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Sample records for high-energy neutron spectra

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  2. DT High Energy Measurements and Comparison of Multiple Spectra in a He-4 Gas Neutron Detector

    NASA Astrophysics Data System (ADS)

    Gardiner, Hannah E.; Zhu, Ting; Gokhale, Sasmit; Parker, Cody; Richard, Andrea; Massey, Thomas; Baciak, James E.; Enqvisst, Andreas; Jordan, Kelly A.

    2016-09-01

    Neutron spectroscopy is important for a variety of applications to nuclear energy, national security, and basic science research. Currently, organic scintillator neutron detectors are used as a diagnostic tool for neutron spectroscopy in DT fusion research. However, these neutron measurements generate contaminants in common organics from deuteron or carbon break-up that affects the light output spectrum. A potential solution to this problem is to use a He-4 fast neutron gas scintillator detector system. He-4 has excellent gamma rejection due to a low charge density, pulse shape discrimination, and lower light yield and deposited energy from gamma interactions. The detector will also not degrade due to high intensity background gamma radiation. The detector was irradiated with 14.1 MeV neutrons at the Edwards Accelerator Lab at Ohio University. We report on the effectiveness of the He-4 detector system to measure the resulting high energy neutrons and compare this spectrum to other neutron spectra taken with this detector.

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

    PubMed Central

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

    2009-01-01

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

  4. High energy neutron radiography

    SciTech Connect

    Gavron, A.; Morley, K.; Morris, C.; Seestrom, S.; Ullmann, J.; Yates, G.; Zumbro, J.

    1996-06-01

    High-energy spallation neutron sources are now being considered in the US and elsewhere as a replacement for neutron beams produced by reactors. High-energy and high intensity neutron beams, produced by unmoderated spallation sources, open potential new vistas of neutron radiography. The authors discuss the basic advantages and disadvantages of high-energy neutron radiography, and consider some experimental results obtained at the Weapons Neutron Research (WNR) facility at Los Alamos.

  5. 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.

  6. High energy neutron dosimeter

    DOEpatents

    Sun, Rai Ko S.F.

    1994-01-01

    A device for measuring dose equivalents in neutron radiation fields. The device includes nested symmetrical hemispheres (forming spheres) of different neutron moderating materials that allow the measurement of dose equivalents from 0.025 eV to past 1 GeV. The layers of moderating material surround a spherical neutron counter. The neutron counter is connected by an electrical cable to an electrical sensing means which interprets the signal from the neutron counter in the center of the moderating spheres. The spherical shape of the device allows for accurate measurement of dose equivalents regardless of its positioning.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  9. High-energy neutron spectroscopy with thick silicon detectors

    NASA Technical Reports Server (NTRS)

    Kinnison, James D.; Maurer, Richard H.; Roth, David R.; Haight, Robert C.

    2003-01-01

    The high-energy neutron component of the space radiation environment in thick structures such as the International Space Station contributes to the total radiation dose received by an astronaut. Detector design constraints such as size and mass have limited the energy range of neutron spectrum measurements in orbit to about 12 MeV in Space Shuttle studies. We present a new method for high-energy neutron spectroscopy using small silicon detectors that can extend these measurements to more than 500 MeV. The methodology is based on measurement of the detector response function for high-energy neutrons and inversion of this response function with measured deposition data to deduce neutron energy spectra. We also present the results of an initial shielding study performed with the thick silicon detector system for high-energy neutrons incident on polyethylene.

  10. Intercomparison of high energy neutron personnel dosimeters

    SciTech Connect

    McDonald, J.C.; Akabani, G.; Loesch, R.M.

    1993-03-01

    An intercomparison of high-energy neutron personnel dosimeters was performed to evaluate the uniformity of the response characteristics of typical neutron dosimeters presently in use at US Department of Energy (DOE) accelerator facilities. It was necessary to perform an intercomparison because there are no national or international standards for high-energy neutron dosimetry. The testing that is presently under way for the Department of Energy Laboratory Accreditation Program (DOELAP) is limited to the use of neutron sources that range in energy from about 1 keV to 2 MeV. Therefore, the high-energy neutron dosimeters presently in use at DOE accelerator facilities are not being tested effectively. This intercomparison employed neutrons produced by the {sup 9}Be(p,n){sup 9}B interaction at the University of Washington cyclotron, using 50-MeV protons. The resulting neutron energy spectrum extended to a maximum of approximately 50-MeV, with a mean energy of about 20-MeV. Intercomparison results for currently used dosimeters, including Nuclear Type A (NTA) film, thermoluminescent dosimeter (TLD)-albedo, and track-etch dosimeters (TEDs), indicated a wide variation in response to identical doses of high-energy neutrons. Results of this study will be discussed along with a description of plans for future work.

  11. Measurements of cross sections for the 209Bi(n, 4n) reaction by using high energy neutrons with continuous energy spectra

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    We measured 209Bi(n, 4n) cross sections at neutron energies En = 29.8 ± 1.8 MeV and En = 34.8 ± 1.8 MeV. Bismuth oxide samples were irradiated with the neutrons produced by impinging 30, 35 and 40 MeV proton beams on a 1.05 cm thick beryllium target, where the proton beams were from the MC-50 Cyclotron of Korea Institute of Radiological Medical Sciences (KIRAMS). The neutron flux for each proton beam energy Ep, ΦEp(En), has a broad spectrum with respect to En. By taking the difference in the neutron fluxes, the difference spectra, Φ40(En) -Φ35(En) and Φ35(En) -Φ30(En), are obatined and found to be peaked at En = 29.8 and 34.8 MeV, respectively, with a width of about 3.6 MeV. By making use of this observation and employing the TENDL-2009 library we could extract the 209Bi(n, 4n)206Bi cross sections at the aforementioned neutron energies.

  12. Neutron emission and fragment yield in high-energy fission

    SciTech Connect

    Grudzevich, O. T. Klinov, D. A.

    2013-07-15

    The KRIS special library of spectra and emission probabilities in the decays of 1500 nuclei excited up to energies between 150 and 250 MeV was developed for correctly taking into account the decay of highly excited nuclei appearing as fission fragments. The emission of neutrons, protons, and photons was taken into account. Neutron emission fromprimary fragments was found to have a substantial effect on the formation of yields of postneutron nuclei. The library was tested by comparing the calculated and measured yields of products originating from the fission of nuclei that was induced by high-energy protons. The method for calculating these yields was tested on the basis of experimental data on the thermal-neutroninduced fission of {sup 235}U nuclei.

  13. Energy spectra of high energy atmospheric neutrinos

    NASA Technical Reports Server (NTRS)

    Mitsui, K.; Minorikawa, Y.

    1985-01-01

    Focusing on high energy neutrinos ( or = 1 TeV), a new calculation of atmospheric neutrino intensities was carried out taking into account EMC effects observed in P-A collisions by accelerator, recent measurement of primary cosmic ray spectrum and results of cosmic ray muon spectrum and charge ratio. Other features of the present calculation are (1) taking into account kinematics of three body decays of kaons and charm particles in diffusion equations and (2) taking into account energy dependence of kaon production.

  14. Practical neutron dosimetry at high energies

    SciTech Connect

    McCaslin, J.B.; Thomas, R.H.

    1980-10-01

    Dosimetry at high energy particle accelerators is discussed with emphasis on physical measurements which define the radiation environment and provide an immutable basis for the derivation of any quantities subsequently required for risk evaluation. Results of inter-laboratory dosimetric comparisons are reviewed and it is concluded that a well-supported systematic program is needed which would make possible detailed evaluations and inter-comparisons of instruments and techniques in well characterized high energy radiation fields. High-energy dosimetry is so coupled with radiation transport that it is clear their study should proceed concurrently.

  15. TU-F-CAMPUS-T-01: Dose and Energy Spectra From Neutron Induced Radioactivity in Medical Linear Accelerators Following High Energy Total Body Irradiation

    SciTech Connect

    Keehan, S; Taylor, M; Franich, R; Smith, R; Dunn, L; Kron, T

    2015-06-15

    Purpose: To assess the risk posed by neutron induced activation of components in medical linear accelerators (linacs) following the delivery of high monitor unit 18 MV photon beams such as used in TBI. Methods: Gamma spectroscopy was used to identify radioisotopes produced in components of a Varian 21EX and an Elekta Synergy following delivery of photon beams. Dose and risk estimates for TBI were assessed using dose deliveries from an actual patient treatment. A 1 litre spherical ion chamber (PTW, Germany) has been used to measure the dose at the beam exit window and at the total body irradiation (TBI) treatment couch following large and small field beams with long beam-on times. Measurements were also made outside of the closed jaws to quantify the benefit of the attenuation provided by the jaws. Results: The radioisotopes produced in the linac head have been identified as {sup 187}W, {sup 56}Mn, {sup 24}Na and {sup 28}Al, which have half-lives from between 2.3 min to 24 hours. The dose at the beam exit window following an 18 MV 2197 MU TBI beam delivery was 12.6 µSv in ten minutes. The dose rate at the TBI treatment couch 4.8 m away is a factor of ten lower. For a typical TBI delivered in six fractions each consisting of four beams and an annual patient load of 24, the annual dose estimate for a staff member at the treatment couch for ten minutes is 750 µSv. This can be further reduced by a factor of about twelve if the jaws are closed before entering the room, resulting in a dose estimate of 65 µSv. Conclusion: The dose resulting from the activation products for a representative TBI workload at our clinic of 24 patients per year is 750 µSv, which can be further reduced to 65 µSv by closing the jaws.

  16. First observations of power MOSFET burnout with high energy neutrons

    SciTech Connect

    Oberg, D.L.; Wert, J.L.; Normand, E.; Majewski, P.P.; Wender, S.A.

    1996-12-01

    Single event burnout was seen in power MOSFETs exposed to high energy neutrons. Devices with rated voltage {ge}400 volts exhibited burnout at substantially less than the rated voltage. Tests with high energy protons gave similar results. Burnout was also seen in limited tests with lower energy protons and neutrons. Correlations with heavy-ion data are discussed. Accelerator proton data gave favorable comparisons with burnout rates measured on the APEX spacecraft. Implications for burnout at lower altitudes are also discussed.

  17. 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.

  18. Microchannel plate response to high-energy neutrons

    SciTech Connect

    Persing, R.; Medley, S.S.

    1981-07-01

    The response of a chevron microchannel plate (MCP) to high energy neutrons was measured. The large area (4.6 cm x 13 cm) multi-anode MCP performance characteristics in the saturated pulse counting mode of operation were examined prior to neutron testing. This established a linear operating regime in which the neutron detection efficiency was measured to be 0.17% for 2.5 MeV-DD neutrons and 0.64% for 14 MeV-DT neutrons. The higher response measured for the 14 MeV-DT neutrons is attributed to gamma ray contamination induced by neutron collisions with materials located between the neutron source and the MCP detector. Due to their lower energy, the 2.5 MeV-DD response measurements are expected to be relatively free of gamma contamination and, hence, indicative of actual response of the MCP detector to neutrons in the 1 to 10 MeV energy range.

  19. High Energy Neutron Induced Gamma Production

    SciTech Connect

    Brown, D A; Johnson, M; Navratil, P

    2007-09-28

    N Division has an interest in improving the physics and accuracy of the gamma data it provides to its customers. It was asked to look into major gamma producing reactions for 14 MeV incident neutrons for several low-Z materials and determine whether LLNL's processed data files faithfully represent the current state of experimental and theoretical knowledge for these reactions. To address this, we surveyed the evaluations of the requested materials, made recommendations for the next ENDL release and noted isotopes that will require further experimental study. This process uncovered several major problems in our translation and processing of the ENDF formatted evaluations, most of which have been resolved.

  20. Mechanical approach to the neutrons spectra collimation and detection

    SciTech Connect

    Sadeghi, H.; Roshan, M. V.

    2014-11-15

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

  1. High-Energy Neutron Backgrounds for Underground Dark Matter Experiments

    SciTech Connect

    Chen, Yu

    2016-01-01

    Direct dark matter detection experiments usually have excellent capability to distinguish nuclear recoils, expected interactions with Weakly Interacting Massive Particle (WIMP) dark matter, and electronic recoils, so that they can efficiently reject background events such as gamma-rays and charged particles. However, both WIMPs and neutrons can induce nuclear recoils. Neutrons are then the most crucial background for direct dark matter detection. It is important to understand and account for all sources of neutron backgrounds when claiming a discovery of dark matter detection or reporting limits on the WIMP-nucleon cross section. One type of neutron background that is not well understood is the cosmogenic neutrons from muons interacting with the underground cavern rock and materials surrounding a dark matter detector. The Neutron Multiplicity Meter (NMM) is a water Cherenkov detector capable of measuring the cosmogenic neutron flux at the Soudan Underground Laboratory, which has an overburden of 2090 meters water equivalent. The NMM consists of two 2.2-tonne gadolinium-doped water tanks situated atop a 20-tonne lead target. It detects a high-energy (>~ 50 MeV) neutron via moderation and capture of the multiple secondary neutrons released when the former interacts in the lead target. The multiplicity of secondary neutrons for the high-energy neutron provides a benchmark for comparison to the current Monte Carlo predictions. Combining with the Monte Carlo simulation, the muon-induced high-energy neutron flux above 50 MeV is measured to be (1.3 ± 0.2) ~ 10-9 cm-2s-1, in reasonable agreement with the model prediction. The measured multiplicity spectrum agrees well with that of Monte Carlo simulation for multiplicity below 10, but shows an excess of approximately a factor of three over Monte Carlo prediction for multiplicities ~ 10 - 20. In an effort to reduce neutron backgrounds for the dark matter experiment SuperCDMS SNO- LAB, an active neutron veto was developed

  2. Radial Distribution of Electron Spectra from High-Energy Ions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Katz, Robert; Wilson, John W.

    1998-01-01

    The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.

  3. Radial Distribution of Electron Spectra from High-Energy Ions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Katz, Robert; Wilson, John W.

    1998-01-01

    The average track model describes the response of physical and biological systems using radial dose distribution as the key physical descriptor. We report on an extension of this model to describe the average distribution of electron spectra as a function of radial distance from an ion. We present calculations of these spectra for ions of identical linear energy transfer (LET), but dissimilar charge and velocity to evaluate the differences in electron spectra from these ions. To illustrate the usefulness of the radial electron spectra for describing effects that are not described by electron dose, we consider the evaluation of the indirect events in microdosimetric distributions for ions. We show that folding our average electron spectra model with experimentally determined frequency distributions for photons or electrons provides a good representation of radial event spectra from high-energy ions in 0.5-2 micrometer sites.

  4. Effect of high-energy neutrons on MuGFETs

    NASA Astrophysics Data System (ADS)

    Kilchytska, V.; Alvarado, J.; Collaert, N.; Rooyakers, R.; Militaru, O.; Berger, G.; Flandre, D.

    2010-02-01

    This paper investigates, for the first time, the influence of high-energy neutrons on Multiple-Gate FETs (MuGFETs) with various gate lengths and fin widths. Neutron-induced degradation is addressed through the variation of major device parameters such as threshold voltage, subthreshold slope, maximum transconductance and DIBL. We demonstrate that high-energy neutrons result in total-dose effects largely similar to those caused by γ- and proton-irradiations. It is shown that, contrarily to the generally-believed immunity to irradiation, very short-channel MuGFETs can become extremely sensitive to the total-dose effect. The possible reasons of such length-dependent neutron-induced degradation are discussed and finally related to gate edges.

  5. High Energy Telescope With Neutron Detection Capabilities (HETn)

    NASA Astrophysics Data System (ADS)

    Posner, A.; Wimmer-Schweingruber, R. F.; Böhm, E.; Böttcher, s.; Connell, J. J.; Dröge, W.; Hassler, D. M.; Heber, B.; Lopate, C.; McKibben, R. B.; Steigies, C. T.

    2007-01-01

    The High-Energy Telescope with neutron detection capabilities (HETn) for the Solar Orbiter will measure and resolve energetic charged particles, in particular electrons, proton, and heavy ions up to Fe including selected isotopes up to energies equivalen to the penetration depth of 100 MeV protons. The full active anti-coincidence encloses detectors sensitive to 1-30 MeV neutrons and 0.5-5 MeV X-/gamma-rays. The sensor consists of the angle-detecting inclined sensors (ADIS) solid-state detector detector telescope utilizing a shared calorimeter for total energy and X-/gamma-ray measurement. A separate plastic detector provides sensitivity to neutrons via the recoil process. HETn will open a new window on solar eruptive events with its neutron detection capability and allows determination of high-energy close to the Sun. Timing and spectral information on neutral particles (neutrons and X-/gamma rays ), on relativistic electrons and high-energy heavy ions will provide new insights into the processes which accelerate particles to high energies at the sun and into transport processes between the source and the spacecraft in the near-Sun environment.

  6. Characterization of high-energy quasi-monoenergetic neutron energy spectra and ambient dose equivalents of 80-389 MeV 7Li(p,n) reactions using a time-of-flight method

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Araki, Shouhei; Yashima, Hiroshi; Sato, Tatsuhiko; Masuda, Akihiko; Matsumoto, Tetsuro; Nakao, Noriaki; Shima, Tatsushi; Kin, Tadahiro; Watanabe, Yukinobu; Iwase, Hiroshi; Nakamura, Takashi

    2015-12-01

    We completed a series of measurements on mono-energetic neutron energy spectra of the 7Li(p,n) reaction with 80-389-MeV protons in the 100-m time-of-flight (TOF) tunnel at the Research Center for Nuclear Physics cyclotron facility. For that purpose, we measured neutron energy spectra of the 80-, 100- and 296-MeV proton incident reactions, which had not been investigated in our previous studies. The neutron peak intensity was 0.9-1.1×1010 neutrons/sr/μC in the incident proton energy region of 80-389 MeV, and it was almost independent of the incident proton energy. The contribution of peak intensity of the spectrum to the total intensity integrated with energies above 3 MeV varied between 0.38 and 0.48 in the incident proton energy range of 80-389 MeV. To consider the correction required to derive a response in the peak region from the measured total responses of neutron monitors in the 100-m TOF tunnel, we proposed the subtraction method using energy spectra between 0° and 25°. The normalizing factor k against 25° neutron fluence to equalize it to 0° neutron fluence in the continuum region ranges from 0.74 to 1.02 depending on the incident proton energy and angle measured. Even without the TOF method, the subtraction method with the k factor almost decreases the response in the continuum region of a neutron spectrum against the total response of neutron monitors.

  7. Superheated emulsions as high-energy neutron dosemeters.

    PubMed

    Das, Mala; Sawamura, Teruko; Abe, Masashi; Kaneko, Junichi H; Homma, Akira; Fujita, Fumiyuki; Tsuda, Shuichi; Nishitani, Takeo

    2004-01-01

    Superheated emulsions being inexpensive, easy to fabricate, and having tissue equivalent composition make them as one of the popular neutron dosemeters. One more advantage is that they can be made insensitive to gamma rays by the choice of the sensitive liquid. It is observed that the response of commercially available bubble detector to neutron decreases above 20 MeV while its response is roughly flat in the 0.1-15 MeV region. This restricts its application as a dosemeter to high-energy neutrons. The response of bubble detector from Bubble Technology Industries, has been observed by using Pb-breeder for high-energy neutrons from different facilities in Japan. It is observed that 2-3 cm Pb-breeder is effective in increasing the response of the detector to the nominal value. Theoretical calculation using MCNPX code indicates an increase in neutrons in the energy range of 0.1-10 MeV with Pb-breeder. The present work indicates the possibility of using the bubble detector as a dosemeter to high-energy neutron using a Pb-breeder of proper thickness.

  8. Neutron dosimetry with TL albedo dosemeters at high energy accelerators.

    PubMed

    Haninger, T; Fehrenbacher, G

    2007-01-01

    The GSF-Personal Monitoring Service uses the TLD albedo dosemeter as standard neutron personal dosemeter. Due to its low sensitivity for fast neutrons however, it is generally not recommended for workplaces at high-energy accelerators. Test measurements with the albedo dosemeter were performed at the accelerator laboratories of GSI in Darmstadt and DESY in Hamburg to reconsider this hypothesis. It revealed that the albedo dosemeter can also be used as personal dosemeter at these workplaces, because at all measurement locations a significant part of neutrons with lower energies could be found, which were produced by scattering at walls or the ground.

  9. High-Energy Neutron Imaging Development at LLNL

    SciTech Connect

    Hall, J M; Rusnak, B; Shen, S

    2005-02-16

    We are proceeding with the development of a high-energy (10 MeV) neutron imaging system for use as an inspection tool in nuclear stockpile stewardship applications. Our goal is to develop and deploy an imaging system capable of detecting cubic-mm-scale voids, cracks or other significant structural defects in heavily-shielded low-Z materials within nuclear device components. The final production-line system will be relatively compact (suitable for use in existing facilities within the DOE complex) and capable of acquiring both radiographic and tomographic (CT) images. In this report, we will review our recent programmatic accomplishments, focusing primarily on progress made in FY04. The design status of the high-intensity, accelerator-driven neutron source and large-format imaging detector associated with the system will be discussed and results from a recent high-energy neutron imaging experiment conducted at the Ohio University Accelerator Laboratory (OUAL) will also be presented.

  10. High-energy X-ray spectra of five sources.

    NASA Technical Reports Server (NTRS)

    Ricker, G. R.; Mcclintock, J. E.; Gerassimenko, M.; Lewin , W. H. G.

    1973-01-01

    On October 15-16, 1970, we carried out balloon X-ray observations from Australia at energies above 15 keV. We present the high-energy X-ray spectra of three sources discovered by us, GX 301-2, GX 304-1, and GX 1 + 4. The data suggest that these high-energy sources correspond to the sources 2U 1223-62, 2U 1258-61, and 2U 1728-24 respectively. We also present the spectra for two additional sources, GX 5-1 (2U 1757-25) and GX 3 + 1 (2U 1744-26). The average intensity of the highly variable source GX 301-2 was observed to be as great as Tau X-1 in the energy range 15-50 keV.

  11. High energy cosmic ray charge and energy spectra measurements

    NASA Technical Reports Server (NTRS)

    Chappell, J. H.; Webber, W. R.

    1981-01-01

    In 1976, 1977, and 1978, a series of three balloon flights was conducted to measure the energy spectra of cosmic ray nuclei. A gas Cerenkov detector with different gas thresholds of 8.97, 13.12, and 17.94 GeV/n was employed to extend these measurements to high energies. The total collection factor for these flights is more than 20 sq m ster-hr. Individual charge resolution was achieved over the charge range Z equals 4-26, and overlapping differential spectra were obtained from the three flights up to approximately 100.0 GeV/n.

  12. A comparison of the response of PADC neutron dosemeters in high-energy neutron fields.

    PubMed

    Trompier, F; Boschung, M; Buffler, A; Domingo, C; Cale, E; Chevallier, M-A; Esposito, A; Ferrarini, M; Geduld, D R; Hager, L; Hohmann, E; Mayer, S; Musso, A; Romero-Esposito, M; Röttger, S; Smit, F D; Sashala Naik, A; Tanner, R; Wissmann, F; Caresana, M

    2014-10-01

    Within the framework of the EURADOS Working Group 11, a comparison of passive neutron dosemeters in high-energy neutron fields was organised in 2011. The aim of the exercise was to evaluate the response of poly-allyl-glycol-carbonate neutron dosemeters from various European dosimetry laboratories to high-energy neutron fields. Irradiations were performed at the iThemba LABS facility in South Africa with neutrons having energies up to 66 and 100 MeV. © The Author 2013. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  13. A phoswich detector for high-energy neutrons.

    PubMed

    Takada, M; Nakamura, T

    2007-01-01

    A phoswich detector was developed to measure neutron energy spectra from a few MeV to a few hundreds MeV in aircrafts and space crafts. Radiation fields, which both crafts are exposured, consist of neutrons, gamma rays, protons, etc. The phoswich detector can measure neutrons separately from gamma rays and protons. The capability of particle discrimination was tested at HIMAC and was found to be excellent. Detector response functions to neutrons were simulated with the MCNPX code using the measured light outputs of charged particles and were measured with quasi-mono-energetic neutrons produced by the p-Li reaction at the NIRS cyclotron. Test flight measurements at high altitudes, 6.5 and 8.5 km, were performed above the middle part of Japan (cut-off rigidity, 12 GV).

  14. Neutron dose per fluence and weighting factors for use at high energy accelerators

    SciTech Connect

    Cossairt, J.Donald; Vaziri, Kamran; /Fermilab

    2008-07-01

    In June 2007, the United States Department of Energy incorporated revised values of neutron weighting factors into its occupational radiation protection Regulation 10 CFR Part 835 as part of updating its radiation dosimetry system. This has led to a reassessment of neutron radiation fields at high energy proton accelerators such as those at the Fermi National Accelerator Laboratory (Fermilab). Values of dose per fluence factors appropriate for accelerator radiation fields calculated elsewhere are collated and radiation weighting factors compared. The results of this revision to the dosimetric system are applied to americium-beryllium neutron energy spectra commonly used for instrument calibrations. A set of typical accelerator neutron energy spectra previously measured at Fermilab are reassessed in light of the new dosimetry system. The implications of this revision are found to be of moderate significance.

  15. Neutron dose per fluence and weighting factors for use at high energy accelerators.

    PubMed

    Cossairt, J Donald; Vaziri, Kamran

    2009-06-01

    In June 2007, the United States Department of Energy incorporated revised values of neutron weighting factors into its occupational radiation protection regulation Title 10, Code of Federal Regulations Part 835, as part of updating its radiation dosimetry system. This has led to a reassessment of neutron radiation fields at high energy accelerators such as those at the Fermi National Accelerator Laboratory (Fermilab) in the context of the amended regulation and contemporary guidance of the International Commission on Radiological Protection (ICRP). Values of dose per fluence factors appropriate for accelerator radiation fields calculated elsewhere are collated and radiation weighting factors compared. The results of this revision to the dosimetric system are applied to americium-beryllium neutron energy spectra commonly used for instrument calibrations. Also, a set of typical accelerator neutron energy spectra previously measured at Fermilab are reassessed in light of the new dosimetry system. The implications of this revision and of recent ICRP publications are found to be of moderate significance.

  16. Neutron dose measurements with the GSI ball at high-energy accelerators.

    PubMed

    Fehrenbacher, G; Gutermuth, F; Kozlova, E; Radon, T; Schuetz, R

    2007-01-01

    A moderator-type neutron monitor containing pairs of TLD 600/700 elements (Harshaw) modified with the addition of a lead layer (GSI ball) for the measurement of the ambient dose equivalent from neutrons at medium- and high-energy accelerators, is introduced in this work. Measurements were performed with the Gesellschaft für Schwerionenforschung (GSI) ball as well as with conventional polyethylene (PE) spheres at the high-energy accelerator SPS at European Organization for Nuclear Research [CERN (CERF)] and in Cave A of the heavy-ion synchrotron SIS at GSI. The measured dose values are compared with dose values derived from calculated neutron spectra folded with dose conversion coefficients. The estimated reading of the spheres calculated by means of the response functions and the neutron spectra is also included in the comparison. The analysis of the measurements shows that the PE/Pb sphere gives an improved estimate on the ambient dose equivalent of the neutron radiation transmitted through shielding of medium- and high-energy accelerators.

  17. EGRET High Energy Capability and Multiwavelength Flare Studies and Solar Flare Proton Spectra

    NASA Technical Reports Server (NTRS)

    Chupp, Edward L.

    1997-01-01

    UNH was assigned the responsibility to use their accelerator neutron measurements to verify the TASC response function and to modify the TASC fitting program to include a high energy neutron contribution. Direct accelerator-based measurements by UNH of the energy-dependent efficiencies for detecting neutrons with energies from 36 to 720 MeV in NaI were compared with Monte Carlo TASC calculations. The calculated TASC efficiencies are somewhat lower (by about 20%) than the accelerator results in the energy range 70-300 MeV. The measured energy-loss spectrum for 207 MeV neutron interactions in NaI were compared with the Monte Carlo response for 200 MeV neutrons in the TASC indicating good agreement. Based on this agreement, the simulation was considered to be sufficiently accurate to generate a neutron response library to be used by UNH in modifying the TASC fitting program to include a neutron component in the flare spectrum modeling. TASC energy-loss data on the 1991 June 11 flare was transferred to UNH. Also included appendix: Gamma-rays and neutrons as a probe of flare proton spectra: the solar flare of 11 June 1991.

  18. High-Energy Neutron Imaging Development at LLNL

    SciTech Connect

    Hall, J; Rusnak, B; Fitsos, P

    2006-12-06

    We are proceeding with the development of a high-energy (10 MeV) neutron imaging system for use as an inspection tool in nuclear stockpile stewardship applications. Our goal is to develop and deploy an imaging system capable of detecting cubic-mm-scale voids, cracks or other significant structural defects in heavily-shielded low-Z materials within nuclear device components. The final production-line system will be relatively compact (suitable for use in existing or proposed facilities within the DOE complex) and capable of acquiring both radiographic and tomographic (CT) images. In this report, we will review our programmatic accomplishments to date, highlighting recent (FY06) progress on engineering and technology development issues related to the proposed imaging system. We will also discuss our preliminary project plan for FY07, including engineering initiatives, proposed radiation damage experiments (neutrons and x rays) and potential options for conducting classified neutron imaging experiments at LLNL.

  19. Hardness ratios of different neutron spectra.

    PubMed

    Tommasino, L; Tripathy, S P

    2004-01-01

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

  20. High-energy spectra of active nuclei. 1: The catalog

    NASA Technical Reports Server (NTRS)

    Malaguti, G.; Bassani, L.; Caroli, E.

    1994-01-01

    This paper presents a catalog of high-energy spectra (E is greater than or equal to 0.01 keV) of active galactic nuclei (AGNs). The catalog contains 209 objects (140 Seyfert galaxies, 65 quasars, and 4 objects otherwise classified), for a total of 1030 spectra. Most of the data have been collected from the literature over a period spanning more than 20 yr starting from the early 1970s up to the end of 1992. For a numbner of objects (17), EXOSAT/ME data have been extracted and analyzed, and the 27 spectra obtained have been added to the database. For each object we report individual observation spectral fit parameters using a power-law model corrected for cold gas absorption along the line of sight (photon index, 1 keV intensity and hydrogen column density), plus other relevant data. It is hoped that this database can become a useful tool for the study of the AGN phenomenon in its various aspects.

  1. Micronuclei Induction in Human Fibroblasts Exposed In Vitro to Los Alamos High-Energy Neutrons

    NASA Technical Reports Server (NTRS)

    Gersey, Brad; Sodolak, John; Hada, Megumi; Saganti, Prem; Wilkins, Richard; Cucinotta, Francis; Wu, Honglu

    2006-01-01

    High-energy secondary neutrons, produced by the interaction of galactic cosmic rays with the atmosphere, spacecraft structure and planetary surfaces, contribute to a significant fraction to the dose equivalent in crew members and passengers during commercial aviation travel, and astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility#s ICE House 30L beamline is known to generate neutrons that simulate the secondary neutron spectra of earth#s atmosphere. The neutron spectrum is also similar to that measured onboard spacecraft like the MIR and International Space Station (ISS). To evaluate the biological damage, we exposed human fibroblasts in vitro to the LANSCE neutron beams without degrader at an entrance dose rate of 25 mGy/hr and analyzed the micronuclei (MN) induction. The cells were also placed behind a 9.9 cm water column to study effect of shielding in the protection of neutron induced damages. It was found that the dose response in the MN frequency was linear for the samples with and without shielding and the slope of the MN yield behind the shielding was reduced by a factor of 3.5. Compared to the MN induction in human fibroblasts exposed to a gamma source at a low dose rate, the RBE was found to be 16.7 and 10.0 for the neutrons without and with 9.9 cm water shielding, respectively.

  2. CREAM: High Energy Frontier of Cosmic Ray Elemental Spectra

    NASA Astrophysics Data System (ADS)

    Seo, Eun-Suk

    The balloon-borne Cosmic Ray Energetics And Mass (CREAM) experiment was flown for 161 days in six flights over Antarctica. High energy cosmic-ray data were collected over a wide energy range from 10 (10) to 10 (15) eV at an average altitude of 38.5 km with 3.9 g/cm (2) atmospheric overburden. Cosmic-ray elements from protons (Z = 1) to iron nuclei (Z = 26) are separated with excellent charge resolution. Building on success of the balloon flights, the payload is being reconfigured for exposure on the International Space Station (ISS). This ISS-CREAM instrument is configured with the CREAM calorimeter for energy measurements, and four finely segmented Silicon Charge Detector layers for precise charge measurements. In addition, the Top and Bottom Counting Detectors (TCD and BCD) and Boronated Scintillator Detector (BSD) have been newly developed. The TCD and BCD are scintillator based segmented detectors to separate electrons from nuclei using the shower profile differences, while BSD distinguishes electrons from nuclei by detecting thermal neutrons that are dominant in nuclei induced showers. An order of magnitude increase in data collecting power is possible by utilizing the ISS to reach the highest energies practical with direct measurements. The project status including results from on-going analysis of existing data and future plans will be discussed.

  3. Determination of high-energy x-ray spectra by photoactivation.

    PubMed

    Nath, R; Schulz, R J

    1976-01-01

    The determination of high-energy x-ray spectra has required scintillation spectrometers with massive shielding, neutron time-of-flight spectrometers, or the tedious counting of electron tracks in nuclear emulsions. A new approach has been developed which takes advantage of the energy dependence of photoactivation cross sections. Radioactivity is produced in a small packet of C, Cu, Co, Y, Zr, and Au foils by approximately 5000 rad (tissue). Since the amount of radioactivity produced in each foil is given by the integral of the product of photonuclear cross section and differential photon fluence, a numerical method for unfolding the spectrum is required, and the orthonormal expansion has been employed for this purpose. The photoactivation method has been used to determine the x-ray spectra produced by 30-MeV electrons incident upon thin and thick tungsten targets, and filtered by equivalent amounts of lead and aluminum. These spectra have been compared to calculated thin-target spectra as well as to those determined by a neutron time-of-flight spectrometer. The central-axis and off-axis x-ray spectra produced by a 33-MeV betatron have also been determined.

  4. EGRET High Energy Capability and Multiwavelength Flare Studies and Solar Flare Proton Spectra

    NASA Technical Reports Server (NTRS)

    Chupp, Edward L.

    1998-01-01

    The accomplishments of the participation in the Compton Gamma Ray Observatory Guest investigator program is summarized in this report. The work involved the study of Energetic Gamma Ray Experiment Telescope (EGRET)/Total Absorption Shower Counter(TASC) flare data. The specific accomplishments were the use of the accelerator neutron measurements obtained at the University of New Hampshire to verify the TASC response function and to modify the TASC fitting program to include a high energy neutron contribution, and to determine a high energy neutron contribution to the emissions from the 1991 June 11, solar flare. The next step in the analysis of this event was doing fits to the TASC energy-loss spectra as a function of time. A significant hardening of the solar proton spectrum over time was found for the flare. Further data was obtained from the Yohkoh HXT time histories and images for the 1991 October 27 flare. The results to date demonstrate that the TASC spectral analysis contributes crucial information on the particle spectrum interacting at the Sun. The report includes a paper accepted for publication, a draft of a paper to be delivered at the 26th International Cosmic Ray Conference and an abstract of a paper to be presented at the Meeting of the American Physical Society.

  5. Neutron and photon spectra in LINACs.

    PubMed

    Vega-Carrillo, H R; Martínez-Ovalle, S A; Lallena, A M; Mercado, G A; Benites-Rengifo, J L

    2012-12-01

    A Monte Carlo calculation, using the MCNPX code, was carried out in order to estimate the photon and neutron spectra in two locations of two linacs operating at 15 and 18 MV. Detailed models of both linac heads were used in the calculations. Spectra were estimated below the flattening filter and at the isocenter. Neutron spectra show two components due to evaporation and knock-on neutrons. Lethargy spectra under the filter were compared to the spectra calculated from the function quoted by Tosi et al. that describes reasonably well neutron spectra beyond 1 MeV, though tends to underestimate the energy region between 10(-6) and 1 MeV. Neutron and the Bremsstrahlung spectra show the same features regardless of the linac voltage.

  6. Hexagonal boron nitride thin film thermal neutron detectors with high energy resolution of the reaction products

    NASA Astrophysics Data System (ADS)

    Doan, T. C.; Majety, S.; Grenadier, S.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2015-05-01

    Hexagonal boron nitride (h-BN) is highly promising for solid-state thermal neutron detector applications due to its many outstanding physical properties, especially its very large thermal neutron capture cross-section (~3840 barns for 10B), which is several orders of magnitude larger than those of most other isotopes. The focus of the present work is to carry out studies on h-BN thin film and detector properties to lay the foundation for the development of a direct-conversion solid-state thermal neutron detector with high sensitivity. The measured carrier mobility-lifetime (μτ) product of h-BN thin films grown on sapphire substrates is 2.83×10-7 cm2/V for electrons and holes, which is comparable to the value of about 10-7 cm2/V for GaN thin films grown on sapphire. Detectors based on h-BN thin films were fabricated and the nuclear reaction product pulse height spectra were measured. Under a bias of 20 V, very narrow individual peaks corresponding to the reaction product energies of α and Li particles as well as the sum peaks have been clearly resolved in the pulse height spectrum for the first time by a B-based direct-conversion semiconductor neutron detector. Our results indicate that h-BN thin film detectors possess unique advantages including small size, low weight, portability, low voltage operation and high energy resolution of specific reaction products.

  7. Implications for High Energy Blazar Spectra from Intergalactic Absorption Calculations

    NASA Technical Reports Server (NTRS)

    Stecker, F

    2008-01-01

    Given a knowledge of the density spectra intergalactic low energy photons as a function of redshift, one can derive the intrinsic gamma-ray spectra and luminosities of blazars over a range of redshifts and look for possible trends in blazar evolution. Stecker, Baring & Summerlin have found some evidence hinting that TeV blazars with harder spectra have higher intrinsic TeV gamma-ray luminosities and indicating that there may be a correlation of spectral hardness and luminosity with redshift. Further work along these lines, treating recent observations of the blazers lES02291+200 and 3C279 in the TeV and sub-TeV energy ranges, has recently been explored by Stecker & Scully. GLAST will observe and investigate many blazars in the GeV energy range and will be sensitive to blazers at higher redshifts. I examine the implications high redshift gamma-ray absorption for both theoretical and observational blazer studies.

  8. Gravitational effects on planetary neutron flux spectra

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  9. 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.

  10. NaI detector neutron activation spectra for PGNAA applications

    PubMed

    Gardner; El; Zheng; Hayden; Mayo

    2000-10-01

    When NaI detectors are used in prompt gamma-ray neutron activation analysis devices, they are activated by neutrons that penetrate the detector. While thermal neutron filters like boron or lithium can be used to reduce this activation, it can never be completely eliminated by this approach since high energy neutrons can penetrate the detector and thermalize inside it. This activation results in the emission of prompt gamma rays from both the I and Na and the production of the radioisotopes 128I and 24Na that subsequently decay and emit their characteristic beta particles and gamma rays. The resulting three spectra represent a background for this measurement. An experimental method for obtaining these three spectra is described and results are reported for 2" x 2", 5" x 5", 6" x 6", and 1" x 6" NaI detectors using the thermal neutron beam of the NCSU PULSTAR nuclear reactor. In addition, Monte Carlo simulation programs have been developed and used for simulating these spectra. Good results have been obtained by the Monte Carlo method for the two radioisotope spectra, and it is anticipated that good results will also be obtained for the prompt gamma-ray spectrum when the I and Na coincidence schemes are known.

  11. Prompt fission neutron spectra of actinides

    SciTech Connect

    Capote, R.; Chen, Y. -J.; Hambsch, F. -J.; Kornilov, N. V.; Lestone, J. P.; Litaize, O.; Morillon, B.; Neudecker, D.; Oberstedt, S.; Ohsawa, T.; Otuka, N.; Pronyaev, V. G.; Saxena, A.; Serot, O.; Shcherbakov, O. A.; Shu, N. -C.; Smith, D. L.; Talou, P.; Trkov, A.; Tudora, A. C.; Vogt, R.; Vorobyev, A. S.

    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. 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.

  13. Neutron production in tissue-like media and shielding materials irradiated with high-energy ion beams.

    PubMed

    Gudowska, I; Kopec, M; Sobolevsky, N

    2007-01-01

    Secondary neutrons produced in high-energy therapeutic ion beams require special attention since they contribute to the dose delivered to patient, both to tumour and to the healthy tissues. Moreover, monitoring of neutron production in the beam line elements and the patient is of importance for radiation protection aspects around ion therapy facility. Monte Carlo simulations of light ion transport in the tissue-like media (water, A-150, PMMA) and materials of interest for shielding devices (graphite, steel and Pb) were performed using the SHIELD-HIT and MCNPX codes. The capability of the codes to reproduce the experimental data on neutron spectra differential both in energy and angle is demonstrated for neutron yield from the thick targets. Both codes show satisfactory agreement with the experimental data. The absorbed dose due to neutrons produced in the water and A-150 phantoms is calculated for proton (200 MeV) and carbon (390 MeV/u) beams. Secondary neutron dose contribution is approximately 0.6% of the total dose delivered to the phantoms by proton beam and at the similar level for both materials. For carbon beam the neutron dose contribution is approximately 1.0 and 1.2% for the water and A-150 phantoms, respectively. The neutron ambient dose equivalent, H(10), was determined for neutrons leaving different shielding materials after irradiation with ions of various energies.

  14. Characteristics of high-energy neutrons estimated using the radioactive spallation products of Au at the 500-MeV neutron irradiation facility of KENS.

    PubMed

    Matsumura, Hiroshi; Masumoto, Kazuyoshi; Nakao, Noriaki; Wang, Qingbin; Toyoda, Akihiro; Kawai, Masayoshi; Aze, Takahiro; Fujimura, Masatsugu

    2005-01-01

    We carried out a shielding experiment of high-energy neutrons, generated from a tungsten target bombarded with primary 500-MeV protons at KENS, which penetrated through a concrete shield in the zero-degree direction. We propose a new method to evaluate the spectra of high-energy neutrons ranging from 8 to 500 MeV. Au foils were set in a concrete shield, and the reaction rates for 13 radionuclides produced by the spallation reactions on the Au targets were measured by radiochemical techniques. The experimental results were compared with those obtained by the MARS14 Monte-Carlo code. A good agreement (between them) was found for energies beyond 100 MeV. The profile of the neutron spectrum, ranging from 8 to 500 MeV, does not depend on the thickness of the concrete shield.

  15. X-ray spectra of Hercules X-1. 3: Pulse phase dependence in high energy continuum

    NASA Technical Reports Server (NTRS)

    Pravdo, S. H.; Bussard, R. W.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; Swank, J. H.

    1978-01-01

    Pulse phase-dependent spectral changes in the high energy (less than 20 keV) continuum of Hercules X-1 were observed. Cyclotron absorption of underlying continua can reproduce the observed angular dependence in the high energy cutoff. Implications of this model, which include the possibility of determining the angular separation between the line of sight and the neutron star magnetic field if the absorbing electron spectrum is known are discussed.

  16. High energy neutron and gamma-radiation generated during the solar flares

    NASA Technical Reports Server (NTRS)

    Kocharov, G. E.; Mandzhavidze, N. Z.

    1985-01-01

    The problem of high energy neutrons and gamma rays generation in the solar conditions is considered. It is shown that due to a peculiarity of generation and propagation of neutrons corresponding solar flares should be localized at high helio-longitudes.

