull using boron neutron capture therapy (BNCT). A major advantage of an ABNS for BNCT over reactor-based neutron sources is the potential for siting within a hospital. Consequently, light-ion accelerators that are injectors to larger machines in high-energy physics facilities are not considered. An ABNS for BNCT is composed of: (1) the accelerator hardware for producing a high current charged particle beam, (2) an appropriate neutron-producing target and target heat removal system (HRS), and (3) a moderator/reflector assembly to render the flux energy spectrum of neutrons produced in the target suitable for patient irradiation. As a consequence of the efforts of researchers throughout the world, progress has been made on the design, manufacture, and testing of these three major components. Although an ABNS facility has not yet been built that has optimally assembled these three components, the feasibility of clinically useful ABNSs has been clearly established. Both electrostatic and radio frequency linear accelerators of reasonable cost (approximately 1.5 M dollars) appear to be capable of producing charged particle beams, with combinations of accelerated particle energy (a few MeV) and beam currents (approximately 10 mA) that are suitable for a hospital-based ABNS for BNCT. The specific accelerator performance requirements depend upon the charged particle reaction by which neutrons are produced in the target and the clinical requirements for neutron field quality and intensity. The accelerator performance requirements are more demanding for beryllium than for lithium as a target. However, beryllium targets are more easily cooled. The accelerator performance requirements are also more demanding for greater neutron field quality and intensity. Target HRSs that are based on submerged-jet impingement and

  3. Corpus Callosum Morphometrics in Young Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Boger-Megiddo, Inbal; Shaw, Dennis W. W.; Friedman, Seth D.; Sparks, Bobbi F.; Artru, Alan A.; Giedd, Jay N.; Dawson, Geraldine; Dager, Stephen R.

    2006-01-01

    This study assessed digital corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD…

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

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ji Chuncheng; Kegel, G.H.R.; Egan, J.J.

    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 fissionmore » 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.« less

  5. Response of LaBr3(Ce) scintillators to 2.5 MeV fusion neutrons.

    PubMed

    Cazzaniga, C; Nocente, M; Tardocchi, M; Croci, G; Giacomelli, L; Angelone, M; Pillon, M; Villari, S; Weller, A; Petrizzi, L; Gorini, G

    2013-12-01

    Measurements of the response of LaBr3(Ce) to 2.5 MeV neutrons have been carried out at the Frascati Neutron Generator and at tokamak facilities with deuterium plasmas. The observed spectrum has been interpreted by means of a Monte Carlo model. It is found that the main contributor to the measured response is neutron inelastic scattering on (79)Br, (81)Br, and (139)La. An extrapolation of the count rate response to 14 MeV neutrons from deuterium-tritium plasmas is also presented. The results are of relevance for the design of γ-ray diagnostics of fusion burning plasmas.

  6. Neutron-induced reactions relevant for Inertial-Cofinement Fusion Experiments

    NASA Astrophysics Data System (ADS)

    Boswell, Melissa; Devlin, Mathew; Fotiadis, Nikolaos; Merrill, Frank; Nelson, Ronald; Tonchev, Anton

    2014-09-01

    The typical ignition experiment at the National Ignition Facility ablatively implodes a plastic capsule filled with DT fuel, generating a high flux of 14-MeV neutrons from the d(t,n) α reaction. There is some spread in the energy of these primary 14-MeV neutrons, which is mainly attributable to Doppler shifting from the relative thermal motion of the burning DT fuel. Neutrons created during this reaction have 5--10% chance of scattering before escaping the fuel assembly, losing some fraction of their energy in the scattering process. Neutrons emerging with an energy greater than the reaction energy are generated by a two-step process where neutrons first transfer momentum to a deuteron or tritium ion, these enhanced energy ions then fuse in flight to produce higher energy neutrons; some of these neutrons have energies in excess of 30 MeV. Measuring the fluencies of both the low- and high-energy neutrons is a powerful mechanism for studying the properties of the fuel assembly, and the various parameters important to inertial confinement fusion. We have developed a number of tools to measure the spectral characteristics of the NIF neutron spectrum. Most of these methods rely on exploiting the energy dependence of (n, γ), (n,2n), (n,3n) and (n,p) reactions on a variety o.