  17. Interpreting inertial fusion neutron spectra

    NASA Astrophysics Data System (ADS)

    Munro, David H.

    2016-03-01

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

  18. A Canadian high-energy neutron spectrometry system for measurements in space

    NASA Astrophysics Data System (ADS)

    Jonkmans, G.; Andrews, H. R.; Clifford, E. T. H.; Frketich, G.; Ing, H.; Koslowsky, V. T.; Noulty, R. A.; Miller, R. C.; Zhou, Y.; Mortimer, A.; Peterson, D.; Wilkinson, R.

    2005-05-01

    Bubble Technology Industries Inc. (BTI), with the support of the Canadian Space Agency, has finished the construction of the Canadian High-Energy Neutron Spectrometry System (CHENSS). This spectrometer is intended to measure the high-energy neutron spectrum ( ˜1-100MeV) encountered in spacecraft in low earth orbit. CHENSS is designed to fly aboard a US space shuttle and its scientific results should facilitate the prediction of neutron dose to astronauts in space from readings of different types of radiation dosimeters that are being used in various missions.

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

    SciTech Connect

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

    2015-11-15

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

  20. 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

  1. Neutron Spectra in a 15 MV LINAC

    SciTech Connect

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

    2010-12-07

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

  2. Neutron Spectra in a 15 MV LINAC

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  3. Neutron productions in the fragmentation of relativistic heavy nuclei and formation of a beam of high-energy neutrons

    SciTech Connect

    Yurevich, V. I.

    2016-03-15

    The production of quasimonoenergetic high-energy neutrons at zero angle (0°) in the spallation of relativistic heavy nuclei is discussed by considering the example of the interaction of lead nuclei with light target nuclei. It is shown that this process can be used to generate a beam of high-energy neutrons at existing heavy ion accelerators. At the same time, itmay lead to the appearance of a parasitic neutron beam because of the interaction of the heavy-ion beam used with beam line and experimental setup materials.

  4. Measurement of High-Energy Neutron Flux Above Ground Utilizing a Spallation Based Multiplicity Technique

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Cosmogenic high-energy neutrons are a ubiquitous, difficult to shield, poorly measured background. Above ground the high-energy neutron energy-dependent flux has been measured, with significantly varying results. Below ground, high-energy neutron fluxes are largely unmeasured. Here we present a reconstruction algorithm to unfold the incident neutron energy-dependent flux measured using the Multiplicity and Recoil Spectrometer (MARS), simulated test cases to verify the algorithm, and provide a new measurement of the above ground high-energy neutron energy-dependent flux with a detailed systematic uncertainty analysis. Uncertainty estimates are provided based upon the measurement statistics, the incident angular distribution, the surrounding environment of the Monte Carlo model, and the MARS triggering efficiency. Quantified systematic uncertainty is dominated by the assumed incident neutron angular distribution and surrounding environment of the Monte Carlo model. The energy-dependent neutron flux between 90 MeV and 400 MeV is reported. Between 90 MeV and 250 MeV the MARS results are comparable to previous Bonner sphere measurements. Over the total energy regime measured, the MARS result are located within the span of previous measurements. These results demonstrate the feasibility of future below ground measurements with MARS.

  5. Measurement of high-energy neutron flux above ground utilizing a spallation based multiplicity technique

    DOE PAGES

    Roecker, Caleb; Bernstein, Adam; Marleau, Peter; ...

    2016-11-14

    Cosmogenic high-energy neutrons are a ubiquitous, difficult to shield, poorly measured background. Above ground the high-energy neutron energy-dependent flux has been measured, with significantly varying results. Below ground, high-energy neutron fluxes are largely unmeasured. Here we present a reconstruction algorithm to unfold the incident neutron energy-dependent flux measured using the Multiplicity and Recoil Spectrometer (MARS), simulated test cases to verify the algorithm, and provide a new measurement of the above ground high-energy neutron energy-dependent flux with a detailed systematic uncertainty analysis. Uncertainty estimates are provided based upon the measurement statistics, the incident angular distribution, the surrounding environment of the Montemore » Carlo model, and the MARS triggering efficiency. Quantified systematic uncertainty is dominated by the assumed incident neutron angular distribution and surrounding environment of the Monte Carlo model. The energy-dependent neutron flux between 90 MeV and 400 MeV is reported. Between 90 MeV and 250 MeV the MARS results are comparable to previous Bonner sphere measurements. Over the total energy regime measured, the MARS result are located within the span of previous measurements. Lastly, these results demonstrate the feasibility of future below ground measurements with MARS.« less

  6. Measurement of high-energy neutron flux above ground utilizing a spallation based multiplicity technique

    SciTech Connect

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

    2016-11-14

    Cosmogenic high-energy neutrons are a ubiquitous, difficult to shield, poorly measured background. Above ground the high-energy neutron energy-dependent flux has been measured, with significantly varying results. Below ground, high-energy neutron fluxes are largely unmeasured. Here we present a reconstruction algorithm to unfold the incident neutron energy-dependent flux measured using the Multiplicity and Recoil Spectrometer (MARS), simulated test cases to verify the algorithm, and provide a new measurement of the above ground high-energy neutron energy-dependent flux with a detailed systematic uncertainty analysis. Uncertainty estimates are provided based upon the measurement statistics, the incident angular distribution, the surrounding environment of the Monte Carlo model, and the MARS triggering efficiency. Quantified systematic uncertainty is dominated by the assumed incident neutron angular distribution and surrounding environment of the Monte Carlo model. The energy-dependent neutron flux between 90 MeV and 400 MeV is reported. Between 90 MeV and 250 MeV the MARS results are comparable to previous Bonner sphere measurements. Over the total energy regime measured, the MARS result are located within the span of previous measurements. Lastly, these results demonstrate the feasibility of future below ground measurements with MARS.

  7. FIELD CALIBRATION OF A TLD ALBEDO DOSEMETER IN THE HIGH-ENERGY NEUTRON FIELD OF CERF.

    PubMed

    Haninger, T; Kleinau, P; Haninger, S

    2016-07-15

    The new albedo dosemeter-type AWST-TL-GD 04 has been calibrated in the CERF neutron field (Cern-EU high-energy Reference Field). This type of albedo dosemeter is based on thermoluminescent detectors (TLDs) and used by the individual monitoring service of the Helmholtz Zentrum München (AWST) since 2015 for monitoring persons, who are exposed occupationally against photon and neutron radiation. The motivation for this experiment was to gain a field specific neutron correction factor Nn for workplaces at high-energy particle accelerators. Nn is a dimensionless factor relative to a basic detector calibration with (137)Cs and is used to calculate the personal neutron dose in terms of Hp(10) from the neutron albedo signal. The results show that the sensitivity of the albedo dosemeter for this specific neutron field is not significantly lower as for fast neutrons of a radionuclide source like (252)Cf. The neutron correction factor varies between 0.73 and 1.16 with a midrange value of 0.94. The albedo dosemeter is therefore appropriate to monitor persons, which are exposed at high-energy particle accelerators.

  8. Determination of the neutron fluence spectra in the neutron therapy room of KIRAMS.

    PubMed

    Kim, B H; Kim, J S; Kim, J L; Kim, Y S; Yang, T G; Lee, M Y

    2007-01-01

    High energy proton induced neutron fluence spectra were determined at the Korea Institute of Radiological and Medical Sciences (KIRAMS) using an extended Bonner Sphere (BS) set from the Korea Atomic Energy Research Institute (KAERI) in a series of measurements to quantify the neutron field. At the facility of the MC50 cyclotron of KIRAMS, two Be targets of different thicknesses, 1.0 and 10.5 mm, were bombarded by 35 and 45-MeV protons to produce six kinds of neutron fields, which were classified according to the measurement position and the use or no use of a beam collimator such as the gantry of the neutron therapy unit. In order to obtain a priori information to unfold the measured BS data the MCNPX code was used to calculate the neutron spectrum, and the influence of the surrounding materials for cooling the target assembly were also reviewed through this calculation. Some dosimetric quantities were determined by using the spectra determined in this measurement. Dose equivalent rates of these neutron fields ranged from 0.21 to 5.66 mSv h(-1)nA(-1) and the neutron yields for a thick Be target were 3.05 and 4.77% in the case of using a 35 and a 45-MeV proton, respectively.

  9. Generation of high-energy neutron beam by fragmentation of relativistic heavy nuclei

    NASA Astrophysics Data System (ADS)

    Yurevich, Vladimir

    2016-09-01

    The phenomenon of multiple production of neutrons in reactions with heavy nuclei induced by high-energy protons and light nuclei is analyzed using a Moving Source Model. The Lorentz transformation of the obtained neutron distributions is used to study the neutron characteristics in the inverse kinematics where relativistic heavy nuclei bombard a light-mass target. The neutron beam generated at 0∘has a Gaussian shape with a maximum at the energy of the projectile nucleons and an energy resolution σE/E < 4% above 6 GeV.

  10. ICF ignition capsule neutron, gamma ray, and high energy x-ray images

    NASA Astrophysics Data System (ADS)

    Bradley, P. A.; Wilson, D. C.; Swenson, F. J.; Morgan, G. L.

    2003-03-01

    Post-processed total neutron, RIF neutron, gamma-ray, and x-ray images from 2D LASNEX calculations of burning ignition capsules are presented. The capsules have yields ranging from tens of kilojoules (failures) to over 16 MJ (ignition), and their implosion symmetry ranges from prolate (flattest at the hohlraum equator) to oblate (flattest towards the laser entrance hole). The simulated total neutron images emphasize regions of high DT density and temperature; the reaction-in-flight neutrons emphasize regions of high DT density; the gamma rays emphasize regions of high shell density; and the high energy x rays (>10 keV) emphasize regions of high temperature.

  11. Biological effects of high-energy neutrons measured in vivo using a vertebrate model.

    PubMed

    Kuhne, Wendy W; Gersey, Brad B; Wilkins, Richard; Wu, Honglu; Wender, Stephen A; George, Varghese; Dynan, William S

    2009-10-01

    Interaction of solar protons and galactic cosmic radiation with the atmosphere and other materials produces high-energy secondary neutrons from below 1 to 1000 MeV and higher. Although secondary neutrons may provide an appreciable component of the radiation dose equivalent received by space and high-altitude air travelers, the biological effects remain poorly defined, particularly in vivo in intact organisms. Here we describe the acute response of Japanese medaka (Oryzias latipes) embryos to a beam of high-energy spallation neutrons that mimics the energy spectrum of secondary neutrons encountered aboard spacecraft and high-altitude aircraft. To determine RBE, embryos were exposed to 0-0.5 Gy of high-energy neutron radiation or 0-15 Gy of reference gamma radiation. The radiation response was measured by imaging apoptotic cells in situ in defined volumes of the embryo, an assay that provides a quantifiable, linear dose response. The slope of the dose response in the developing head, relative to reference gamma radiation, indicates an RBE of 24.9 (95% CI 13.6-40.7). A higher RBE of 48.1 (95% CI 30.0-66.4) was obtained based on overall survival. A separate analysis of apoptosis in muscle showed an overall nonlinear response, with the greatest effects at doses of less than 0.3 Gy. Results of this experiment indicate that medaka are a useful model for investigating biological damage associated with high-energy neutron exposure.

  12. Slow neutron leakage spectra from spallation neutron sources

    SciTech Connect

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

    1980-02-01

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

  13. Neutron skin and centrality classification in high-energy heavy-ion collisions at the LHC

    NASA Astrophysics Data System (ADS)

    Paukkunen, Hannu

    2015-05-01

    The concept of centrality in high-energy nuclear collisions has recently become a subject of an active debate. In particular, the experimental methods to determine the centrality that have given reasonable results for many observables in high-energy lead-lead collisions at the LHC have led to surprising behavior in the case of proton-lead collisions. In this letter, we discuss the possibility to calibrate the experimental determination of centrality by asymmetries caused by mutually different spatial distributions of protons and neutrons inside the nuclei - a well-known phenomenon in nuclear physics known as the neutron-skin effect.

  14. Improving the neutron-to-photon discrimination capability of detectors used for neutron dosimetry in high energy photon beam radiotherapy.

    PubMed

    Irazola, L; Terrón, J A; Bedogni, R; Pola, A; Lorenzoli, M; Sánchez-Nieto, B; Gómez, F; Sánchez-Doblado, F

    2016-09-01

    The increasing interest of the medical community to radioinduced second malignancies due to photoneutrons in patients undergoing high-energy radiotherapy, has stimulated in recent years the study of peripheral doses, including the development of some dedicated active detectors. Although these devices are designed to respond to neutrons only, their parasitic photon response is usually not identically zero and anisotropic. The impact of these facts on measurement accuracy can be important, especially in points close to the photon field-edge. A simple method to estimate the photon contribution to detector readings is to cover it with a thermal neutron absorber with reduced secondary photon emission, such as a borated rubber. This technique was applied to the TNRD (Thermal Neutron Rate Detector), recently validated for thermal neutron measurements in high-energy photon radiotherapy. The positive results, together with the accessibility of the method, encourage its application to other detectors and different clinical scenarios. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Neutron production from flattening filter free high energy medical linac: A Monte Carlo study

    NASA Astrophysics Data System (ADS)

    Najem, M. A.; Abolaban, F. A.; Podolyák, Z.; Spyrou, N. M.

    2015-11-01

    One of the problems arising from using a conventional linac at high energy (>8 MV) is the production of neutrons. One way to reduce neutron production is to remove the flattening filter (FF). The main purpose of this work was to study the effect of FF removal on neutron fluence and neutron dose equivalent inside the treatment room at different photon beam energies. Several simulations based on Monte Carlo techniques were carried out in order to calculate the neutron fluence at different locations in the treatment room from different linac energies with and without a FF. In addition, a step-and-shoot intensity modulated radiotherapy (SnS IMRT) for prostate cancer was modelled using the 15 MV photon beam with and without a FF on a water phantom to calculate the neutron dose received in a full treatment. The results obtained show a significant drop-off in neutrons fluence and dose equivalent when the FF was removed. For example, the neutron fluence was decreased by 54%, 76% and 75% for 10, 15 and 18 MV, respectively. This can decrease the neutron dose to the patient as well as reduce the shielding cost of the treatment room. The neutron dose equivalent of the SnS IMRT for prostate cancer was reduced significantly by 71.3% when the FF was removed. It can be concluded that the flattening filter removal from the head of the linac could reduce the risk of causing secondary cancers and the shielding cost of radiotherapy treatment rooms.

  16. 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

  17. A diamond 14 MeV neutron energy spectrometer with high energy resolution

    SciTech Connect

    Shimaoka, Takehiro Kaneko, Junichi H.; Tsubota, Masakatsu; Shimmyo, Hiroaki; Ochiai, Kentaro; Chayahara, Akiyoshi; Umezawa, Hitoshi; Shikata, Shin-ichi; Watanabe, Hideyuki; Isobe, Mitsutaka; Osakabe, Masaki

    2016-02-15

    A self-standing single-crystal chemical vapor deposited diamond was obtained using lift-off method. It was fabricated into a radiation detector and response function measurements for 14 MeV neutrons were taken at the fusion neutronics source. 1.5% of high energy resolution was obtained by using the {sup 12}C(n, α){sup 9}Be reaction at an angle of 100° with the deuteron beam line. The intrinsic energy resolution, excluding energy spreading caused by neutron scattering, slowing in the target and circuit noises was 0.79%, which was also the best resolution of the diamond detector ever reported.

  18. Energy and angular dependence of active-type personal dosemeter for high-energy neutron.

    PubMed

    Rito, Hirotaka; Yamauchi, Tomoya; Oda, Keiji

    2011-07-01

    In order to develop an active-type personal dosemeter having suitable sensitivity to high-energy neutrons, the characteristic response of silicon surface barrier detector has been investigated experimentally and theoretically. An agreement of the shape of pulse-height distribution, its change with radiator thickness and the relative sensitivity was confirmed between the calculated and experimental results for 14.8-MeV neutrons. The angular dependence was estimated for other neutron energies, and found that the angular dependence decreased with the incident energy. The reason was also discussed with regard to the radiator thickness relative to maximum range of recoil protons.

  19. Development and Characterization of a High-Energy Neutron Time-of-Flight Imaging System

    DOE PAGES

    Madden, Amanda Christine; Schirato, Richard C.; Swift, Alicia L.; ...

    2017-02-09

    We present that Los Alamos National Laboratory has developed a prototype of a high-energy neutron time-of-flight imaging system for the non-destructive evaluation of dense, massive, and/or high atomic number objects. High-energy neutrons provide the penetrating power, and thus the high dynamic range necessary to image internal features and defects of such objects. The addition of the time gating capability allows for scatter rejection when paired with a pulsed monoenergetic beam, or neutron energy selection when paired with a pulsed broad-spectrum neutron source. The Time Gating to Reject Scatter and Select Energy (TiGReSSE) system was tested at the Los Alamos Neutronmore » Science Center’s (LANSCE) Weapons Nuclear Research (WNR) facility, a spallation neutron source, to provide proof of concept measurements and to characterize the instrument response. This paper will show results of several objects imaged during this run cycle. In addition, results from system performance metrics such as the Modulation Transfer Function and the Detective Quantum Efficiency measured as a function of neutron energy, characterize the current system performance and inform the next generation of neutron imaging instrument.« less

  20. Monte Carlo calibration of the SMM gamma ray spectrometer for high energy gamma rays and neutrons

    NASA Technical Reports Server (NTRS)

    Cooper, J. F.; Reppin, C.; Forrest, D. J.; Chupp, E. L.; Share, G. H.; Kinzer, R. L.

    1985-01-01

    The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission spacecraft was primarily designed and calibrated for nuclear gamma ray line measurements, but also has a high energy mode which allows the detection of gamma rays at energies above 10 MeV and solar neutrons above 20 MeV. The GRS response has been extrapolated until now for high energy gamma rays from an early design study employing Monte Carlo calculations. The response to 50 to 600 MeV solar neutrons was estimated from a simple model which did not consider secondary charged particles escaping into the veto shields. In view of numerous detections by the GRS of solar flares emitting high energy gamma rays, including at least two emitting directly detectable neutrons, the calibration of the high energy mode in the flight model has been recalculated by the use of more sophisticated Monte Carlo computer codes. New results presented show that the GRS response to gamma rays above 20 MeV and to neutrons above 100 MeV is significantly lower than the earlier estimates.

  1. Development of high-energy neutron imaging for use in NDE applications

    SciTech Connect

    Dietrich, F; Hall, J; Logan, C; Schmid, G

    1999-06-01

    We are currently developing a high-energy (10 - 15 MeV) neutron imaging system for use in NDE applications. Our goal is to develop an imaging system capable of detecting cubic-mm-scale voids or other structural defects in heavily-shielded low-Z materials within thick sealed objects. The system will be relatively compact (suitable for use in a small laboratory) and capable of acquiring tomographic image data sets. The design of a prototype imaging detector and multi-axis staging system will be discussed and selected results from recent imaging experiments will be presented. The development of an intense, accelerator-driven neutron source suitable for use with the imaging system will also be discussed. Keywords: neutron imaging, neutron radiography, computed tomography, non-destructive inspection, neutron sources

  2. Liquid lithium target as a high intensity, high energy neutron source

    DOEpatents

    Parkin, Don M.; Dudey, Norman D.

    1976-01-01

    This invention provides a target jet for charged particles. In one embodiment the charged particles are high energy deuterons that bombard the target jet to produce high intensity, high energy neutrons. To this end, deuterons in a vacuum container bombard an endlessly circulating, free-falling, sheet-shaped, copiously flowing, liquid lithium jet that gushes by gravity from a rectangular cross-section vent on the inside of the container means to form a moving web in contact with the inside wall of the vacuum container. The neutrons are produced via break-up of the beam in the target by stripping, spallation and compound nuclear reactions in which the projectiles (deuterons) interact with the target (Li) to produce excited nuclei, which then "boil off" or evaporate a neutron.

  3. High-energy neutron dosimetry at the Clinton P. Anderson Meson Physics Facility

    SciTech Connect

    Mallett, M.W.; Vasilik, D.G.; Littlejohn, G.J.; Cortez, J.R.

    1990-01-01

    Neutron energy spectrum measurements performed at the Clinton P. Anderson Meson Physics Facility indicated potential areas for high energy neutron exposure to personnel. The low sensitivity of the Los Alamos thermoluminescent dosimeter (TLD) to high energy neutrons warranted issuing a NTA dosimeter in addition to the TLD badge to employees entering these areas. The dosimeter consists of a plastic holder surrounding NTA film that has been desiccated and sealed in a dry nitrogen environment. A study of the fading of latent images in NTA film demonstrated the success of this packaging method to control the phenomenon. The Los Alamos NTA dosimeter is characterized and the fading study discussed. 10 refs., 4 figs., 2 tabs.

  4. Measurement of the High-Energy Neutron Flux Above and Below Ground

    NASA Astrophysics Data System (ADS)

    Roecker, Caleb Daniel

    This dissertation introduces the new multiplicity measurement approach, the MCMC inversion algorithm, the Monte Carlo model and associated calibrations, and presents results from the four measurements. Above ground, the MARS measurement results agree with most of the previous measurements in the energy range between 90 MeV and 250 MeV. Above 250 MeV the MARS results report slightly lower flux than most of the previous measurements, but are still within the spread of all previous measurements. Below ground, no direct comparison can be made to the MARS results at 377 m.w.e. The MARS result at 540 m.w.e. appears to be in rough agreement with one of the previous below ground measurements, at the one measured energy where the results overlap. At 1450 m.w.e., the MARS results shows reasonable agreement with previous simulation predictions. The rough agreement of the MARS results, at all relevant locations, with previous measurements and existing simulation where applicable, provide confidence that all MARS measurements have produced the correct high-energy neutron energy-dependent flux. Above ground, the new independent results strengthen the results of previous measurements. Below ground, the three measurements provide consistent results with minimal detector related bias between measurements due to the transportable nature of MARS, that will be used to produce a depth-dependent model of the high-energy neutron energy-dependent flux. For the rare-event particle and nuclear physics experiments affected by high-energy neutron backgrounds, this model will allow for the prediction of the high-energy neutron background at different measurement locations, a more robust instrumental design, and the ability to estimate the high-energy neutron background contribution in their final measured data; the confidence in the results of these experiments will be improved. (Abstract shortened by ProQuest.).

  5. Biological Effects of High-Energy Neutrons Measured In Vivo Using a Vertebrate Model

    PubMed Central

    Kuhne, Wendy W.; Gersey, Brad B.; Wilkins, Richard; Wu, Honglu; Wender, Stephen A.; George, Varghese; Dynan, William S.

    2009-01-01

    Interaction of solar protons and galactic cosmic radiation with the atmosphere and other materials produces high-energy secondary neutrons from below 1 to 1000 MeV and higher. Although secondary neutrons may provide an appreciable component of the radiation dose equivalent received by space and high-altitude air travelers, the biological effects remain poorly defined, particularly in vivo in intact organisms. Here we describe the acute response of Japanese medaka (Oryzias latipes) embryos to a beam of high-energy spallation neutrons that mimics the energy spectrum of secondary neutrons encountered aboard spacecraft and high-altitude aircraft. To determine RBE, embryos were exposed to 0–0.5 Gy of high-energy neutron radiation or 0–15 Gy of reference γ radiation. The radiation response was measured by imaging apoptotic cells in situ in defined volumes of the embryo, an assay that provides a quantifiable, linear dose response. The slope of the dose response in the developing head, relative to reference γ radiation, indicates an RBE of 24.9 (95% CI 13.6–40.7). A higher RBE of 48.1 (95% CI 30.0–66.4) was obtained based on overall survival. A separate analysis of apoptosis in muscle showed an overall nonlinear response, with the greatest effects at doses of less than 0.3 Gy. Results of this experiment indicate that medaka are a useful model for investigating biological damage associated with high-energy neutron exposure. PMID:19772468

  6. Extensions of the direct-semidirect model for calculating the high energy component of fast-nucleon induced gamma spectra

    SciTech Connect

    Dietrich, F S

    2000-05-22

    This section reviews extensions and variations of the direct-semidirect (DSD) model for understanding the high-energy component of gamma spectra resulting from radiative capture of fast nucleons; i.e., the part of the spectrum that is not amenable to standard statistical model (Hauser-Feshbach) treatments. We describe recent results on the extension of the DSD model to unbound final states, including comparison with proton and neutron capture data. The importance of including convective-current magnetic radiation to explain proton capture angular distributions in the 30 MeV region is shown. We conclude with a brief discussion of a model closely related to the DSD, the pure-resonance model.

  7. 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.

  8. Demonstrating a directional detector based on neon for characterizing high energy neutrons

    NASA Astrophysics Data System (ADS)

    Hexley, Allie

    2016-03-01

    MITPC is a gas-based time projection chamber used for detecting fast, MeV-scale neutrons. The standard version of the detector relies on a mixture of 600 torr gas composed of 87.5% helium-4 and 12.5% tetrafluoromethane for precisely measuring the energy and direction of neutron-induced nuclear recoils. I describe studies performed with a prototype detector investigating the use of neon, as a replacement for helium-4, in the gas mixture. My discussion focuses on the advantages of neon as the fast neutron target for high energy neutron events (100 MeV) and a demonstration that the mixture will be effective for this event class. I show that the achievable gain and transverse diffusion of drifting electrons in the neon mixture are acceptable and that the detector uptime lost due to voltage breakdowns in the amplification plane is negligible, compared to 20% with the helium-4 mixture.

  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. Simulation of a high energy neutron irradiation facility at beamline 11 of the China Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Tairan, Liang; Zhiduo, Li; Wen, Yin; Fei, Shen; Quanzhi, Yu; Tianjiao, Liang

    2017-07-01

    The China Spallation Neutron Source (CSNS) will accommodate 20 neutron beamlines at its first target station. These beamlines serve different purposes, and beamline 11 is designed to analyze the degraded models and damage mechanisms, such as Single Event Effects in electronic components and devices for aerospace electronic systems. This paper gives a preliminary discussion on the scheme of a high energy neutron irradiation experiment at the beamline 11 shutter based on the Monte Carlo simulation method. The neutron source term is generated by calculating the neutrons scattering into beamline 11 with a model that includes the target-moderator-reflector area. Then, the neutron spectrum at the sample position is obtained. The intensity of neutrons with energy of hundreds of MeV is approximately 1E8 neutron/cm2/s, which is useful for experiments. The displacement production rate and gas productions are calculated for common materials such as tungsten, tantalum and SS316. The results indicate that the experiment can provide irradiation dose rate ranges from 1E-5 to 1E-4 dpa per operating year. The residual radioactivity is also calculated for regular maintenance work. These results give the basic reference for the experimental design.

  11. High energy neutron treatment for pelvic cancers: study stopped because of increased mortality.

    PubMed Central

    Errington, R D; Ashby, D; Gore, S M; Abrams, K R; Myint, S; Bonnett, D E; Blake, S W; Saxton, T E

    1991-01-01

    OBJECTIVE--To compare high energy fast neutron treatment with conventional megavoltage x ray treatment in the management of locally advanced pelvic carcinomas (of the cervix, bladder, prostate, and rectum). DESIGN--Randomised study from February 1986; randomisation to neutron treatment or photon treatment was unstratified and in the ratio of 3 to 1 until January 1988, when randomisation was in the ratio 1 to 1 and stratified by site of tumour. SETTING--Mersey regional radiotherapy centre at Clatterbridge Hospital, Wirral. PATIENTS--151 patients with locally advanced, non-metastatic pelvic cancer (27 cervical, 69 of the bladder, seven prostatic, and 48 of the rectum). INTERVENTION--Randomisation to neutron treatment was stopped in February 1990. MAIN OUTCOME MEASURES--Patient survival and causes of death in relation to the development of metastatic disease and treatment related morbidity. RESULTS--In the first phase of the trial 42 patients were randomised to neutron treatment and 14 to photon treatment, and in the second phase 48 to neutron treatment and 47 to photon treatment. The relative risk of mortality for photons compared with neutrons was 0.66 (95% confidence interval 0.40 to 1.10) after adjustment for site of tumour and other important prognostic factors. Short term and long term complications were similar in both groups. CONCLUSIONS--The trial was stopped because of the increased mortality in patients with cancer of the cervix, bladder, or rectum treated with neutrons. PMID:1903663

  12. Track Structure Model for Radial Distributions of Electron Spectra and Event Spectra from High-Energy Ions

    NASA Technical Reports Server (NTRS)

    Cucinotta, F. A.; Katz, R.; Wilson, J. W.

    1998-01-01

    An analytic method is described for evaluating the average radial electron spectrum and the radial and total frequency-event spectrum for high-energy ions. For high-energy ions, indirect events make important contributions to frequency-event spectra. The method used for evaluating indirect events is to fold the radial electron spectrum with measured frequency-event spectrum for photons or electrons. The contribution from direct events is treated using a spatially restricted linear energy transfer (LET). We find that high-energy heavy ions have a significantly reduced frequency-averaged final energy (yF) compared to LET, while relativistic protons have a significantly increased yF and dose-averaged lineal energy (yD) for typical site sizes used in tissue equivalent proportional counters. Such differences represent important factors in evaluating event spectra with laboratory beams, in space- flight, or in atmospheric radiation studies and in validation of radiation transport codes. The inadequacy of LET as descriptor because of deviations in values of physical quantities, such as track width, secondary electron spectrum, and yD for ions of identical LET is also discussed.

  13. Superconducting gamma and fast-neutron spectrometers with high energy resolution

    DOEpatents

    Friedrich, Stephan; , Niedermayr, Thomas R.; Labov, Simon E.

    2008-11-04

    Superconducting Gamma-ray and fast-neutron spectrometers with very high energy resolution operated at very low temperatures are provided. The sensor consists of a bulk absorber and a superconducting thermometer weakly coupled to a cold reservoir, and determines the energy of the incident particle from the rise in temperature upon absorption. A superconducting film operated at the transition between its superconducting and its normal state is used as the thermometer, and sensor operation at reservoir temperatures around 0.1 K reduces thermal fluctuations and thus enables very high energy resolution. Depending on the choice of absorber material, the spectrometer can be configured either as a Gamma-spectrometer or as a fast-neutron spectrometer.

  14. Examination of level density prescriptions for the interpretation of high-energy γ -ray spectra

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Srijit; Pandit, Deepak; Dey, Balaram; Mondal, Debasish; Mukhopadhyay, S.; Pal, Surajit; De, A.; Banerjee, S. R.

    2014-11-01

    High-energy γ -ray spectra measured by our group involving the compound nuclei (CN) 63Cu at excitation energy E*˜36 MeV with average angular momentum J =12 -17 ℏ , 97Tc at E*˜29 -50 MeV with J =12 -14 ℏ , 113Sb at E*=109 and 121 MeV with J =49 -59 ℏ , and 201Tl at E*=39.5 and 47.5 MeV with J =18 -24 ℏ have been analyzed utilizing the level density prescriptions of (i) Ignatyuk, Smirenkin, and Tishin (IST), (ii) Budtz-Jorgensen and Knitter (BJK), and (iii) Kataria, Ramamurthy, and Kapoor (KRK). These three prescriptions have been tested for the correct statistical model description of high-energy γ rays in the light of extracting the giant dipole resonance (GDR) parameters at low excitation energy and spin where shell effects might play an important role, as well as at high excitation energy where shell effects have melted. Interestingly, only the IST level density prescription could explain the high-energy γ -ray spectra with reasonable GDR parameters for all four nuclei.

  15. Neutron-induced electronic failures around a high-energy linear accelerator.

    PubMed

    Kry, Stephen F; Johnson, Jennifer L; White, R Allen; Howell, Rebecca M; Kudchadker, Rajat J; Gillin, Michael T

    2011-01-01

    After a new in-vault CT-on-rails system repeatedly malfunctioned following use of a high-energy radiotherapy beam, we investigated the presence and impact of neutron radiation on this electronic system, as well as neutron shielding options. We first determined the CT scanner's failure rate as a function of the number of 18 MV monitor units (MUs) delivered. We then re-examined the failure rate with both 2.7-cm-thick and 7.6-cm-thick borated polyethylene (BPE) covering the linac head for neutron shielding. To further examine shielding options, as well as to explore which neutrons were relevant to the scanner failure, Monte Carlo simulations were used to calculate the neutron fluence and spectrum in the bore of the CT scanner. Simulations included BPE covering the CT scanner itself as well as covering the linac head. We found that the CT scanner had a 57% chance of failure after the delivery of 200 MUs. While the addition of neutron shielding to the accelerator head reduced this risk of failure, the benefit was minimal and even 7.6 cm of BPE was still associated with a 29% chance of failure after the delivery of 200 MU. This shielding benefit was achieved regardless of whether the linac head or CT scanner was shielded. Additionally, it was determined that fast neutrons were primarily responsible for the electronic failures. As illustrated by the CT-on-rails system in the current study, physicists should be aware that electronic systems may be highly sensitive to neutron radiation. Medical physicists should therefore monitor electronic systems that have not been evaluated for potential neutron sensitivity. This is particularly relevant as electronics are increasingly common in the therapy vault and newer electronic systems may exhibit increased sensitivity.

  16. Neutron-induced electronic failures around a high-energy linear accelerator

    SciTech Connect

    Kry, Stephen F.; Johnson, Jennifer L.; White, R. Allen; Howell, Rebecca M.; Kudchadker, Rajat J.; Gillin, Michael T.

    2011-01-15

    Purpose: After a new in-vault CT-on-rails system repeatedly malfunctioned following use of a high-energy radiotherapy beam, we investigated the presence and impact of neutron radiation on this electronic system, as well as neutron shielding options. Methods: We first determined the CT scanner's failure rate as a function of the number of 18 MV monitor units (MUs) delivered. We then re-examined the failure rate with both 2.7-cm-thick and 7.6-cm-thick borated polyethylene (BPE) covering the linac head for neutron shielding. To further examine shielding options, as well as to explore which neutrons were relevant to the scanner failure, Monte Carlo simulations were used to calculate the neutron fluence and spectrum in the bore of the CT scanner. Simulations included BPE covering the CT scanner itself as well as covering the linac head. Results: We found that the CT scanner had a 57% chance of failure after the delivery of 200 MUs. While the addition of neutron shielding to the accelerator head reduced this risk of failure, the benefit was minimal and even 7.6 cm of BPE was still associated with a 29% chance of failure after the delivery of 200 MU. This shielding benefit was achieved regardless of whether the linac head or CT scanner was shielded. Additionally, it was determined that fast neutrons were primarily responsible for the electronic failures. Conclusions: As illustrated by the CT-on-rails system in the current study, physicists should be aware that electronic systems may be highly sensitive to neutron radiation. Medical physicists should therefore monitor electronic systems that have not been evaluated for potential neutron sensitivity. This is particularly relevant as electronics are increasingly common in the therapy vault and newer electronic systems may exhibit increased sensitivity.

  17. High-energy response of the PRESCILA and WENDI-II neutron rem meters.

    PubMed

    Olsher, Richard H; McLean, Thomas D

    2008-01-01

    WENDI-II was designed at the Los Alamos National Laboratory (LANL) specifically as a wide-range rem meter, suitable for applications at particle accelerators, with response extension to 5 GeV. PRESCILA was also designed at LANL, mainly as a lightweight alternative to traditional rem meters, but has shown excellent response characteristics above 20 MeV. This Note summarises measurements performed over a span of 4 y to characterise the high-energy neutron response (>20 MeV) of these meters to several hundred million electron volts. High-energy quasi-monoenergetic beams utilised as part of this study were produced by the cyclotron facilities at the Université Catholique de Louvain (33 and 60 MeV) and the T. Svedberg Laboratory ( 46, 95, 143 and 173 MeV). In addition, measurements were also conducted at the Los Alamos Neutron Science Center, 800 MeV spallation neutron source, in broad energy fields with an average energy of 345 MeV. For the sake of completeness, data collected between 2.5 and 19 MeV in monoenergetic neutron fields at the German Physikalisch-Technische Bundesanstalt (PTB) facility are also included in this study.

  18. The silicon photomultipliers for inelastic neutron scattering at high energy transfers

    NASA Astrophysics Data System (ADS)

    Pietropaolo, Antonino

    2010-01-01

    The silicon photomultiplier (SiPM) is a photo sensor of recent technology. It is mostly used in particle physics, for example in the detection of minimum ionizing particles and/or Cherenkov radiation. Its performance is comparable to that of photomultiplier tubes (PMTs), but with advantages in terms of reduced volume and magnetic field insensitivity. In the present study, the performance of a SiPM as a readout for a γ-ray detector made of a yttrium-aluminum-perovskite (YAP) scintillation crystal is assessed for use in time of flight inelastic neutron spectroscopy at high energy transfers. This was done by performing explorative measurements at the Italian Neutron Experimental Station (INES) beam line at the ISIS spallation neutron source. The measurements, carried out in the so-called resonance detector (RD) configuration, demonstrate the suitability of the SiPM for this kind of application.

  19. Magnetized neutron stars as gamma-ray bursters - Detection rates at high energies

    NASA Technical Reports Server (NTRS)

    Meszaros, P.; Bagoly, Z.; Riffert, H.

    1989-01-01

    Detailed calculations of the escape of high-energy gamma-rays from the dipolar magnetosphere of general relativistic neutron star models are used to model the detection rate of bursters at high photon energies between 0.3 and 10 MeV. This analysis shows the SMM detection rates to be compatible with a magnetized neutron star origin, with a distribution of magnetic field strengths extending at least up to about 4 x 10 to the 12th G, as expected if the (20-60) keV features reported from Konus and Ginga measurements are interpreted as cyclotron lines. Additional implications are discussed for the emission geometry and the neutron star radius.

  20. Sources of High-Energy Emission in the Green Pea Galaxies: New Constraints from Magellan Spectra

    NASA Astrophysics Data System (ADS)

    Carroll, Derek Alexander

    2016-01-01

    The recently discovered Green Pea galaxies display extreme starburst activity and may be some of the only possible Lyman continuum emitting galaxies at low redshift. Green Peas are characterized by their unusually high [O III]/[O II] ratios, similar to the ratios observed in high-redshift galaxies. In addition, the presence of the high-energy He II 4686 line shows that the Green Peas are highly ionized. However, the origin of the He II emission in the Green Peas, and many other starburst galaxies, is still an open question. We analyze IMACS and MagE spectra from the Magellan telescopes in order to evaluate the most probable cause of this He II emission. We also analyze other properties like dust content, temperature and density, and kinematic components. Our IMACS spectra show no Wolf-Rayet (WR) features. We set upper limits on the WR populations in our sample and conclude that Wolf-Rayet stars are not a likely candidate for the He II emission. With deeper MagE spectra we investigate energetic shocks as a possible source of the He II, and move one step closer to uncovering the origin of high-energy photons in these unique starbursts.

  1. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    SciTech Connect

    Aloisio, R.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate X{sub max}(E) and dispersion σ(X{sub max}) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ∼ E{sup -γ} with γ∼ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ∼ 5Z× 10{sup 18} eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ∼ E{sup -2.7}). In this sense, at the ankle E{sub A}≈ 5× 10{sup 18} eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  2. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

    NASA Astrophysics Data System (ADS)

    Aloisio, R.; Berezinsky, V.; Blasi, P.

    2014-10-01

    We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate Xmax(E) and dispersion σ(Xmax) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ~ E-γ with γ~ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ~ 5Z× 1018 eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ~ E-2.7). In this sense, at the ankle EA≈ 5× 1018 eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

  3. Determination of neutron energy spectra inside a water phantom irradiated by 64 MeV neutrons.

    PubMed

    Herbert, M S; Brooks, F D; Allie, M S; Buffler, A; Nchodu, M R; Makupula, S A; Jones, D T L; Langen, K M

    2007-01-01

    A NE230 deuterated liquid scintillator detector (25 mm diameter x 25 mm) has been used to investigate neutron energy spectra as a function of position in a water phantom under irradiation by a quasi-monoenergetic 64 MeV neutron beam. Neutron energy spectra are obtained from measurements of pulse height spectra by the NE230 detector using the Bayesian unfolding code MAXED. The experimentally measured energy spectra are compared with spectra calculated by Monte Carlo simulation using the code MCNPX.

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

    SciTech Connect

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

    2005-12-14

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

  5. Prompt Fission Neutron Spectra of Actinides

    SciTech Connect

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

    2016-01-01

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

  6. COMPTEL measurements of the omnidirectional high-energy neutron flux in near-earth orbit.

    PubMed

    Morris, D J; Aarts, H; Bennett, K; Lockwood, J A; McConnell, M L; Ryan, J M; Schonfelder, V; Steinle, H; Weidenspointner, G

    1998-01-01

    On four occasions, twice in 1991 (near solar maximum) and twice in 1994 (near solar minimum), one COMPTEL D1 detector module was used as an omnidirectional detector to measure the high-energy (> 12.8 MeV) neutron flux near an altitude of 450 km. The D1 modules are cylindrical, with radius 13.8 cm and depth 8 cm, and are filled with liquid scintillator (NE213A). The combined flux measurements can be fit reasonably well by a product of the Mt. Washington neutron monitor rate, a linear function in the spacecraft geocenter zenith angle, and an exponential function of the vertical geomagnetic cutoff rigidity in which the coefficient of the rigidity is a linear function of the neutron monitor rate. When pointed at the nadir, the flux is consistent with that expected from the atmospheric neutron albedo alone. When pointed at the zenith the flux is reduced by a factor of about 0.54. Thus the production of secondary neutrons in the massive (16000 kg) Compton Gamma-Ray Observatory spacecraft is negligible. Rather, the mass of the spacecraft provides shielding from the earth albedo.

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

    SciTech Connect

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

    2014-08-15

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

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

    NASA Technical Reports Server (NTRS)

    Drake, Darrell

    1993-01-01

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

  9. The 12B counter: an active dosemeter for high-energy neutrons.

    PubMed

    Leuschner, A

    2005-01-01

    High-energy accelerators can produce strong time-structured radiation fields. Such dose shots are generated at linear machines with low duty cycles as well as at circular machines when complete fills are instantaneously lost. The main dose component behind thick shielding is due to high-energy neutrons occurring at that time structure. Dosemeters based on Geiger-Mueller tubes or proportional counters fail here completely. The 12B counter, a novel dosemeter made of a plastic scintillator using carbon activation for event-like exposure, has been introduced. High-energy neutrons activate the carbon nuclei by three inelastic reactions. The decay patterns with half-lives between 20 ms and 20 min can be exploited depending on the time structure of the radiation field. The response of the 12B counter was measured along with some other dosemeters, both active and passive, in the radiation field behind the lateral concrete shielding of a 7.5 GeV proton transfer line.

  10. Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system

    DOEpatents

    Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

    2013-02-12

    A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

  11. Apparatus, Method and Program Storage Device for Determining High-Energy Neutron/Ion Transport to a Target of Interest

    NASA Technical Reports Server (NTRS)

    Wilson, John W. (Inventor); Tripathi, Ram K. (Inventor); Badavi, Francis F. (Inventor); Cucinotta, Francis A. (Inventor)

    2012-01-01

    An apparatus, method and program storage device for determining high-energy neutron/ion transport to a target of interest. Boundaries are defined for calculation of a high-energy neutron/ion transport to a target of interest; the high-energy neutron/ion transport to the target of interest is calculated using numerical procedures selected to reduce local truncation error by including higher order terms and to allow absolute control of propagated error by ensuring truncation error is third order in step size, and using scaling procedures for flux coupling terms modified to improve computed results by adding a scaling factor to terms describing production of j-particles from collisions of k-particles; and the calculated high-energy neutron/ion transport is provided to modeling modules to control an effective radiation dose at the target of interest.

  12. BNCT of skin tumors using the high-energy D-T neutrons.

    PubMed

    Masoudi, S Farhad; Rasouli, Fatemeh S; Ghasemi, Marjan

    2017-04-01

    Owing to the continuing need for providing improved and universally accepted facilities to be used in radiation therapies, a number of recently published BNCT-related studies have focused on investigating appropriate neutron sources as alternatives for nuclear reactors. Of special interest are D-T neutron generators, which theoretically have shown the potential to be utilized as neutron sources for BNCT of deep-seated tumors. This work is devoted to investigate the feasibility of using the high-energy neutrons emitted from these generators for treatment of surface tumors, especially skin. Using a set of MCNPX simulations, the D-T neutrons are passed through an optimized arrangement of materials to slow-down toward the desired energy range, and to remove the neutron and gamma contamination considering the IAEA recommended criteria, especially determined for pre-clinical survey for treatment of surface tumors. By assessment with these parameters, it is shown that the designed beam, corresponding to a configuration composed of natural uranium as neutron multiplier, D2O as moderator, Pb as reflector, Bi as gamma filter, and polyethylene and BeO as collimators provides high-intensity of desired neutrons, and low-background doses as well. It was found that an appropriate material for collimator, if accompanied with an optimized geometry, is an important parameter for keeping the undesired components to the recommended level. A typical simulated phantom, subjected to the irradiation of the designed spectrum, is used to study the performance of the resultant beam in shallow tissue. For an arbitrary chosen (10)B concentration, the evaluated depth-dose curves show that the proposed configuration establishes acceptable agreement between the appropriate neutron intensity and penetration to desired depth in tissue in a reasonable treatment time of about 25-38min. Considering the simulations carried out, the total dose delivered to the tumor is expected to be of about 4.2 times

  13. Disk-accreting magnetic neutron stars as high-energy particle accelerators

    NASA Technical Reports Server (NTRS)

    Hamilton, Russell J.; Lamb, Frederick K.; Miller, M. Coleman

    1994-01-01

    Interaction of an accretion disk with the magnetic field of a neutron star produces large electromotive forces, which drive large conduction currents in the disk-magnetosphere-star circuit. Here we argue that such large conduction currents will cause microscopic and macroscopic instabilities in the magnetosphere. If the minimum plasma density in the magnetosphere is relatively low is less than or aproximately 10(exp 9)/cu cm, current-driven micro-instabilities may cause relativistic double layers to form, producing voltage differences in excess of 10(exp 12) V and accelerating charged particles to very high energies. If instead the plasma density is higher (is greater than or approximately = 10(exp 9)/cu cm, twisting of the stellar magnetic field is likely to cause magnetic field reconnection. This reconnection will be relativistic, accelerating plasma in the magnetosphere to relativistic speeds and a small fraction of particles to very high energies. Interaction of these high-energy particles with X-rays, gamma-rays, and accreting plasma may produce detectable high-energy radiation.

  14. Disk-accreting magnetic neutron stars as high-energy particle accelerators

    NASA Technical Reports Server (NTRS)

    Hamilton, Russell J.; Lamb, Frederick K.; Miller, M. Coleman

    1994-01-01

    Interaction of an accretion disk with the magnetic field of a neutron star produces large electromotive forces, which drive large conduction currents in the disk-magnetosphere-star circuit. Here we argue that such large conduction currents will cause microscopic and macroscopic instabilities in the magnetosphere. If the minimum plasma density in the magnetosphere is relatively low is less than or aproximately 10(exp 9)/cu cm, current-driven micro-instabilities may cause relativistic double layers to form, producing voltage differences in excess of 10(exp 12) V and accelerating charged particles to very high energies. If instead the plasma density is higher (is greater than or approximately = 10(exp 9)/cu cm, twisting of the stellar magnetic field is likely to cause magnetic field reconnection. This reconnection will be relativistic, accelerating plasma in the magnetosphere to relativistic speeds and a small fraction of particles to very high energies. Interaction of these high-energy particles with X-rays, gamma-rays, and accreting plasma may produce detectable high-energy radiation.

  15. The Fascinating High-Energy World of Neutron Stars and Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Safi-Harb, Samar

    2006-06-01

    The past few years have witnessed a fast growth in the high-energy astrophysics community in Canada, thanks to new opportunities including the University Faculty Award (UFA) program introduced by the Natural Sciences and Engineering Research Council of Canada (NSERC) to appoint promising female researchers to faculty positions in science and engineering. As a UFA fellow at the University of Manitoba, I have had the unique opportunity to contribute to the launch of a new astronomy program in the department of Physics (renamed to Physics and Astronomy). My research focuses on observational studies of neutron stars, pulsar wind nebulae, and supernova remnants. The study of these exotic objects helps address the physics of the extreme and probe some of the most energetic events in the Universe. I will highlight exciting discoveries in this field and some of the questions to be addressed with current and future high-energy missions.

  16. Characterizing high energy spectra of NIF ignition Hohlraums using a differentially filtered high energy multipinhole x-ray imager.

    PubMed

    Park, Hye-Sook; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Robey, H F; Thomas, C A

    2010-10-01

    Understanding hot electron distributions generated inside Hohlraums is important to the national ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with target materials. We used an array of 18 pinholes with four independent filter combinations to image entire Hohlraums with a magnification of 0.87× during the Hohlraum energetics campaign on NIF. Comparing our results with Hohlraum simulations indicates that the characteristic 10-40 keV hot electrons are mainly generated from backscattered laser-plasma interactions rather than from Hohlraum hydrodynamics.

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

    PubMed

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

    2009-09-01

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

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

    PubMed Central

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

    2009-01-01

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

  19. Comparison of neutron and high-energy X-ray dual-beam radiography for air cargo inspection.

    PubMed

    Liu, Y; Sowerby, B D; Tickner, J R

    2008-04-01

    Dual-beam radiography techniques utilising various combinations of high-energy X-rays and neutrons are attractive for screening bulk cargo for contraband such as narcotics and explosives. Dual-beam radiography is an important enhancement to conventional single-beam X-ray radiography systems in that it provides additional information on the composition of the object being imaged. By comparing the attenuations of transmitted dual high-energy beams, it is possible to build a 2D image, colour coded to indicate material. Only high-energy X-rays, gamma-rays and neutrons have the required penetration to screen cargo containers. This paper reviews recent developments and applications of dual-beam radiography for air cargo inspection. These developments include dual high-energy X-ray techniques as well as fast neutron and gamma-ray (or X-ray) radiography systems. High-energy X-ray systems have the advantage of generally better penetration than neutron systems, depending on the material being interrogated. However, neutron systems have the advantage of much better sensitivity to material composition compared to dual high-energy X-ray techniques. In particular, fast neutron radiography offers the potential to discriminate between various classes of organic material, unlike dual energy X-ray techniques that realistically only offer the ability to discriminate between organic and metal objects.

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

    NASA Astrophysics Data System (ADS)

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

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

  1. 90° Neutron emission from high energy protons and lead ions on a thin lead target

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Birattari, C.; Foglio Para, A.; Mitaroff, A.; Silari, M.; Ulrici, L.

    2002-01-01

    The neutron emission from a relatively thin lead target bombarded by beams of high energy protons/pions and lead ions was measured at CERN in one of the secondary beam lines of the Super Proton Synchrotron for radiation protection and shielding calculations. Measurements were performed with three different beams: 208Pb 82+ lead ions at 40 GeV/ c per nucleon and 158 GeV/ c per nucleon, and 40 GeV/ c mixed protons/pions. The neutron yield and spectral fluence per incident ion on target were measured at 90° with respect to beam direction. Monte-Carlo simulations with the FLUKA code were performed for the case of protons and pions and the results found in good agreement with the experimental data. A comparison between simulations and experiment for protons, pions and lead ions have shown that—for such high energy heavy ion beams—a reasonable estimate can be carried out by scaling the result of a Monte-Carlo calculation for protons by the projectile mass number to the power of 0.80-0.84.

  2. Characterization of extended range Bonner Sphere Spectrometers in the CERF high-energy broad neutron field at CERN

    NASA Astrophysics Data System (ADS)

    Agosteo, S.; Bedogni, R.; Caresana, M.; Charitonidis, N.; Chiti, M.; Esposito, A.; Ferrarini, M.; Severino, C.; Silari, M.

    2012-12-01

    controlled workplace field. The CERF (CERN-EU high-energy reference field) facility is a unique example of such a field, where a number of experimental campaigns and Monte Carlo simulations have been performed over the past years. With the aim of performing this kind of workplace performance test, four different ERBSS with different degrees of validation, operated by three groups (CERN, INFN-LNF and Politecnico of Milano), were exposed in two fixed positions at CERF. Using different unfolding codes (MAXED, GRAVEL, FRUIT and FRUIT SGM), the experimental data were analyzed to provide the neutron spectra and the related dosimetric quantities. The results allow assessing the overall performance of each ERBSS and of the unfolding codes, as well as comparing the performance of three ERRCs when used in a neutron field with energy distribution different from the calibration spectrum.

  3. Spectra and Neutron Dosimetry Inside a PET Cyclotron Vault Room

    SciTech Connect

    Vega-Carrillo, Hector Rene; Mendez, Roberto; Iniguez, Maria Pilar; Marti-Climent, Joseph; Penuelas, Ivan; Barquero, Raquel

    2006-09-08

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

  4. Tolerance of the human spinal cord to high energy p(66)Be(49) neutrons

    SciTech Connect

    Cohen, L.; Ten Haken, R.K.; Mansell, J.; Yalavarthi, S.D.; Hendrickson, F.R.; Awschalom, M.

    1985-04-01

    The risk of post irradiation myelopathy was evaluated in 76 patients followed for 1-5 years after neutron irradiation of the cervical and thoracic regions. No overt myelopathy was observed. Forty-six patients received doses (central cord dose) in excess of 10 Gy, 9 received doses in excess of 12 Gy, and 5 received doses between 13 and 17 Gy, all without any evidence of spinal cord injury. A review of available literature revealed a total of 14 patients with myelopathy, 13 of whom received doses in excess of 13 Gy delivered with relatively low energy neutrons generated by the deuteron + beryllium reaction. It is concluded from these studies that the tolerance limit for the human spinal cord irradiated with high energy (p(66)Be(49)) neutrons is close to 15 Gy, above which the risk of cord injury becomes significant. Central cord doses of 13 Gy or less appear to be well tolerated with little, if any, risk of myelopathy. These conclusions are valid for a treatment time of 4 weeks or more with two or more fractions per week (9 or more fractions). The RBE for the human spinal cord irradiated under the above conditions compared with conventionally fractionated photon therapy does not exceed 4.0.

  5. New estimation method of neutron skyshine for a high-energy particle accelerator

    NASA Astrophysics Data System (ADS)

    Oh, Joo-Hee; Jung, Nam-Suk; Lee, Hee-Seock; Ko, Seung-Kook

    2016-09-01

    A skyshine is the dominant component of the prompt radiation at off-site. Several experimental studies have been done to estimate the neutron skyshine at a few accelerator facilities. In this work, the neutron transports from a source place to off-site location were simulated using the Monte Carlo codes, FLUKA and PHITS. The transport paths were classified as skyshine, direct (transport), groundshine and multiple-shine to understand the contribution of each path and to develop a general evaluation method. The effect of each path was estimated in the view of the dose at far locations. The neutron dose was calculated using the neutron energy spectra obtained from each detector placed up to a maximum of 1 km from the accelerator. The highest altitude of the sky region in this simulation was set as 2 km from the floor of the accelerator facility. The initial model of this study was the 10 GeV electron accelerator, PAL-XFEL. Different compositions and densities of air, soil and ordinary concrete were applied in this calculation, and their dependences were reviewed. The estimation method used in this study was compared with the well-known methods suggested by Rindi, Stevenson and Stepleton, and also with the simple code, SHINE3. The results obtained using this method agreed well with those using Rindi's formula.

  6. Calibration of a Bonner sphere extension (BSE) for high-energy neutron spectrometry

    PubMed Central

    Howell, R.M.; Burgett, E.A.; Wiegel, B.; Hertel, N.E.

    2011-01-01

    In a recent work, we constructed modular multisphere system which expands upon the design of an existing, commercially available Bonner sphere system by adding concentric shells of copper, tungsten, or lead. Our modular multisphere system is referred to as the Bonner Sphere Extension (BSE). The BSE was tested in a high energy neutron beam (thermal to 800 MeV) at Los Alamos Neutron Science Center and provided improvement in the measurement of the neutron spectrum in the energy regions above 20 MeV when compared to the standard BSS (Burgett, 2008 and Howell et al., 2009). However, when the initial test of the system was carried-out at LANSCE, the BSE had not yet been calibrated. Therefore the objective of the present study was to perform calibration measurements. These calibration measurements were carried out using monoenergetic neutron ISO 8529-1 reference beams at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. The following monoenergetic reference beams were used for these experiments: 14.8 MeV, 1.2 MeV, 565 keV, and 144 keV. Response functions for the BSE were calculated using the Monte Carlo N-Particle Code, eXtended (MCNPX). The percent difference between the measured and calculated responses was calculated for each sphere and energy. The difference between measured and calculated responses for individual spheres ranged between 7.9 % and 16.7 % and the arithmetic mean for all spheres was (10.9 ± 1.8) %. These sphere specific correction factors will be applied for all future measurements carried-out with the BSE. PMID:22888283

  7. Arrangement of high-energy neutron irradiation field and shielding experiment using 4 m concrete at KENS.

    PubMed

    Nakao, N; Yashima, H; Kawai, M; Oishi, K; Nakashima, H; Masumoto, K; Matsumura, H; Sasaki, S; Numajiri, M; Sanami, T; Wang, Q; Toyoda, A; Takahashi, K; Iijima, K; Eda, K; Ban, S; Hirayama, H; Muto, S; Nunomiya, T; Yonai, S; Rasolonjatovo, D R H; Terunuma, K; Yamauchi, K; Sarkar, P K; Kim, E; Nakamura, T; Maruhashi, A

    2005-01-01

    An irradiation field of high-energy neutrons produced in the forward direction from a thick tungsten target bombarded by 500 MeV protons was arranged at the KENS spallation neutron source facility. In this facility, shielding experiment was performed with an ordinary concrete shield of 4 m thickness assembled in the irradiation room, 2.5 m downstream from the target centre. Activation detectors of bismuth, aluminium, indium and gold were inserted into eight slots inside the shield and attenuations of neutron reaction rates were obtained by measurements of gamma-rays from the activation detectors. A MARS14 Monte Carlo simulation was also performed down to thermal energy, and comparisons between the calculations and measurements show agreements within a factor of 3. This neutron field is useful for studies of shielding, activation and radiation damage of materials for high-energy neutrons, and experimental data are useful to check the accuracies of the transmission and activation calculation codes.

  8. Neutron therapy facility at the Institute of High Energy Physics, Academia Sinica

    SciTech Connect

    Zhu, Y.C.

    1983-12-01

    The 10 MeV proton linac which was designed as preinjector for the Beijing 50 GeV Proton Synchrotron (BPS) was completed by the end of 1982. Because of the economic readjustment in the People's Republic of China the BPS project was cancelled. Then, the Institute of High Energy Physics decided to increase the energy of the linac from 10 MeV to 35.5 MeV. This increase will take place using the primary five megawatts RF system of the 10 MeV linac. This 35.5 MeV proton linac will be used for research in radiomedicine and radiobiology in general and in particular for research in fast neutron therapy and radiopharmaceutical production. This project has been approved by the Academia Sinica.

  9. Neutron Scattering Study of the High-energy Graphitic Phonons in Superconducting CaC6

    SciTech Connect

    Dean, M.P.; Walters, A.C.; Howard, C.A.; Weller, T.E.; Calandra, M.; Mauri, F.; Ellerby, M.; Saxena, S.S.; Ivanov, A.; McMorrow, D.F.

    2010-07-28

    We present the results of a neutron scattering study of the high energy phonons in the superconducting graphite intercalation compound CaC{sub 6}. The study was designed to address hitherto unexplored aspects of the lattice dynamics in CaC{sub 6}, and in particular any renormalization of the out-of-plane and in-plane graphitic phonon modes. We present a detailed comparison between the data and the results of density functional theory (DFT). A description is given of the analysis methods developed to account for the highly-textured nature of the samples. The DFT calculations are shown to provide a good description of the general features of the experimental data. This is significant in light of a number of striking disagreements in the literature between other experiments and DFT on CaC{sub 6}. The results presented here demonstrate that the disagreements are not due to any large inaccuracies in the calculated phonon frequencies.

  10. Neutron scattering study of the high-energy graphitic phonons in sperconducting CaC6

    SciTech Connect

    Dean, M.P.M.; Walters, A.C.; Howard, C.A.; Weller, T.E.; Calandra, M.; Mauri, F.; Ellerby, M.; Saxena, S.S.; Ivanov, A.; McMorrow, D.F.

    2010-07-28

    We present the results of a neutron scattering study of the high-energy phonons in the superconducting graphite intercalation compound CaC{sub 6} . The study was designed to address hitherto unexplored aspects of the lattice dynamics in CaC{sub 6} , and, in particular, any renormalization of the out-of-plane and in-plane graphitic phonon modes. We present a detailed comparison between the data and the results of density-functional theory (DFT). A description is given of the analysis methods developed to account for the highly textured nature of the samples. The DFT calculations are shown to provide a good description of the general features of the experimental data. This is significant in light of a number of striking disagreements in the literature between other experiments and DFT on CaC{sub 6} . The results presented here demonstrate that the disagreements are not due to any large inaccuracies in the calculated phonon frequencies.

  11. The origin of thermal component in the transverse momentum spectra in high energy hadronic processes

    DOE PAGES

    Bylinkin, Alexander A.; Kharzeev, Dmitri E.; Rostovtsev, Andrei A.

    2014-12-15

    The transverse momentum spectra of hadrons produced in high energy collisions can be decomposed into two components: the exponential ("thermal") and the power ("hard") ones. Recently, the H1 Collaboration has discovered that the relative strength of these two components in Deep Inelastic Scattering (DIS) depends drastically upon the global structure of the event - namely, the exponential component is absent in the diffractive events characterized by a rapidity gap. We discuss the possible origin of this effect and speculate that it is linked to confinement. Specifically, we argue that the thermal component is due to the effective event horizon introducedmore » by the confining string, in analogy to the Hawking-Unruh effect. In diffractive events, the t-channel exchange is color-singlet and there is no fragmenting string - so the thermal component is absent. The slope of the soft component of the hadron spectrum in this picture is determined by the saturation momentum that drives the deceleration in the color field, and thus the Hawking-Unruh temperature. We analyze the data on non-diffractive pp collisions and find that the slope of the thermal component of the hadron spectrum is indeed proportional to the saturation momentum.« less

  12. The origin of thermal component in the transverse momentum spectra in high energy hadronic processes

    SciTech Connect

    Bylinkin, Alexander A.; Kharzeev, Dmitri E.; Rostovtsev, Andrei A.

    2014-12-15

    The transverse momentum spectra of hadrons produced in high energy collisions can be decomposed into two components: the exponential ("thermal") and the power ("hard") ones. Recently, the H1 Collaboration has discovered that the relative strength of these two components in Deep Inelastic Scattering (DIS) depends drastically upon the global structure of the event - namely, the exponential component is absent in the diffractive events characterized by a rapidity gap. We discuss the possible origin of this effect and speculate that it is linked to confinement. Specifically, we argue that the thermal component is due to the effective event horizon introduced by the confining string, in analogy to the Hawking-Unruh effect. In diffractive events, the t-channel exchange is color-singlet and there is no fragmenting string - so the thermal component is absent. The slope of the soft component of the hadron spectrum in this picture is determined by the saturation momentum that drives the deceleration in the color field, and thus the Hawking-Unruh temperature. We analyze the data on non-diffractive pp collisions and find that the slope of the thermal component of the hadron spectrum is indeed proportional to the saturation momentum.

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

    SciTech Connect

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

    2009-01-01

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

  14. Measured Neutron Spectra and Dose Equivalents From a Mevion Single-Room, Passively Scattered Proton System Used for Craniospinal Irradiation.

    PubMed

    Howell, Rebecca M; Burgett, Eric A; Isaacs, Daniel; Price Hedrick, Samantha G; Reilly, Michael P; Rankine, Leith J; Grantham, Kevin K; Perkins, Stephanie; Klein, Eric E

    2016-05-01

    To measure, in the setting of typical passively scattered proton craniospinal irradiation (CSI) treatment, the secondary neutron spectra, and use these spectra to calculate dose equivalents for both internal and external neutrons delivered via a Mevion single-room compact proton system. Secondary neutron spectra were measured using extended-range Bonner spheres for whole brain, upper spine, and lower spine proton fields. The detector used can discriminate neutrons over the entire range of the energy spectrum encountered in proton therapy. To separately assess internally and externally generated neutrons, each of the fields was delivered with and without a phantom. Average neutron energy, total neutron fluence, and ambient dose equivalent [H* (10)] were calculated for each spectrum. Neutron dose equivalents as a function of depth were estimated by applying published neutron depth-dose data to in-air H* (10) values. For CSI fields, neutron spectra were similar, with a high-energy direct neutron peak, an evaporation peak, a thermal peak, and an intermediate continuum between the evaporation and thermal peaks. Neutrons in the evaporation peak made the largest contribution to dose equivalent. Internal neutrons had a very low to negligible contribution to dose equivalent compared with external neutrons, largely attributed to the measurement location being far outside the primary proton beam. Average energies ranged from 8.6 to 14.5 MeV, whereas fluences ranged from 6.91 × 10(6) to 1.04 × 10(7) n/cm(2)/Gy, and H* (10) ranged from 2.27 to 3.92 mSv/Gy. For CSI treatments delivered with a Mevion single-gantry proton therapy system, we found measured neutron dose was consistent with dose equivalents reported for CSI with other proton beamlines. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  15. Cyclotron Lines in Accreting Neutron Star Spectra

    NASA Astrophysics Data System (ADS)

    Wilms, Jörn; Schönherr, Gabriele; Schmid, Julia; Dauser, Thomas; Kreykenbohm, Ingo

    2009-05-01

    Cyclotron lines are formed through transitions of electrons between discrete Landau levels in the accretion columns of accreting neutron stars with strong (1012 G) magnetic fields. We summarize recent results on the formation of the spectral continuum of such systems, describe recent advances in the modeling of the lines based on a modification of the commonly used Monte Carlo approach, and discuss new results on the dependence of the measured cyclotron line energy from the luminosity of transient neutron star systems. Finally, we show that Simbol-X will be ideally suited to build and improve the observational database of accreting and strongly magnetized neutron stars.

  16. The Effects of Low- and High-Energy Cutoffs on Solar Flare Microwave and Hard X-Ray Spectra

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Oegerle, William (Technical Monitor)

    2002-01-01

    Microwave and hard x-ray spectra provide crucial information about energetic electrons and their environment in solar flares. These spectra are becoming better determined with the Owens Valley Solar Array (OVSA) and the recent launch of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The proposed Frequency Agile Solar Radiotelescope (FASR) promises even greater advances in radio observations of solar flares. Both microwave and hard x-ray spectra are sensitive to cutoffs in the electron distribution function. The determination of the high-energy cutoff from these spectra establishes the highest electron energies produced by the acceleration mechanism, while determination of the low-energy cutoff is crucial to establishing the total energy in accelerated electrons. This paper will show computations of the effects of both high- and low-energy cutoffs on microwave and hard x-ray spectra. The optically thick portion of a microwave spectrum is enhanced and smoothed by a low-energy cutoff, while a hard x-ray spectrum is flattened below the cutoff energy. A high-energy cutoff steepens the microwave spectrum and increases the wavelength at which the spectrum peaks, while the hard x-ray spectrum begins to steepen at photon energies roughly an order of magnitude below the electron cutoff energy. This work discusses how flare microwave and hard x-ray spectra can be analyzed together to determine these electron cutoff energies. This work is supported in part by the NASA Sun-Earth Connection Program.

  17. The Effects of Low- and High-Energy Cutoffs on Solar Flare Microwave and Hard X-Ray Spectra

    NASA Technical Reports Server (NTRS)

    Holman, G. D.; Oegerle, William (Technical Monitor)

    2002-01-01

    Microwave and hard x-ray spectra provide crucial information about energetic electrons and their environment in solar flares. These spectra are becoming better determined with the Owens Valley Solar Array (OVSA) and the recent launch of the Ramaty High Energy Solar Spectroscopic Imager (RHESSI). The proposed Frequency Agile Solar Radiotelescope (FASR) promises even greater advances in radio observations of solar flares. Both microwave and hard x-ray spectra are sensitive to cutoffs in the electron distribution function. The determination of the high-energy cutoff from these spectra establishes the highest electron energies produced by the acceleration mechanism, while determination of the low-energy cutoff is crucial to establishing the total energy in accelerated electrons. This paper will show computations of the effects of both high- and low-energy cutoffs on microwave and hard x-ray spectra. The optically thick portion of a microwave spectrum is enhanced and smoothed by a low-energy cutoff, while a hard x-ray spectrum is flattened below the cutoff energy. A high-energy cutoff steepens the microwave spectrum and increases the wavelength at which the spectrum peaks, while the hard x-ray spectrum begins to steepen at photon energies roughly an order of magnitude below the electron cutoff energy. This work discusses how flare microwave and hard x-ray spectra can be analyzed together to determine these electron cutoff energies. This work is supported in part by the NASA Sun-Earth Connection Program.

  18. Calculating fusion neutron energy spectra from arbitrary reactant distributions

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  19. Development and first flight of the high energy focusing telescope and analysis of spectral features in the isolated neutron star 1E1207.4-5209

    NASA Astrophysics Data System (ADS)

    Chonko, James C.

    Research efforts in this thesis are focused on two areas: (1) the High Energy Focusing Telescope (HEFT), a next-generation, focusing, hard X-ray telescope, and (2) the spectral analysis of the isolated neutron star 1E1207.4-5209. I describe the production, calibration, and flight performance of the High Energy Focusing Telescope (HEFT), a balloon-borne focusing hard X-ray telescope sensitive to X-rays in the 20--70 keV energy band. A number of new technologies were developed and implemented to achieve significant improvements in effective area and angular resolution over previous instruments. HEFT's balloon flight in the Spring of 2005 was highly successful, making HEFT the first focusing hard X-ray instrument to yield scientific results. The thermal emission from isolated neutron stars provides a clean probe of the extreme physical conditions present at the surface and in the interior of neutron stars. In particular, the identification of spectral features in these spectra can be used to determine neutron star parameters, such as temperature, magnetic field, surface chemical composition, and equation of state. The isolated neutron star 1E1207.4-5209 differentiates itself from all other known neutron stars by possessing multiple X-ray absorption lines. We have reanalyzed the 260 ksec XMM-Newton observation and applied more rigorous statistical analysis to the data. We do not find a third and fourth spectral feature as previously reported in 1E1207.4-5209 with our improved analysis, but only the two broad absorption features.

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

    SciTech Connect

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

    2015-06-15

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

  1. Applicability of the two-angle differential method to response measurement of neutron-sensitive devices at the RCNP high-energy neutron facility

    NASA Astrophysics Data System (ADS)

    Masuda, Akihiko; Matsumoto, Tetsuro; Iwamoto, Yosuke; Hagiwara, Masayuki; Satoh, Daiki; Sato, Tatsuhiko; Iwase, Hiroshi; Yashima, Hiroshi; Nakane, Yoshihiro; Nishiyama, Jun; Shima, Tatsushi; Tamii, Atsushi; Hatanaka, Kichiji; Harano, Hideki; Nakamura, Takashi

    2017-03-01

    Quasi-monoenergetic high-energy neutron fields induced by 7Li(p,n) reactions are used for the response evaluation of neutron-sensitive devices. The quasi-monoenergetic high-energy field consists of high-energy monoenergetic peak neutrons and unwanted continuum neutrons down to the low-energy region. A two-angle differential method has been developed to compensate for the effect of the continuum neutrons in the response measurements. In this study, the two-angle differential method was demonstrated for Bonner sphere detectors, which are typical examples of moderator-based neutron-sensitive detectors, to investigate the method's applicability and its dependence on detector characteristics. Experiments were performed under 96-387 MeV quasi-monoenergetic high-energy neutron fields at the Research Center for Nuclear Physics (RCNP), Osaka University. The measurement results for large high-density polyethylene (HDPE) sphere detectors agreed well with Monte Carlo calculations, which verified the adequacy of the two-angle differential method. By contrast, discrepancies were observed in the results for small HDPE sphere detectors and metal-induced sphere detectors. The former indicated that detectors that are particularly sensitive to low-energy neutrons may be affected by penetrating neutrons owing to the geometrical features of the RCNP facility. The latter discrepancy could be consistently explained by a problem in the evaluated cross-section data for the metals used in the calculation. Through those discussions, the adequacy of the two-angle differential method was experimentally verified, and practical suggestions were made pertaining to this method.

  2. The spectra of weakly magnetized neutron stars

    NASA Technical Reports Server (NTRS)

    Fu, Albert; Taam, Ronald E.

    1990-01-01

    The continuum spectrum of a rotating equatorial emitting region on the surface of an accreting neutron star is investigated within the Schwarzschild spacetime. It is found that the dominant general relativistic effect is the increase in apparent emission area from the neutron star surface due to gravitational light bending. For typical neutron star parameters, the apparent area of the accretion belt is remarkably independent of the viewing angle and, hence, the contribution for a boundary layer to the total X-ray luminosity is found to depend only weakly on the inclination angle of the binary system. For a blackbody spectrum in the local rest frame of the emitting surface, the distortion of the spectral shape by longitudinal and transverse Doppler shifts is minimal for neutron stars rotating at periods greater than about 2 ms. It is shown that the failure to detect a blackbody component from the weakly magnetized neutron star surface in some X-ray burst sources during their quiescent state may be related to the presence of temperature variations along the vertical extent of the boundary layer.

  3. Neutron energy spectra of d(49)-Be and p(41)-Be neutron radiotherapy sources.

    PubMed

    Graves, R G; Smathers, J B; Almond, P R; Grant, W H; Otte, V A

    1979-01-01

    Zero-degree neutron energy spectra for the p(41)-Be and d(49)-Be reactions were measured by time-of-flight for neutrons with energies above 1.9 and 1.4 MeV, respectively. Spectral changes resulting from the addition of copper, aluminum, and polyethylene filters to unfiltered beams were determined. Integral yields, average energies, filter material attenuation coefficients, and kerma fractions were computed for these spectra. Calculated spectra for neutron beams filtered by various thicknesses of polyethylene compared favorably with experimental results

  4. On Integral Upper Limits Assuming Power-law Spectra and the Sensitivity in High-energy Astronomy

    NASA Astrophysics Data System (ADS)

    Ahnen, Max L.

    2017-02-01

    The high-energy non-thermal universe is dominated by power-law-like spectra. Therefore, results in high-energy astronomy are often reported as parameters of power-law fits, or, in the case of a non-detection, as an upper limit assuming the underlying unseen spectrum behaves as a power law. In this paper, I demonstrate a simple and powerful one-to-one relation of the integral upper limit in the two-dimensional power-law parameter space into the spectrum parameter space and use this method to unravel the so-far convoluted question of the sensitivity of astroparticle telescopes.

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

    PubMed

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

    2015-05-01

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

  6. Neutron flux spectra in the FFTF In-Reactor Thimble

    SciTech Connect

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

    1982-12-01

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

  7. Workplace characterisation in mixed neutron-gamma fields, specific requirements and available methods at high-energy accelerators.

    PubMed

    Silari, Marco

    2007-01-01

    A good knowledge of the radiation field present outside the shielding of high-energy particle accelerators is very important to be able to select the type of detectors (active and/or passive) to be employed for area monitoring and the type of personal dosemeter required for estimating the doses received by individuals. Around high-energy electron and proton accelerators the radiation field is usually dominated by neutrons and photons, with minor contributions from other charged particles. Under certain circumstances, muon radiation in the forward beam direction may also be present. Neutron dosimetry and spectrometry are of primary importance to characterise the radiation field and thus to correctly evaluate personnel exposure. Starting from the beam parameters important for radiation monitoring, the paper first briefly reviews the stray radiation fields encountered around high-energy accelerators and then addresses the relevant techniques employed for their monitoring. Recent developments to increase the response of neutron measuring devices beyond 10-20 MeV are illustrated. Instruments should be correctly calibrated either in reference monoenergetic radiation fields or in a field similar to the field in which they are used (workplace calibration). The importance of the instrument calibration is discussed and available neutron calibration facilities are briefly reviewed.

  8. High Energy Cosmic Ray Electron Spectra measured from the ATIC Balloon Experiment

    NASA Technical Reports Server (NTRS)

    Chang, J.; Schmidt, W. K. H.; Adams, J. H.; Ahn, H. S.; Bashindzhagyan, G.; Batkov, K. E.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunasingha, R. M.

    2003-01-01

    The Advanced Thin Ionization Calorimeter Balloon Experiment (ATIC) is specifically designed for high energy cosmic ray ion detection. From simulation and a CERN beam test exposure we find that the design consisting of a graphite target and an energy detection device, a totally active calorimeter of BGO scintillator, gives us sufficient information to distinguish electrons from protons up to the TeV energy range. Balloon observations were successfully carried out over Antarctica in both 2000/2001 and 2002/2003 for a total of more than 35 days. This paper presents preliminary results on the spectrum of high energy electrons observed in the first ATIC flight.

  9. Neutron spectra and angular distributions of concrete-moderated neutron calibration fields at JAERI.

    PubMed

    Yoshizawa, M; Tanimura, Y; Saegusa, J; Nemoto, H; Yoshida, M

    2004-01-01

    The Facility of Radiation Standards of Japan Atomic Energy Research Institute has been equipped with concrete-moderated neutron calibration fields as simulated workplace neutron fields. The fields use an 241Am-Be neutron source placed in the narrow space surrounded by concrete bricks, walls and floor. The neutron spectra and the neutron fluence rates of the fields were measured with the Bonner multi-sphere spectrometer system (BMS), spherical recoil-proton proportional counters, and a liquid scintillation counter (NE-213). The results were compared with each other. The reference values of H*(10) were determined from the results of BMS. The angular distributions of neutron fluence were calculated using MCNP-4B2 to obtain the reference values of Hp(10). The calculated results show that the scattered neutrons have a wide range of incident angles. The reference Hp(10) values considered the angular distribution were found to be 10-18% smaller than those without consideration.

  10. Determination of Endpoint Energy and Bremsstrahlung Spectra for High-Energy Radiation-Therapy Beams

    NASA Astrophysics Data System (ADS)

    Landry, Danny Joe

    Few attempts have been made to experimentally determine thick-target bremsstrahlung spectra of megavoltage therapy beams. For spectral studies using the Compton scattering technique, sodium iodine (NaI) detectors with relatively poor energy resolution have been used. Other experimental techniques for determining spectra are generally not suited for a clinical environment with the inherent time and space constraints. To gather more spectral information than previously obtained in the region near the endpoint energy, the use of a high-resolution intrinsic-germanium (Ge) detector was proposed. A response function matrix was determined from experimentally obtained pulse height distributions on the multichannel analyzer. The distributions were for nine various monoenergetic sources between 280 adn 1525 keV. The response function was used to convert the measured pulse height distributions to photon flux spectra using an iterative approximation technique with a computer. Photon flux spectra from the Sagittaire Linear Accelerator were obtained at average-electron endpoint energies of 15, 20, and 25 MeV. Two spectra were measured at the 25 MeV setting; one spectrum was measured along the central axis and one spectrum at 4(DEGREES) off axis. Photon spectra were also obtained for a Van de Graaff generator at the nominal endpoint energies of 2.2, 2.35, and 2.5 MeV. The results for both the linac and the Van de Graaff generator were compared with theoretical spectra and previously measured spectra where available. Also, photon spectra from a Theratron-80 (('60)Co) unit were determined for three field sizes and for a 10 x 10 cm. field with a lucite tray or a 45(DEGREES) wedge in the beam. The resulting spectra were compared to previously measured ('60)Co spectra.

  11. Measurements of liquid and glass structures using in-situ high energy x-ray and neutron scattering

    SciTech Connect

    Weber, Richard; Benmore, C. J.; Skinner, Lawrie; Neuefeind, Joerg C; Tumber, Sonia; Jennings, G; Santodonato, Louis J; Jin, D; Du, Jincheng; Parise, John B

    2013-01-01

    Investigation of high temperature molten materials and their evolution to the amorphous state is often hampered by unwanted reactions with container surfaces. This work used aerodynamic levitation in combination with laser beam heating to study high melting point materials that can form supercooled liquids or glasses. Details of the instruments that are being used at the Advanced Photon Source and the Spallation Neutron Source to study molten oxides with high energy x-ray scattering and neutron diffraction with isotope substitution are presented. Examples of measurements are used to illustrate the use of the instruments. Plans for further development and application of the capabilities are presented.

  12. Neutron emission profiles and energy spectra measurements at JET

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  13. New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions

    NASA Astrophysics Data System (ADS)

    Geslot, B.; Vermeeren, L.; Filliatre, P.; Lopez, A. Legrand; Barbot, L.; Jammes, C.; Bréaud, S.; Oriol, L.; Villard, J.-F.

    2011-03-01

    Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 × 1020 n/cm2. A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.

  14. New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions.

    PubMed

    Geslot, B; Vermeeren, L; Filliatre, P; Lopez, A Legrand; Barbot, L; Jammes, C; Bréaud, S; Oriol, L; Villard, J-F

    2011-03-01

    Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 × 10(20) n∕cm(2). A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.

  15. New measurement system for on line in core high-energy neutron flux monitoring in materials testing reactor conditions

    SciTech Connect

    Geslot, B.; Filliatre, P.; Barbot, L.; Jammes, C.; Breaud, S.; Oriol, L.; Villard, J.-F.; Lopez, A. Legrand

    2011-03-15

    Flux monitoring is of great interest for experimental studies in material testing reactors. Nowadays, only the thermal neutron flux can be monitored on line, e.g., using fission chambers or self-powered neutron detectors. In the framework of the Joint Instrumentation Laboratory between SCK-CEN and CEA, we have developed a fast neutron detector system (FNDS) capable of measuring on line the local high-energy neutron flux in fission reactor core and reflector locations. FNDS is based on fission chambers measurements in Campbelling mode. The system consists of two detectors, one detector being mainly sensitive to fast neutrons and the other one to thermal neutrons. On line data processing uses the CEA depletion code DARWIN in order to disentangle fast and thermal neutrons components, taking into account the isotopic evolution of the fissile deposit. The first results of FNDS experimental test in the BR2 reactor are presented in this paper. Several fission chambers have been irradiated up to a fluence of about 7 x 10{sup 20} n/cm{sup 2}. A good agreement (less than 10% discrepancy) was observed between FNDS fast flux estimation and reference flux measurement.

  16. The Efficiency of the BC-720 Scintillator in a High-Energy (20--800 MeV) Accelerator Neutron Field

    SciTech Connect

    Miles, Leslie H.

    2005-12-01

    High-energy neutron doses (>20 MeV) are of little importance to most radiation workers. However, space and flight crews, and people working around medical and scientific accelerators receive over half of their radiation dose from high-energy neutrons. Unfortunately, neutrons are difficult to measure, and no suitable dosimetry has yet been developed to measure this radiation. In this paper, basic high-energy neutron interactions, characteristics of high-energy neutron environments, present neutron dosimetry, and quantities used in neutron dosimetry are discussed before looking into the potential of the BC-720 scintillator to improve dosimetry. This research utilized 800 MeV protons impinging upon the WNR Facility spallation neutron source at Los Alamos National Laboratory. Time-of-flight methods and a U-238 Fission Chamber were used to aid evaluation of the efficiency of the BC-720. Results showed that the efficiency is finite over the 20–650 MeV energy region studied, although it decreases by a factor of ten between 40 and 100 MeV. This limits the use of this dosimeter to measure doses at sitespecific locations. It also encourages modifications to use this dosimeter for any unknown neutron field. As such, this dosimeter has the potential for a small, lightweight, real-time dose measurement, which could impact neutron dosimetry in all high-energy neutron environments.

  17. Review of spent-fuel photon and neutron source spectra

    SciTech Connect

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

    1986-01-01

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

  18. Gamma-ray, neutron, and hard X-ray studies and requirements for a high-energy solar physics facility

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Dennis, B. R.; Emslie, A. G.

    1988-01-01

    The requirements for future high-resolution spatial, spectral, and temporal observation of hard X-rays, gamma rays and neutrons from solar flares are discussed in the context of current high-energy flare observations. There is much promise from these observations for achieving a deep understanding of processes of energy release, particle acceleration and particle transport in a complicated environment such as the turbulent and highly magnetized atmosphere of the active sun.

  19. Gamma-ray, neutron, and hard X-ray studies and requirements for a high-energy solar physics facility

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Dennis, B. R.; Emslie, A. G.

    1988-01-01

    The requirements for future high-resolution spatial, spectral, and temporal observation of hard X-rays, gamma rays and neutrons from solar flares are discussed in the context of current high-energy flare observations. There is much promise from these observations for achieving a deep understanding of processes of energy release, particle acceleration and particle transport in a complicated environment such as the turbulent and highly magnetized atmosphere of the active sun.

  20. Neutron dose and energy spectra measurements at Savannah River Plant

    SciTech Connect

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

    1987-08-01

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

  1. Effect of wall thickness on measurement of dose for high energy neutrons.

    PubMed

    Perez-Nunez, Delia; Braby, Leslie A

    2010-01-01

    Neutrons produced from the interaction between galactic cosmic rays and spacecraft materials are responsible for a very important portion of the dose received by astronauts. The neutron energy spectrum depends on the incident charged particle spectrum and the scattering environment but generally extends to beyond 100 MeV. Tissue-equivalent proportional counters (TEPC) are used to measure the dose during the space mission, but their weight and size are very important factors for their design and construction. To achieve ideal neutron dosimetry, the wall thickness should be at least the range of a proton having the maximum energy of the neutrons to be monitored. This proton range is 0.1 cm for 10 MeV neutrons and 7.6 cm for 100 MeV neutrons. A 7.6 cm wall thickness TEPC would provide charged particle equilibrium (CPE) for neutrons up to 100 MeV, but for space applications it would not be reasonable in terms of weight and size. In order to estimate the errors in measured dose due to absence of CPE, MCNPX simulations of energy deposited by 10 MeV and 100 MeV neutrons in sites with wall thickness between 0.1 cm and 8.5 cm were performed. The results for 100 MeV neutrons show that energy deposition per incident neutron approaches a plateau as the wall thickness approaches 7.6 cm. For the 10 MeV neutrons, energy deposition per incident neutron decreases as the wall thickness increases above 0.1 cm due to attenuation.