  7. A neutron track etch detector for electron linear accelerators in radiotherapy

    PubMed Central

    Vukovic, Branko; Faj, Dario; Poje, Marina; Varga, Maja; Radolic, Vanja; Miklavcic, Igor; Ivkovic, Ana; Planinic, Josip

    2010-01-01

    Background Electron linear accelerators in medical radiotherapy have replaced cobalt and caesium sources of radiation. However, medical accelerators with photon energies over 10 MeV generate undesired fast neutron contamination in a therapeutic X-ray photon beam. Photons with energies above 10 MeV can interact with the atomic nucleus of a high-Z material, of which the target and the head of an accelerator consist, and lead to the neutron ejection. Results and conclusions. Our neutron dosimeter, composed of the LR-115 track etch detector and boron foil BN-1 converter, was calibrated on thermal neutrons generated in the nuclear reactor of the Josef Stefan Institute (Slovenia), and applied to dosimetry of undesirable neutrons in photon radiotherapy by the linear accelerator 15 MV Siemens Mevatron. Having considered a high dependence of a cross-section between neutron and boron on neutron energy, and broad neutron spectrum in a photon beam, as well as outside the entrance door to maze of the Mevatron, we developed a method for determining the effective neutron detector response. A neutron dose rate in the photon beam was measured to be 1.96 Sv/h. Outside the Mevatron room the neutron dose rate was 0.62 μSv/h. PACS: 87.52. Ga; 87.53.St; 29.40.Wk. PMID:22933893

  8. 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.

  9. SU-E-T-90: Accuracy of Calibration of Lithium-6 and -7 Enriched LiF TLDs for Neutron Measurements in High Energy Radiotherapy

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Keehan, S; Franich, R; Taylor, M

    Purpose: To determine the potential error involved in the interpretation of neutron measurements from medical linear accelerators (linacs) using TLD-600H and TLD-700H if standard AmBe and {sup 252}Cf neutron sources are used for calibration without proper inclusion of neutron energy spectrum information. Methods: The Kerma due to neutrons can be calculated from the energy released by various nuclear interactions (elastic and inelastic scatter, (n,α), (n,p), (n,d), (n,t), (n,2n), etc.). The response of each TLD can be considered the sum of the neutron and gamma components; each proportional to the Kerma. Using the difference between the measured TLD responses and themore » ratio of the calculated Kerma for each material, the neutron component of the response can be calculated. The Monte Carlo code MCNP6 has been used to calculate the neutron energy spectra resulting from photonuclear interactions in a Varian 21EX linac. TLDs have been exposed to the mixed (γ-n) field produced by a linac and AmBe and {sup 252}Cf standard neutron sources. Results: For dosimetry of neutrons from AmBe or {sup 252}Cf sources, assuming TLD-700H insensitivity to neutrons will Result in 10% or 20% overestimation of neutron doses respectively.For dosimetry of neutrons produced in a Varian 21EX, applying a calibration factor derived from a standard AmBe or {sup 252}Cf source will Result in an overestimation of neutron fluence, by as much as a factor of 47.The assumption of TLD-700H insensitivity to neutrons produced by linacs leads to a negligible error due to the extremely high Kerma ratio (600H/700H) of 3000 for the assumed neutron spectrum. Conclusion: Lithium-enriched TLDs calibrated with AmBe and/or {sup 252}Cf neutron sources are not accurate for use under the neutron energy spectrum produced by a medical linear accelerator.« less

  10. A Gamma-Ray Burst Model Via Compressional Heating of Binary Neutron Stars

    NASA Astrophysics Data System (ADS)

    Salmonson, J. D.; Wilson, J. R.; Mathews, G. J.