  2. Measurements of high-energy neutron and proton fluxes on-board "Mir-Spectr" orbital complex.

    PubMed

    Kudryavtsev, M I; Bogomolov, A V; Bogomolov, V V; Denisov YuI; Svertilov, S I

    1998-01-01

    The measurements of high-energy neutron (with energies approximately 30-300 MeV) and proton (with energies approximately 1-200 MeV) fluxes are being conducted on-board "Mir-Spectr" orbital complex. Neutrons are detected by the undirected (FOV approximately 4 pi sr) scintillator spectrometer, consisting of 4 identical CsI(T1) detector units (the effective area for neutrons approximately 30 cm2). The gamma-quanta, which can be also detected by this instrument, are separated from neutrons by the analysis of the scintillator output pulse shape. To exclude registration of charged particles an anticoincidence plastic scintillator shield is realized in each detector unit. The proton fluxes are measured by the telescope based on 3 semiconductor detectors with small geometry factor (approximately 1 cm2 x sr). As the first result of the experiment the upper limit of the integral flux of local and albedo neutrons in the equatorial region (L<1. 1) was estimated. The results of this measurements can be useful for the radiation security. Also, the neutrons of solar flares can be detected in this experiment.

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

    NASA Astrophysics Data System (ADS)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

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

  4. Are high energy proton beams ideal for AB-BNCT? A brief discussion from the viewpoint of fast neutron contamination control.

    PubMed

    Lee, Pei-Yi; Liu, Yuan-Hao; Jiang, Shiang-Huei

    2014-06-01

    High energy proton beam (>8MeV) is favorable for producing neutrons with high yield. However, the produced neutrons are of high energies. These high energy neutrons can cause severe fast neutron contamination and degrade the BNCT treatment quality if they are not appropriately moderated. Hence, this study aims to briefly discuss the issue, from the viewpoint of fast neutron contamination control, whether high energy proton beam is ideal for AB-BNCT or not. In this study, D2O, PbF4, CaF2, and Fluental(™) were used standalone as moderator materials to slow down 1-, 6-, and 10-MeV parallelly incident neutrons. From the calculated results, we concluded that neutrons produced by high energy proton beam could not be easily moderated by a single moderator to an acceptable contamination level and still with reasonable epithermal neutron beam intensity. Hence, much more complicated and sophisticated designs of beam shaping assembly have to be developed when using high energy proton beams. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Simulation experiments for gamma-ray mapping of planetary surfaces: Scattering of high-energy neutrons

    NASA Technical Reports Server (NTRS)

    Brueckner, J.; Englert, P.; Reedy, R. C.; Waenke, H.

    1986-01-01

    The concentration and distribution of certain elements in surface layers of planetary objects specify constraints on models of their origin and evolution. This information can be obtained by means of remote sensing gamma-ray spectroscopy, as planned for a number of future space missions, i.e., Mars, Moon, asteroids, and comets. To investigate the gamma-rays made by interactions of neutrons with matter, thin targets of different composition were placed between a neutron-source and a high-resolution germanium spectrometer. Gamma-rays in the range of 0.1 to 8 MeV were accumulated. In one set of experiments a 14-MeV neutron generator using the T(d,n) reaction as neutron-source was placed in a small room. Scattering in surrounding walls produced a spectrum of neutron energies from 14 MeV down to thermal. This complex neutron-source induced mainly neutron-capture lines and only a few scattering lines. As a result of the set-up, there was a considerable background of discrete lines from surrounding materials. A similar situation exists under planetary exploration conditions: gamma-rays are induced in the planetary surface as well as in the spacecraft. To investigate the contribution of neutrons with higher energies, an experiment for the measurement of prompt gamma radiation was set up at the end of a beam-line of an isochronous cyclotron.

  6. Prompt fission neutron spectra in fast-neutron-induced fission of 238U

    NASA Astrophysics Data System (ADS)

    Desai, V. V.; Nayak, B. K.; Saxena, A.; Suryanarayana, S. V.; Capote, R.

    2015-07-01

    Prompt fission neutron spectrum (PFNS) measurements for the neutron-induced fission of 238U are carried out at incident neutron energies of 2.0, 2.5, and 3.0 MeV, respectively. The time-of-flight technique is employed to determine the energy of fission neutrons. The prompt fission neutron energy spectra so obtained are analyzed using Watt parametrization to derive the neutron multiplicity and average prompt fission neutron energy. The present experimental PFNS data are compared with the evaluated spectra taken from the ENDF/B-VII.1 library and the predictive calculations carried out using the empire-3.2 (Malta) code with built-in Los Alamos (LA) and Kornilov PFNS models. The sensitivity of the empire-3.2 LA model-calculated PFNS to the nuclear level density parameter of the average fission fragment and to the total kinetic energy is investigated. empire-3.2 LA model PFNS calculations that use Madland 2006-recommended values [D. G. Madland, Nucl. Phys. A 772, 113 (2006), 10.1016/j.nuclphysa.2006.03.013] of the total kinetic energy and the level density parameter a =A /(10 ±0.5 ) compare very well to measured data at all incident neutron incident energies.

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

    SciTech Connect

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

    1996-01-17

    We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures ({le}3 - 5 x 10{sup 4} K), whereas in the case of iron composition it arises at T{sub eff}{le} 3 x 10{sup 5}K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. Thus, it should be taken into account for the proper interpretation of EUV/soft-X-ray observations of the thermal radiation from neutron stars.

  8. Localization, time histories, and energy spectra of a new type of recurrent high-energy transient source

    NASA Technical Reports Server (NTRS)

    Atteia, J.-L.; Boer, M.; Hurley, K.; Niel, M.; Vedrenne, G.; Fenimore, E. E.; Klebesadel, R. W.; Laros, J. G.; Kuznetsov, A. V.; Kouveliotou, C.

    1987-01-01

    The detection of a recurrent high-energy transient source which is neither a classical X-ray nor a gamma-ray burster, but whose properties are intermediate between the two, is reported. The energy spectra of 12 recurrent events are found to be soft, characterized by kT's of 34-56 keV. The time histories are short with rise and fall times as fast as about 10 ms. The source location is a 0.12 sq deg region about 10 deg from the Galactic center.

  9. Overview of reaction mechanisms for calculating the high energy component of fast-nucleon induced gamma spectra

    SciTech Connect

    Dietrich, F.S.

    1995-02-21

    This presentation reviews the current status of quantum mechanical models for understanding the high-energy component of gamma spectra resulting from radiative capture of fast nucleons; i.e., the part of the spectrum that is not amenable to standard statistical model (Hauser-Feshbach) treatments. These models are based on the direct-semidirect (DSD) model and its variants. Included are recent results on the extension of the DSD model to unbound final states, a discussion of problems and improvements in understanding the form factors in this model, and a brief discussion of a model closely related to the DSD, the pure-resonance model.

  10. Few groups neutron spectra, and dosimetric features, of isotopic neutron sources.

    PubMed

    Vega-Carrillo, Hector Rene; Martinez-Ovalle, Segundo Agustín

    2016-11-01

    Using Monte Carlo methods, the neutron spectra in 31 energy groups of several isotopic neutron sources were estimated. For each source the neutron mean energy; the Ambient dose equivalent, the Personal dose equivalent and the Effective dose per unit fluence rate were calculated. A convenient way to produce neutrons is the isotopic neutron source, where the production is through (α, n), (γ, n), and spontaneous fission reactions. Isotopic neutron sources are small, easy to handle, and have a relative low cost. On the other hand the neutron yield is small and mostly of them produces neutrons with a wide energy distribution. In this work, the main features of (24)NaBe, (24)NaD2O, (116)InBe, (140)LaBe, (238)PuLi, (239)PuBe, (241)AmB, (241)AmBe, (241)AmF, (241)AmLi, (242)CmBe, (210)PoBe, (226)RaBe, (252)Cf and (252)Cf/D2O isotopic neutron source are also compiled.

  11. OER and RBE of high energy neutron beams for growth inhibition in Vicia faba.

    PubMed

    Van Dam, J; Billiet, G; Zoetelief, J; Broerse, J J; Wambersie, A

    1983-01-01

    The radiobiologic characteristics of 15 MeV neutrons produced by the d + T reaction at the TNO of Rijswijk and of neutrons produced by the d(50) + Be and p(75) + Be reactions at the cyclotron Cyclone of Louvain-la- Neuve were compared. Growth inhibition in Vicia faba bean roots was used as biologic system. An OER value of 1.5 +/- 0.1 ws obtained for the neutron beams compared. The RBE of 15 MeV, d(50) + Be and p(75) + Be neutrons was found equal to 3.4 +/- 0.2, 3.2 +/- 0.2 and 2.9 +/- 0.3, respectively, relative to gamma rays, for a total (n + gamma) absorbed dose of 0.6 Gy.

  12. Measurements of high-energy neutron-induced fission ofnatPb and 209Bi

    NASA Astrophysics Data System (ADS)

    Tarrío, D.; Tassan-Got, L.; Audouin, L.; Berthier, B.; Duran, I.; Ferrant, L.; Isaev, S.; Le Naour, C.; Paradela, C.; Stephan, C.; Trubert, D.; Abbondanno, U.; Aerts, G.; Álvarez, H.; Álvarez-Velarde, F.; Andriamonje, S.; Andrzejewski, J.; Assimakopoulos, P.; Badurek, G.; Baumann, P.; Becvár, F.; Berthoumieux, E.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Capote, R.; Carrapiço, C.; Cennini, P.; Chepel, V.; Chiaveri, E.; Colonna, N.; Cortes, G.; Couture, A.; Cox, J.; Dahlfors, M.; David, S.; Dillmann, I.; Domingo-Pardo, C.; Dridi, W.; Eleftheriadis, C.; Embid-Segura, M.; Ferrari, A.; Ferreira-Marques, R.; Fujii, K.; Furman, W.; Gonçalves, I.; González-Romero, E.; Gramegna, F.; Guerrero, C.; Gunsig, F.; Haas, B.; Haight, R.; Heil, M.; Herrera-Martinez, A.; Igashira, M.; Jericha, E.; Kadi, Y.; Käppeler, F.; Karadimos, D.; Karamanis, D.; Kerveno, M.; Koehler, P.; Kossionides, E.; Krticka, M.; Lampoudis, C.; Leeb, H.; Lindote, A.; Lopes, I.; Lozano, M.; Lukic, S.; Marganiec, J.; Marrone, S.; Martínez, T.; Massimi, C.; Mastinu, P.; Mengoni, A.; Milazzo, P. M.; Moreau, C.; Mosconi, M.; Neves, F.; Oberhummer, H.; O'Brien, S.; Oshima, M.; Pancin, J.; Papachristodoulou, C.; Papadopoulos, C.; Patronis, N.; Pavlik, A.; Pavlopoulos, P.; Perrot, L.; Pigni, M. T.; Plag, R.; Plompen, A.; Plukis, A.; Poch, A.; Praena, J.; Pretel, C.; Quesada, J.; Rauscher, T.; Reifarth, R.; Rubbia, C.; Rudolf, G.; Rullhusen, P.; Salgado, J.; Santos, C.; Sarchiapone, L.; Savvidis, I.; Tagliente, G.; Tain, J. L.; Tavora, L.; Terlizzi, R.; Vannini, G.; Vaz, P.; Ventura, A.; Villamarin, D.; Vicente, M. C.; Vlachoudis, V.; Vlastou, R.; Voss, F.; Walter, S.; Wiescher, M.; Wisshak, K.

    2010-10-01

    The CERN Neutron Time-Of-Flight (n_TOF) facility is well suited to measure low cross sections as those of neutron-induced fission in subactinides. The cross section ratios of natPb and 209Bi relative to 235U and 238U were measured using PPAC detectors and a fragment coincidence method that allows us to identify the fission events. The present experiment provides first results for neutron-induced fission up to 1 GeV. Good agreement is found with previous experimental data below 200 MeV. The comparison with proton-induced fission indicates that the limiting regime where neutron-induced and proton-induced fission reach equal cross sections is close to 1 GeV.

  13. Study on Response Function of Organic Liquid Scintillator for High-Energy Neutrons

    NASA Astrophysics Data System (ADS)

    Satoh, Daiki; Sato, Tatsuhiko; Endo, Akira; Yamaguchi, Yasuhiro; Takada, Masashi; Ishibashi, Kenji

    2005-05-01

    Response functions of liquid organic scintillator for neutrons up to 800 MeV have been measured at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) of National Institute of Radiological Sciences (NIRS). 800-MeV/u Si ions and 400-MeV/u C ions bombarded a thick carbon target to produce neutrons. The kinetic energies of emitted neutrons were determined by the time-of-flight (TOF) method. Light output for neutrons was evaluated by eliminating events due to gamma-rays and charged particles. The measured response functions were compared with calculations using SCINFUL-QMD and CECIL codes. It was found that SCINFUL-QMD reproduced our experimental data adequately.

  14. Development of highly efficient proton recoil counter telescope for absolute measurement of neutron fluences in quasi-monoenergetic neutron calibration fields of high energy

    NASA Astrophysics Data System (ADS)

    Shikaze, Yoshiaki; Tanimura, Yoshihiko; Saegusa, Jun; Tsutsumi, Masahiro

    2010-04-01

    Precise calibration of monitors and dosimeters for use with high energy neutrons necessitates reliable and accurate neutron fluences being evaluated with use of a reference point. A highly efficient Proton Recoil counter Telescope (PRT) to make absolute measurements with use of a reference point was developed to evaluate neutron fluences in quasi-monoenergetic neutron fields. The relatively large design of the PRT componentry and relatively thick, approximately 2 mm, polyethylene converter contributed to high detection efficiency at the reference point over a large irradiation area at a long distance from the target. The polyethylene converter thickness was adjusted to maintain the same carbon density per unit area as the graphite converter for easy background subtraction. The high detection efficiency and thickness adjustment resulted in efficient absolute measurements being made of the neutron fluences of sufficient statistical precision over a short period of time. The neutron detection efficiencies of the PRT were evaluated using MCNPX code at 2.61×10-6, 2.16×10-6 and 1.14×10-6 for the respective neutron peak energies of 45, 60 and 75 MeV. The neutron fluences were determined to have been evaluated at an uncertainty of within 6.5% using analysis of measured data and the detection efficiencies. The PRT was also designed so as to be capable of simultaneously obtaining TOF data. The TOF data also increased the reliability of neutron fluence measurements and provided useful information for use in interpreting the source of proton events.

  15. High energy X-ray spectra of cygnus XR-1 observed from OSO-8

    NASA Technical Reports Server (NTRS)

    Dolan, J. F.; Crannell, C. J.; Dennis, B. R.; Frost, K. J.; Orwig, L. E.

    1978-01-01

    X-ray spectra of Cygnus XR-1 were measured with the scintillation spectrometer on board the OSO-8 satellite during a period of one and one-half to three weeks in each of the years from 1975 to 1977. Observations were made when the source was both in a high state and in a low state. Typical spectra of the source between 15 and 250 keV are presented. The observed pivoting effect is consistent with two temperature accretion disk models of the X-ray emitting region. No significant break in the spectrum occurred at energies up to 150 keV. The high state as defined in the 3 to 6 keV bandwidth was found to be the higher luminosity state of the X-ray source. One transition from a low to a high state occurred during observations. The time of occurrence of this and other transitions is consistent with the hypothesis that all intensity transitions occur near periastron of the binary system, and that such transitions are caused by changes in the mass transfer rate between the primary and the accretion disk around the secondary.

  16. Chromosome Aberrations in Human Epithelial Cells Exposed Los Alamos High-Energy Secondary Neutrons: M-BAND Analysis

    NASA Technical Reports Server (NTRS)

    Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

    2007-01-01

    High-energy secondary neutrons, produced by the interaction of galactic cosmic rays (GCR) with the atmosphere, spacecraft structure and planetary surfaces, contribute a significant fraction to the dose equivalent radiation measurement in crew members and passengers of commercial aviation travel as well as astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility's 30L beam line (4FP30L-A/ICE House) is known to generate neutrons that simulate the secondary neutron spectrum of the Earth's atmosphere at high altitude. The neutron spectrum is also similar to that measured onboard spacecrafts like the MIR and the International Space Station (ISS). To evaluate the biological damage, we exposed human epithelial cells in vitro to the LANSCE neutron beams with an entrance dose rate of 2.5 cGy/hr, and studied the induction of chromosome aberrations that were identified with multicolor-banding in situ hybridization (mBAND) technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of inter-chromosomal aberrations (translocation to unpainted chromosomes) and intra-chromosomal aberrations (inversions and deletions within a single painted chromosome). Compared to our previous results with gamma-rays and 600 MeV/nucleon Fe ions of high dose rate at NSRL (NASA Space Radiation Laboratory at Brookhaven National Laboratory), the neutron data from the LANSCE experiments showed significantly higher frequency of chromosome aberrations. However, detailed analysis of the inversion type revealed that all of the three radiation types in the study induced a low incidence of simple inversions. Most of the inversions in gamma-ray irradiated samples were accompanied by other types of intrachromosomal aberrations but few inversions were accompanied by interchromosomal aberrations. In contrast, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both

  17. Chromosome Aberrations in Human Epithelial Cells Exposed Los Alamos High-Energy Secondary Neutrons: M-BAND Analysis

    NASA Technical Reports Server (NTRS)

    Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

    2007-01-01

    High-energy secondary neutrons, produced by the interaction of galactic cosmic rays (GCR) with the atmosphere, spacecraft structure and planetary surfaces, contribute a significant fraction to the dose equivalent radiation measurement in crew members and passengers of commercial aviation travel as well as astronauts in space missions. The Los Alamos Nuclear Science Center (LANSCE) neutron facility's 30L beam line (4FP30L-A/ICE House) is known to generate neutrons that simulate the secondary neutron spectrum of the Earth's atmosphere at high altitude. The neutron spectrum is also similar to that measured onboard spacecrafts like the MIR and the International Space Station (ISS). To evaluate the biological damage, we exposed human epithelial cells in vitro to the LANSCE neutron beams with an entrance dose rate of 2.5 cGy/hr, and studied the induction of chromosome aberrations that were identified with multicolor-banding in situ hybridization (mBAND) technique. With this technique, individually painted chromosomal bands on one chromosome allowed the identification of inter-chromosomal aberrations (translocation to unpainted chromosomes) and intra-chromosomal aberrations (inversions and deletions within a single painted chromosome). Compared to our previous results with gamma-rays and 600 MeV/nucleon Fe ions of high dose rate at NSRL (NASA Space Radiation Laboratory at Brookhaven National Laboratory), the neutron data from the LANSCE experiments showed significantly higher frequency of chromosome aberrations. However, detailed analysis of the inversion type revealed that all of the three radiation types in the study induced a low incidence of simple inversions. Most of the inversions in gamma-ray irradiated samples were accompanied by other types of intrachromosomal aberrations but few inversions were accompanied by interchromosomal aberrations. In contrast, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both

  18. Simulation of neutron displacement damage in bipolar junction transistors using high-energy heavy ion beams.

    SciTech Connect

    Doyle, Barney Lee; Buller, Daniel L.; Hjalmarson, Harold Paul; Fleming, Robert M; Bielejec, Edward Salvador; Vizkelethy, Gyorgy

    2006-12-01

    Electronic components such as bipolar junction transistors (BJTs) are damaged when they are exposed to radiation and, as a result, their performance can significantly degrade. In certain environments the radiation consists of short, high flux pulses of neutrons. Electronics components have traditionally been tested against short neutron pulses in pulsed nuclear reactors. These reactors are becoming less and less available; many of them were shut down permanently in the past few years. Therefore, new methods using radiation sources other than pulsed nuclear reactors needed to be developed. Neutrons affect semiconductors such as Si by causing atomic displacements of Si atoms. The recoiled Si atom creates a collision cascade which leads to displacements in Si. Since heavy ions create similar cascades in Si we can use them to create similar damage to what neutrons create. This LDRD successfully developed a new technique using easily available particle accelerators to provide an alternative to pulsed nuclear reactors to study the displacement damage and subsequent transient annealing that occurs in various transistor devices and potentially qualify them against radiation effects caused by pulsed neutrons.

  19. High energy cosmic ray physics with underground muons in MACRO. II. Primary spectra and composition

    SciTech Connect

    Bellotti, R.; Cafagna, F.; Calicchio, M.; Castellano, M.; De Cataldo, G.; De Marzo, C.; Erriquez, O.; Favuzzi, C.; Fusco, P.; Giglietto, N.; Guarnaccia, P.; Mazziotta, M.N.; Montaruli, T.; Raino, A.; Spinelli, P.; Cecchini, S.; Dekhissi, H.; Fantini, R.; Giacomelli, G.; Mandrioli, G.; Margiotta-Neri, A.; Patrizii, L.; Popa, V.; Serra-Lugaresi, P.; Spurio, M.; Togo, V.; Hong, J.T.; Kearns, E.; Okada, C.; Orth, C.; Stone, J.L.; Sulak, L.R.; Barish, B.C.; Goretti, M.; Katsavounidis, E.; Kyriazopoulou, S.; Michael, D.G.; Nolty, R.; Peck, C.W.; Scholberg, K.; Walter, C.W.; Lane, C.; Steinberg, R.; Battistoni, G.; Bilokon, H.; Bloise, C.; Carboni, M.; Chiarella, V.; Forti, C.; Iarocci, E.; Marini, A.; Patera, V.; Ronga, F.; Satta, L.; Sciubba, A.; Spinetti, M.; Valente, V.; Antolini, R.; Bosio, T.; Di Credico, A.; Grillo, A.; Gustavino, C.; Mikheyev, S.; Parlati, S.; Reynoldson, J.; Scapparone, E.; Bower, C.; Habig, A.; Hawthorne, A.; Heinz, R.; Miller, L.; Mufson, S.; Musser, J.; De Mitri, I.; Monacelli, P.; Bernardini, P.; Mancarella, G.; Martello, D.; Palamara, O.; Petrera, S.; Pistilli, P.; Ricciardi, M.; Surdo, A.; Baker, R.; and others

    1997-08-01

    Multimuon data from the MACRO experiment at Gran Sasso have been analyzed using a new method, which allows one to estimate the primary cosmic ray fluxes. The estimated all-particle spectrum is higher and flatter than the one obtained from direct measurements but is consistent with EAS array measurements. The spectral indexes of the fitted energy spectrum are 2.56{plus_minus}0.05 for E{lt}500 TeV and 2.9{plus_minus}0.3 for E{gt}5000 TeV with a gradual change at intermediate energies. The average mass number shows little dependence on the primary energy below 1000 TeV, with a value of 10.1{plus_minus}2.5 at 100 TeV. At higher energies the best fit average mass shows a mild increase with energy, even though no definite conclusion can be reached taking into account errors. The fitted spectra cover a range from {approximately} 50 TeV up to several thousand TeV. {copyright} {ital 1997} {ital The American Physical Society}

  20. High-energy astrophysics: A theoretical analysis of thermal radiation from neutron stars

    NASA Technical Reports Server (NTRS)

    Applegate, James H.

    1994-01-01

    The unambiguous detection of thermal radiation from the surface of a cooling neutron star was one of the most anxiously awaited results in neutron star physics. This particular Holy Grail was found by Halpern and Holt, who used ROSAT to detect pulsed X-rays from the gamma-ray source Geminga and demonstrate that it was a neutron star, probably a radio pulsar beamed away from us. At an age of approximately 3.4 x 10(exp 5) years, Geminga is in the photon cooling era. Its surface temperature of 5.2 x 10(exp 5) K can be explained within the contexts of both the slow and fast cooling scenarios. In the slow cooling scenario, the surface temperature is too high unless the specific heat of the interior is reduced by extensive baryon pairing. In the fast cooling scenario, the surface temperature will be much too low unless the fast neutrino cooling is shut off by baryon pairing. Two other pulsars, PSR 0656+14 and PSR 1055-52, have also been detected in thermal X-rays by ROSAT. They are also in the photon cooling era. All of this research's neutron star cooling models to date have used the unmagnetized effective temperature-interior temperature relation for the outer boundary condition. Models are being improved by using published magnetic envelope calculations and assumed geometried for the surface magnetic field to determine local interior temperature-emitted flux relations for the surface of the star.

  1. Measurement of high-energy neutrons at ISS by SEDA-AP

    NASA Astrophysics Data System (ADS)

    Koga, K.; Goka, T.; Matsumoto, H.; Obara, T.; Muraki, Y.; Yamamoto, T.

    2011-09-01

    A new type of solar neutron detector (NEM) was launched by the space shuttle Endeavour on 16 July 2009 and it began collecting data on 25 August 2009 at the International Space Station (ISS). In this paper we introduce preliminary results obtained by the NEM.

  2. Van der Waals Type Model for Neutron-Proton Elastic Scattering at High Energies

    NASA Astrophysics Data System (ADS)

    Aleem, F.

    1980-12-01

    The most recent measurements of the angular distribution and total cross-section for neutron-proton elastic scattering between 70< pL <400 GeV/c with squared four momentum transfer -t ≤ 3.6 (GeV/c)2 have been explained using Van der Waals type model.

  3. Time gating for energy selection and scatter rejection: High-energy pulsed neutron imaging at LANSCE

    NASA Astrophysics Data System (ADS)

    Swift, Alicia; Schirato, Richard; McKigney, Edward; Hunter, James; Temple, Brian

    2015-09-01

    The Los Alamos Neutron Science Center (LANSCE) is a linear accelerator in Los Alamos, New Mexico that accelerates a proton beam to 800 MeV, which then produces spallation neutron beams. Flight path FP15R uses a tungsten target to generate neutrons of energy ranging from several hundred keV to ~600 MeV. The beam structure has micropulses of sub-ns width and period of 1.784 ns, and macropulses of 625 μs width and frequency of either 50 Hz or 100 Hz. This corresponds to 347 micropulses per macropulse, or 1.74 x 104 micropulses per second when operating at 50 Hz. Using a very fast, cooled ICCD camera (Princeton Instruments PI-Max 4), gated images of various objects were obtained on FP15R in January 2015. Objects imaged included blocks of lead and borated polyethylene; a tungsten sphere; and a tungsten, polyethylene, and steel cylinder. Images were obtained in 36 min or less, with some in as little as 6 min. This is novel because the gate widths (some as narrow as 10 ns) were selected to reject scatter and other signal not of interest (e.g. the gamma flash that precedes the neutron pulse), which has not been demonstrated at energies above 14 MeV. This proof-of-principle experiment shows that time gating is possible above 14MeV and is useful for selecting neutron energy and reducing scatter, thus forming clearer images. Future work (simulation and experimental) is being undertaken to improve camera shielding and system design and to precisely determine optical properties of the imaging system.

  4. (A neutron scattering experiment to study the high-energy spin dynamics of the itinerant antiferromagnet Mn sub 90 Cu sub 10 )

    SciTech Connect

    Fernandez-Baca, J.A.

    1990-10-26

    The traveler performed a neutron scattering experiment to study the high-energy spin dynamics of the itinerant antiferromagnet. This experiment was conducted at a unique instrument located at the hot-neutron source at the ILL. The traveler also held various scientific discussions with ILL research staff members and visiting scientists.

  5. Measurement of neutron spectra in the experimental reactor LR-0

    SciTech Connect

    Prenosil, Vaclav; Mravec, Filip; Veskrna, Martin; Kostal, Michal; Matej, Zdenek; Cvachovec, Frantisek

    2015-07-01

    The measurement of fast neutron fluxes is important in many areas of nuclear technology. It affects the stability of the reactor structural components, performance of fuel, and also the fuel manner. The experiments performed at the LR-0 reactor were in the past focused on the measurement of neutron field far from the core, in reactor pressure vessel simulator or in biological shielding simulator. In the present the measurement in closer regions to core became more important, especially measurements in structural components like reactor baffle. This importance increases with both reactor power increase and also long term operation. Other important task is an increasing need for the measurement close to the fuel. The spectra near the fuel are aimed due to the planned measurements with the FLIBE salt, in FHR / MSR research, where one of the task is the measurement of the neutron spectra in it. In both types of experiments there is strong demand for high working count rate. The high count rate is caused mainly by high gamma background and by high fluxes. The fluxes in core or in its vicinity are relatively high to ensure safe reactor operation. This request is met in the digital spectroscopic apparatus. All experiments were realized in the LR-0 reactor. It is an extremely flexible light water zero-power research reactor, operated by the Research Center Rez (Czech Republic). (authors)

  6. High-energy transients. [from weakly and strongly magnetic neutron stars

    NASA Technical Reports Server (NTRS)

    Lamb, D. Q.

    1991-01-01

    The observational characteristics of X-ray bursts are reviewed and the thermonuclear-flash model is examined to assess the suitability of the model and the sources of X- and gamma-ray bursts. The profiles of X-ray bursts from five different sources are delineated, and the global analysis of nuclear burning is discussed to review th range possible X-ray burst behavior. The analysis by Fushiki and Lamb (1987) is noted for the description of regions which lie away from the steady-state cut. The discussion of cyclotron lines in gamma-ray bursts emphasizes the source GB880205, and it is shown that Raman and cyclotron resonant scattering can explain the observed positions, strengths, and widths of the dips in the spectrum. X-ray bursts are theorized to emanate from weakly magnetic neutron stars, and gamma-ray bursts are shown to be the products of strongly magnetic neutron stars.

  7. The properties of gamma-radiation and high-energy neutron fluxes in "MIR" station orbit.

    PubMed

    Bogomolov, A V; Bogomolov, V V; Denisov, Yu I; Logachev, Yu I; Svertilov, S I; Kudryavtsev, M I; Lyagushin, V I; Ershova, T V

    2002-10-01

    The study of radiation background components in the near-Earth space is very important for different branches of space research, in particular for space dosimetry and for the planning of gamma-astronomy experiments. Detailed information on the neutral components (gamma-quanta, neutrons) of background radiation was obtained during the Grif-1 experiment onboard Mir orbital station (OS). The measurements of fluxes of 0.05-50 MeV gamma-quanta and >30 MeV neutrons with a large area instrument (approximately 250 cm2 for gamma-quanta, approximately 30 cm2 for neutrons) as well as corresponding charged particle measurements (0.4-1.5 MeV electrons, 1-200 MeV protons) were made during this experiment. The background components induced by the station's own radiation as well as the albedo gamma-rays from the Earth's atmosphere were revealed as the result of data analysis for about 600 h of observation. A mathematical model describing the latitude and energy dependences of atmospheric albedo gamma-rays as well as of those of gamma-quanta produced in the material of the station due to cosmic ray interactions was developed. An analytical approximation of the spectrum of induced gamma-rays from radioactive isotopes stored in the station and instrument's materials is presented. The dynamics of gamma-quantum background fluxes during the geomagnetic disturbances of January 10-11, 1997 are discussed. An analytical representation of the latitude dependence of the integral flux of neutrons with >30 MeV is given.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  10. Lattice dynamics of α-AlH3 and α-AlD3 by inelastic neutron scattering: High-energy band of optical bond-stretching vibrations

    NASA Astrophysics Data System (ADS)

    Kolesnikov, A. I.; Antonov, V. E.; Markushkin, Yu. E.; Natkaniec, I.; Sakharov, M. K.

    2007-08-01

    Inelastic neutron scattering (INS) spectra of trigonal α-AlH3 and α-AlD3 have been measured in a wide range (5-150meV) of energy transfers with a much better statistical accuracy than previously using the inverted-geometry NERA-PR spectrometer at JINR, Dubna. The studied energy interval covers the range of low-frequency lattice vibrations and a broad band of optical H vibrations. By using a direct-geometry HRMECS spectrometer at ANL, Argonne, the AlH3 hydride was also examined by INS at energy transfers up to 315meV in the regime of small momentum transfers. This significantly enhanced the contribution from the one-phonon neutron scattering and allowed an observation and accurate examination of one more, high-energy band of optical H vibrations predicted theoretically [C. Wolverton , Phys. Rev. B 69, 144109 (2004)]. Combining the obtained experimental data, the entire spectrum of phonon density of states was reconstructed for both α-AlH3 and α-AlD3 .

  11. Measurement of high-energy prompt gamma-rays from neutron induced fission of U-235

    NASA Astrophysics Data System (ADS)

    Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Léguillon, Romain; Ogawa, Tatsuhiko; Soldner, Torsten; Hambsch, Franz-Josef; Astier, Alain; Pollitt, Andrew; Petrache, Costel; Tsekhanovich, Igor; Mathieu, Ludovic; Aïche, Mourad; Frost, Robert; Czajkowski, Serge; Guo, Song; Köster, Ulli

    2017-09-01

    We have developed a new setup to measure prompt γ-rays from the 235U(nth,f) reaction. The setup consists of two multi-wire proportional counters (MWPCs) to detect the fission fragments, two LaBr3(Ce) scintillators to measure the γ-rays. The highly efficient setup was installed at the PF1B beam line of the Institut Laue Langevin (ILL). We have successfully measured the γ-ray spectrum up to about 20 MeV for the fist time in neutron-induced fission.

  12. Phase-resolved spectra of burst oscillations in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Zoghbi, Abderahmen; Miller, Jon M.

    2017-08-01

    Millisecond oscillations have been observed during thermonuclear bursts from many neutron stars (NS) in LMXBs. Their periods are comparable to the rotational period of the NS, and are thought to be produced by temperature anisotropies on the NS surface. Understanding and correcly modeling these oscillation is a powerful tool to constrain the NS interior. Studying these oscillations has thus far focused on modeling the oscillation profile form these pulsations using mostly XTE data. Here, we take a different approach and extract spectra at different phases of the oscillations. This allows us track the observed spectrum as the NS rotates. We are able to measure temperature changes as the star rotates. The temperature profiles from some bursts show asymetries likely due to Doppler effects. Here, we present detailed results from the phase spectra and discuss their implications on measurements of NS masses and radii.

  13. High-energy quasi-monoenergetic neutron fields: existing facilities and future needs.

    PubMed

    Pomp, S; Bartlett, D T; Mayer, S; Reitz, G; Röttger, S; Silari, M; Smit, F D; Vincke, H; Yasuda, H

    2014-10-01

    The argument that well-characterised quasi-monoenergetic neutron (QMN) sources reaching into the energy domain >20 MeV are needed is presented. A brief overview of the existing facilities is given, and a list of key factors that an ideal QMN source for dosimetry and spectrometry should offer is presented. The authors conclude that all of the six QMN facilities currently in existence worldwide operate in sub-optimal conditions for dosimetry. The only currently available QMN facility in Europe capable of operating at energies >40 MeV, TSL in Uppsala, Sweden, is threatened with shutdown in the immediate future. One facility, NFS at GANIL, France, is currently under construction. NFS could deliver QMN beams up to about 30 MeV. It is, however, so far not clear if and when NFS will be able to offer QMN beams or operate with only so-called white neutron beams. It is likely that by 2016, QMN beams with energies >40 MeV will be available only in South Africa and Japan, with none in Europe.

  14. Absorption Features in Spectra of Magnetized Neutron Stars

    SciTech Connect

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

    2011-09-21

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

  15. Measurements of High Energy Neutron Spectrum (> 10 MeV) by Using Yttrium Foils in a U/Pb Assembly

    NASA Astrophysics Data System (ADS)

    Bielewicz, M.; Strugalska-Gola, E.; Szuta, M.; Wojciechowski, A.; Kadykov, M.; Tyutyunnikov, S.

    2014-05-01

    Study of deep subcritical electronuclear systems and radioactive waste transmutation using relativistic beams were performed. This work is a preliminary step toward the study of the physical properties of Accelerator Driven Systems, in which a deeply subcritical active core is irradiated by a pulsed beam of relativistic ions. The long-range goal of the project is to study the capabilities of such systems with a hard neutron spectrum, for transmutation of radioactive nuclear wastes. Two experimental assemblies, “Energy plus Transmutation” (2006-2009) and “Quinta” (2011-), were irradiated by 1 to 6 GeV deuteron beams using the JINR NUCLOTRON accelerator. The main difference between the two experimental setups is the spallation target - lead or natural uranium. We attempt to obtain neutron energy spectra inside the volume of these assemblies using threshold reactions in natural yttrium (89Y) foils. Some results from three different experiments are presented.

  16. Characterizing high energy spectra of NIF ignition hohlraums using a differentially filtered high energy multi-pinhole X-ray imager

    SciTech Connect

    Park, H; Dewald, E D; Glenzer, S; Kalantar, D H; Kilkenny, J D; MacGowan, B J; Maddox, B R; Milovich, J L; Prasad, R R; Remington, B A; Thomas, C A

    2010-05-11

    Understanding hot electron distributions generated inside hohlraums is important to the ignition campaign for controlling implosion symmetry and sources of preheat. While direct imaging of hot electrons is difficult, their spatial distribution and spectrum can be deduced by detecting high energy x-rays generated as they interact with the target materials. We used an array of 18 pinholes, with four independent filter combinations, to image entire hohlraums with a magnification of 0.87x during the hohlraum energetics campaign on NIF. Comparing our results with hohlraum simulations indicates that the characteristic 30 keV hot electrons are mainly generated from backscattered laser plasma interactions rather than from hohlraum hydrodynamics.

  17. High energy neutron and pion-decay gamma-ray emissions from solar flares

    NASA Astrophysics Data System (ADS)

    Chupp, Edward L.; Ryan, James M.

    2009-01-01

    Solar flare gamma-ray emissions from energetic ions and electrons have been detected and measured to GeV energies since 1980. In addition, neutrons produced in solar flares with 100 MeV to GeV energies have been observed at the Earth. These emissions are produced by the highest energy ions and electrons accelerated at the Sun and they provide our only direct (albeit secondary) knowledge about the properties of the accelerator(s) acting in a solar flare. The solar flares, which have direct evidence for pion-decay gamma-rays, are unique and are the focus of this paper. We review our current knowledge of the highest energy solar emissions, and how the characteristics of the acceleration process are deduced from the observations. Results from the RHESSI, INTEGRAL and CORONAS missions will also be covered. The review will also cover the solar flare capabilities of the new mission, FERMI GAMMA RAY SPACE TELESCOPE, launched on 2008 June 11. Finally, we discuss the requirements for future missions to advance this vital area of solar flare physics.

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

    SciTech Connect

    Kroc, T.K.; /Fermilab

    2009-10-01

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

  19. Characterization of neutron-irradiated HT-UPS steel by high-energy X-ray diffraction microscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Xuan; Park, Jun-Sang; Almer, Jonathan; Li, Meimei

    2016-04-01

    This paper presents the first measurement of neutron-irradiated microstructure using far-field high-energy X-ray diffraction microscopy (FF-HEDM) in a high-temperature ultrafine-precipitate-strengthened (HT-UPS) austenitic stainless steel. Grain center of mass, grain size distribution, crystallographic orientation (texture), diffraction spot broadening and lattice constant distributions of individual grains were obtained for samples in three different conditions: non-irradiated, neutron-irradiated (3dpa/500 °C), and irradiated + annealed (3dpa/500 °C + 600 °C/1 h). It was found that irradiation caused significant increase in grain-level diffraction spot broadening, modified the texture, reduced the grain-averaged lattice constant, but had nearly no effect on the average grain size and grain size distribution, as well as the grain size-dependent lattice constant variations. Post-irradiation annealing largely reversed the irradiation effects on texture and average lattice constant, but inadequately restored the microstrain.

  20. Laser-driven high-energy-density deuterium and tritium ions for neutron production in a double-cone configuration

    SciTech Connect

    Hu, Li-Xiang; Yu, Tong-Pu Shao, Fu-Qiu; Yin, Yan; Ma, Yan-Yun; Zhu, Qing-Jun

    2015-12-15

    By using two-dimensional particle-in-cell simulations, we investigate laser-driven ion acceleration and compression from a thin DT foil in a double-cone configuration. By using two counterpropagating laser pulses, it is shown that a double-cone structure can effectively guide, focus, and strengthen the incident laser pulses, resulting in the enhanced acceleration and compression of D{sup +} and T{sup +}. Due to the ion Coulomb repulsion and the effective screening from the external laser electric fields, the transverse diffusion of ions is significantly suppressed. Finally, the peak energy density of the compressed ions exceeds 2.73 × 10{sup 16 }J/m{sup 3}, which is about five orders of magnitude higher than the threshold for high energy density physics, 10{sup 11 }J/m{sup 3}. Under this condition, DT fusion reactions are initiated and the neutron production rate per volume is estimated to be as high as 7.473 × 10{sup 35}/m{sup 3} s according to Monte Carlo simulations. It is much higher than that of the traditional large neutron sources, which may facilitate many potential applications.

  1. High-energy particle production in solar flares (SEP, gamma-ray and neutron emissions). [solar energetic particles

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.

    1987-01-01

    Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near earth, consist of electrons and ions that range in energy from 10 keV to about 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while X-ray, gamma-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism. The paper reviews the physics of gamma-rays and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. Particular attention is given to energetic particle production in the large flare on June 3, 1982.

  2. High Energy Neutrinos Produced in the Accretion Disks by Neutrons from Nuclei Disintegrated in the AGN Jets

    NASA Astrophysics Data System (ADS)

    Bednarek, W.

    2016-12-01

    We investigate the consequences of acceleration of nuclei in jets of active galaxies not far from the surface of an accretion disk. The nuclei can be accelerated in the re-connection regions in the jet and/or at the jet boundary, between the relativistic jet and its cocoon. It is shown that the relativistic nuclei can efficiently fragment onto specific nucleons in collisions with the disk radiation. Neutrons, directed toward the accretion disk, take a significant part of energy from the relativistic nuclei. These neutrons develop a cascade in the dense accretion disk. We calculate the neutrino spectra produced in such a hadronic cascade within the accretion disk. We propose that the neutrinos produced in such a scenario, from the whole population of super-massive black holes in active galaxies, can explain the extragalactic neutrino background recently measured by the IceCube neutrino detector, provided that a 5% fraction of galaxies have an active galactic nucleus and a few percent of neutrons reach the accretion disk. We predict that the neutrino signals in the present neutrino detectors, produced in terms of such a model, will not be detectable even from the nearby radio galaxies similar to M87.

  3. High-energy particle production in solar flares (SEP, gamma-ray and neutron emissions). [solar energetic particles

    NASA Technical Reports Server (NTRS)

    Chupp, E. L.

    1987-01-01

    Electrons and ions, over a wide range of energies, are produced in association with solar flares. Solar energetic particles (SEPs), observed in space and near earth, consist of electrons and ions that range in energy from 10 keV to about 100 MeV and from 1 MeV to 20 GeV, respectively. SEPs are directly recorded by charged particle detectors, while X-ray, gamma-ray, and neutron detectors indicate the properties of the accelerated particles (electrons and ions) which have interacted in the solar atmosphere. A major problem of solar physics is to understand the relationship between these two groups of charged particles; in particular whether they are accelerated by the same mechanism. The paper reviews the physics of gamma-rays and neutron production in the solar atmosphere and the method by which properties of the primary charged particles produced in the solar flare can be deduced. Recent observations of energetic photons and neutrons in space and at the earth are used to present a current picture of the properties of impulsively flare accelerated electrons and ions. Some important properties discussed are time scale of production, composition, energy spectra, accelerator geometry. Particular attention is given to energetic particle production in the large flare on June 3, 1982.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

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

    PubMed

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

    2004-01-01

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

  6. Applicability of self-activation of an NaI scintillator for measurement of photo-neutrons around a high-energy X-ray radiotherapy machine.

    PubMed

    Wakabayashi, Genichiro; Nohtomi, Akihiro; Yahiro, Eriko; Fujibuchi, Toshioh; Fukunaga, Junichi; Umezu, Yoshiyuki; Nakamura, Yasuhiko; Nakamura, Katsumasa; Hosono, Makoto; Itoh, Tetsuo

    2015-01-01

    The applicability of the activation of an NaI scintillator for neutron monitoring at a clinical linac was investigated experimentally. Thermal neutron fluence rates are derived by measurement of the I-128 activity generated in an NaI scintillator irradiated by neutrons; β-rays from I-128 are detected efficiently by the NaI scintillator. In order to verify the validity of this method for neutron measurement, we irradiated an NaI scintillator at a research reactor, and the neutron fluence rate was estimated. The method was then applied to neutron measurement at a 10-MV linac (Varian Clinac 21EX), and the neutron fluence rate was estimated at the isocenter and at 30 cm from the isocenter. When the scintillator was irradiated directly by high-energy X-rays, the production of I-126 was observed due to photo-nuclear reactions, in addition to the generation of I-128 and Na-24. From the results obtained by these measurements, it was found that the neutron measurement by activation of an NaI scintillator has a great advantage in estimates of a low neutron fluence rate by use of a quick measurement following a short-time irradiation. Also, the future application of this method to quasi real-time monitoring of neutrons during patient treatments at a radiotherapy facility is discussed, as well as the method of evaluation of the neutron dose.

  7. Measurements of high energy neutrons penetrated through iron shields using the Self-TOF detector and an NE213 organic liquid scintillator

    NASA Astrophysics Data System (ADS)

    Sasaki, M.; Nakao, N.; Nunomiya, T.; Nakamura, T.; Fukumura, A.; Takada, M.

    2002-11-01

    Neutron energy spectra penetrated through iron shields were measured using the Self-TOF detector and an NE213 organic liquid scintillator which have been newly developed by our group at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) of National Institute of Radiological Sciences (NIRS), Japan. Neutrons were generated by bombarding 400 MeV/nucleon C ion on a thick (stopping-length) copper target. The neutron spectra in the energy range from 20 to 800 MeV were obtained through the FORIST unfolding code with their response functions and compared with the MCNPX calculations combined with the LA150 cross section library. The neutron fluence measured by the NE213 detector was simulated by the track length estimator in the MCNPX, and evaluated the contribution of the room-scattered neutrons. The calculations are in fairly good agreement with the measurements. Neutron fluence attenuation lengths were obtained from the experimental results and the calculation.

  8. Prompt fission neutron spectra of n+235U above the (n,nf) fission threshold

    NASA Astrophysics Data System (ADS)

    Shu, Neng-Chuan; Jia, Min; Chen, Yong-Jing; Liu, Ting-Jin

    2015-05-01

    Calculations of prompt fission neutron spectra (PFNS) from the 235U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n,xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n,xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n,nf) or (n,2nf) reactions influences the PFNS shape, and the neutron spectra of the (n,xnf) fission-channel are soft compared with the neutron spectra of the (n,f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. Supported by National Natural Science Foundation of China (11205246, 91126010, U1230127, 91226102), IAEA CRP (15905), and Defense Industrial Technology Development Program (B0120110034)

  9. SU-E-T-90: Accuracy of Calibration of Lithium-6 and -7 Enriched LiF TLDs for Neutron Measurements in High Energy Radiotherapy

    SciTech Connect

    Keehan, S; Franich, R; Taylor, M; Lonski, P; Kron, T

    2015-06-15

    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 the 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.

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

    SciTech Connect

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

    2008-01-01

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

  11. Particle LET spectra from microelectronics packaging materials subjected to neutron and proton irradiation

    NASA Astrophysics Data System (ADS)

    Browning, J. S.; Holtkamp, D. B.

    1988-12-01

    Cumulative fractions for LET spectra were measured for particles ejected from microelectronics packaging materials subjected to neutron and proton irradiation. The measurements for the neutron irradiation compare well with Monte Carlo theoretical calculations. The spectra can be used to access microelectronics vulnerabilities in strategic-nuclear- weapon, space-trapped, and neutral-beam directed-energy particle environments.

  12. Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field.

    PubMed

    Badhwar, G D; Huff, H; Wilkins, R; Thibeault, Sheila

    2002-12-01

    Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study.

  13. Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study. Published by Elsevier Science Ltd.

  14. Comparison of graphite, aluminum, and TransHab shielding material characteristics in a high-energy neutron field

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    Space radiation transport models clearly show that low atomic weight materials provide a better shielding protection for interplanetary human missions than high atomic weight materials. These model studies have concentrated on shielding properties against charged particles. A light-weight, inflatable habitat module called TransHab was built and shown to provide adequate protection against micrometeoroid impacts and good shielding properties against charged particle radiation in the International Space Station orbits. An experiment using a tissue equivalent proportional counter, to study the changes in dose and lineal energy spectra with graphite, aluminum, and a TransHab build-up as shielding, was carried out at the Los Alamos Nuclear Science Center neutron facility. It is a continuation of a previous study using regolith and doped polyethylene materials. This paper describes the results and their comparison with the previous study. Published by Elsevier Science Ltd.

  15. Ground-based observations of thunderstorm-correlated fluxes of high-energy electrons, gamma rays, and neutrons

    SciTech Connect

    Chilingarian, A.; Daryan, A.; Arakelyan, K.; Hovhannisyan, A.; Mailyan, B.; Melkumyan, L.; Hovsepyan, G.; Chilingaryan, S.; Reymers, A.; Vanyan, L.

    2010-08-15

    The Aragats Space Environmental Center facilities continuously measure fluxes of neutral and charged secondary cosmic ray incidents on the Earth's surface. Since 2003 in the 1-minute time series we have detected more than 100 enhancements in the electron, gamma ray, and neutron fluxes correlated with thunderstorm activities. During the periods of the count rate enhancements, lasting tens of minutes, millions of additional particles were detected. Based on the largest particle event of September 19, 2009, we show that our measurements support the existence of long-lasting particle multiplication and acceleration mechanisms in the thunderstorm atmosphere. For the first time we present the energy spectra of electrons and gamma rays from the particle avalanches produced in the thunderstorm atmosphere, reaching the Earth's surface.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    SciTech Connect

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

    2016-05-25

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

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

    SciTech Connect

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

    2016-05-25

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

  19. 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

  20. Are neutrons responsible for the dose discrepancies between Monte Carlo calculations and measurements in the build-up region for a high-energy photon beam?

    PubMed

    Ding, George X; Duzenli, Cheryl; Kalach, Nina I

    2002-09-07

    This study presents measured neutron dose using a neutron dosimeter in a water phantom and investigates a hypothesis that neutrons in a high-energy photon beam may be responsible for the reported significant dose discrepancies between Monte Carlo calculations and measurements at the build-up region in large fields. Borated polyethylene slabs were inserted between the accelerator head and the phantom in order to remove neutrons generated in the accelerator head. The thickness of the slab ranged from 2.5 cm to 10 cm. A lead slab of 3 mm thickness was also used in the study. The superheated drop neutron dosimeter was used to measure the depth-dose curve of neutrons in a high-energy photon beam and to verify the effectiveness of the slab to remove these neutrons. Total dose measurements were performed in water using a WELLHOFER WP700 beam scanner with an IC-10 ionization chamber. The Monte Carlo code BEAM was used to simulate an 18 MV photon beam from a Varian Clinac-2100EX accelerator. Both EGS4/DOSXYZ and EGSnrc/DOSRZnrc were used in the dose calculations. Measured neutron dose equivalents as a function of depth per unit total dose in water were presented for 10 x 10 and 40 x 40 cm2 fields. The measured results have shown that a 5-10 cm thick borated polyethylene slab can reduce the neutron dose by a factor of 2 when inserted between the accelerator head and the detector. In all cases the measured neutron dose equivalent was less than 0.5% of the photon dose. In order to study if the ion chamber was highly sensitive to the neutron dose, we have investigated the disagreement between the Monte Carlo calculated and measured central-axis depth-dose curves in the build-up region when different shielding materials were used. The result indicated that the IC-10 chamber was not highly sensitive to the neutron dose. Therefore, neutrons present in a high-energy photon beam were unlikely to be responsible for the reported discrepancies in the build-up region for large fields.

  1. Characterization of the PTW 34031 ionization chamber (PMI) at RCNP with high energy neutrons ranging from 100 - 392 MeV

    NASA Astrophysics Data System (ADS)

    Theis, C.; Carbonez, P.; Feldbaumer, E.; Forkel-Wirth, D.; Jaegerhofer, L.; Pangallo, M.; Perrin, D.; Urscheler, C.; Roesler, S.; Vincke, H.; Widorski, M.; Iwamoto, Y.; Hagiwara, M.; Satoh, D.; Iwase, H.; Yashima, H.; Matsumoto, T.; Masuda, A.; Nishiyama, J.; Harano, H.; Itoga, T.; Nakamura, T.; Sato, T.; Nakane, Y.; Nakashima, H.; Sakamoto, Y.; Taniguchi, S.; Nakao, N.; Tamii, A.; Shima, T.; Hatanaka, K.

    2017-09-01

    Radiation monitoring at high energy proton accelerators poses a considerable challenge due to the complexity of the encountered stray radiation fields. These environments comprise a wide variety of different particle types and span from fractions of electron-volts up to several terra electron-volts. As a consequence the use of Monte Carlo simulation programs like FLUKA is indispensable to obtain appropriate field-specific calibration factors. At many locations of the LHC a large contribution to the particle fluence is expected to originate from high-energy neutrons and thus, benchmark experiments with mono-energetic neutron beams are of high importance to verify the aforementioned detector response calculations. This paper summarizes the results of a series of benchmark experiments with quasi mono-energetic neutrons of 100, 140, 200, 250 and 392 MeV that have been carried out at RCNP - Osaka University, during several campaigns between 2006 and 2014.

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

    SciTech Connect

    Hoots, S.; Wadsworth, D.

    1984-06-01

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

  3. Energy spectra and fluence of the neutrons produced in deformed space-time conditions

    NASA Astrophysics Data System (ADS)

    Cardone, F.; Rosada, A.

    2016-10-01

    In this work, spectra of energy and fluence of neutrons produced in the conditions of deformed space-time (DST), due to the violation of the local Lorentz invariance (LLI) in the nuclear interactions are shown for the first time. DST-neutrons are produced by a mechanical process in which AISI 304 steel bars undergo a sonication using ultrasounds with 20 kHz and 330 W. The energy spectrum of the DST-neutrons has been investigated both at low (less than 0.4 MeV) and at high (up to 4 MeV) energy. We could conclude that the DST-neutrons have different spectra for different energy intervals. It is therefore possible to hypothesize that the DST-neutrons production presents peculiar features not only with respect to the time (asynchrony) and space (asymmetry) but also in the neutron energy spectra.

  4. Optimization of Beam-Shaping Assemblies for BNCS Using the High-Energy Neutron Sources D-D and D-T

    SciTech Connect

    Verbeke, Jerome M.; Chen, Allen S.; Vujic, Jasmina L.; Leung, Ka-Ngo

    2001-06-15

    Boron neutron capture synovectomy is a novel approach for the treatment of rheumatoid arthritis. The goal of the treatment is the ablation of diseased synovial membranes in articulating joints. The treatment of knee joints is the focus of this work. A method was developed, as discussed previously, to predict the dose distribution in a knee joint from any neutron and photon beam spectra incident on the knee. This method is validated and used to design moderators for the deuterium-deuterium (D-D) and deuterium-tritium (D-T) neutron sources. Treatment times >2 h were obtained with the D-D reaction. They could potentially be reduced if the {sup 10}B concentration in the synovium was increased. For D-T neutrons, high therapeutic ratios and treatment times <5 min were obtained for neutron yields of 10{sup 14} s{sup -1}. This treatment time makes the D-T reaction attractive for boron neutron capture synovectomy.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    SciTech Connect

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

    1995-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  8. The evaluation of neutron and gamma ray dose equivalent distributions in patients and the effectiveness of shield materials for high energy photons radiotherapy facilities.

    PubMed

    Ghassoun, J; Senhou, N

    2012-04-01

    In this study, the MCNP5 code was used to model radiotherapy room of a medical linear accelerator operating at 18 MV and to evaluate the neutron and the secondary gamma ray fluences, the energy spectra and the dose equivalent distributions inside a liquid tissue-equivalent (TE) phantom. The obtained results were compared with measured data published in the literature. Moreover, the shielding effects of various neutron material shields on the radiotherapy room wall were also investigated. Our simulation results showed that paraffin wax containing boron carbide presents enough effectiveness to reduce both neutron and secondary gamma ray doses.

  9. Russian measurements of neutron energy spectra on the Mir orbital station.

    PubMed

    Lyagushin, V I; Dudkin, V E; Potapov, Y V; Sevastianov, V D

    2001-06-01

    Results of the experiments on neutron energy spectra measurements within broad energy range from 5 x 10(-7) to 2 x 10(2) MeV aboard the Mir orbital station and equivalent neutron dose estimation are presented. Four measurement techniques were used during the experiments. The shape of spectra and their absolute values are in good agreement. According to those experiments, an equivalent neutron dose depends upon effective shielding thickness and spacecraft mass. The neutron dose mentioned is comparable with that of ionizing radiation. Neutron flux levels measured aboard the Mir station have shown that a neutron spectrometer involving broad energy range will be used within the radiation monitoring systems in manned space flights.

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

    PubMed

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

    2014-01-01

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

  11. Theoretical Calculation of Prompt Neutron Spectra from Fission of Curium Isotopes

    NASA Astrophysics Data System (ADS)

    Ohsawa, Takaaki; Tani, Kazuhiro; Kishimoto, Yasufumi

    2003-06-01

    Prompt neutron spectra for Cm-isotopes (242Cm, 243Cm, 244Cm, 245Cm, 246Cm, 248Cm) were calculated on the basis of a modified version of the Madland-Nix model combined with a multimodal fission model. The predicted spectra were found to be in fair agreement with recent data. A slight enhancement of the low-energy component of the spectrum was interpreted in terms of neutron emission during fragment acceleration.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  13. 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.

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

    SciTech Connect

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

    2010-10-15

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

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

    PubMed

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

    2011-11-01

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

  16. Measurement of neutron spectra in a silicon filtered neutron beam using stilbene detectors at the LVR-15 research reactor.

    PubMed

    Košťál, Michal; Šoltés, Jaroslav; Viererbl, Ladislav; Matěj, Zdeněk; Cvachovec, František; Rypar, Vojtěch; Losa, Evžen

    2017-10-01

    A well-defined neutron spectrum is an essential tool for calibration and tests of spectrometry and dosimetry detectors, and evaluation methods for spectra processing. Many of the nowadays used neutron standards are calibrated against a fission spectrum which has a rather smooth energy dependence. In recent time, at the LVR-15 research reactor in Rez, an alternative approach was tested for the needs of fast neutron spectrometry detector calibration. This process comprises detector tests in a neutron beam, filtered by one meter of single-crystalline silicon, which contains several significant peaks in the fast neutron energy range. Tests in such neutron field can possibly reveal specific problems in the deconvolution matrix of the detection system, which may stay hidden in fields with a smooth structure and can provide a tool for a proper energy calibration. Test with several stilbene scintillator crystals in two different beam configurations supplemented by Monte-Carlo transport calculations have been carried out. The results have shown a high level of agreement between the experimental data and simulation, proving thus the accuracy of used deconvolution matrix. The chosen approach can, thus, provide a well-defined neutron reference field with a peaked structure for further tests of spectra evaluation methods and scintillation detector energy calibration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Out-of-field neutron and leakage photon exposures and the associated risk of second cancers in high-energy photon radiotherapy: current status.

    PubMed

    Takam, R; Bezak, E; Marcu, L G; Yeoh, E

    2011-10-01

    Determination and understanding of out-of-field neutron and photon doses in accelerator-based radiotherapy is an important issue since linear accelerators operating at high energies (>10 MV) produce secondary radiations that irradiate parts of the patient's anatomy distal to the target region, potentially resulting in detrimental health effects. This paper provides a compilation of data (technical and clinical) reported in the literature on the measurement and Monte Carlo simulations of peripheral neutron and photon doses produced from high-energy medical linear accelerators and the reported risk and/or incidence of second primary cancer of tissues distal to the target volume. Information in the tables facilitates easier identification of (1) the various methods and measurement techniques used to determine the out-of-field neutron and photon radiations, (2) reported linac-dependent out-of-field doses, and (3) the risk/incidence of second cancers after radiotherapy due to classic and modern treatment methods. Regardless of the measurement technique and type of accelerator, the neutron dose equivalent per unit photon dose ranges from as low as 0.1 mSv/Gy to as high as 20.4 mSv/Gy. This radiation dose potentially contributes to the induction of second primary cancer in normal tissues outside the treated area.

  18. Measurement of the High Energy Neutron Flux on the Surface of the Natural Uranium Target Assembly QUINTA Irradiated by Deuterons of 4 and 8 GeV Energy

    NASA Astrophysics Data System (ADS)

    Adam, J.; Baldin, A. A.; Chilap, V.; Furman, W.; Katovsky, K.; Khushvaktov, J.; Kumar, V.; Pronskikh, V.; Mar'in, I.; Solnyshkin, A.; Suchopar, M.; Tsupko-Sitnikov, V.; Tyutyunnikov, S.; Vrzalova, J.; Wagner, V.; Zavorka, L.

    Experiments with the natural uranium target assembly "QUINTA" exposed to 4 and 8 GeV deuteron beams of the Nuclotron accelerator at the Joint Institute for Nuclear Research (Dubna) are analyzed. The reaction rates of 27Al(n,y1)24Na, 27Al(n,y2)22Na and 27Al(n,y3)7Be reactions with effective threshold energies of 5, 27, and 119 MeV were measured at both 4 GeV and 8 GeV deuteron beam energies. The average neutron fluxes between the effective threshold energies and the effective ends of the neutron spectra (which are 800 or 1000 MeV for 4 or 8 GeV deuterons) were determined. The evidence for the intensity shift of the neutron spectra to higher neutron energies with the increase of the deuteron energy from 4 GeV to 8 GeV was found from the ratios of the average neutron fluxes. The reaction rates and the average neutron fluxes were calculated with the MCNPX 2.7 code.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  1. Unfolding neutron spectra from simulated response of thermoluminescence dosimeters inside a polyethylene sphere using GRNN neural network

    NASA Astrophysics Data System (ADS)

    Lotfalizadeh, F.; Faghihi, R.; Bahadorzadeh, B.; Sina, S.

    2017-07-01

    Neutron spectrometry using a single-sphere containing dosimeters has been developed recently, as an effective replacement for Bonner sphere spectrometry. The aim of this study is unfolding the neutron energy spectra using GRNN artificial neural network, from the response of thermoluminescence dosimeters, TLDs, located inside a polyethylene sphere. The spectrometer was simulated using MCNP5. TLD-600 and TLD-700 dosimeters were simulated at different positions in all directions. Then the GRNN was used for neutron spectra prediction, using the TLDs' readings. Comparison of spectra predicted by the network with the real spectra, show that the single-sphere dosimeter is an effective instrument in unfolding neutron spectra.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

    Puchalska, Monika; Sihver, Lembit

    2015-06-21

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

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

    NASA Astrophysics Data System (ADS)

    Puchalska, Monika; Sihver, Lembit

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Appelbe, B.; Chittenden, J.

    2015-10-01

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

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

    SciTech Connect

    Appelbe, B. Chittenden, J.

    2015-10-15

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

  7. Scintillating Fiber Array Characterization and Alignment for Neutron Imaging using the High Energy X-ray (HEX) Facility

    SciTech Connect

    Buckles, R. A., Ali, Z. A., Cradick, J. R., Traille, A. J., Warthan, W. A.

    2009-09-04

    The Neutron Imager diagnostic at the National Ignition Facility (NIF) located at Lawrence Livermore National Laboratory (LLNL) will produce high-resolution, gated images of neutron-generating implosions. A similar pinhole imaging experiment (PINEX) diagnostic was recently deployed at the Z facility at Sandia National Laboratories (SNL). Both the SNL and LLNL neutron imagers use similar fiber array scintillators (BCF-99-555). Despite diverse resolution and magnification requirements, both diagnostics put significant onus on the scintillator spatial quality and alignment precision to maintain optimal point spread. Characterization and alignment of the Z-PINEX scintillator and imaging system were done at NSTec/Livermore Operations in 2009, and is currently underway for the NIF Neutron Imager.

  8. Intramolecular and intermolecular interactions in methyl substituted pentanes as revealed by high energy CH-stretching overtone spectra

    NASA Astrophysics Data System (ADS)

    Henry, Bryan R.; Mohammadi, M. Ali; Thomson, James A.

    1981-10-01

    The overtone spectra of pentane and 12 methyl substituted pentanes are measured in the liquid phase in the region of the pure local mode overtones corresponding to ΔvCH = 3, 4, 5, and 6. The local mode structure of the spectra is discussed. The local mode frequencies ωCH and diagonal local mode anharmonicities XCH for the methyl oscillators are obtained from an analysis of the spectra. The change in ωCH and XCH with increased methyl substitution is related to a barrier to large amplitude vibrational motion arising from steric crowding. The height of this barrier is obtained from dissociation energies calculated from ωCH and XCH by taking the local methyl CH stretching potential to be a Lippincott-Schroeder potential. The methyl steric interactions are described in terms of nonbonded Lennard-Jones and Morse potentials. The parameters for these nonbonded potentials are calculated from the barrier heights and structural information obtained from molecular models for their least strained conformations. These parameters are used to identify a positional dependence in methyl steric hindrance. Force constants evaluated from the nonbonded potentials are correlated with bulk liquid properties.

  9. MEASUREMENT OF THE HIGH ENERGY COMPONENT OF THE X-RAY SPECTRA INTHE VENUS ECR ION SOURCE

    SciTech Connect

    Leitner, Daniela; Benitez, Janilee Y.; Lyneis, Claude M.; Todd,Damon S.; Ropponen,Tommi; Ropponen,Janne; Koivisto, Hannu; Gammino, Santo

    2007-11-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for Nuclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental set-up to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular the collimation and background shielding can be problematic. In this paper we will discuss the experimental set-up for such a measurement, the energy calibration and background reduction, the correction for detector efficiency, the shielding of the detector and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power and heating frequency.

  10. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-03-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (Versatile ECR for NUclear Science), produce large amounts of x-rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet, adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different from that for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper, we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates depending on various ion source parameters, such as confinement fields, minimum B-field, rf power, and heating frequency.

  11. Introducing Nuclear Data Evaluations of Prompt Fission Neutron Spectra

    SciTech Connect

    Neudecker, Denise

    2015-06-17

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

  12. Multi-layer plastic scintillation detector for intermediate- and high-energy neutrons with n- γ discrimination capability

    NASA Astrophysics Data System (ADS)

    Yu, L.; Terashima, S.; Ong, H. J.; Chan, P. Y.; Tanihata, I.; Iwamoto, C.; Tran, D. T.; Tamii, A.; Aoi, N.; Fujioka, H.; Gey, G.; Sakaguchi, H.; Sakaue, A.; Sun, B. H.; Tang, T. L.; Wang, T. F.; Watanabe, Y. N.; Zhang, G. X.

    2017-09-01

    A new type of neutron detector, named Stack Structure Solid organic Scintillator (S4), consisting of multi-layer plastic scintillators with capability to suppress low-energy γ rays under high-counting rate has been constructed and tested. To achieve n- γ discrimination, we exploit the difference in the ranges of the secondary charged particles produced by the interactions of neutrons and γ rays in the scintillator material. The thickness of a plastic scintillator layer was determined based on the results of Monte Carlo simulations using the Geant4 toolkit. With layer thicknesses of 5 mm, we have achieved a good separation between neutrons and γ rays at 5 MeVee threshold setting. We have also determined the detection efficiencies using monoenergetic neutrons at two energies produced by the d + d → n+3He reaction. The results agree well with the Geant4 simulations implementing the Li e ̀ge Intranuclear Cascade hadronic model (INCL++) and the high-precision model of low-energy neutron interactions (NeutronHP).

  13. Seasonal redistribution of water in the surficial Martian regolith: Results from the Mars Odyssey high-energy neutron detector (HEND)

    NASA Astrophysics Data System (ADS)

    Kuzmin, R. O.; Zabalueva, E. V.; Mitrofanov, I. G.; Litvak, M. L.; Rodin, A. V.; Boynton, W. V.; Saunders, R. S.

    2007-04-01

    The seasonal variation of neutron emissions from Mars in different spectral intervals measured by the HEND neutron detector for the entire Martian year are analyzed. Based on these data, the spatial variations of the neutron emissions from the planet are globally mapped as a function of season, and the dynamics of seasonal variation of neutron fluxes with different energies is analyzed in detail. No differences were found between seasonal regimes of neutron fluxes in different energy ranges in the southern hemisphere of Mars, while the regime of fast neutrons (with higher energies) during the northern winter strongly differs from that during the southern winter. In winter ( L s = 270° 330°), the fast neutron fluxes are noticeably reduced in the northern hemisphere (along with the consecutive thickening of the seasonal cap of solid carbon dioxide). This provides evidence of a temporary increase in the water content in the effective layer of neutron generation. According to the obtained estimates, the observed reduction of the flux of fast neutrons in the effective layer corresponds to an increase in the water abundance of up to 5% in the seasonal polar cap (70° 90°N), about 3% at mid-latitudes, and from 1.5 to 2% at low latitudes. The freezing out of atmospheric water at the planetary surface (at middle and high latitudes) and the hydration of salt minerals composing the Martian soil are considered as the main processes responsible for the temporary increase in the water content in the soil and upper layer of the seasonal polar cap. The meridional atmospheric transport of water vapor from the summer southern to the winter northern hemisphere within the Hadley circulation cell is a basic process that delivers water to the subsurface soil layer and ensures the observed scale of the seasonal increase in water abundance. In the summer northern hemisphere, the similar Hadley circulation cell transports mainly dry air masses to the winter southern hemisphere. The

  14. Low-energy photons in high-energy photon fields--Monte Carlo generated spectra and a new descriptive parameter.

    PubMed

    Chofor, Ndimofor; Harder, Dietrich; Willborn, Kay; Rühmann, Antje; Poppe, Björn

    2011-09-01

    The varying low-energy contribution to the photon spectra at points within and around radiotherapy photon fields is associated with variations in the responses of non-water equivalent dosimeters and in the water-to-material dose conversion factors for tissues such as the red bone marrow. In addition, the presence of low-energy photons in the photon spectrum enhances the RBE in general and in particular for the induction of second malignancies. The present study discusses the general rules valid for the low-energy spectral component of radiotherapeutic photon beams at points within and in the periphery of the treatment field, taking as an example the Siemens Primus linear accelerator at 6 MV and 15 MV. The photon spectra at these points and their typical variations due to the target system, attenuation, single and multiple Compton scattering, are described by the Monte Carlo method, using the code BEAMnrc/EGSnrc. A survey of the role of low energy photons in the spectra within and around radiotherapy fields is presented. In addition to the spectra, some data compression has proven useful to support the overview of the behaviour of the low-energy component. A characteristic indicator of the presence of low-energy photons is the dose fraction attributable to photons with energies not exceeding 200 keV, termed P(D)(200 keV). Its values are calculated for different depths and lateral positions within a water phantom. For a pencil beam of 6 or 15 MV primary photons in water, the radial distribution of P(D)(200 keV) is bellshaped, with a wide-ranging exponential tail of half value 6 to 7 cm. The P(D)(200 keV) value obtained on the central axis of a photon field shows an approximately proportional increase with field size. Out-of-field P(D)(200 keV) values are up to an order of magnitude higher than on the central axis for the same irradiation depth. The 2D pattern of P(D)(200 keV) for a radiotherapy field visualizes the regions, e.g. at the field margin, where changes of

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

    SciTech Connect

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

    2005-11-15

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

  16. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy pp and pp¯ collisions

    DOE PAGES

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; ...

    2015-06-22

    Transverse spectra of both jets and hadrons obtained in high-energymore » $pp$ and $$p\\bar p $$ collisions at central rapidity exhibit power-law behavior of $$1/p_T^n$$ at high $$p_T$$. The power index $n$ is 4-5 for jet production and is slightly greater for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest $$p_T$$ region in $pp$ collisions at LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the dominance of the hard-scattering process over essentially the whole $$p_T$$ region at central rapidity in $pp$ collisions at LHC. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power index of UA1 jet spectra over an extended $$p_T$$ region and the two-particle correlation data of the STAR and PHENIX Collaborations in high-energy $pp$ and $$p \\bar p$$ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that can be cast into a single-particle non-extensive statistical mechanical distribution. Lastly, because of such a connection, the non-extensive statistical mechanical distribution can be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high energy $pp$ and $$p\\bar p$$ collisions.« less

  17. 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.

  18. High energy neutron response characteristics of a passive survey instrument for the determination of cosmic radiation fields in aircraft.

    PubMed

    Bartlett, D T; Tanner, R J; Hager, L G

    2002-01-01

    A passive survey instrument has been developed for the determination of cosmic radiation fields in aircraft. The instrument contains 30 TLDs and 36 PADC etched track detectors in order to obtain the required precision and an isotropic response. Two active electronic personal dosemeters are included to record the time profile of the field intensity. The instrument is robust and reliable, and is particularly useful to verify values of route doses based on calculations. The energy of the neutron component of the field to be determined extends to over 500 MeV, but with the majority of the dose equivalent below 200 MeV. The results are reported of measurements at Uppsala University and Physikalisch-Technische Bundesanstalt of the response characteristics of the instrument to quasi-monoenergetic neutrons in the energy range 60 to 180 MeV and for monoenergetic neutrons of energy from 70 keV to 14.7 MeV.

  19. 239Pu Prompt Fission Neutron Spectra Impact on a Set of Criticality and Experimental Reactor Benchmarks

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  20. Energy spectra of gamma rays, electrons, and neutrinos produced at proton-proton interactions in the very high energy regime

    SciTech Connect

    Kelner, S. R.; Aharonian, F. A.; Bugayov, V. V.

    2006-08-01

    We present new parameterizations of energy spectra of secondary particles, {pi} mesons, gamma rays, electrons, and neutrinos produced in inelastic proton-proton collisions. The simple analytical approximations based on simulations of proton-proton interactions using the public available SIBYLL code provide very good accuracy for energy distributions of secondary products in the energy range above 100 GeV. Generally, the recommended analytical formulas deviate from the simulated distributions within a few percent over a large range of x=E{sub i}/E{sub p}--the fraction of energy of the incident proton transferred to the secondaries. Finally, we describe an approximate procedure of continuation of calculations towards low energies, down to the threshold of {pi}-meson production.

  1. Accurate simulations of TEPC neutron spectra using Geant4

    NASA Astrophysics Data System (ADS)

    Taylor, G. C.; Hawkes, N. P.; Shippen, A.

    2015-11-01

    A Geant4 model of a tissue-equivalent proportional counter (TEPC) has been developed in which the calculated output spectrum exhibits unparalleled agreement with experiment for monoenergetic neutron fields at several energies below 20 MeV. The model uses the standard release of the Geant4 9.6 p2 code, but with a non-standard neutron cross section file as provided by Mendoza et al., and with the environment variable options recommended by the same authors. This configuration was found to produce significant improvements in the alpha-dominated region of the calculated response. In this paper, these improvements are presented, and the post-processing required to convert deposited energy into the number of ion pairs (which is the quantity actually measured experimentally) is discussed.

  2. Analyzing neutron time-of-flight spectra from the National Ignition Facility using moments

    NASA Astrophysics Data System (ADS)

    Hatarik, R.; Field, J.; Eckart, M.; Grim, G.; Hartouni, E. P.; Moore, A.; Munro, D.; Sayre, D.

    2016-10-01

    The neutron spectrum produced by an indirectly driven implosion at the National Ignition Facility (NIF) provides valuable insight into the performance of the capsule. There are four neutron time-of-flight (nTOF) spectrometers being used at the NIF which can simultaneously measure DD and DT fusion neutrons on NIF shots. The width of theses peaks have been traditionally associated with the temperature of the plasma, recent work shows that it has to be considered a combination of flow and temperature distributions. This leads to a deviation from a pure gaussian shape of a single temperature static plasma and the presence of higher order moments in the neutron spectrum. The current status of the analysis of neutron spectra from the nTOF diagnostics at the NIF will be presented. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Dual-energy contrast-enhanced digital mammography (DE-CEDM): optimization on digital subtraction with practical x-ray low/high-energy spectra

    NASA Astrophysics Data System (ADS)

    Chen, Biao; Jing, Zhenxue; Smith, Andrew P.; Parikh, Samir; Parisky, Yuri

    2006-03-01

    Dual-energy contrast enhanced digital mammography (DE-CEDM), which is based upon the digital subtraction of low/high-energy image pairs acquired before/after the administration of contrast agents, may provide physicians physiologic and morphologic information of breast lesions and help characterize their probability of malignancy. This paper proposes to use only one pair of post-contrast low / high-energy images to obtain digitally subtracted dual-energy contrast-enhanced images with an optimal weighting factor deduced from simulated characteristics of the imaging chain. Based upon our previous CEDM framework, quantitative characteristics of the materials and imaging components in the x-ray imaging chain, including x-ray tube (tungsten) spectrum, filters, breast tissues / lesions, contrast agents (non-ionized iodine solution), and selenium detector, were systemically modeled. Using the base-material (polyethylene-PMMA) decomposition method based on entrance low / high-energy x-ray spectra and breast thickness, the optimal weighting factor was calculated to cancel the contrast between fatty and glandular tissues while enhancing the contrast of iodized lesions. By contrast, previous work determined the optimal weighting factor through either a calibration step or through acquisition of a pre-contrast low/high-energy image pair. Computer simulations were conducted to determine weighting factors, lesions' contrast signal values, and dose levels as functions of x-ray techniques and breast thicknesses. Phantom and clinical feasibility studies were performed on a modified Selenia full field digital mammography system to verify the proposed method and computer-simulated results. The resultant conclusions from the computer simulations and phantom/clinical feasibility studies will be used in the upcoming clinical study.

  4. Deconvolution of charged particle spectra from neutron depth profiling using Simplex method

    NASA Astrophysics Data System (ADS)

    Hnatowicz, V.; Vacík, J.; Fink, D.

    2010-07-01

    Neutron depth profiling (NDP), based on neutron induced nuclear reactions, is a well known, nondestructive technique for the determination of the concentration depth profiles of some isotopes in the surface layers of solids. The profile determination consists of deconvolution of a relevant part of the energy spectra of the charged reaction products. Several solutions have been suggested for this problem. In this work, an alternative computer code (LIBOR), which makes use of the Simplex minimization technique for the deconvolution of the NDP spectra, is described and its performance is documented on several examples.

  5. Deconvolution of charged particle spectra from neutron depth profiling using Simplex method.

    PubMed

    Hnatowicz, V; Vacík, J; Fink, D

    2010-07-01

    Neutron depth profiling (NDP), based on neutron induced nuclear reactions, is a well known, nondestructive technique for the determination of the concentration depth profiles of some isotopes in the surface layers of solids. The profile determination consists of deconvolution of a relevant part of the energy spectra of the charged reaction products. Several solutions have been suggested for this problem. In this work, an alternative computer code (LIBOR), which makes use of the Simplex minimization technique for the deconvolution of the NDP spectra, is described and its performance is documented on several examples.

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

    NASA Astrophysics Data System (ADS)

    Recktenwald, Geoff; Deinert, Mark

    2010-03-01

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

  7. Impact of intermediate and high energy nuclear data on the neutronic safety parameters of MYRRHA accelerator driven system

    NASA Astrophysics Data System (ADS)

    Stankovskiy, Alexey; Çelik, Yurdunaz; Eynde, Gert Van den

    2017-09-01

    Perturbation of external neutron source can cause significant local power changes transformed into undesired safety-related events in an accelerator driven system. Therefore for the accurate design of MYRRHA sub-critical core it is important to evaluate the uncertainty of power responses caused by the uncertainties in nuclear reaction models describing the particle transport from primary proton energy down to the evaluated nuclear data table range. The calculations with a set of models resulted in quite low uncertainty on the local power caused by significant perturbation of primary neutron yield from proton interactions with lead and bismuth isotopes. The considered accidental event of prescribed proton beam shape loss causes drastic increase in local power but does not practically change the total core thermal power making this effect difficult to detect. In the same time the results demonstrate a correlation between perturbed local power responses in normal operation and misaligned beam conditions indicating that generation of covariance data for proton and neutron induced neutron multiplicities for lead and bismuth isotopes is needed to obtain reliable uncertainties for local power responses.

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

    SciTech Connect

    Remec, I.; Kam, F.B.

    1993-12-01

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

  9. Disentangling random thermal motion of particles and collective expansion of source from transverse momentum spectra in high energy collisions

    NASA Astrophysics Data System (ADS)

    Wei, Hua-Rong; Liu, Fu-Hu; Lacey, Roy A.

    2016-12-01

    In the framework of a multisource thermal model, we describe experimental results of the transverse momentum spectra of final-state light flavor particles produced in gold-gold (Au-Au), copper-copper (Cu-Cu), lead-lead (Pb-Pb), proton-lead (p-Pb), and proton-proton (p -p) collisions at various energies, measured by the PHENIX, STAR, ALICE, and CMS Collaborations, by using the Tsallis-standard (Tsallis form of Fermi-Dirac or Bose-Einstein), Tsallis, and two- or three-component standard distributions which can be in fact regarded as different types of ‘thermometers’ or ‘thermometric scales’ and ‘speedometers’. A central parameter in the three distributions is the effective temperature which contains information on the kinetic freeze-out temperature of the emitting source and reflects the effects of random thermal motion of particles as well as collective expansion of the source. To disentangle both effects, we extract the kinetic freeze-out temperature from the intercept of the effective temperature (T) curve as a function of particle’s rest mass (m 0) when plotting T versus m 0, and the mean transverse flow velocity from the slope of the mean transverse momentum (< {p}T> ) curve as a function of mean moving mass (\\overline{m}) when plotting < {p}T> versus \\overline{m}.

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

    SciTech Connect

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

    2015-01-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  13. Computation and inversion of ion spectra for neutron depth profiling of curved surfaces

    NASA Astrophysics Data System (ADS)

    Shultis, J. Kenneth

    2004-07-01

    Neutron depth profiling (NDP) is a nondestructive technique for determining the concentration of special isotopes within several microns of a sample's surface. Previous NDP analyses, however, have been restricted to samples with plane surfaces. Here samples with curved surfaces are considered. In particular, a method for estimating the energy spectrum of ions emitted from curved surfaces is presented. Also, a robust method for inverting the NDP ion energy spectra is presented that yields accurate concentration profiles for both under- and overdetermined NDP spectra.

  14. Results of monte carlo calculations of neutron spectra and doses outside the BDMS shielding

    SciTech Connect

    Radev, R P; Hall, J M

    2000-10-16

    A set of Monte Carlo calculations of the neutron dose rates and neutron spectra outside Blend Down Monitoring System (BDMS) shielding were performed with U.S. and Russian neutron fluence-to-dose conversion coefficients. The purpose of these calculations was to facilitate the proper interpretation of the dose rate measurements from rem meters outside the BDMS shielding. An accurate determination of the dose rate is of particular interest so that dose rate can be compared with the applicable regulatory limit. The calculations show that the neutrons outside the BDMS shielding are significantly reduced in energy, i.e. the spectrum is shifted (moderated) towards the lower energies and contains significantly larger amount of neutrons in the energy range below 100 keV. The result of these calculations indicates that the dose measurement for the BDMS neutrons is overestimated from 25% to 55% depending on the location around BDMS when using either Russian or U.S. dose conversion coefficients. For an accurate neutron dose determination the application of an appropriate correcting factor to the neutron dose measurement is necessary.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  17. Measurement and Analysis of Neutron Leakage Spectra from Pb and LBE Cylinders with D-T Neutrons

    NASA Astrophysics Data System (ADS)

    Chen, Size; Gan, Leting; Li, Taosheng; Han, Yuncheng; Liu, Chao; Jiang, Jieqiong; Wu, Yican

    2017-09-01

    For validating the current evaluated neutron data libraries, neutron leakage spectra from lead and lead bismuth eutectic (LBE) cylinders have been measured using an intense D-T pulsed neutron source with time-of-flight (TOF) method by Institute of Nuclear Energy Safety Technology (INEST), Chinese Academy of Sciences (CAS). The measured leakage spectra have been compared with the calculated ones using Super Monte Carlo Simulation Program for Nuclear and Radiation Process (SuperMC) with the evaluated pointwise data of lead and bismuth processed from ENDF/B-VII.1, JEFF-3.1 and JENDL-4.0 libraries. This work shows that calculations of the three libraries are all generally consistent with the lead experimental result. For LBE experiment, the JEFF-3.1 and JENDL-4.0 calculations both agree well with the measurement. However, the result of ENDF/B-VII.1 fails to fit with the measured data, especially in the energy range of 5.5 and 7 MeV with difference more than 80%. Through sensitivity analysis with partial cross sections of 209Bi in ENDF/B-VII.1 and JEFF, the difference between the measurement and the ENDF/B-VII.1 calculation in LBE experiment is found due to the neutron data of 209Bi.

  18. Search for Sources of High-energy Neutrons with Four Years of Data from the IceTop Detector

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glagla, M.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, B.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Holzapfel, K.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Jurkovic, M.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kemp, J.; Kheirandish, A.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Leuner, J.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Meli, A.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Mohrmann, L.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schimp, M.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stahlberg, M.; Stanev, T.; Stasik, A.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stössl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Turcati, A.; Unger, E.; Usner, M.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Veenkamp, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Weaver, Ch.; Weiss, M. J.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; IceCube Collaboration

    2016-10-01

    IceTop is an air-shower array located on the Antarctic ice sheet at the geographic South Pole. IceTop can detect an astrophysical flux of neutrons from Galactic sources as an excess of cosmic-ray air showers arriving from the source direction. Neutrons are undeflected by the Galactic magnetic field and can typically travel 10 (E/PeV) pc before decay. Two searches are performed using 4 yr of the IceTop data set to look for a statistically significant excess of events with energies above 10 PeV (1016 eV) arriving within a small solid angle. The all-sky search method covers from -90° to approximately -50° in declination. No significant excess is found. A targeted search is also performed, looking for significant correlation with candidate sources in different target sets. This search uses a higher-energy cut (100 PeV) since most target objects lie beyond 1 kpc. The target sets include pulsars with confirmed TeV energy photon fluxes and high-mass X-ray binaries. No significant correlation is found for any target set. Flux upper limits are determined for both searches, which can constrain Galactic neutron sources and production scenarios.

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

    PubMed

    Rivard, Mark J; Zamenhof, Robert G

    2004-11-01

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

  20. Neutron spectra and dose-rate measurements around a transport cask for spent reactor fuel

    NASA Astrophysics Data System (ADS)

    Rimpler, Arndt

    1997-02-01

    A storage facility with a capacity of 420 containers is available for the interim storage of spent fuel from power reactors at the village of Gorleben in Germany. During transportation and storage of spent fuel casks radiation exposure of the personnel is dominated by neutrons. The routine control of the dose rate limits according to the transport regulations and the licence of the storage facility is performed with conventional neutron survey meters. These monitors, calibrated for fast neutrons at radionuclide neutron sources, usually overestimate the real dose rate in unknown neutron fields. In this paper, a series of measurements with several monitoring instruments near a transport cask of the CASTOR type is presented. The results are compared with reference data for the does equivalents calculated from the measured fluence spectra using a Bonner multisphere spectrometer. Besides reliable information about neutron spectra and dose rates at the container, it was found that some of the rem counters overestimate the true dose rate by a factor of 2 or more.