    1998-12-01

    We present a model for gamma-ray bursts based on the compression of neutron stars in close binary systems. General relativistic (GR) simulations of close neutron star binaries have found compression of the neutron stars estimated to produce 1053 ergs of thermal neutrinos on a timescale of seconds. The hot neutron stars will emit neutrino pairs which will partially recombine to form 1051 to 1052 ergs of electron-positron (e^-e^+) pair plasma. GR hydrodynamic computational modeling of the e^-e^+ plasma flow and recombination yield a gamma-ray burst in good agreement with general characteristics (duration ~10 seconds, spectrum peak energy ~100 keV, total energy ~1051 ergs) of many observed gamma-ray bursts.

  11. Estimating the absolute wealth of households.

    PubMed

    Hruschka, Daniel J; Gerkey, Drew; Hadley, Craig

    2015-07-01

    To estimate the absolute wealth of households using data from demographic and health surveys. We developed a new metric, the absolute wealth estimate, based on the rank of each surveyed household according to its material assets and the assumed shape of the distribution of wealth among surveyed households. Using data from 156 demographic and health surveys in 66 countries, we calculated absolute wealth estimates for households. We validated the method by comparing the proportion of households defined as poor using our estimates with published World Bank poverty headcounts. We also compared the accuracy of absolute versus relative wealth estimates for the prediction of anthropometric measures. The median absolute wealth estimates of 1,403,186 households were 2056 international dollars per capita (interquartile range: 723-6103). The proportion of poor households based on absolute wealth estimates were strongly correlated with World Bank estimates of populations living on less than 2.00 United States dollars per capita per day (R(2)  = 0.84). Absolute wealth estimates were better predictors of anthropometric measures than relative wealth indexes. Absolute wealth estimates provide new opportunities for comparative research to assess the effects of economic resources on health and human capital, as well as the long-term health consequences of economic change and inequality.

  12. A Deuterated Neutron Detector Array For Nuclear (Astro)Physics Studies

    NASA Astrophysics Data System (ADS)

    Almaraz-Calderon, Sergio; Asher, B. W.; Barber, P.; Hanselman, K.; Perello, J. F.

    2016-09-01

    The properties of neutron-rich nuclei are at the forefront of research in nuclear structure, nuclear reactions and nuclear astrophysics. The advent of intense rare isotope beams (RIBs) has opened a new door for studies of systems with very short half-lives and possible fascinating properties. Neutron spectroscopic techniques become increasingly relevant when these neutron rich nuclei are used in a variety of experiments. At Florida State University, we are developing a neutron detector array that will allow us to perform high-resolution neutron spectroscopic studies with stable and radioactive beams. The neutron detection system consists of 16 deuterated organic liquid scintillation detectors with fast response and pulse-shape discrimination capabilities. In addition to these properties, there is the potential to use the structure in the pulse-height spectra to extract the energy of the neutrons and thus produce directly excitation spectra. This type of detector uses deuterated benzene (C6D6) as the liquid scintillation medium. The asymmetric nature of the scattering between a neutron and a deuterium in the center of mass produces a pulse-height spectrum from the deuterated scintillator which contains useful information on the initial energy of the neutron. Work supported in part by the State of Florida and NSF Grant No. 1401574.

  13. Ross filter development for absolute measurement of Al line radiation on MST

    NASA Astrophysics Data System (ADS)

    Lauersdorf, N.; Reusch, L. M.; den Hartog, D. J.; Goetz, J. A.; Franz, P.; Vanmeter, P.

    2017-10-01

    The MST has a two-color soft x-ray tomography (SXT) diagnostic that, using the double-filter technique, measures electron temperature (Te) from the slope of the soft x-ray (SXR) continuum. Because MST has an aluminum plasma-facing surface, bright Al line radiation occurs in the SXR spectrum. In past application of the double-filter technique, these lines have been filtered out using thick Be filters ( 400 μm and 800 μm), restricting the measurement temperature range to >=1 keV due to the signal strength having a positive correlation with Te. Another way to deal with the line radiation is to explicitly include it into the SXR spectrum analysis from which Te is derived. A Ross filter set has been designed to measure this line radiation, and will enable the absolute intensities of the aluminum lines to be quantified and incorporated into the analysis. The Ross filter will be used to measure Al+11 and Al+12 lines, occurring between 1.59 and 2.04 keV. By using multiple detectors with filters made of varying element concentrations, we create spectral bins in which the dominant transmission is the line radiation. Absolute measurement of Al line intensities will enable use of thinner filters in the SXT diagnostic and accurate measurement of Te < 1 keV. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Fusion Energy Sciences program under Award Numbers DE-FC02-05ER54814 and DE-SC0015474.