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

    SciTech Connect

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

    2015-01-20

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

  2. Transmutation characteristics in thermal and fast neutron spectra: application to americium

    NASA Astrophysics Data System (ADS)

    Berthou, V.; Degueldre, C.; Magill, J.

    2003-07-01

    In this paper, a method is introduced which allows a quick and accurate evaluation of the overall transmutation rate of a nuclide in fast and thermal neutron spectra. The method is applied to 241Am, a main contributor to the waste toxicity in the nuclear fuel cycle. Results show good agreement with the detailed calculations using ORIGEN code.

  3. Analysis of neutron noise spectra using neural networks

    SciTech Connect

    Korsah, K. ); Uhrig, R.E. Tennessee Univ., Knoxville, TN )

    1991-01-01

    Neural network architectures based on the back-propagation paradigm have been developed to recognize the features, and detect resonance shifts in, power spectral density (PSD) data. Our goal is to advance the state of the art in the application of noise analysis techniques to monitor nuclear reactor internals. The initial objectives have been to use PSD data, acquired over a period of about 2 years by PSDREC (power spectral density recognition system), to develop neural networks that are able to differentiate between normal neutron power spectral density data and anomalous spectral data, and detect significant shifts in the positions of spectral resonances while reducing the effect of small shifts. Neural network systems referred to in this paper as spectral feature detectors (SFDs) and integral network filters have been developed to meet these objectives. The performance of the SFDs is the subject of this paper. 2 refs., 2 figs.

  4. Application of low-cost Gallium Arsenide light-emitting-diodes as kerma dosemeter and fluence monitor for high-energy neutrons.

    PubMed

    Mukherjee, B; Simrock, S; Khachan, J; Rybka, D; Romaniuk, R

    2007-01-01

    Displacement damage (DD) caused by fast neutrons in unbiased Gallium Arsenide (GaAs) light emitting diodes (LED) resulted in a reduction of the light output. On the other hand, a similar type of LED irradiated with gamma rays from a (60)Co source up to a dose level in excess of 1.0 kGy (1.0 x 10(5) rad) was found to show no significant drop of the light emission. This phenomenon was used to develop a low cost passive fluence monitor and kinetic energy released per unit mass dosemeter for accelerator-produced neutrons. These LED-dosemeters were used to assess the integrated fluence of photoneutrons, which were contaminated with a strong bremsstrahlung gamma-background generated by the 730 MeV superconducting electron linac driving the free electron laser in Hamburg (FLASH) at Deutsches Elektronen-Synchrotron. The applications of GaAs LED as a routine neutron fluence monitor and DD precursor for the electronic components located in high-energy accelerator environment are highlighted.

  5. Calculation of Neutron Production Rates and Spectra from Compounds of Actinides and Light Elements

    NASA Astrophysics Data System (ADS)

    Vlaskin, Gennady; Khomiakov, Yuriy

    2017-09-01

    The code NEDIS allows the calculation of neutron production rate and continuous energy spectra due to (α,n) reaction on Li, Be, B, C, O, F, Ne, Na Mg, Al, Si, P, S, Cl, Ar, K, and Ca. It accounts for anisotropic angular distribution of neutrons of (α,n) reaction in centre-of- mass system and dimensions of alpha emitting source material particles. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, ν- averaged per fission, and Watt spectrum parameters. The results of calculations by NEDIS can be used as input for Monte Carlo simulation for materials that will be used in radiation shielding and for underground neutron experiments

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

    SciTech Connect

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

    2013-07-14

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

  7. Measurement of activation cross-sections for high-energy neutron-induced reactions of Bi and Pb

    NASA Astrophysics Data System (ADS)

    Zaman, Muhammad; Kim, Guinyun; Kim, Kwangsoo; Naik, Haladhara; Shahid, Muhammad; Lee, Manwoo

    2015-08-01

    The cross-sections for 209Bi(n, 4n)206Bi, 209Bi(n, 5n)205Bi, natPb(n, xn)204mPb, natPb(n, xn)203Pb, natPb(n, xn)202mPb,natPb(n, xn)201Pb, natPb(n, xn)200Pb, natPb(n, αxn)203Hg and natPb(n, p xn)202Tl reactions were determined at the Korean Institute of Radiological and Medical Sciences (KIRAMS), Korea in the neutron energy range of 15.2 to 37.2 MeV. The above cross-sections were obtained by using the activation and off-line γ-ray spectrometric technique. The quasi-monoenergetic neutron used for the above reactions are based on the 9Be(p, n) reaction. Simulations of the spectral flux from the Be target were done using the MCNPX program. The cross-sections were estimated with the TALYS 1.6 code using the default parameter. The data from the present work and literature were compared with the data from the EAF-2010 and the TENDL-2013 libraries, and calculated values of TALYS 1.6 code. It shows that appropriate level density model, the γ-ray strength function, and the spin cut-off parameter are needed to obtain a good agreement between experimental data and theoretical values from TALYS 1.6 code.

  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. Neutron energy spectra unfolding from foil activation detector measurements with MINUIT

    NASA Astrophysics Data System (ADS)

    Seghour, A.; Seghour, F. Z.

    2005-12-01

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

  10. Modeling of spectral features in the dynamic spectra of neutron stars

    NASA Astrophysics Data System (ADS)

    Garasyov, M. A.; Derishev, E. V.; Kocharovsky, Vl. V.

    2011-10-01

    Modeling of atomic and cyclotron lines in the emergent spectra of rotating neutron stars with various distributions of temperature over the star surface is carried out. General and special relativity effects are taken into account in the radiation transfer calculations. A novel method of analysis based on the Fourier series expansion of the observed spectra over rotation frequencies is proposed. It is shown that the mutual influence of the gravitational bending of light rays and rotation of the star leads to the formation of strong features (sometimes several features at once) in the Fourier-harmonic spectrum, whereas these features remain almost invisible in both the integrated and dynamic spectra. Possible application of the obtained results to the interpretation of absorption features in the spectrum of the single neutron star 1E 1207.4 - 5209 is discussed.

  11. An integral test of the inelastic cross sections of Pb and Mo using measured neutron spectra

    NASA Technical Reports Server (NTRS)

    Shook, D. F.; Fieno, D.; Ford, C. H.; Wrights, G. N.

    1972-01-01

    Comparison of measurements and calculations of fast neutron spectra from a radioactive neutron source inside spheres of Mo or Pb and from a cylindrical reactor containing a thick Pb or Mo reflector are used as a test of ENDF cross sections. The sphere leakage spectra were measured at a sphere-to-spectrometer distance of 2 meters using a 54 Ci spherical Am-Be neutron source. Reactor leakage spectrum measurements were made at the surface of the ZP-1 reactor when bare, with a Pb radial reflector 21 cm thick, and with a metallic Mo radial reflector 10 cm thick. In the case of the thin Mo sphere there is agreement between the calculation and measurement. The Pb calculation is much lower than the measurement except at the highest neutron energy. Two-dimensional calculations of reactor spectra result indicate that the reactor source is reasonably well known. Significant differences in leakage spectrum shape for both Mo and Pb reflectors suggest that there are large uncertainties in the inelastic cross sections for Pb and some for Mo.

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

    SciTech Connect

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

    2005-05-24

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

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

    PubMed

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

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  15. Anharmonicity and disorder in simple and complex perovskites: a high energy synchrotron and hot neutron diffraction study

    NASA Astrophysics Data System (ADS)

    Kiat, Jean-Michel; Baldinozzi, Gianguido; Dunlop, Muriel; Malibert, Charlotte; Dkhil, Brahim; Ménoret, Carole; Masson, Olivier; Fernandez-Diaz, Maria-Teresa

    2000-10-01

    We report a study of simple ABO3 type perovskites BaTiO3, PbTiO3, KNbO3, SrTiO3 and the relaxor perovskites PbSc1/2Nb1/2O3 (PSN) in their cubic phase using hard synchrotron radiation and hot neutrons. Gram-Charlier expansions of the thermal parameters have been performed and have revealed interesting features about the probability density function and the one-particle potential of the different atoms. This description is compared with other descriptions in terms of the split atom model and in terms of the rotator model. Structural trends regarding the order-disorder versus displacive character of the phase transitions have been obtained. It is concluded that SrTiO3 and BaTiO3 are quasi-harmonic systems whereas KNbO3 shows weak anharmonicity and PbTiO3 and PSN display strong anharmonic features.

  16. Neutron Generation from Laser-Accelerated Ion Beams: Use of Alternative Deuteron-Rich Targets for Improved Neutron Yield and Control of Neutron Spectra

    NASA Astrophysics Data System (ADS)

    Albright, B. J.; Yin, L.; Favalli, A.

    2016-10-01

    Laser-ion-beam generation in the break-out afterburner (BOA) acceleration regime has been modeled for several deuteron-rich solid-density targets using the VPIC particle-in-cell code. Monte Carlo modeling of the transport of these beams in a beryllium converter in a pitcher-catcher neutron source configuration shows significant increases in neutron yields may be achievable through judicious choices of laser target material. Additionally, species-separation dynamics in some target materials during the BOA ion acceleration phase can be exploited to control the shapes of the neutron spectra. Work performed under the auspices of the U.S. DOE by the LANS, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396. Funding provided by the Los Alamos National Laboratory Directed Research and Development Program.

  17. Fission foil detector calibrations with high energy protons

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.

    1995-01-01

    Fission foil detectors (FFD's) are passive devices composed of heavy metal foils in contact with muscovite mica films. The heavy metal nuclei have significant cross sections for fission when irradiated with neutrons and protons. Each isotope is characterized by threshold energies for the fission reactions and particular energy-dependent cross sections. In the FFD's, fission fragments produced by the reactions are emitted from the foils and create latent particle tracks in the adjacent mica films. When the films are processed surface tracks are formed which can be optically counted. The track densities are indications of the fluences and spectra of neutrons and/or protons. In the past, detection efficiencies have been calculated using the low energy neutron calibrated dosimeters and published fission cross sections for neutrons and protons. The problem is that the addition of a large kinetic energy to the (n,nucleus) or (p,nucleus) reaction could increase the energies and ranges of emitted fission fragments and increase the detector sensitivity as compared with lower energy neutron calibrations. High energy calibrations are the only method of resolving the uncertainties in detector efficiencies. At high energies, either proton or neutron calibrations are sufficient since the cross section data show that the proton and neutron fission cross sections are approximately equal. High energy proton beams have been utilized (1.8 and 4.9 GeV, 80 and 140 MeV) for measuring the tracks of fission fragments emitted backward and forward.

  18. Fission foil detector calibrations with high energy protons

    SciTech Connect

    Benton, E.V.; Frank, A.L.

    1995-03-01

    Fission foil detectors (FFD`s) are passive devices composed of heavy metal foils in contact with muscovite mica films. The heavy metal nuclei have significant cross sections for fission when irradiated with neutrons and protons. Each isotope is characterized by threshold energies for the fission reactions and particular energy-dependent cross sections. In the FFD`s, fission fragments produced by the reactions are emitted from the foils and create latent particle tracks in the adjacent mica films. When the films are processed surface tracks are formed which can be optically counted. The track densities are indications of the fluences and spectra of neutrons and/or protons. In the past, detection efficiencies have been calculated using the low energy neutron calibrated dosimeters and published fission cross sections for neutrons and protons. The problem is that the addition of a large kinetic energy to the (n,nucleus) or (p,nucleus) reaction could increase the energies and ranges of emitted fission fragments and increase the detector sensitivity as compared with lower energy neutron calibrations. High energy calibrations are the only method of resolving the uncertainties in detector efficiencies. At high energies, either proton or neutron calibrations are sufficient since the cross section data show that the proton and neutron fission cross sections are approximately equal. High energy proton beams have been utilized (1.8 and 4.9 GeV, 80 and 140 MeV) for measuring the tracks of fission fragments emitted backward and forward.

  19. In situ high-energy X-ray diffraction study of tensile deformation of neutron-irradiated polycrystalline Fe-9%Cr alloy

    SciTech Connect

    Zhang, Xuan; Li, Meimei; Park, Jun -Sang; Kenesei, Peter; Almer, Jonathan; Xu, Chi; Stubbins, James F.

    2016-12-30

    The effect of neutron irradiation on tensile deformation of a Fe-9wt.%Cr alloy was investigated using in situ high-energy synchrotron X-ray diffraction during room-temperature uniaxial tensile tests. New insights into the deformation mechanisms were obtained through the measurements of lattice strain evolution and the analysis of diffraction peak broadening using the modified Williamson-Hall method. Two neutron-irradiated specimens, one irradiated at 300 °C to 0.01 dpa and the other at 450 °C to 0.01dpa, were tested along with an unirradiated specimen. The macroscopic stress–strain curves of the irradiated specimens showed increased strength, reduced ductility and work-hardening exponent compared to the unirradiated specimen. The evolutions of the lattice strain, the dislocation density and the coherent scattering domain size in the deformation process revealed different roles of the submicroscopic defects in the 300°C/0.01 dpa specimen and the TEM-visible nanometer-sized dislocation loops in the 450°C/0.01 dpa specimen: submicroscopic defects extended the linear work hardening stage (stage II) to a higher strain, while irradiation-induced dislocation loops were more effective in dislocation pinning. Lastly, while the work hardening rate of stage II was unaffected by irradiation, significant dynamic recovery in stage III in the irradiated specimens led to the early onset of necking without stage IV as observed in the unirradiated specimen.

  20. High energy x-ray and neutron studies of disordered energy-related materials at extreme conditions

    SciTech Connect

    Parise, John

    2016-05-16

    The fundamental scientific accomplishments are: (1) advances in a general description of the liquid state by employing structural models constrained by measurements to interpret experimental results and extend them to liquids in general, with special emphasis on (2) The structure of the high-temperature crystal and molten UO2 and 3) water. Specifically, samples of UO2 and water were probed using high-energy x-rays at the Advanced Photon Source. The high Z of UO2, and the 2-3mm diameter droplet shape of the molten sample, means that >100keV X-rays are required to minimize absorption and multiple scattering, which can distort the measured structure factor. A high flux of x-rays is also required to obtain sufficient statistical accuracy in short (a few seconds) measurement times. The scattered x-ray data were analyzed and pair distribution functions, extracted that characterize the local and long-range atomic structure of the material. The measurements of the hot UO2 solid show a substantial increase in oxygen disorder and, upon melting, the average U-O coordination was found to decrease from 8 to 6.7±0.5. The research incorporated development of diffraction techniques, sample environment optimization and state-of-the-art simulation techniques. The symbiotic nature of the advances in simulation and experiment allowed for a more focused and informed development of future experiments, effective use of expensive beam time and generated new research agendas for the growing number of research groups, within the US and internationally, that focus on the structure of liquids. Molecular dynamics (MD) provided detailed information when combined with high-quality XN data including addressing key issues in liquids; the relationship between cooling path, structure and fictive temperature, and the trade-offs between network over connectedness in liquids containing low-coordination cations.

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

    SciTech Connect

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

    1999-03-01

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

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

    SciTech Connect

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

    2012-10-23

    Spectra of photons and neutrons were calculated, using the Monte Carlo code MCNP-5 using the e/p/n mode. A heterogeneous model was used to define the linac head where the collimators were modeled to produce five different treatment fields at the isocenter. Photon and neutron spectra were estimated in several points along two directions from the isocenter. The total photon fluence beyond 60 cm behaves according to 1/r{sup 2} rule, while total neutron fluence, beyond 80 cm, can be described by diffusion theory using an infinite plane as a neutron source.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    SciTech Connect

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

    2012-10-15

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

  5. Total π+p cross section extracted from the leading neutron spectra at the LHC

    NASA Astrophysics Data System (ADS)

    Khoze, V. A.; Martin, A. D.; Ryskin, M. G.

    2017-08-01

    We use the very forward neutron energy spectra measured by the LHC forward experiment at 7 TeV to extract the π+p total cross section at center-of-mass energies in the range 2.3 - 3.5 TeV . To do this, we have to first isolate the π -exchange pole in forward neutron production in p p collisions, by evaluating other possible contributions, namely, those from ρ and a2 exchange, from both eikonal and enhanced screening effects, from migration, from neutron production by Δ -isobar decay and from diffractive nucleon excitations. We discuss the possible theoretical uncertainties due to the fact that the data do not exactly reach the π pole. We choose the kinematical domain where the pion contribution dominates and demonstrate the role of the different corrections which could affect the final result.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

  7. Total pion-proton cross section from the new LHCf data on leading neutrons spectra

    NASA Astrophysics Data System (ADS)

    Ryutin, R. A.

    2017-02-01

    In the light of the latest data by the LHCf collaboration of the LHC on leading neutrons spectra it is possible to obtain total pion-proton cross sections in the TeV energy region. In this work the exact extraction procedure is shown. Final results for the pion-proton cross section are collected at several different values of the colliding energy and compared with some popular theoretical predictions. The errors of the results are estimated.

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

    PubMed

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

    2016-10-01

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

  9. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    DOE PAGES

    Wakimoto, S.; Ishii, K.; Kimura, H.; ...

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with themore » previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.« less

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

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

    SciTech Connect

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

    1987-12-01

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

  12. The optimization of gamma spectra processing in prompt gamma neutron activation analysis (PGNAA)

    NASA Astrophysics Data System (ADS)

    Pinault, Jean-Louis; Solis, Jose

    2009-04-01

    The uncertainty of the elemental analysis is one of the major factors governing the utility of on-line Prompt Gamma Neutron Activation Analysis (PGNAA) in the blending and sorting of bulk materials. In this paper, a general method applicable to Gamma spectra processing is presented and applied to PGNAA in mineral industry. Based on the Fourier transform of spectra and their de-correlation in the Fourier space (the improvement of the conditioning of the correlation matrix), processing of overlapping of characteristic peaks minimizes the propagation of random errors, which optimizes the accuracy and decreases the detection limits of elemental analyses. In comparison with classical methods based on the linear combinations of relevant regions of spectra the improvement may be considerable, especially when several elements are interfering. The method is applied to four case stories covering both borehole logging and on-line analysis on conveyor belt of raw materials.

  13. In situ high-energy X-ray diffraction study of tensile deformation of neutron-irradiated polycrystalline Fe-9%Cr alloy

    DOE PAGES

    Zhang, Xuan; Li, Meimei; Park, Jun -Sang; ...

    2016-12-30

    The effect of neutron irradiation on tensile deformation of a Fe-9wt.%Cr alloy was investigated using in situ high-energy synchrotron X-ray diffraction during room-temperature uniaxial tensile tests. New insights into the deformation mechanisms were obtained through the measurements of lattice strain evolution and the analysis of diffraction peak broadening using the modified Williamson-Hall method. Two neutron-irradiated specimens, one irradiated at 300 °C to 0.01 dpa and the other at 450 °C to 0.01dpa, were tested along with an unirradiated specimen. The macroscopic stress–strain curves of the irradiated specimens showed increased strength, reduced ductility and work-hardening exponent compared to the unirradiated specimen.more » The evolutions of the lattice strain, the dislocation density and the coherent scattering domain size in the deformation process revealed different roles of the submicroscopic defects in the 300°C/0.01 dpa specimen and the TEM-visible nanometer-sized dislocation loops in the 450°C/0.01 dpa specimen: submicroscopic defects extended the linear work hardening stage (stage II) to a higher strain, while irradiation-induced dislocation loops were more effective in dislocation pinning. Lastly, while the work hardening rate of stage II was unaffected by irradiation, significant dynamic recovery in stage III in the irradiated specimens led to the early onset of necking without stage IV as observed in the unirradiated specimen.« less

  14. The effects of magnetic field topology on secondary neutron spectra in Magnetized Liner Inertial Fusion

    NASA Astrophysics Data System (ADS)

    Appelbe, B.; Pecover, J.; Chittenden, J.

    2017-03-01

    The Magnetized Liner Inertial Fusion (MagLIF) concept involves the compression of a magnetized fuel such that the stagnated fuel contains a magnetic field that can suppress heat flow losses and confine α particles. Magnetic confinement of α particles reduces the fuel ρR required for ignition. Recent work [1,2] has demonstrated that the magnitude of the magnetic field in deuterium fuel can be inferred from the yields and spectra of secondary DT neutrons. In this work we investigate the potential for using the shape of the secondary neutron spectra to diagnose the magnetic field topology in the stagnated fuel. Three different field topologies that could possibly occur in MagLIF experiments are studied: (1) a cylindrical fuel column containing axial and azimuthal magnetic field components, (2) a fuel column which is pinched at the ends to form a magnetic mirror and (3) a fuel column that has a helical tube shape with magnetic field lines following the helical path of the tube's axis. Each topology is motivated by observations from experimental or simulated MagLIF data. For each topology we use a multi-physics model to investigate the shapes of the secondary neutron spectra emitted from a steady-state stagnated fuel column. It is found that the azimuthal and helical topologies are more suitable than the mirror topology for reproducing an asymmetry in the axial spectra that was observed in experiments. Gorgon MHD simulations of the MagLIF implosion in 1D are also carried out. These show that sufficient azimuthal magnetic field can penetrate from the liner into the fuel to qualitatively reproduce the observed spectral asymmetry.

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

    SciTech Connect

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

    2009-01-21

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

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

    PubMed

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

    2005-09-01

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

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

    SciTech Connect

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

    2009-03-15

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

  18. Flare physics at high energies

    NASA Technical Reports Server (NTRS)

    Ramaty, R.

    1990-01-01

    High-energy processes, involving a rich variety of accelerated particle phenomena, lie at the core of the solar flare problem. The most direct manifestation of these processes are high-energy radiations, gamma rays, hard X-rays and neutrons, as well as the accelerated particles themselves, which can be detected in interplanetary space. In the study of astrophysics from the moon, the understanding of these processes should have great importance. The inner solar system environment is strongly influenced by activity on the sun; the physics of solar flares is of great intrinsic interest; and much high-energy astrophysics can be learned from investigations of flare physics at high energies.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Seghour, A.; Seghour, F. Z.

    2001-01-01

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

  1. Comparison of measured and calculated neutron and gamma-ray energy spectra behind an in-line shielded duct

    SciTech Connect

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

    1982-05-01

    Integral experiments that measure the transport of approx. 14 MeV neutrons through a 0.30-m-diameter duct having a length-to-diameter ratio of 2.83 that is partially plugged with a 0.15 m diameter, 0.51 m long shield comprised of alternating layers of stainless steel type 304 and borated polyethylene have been carried out at the Oak Ridge National Laboratory. Measured and calculated neutron and gamma ray energy spectra are compared at several locations relative to the mouth of the duct. The measured spectra were obtained using an NE-213 liquid scintillator detector with pulse shape discrimination methods used to simultaneously resolve neutron and gamma ray events. The calculated spectra were obtained using a computer code network that incorporates two radiation transport methods: discrete ordinates (with P/sub 3/ multigroup cross sections) and Monte Carlo (with continuous point cross sections). The two radiation transport methods are required to account for neutrons that singly scatter from the duct to the detectors. The calculated and measured neutron energy spectra above 850 keV agree with 5 to 50% depending on detector location and neutron energy. The calculated and measured gamma ray energy spectra above 750 keV are also in favorable agreement, approx. 5 to 50%, depending on detector location and gamma ray energy.

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

    PubMed

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

    2016-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  4. Stabilization of prompt gamma-ray neutron activation analysis (PGNAA) spectra from NaI detectors

    NASA Astrophysics Data System (ADS)

    Metwally, W. A.; Gardner, R. P.

    2004-06-01

    NaI detectors are still used frequently in industrial Prompt Gamma-Ray Neutron Activation Analysis applications such as in bulk material analysis. They have the advantages of being efficient for high-energy gamma rays, being relatively rugged, and being able to be used without cooling. When using NaI detectors, and consequently photomultiplier tubes, the quality of the data can drastically deteriorate through gain and zero shifts that result in spectral smearing due to temperature and/or counting rate changes. A new offline approach is presented to stabilize the NaI spectral drift. The approach is not sensitive to the cause of the drift and takes into account the NaI and ADC non-linearities. Peak resolution is improved substantially when this approach is used in the presence of spectral drift.

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

    SciTech Connect

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

    2013-01-01

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

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

    SciTech Connect

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

    2013-06-15

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

  7. Observations of high-energy radiation during thunderstorms at Tien-Shan

    NASA Astrophysics Data System (ADS)

    Gurevich, A. V.; Almenova, A. M.; Antonova, V. P.; Chubenko, A. P.; Karashtin, A. N.; Kryakunova, O. N.; Lutsenko, V. Yu.; Mitko, G. G.; Ptitsyn, M. O.; Piscal, V. V.; Ryabov, V. A.; Salikhov, N. M.; Sadykov, T. Kh.; Shepetov, A. L.; Shlyugaev, Yu. V.; Thu, W. M.; Vil'danova, L. I.; Zastrozhnova, N. N.; Zybin, K. P.

    2016-07-01

    Energetic radiation during thunderstorms is studied. The possibility to identify the high-energy lightning emission in the 10 s monitoring mode is demonstrated. Simultaneous measurements of gamma-ray emission, high-energy electrons, and neutron radiation in the triggering mode are fulfilled. Energy spectra of gamma emission and electrons are obtained. The intensity both of electrons and gamma rays in lightning discharge prevail the background emission by 1.5 to 2 orders of magnitude.

  8. A New Method for the Reconstruction of Very-High-Energy Gamma-Ray Spectra and Application to Galactic Cosmic-Ray Accelerators

    NASA Astrophysics Data System (ADS)

    Fernandes, Milton Virgílio

    2014-06-01

    In this thesis, high-energy (HE; E > 0.1 GeV) and very-high-energy (VHE; E > 0.1 TeV) γ-ray data were investigated to probe Galactic stellar clusters (SCs) and star-forming regions (SFRs) as sites of hadronic Galactic cosmic-ray (GCR) acceleration. In principle, massive SCs and SFRs could accelerate GCRs at the shock front of the collective SC wind fed by the individual high-mass stars. The subsequently produced VHE γ rays would be measured with imaging air-Cherenkov telescopes (IACTs). A couple of the Galactic VHE γ-ray sources, including those potentially produced by SCs, fill a large fraction of the field-of-view (FoV) and require additional observations of source-free regions to determine the dominant background for a spectral reconstruction. A new method of reconstructing spectra for such extended sources without the need of further observations is developed: the Template Background Spectrum (TBS). This methods is based on a method to generate skymaps, which determines background in parameter space. The idea is the creation of a look-up of the background normalisation in energy, zenith angle, and angular separation and to account for possible systematics. The results obtained with TBS and state-of-the-art background-estimation methods on H.E.S.S. data are in good agreement. With TBS even those sources could be reconstructed that normally would need further observations. Therefore, TBS is the third method to reconstruct VHE γ-ray spectra, but the first one to not need additional observations in the analysis of extended sources. The discovery of the largest VHE γ-ray source HESS J1646-458 (2.2° in size) towards the SC Westerlund 1 (Wd 1) can be plausibly explained by the SC-wind scenario. But owing to its size, other alternative counterparts to the TeV emission (pulsar, binary system, magnetar) were found in the FoV. Therefore, an association of HESS J1646-458 with the SC is favoured, but cannot be confirmed. The SC Pismis 22 is located in the centre of

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

    SciTech Connect

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

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

    DOE PAGES

    Rusev, G.; Jandel, M.; Arnold, C. W.; ...

    2015-05-28

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

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

    PubMed

    Martín, Guido

    2003-03-01

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

  13. 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.

  14. Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

    NASA Astrophysics Data System (ADS)

    Li, Yan-Yan; Zhang, Xue-Ying; Ju, Yong-Qin; Ma, Fei; Zhang, Hong-Bin; Chen, Liang; Ge, Hong-Lin; Wan, Bo; Luo, Peng; Zhou, Bin; Zhang, Yan-Bin; Li, Jian-Yang; Xu, Jun-Kui; Wang, Song-Lin; Yang, Yong-Wei; Yang, Lei

    2015-04-01

    Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra. Supported by National Natural Science Foundation and Strategic Priority Research Program of the Chinese Academy of Sciences (11305229, 11105186, 91226107, 91026009, XDA03030300)

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

    SciTech Connect

    Blann, M.; Komoto, T.T.

    1988-01-01

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

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

    SciTech Connect

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

    1989-01-19

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

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

    SciTech Connect

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

    1998-04-01

    In many systems, it is imperative to have accurate knowledge of all significant sources of neutrons due to the decay of radionuclides. These sources can include neutrons resulting from the spontaneous fission of actinides, the interaction of actinide decay {alpha}-particles in ({alpha},n) reactions with low- or medium-Z nuclides, and/or delayed neutrons from the fission products of actinides. Numerous systems exist in which these neutron sources could be important. These include, but are not limited to, clean and spent nuclear fuel (UO{sub 2}, ThO{sub 2}, MOX, etc.), enrichment plant operations (UF{sub 6}, PuF{sub 4}, etc.), waste tank studies, waste products in borosilicate glass or glass-ceramic mixtures, and weapons-grade plutonium in storage containers. SOURCES-3A is a computer code that determines neutron production rates and spectra from ({alpha},n) reactions, spontaneous fission, and delayed neutron emission due to the decay of radionuclides in homogeneous media (i.e., a mixture of {alpha}-emitting source material and low-Z target material) and in interface problems (i.e., a slab of {alpha}-emitting source material in contact with a slab of low-Z target material). The code is also capable of calculating the neutron production rates due to ({alpha},n) reactions induced by a monoenergetic beam of {alpha}-particles incident on a slab of target material. Spontaneous fission spectra are calculated with evaluated half-life, spontaneous fission branching, and Watt spectrum parameters for 43 actinides. The ({alpha},n) spectra are calculated using an assumed isotropic angular distribution in the center-of-mass system with a library of 89 nuclide decay {alpha}-particle spectra, 24 sets of measured and/or evaluated ({alpha},n) cross sections and product nuclide level branching fractions, and functional {alpha}-particle stopping cross sections for Z < 106. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code outputs the magnitude

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

    SciTech Connect

    Lemley, E.C.; West, L.

    1996-12-31

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

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

    SciTech Connect

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

    1984-07-02

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Ebisuzaki, Toshikazu

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

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

    NASA Technical Reports Server (NTRS)

    Ebisuzaki, Toshikazu

    1987-01-01

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

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

    USGS Publications Warehouse

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

    1984-01-01

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

  5. Measurement of electron-positron spectrum in high-energy cosmic rays in the PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Karelin, A. V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Koldashov, S. V.; Koldobskiy, S. A.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A. A.; Mayorov, A. G.; Malakhov, V. V.; Marcelli, L.; Martucci, M.; Menn, W.; Merge, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Rossetto, L.; Simon, M.; Sparvoli, R.; Spillantini, P.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-08-01

    At present the existing data on the cosmic ray electron energy spectra in the high energy range are fragmented, and the situation is exacerbated by their small number. In the satellite PAMELA experiment measurements at high energies are carried out by the calorimeter. The experimental data accumulated for more than 8 years of measurements, with the information of the calorimeter, the neutron detector and the scintillation counters made it possible to obtain the total spectrum of high-energy electrons and positrons in energy range 0.3-3 TeV.

  6. Investigating in-field and out-of-field neutron contamination in high-energy medical linear accelerators based on the treatment factors of field size, depth, beam modifiers, and beam type.

    PubMed

    Biltekin, Fatih; Yeginer, Mete; Ozyigit, Gokhan

    2015-07-01

    We analysed the effects of field size, depth, beam modifier and beam type on the amount of in-field and out-of-field neutron contamination for medical linear accelerators (linacs). Measurements were carried out for three high-energy medical linacs of Elekta Synergy Platform, Varian Clinac DHX High Performance and Philips SL25 using bubble detectors. The photo-neutron measurements were taken in the first two linacs with 18 MV nominal energy, whereas the electro-neutrons were measured in the three linacs with 9 MeV, 10 MeV, 15 MeV and 18 MeV. The central neutron doses increased with larger field sizes as a dramatic drop off was observed in peripheral areas. Comparing with the jaws-shaped open-field of 10 × 10 cm, the motorised and physical wedges contributed to neutron contamination at central axis by 60% and 18%, respectively. The similar dose increment was observed in MLC-shaped fields. The contributions of MLCs were in the range of 55-59% and 19-22% in Elekta and Varian linacs comparing with 10 × 10 and 20 × 20 cm open fields shaped by the jaws, respectively. The neutron doses at shallow depths were found to be higher than the doses found at deeper regions. The electro-neutron dose at the 18 MeV energy was higher than the doses at the electron energies of 15 MeV and 9 MeV by a factor of 3 and 50, respectively. The photo- and electro-neutron dose should be taken into consideration in the radiation treatment with high photon and electron energies. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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

    PubMed

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

    2012-08-01

    The need of neutron capture cross section measurements for astrophysics motivates present work, where calculations to generate stellar neutron spectra at different temperatures are performed. The accelerator-based (7)Li(p,n)(7)Be reaction is used. Shaping the proton beam energy and the sample covering a specific solid angle, neutron activation for measuring stellar-averaged capture cross section can be done. High-quality Maxwell-Boltzmann neutron spectra are predicted. Assuming a general behavior of the neutron capture cross section a weighted fit of the spectrum to Maxwell-Boltzmann distributions is successfully introduced. Copyright © 2012 Elsevier Ltd. All rights reserved.

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

    PubMed Central

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

    1984-01-01

    Results have been obtained on the quasi-elastic spectra of neutrons scattered from pure water, a 20% agarose gel (hydration four grams H2O per gram of dry solid) and cysts of the brine shrimp Artemia for hydrations between 0.10 and 1.2 grams H2O per gram of dry solids. The spectra were interpreted using a two-component model that included contributions from the covalently bonded protons and the hydration water, and a mobile water fraction. The mobile fraction was described by a jump-diffusion correlation function for the translation motion and a simple diffusive orientational correlation function. The results for the line widths gamma (Q2) for pure water were in good agreement with previous measurements. The agarose results were consistent with NMR measurements that show a slightly reduced translational diffusion for the mobile water fraction. The Artemia results show that the translational diffusion coefficient of the mobile water fraction was greatly reduced from that of pure water. The line width was determined mainly by the rotational motion, which was also substantially reduced from the pure water value as determined from dielectric relaxation studies. The translational and rotational diffusion parameters were consistent with the NMR measurements of diffusion and relaxation. Values for the hydration fraction and the mean square thermal displacement [u2] as determined from the Q-dependence of the line areas were also obtained. PMID:6733243

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

    SciTech Connect

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

    2002-01-01

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

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

    SciTech Connect

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

    1999-09-01

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

  11. Streaming of 14-MeV neutrons through an iron duct: comparison of measured neutron and gamma-ray energy spectra with results calculated using the Monte Carlo code MCNP

    SciTech Connect

    Santoro, R.T.; Barnes, J.M.; Soran, P.D.; Alsmiller, R.G. Jr.

    1982-11-01

    Neutron and gamma-ray energy spectra resulting from the streaming of 14 MeV neutrons through a 0.30-m-diameter duct (length-to-diameter ratio = 2.83) have been calculated using the Monte Carlo code MCNP. The calculated spectra are compared with measured data and data calculated previously using a combination of discrete ordinates and Monte Carlo methods. Comparisons are made at twelve detector locations on and off the duct axis for neutrons with energies above 850 keV and for gamma rays with energies above 750 keV. The neutron spectra calculated using MCNP agree with the measured data within approx. 5 to approx. 50%, depending on detector location and neutron energy. Agreement with the measured gamma-ray spectra is also within approx. 5 to approx. 50%. The spectra obtained with MCNP are also in favorable agreement with the previously calculated data and were obtained with less calculational effort.

  12. High-Energy Anomaly in the Angle-Resolved Photoemission Spectra of Nd2-xCexCuO4: Evidence for a Matrix Element Effect

    NASA Astrophysics Data System (ADS)

    Rienks, E. D. L.; ńrrälä, M.; Lindroos, M.; Roth, F.; Tabis, W.; Yu, G.; Greven, M.; Fink, J.

    2014-09-01

    We use polarization-dependent angle-resolved photoemission spectroscopy (ARPES) to study the high-energy anomaly (HEA) in the dispersion of Nd2-xCexCuO4, x =0.123. We find that at particular photon energies the anomalous, waterfall-like dispersion gives way to a broad, continuous band. This suggests that the HEA is a matrix element effect: it arises due to a suppression of the intensity of the broadened quasiparticle band in a narrow momentum range. We confirm this interpretation experimentally, by showing that the HEA appears when the matrix element is suppressed deliberately by changing the light polarization. Calculations of the matrix element using atomic wave functions and simulation of the ARPES intensity with one-step model calculations provide further evidence for this scenario. The possibility to detect the full quasiparticle dispersion further allows us to extract the high-energy self-energy function near the center and at the edge of the Brillouin zone.

  13. Universal High Energy Anomaly in the Angle-Resolved Photoemission Spectra of High Temperature Superconductors: Possible Evidence of Spinon and Holon Branches

    NASA Astrophysics Data System (ADS)

    Graf, J.; Gweon, G.-H.; McElroy, K.; Zhou, S. Y.; Jozwiak, C.; Rotenberg, E.; Bill, A.; Sasagawa, T.; Eisaki, H.; Uchida, S.; Takagi, H.; Lee, D.-H.; Lanzara, A.

    2007-02-01

    A universal high energy anomaly in the single particle spectral function is reported in three different families of high temperature superconductors by using angle-resolved photoemission spectroscopy. As we follow the dispersing peak of the spectral function from the Fermi energy to the valence band complex, we find dispersion anomalies marked by two distinctive high energy scales, E1≈0.38eV and E2≈0.8eV. E1 marks the energy above which the dispersion splits into two branches. One is a continuation of the near parabolic dispersion, albeit with reduced spectral weight, and reaches the bottom of the band at the Γ point at ≈0.5eV. The other is given by a peak in the momentum space, nearly independent of energy between E1 and E2. Above E2, a bandlike dispersion reemerges. We conjecture that these two energies mark the disintegration of the low-energy quasiparticles into a spinon and holon branch in the high Tc cuprates.

  14. Using Gamma-Ray and Neutron Emission to Determine Solar Flare Accelerated Particle Spectra and Composition and the Conditions Within the Flare Magnetic Loop

    DTIC Science & Technology

    2007-01-01

    computer codes we have cal- culated the yields of deexcitation lines, escaping neutron spec- tra and the neutron capture line for monoenergetic ...USING GAMMA-RAYAND NEUTRON EMISSION TO DETERMINE SOLAR FLARE ACCELERATED PARTICLE SPECTRA AND COMPOSITION AND THE CONDITIONS WITHIN THE FLARE...California, San Diego, La Jolla, CA Received 2006 May 4; accepted 2006 August 23 ABSTRACT The measurable quantities associated with -ray and neutron

  15. ELECTROMAGNETIC EMISSION FROM LONG-LIVED BINARY NEUTRON STAR MERGER REMNANTS. II. LIGHT CURVES AND SPECTRA

    SciTech Connect

    Siegel, Daniel M.; Ciolfi, Riccardo E-mail: riccardo.ciolfi@unitn.it

    2016-03-01

    Recent observations indicate that in a large fraction of binary neutron star (BNS) mergers a long-lived neutron star (NS) may be formed rather than a black hole. Unambiguous electromagnetic (EM) signatures of such a scenario would strongly impact our knowledge on how short gamma-ray bursts (SGRBs) and their afterglow radiation are generated. Furthermore, such EM signals would have profound implications for multimessenger astronomy with joint EM and gravitational-wave (GW) observations of BNS mergers, which will soon become reality thanks to the ground-based advanced LIGO/Virgo GW detector network. Here we explore such EM signatures based on the model presented in a companion paper, which provides a self-consistent evolution of the post-merger system and its EM emission up to ∼10{sup 7} s. Light curves and spectra are computed for a wide range of post-merger physical properties. We present X-ray afterglow light curves corresponding to the “standard” and the “time-reversal” scenario for SGRBs (prompt emission associated with the merger or with the collapse of the long-lived NS). The light curve morphologies include single and two-plateau features with timescales and luminosities that are in good agreement with Swift observations. Furthermore, we compute the X-ray signal that should precede the SGRB in the time-reversal scenario, the detection of which would represent smoking-gun evidence for this scenario. Finally, we find a bright, highly isotropic EM transient peaking in the X-ray band at ∼10{sup 2}–10{sup 4} s after the BNS merger with luminosities of L{sub X} ∼ 10{sup 46}–10{sup 48} erg s{sup −1}. This signal represents a very promising EM counterpart to the GW emission from BNS mergers.

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

    NASA Astrophysics Data System (ADS)

    Siegel, Daniel M.; Ciolfi, Riccardo

    2016-03-01

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

  17. Signatures of asymmetry in neutron spectra and images predicted by three-dimensional radiation hydrodynamics simulations of indirect drive implosions

    NASA Astrophysics Data System (ADS)

    Chittenden, J. P.; Appelbe, B. D.; Manke, F.; McGlinchey, K.; Niasse, N. P. L.

    2016-05-01

    We present the results of 3D simulations of indirect drive inertial confinement fusion capsules driven by the "high-foot" radiation pulse on the National Ignition Facility. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium (DT) and deuterium-deuterium (DD) neutron spectra as well as primary and down scattered neutron images. Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutron spectra shift, width, and shape. Comparisons of primary and down scattered images highlight the lack of alignment between the neutron sources, scatter sites, and detector plane, which limits the ability to infer the ρr of the fuel from a down scattered ratio. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutron spectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.

  18. Signatures of asymmetry in neutron spectra and images predicted by three-dimensional radiation hydrodynamics simulations of indirect drive implosions

    SciTech Connect

    Chittenden, J. P. Appelbe, B. D.; Manke, F.; McGlinchey, K.; Niasse, N. P. L.

    2016-05-15

    We present the results of 3D simulations of indirect drive inertial confinement fusion capsules driven by the “high-foot” radiation pulse on the National Ignition Facility. The results are post-processed using a semi-deterministic ray tracing model to generate synthetic deuterium-tritium (DT) and deuterium-deuterium (DD) neutron spectra as well as primary and down scattered neutron images. Results with low-mode asymmetries are used to estimate the magnitude of anisotropy in the neutron spectra shift, width, and shape. Comparisons of primary and down scattered images highlight the lack of alignment between the neutron sources, scatter sites, and detector plane, which limits the ability to infer the ρr of the fuel from a down scattered ratio. Further calculations use high bandwidth multi-mode perturbations to induce multiple short scale length flows in the hotspot. The results indicate that the effect of fluid velocity is to produce a DT neutron spectrum with an apparently higher temperature than that inferred from the DD spectrum and which is also higher than the temperature implied by the DT to DD yield ratio.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-01-01

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

  1. Measurement and calculation of neutron leakage spectra from slab samples of beryllium, gallium and tungsten irradiated with 14.8 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Nie, Y. B.; Ruan, X. C.; Ren, J.; Zhang, S.; Han, R.; Bao, J.; Huang, H. X.; Ding, Y. Y.; Wu, H. C.; Liu, P.; Zhou, Z. Y.

    2017-09-01

    In order to make benchmark validation of the nuclear data for gallium (Ga), tungsten (W) and beryllium (Be) in existing modern evaluated nuclear data files, neutron leakage spectra in the range from 0.8 to 15 MeV from slab samples were measured by time-of-flight technique with a BC501 scintillation detector. The measurements were performed at China Institute of Atomic Energy (CIAE) using a D-T neutron source. The thicknesses of the slabs were 0.5 to 2.5 mean free path for 14.8 MeV neutrons, and the measured angles were chosen to be 60∘ and 120∘. The measured spectra were compared with those calculated by the continuous energy Monte-Carlo transport code MCNP, using the data from the CENDL-3.1, ENDF/B-VII.1 and JENDL-4.0 nuclear data files, the comparison between the experimental and calculated results show that: The results from all three libraries significantly underestimate the cross section in energy range of 10-13 MeV for Ga; For W, the calculated spectra using data from CENDL-3.1 and JENDL-4.0 libraries show larger discrepancies with the measured ones, especially around 8.5-13.5 MeV; and for Be, all the libraries led to underestimation below 3 MeV at 120∘.

  2. Measurement of the high energy component of the x-ray spectra in the VENUS electron cyclotron resonance ion source (abstract only)

    SciTech Connect

    Leitner, D.; Benitez, J. Y.; Lyneis, C. M.; Todd, D. S.; Ropponen, T.; Ropponen, J.; Koivisto, H.; Gammino, S.

    2008-02-15

    High performance electron cyclotron resonance (ECR) ion sources, such as VENUS (versatile ECR for nuclear science), produce large amounts of x rays. By studying their energy spectra, conclusions can be drawn about the electron heating process and the electron confinement. In addition, the bremsstrahlung from the plasma chamber is partly absorbed by the cold mass of the superconducting magnet adding an extra heat load to the cryostat. Germanium or NaI detectors are generally used for x-ray measurements. Due to the high x-ray flux from the source, the experimental setup to measure bremsstrahlung spectra from ECR ion sources is somewhat different than for the traditional nuclear physics measurements these detectors are generally used for. In particular, the collimation and background shielding can be problematic. In this paper we will discuss the experimental setup for such a measurement, the energy calibration and background reduction, the shielding of the detector, and collimation of the x-ray flux. We will present x-ray energy spectra and cryostat heating rates in dependence of various ion source parameters such as confinement fields, minimum B-field, rf power, and heating frequency.

  3. Study of optical model parameters for high energy neutron cross sections from 5 to 50 MeV in the mass-140 region

    SciTech Connect

    Phillips, T.W.; Camarda, H.S.; White, R.M.

    1980-05-08

    A study of the neutron optical potential on nuclei near mass-140 was begun to extend the energy range and improve the precision of previous neutron total cross section measurements. The extended energy range of this measurement reveals maxima and minima in the total cross section that are evidence of the nuclear Ramsauer effect. A 100-MeV linear accelerator is used to produce a continuum of neutron energies from a Ta-Be conversion target. A 250-meter flight path is used to measure neutron energies by the time-of-flight method. Transmission data for /sup 140/Ce and transmission ratios for /sup 142/Ce, /sup 141/Pr, and /sup 139/La relative to /sup 140/Ce were obtained. The /sup 140/Ce data have a precision of 1 to 3% and the ratios are obtained with a precision of about 0.3%. To analyze these total cross section data a computer code was developed to calculate the total elastic, reaction, and differential elastic scattering cross sections for a neutron interacting with a nucleus. The interaction is represented by a spherically symmetric complex potential that includes spin-orbit coupling. The parameters of this potential were adjusted to approximate the /sup 140/Ce total cross over the energy range from 2.5 to 60 MeV. The energy dependence of these parameters is described. 5 figures, 1 table.

  4. Impact of flows on ion temperatures inferred from neutron spectra in asymmetrically driven OMEGA DT implosions

    NASA Astrophysics Data System (ADS)

    Gatu Johnson, M.; Frenje, J. A.; Seguin, F. H.; Petrasso, R. D.; Aappelbe, B.; Chittenden, J.; Walsh, C.; Knauer, J. P.; Glebov, V. Yu.; Forrest, C.; Marshall, F.; Michel, T.; Stoeckl, C.; Sangster, T. C.; Zylstra, A.

    2016-10-01

    Ion temperatures (Tion) in Inertial Confinement Fusion (ICF) experiments have traditionally been inferred from the broadening of primary neutron spectra. Directional motion (flow) of the fuel at burn, expected to arise due to asymmetries imposed by engineering features (such as stalks, fill tubes, tents, or capsule imperfections) or drive non-uniformity, also impacts broadening and may lead to artificially inflated ``Tion'' values. Flow due to low-mode asymmetries is expected to give rise to line-of-sight variations in measured Tion, as observed in OMEGA cryogenic DT implosions but not in similar experiments at the NIF. In this presentation we report on an OMEGA experiment with intentionally asymmetric drive, designed to test the ability to accurately predict and measure line-of-sight differences in apparent Tion due to low-mode asymmetry-seeded flows. The results provide insight into the complexity of hot-spot dynamics, which is a problem that must be mastered to achieve ICF ignition. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  5. Two-Source Double-Slit Interference in Angle-Resolved High-Energy Above-Threshold Ionization Spectra of Diatoms

    SciTech Connect

    Okunishi, M.; Itaya, R.; Shimada, K.; Pruemper, G.; Ueda, K.; Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.; Becker, W.

    2009-07-24

    When an electron from a diatomic molecule undergoes tunneling-rescattering ionization, a novel form of destructive interference can be realized that involves all four geometric orbits that are available to the electron when it is freed, because both ionization and rescattering may take place at the same or at different centers. We find experimentally and confirm theoretically that in orientation-averaged angle-resolved high-order above-threshold ionization spectra the corresponding destructive interference is visible for O{sub 2} but not for N{sub 2}. This effect is different from the suppression of ionization that is well known to occur for O{sub 2}.

  6. Towards an optimum design of a P-MOS radiation detector for use in high-energy medical photon beams and neutron facilities: analysis of activation materials.

    PubMed

    Price, Robert A

    2005-01-01

    The behaviour of packaged and unpackaged ESAPMOS4 RadFET radiation detectors (NMRC Cork, Ireland) was investigated when used in the mixed photon and neutron environment of a medical linear accelerator operating above the nucleon separation energy and in a 14 MeV neutron field provided by a D-T generator. Within the uncertainty of the experimental set-up (4% at 95% confidence level) the unpackaged device was found to have essentially zero activation dose-burden whereas the packaged device exhibits a considerable degree of post irradiation absorbed dose due to deactivation radiation.

  7. Measurement of Feynman- spectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

    NASA Astrophysics Data System (ADS)

    Andreev, V.; Baghdasaryan, A.; Begzsuren, K.; Belousov, A.; Belov, P.; Boudry, V.; Brandt, G.; Brinkmann, M.; Brisson, V.; Britzger, D.; Buniatyan, A.; Bylinkin, A.; Bystritskaya, L.; Campbell, A. J.; Cantun Avila, K. B.; Ceccopieri, F.; Cerny, K.; Chekelian, V.; Contreras, J. G.; Dainton, J. B.; Daum, K.; Diaconu, C.; Dobre, M.; Dodonov, V.; Dossanov, A.; Eckerlin, G.; Egli, S.; Elsen, E.; Favart, L.; Fedotov, A.; Feltesse, J.; Ferencei, J.; Fleischer, M.; Fomenko, A.; Gabathuler, E.; Gayler, J.; Ghazaryan, S.; Glazov, A.; Goerlich, L.; Gogitidze, N.; Gouzevitch, M.; Grab, C.; Grebenyuk, A.; Greenshaw, T.; Grindhammer, G.; Haidt, D.; Henderson, R. C. W.; Herbst, M.; Hladkỳ, J.; Hoffmann, D.; Horisberger, R.; Hreus, T.; Huber, F.; Jacquet, M.; Janssen, X.; Jung, H.; Kapichine, M.; Kiesling, C.; Klein, M.; Kleinwort, C.; Kogler, R.; Kostka, P.; Kretzschmar, J.; Krüger, K.; Landon, M. P. J.; Lange, W.; Laycock, P.; Lebedev, A.; Levonian, S.; Lipka, K.; List, B.; List, J.; Lobodzinski, B.; Lytkin, L.; Malinovski, E.; Martyn, H.-U.; Maxfield, S. J.; Mehta, A.; Meyer, A. B.; Meyer, H.; Meyer, J.; Mikocki, S.; Morozov, A.; Müller, K.; Naumann, Th.; Newman, P. R.; Niebuhr, C.; Nowak, G.; Nowak, K.; Olsson, J. E.; Ozerov, D.; Pahl, P.; Pascaud, C.; Patel, G. D.; Perez, E.; Petrukhin, A.; Picuric, I.; Pirumov, H.; Pitzl, D.; Plačakytė, R.; Pokorny, B.; Polifka, R.; Povh, B.; Radescu, V.; Raicevic, N.; Ravdandorj, T.; Reimer, P.; Rizvi, E.; Robmann, P.; Roosen, R.; Rostovtsev, A.; Rotaru, M.; Rusakov, S.; Šálek, D.; Sankey, D. P. C.; Sauter, M.; Sauvan, E.; Schmitt, S.; Schoeffel, L.; Schöning, A.; Schultz-Coulon, H.-C.; Sefkow, F.; Shushkevich, S.; Soloviev, Y.; Sopicki, P.; South, D.; Spaskov, V.; Specka, A.; Steder, M.; Stella, B.; Straumann, U.; Sykora, T.; Thompson, P. D.; Traynor, D.; Truöl, P.; Tsakov, I.; Tseepeldorj, B.; Turnau, J.; Valkárová, A.; Vallée, C.; Van Mechelen, P.; Vazdik, Y.; Wegener, D.; Wünsch, E.; Žáček, J.; Zhang, Z.; Žlebčík, R.; Zohrabyan, H.; Zomer, F.

    2014-06-01

    Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic scattering at HERA are presented as a function of the Feynman variable and of the centre-of-mass energy of the virtual photon-proton system . The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of . The measurement is restricted to photons and neutrons in the pseudorapidity range and covers the range of negative four momentum transfer squared at the positron vertex GeV, of inelasticity and of GeV. To test the Feynman scaling hypothesis the dependence of the dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    SciTech Connect

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

    2015-10-15

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

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

    DOEpatents

    Distenfeld, Carl H.

    1978-01-01

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

  11. High energy reactor neutrinos

    NASA Astrophysics Data System (ADS)

    Raper, Neill

    We present the first measurement of a nonzero reactor neutrino flux with energies above 8 MeV. Measurements are taken with the Daya Bay Reactor Neutrino Experiments detectors, using the Guangdong Nuclear Power Station as a source. Disagreement between data and theory regarding rate and shape of reactor neutrino spectra have made the need for direct measurement clear. Data are especially useful at high energies, where far fewer isotopes contribute. Neutrino candidates are correlated to reactor power and reactor power is extrapolated to zero in order to separate neutrino events from background. We find evidence of reactor neutrinos up to ˜12.5 MeV at 1.92 sigma above 0 and include a survey of isotopes likely to be contributing neutrinos in this energy range.

  12. High-energy thermal synchrotron emission

    NASA Technical Reports Server (NTRS)

    Imamura, J. N.; Epstein, R. I.; Petrosian, V.

    1985-01-01

    It is shown how the thermal synchrotron emission spectrum is modified when the photon energy is greater than the mean energy of the radiating particles. The effect if applying this energy conservation constraint is to produce spectra which have less high-energy photon emission than had been previously estimated. The thermal synchrotron spectra provide satisfactory fits to recently observed very high energy gamma ray spectra of certain burst sources.

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

    PubMed

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

    2014-06-01

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

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

    SciTech Connect

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

    2014-06-15

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

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

    SciTech Connect

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

    1995-04-01

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

  16. Fast neutron yields and spectra from targets of varying atomic number bombarded with deuterons from 16 to 50 MeV.

    PubMed

    Meulders, J P; Leleux, P; Macq, P C; Pirart, C

    1975-03-01

    Neutron production from targets of Be, C, Mo, Cu, Ta and Au bombarded with deuterons of 16, 33 and 50 MeV has been studied at the isochronous cyclotron at Louvain-la-Neuve. Neutron spectra were measured by the time of flight method. The yields of neutrons and gamma rays were also measured, and the greatest ratio of neutrons to gamma rays in the forward direction was found to occur with 50 MeV deuterons on a Be target. The angular distribution of neutrons from Be was measured at 16, 33 and 50 MeV, and neutron spectra were measured as function of angle with 50 MeV deuterons on Be.

  17. 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 (Tion) and cold fuel areal density. We explain such novel methodologies used to determine neutron yield, apparent Tion and DSR.

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

    SciTech Connect

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

    2015-11-12

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

  19. Comparison of ({alpha},n) thick-target neutron yields and spectra from ORIGEN-S and SOURCES

    SciTech Connect

    Brown, T.H.; Wilson, W.B.; Perry, R.T.

    1998-12-31

    Both ORIGEN-S and SOURCES generate thick-target neutron yields and energy spectra from ({alpha}, n) reactions in homogeneous material containing alpha-emitting and ({alpha},n) target elements by simulating reaction physics, using alpha-emission energy spectra, elemental stopping cross sections, ({alpha}, n) target elements by simulating reaction physics, using alpha-emission energy spectra, elemental stopping cross sections, ({alpha}, n) cross sections for target nuclei, and branching fractions to product-nuclide energy levels. This methodology results in accurate yield and spectra. ORIGEN-S has two options for calculating yields and spectra. The UO{sub 2} option (default) estimates yields and spectra assuming the input alpha emitters to be infinitely dilute in UO{sub 2}. The borosilicate-glass option estimates yields from the total input material composition and generates spectra purportedly representative of spectra generated by {sup 238}Pu, {sup 241}Am, {sup 242}Cm, and {sup 244}Cm infinitely dilute in borosilicate glass, even if none of these four alpha emitters are present in the input material composition. Because yields from the borosilicate-glass option in ORIGEN-S are based on entire input material composition and are reasonably accurate, the same is often assumed to be true for spectra. The input/output functionality of the borosilicate-glass option, along with ambiguity in ORIGEN-S documentation, gives the incorrect impression that spectra representative of input compositions are generated. This impression is reinforced by wide usage of the SCALE code system and its ORIGEN-S module and their sponsorship by the US Nuclear Regulatory Commission.

  20. Multipolarity analysis for {sup 14}C high-energy resonance populated by ({sup 18}O,{sup 16}O) two-neutron transfer reaction

    SciTech Connect

    Carbone, D. Cavallaro, M.; Bondì, M.; Agodi, C.; Cunsolo, A.; Cappuzzello, F.; Azaiez, F.; Franchoo, S.; Khan, E.; Bonaccorso, A.; Fortunato, L.; Foti, A.; Linares, R.; Lubian, J.; Scarpaci, J. A.; Vitturi, A.

    2015-10-15

    The {sup 12}C({sup 18}O,{sup 16}O){sup 14}C reaction at 84 MeV incident energy has been explored up to high excitation energy of the residual nucleus thanks to the use of the MAGNEX spectrometer to detect the ejectiles. In the region above the two-neutron separation energy, a resonance has been observed at 16.9 MeV. A multipolarity analysis of the cross section angular distribution indicates an L = 0 character for such a transition.

  1. (n,xn) cross section measurements for Y-89 foils used as detectors for high energy neutron measurements in the deeply subcritical assembly "QUINTA"

    NASA Astrophysics Data System (ADS)

    Bielewicz, Marcin; Kilim, Stanisław; Strugalska-Gola, Elżbieta; Szuta, Marcin; Wojciechowski, Andrzej; Tyutyunnikov, Sergey; Prokofiev, Alexander; Passoth, Elke

    2017-09-01

    Study of the deep subcritical systems (QUINTA) using relativistic beams is performed within the project "Energy and Transmutation of Radioactive Wastes" (E&T - RAW). The experiment assembly was irradiated by deuteron/proton beam (Dubna NUCLOTRON). We calculated the neutron energy spectrum inside the whole assembly by using threshold energy (n,xn) reactions in yttrium (Y-89) foils. There are almost no experimental cross section data for those reactions. New Y-89(n,xn) cross section measurements were carried out at The Svedberg laboratory (TSL) in Uppsala, Sweden in 2015. In this paper we present preliminary results of those experiments.

  2. Inelastic Neutron Scattering Studies of High-Energy Spin Excitations in Superconducting BaFe1.9Ni0.1As2

    NASA Astrophysics Data System (ADS)

    Liu, Mengshu; Abernathy, Douglas; Zhao, Jun; Wang, Meng; Zhang, Chenglin; Wang, Miaoyin; Dai, Pengcheng

    2010-03-01

    Understanding how the spin fluctuations evolve with doping in iron pnictide superconductors is important because spin fluctuations may mediate electron pairing for superconductivity in these materials. Upon doping, the spin fluctuation persists long after the long-range antiferromagnetism is destroyed. More importantly, spin excitations are coupled to superconductivity in the appearance of a neutron magnetic resonance and a superconductivity-induced spin gap. However, all current neutron scattering results in iron based superconductors are confined to low energy excitations except for the ``11'' FeTe1-xSex system, which shows incommensurate excitations that are not found in other iron pnictide systems. Therefore, how the spin waves in parent compounds of the ``122'' (AFe2As2, A = Ca, Sr, Ba) system will evolve when the system becomes an optimal superconductor is still an open question. We use time-of-flight spectroscopy to determine S (Q,φ) at energy regions not accessed before. We compare spin fluctuations of iron arsenide superconductors with those of high-Tc copper oxides and discuss their role in the superconductivity of these materials.

  3. High-Energy Astrophysics: An Overview

    NASA Technical Reports Server (NTRS)

    Fishman, Gerald J.

    2007-01-01

    High-energy astrophysics is the study of objects and phenomena in space with energy densities much greater than that found in normal stars and galaxies. These include black holes, neutron stars, cosmic rays, hypernovae and gamma-ray bursts. A history and an overview of high-energy astrophysics will be presented, including a description of the objects that are observed. Observing techniques, space-borne missions in high-energy astrophysics and some recent discoveries will also be described. Several entirely new types of astronomy are being employed in high-energy astrophysics. These will be briefly described, along with some NASA missions currently under development.

  4. Nuclear level densities in 47V, 48V, 49V, 53Mn, and 54Mn from neutron evaporation spectra

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    SciTech Connect

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

    2015-11-14

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

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1990-12-01

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

  9. Proliferative characteristics of intestinal stem cells. Response and protection to high-energy or fission spectrum neutrons or photons. Technical report, 1 December 1983-1 December 1985

    SciTech Connect

    Hanson, W.R.

    1986-04-30

    Cytosine Arabinoside (Ara/C) is an S-phase cytoxic agent. Since nearly half the proliferating cells in the murine crypt are in the S phase, Ara/c treatment, the clonogenic cells (the cells responsible for tissue regeneration) in the crypt are considerably less sensitive to photon radiation than colonogenic cells of control animals. Evidence suggests that the reason for this radioprotection by a toxic agent is the Ara/c-induced alteration in the cell age distribution of the clonogenic cells. Normally, the clonogenic cells are in a G/sub 1/ or G/sub 0/ stage of the cell cycle and are unaffected directly by Ara/c; however, following Ara/c treatment of an animal, the clonogenic cells enter the cell cycle. By 12 hours, the clonogenic cells proceed in a partially synchronized fashion to a mid toi late S phase of the cell cycle where they are less sensitive. WR-2721 appears to protect cells from radiation throughout the cell cycle and most likely acts through a mechanism different from Ara/c. Results of this contrast showed that the combination of Ara/c and WR-2721 protected the gut from photon injury to a greater extent than each agent alone. The protection from Fermilab neutrons by the combination was slightly better than each agent and there was no additional protection of Ara/c combined with WR-2721 for injury by JANUS fission spectrum neutrons. These treatments did not alter the animal response at doses in the bone marrow lethal range.

  10. Neutron spectra measurement and calculations using data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 in iron benchmark assemblies

    NASA Astrophysics Data System (ADS)

    Jansky, Bohumil; Rejchrt, Jiri; Novak, Evzen; Losa, Evzen; Blokhin, Anatoly I.; Mitenkova, Elena

    2017-09-01

    The leakage neutron spectra measurements have been done on benchmark spherical assemblies - iron spheres with diameter of 20, 30, 50 and 100 cm. The Cf-252 neutron source was placed into the centre of iron sphere. The proton recoil method was used for neutron spectra measurement using spherical hydrogen proportional counters with diameter of 4 cm and with pressure of 400 and 1000 kPa. The neutron energy range of spectrometer is from 0.1 to 1.3 MeV. This energy interval represents about 85 % of all leakage neutrons from Fe sphere of diameter 50 cm and about of 74% for Fe sphere of diameter 100 cm. The adequate MCNP neutron spectra calculations based on data libraries CIELO, JEFF-3.2 and ENDF/B-VII.1 were done. Two calculations were done with CIELO library. The first one used data for all Fe-isotopes from CIELO and the second one (CIELO-56) used only Fe-56 data from CIELO and data for other Fe isotopes were from ENDF/B-VII.1. The energy structure used for calculations and measurements was 40 gpd (groups per decade) and 200 gpd. Structure 200 gpd represents lethargy step about of 1%. This relatively fine energy structure enables to analyze the Fe resonance neutron energy structure. The evaluated cross section data of Fe were validated on comparisons between the calculated and experimental spectra.

  11. Energy and Angular Spectra of Albedo Protons and Neutrons Emitted from Hydrated Layers of Lunar Regolith

    NASA Astrophysics Data System (ADS)

    Townsend, L. W.; Zaman, F.; Schwadron, N. A.; Wilson, J. K.; Spence, H. E.; Case, A. W.; Kasper, J. C.; Mazur, J. E.; Looper, M. D.

    2016-11-01

    Energy and angular yields of albedo protons and neutrons emitted from the lunar surface as a function of hydration layer thickness in the lunar regolith using the MCNP computer code developed at Los Alamos National Laboratory are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  13. The equilibrium and preequilibrium neutron-emission spectra of some structural fusion materials for (n, xn) reactions up to 16 MeV energy

    SciTech Connect

    Kaplan, A.; Tel, E.; Aydin, A.

    2009-06-15

    In this study, neutron-emission spectra produced by (n, xn) reactions for some structural fusion materials as {sup 27}Al, {sup 51}V, {sup 52}Cr, {sup 55}Mn, and {sup 56}Fe have been investigated by a neutron beam up to 16 MeV. Multiple preequilibrium mean-free-path constant from internal transition and the preequilibrium and equilibrium level-density parameters have been investigated for some (n, xn) neutron-emission spectra calculated in this study. Preequilibrium neutron-emission spectra were calculated by using new-evaluated hybrid model and geometry-dependent hybrid model, full-exciton model, and cascade-exciton model. The reaction equilibrium component was calculated by Weisskopf-Ewing model. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

  14. Structure of fragment energy spectra in spontaneous fission of sup 242 Cm and fast-neutron fission of sup 242 m Am

    SciTech Connect

    Fomushkin, E.F.; Vinogradov, Y.I.; Gavrilov, V.V.; Novoselov, G.F.; Shvetsov, A.M.

    1989-05-01

    A technique for measurement of the energy spectra of fission fragments is discussed. The fine structure found in the spectra of fragments from spontaneous fission of {sup 242}Cm and fast-neutron fission of {sup 242{ital m}}Am is analyzed. The quantitative parameters of the structure and their analogy with the characteristics of cold fission are discussed.

  15. Ultraviolet spectra of HZ Herculis/Hercules X-1 from HST: Hot gas during total eclipse of the neutron star

    NASA Technical Reports Server (NTRS)

    Anderson, Scott F.; Wachter, Stefanie; Margon, Bruce; Downes, Ronald A.; Blair, William P.; Halpern, Jules P.

    1994-01-01

    The Faint Object Spectrograph (FOS) aboard Hubble Space Telescope (HST) has been used in the UV to observe the prototypical X-ray pulsar Her X-1 and its companion HZ Her. Optical spectra were also obtained contemporaneously at the Kitt Peak National Observatory (KPNO) 2.1 m. The FOS spectra encompass the 1150-3300 A range near binary orbital phases 0.5 (X-ray maximum) and at 0.0 (mid-X-ray eclipse). The maximum light spectra show strong, narrow C III, N V, O V, Si IV + O IV), N IV), C IV, He II, and N IV emission lines, extending previous IUE results; the O III lambda 3133 Bowen resonance line is also prominent, confirming that the Bowen mechanism is the source of the strong lambda lambda 4640, 4650 emission complex, also seen at maximum light. Most remarkable, however, are the minimum light spectra, where the object is too faint for reasonable observations from IUE. Despite the total eclipse of the X-ray-emitting neutron star, our spectra show strong emission at N V lambda 1240, S IV + O IV) whose emission dominates the UV light at phase 0.0 might be associated with the 'accretion disk corona,' it is more likely the source is somewhat less hot (but extended) gas above and around the disk, or perhaps circumstellar material such as a stellar wind.

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

    SciTech Connect

    Murphy, T. J.

    2014-07-15

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

  17. Experimental analysis of neutron and background gamma-ray energy spectra of 80-400 MeV 7Li(p,n) reactions under the quasi-monoenergetic neutron field at RCNP, Osaka University

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yosuke; Sato, Tatsuhiko; Satoh, Daiki; Hagiwara, Masayuki; Yashima, Hiroshi; Masuda, Akihiko; Matsumoto, Tetsuro; Iwase, Hiroshi; Shima, Tatsushi; Nakamura, Takashi

    2017-09-01

    To develop the 100-400 MeV quasi-monoenergetic neutron field, we measured neutron and unexpected gamma-ray energy spectra of the 7Li(p,n) reaction with 80-389 MeV protons in the 100-m time-of-flight (TOF) tunnel at the Research Center for Nuclear Physics (RCNP) cyclotron facility. Neutron energy spectra with energies above 3 MeV were measured by the TOF method, which had been reported in our previous papers, and photon energy spectra with energies above 0.1 MeV were measured by the automatic unfolding function of the radiation dose monitor DARWIN. For neutron spectra, the contribution of peak intensity to the total intensity integrated with energies above 3 MeV varied between 0.38 and 0.48 in the proton energy range of 80-389 MeV. For gamma-ray spectra, highenergetic gamma-rays at around 70 MeV originated from the decay of π0 were observed with proton energies higher than 200 MeV. For the 246-MeV proton incident reaction, the contribution of gamma-ray dose to neutron dose is negligible because the ratio of gamma-ray dose to neutron dose is 0.014.

  18. Extraterrestrial high energy neutrino fluxes

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.

    1979-01-01

    Using the most recent cosmic ray spectra up to 2x10 to the 20th power eV, production spectra of high energy neutrinos from cosmic ray interactions with interstellar gas and extragalactic interactions of ultrahigh energy cosmic rays with 3K universal background photons are presented and discussed. Estimates of the fluxes from cosmic diffuse sources and the nearby quasar 3C273 are made using the generic relationship between secondary neutrinos and gammas and using recent gamma ray satellite data. These gamma ray data provide important upper limits on cosmological neutrinos. Quantitative estimates of the observability of high energy neutrinos from the inner galaxy and 3C273 above atmospheric background for a DUMAND type detector are discussed in the context of the Weinberg-Salam model with sq sin theta omega = 0.2 and including the atmospheric background from the decay of charmed mesons. Constraints on cosmological high energy neutrino production models are also discussed. It appears that important high energy neutrino astronomy may be possible with DUMAND, but very long observing times are required.

  19. 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.

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

    PubMed

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

    2014-10-01

    High-resolution neutron energy spectra, covering the entire energy range of interest, for two standard radionuclide neutron sources ((241)Am-B and (241)Am-F) have been derived from Bonner sphere measurements by using high-resolution a priori data in the unfolding process. In each case, two a priori spectra were used, one from a two-stage calculation and also one from a combination of the calculated spectrum with a high-resolution measured spectrum. The unfolded spectra are compared with those published elsewhere and show significant differences from the ISO- and IAEA-recommended spectra for (241)Am-B and (241)Am-F, respectively. Values for the fluence-average energy and fluence-to-dose-equivalent conversion coefficients are presented for the new spectra, and the implications of the new spectra for the emission rates of the sources when measured by the manganese bath technique are also determined. © Crown copyright 2013.

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

    SciTech Connect

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Lei, Yajuan; Zhang, Haotong; zhang, Yanxia

    2015-08-01

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

  3. ORIGEN-S (. cap alpha. ,n) neutron source spectra in borosilicate glass containing HLW (high-level waste)

    SciTech Connect

    Hermann, O.W.; Parks, C.V.; Ludwig, S.B.

    1987-01-01

    There is growing interest in the methodology and computational software for evaluating the (..cap alpha..,n) source spectra produced in mixtures of high-level waste (HLW) and borosilicate glass. The need for this development has been seen in previous work involving the analysis of HLW in borosilicate glass. Descriptions and applications of the ORIGEN-S method of computing neutron source spectra by both (..cap alpha..,n) reactions and spontaneous fission of UO/sub 2/ spent fuel have been reported previously. This summary presents a significant expansion of the ORIGEN-S (..cap alpha..,n) model to include ..cap alpha..-interactions with the light elements of borosilicate glass.

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

    PubMed

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

    2014-05-02

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  7. High Energy Astronomy Observatory (HEAO)

    NASA Technical Reports Server (NTRS)

    1972-01-01

    This is an artist's concept describing the High Energy Astronomy Observatory (HEAO). The HEAO project involved the launching of three unmarned scientific observatories into low Earth orbit between 1977 and 1979 to study some of the most intriguing mysteries of the universe; pulsars, black holes, neutron stars, and super nova. This concept was painted by Jack Hood of the Marshall Space Flight Center (MSFC). Hardware support for the imaging instruments was provided by American Science and Engineering. The HEAO spacecraft were built by TRW, Inc. under project management of the MSFC.

  8. Neutron Spectra, Fluence and Dose Rates from Bare and Moderated Cf-252 Sources

    SciTech Connect

    Radev, Radoslav P.

    2016-04-01

    A new, stronger 252Cf source (serial number SR-CF-3050-OR) was obtained from Oak Ridge National Laboratory (ORNL) in 2014 to supplement the existing 252Cf sources which had significantly decayed. A new instrument positioning track system was designed and installed by Hopewell Designs, Inc. in 2011. The neutron field from the new, stronger 252Cf source in the modified calibration environment needed to be characterized as well as the modified neutron fields produced by the new source and seven different neutron moderators. Comprehensive information about our 252Cf source, its origin, production, and isotopic content and decay characteristics needed to be compiled as well. This technical report is intended to address these issues.

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

    SciTech Connect

    Reedy, Robert; Frankle, S. C.

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  11. DOSE AND GAMMA-RAY SPECTRA FROM NEUTRON-INDUCED RADIOACTIVITY IN MEDICAL LINEAR ACCELERATORS FOLLOWING HIGH-ENERGY TOTAL BODY IRRADIATION.

    PubMed

    Keehan, S; Taylor, M L; Smith, R L; Dunn, L; Kron, T; Franich, R D

    2016-12-01

    Production of radioisotopes in medical linear accelerators (linacs) is of concern when the beam energy exceeds the threshold for the photonuclear interaction. Staff and patients may receive a radiation dose as a result of the induced radioactivity in the linac. Gamma-ray spectroscopy was used to identify the isotopes produced following the delivery of 18 MV photon beams from a Varian 21EX and an Elekta Synergy. The prominent radioisotopes produced include (187)W, (63)Zn, (56)Mn, (24)Na and (28)Al in both linac models. The dose rate was measured at the beam exit window (12.6 µSv in the first 10 min) following 18 MV total body irradiation (TBI) beams. For a throughput of 24 TBI patients per year, staff members are estimated to receive an annual dose of up to 750 μSv at the patient location. This can be further reduced to 65 μSv by closing the jaws before re-entering the treatment bunker. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

    SciTech Connect

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

    1980-05-01

    Measurements were performed using a 35 MeV deuteron beam from the isochronous cyclotron at the University of California at Davis. Data were obtained using the time-of-flight technique with an NE213 liquid scintillator. One set of measurements was used to observe the neutron spectrum from approx. 1 MeV to approx. 50 MeV, the maximum kinematically allowed energy. Observation angles were from 0/sup 0/ to 150/sup 0/ with emphasis on forward angles. Spectral data below approx. 1.5 MeV had poor accuracy. It was felt that a significant fraction of the neutron yield might lie at still lower energies, therefore a second set of measurements was performed to investigate the spectra to as low an energy as possible. Additional measurements were performed with a target enriched in the isotope /sup 6/Li replacing the natural lithium target used in previous measurements. The main advantage of a /sup 6/Li target is that the maximum kinematically allowed neutron energy is only about 38 MeV, hence reducing shielding requirements. The experiments, preliminary results, and future needs will be described.

  13. Accuracy of Mass and Radius Determination for Neutron Stars in X-ray Bursters from Simulated LOFT Spectra

    NASA Astrophysics Data System (ADS)

    Majczyna, A.; Madej, J.; Różańska, A.; Należyty, M.

    2017-06-01

    We present a simulation of an X-ray spectrum of a hot neutron star, as would be seen by the LAD detector on board of LOFT satellite. We also compute a grid of theoretical spectra corresponding to a range of effective temperatures Teff and surface gravities log g with values corresponding to compact stars in Type I X-ray bursters. A neutron star with the mass M=1.64 M⊙ and the radius R=11.95 km (which yields the surface gravity log g=14.30 [cgs] and the surface redshift z=0.30) is used in simulation. Accuracy of mass and radius determination by fitting theoretical spectra to the observed one is found to be M=1.64+0.16-0.02 M⊙ and R=11.95+1.57-0.40 km (2σ). The confidence contours for these two variables are narrow but elongated, and therefore the resulting constraints on the EOS cannot be strong. Note, that in this paper we aim to discuss error contours of NS mass and radius, whereas discussion of EOS is beyond the scope of this work.

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

    SciTech Connect

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

    2015-05-28

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

  15. SONTRAC: A solar neutron track chamber detector

    NASA Technical Reports Server (NTRS)

    Frye, G. M., Jr.; Jenkins, T. L.; Owens, A.

    1985-01-01

    The recent detection on the solar maximum mission (SMM) satellite of high energy neutrons emitted during large solar flares has provided renewed incentive to design a neutron detector which has the sensitivity, energy resolution, and time resolution to measure the neutron time and energy spectra with sufficient precision to improve our understanding of the basic flare processes. Over the past two decades a variety of neutron detectors has been flown to measure the atmospheric neutron intensity above 10 MeV and to search for solar neutrons. The SONTRAC (Solar Neutron Track Chamber) detector, a new type of neutron detector which utilizes n-p scattering and has a sensitivity 1-3 orders of magnitude greater than previous instruments in the 20-200 MeV range is described. The energy resolution is 1% for neutron kinetic energy, T sub n 50 MeV. When used with a coded aperture mask at 50 m (as would be possible on the space station) an angular resolution of approx. 4 arc sec could be achieved, thereby locating the sites of high energy nuclear interactions with an angular precision comparable to the existing x-ray experiments on SMM. The scintillation chamber is investigated as a track chamber for high energy physics, either by using arrays of scintillating optical fibers or by optical imaging of particle trajectories in a block of scintillator.

  16. Material Classification by Analysis of Prompt Photon Spectra Induced by 14-Mev Neutrons

    NASA Astrophysics Data System (ADS)

    Barzilov, Alexander; Novikov, Ivan

    Neutron based technologies are widely used in the field of bulk material analysis. These methods employ characteristic prompt gamma rays induced by a neutron probe for classification of the interrogated object using the elemental parameters extracted from the spectral data. Automatic data analysis and material classification algorithms are required for applications where access to nuclear spectroscopy expertise is limited and/or the autonomous robotic operation is necessary. Data obtained with neutron based systems differ from elemental composition evaluations based on chemical formulae due to statistical nature of nuclear reactions, presence of shielding and cladding, and other environmental conditions. Experimental data that are produced by the spectral decomposition can be expressed graphically as sets of overlapping classes in a multidimensional space of measured elemental intensities. To discriminate between classes of various materials, decision-tree and pattern recognition algorithms were studied. Results of application of these methods to data sets obtained for a pulsed 14-MeV neutron generator based active interrogation system are discussed.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  18. Neutron dose in and out of 18MV photon fields.

    PubMed

    Ezzati, A O; Studenski, M T

    2017-04-01

    In radiation therapy, neutron contamination is an undesirable side effect of using high energy photons to treat patients. Neutron contamination requires adjustments to the shielding requirements of the linear accelerator vault and contributes to the risk of secondary malignancies in patients by delivering dose outside of the primary treatment field. Using MCNPX, an established Monte Carlo code, manufacturer blueprints, and the most up to date ICRP neutron dose conversion factors, the neutron spectra, neutron/photon dose ratio, and the neutron capture gamma ray dose were calculated at different depths and off axis distances in a tissue equivalent phantom. Results demonstrated that the neutron spectra and dose are dependent on field size, depth in the phantom, and off-axis distance. Simulations showed that because of the low neutron absorption cross section of the linear accelerator head materials, the contribution to overall patient dose from neutrons can be up to 1000 times the photon dose out of the treatment field and is also dependent on field size and depth. Beyond 45cm off-axis, the dependence of the neutron dose on field size is minimal. Neutron capture gamma ray dose is also field size dependent and is at a maximum at a depth of about 7cm. It is important to remember that when treating with high energy photons, the dose from contamination neutrons must be considered as it is much greater than the photon dose.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  20. High-energy magnetic excitations in overdoped La2-xSrxCuO4 studied by neutron and resonant inelastic X-ray scattering

    SciTech Connect

    Wakimoto, S.; Ishii, K.; Kimura, H.; Fujita, M.; Dellea, G.; Kummer, K.; Braicovich, L.; Ghiringhelli, G.; Debeer-Schmitt, Lisa M.; Granroth, Garrett E.

    2015-05-21

    We have performed neutron inelastic scattering and resonant inelastic x-ray scattering (RIXS) at the Cu-L3 edge to study high-energy magnetic excitations at energy transfers of more than 100 meV for overdoped La2₋xSrxCuO4 with x=0.25 (Tc=15 K) and x=0.30 (nonsuperconducting) using identical single-crystal samples for the two techniques. From constant-energy slices of neutron-scattering cross sections, we have identified magnetic excitations up to ~250 meV for x=0.25. Although the width in the momentum direction is large, the peak positions along the (π,π) direction agree with the dispersion relation of the spin wave in the nondoped La2CuO4 (LCO), which is consistent with the previous RIXS results of cuprate superconductors. Using RIXS at the Cu-L3 edge, we have measured the dispersion relations of the so-called paramagnon mode along both (π,π) and (π,0) directions. Although in both directions the neutron and RIXS data connect with each other and the paramagnon along (π,0) agrees well with the LCO spin-wave dispersion, the paramagnon in the (π,π) direction probed by RIXS appears to be less dispersive and the excitation energy is lower than the spin wave of LCO near (π/2,π/2). Thus, our results indicate consistency between neutron inelastic scattering and RIXS, and elucidate the entire magnetic excitation in the (π,π) direction by the complementary use of two probes. The polarization dependence of the RIXS profiles indicates that appreciable charge excitations exist in the same energy range of magnetic excitations, reflecting the itinerant character of the overdoped sample. Lastly, we find a possible anisotropy in the charge excitation intensity might explain the apparent differences in the paramagnon dispersion in the (π,π) direction as detected by the x-ray scattering.

  1. Determination of neutron spectra within the energy of 1 keV to 1 MeV by means of reactor dosimetry

    SciTech Connect

    Sergeyeva, Victoria; Destouches, Christophe; Lyoussi, Abdallah; Thiollay, Nicolas; Vigneau, Olivier; Korschinek, Gunther; Carcreff, Hubert

    2015-07-01

    The standard procedure for neutron reactor dosimetry is based on neutron irradiation of a target and its post-irradiation analysis by Gamma and/or X-ray spectrometry. Nowadays, the neutron spectra can be easily characterized for thermal and fast energies (respectively 0.025 eV and >1 MeV). In this work we propose a new target and an innovating post-irradiation technique of analysis in order to detect the neutron spectra within the energy of 1 keV to 1 MeV. This article will present the calculations performed for the selection of a suitable nuclear reaction and isotope, the results predicted by simulations, the irradiation campaign that is proposed and the post-irradiation technique of analysis. (authors)

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  4. UV Spectra of HZ Her/Her X-1 from HST: Hot Gas During Total Eclipse of the Neutron Star

    NASA Astrophysics Data System (ADS)

    Anderson, S. F.; Wachter, S.; Margon, B.; Downes, R. A.

    1993-05-01

    The Faint Object Spectrograph aboard Hubble Space Telescope has observed HZ Her, the companion of the prototypical binary X-ray pulsar Her X-1, in its high spectral resolution mode (lambda /Delta lambda ~ 1200). The spectra encompass the 1150--3300 Angstroms range at binary orbital phases 0.5 and 0.0, corresponding to X-ray maximum and mid-X-ray eclipse, respectively. The maximum light spectra are dominated by strong, narrow NV, CIV, and HeII emission, confirming and extending previous IUE results. The OIII Bowen resonance fluorescence line at lambda3133 is particularly prominent, confirming that the Bowen mechanism is most certainly the source of the strong lambda lambda4640 , 4650 emission complex. Most remarkable, however, are the minimum light spectra, where the object is too faint for reasonable observations from IUE. Despite the total eclipse of the X-ray-emitting neutron star, our spectra show strong emission at NV lambda 1240, SiIV lambda 1400, NIV] lambda1488 , and CIV lambda1549 . (The situation at Lalpha is ambiguous due to geocoronal contamination). In a little-cited observation almost two decades ago, Koo & Kron (PASP, 89, 285) reported an incident of HeII lambda4686 in emission on a glass plate obtained in 1973 at mid-eclipse in a heroic 6 hr exposure by R. Kraft. However, very few ground-based spectra of HZ Her have been published in the last decade, and it does not seem commonly appreciated that strong, high excitation emission is indeed present, probably routinely, when the neutron star is occulted. Although the hot gas might be associated with the ``accretion disk corona" (inferred to be present through very weak X-ray emission during eclipse), more likely the source is somewhat cooler blobs above and around the disk, also thought to be responsible for the occasional odd ``X-ray dips," as well as features in the optical light curve. This work has been supported by NASA Grant NAG5-1630.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  6. High Energy Missile Project

    DTIC Science & Technology

    2004-12-01

    hypervelocity missile concept has been investigated. This research and development project called High Energy Missile (HEMi) technology...currently valid OMB control number. 1. REPORT DATE 00 DEC 2004 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE High Energy

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

    SciTech Connect

    Meadows, J.W.

    1991-11-01

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

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

    SciTech Connect

    Meadows, J.W.

    1991-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  10. What High Energy Emissions Reveal about Solar Flares

    NASA Astrophysics Data System (ADS)

    Murphy, R. J.; Share, G. H.

    Interactions of accelerated ions in solar flares produce gamma-ray lines and continuum and neutrons. These emissions contain a rich set of observable quantities such as line intensities, shapes, shifts and time histories and escaping neutron spectra and time histories. An extensive database of high-energy flare observations spanning almost 25 years exists from various missions such as SMM/GRS, Yohkoh, all four CGRO instruments, GAMMA-1, and GRANAT/Phebus. RHESSI, launched in 2002, observed the 2002 July 23 solar flare and provided the first comprehensive high-spectral resolution measurements and gamma-ray imaging of a flare and has since observed gamma-ray lines from the 2003 October 28 and November 2 flares. These high-energy measurements provide information not only about the accelerated particles but also about the physical conditions at the flare site. We will discuss how this information is extracted from the measurements and review what has been learned about the acceleration process, the relationship of flare particles with particles observed in space, and the flare environment.