  14. Calculation of response matrix of CaSO 4:Dy based neutron dosimeter using Monte Carlo code FLUKA and measurement of 241Am-Be spectra

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.; Bakshi, A. K.; Tripathy, S. P.

    2010-09-01

    Response matrix for CaSO 4:Dy based neutron dosimeter was generated using Monte Carlo code FLUKA in the energy range thermal to 20 MeV for a set of eight Bonner spheres of diameter 3-12″ including the bare one. Response of the neutron dosimeter was measured for the above set of spheres for 241Am-Be neutron source covered with 2 mm lead. An analytical expression for the response function was devised as a function of sphere mass. Using Frascati Unfolding Iteration Tool (FRUIT) unfolding code, the neutron spectrum of 241Am-Be was unfolded and compared with standard IAEA spectrum for the same.

  15. Neutron radiative capture methods for surface elemental analysis

    USGS Publications Warehouse

    Trombka, J.I.; Senftle, F.; Schmadebeck, R.

    1970-01-01

    Both an accelerator and a 252Cf neutron source have been used to induce characteristic gamma radiation from extended soil samples. To demonstrate the method, measurements of the neutron-induced radiative capture and activation gamma rays have been made with both Ge(Li) and NaI(Tl) detectors, Because of the possible application to space flight geochemical analysis, it is believed that NaI(Tl) detectors must be used. Analytical procedures have been developed to obtain both qualitative and semiquantitative results from an interpretation of the measured NaI(Tl) pulse-height spectrum. Experiment results and the analytic procedure are presented. ?? 1970.

  16. Bubble-detector measurements of neutron radiation in the international space station: ISS-34 to ISS-37

    PubMed Central

    Smith, M. B.; Khulapko, S.; Andrews, H. R.; Arkhangelsky, V.; Ing, H.; Koslowksy, M. R.; Lewis, B. J.; Machrafi, R.; Nikolaev, I.; Shurshakov, V.

    2016-01-01

    Bubble detectors have been used to characterise the neutron dose and energy spectrum in several modules of the International Space Station (ISS) as part of an ongoing radiation survey. A series of experiments was performed during the ISS-34, ISS-35, ISS-36 and ISS-37 missions between December 2012 and October 2013. The Radi-N2 experiment, a repeat of the 2009 Radi-N investigation, included measurements in four modules of the US orbital segment: Columbus, the Japanese experiment module, the US laboratory and Node 2. The Radi-N2 dose and spectral measurements are not significantly different from the Radi-N results collected in the same ISS locations, despite the large difference in solar activity between 2009 and 2013. Parallel experiments using a second set of detectors in the Russian segment of the ISS included the first characterisation of the neutron spectrum inside the tissue-equivalent Matroshka-R phantom. These data suggest that the dose inside the phantom is ∼70 % of the dose at its surface, while the spectrum inside the phantom contains a larger fraction of high-energy neutrons than the spectrum outside the phantom. The phantom results are supported by Monte Carlo simulations that provide good agreement with the empirical data. PMID:25899609

  17. The Spectrum of Thermally Stimulated Surface Plasmon Polaritons of a Linear Sample

    NASA Astrophysics Data System (ADS)

    Gerasimov, V. V.; Nikitin, A. K.; Khasanov, I. Sh.; Trang, Ta Thu

    2017-12-01

    An analytical model of the spectrum of thermally stimulated surface plasmon polaritons (TSSPPs) coming to the edge of a linear conducting sample has been developed. It has been found that the spectrum of such TSSPPs obeys neither the Wien law nor the Stefan-Boltzmann law for thermal radiation. The maximum of this spectrum is shifted to the low-frequency region with respect to the spectrum of the absolutely black body, and the magnitude of the shift is proportional to the sample length. The plasmon nature of the intensity increment of thermal radiation from the edge of a plane face of a duralumin sample has been verified experimentally. It has been shown that the intensity and spectrum of this increment can be controlled both by the sample temperature and by the extension of the face.

  18. Correlation spectrometer for filtering of (quasi) elastic neutron scattering with variable resolution

    NASA Astrophysics Data System (ADS)

    Magazù, Salvatore; Mezei, Ferenc; Migliardo, Federica

    2018-05-01

    In a variety of applications of inelastic neutron scattering spectroscopy the goal is to single out the elastic scattering contribution from the total scattered spectrum as a function of momentum transfer and sample environment parameters. The elastic part of the spectrum is defined in such a case by the energy resolution of the spectrometer. Variable elastic energy resolution offers a way to distinguish between elastic and quasi-elastic intensities. Correlation spectroscopy lends itself as an efficient, high intensity approach for accomplishing this both at continuous and pulsed neutron sources. On the one hand, in beam modulation methods the Liouville theorem coupling between intensity and resolution is relaxed and time-of-flight velocity analysis of the neutron velocity distribution can be performed with 50 % duty factor exposure for all available resolutions. On the other hand, the (quasi)elastic part of the spectrum generally contains the major part of the integrated intensity at a given detector, and thus correlation spectroscopy can be applied with most favorable signal to statistical noise ratio. The novel spectrometer CORELLI at SNS is an example for this type of application of the correlation technique at a pulsed source. On a continuous neutron source a statistical chopper can be used for quasi-random time dependent beam modulation and the total time-of-flight of the neutron from the statistical chopper to detection is determined by the analysis of the correlation between the temporal fluctuation of the neutron detection rate and the statistical chopper beam modulation pattern. The correlation analysis can either be used for the determination of the incoming neutron velocity or for the scattered neutron velocity, depending of the position of the statistical chopper along the neutron trajectory. These two options are considered together with an evaluation of spectrometer performance compared to conventional spectroscopy, in particular for variable

  19. ALGORITHM BASED ON ARTIFICIAL BEE COLONY FOR UNFOLDING OF NEUTRON SPECTRA OBTAINED WITH BONNER SPHERES.

    PubMed

    Silva, Everton R; Freitas, Bruno M; Santos, Denison S; Maurício, Cláudia L P

    2018-04-13

    Occupational neutron fields usually have energies from the thermal range to some MeV and the characterization of the spectra is essential for estimation of the radioprotection quantities. Thus, the spectrum must be unfolded based on a limited number of measurements. This study implemented an algorithm based on the bee colonies behavior, named Artificial Bee Colony (ABC), where the intelligent behavior of the bees in search of food is reproduced to perform the unfolding of neutron spectra. The experimental measurements used Bonner spheres and 6LiI (Eu) detector, with irradiations using a thermal neutron flux and three reference fields: 241Am-Be, 252Cf and 252Cf (D2O). The ABC obtained good estimation of the expected spectrum even without previous information and its results were closer to expected spectra than those obtained by the SPUNIT algorithm.

  20. The total kinetic energy release in the fast neutron-induced fission of 232Th

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    King, Jonathan; Yanez, Ricardo; Loveland, Walter

    Here, the post-emission total kinetic energy release (TKE) in the neutron-induced fission of 232Th was measured (using white spectrum neutrons from LANSCE) for neutron energies from E n=3 to 91MeV. In this energy range the average post-neutron total kinetic energy release decreases from 162.3±0.3 at E n=3 MeV to 154.9±0.3 MeV at E n=91 MeV. Analysis of the fission mass distributions indicates that the decrease in TKE with increasing neutron energy is a combination of increasing yields of symmetric fission (which has a lower associated TKE) and a decrease in the TKE release in asymmetric fission.