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

    SciTech Connect

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

    1995-06-01

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

  12. Gaps in nuclear spectra as traces of seniority changes in systems of both neutrons and protons

    NASA Astrophysics Data System (ADS)

    Zamick, Larry

    2016-03-01

    There has been a great deal of attention given to the low-lying energy spectrum in a nucleus because of the abundance of experimental data. Likewise, perhaps to a lesser extent but still significant, the high end for a given configuration has been examined. Here, using single j shell calculations as a guide, we examine the middle part of the spectrum resulting from single j shell calculations. Seniority arguments are used to partially explain the midshell behaviors even though in general seniority is not a good quantum number for mixed systems of neutrons and protons.

  13. A cross-validation procedure for stopping the EM algorithm and deconvolution of neutron depth profiling spectra

    SciTech Connect

    Coakley, K.J. )

    1991-02-01

    The iterative EM algorithm is used to deconvolve neutron depth profiling spectra. Because of statistical noise in the data, artifacts in the estimated particle emission rate profile appear after too many iterations of the EM algorithm. To avoid artifacts, the EM algorithm is stopped using a cross-validation procedure. The data are split into two independent halves. The EM algorithm is applied to one half of the data to get an estimate of the emission rates. The algorithm is stopped when the conditional likelihood of the other half of the data passes through its maximum. The roles of the two halves of the data are then switched to get a second estimate of the emission rates. The two estimates are then averaged.

  14. Analysis of neutron diffraction spectra acquired [ital in situ] during stress-induced transformations in superelastic NiTi

    SciTech Connect

    Vaidyanathan, R. ); Bourke, M.A. ); Dunand, D.C. )

    1999-09-01

    Neutron diffraction spectra were obtained during various stages of a reversible stress-induced austenite to martensite phase transformation in superelastic NiTi. This was accomplished by neutron diffraction measurements on bulk polycrystalline NiTi samples simultaneously subjected to mechanical loading. Analysis of the data was carried out using individual lattice plane ([ital hkl]) reflections as well as by Rietveld refinement. In the Rietveld procedure, strains in austenite were described in terms of an isotropic ([ital hkl] independent) and an anisotropic ([ital hkl] dependent) component. At higher stresses, austenite lattice plane reflections exhibited nonlinear and dissimilar elastic responses which may be attributed to the transformation. The texture evolution is significant in both austenite and martensite phases during the transformation and two approaches were used to describe this evolving texture, i.e., an ellipsoidal model due to March[endash]Dollase and a generalized spherical-harmonic approach. The respective predictions of the phase fraction evolution as a function of applied stress were compared. A methodology is thus established to quantify the discrete phase strains, phase volume fractions, and texture during such transformations. [copyright] [ital 1999 American Institute of Physics.

  15. Are Scaling Models for Production of Cosmogenic Nuclides Isotope Specific? - Implications from Secondary Cosmic Ray Neutron Spectra Measurements

    NASA Astrophysics Data System (ADS)

    Wilcken, K.

    2015-12-01

    A necessary requirement in studies using in-situ cosmogenic isotopes is to convert the measured isotope concentrations to exposure ages or geomorphic process rates. This involves using an accepted reference production rate, derived experimentally at a calibration site that has independent age control, and applying scaling factors for latitude and altitude in order to calculate a site-specific production rate. Throughout the development of the in-situ cosmogenic dating method, although reference production rates are necessarily nuclide specific, the scaling factors were not. The first atmospheric scaling model by Lal and Peters [1967] and others that followed, were based on the principle that as the cosmic ray particle flux attenuates with depth, the energy spectrum of nucleons of energy below 400 MeV becomes invariant at atmospheric depths greater than 200 g/cm2(altitude < 12 km). Hence scaling factors would thus be isotope independent resulting in production rate ratios of different isotopes to be invariant as a function of altitude. However, recent models by Argento et al. [2012, 2015] and Lifton et al. [2014] suggest that the energy spectrum is not invariant and scaling factors should in fact be isotope specific. The essential feature of the new models is that the focus is on generating the energy spectrum of cosmic-ray nucleons that is then converted into scaling factors with known cross sections. To benchmark the new scaling models I have collated secondary cosmic-ray neutron spectra measurements from the last 20 years and utilised these to calculate site-specific production rates. When using both ground-based and airborne neutron spectra measurements, the result follows the general trend predicted by the new models requiring isotope specific scaling. In contrast, using only the ground-based measurements, which range from sea-level to ~4000 m in altitude, no evidence for isotope specific scaling is apparent.

  16. X-ray Spectra of Accreting Neutron Stars in the Atoll and Z Subclasses

    NASA Astrophysics Data System (ADS)

    Remillard, Ronald A.; Lin, D.; Homan, J.

    2010-03-01

    We continue to find physical insights about atoll and Z sources by using a low-Comptonization spectral model for their soft states. In this decomposition, most of the radiation is thermal emission from two components: the accretion disk and the hotter boundary layer on the neutron star surface. Spectral analyses with RXTE then imply that atoll sources have nearly constant inner disk radius, consistent with a termination at the ISCO. This picture is largely confirmed in recent observations with Suzaku. On the other hand, Z sources show inner disk radii that increase with luminosity, suggesting the workings of the local Eddington limit. The flaring and normal branches can be understood as radius and advection instabilities, respectively, that disturb the Eddington-inflated disk. Patterns of spectral evolution are used to confirm the classification of GX13+1 as a Z source. We discuss implications for the origin of kHz QPOs. Finally, we compare the luminosity evolution of accreting black holes and neutron stars. This research was supported by NASA.

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

    NASA Astrophysics Data System (ADS)

    Holmes, Jesse Curtis

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

  18. Triaxiality of neutron-rich 84,86,88Ge from low-energy nuclear spectra

    NASA Astrophysics Data System (ADS)

    Lettmann, M.; Werner, V.; Pietralla, N.; Doornenbal, P.; Obertelli, A.; Rodríguez, T. R.; Sieja, K.; Authelet, G.; Baba, H.; Calvet, D.; Château, F.; Chen, S.; Corsi, A.; Delbart, A.; Gheller, J.-M.; Giganon, A.; Gillibert, A.; Lapoux, V.; Motobayashi, T.; Niikura, M.; Paul, N.; Roussé, J.-Y.; Sakurai, H.; Santamaria, C.; Steppenbeck, D.; Taniuchi, R.; Uesaka, T.; Ando, T.; Arici, T.; Blazhev, A.; Browne, F.; Bruce, A.; Caroll, R. J.; Chung, L. X.; Cortés, M. L.; Dewald, M.; Ding, B.; Flavigny, F.; Franchoo, S.; Górska, M.; Gottardo, A.; Jungclaus, A.; Lee, J.; Linh, B. D.; Liu, J.; Liu, Z.; Lizarazo, C.; Momiyama, S.; Moschner, K.; Nagamine, S.; Nakatsuka, N.; Nita, C.; Nobs, C. R.; Olivier, L.; Patel, Z.; Podolyák, Zs.; Rudigier, M.; Saito, T.; Shand, C.; Söderström, P.-A.; Stefan, I.; Vaquero, V.; Wimmer, K.; Xu, Z.

    2017-07-01

    γ -ray transitions between low-spin states of the neutron-rich 84,86,88Ge were measured by means of in-flight γ -ray spectroscopy at 270 MeV/u. Excited 61+,41,2 + , and 21,2 + states of Ge,8684 and 41+ and 21,2 + states of 88Ge were observed. Furthermore, a candidate for a 31+ state of 86Ge was identified. This state plays a key role in the discussion of ground-state triaxiality of 86Ge, along with other features of its low-energy level scheme. A new region of triaxially deformed nuclei is proposed in the Ge isotopic chain.

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

    SciTech Connect

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

    1984-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

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

    SciTech Connect

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

    2012-07-01

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

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

    PubMed Central

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

    2009-01-01

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

  3. High Energy Density Laboratory Astrophysics

    SciTech Connect

    Remington, B A

    2004-11-11

    High-energy-density (HED) physics refers broadly to the study of macroscopic collections of matter under extreme conditions of temperature and density. The experimental facilities most widely used for these studies are high-power lasers and magnetic-pinch generators. The HED physics pursued on these facilities is still in its infancy, yet new regimes of experimental science are emerging. Examples from astrophysics include work relevant to planetary interiors, supernovae, astrophysical jets, and accreting compact objects (such as neutron stars and black holes). In this paper, we will review a selection of recent results in this new field of HED laboratory astrophysics and provide a brief look ahead to the coming decade.

  4. High Energy Astronomy Observatory (HEAO)

    NASA Image and Video Library

    1982-01-01

    This artist's conception depicts the High Energy Astronomy Observatory (HEAO)-1 in orbit. The first observatory, designated HEAO-1, was launched on August 12, 1977 aboard an Atlas/Centaur launch vehicle and was designed to survey the sky for additional x-ray and gamma-ray sources as well as pinpointing their positions. The HEAO-1 was originally identified as HEAO-A but the designation was changed once the spacecraft achieved orbit. The HEAO project involved the launching of three unmarned scientific observatories into low Earth orbit between 1977 and 1979 to study some of the most intriguing mysteries of the universe; pulsars, black holes, neutron stars, and super nova. Hardware support for the imaging instruments was provided by American Science and Engineeing. The HEAO spacecraft were built by TRW, Inc. under project management of the Marshall Space Flight Center.

  5. Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy

    SciTech Connect

    Marrs, R E; Norman, E B; Burke, J T; Macri, R A; Shugart, H A; Browne, E; Smith, A R

    2007-11-15

    The beta-delayed gamma-ray spectra from the fission of {sup 235}U, {sup 238}U, and {sup 239}Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 minute to 14 hours. Spectra at all delay times contain sets of prominent gamma-ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  7. A tool for calculation of 7Li(p,n)7Be neutron source spectra below the three-body break-up reaction threshold

    NASA Astrophysics Data System (ADS)

    Pachuau, Rebecca; Lalremruata, B.; Otuka, N.; Hlondo, L. R.; Punte, L. R. M.; Thanga, H. H.

    2017-09-01

    We developed a new deterministic neutron source spectrum code EPEN - Energy of Proton Energy of Neutron - for a given lithium target thickness, sample angular coverage and proton energy from the reaction threshold to the three-body break-up threshold. The angular differential cross sections of the 7Li(p,n0)7Be and 7Li(p,n1)7Be reactions evaluated by Liskien and Paulsen were adopted above 1.95 MeV while the functional form suggested by Macklin and Gibbons was adopted for the 7Li(p,n0)7Be reaction cross section near threshold. The spectra obtained by EPEN are validated by the experimental spectra and also compared with the spectra predicted by two Monte Carlo codes, SimLiT and PINO. The results of comparison are discussed in detail.

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

    SciTech Connect

    Vaknin, David; Demmel, Franz

    2014-05-01

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

  9. High-energy detector

    DOEpatents

    Bolotnikov, Aleksey E [South Setauket, NY; Camarda, Giuseppe [Farmingville, NY; Cui, Yonggang [Upton, NY; James, Ralph B [Ridge, NY

    2011-11-22

    The preferred embodiments are directed to a high-energy detector that is electrically shielded using an anode, a cathode, and a conducting shield to substantially reduce or eliminate electrically unshielded area. The anode and the cathode are disposed at opposite ends of the detector and the conducting shield substantially surrounds at least a portion of the longitudinal surface of the detector. The conducting shield extends longitudinally to the anode end of the detector and substantially surrounds at least a portion of the detector. Signals read from one or more of the anode, cathode, and conducting shield can be used to determine the number of electrons that are liberated as a result of high-energy particles impinge on the detector. A correction technique can be implemented to correct for liberated electron that become trapped to improve the energy resolution of the high-energy detectors disclosed herein.

  10. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed by members of the USRA (Universities Space Research Association) contract team during the six months during the reporting period (10/95 - 3/96) and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, within the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA), X-ray Timing Experiment (XTE), X-ray Spectrometer (XRS), Astro-E, High Energy Astrophysics Science, Archive Research Center (HEASARC), and others.

  11. High Energy Astrophysics Program

    NASA Technical Reports Server (NTRS)

    1996-01-01

    This report reviews activities performed-by members of the USRA contract team during the six months of the reporting period and projected activities during the coming six months. Activities take place at the Goddard Space Flight Center, visiting the Laboratory for High Energy Astrophysics. Developments concern instrumentation, observation, data analysis, and theoretical work in Astrophysics. Missions supported include: Advanced Satellite for Cosmology and Astrophysics (ASCA); X-ray Timing Experiment (XTE); X-ray Spectrometer (XRS); Astro-E; High Energy Astrophysics Science Archive Research Center (HEASARC), and others.

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

    PubMed

    Pignol, J P; Slabbert, J

    2001-02-01

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

  13. High Energy Exoplanet Transits

    NASA Astrophysics Data System (ADS)

    Llama, Joe; Shkolnik, Evgenya L.

    2017-10-01

    X-ray and ultraviolet transits of exoplanets allow us to probe the atmospheres of these worlds. High energy transits have been shown to be deeper but also more variable than in the optical. By simulating exoplanet transits using high-energy observations of the Sun, we can test the limits of our ability to accurately measure the properties of these planets in the presence of stellar activity. We use both disk-resolved images of the Solar disk spanning soft X-rays, the ultraviolet, and the optical and also disk-integrated Sun-as-a-star observations of the Lyα irradiance to simulate transits over a wide wavelength range. We find that for stars with activity levels similar to the Sun, the planet-to-star radius ratio can be overestimated by up to 50% if the planet occults an active region at high energies. We also compare our simulations to high energy transits of WASP-12b, HD 189733, 55 Cnc b, and GJ 436b.

  14. High energy colliders

    SciTech Connect

    Palmer, R.B.; Gallardo, J.C.

    1997-02-01

    The authors consider the high energy physics advantages, disadvantages and luminosity requirements of hadron (pp, p{anti p}), lepton (e{sup +}e{sup {minus}}, {mu}{sup +}{mu}{sup {minus}}) and photon-photon colliders. Technical problems in obtaining increased energy in each type of machine are presented. The machines relative size are also discussed.

  15. High energy particle astronomy.

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Muller, R. A.; Smith, L. H.; Smoot, G. F.

    1972-01-01

    Discussion of techniques currently used in high energy particle astronomy for measuring charged and neutral cosmic rays and their isotope and momentum distribution. Derived from methods developed for accelerator experiments in particle physics, these techniques help perform important particle astronomy experiments pertaining to nuclear cosmic ray and gamma ray research, electron and position probes, and antimatter searches.

  16. High energy particle astronomy.

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Muller, R. A.; Smith, L. H.; Smoot, G. F.

    1972-01-01

    Discussion of techniques currently used in high energy particle astronomy for measuring charged and neutral cosmic rays and their isotope and momentum distribution. Derived from methods developed for accelerator experiments in particle physics, these techniques help perform important particle astronomy experiments pertaining to nuclear cosmic ray and gamma ray research, electron and position probes, and antimatter searches.

  17. Inorganic High Energy Oxidisers,

    DTIC Science & Technology

    properties may contribute significantly to the energy of the whole system. A book entitled ’Inorganic High - Energy Oxidisers’ by E.W. Lawless and I.C. Smith is the subject of this Essay Review by W.E. Batty.

  18. High Energy Astronomy Observatory

    NASA Technical Reports Server (NTRS)

    1980-01-01

    An overview of the High Energy Astronomy Observatory 2 contributions to X-ray astronomy is presented along with a brief description of the satellite and onboard telescope. Observations relating to galaxies and galactic clusters, black holes, supernova remnants, quasars, and cosmology are discussed.

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

    PubMed

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

    2007-11-01

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

  20. What is learned from high energy bursts and flares

    NASA Technical Reports Server (NTRS)

    Schneid, Edward J.

    1990-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) with its large Nal Total Absorption Shower Counter (TASC) has the scientific capability of performing spectroscopy of high energy cosmic gamma ray bursts and solar flares. EGRET, with a spectroscopy energy range from 0.6 to 140 MeV, provides an opportunity to increase the understanding of the high energy mechanisms of gamma ray bursts and solar flares. A likely interpretation of gamma ray burst sources is that they are rotating, magnetized neutron stars. High magnetic fields can influence the emission of high energy gamma rays, so observational spectroscopic data at high energies can provide information on the upper limits of the magnetic fields in the GRB regions of magnetized neutron stars. Likewise, spectroscopy of high energy gamma rays can provide information useful for deriving the flare proton spectrum which in turn can lead to an understanding of high energy solar flare particle acceleration mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  2. New prompt fission neutron spectra measurements in the 238U(n,f) reaction with a dedicated setup at LANSCE/WNR

    NASA Astrophysics Data System (ADS)

    Laurent, Benoit; Marini, Paola; Bélier, Gilbert; Bonnet, Thomas; Chatillon, Audrey; Taieb, Julien; Etasse, David; Devlin, Matthew; Haight, Robert

    2017-09-01

    A new prompt fission neutron spectra (PFNS) measurement in the 238U(n,f) reaction was performed at LANSCE/WNR facility. Evaluated data show discrepancies on the low (below 1 MeV) and high (above 5 MeV) energy parts in the PFNS for different major and minor actinides. The goal is to improve these measurements in a wide range of incident energy. The energy of the incoming neutron, inducing the fission, and the prompt neutron energies, are measured by time-of-flight method. A dedicated fission chamber was developed, in order to improve alpha-fission discrimination, timing resolution, actinide mass, and to reduce the amount of neutron scattering. To detect prompt neutrons, the 54 Chi-Nu scintillator cells array were surrounding the fission chamber. High statistics were recorded during this experiment, allowing a precise study of PFNS behavior as a function of incident neutron energy, from 1 MeV to 200 MeV. This experiment also showed that all the new tools developed to improve PFNS measurements are performing. Therefore, measurements of PFNS with others actinides such as 239Pu are planned.

  3. NIST Calibration of a Neutron Spectrometer ROSPEC

    PubMed Central

    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 252Cf, 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. PMID:27274944

  4. 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.

  5. High energy transients

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.

    1984-01-01

    A meeting was convened on the campus of the University of California at Santa Cruz during the two-week interval July 11 through July 22, 1983. Roughly 100 participants were chosen so as to give broad representation to all aspects of high energy transients. Ten morning review sessions were held in which invited speakers discussed the current status of observations and theory of the above subjects. Afternoon workshops were also held, usually more than one per day, to informally review various technical aspects of transients, confront shortcomings in theoretical models, and to propose productive courses for future research. Special attention was also given to the instrumentation used to study high energy transient and the characteristics and goals of a dedicated space mission to study transients in the next decade were determined. A listing of articles written by various members of the workshop is included.

  6. High energy from space

    NASA Technical Reports Server (NTRS)

    Margon, Bruce; Canizares, Claude; Catura, Richard C.; Clark, George W.; Fichtel, Carl E.; Friedman, Herbert; Giacconi, Riccardo; Grindlay, Jonathan E.; Helfand, David J.; Holt, Stephen S.

    1991-01-01

    The following subject areas are covered: (1) important scientific problems for high energy astrophysics (stellar activity, the interstellar medium in galaxies, supernovae and endpoints of stellar evolution, nucleosynthesis, relativistic plasmas and matter under extreme conditions, nature of gamma-bursts, identification of black holes, active nuclei, accretion physics, large-scale structures, intracluster medium, nature of dark matter, and the X- and gamma-ray background); (2) the existing experimental programs (Advanced X-Ray Astrophysics Facility (AXAF), Gamma Ray Observatory (GRO), X-Ray Timing Explorer (XTE), High Energy Transient Experiment (HETE), U.S. participation in foreign missions, and attached Shuttle and Space Station Freedom payloads); (3) major missions for the 1990's; (4) a new program of moderate missions; (5) new opportunities for small missions; (6) technology development issues; and (7) policy issues.

  7. High energy beam lines

    NASA Astrophysics Data System (ADS)

    Marchetto, M.; Laxdal, R. E.

    2014-01-01

    The ISAC post accelerator comprises an RFQ, DTL and SC-linac. The high energy beam lines connect the linear accelerators as well as deliver the accelerated beams to two different experimental areas. The medium energy beam transport (MEBT) line connects the RFQ to the DTL. The high energy beam transport (HEBT) line connects the DTL to the ISAC-I experimental stations (DRAGON, TUDA-I, GPS). The DTL to superconducting beam (DSB) transport line connects the ISAC-I and ISAC-II linacs. The superconducting energy beam transport (SEBT) line connects the SC linac to the ISAC-II experimental station (TUDA-II, HERACLES, TIGRESS, EMMA and GPS). All these lines have the function of transporting and matching the beams to the downstream sections by manipulating the transverse and longitudinal phase space. They also contain diagnostic devices to measure the beam properties.

  8. Monte Carlo characterizations mapping of the (γ,n) and (n,γ) photonuclear reactions in the high energy X-ray radiation therapy

    PubMed Central

    Ghiasi, Hosein

    2013-01-01

    Aim The aim of this work was to map the characteristics of (n,γ) and (γ,n) reactions in a high energy photon radiation therapy. Background Photoneutrons produced in the high energy X-Ray radiation therapy may damage patients and staff. It is due to high RBE of the produced neutrons according to their energy and isotropic emission. Characterization of the photoneutrons can help us in appropriate shielding. Materials and methods This study focused on the photoneutron and capture gamma ray phenomena. Characteristics such as dose value, fluence and spectra of both the neutrons and the by produced prompt gamma ray were described. Results and discussion Neutron and prompt gamma spectra in different points showed the neutrons to be thermalized when increasing the distance from the linac. Energy of the neutrons changed from about 0.6 MeV at the isocentre to around 10−08 MeV at the outer door position. Although the neutrons were found as fast neutrons, their spectra showed they were thermal neutrons at the outer door position. Additionally, it was seen that the energy of the gamma rays is higher than the scattered X-ray energy. The energy of gamma rays was seen to be up to 10 MeV while the linac photons had energy lower than 1 MeV. Neutron source strength obtained in this work was in good agreement with the published data, which may be a confirmation of our simulation accuracy. Conclusion The study showed that the Monte Carlo simulation can be applied in the radiotherapy and industrial radiation works as a useful and precise estimator. We also concluded that the dose from the prompt gamma ray at the outer door location is higher than the scattered radiation from the linac and should be considered in the shielding. PMID:24936317

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

    NASA Astrophysics Data System (ADS)

    Büyükuslu, H.; Kaplan, A.; Tel, E.; Aydin, A.; Yıldırım, G.

    2010-02-01

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

  10. Theoretical High Energy Physics

    SciTech Connect

    Christ, Norman H.; Weinberg, Erick J.

    2014-07-14

    we provide reports from each of the six faculty supported by the Department of Energy High Energy Physics Theory grant at Columbia University. Each is followed by a bibliography of the references cited. A complete list of all of the publications in the 12/1/2010-04/30/2014 period resulting from research supported by this grant is provided in the following section. The final section lists the Ph.D. dissertations based on research supported by the grant that were submitted during this period.

  11. High energy electron cooling

    SciTech Connect

    Parkhomchuk, V.

    1997-09-01

    High energy electron cooling requires a very cold electron beam. The questions of using electron cooling with and without a magnetic field are presented for discussion at this workshop. The electron cooling method was suggested by G. Budker in the middle sixties. The original idea of the electron cooling was published in 1966. The design activities for the NAP-M project was started in November 1971 and the first run using a proton beam occurred in September 1973. The first experiment with both electron and proton beams was started in May 1974. In this experiment good result was achieved very close to theoretical prediction for a usual two component plasma heat exchange.

  12. A Monte Carlo model for out-of-field dose calculation from high-energy photon therapy.

    PubMed

    Kry, Stephen F; Titt, Uwe; Followill, David; Pönisch, Falk; Vassiliev, Oleg N; White, R Allen; Stovall, Marilyn; Salehpour, Mohammad

    2007-09-01

    As cancer therapy becomes more efficacious and patients survive longer, the potential for late effects increases, including effects induced by radiation dose delivered away from the treatment site. This out-of-field radiation is of particular concern with high-energy radiotherapy, as neutrons are produced in the accelerator head. We recently developed an accurate Monte Carlo model of a Varian 2100 accelerator using MCNPX for calculating the dose away from the treatment field resulting from low-energy therapy. In this study, we expanded and validated our Monte Carlo model for high-energy (18 MV) photon therapy, including both photons and neutrons. Simulated out-of-field photon doses were compared with measurements made with thermoluminescent dosimeters in an acrylic phantom up to 55 cm from the central axis. Simulated neutron fluences and energy spectra were compared with measurements using moderated gold foil activation in moderators and data from the literature. The average local difference between the calculated and measured photon dose was 17%, including doses as low as 0.01% of the central axis dose. The out-of-field photon dose varied substantially with field size and distance from the edge of the field but varied little with depth in the phantom, except at depths shallower than 3 cm, where the dose sharply increased. On average, the difference between the simulated and measured neutron fluences was 19% and good agreement was observed with the neutron spectra. The neutron dose equivalent varied little with field size or distance from the central axis but decreased with depth in the phantom. Neutrons were the dominant component of the out-of-field dose equivalent for shallow depths and large distances from the edge of the treatment field. This Monte Carlo model is useful to both physicists and clinicians when evaluating out-of-field doses and associated potential risks.

  13. Comparative study of Monte Carlo particle transport code PHITS and nuclear data processing code NJOY for recoil cross section spectra under neutron irradiation

    NASA Astrophysics Data System (ADS)

    Iwamoto, Yosuke; Ogawa, Tatsuhiko

    2017-04-01

    Because primary knock-on atoms (PKAs) create point defects and clusters in materials that are irradiated with neutrons, it is important to validate the calculations of recoil cross section spectra that are used to estimate radiation damage in materials. Here, the recoil cross section spectra of fission- and fusion-relevant materials were calculated using the Event Generator Mode (EGM) of the Particle and Heavy Ion Transport code System (PHITS) and also using the data processing code NJOY2012 with the nuclear data libraries TENDL2015, ENDF/BVII.1, and JEFF3.2. The heating number, which is the integral of the recoil cross section spectra, was also calculated using PHITS-EGM and compared with data extracted from the ACE files of TENDL2015, ENDF/BVII.1, and JENDL4.0. In general, only a small difference was found between the PKA spectra of PHITS + TENDL2015 and NJOY + TENDL2015. From analyzing the recoil cross section spectra extracted from the nuclear data libraries using NJOY2012, we found that the recoil cross section spectra were incorrect for 72Ge, 75As, 89Y, and 109Ag in the ENDF/B-VII.1 library, and for 90Zr and 55Mn in the JEFF3.2 library. From analyzing the heating number, we found that the data extracted from the ACE file of TENDL2015 for all nuclides were problematic in the neutron capture region because of incorrect data regarding the emitted gamma energy. However, PHITS + TENDL2015 can calculate PKA spectra and heating numbers correctly.

  14. Introduction to High-Energy Astrophysics

    NASA Astrophysics Data System (ADS)

    Rosswog, Stephan; Bruggen, Marcus

    2003-04-01

    High-energy astrophysics covers cosmic phenomena that occur under the most extreme physical conditions. It explores the most violent events in the Universe: the explosion of stars, matter falling into black holes, and gamma-ray bursts - the most luminous explosions since the Big Bang. Driven by a wealth of new observations, the last decade has seen a large leap forward in our understanding of these phenomena. Exploring modern topics of high-energy astrophysics, such as supernovae, neutron stars, compact binary systems, gamma-ray bursts, and active galactic nuclei, this textbook is ideal for undergraduate students in high-energy astrophysics. It is a self-supporting, timely overview of this exciting field of research. Assuming a familiarity with basic physics, it introduces all other concepts, such as gas dynamics or radiation processes, in an instructive way. An extended appendix gives an overview of some of the most important high-energy astrophysics instruments, and each chapter ends with exercises.• New, up-to-date, introductory textbook providing a broad overview of high-energy phenomena and the many advances in our knowledge gained over the last decade • Written especially for undergraduate teaching use, it introduces the necessary physics and includes many exercises • This book fills a valuable niche at the advanced undergraduate level, providing professors with a new modern introduction to the subject

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

    NASA Astrophysics Data System (ADS)

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

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

  16. Prospects at high energies

    SciTech Connect

    Quigg, C.

    1988-11-01

    I discuss some possibilities for neutrino experiments in the fixed-target environment of the SPS, Tevatron, and UNK, with their primary proton beams of 0.4, 0.9, and 3.0 TeV. The emphasis is on unfinished business: issues that have been recognized for some time, but not yet resolved. Then I turn to prospects for proton-proton colliders to explore the 1-TeV scale. I review the motivation for new physics in the neighborhood of 1 TeV and mention some discovery possibilities for high-energy, high-luminosity hadron colliders and the implications they would have for neutrino physics. I raise the possibility of the direct study of neutrino interactions in hadron colliders. I close with a report on the status of the SSC project. 38 refs., 17 figs.

  17. Near-Field High-Energy Spectroscopic Gamma Imaging Using a Rotation Modulation Collimator.

    PubMed

    Sharma, Amy C; Turkington, Timothy G; Tourassi, Georgia D; Floyd, Carey E

    2008-11-01

    Certain trace elements are vital to the body and elemental imbalances can be indicators of certain diseases including cancer and liver diseases. Neutron Stimulated Emission Computed Tomography (NSECT) is being developed as spectroscopic imaging technique to non-invasively and non-destructively measure and image elemental concentrations within the body. A region of interest is illuminated via a high-energy beam of neutrons that scatter inelastically with elemental nuclei within the body. The excited nuclei then relax by emitting characteristic gamma rays. Acquiring the gamma spectrum in a tomographic manner allows not only the identification of elements, but also the formation of images representing spatial distributions of specific elements. We are developing a high-energy position-sensitive gamma camera that allows full illumination of the entire region of interest. Because current scintillation crystal based position-sensitive gamma cameras operate in too low of an energy range, we are adapting high-energy gamma imaging techniques used in space-based imaging. A High Purity Germanium (HPGe) detector provides high-resolution energy spectra while a rotating modulation collimator (RMC) placed in front of the detector modulates the incoming signal to provide spatial information. The purpose of this manuscript is to describe the near-field RMC geometry, which varies greatly from the infinite-focus space-based applications, and how it modulates the incident gamma flux. A simple geometric model is presented and then used to reconstruct two-dimensional planar images of both simulated point sources and extended sources.

  18. Supernova pointing with low- and high-energy neutrino detectors

    NASA Astrophysics Data System (ADS)

    Tomàs, R.; Semikoz, D.; Raffelt, G. G.; Kachelrieß, M.; Dighe, A. S.

    2003-11-01

    A future galactic SN can be located several hours before the optical explosion through the MeV-neutrino burst, exploiting the directionality of ν-e scattering in a water Cherenkov detector such as Super-Kamiokande. We study the statistical efficiency of different methods for extracting the SN direction and identify a simple approach that is nearly optimal, yet independent of the exact SN neutrino spectra. We use this method to quantify the increase in the pointing accuracy by the addition of gadolinium to water, which tags neutrons from the inverse beta decay background. We also study the dependence of the pointing accuracy on neutrino mixing scenarios and initial spectra. We find that in the “worst case” scenario the pointing accuracy is 8° at 95% C.L. in the absence of tagging, which improves to 3° with a tagging efficiency of 95%. At a megaton detector, this accuracy can be as good as 0.6°. A TeV-neutrino burst is also expected to be emitted contemporaneously with the SN optical explosion, which may locate the SN to within a few tenths of a degree at a future km2 high-energy neutrino telescope. If the SN is not seen in the electromagnetic spectrum, locating it in the sky through neutrinos is crucial for identifying the Earth matter effects on SN neutrino oscillations.

  19. Leading neutron production at HERA in the color dipole approach

    NASA Astrophysics Data System (ADS)

    Carvalho, F.; Gonçalves, V. P.; Spiering, D.; Navarra, F. S.

    2016-03-01

    In this work we study leading neutron production in e + p → e + n + X collisions at high energies and calculate the Feynman xL distribution of these neutrons. The differential cross section is written in terms of the pion flux and of the photon-pion total cross section. We describe this process using the color dipole formalism and, assuming the validity of the additive quark model, we relate the dipole-pion with the well determined dipoleproton cross section. In this formalism we can estimate the impact of the QCD dynamics at high energies as well as the contribution of gluon saturation effects to leading neutron production. With the parameters constrained by other phenomenological information, we are able to reproduce the basic features of the recently released H1 leading neutron spectra.

  20. From QCD-based hard-scattering to nonextensive statistical mechanical descriptions of transverse momentum spectra in high-energy pp and pp¯ collisions

    SciTech Connect

    Wong, Cheuk-Yin; Wilk, Grzegorz; Cirto, Leonardo J. L.; Tsallis, Constantino

    2015-06-22

    Transverse spectra of both jets and hadrons obtained in high-energy $pp$ and $p\\bar p $ collisions at central rapidity exhibit power-law behavior of $1/p_T^n$ at high $p_T$. The power index $n$ is 4-5 for jet production and is slightly greater for hadron production. Furthermore, the hadron spectra spanning over 14 orders of magnitude down to the lowest $p_T$ region in $pp$ collisions at LHC can be adequately described by a single nonextensive statistical mechanical distribution that is widely used in other branches of science. This suggests indirectly the dominance of the hard-scattering process over essentially the whole $p_T$ region at central rapidity in $pp$ collisions at LHC. We show here direct evidences of such a dominance of the hard-scattering process by investigating the power index of UA1 jet spectra over an extended $p_T$ region and the two-particle correlation data of the STAR and PHENIX Collaborations in high-energy $pp$ and $p \\bar p$ collisions at central rapidity. We then study how the showering of the hard-scattering product partons alters the power index of the hadron spectra and leads to a hadron distribution that can be cast into a single-particle non-extensive statistical mechanical distribution. Lastly, because of such a connection, the non-extensive statistical mechanical distribution can be considered as a lowest-order approximation of the hard-scattering of partons followed by the subsequent process of parton showering that turns the jets into hadrons, in high energy $pp$ and $p\\bar p$ collisions.

  1. High-energy PIXE: quantitative analysis

    NASA Astrophysics Data System (ADS)

    Denker, A.; Opitz-Coutureau, J.; Campbell, J. L.; Maxwell, J. A.; Hopman, T.

    2004-06-01

    In recent years, high-energy PIXE was applied successfully for qualitative analysis on art and archaeological objects, e.g. coins, bronzes, sculptures, brooches. However, in the absence of software for quantitative analysis the full benefit inherent in the PIXE technique was not obtained. For example, a bronze could easily be distinguished from a brass, but the concentrations could not be rigorously compared within a set of bronzes. In this paper, the first quantitative analysis by high-energy PIXE is presented. The Guelph PIXE Software Package GUPIX has been extended to proton energies up to 100 MeV, so that high-energy PIXE spectra can be evaluated and concentrations derived. Measurements on metal and alloy standards at two different proton energies have been performed and the obtained compositions were compared to the certified values. The results will be presented and deviations discussed.

  2. FSU High Energy Physics

    SciTech Connect

    Prosper, Harrison B.; Adams, Todd; Askew, Andrew; Berg, Bernd; Blessing, Susan K.; Okui, Takemichi; Owens, Joseph F.; Reina, Laura; Wahl, Horst D.

    2014-12-01

    The High Energy Physics group at Florida State University (FSU), which was established in 1958, is engaged in the study of the fundamental constituents of matter and the laws by which they interact. The group comprises theoretical and experimental physicists, who sometimes collaborate on projects of mutual interest. The report highlights the main recent achievements of the group. Significant, recent, achievements of the group’s theoretical physicists include progress in making precise predictions in the theory of the Higgs boson and its associated processes, and in the theoretical understanding of mathematical quantities called parton distribution functions that are related to the structure of composite particles such as the proton. These functions are needed to compare data from particle collisions, such as the proton-proton collisions at the CERN Large Hadron Collider (LHC), with theoretical predictions. The report also describes the progress in providing analogous functions for heavy nuclei, which find application in neutrino physics. The report highlights progress in understanding quantum field theory on a lattice of points in space and time (an area of study called lattice field theory), the progress in constructing several theories of potential new physics that can be tested at the LHC, and interesting new ideas in the theory of the inflationary expansion of the very early universe. The focus of the experimental physicists is the Compact Muon Solenoid (CMS) experiment at CERN. The report, however, also includes results from the D0 experiment at Fermilab to which the group made numerous contributions over a period of many years. The experimental group is particularly interested in looking for new physics at the LHC that may provide the necessary insight to extend the standard model (SM) of particle physics. Indeed, the search for new physics is the primary task of contemporary particle physics, one motivated by the need to explain certain facts, such as the

  3. High energy physics

    SciTech Connect

    Kernan, A.; Shen, B.C.; Ma, E.

    1997-07-01

    This proposal is for the continuation of the High Energy Physics program at the University of California at Riverside. In hadron collider physics the authors will complete their transition from experiment UA1 at CERN to the DZERO experiment at Fermilab. On experiment UA1 their effort will concentrate on data analysis at Riverside. At Fermilab they will coordinate the high voltage system for all detector elements. They will also carry out hardware/software development for the D0 muon detector. The TPC/Two-Gamma experiment has completed its present phase of data-taking after accumulating 160 pb{sup {minus}}1 of luminosity. The UC Riverside group will continue data and physics analysis and make minor hardware improvement for the high luminosity run. The UC Riverside group is participating in design and implementation of the data acquisition system for the OPAL experiment at LEP. Mechanical and electronics construction of the OPAL hadron calorimeter strip readout system is proceeding on schedule. Data analysis and Monte Carlo detector simulation efforts are proceeding in preparation for the first physics run when IEP operation comenses in fall 1989.

  4. High energy physics

    SciTech Connect

    Kernan, A.; Shen, B.C.; Ma, E.

    1997-07-01

    This proposal is for the continuation of the High Energy Physics Program at the University of California, Riverside. In 1990, we will concentrate on analysis of LEP data from the OPAL detector. We expect to record 10{sup 5} Z`s by the end of 1989 and 10{sup 6} in 1990. This data will be used to measure the number of quark-lepton families in the universe. In the second half of 1990 we will also be occupied with the installation of the D-Zero detector in the Tevatron Collider and the preparation of software for the 1991 run. A new initiative made possible by generous university support is a laboratory for detector development at UCR. The focus will be on silicon strip tracking detectors both for the D-Zero upgrade and for SSC physics. The theory program will pursue further various mass-generating radiative mechanisms for understanding small quark and lepton masses as well as some novel phenomenological aspects of supersymmetry.

  5. High Energy Astrophysics Mission

    NASA Technical Reports Server (NTRS)

    White, Nicholas E.; Ormes, Jonathan F. (Technical Monitor)

    2000-01-01

    The nature of gravity and its relationship to the other three forces and to quantum theory is one of the major challenges facing us as we begin the new century. In order to make progress we must challenge the current theories by observing the effects of gravity under the most extreme conditions possible. Black holes represent one extreme, where the laws of physics as we understand them break down. The Universe as whole is another extreme, where its evolution and fate is dominated by the gravitational influence of dark matter and the nature of the Cosmological constant. The early universe represents a third extreme, where it is thought that gravity may somehow be unified with the other forces. NASA's "Cosmic Journeys" program is part of a NASA/NSF/DoE tri-agency initiative designed to observe the extremes of gravity throughout the universe. This program will probe the nature of black holes, ultimately obtaining a direct image of the event horizon. It will investigate the large scale structure of the Universe to constrain the location and nature of dark matter and the nature of the cosmological constant. Finally it will search for and study the highest energy processes, that approach those found in the early universe. I will outline the High Energy Astrophysics part of this program.

  6. High Energy Astrophysics Mission

    NASA Technical Reports Server (NTRS)

    White, Nicholas E.; Ormes, Jonathan F. (Technical Monitor)

    2000-01-01

    The nature of gravity and its relationship to the other three forces and to quantum theory is one of the major challenges facing us as we begin the new century. In order to make progress we must challenge the current theories by observing the effects of gravity under the most extreme conditions possible. Black holes represent one extreme, where the laws of physics as we understand them break down. The Universe as whole is another extreme, where its evolution and fate is dominated by the gravitational influence of dark matter and the nature of the Cosmological constant. The early universe represents a third extreme, where it is thought that gravity may somehow be unified with the other forces. NASA's "Cosmic Journeys" program is part of a NASA/NSF/DoE tri-agency initiative designed to observe the extremes of gravity throughout the universe. This program will probe the nature of black holes, ultimately obtaining a direct image of the event horizon. It will investigate the large scale structure of the Universe to constrain the location and nature of dark matter and the nature of the cosmological constant. Finally it will search for and study the highest energy processes, that approach those found in the early universe. I will outline the High Energy Astrophysics part of this program.

  7. 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.

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

    SciTech Connect

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

    1985-08-01

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

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

    SciTech Connect

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

    2015-05-28

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

  10. Measurement of keV-neutron capture cross sections and capture gamma-ray spectra of Cs-133 and I-127

    NASA Astrophysics Data System (ADS)

    Umezawa, Seigo; Igashira, Masayuki; Katabuchi, Tatuya; Dominic, Moraru; Yanagida, Shotaro; Okamiya, Tomohiro

    2017-09-01

    The neutron capture cross sections and the capture gamma-ray spectra of 127I and 133Cs at incident neutron energies from 15 to 100 keV have been measured by the time-of-flight method. Capture gamma-rays were detected with an anti-Compton NaI(Tl) spectrometer, and the pulse-height weighting technique was applied to derive capture yields. The capture cross sections of 127I and 133Cs were determined using the standard capture cross section of 197Au. The total errors of the cross sections were 3.8-5.1%. The obtained cross sections were compared with evaluated values in JENDL-4.0 and ENDF/B-VII.1. For 127I, the energy dependence is different between the present results and the evaluations. For 133Cs, the evaluated values in JENDL-4.0 agree with the present results but the evaluated values in ENDF/B-VII.1 are smaller than the present results by 14%-18%. The capture gamma-ray spectra of 133Cs and 127I were derived by unfolding the pulse height spectra with detector response functions.

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

    SciTech Connect

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

    2013-11-06

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

  12. High Energy Astronomy Observatory (HEAO)

    NASA Image and Video Library

    1975-07-01

    This illustration is a schematic of the High Energy Astronomy Observatory (HEAO)-2 and its experiments. It shows the focal plane instruments (at the right) plus the associated electronics for operating the telescope as it transmitted its observations to the ground. A fifth instrument, the Monitor Proportional Counter, is located near the front of the telescope. Four separate astronomical instruments are located at the focus of this telescope and they could be interchanged for different types of observations as the observatory pointed at interesting areas of the Sky. Two of these instruments produced images; a High Resolution Imaging Detector and an Imaging Proportional Counter. The other two instruments, the Solid State Spectrometer and the Crystal Spectrometer, measured the spectra of x-ray objects. A fifth instrument, the Monitor Proportional Counter, continuously viewed space independently to study a wider band of x-ray wavelengths and to examine the rapid time variations in the sources. The HEAO-2 was nicknamed the Einstein Observatory by its scientific experimenters in honor of the centernial of the birth of Albert Einstein, whose concepts of relativity and gravitation have influenced much of modern astrophysics, particularly x-ray astronomy. The HEAO-2, designed and developed by TRW, Inc. under the project management of the Marshall Space Flight Center, was launched aboard an Atlas/Centaur launch vehicle on November 13, 1978. The HEAO-2 was originally identified as HEAO-B but the designation was changed once the spacecraft achieved orbit.

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

    SciTech Connect

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

    2009-03-10

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

  14. 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.

  15. (High energy physics)

    SciTech Connect

    Bonner, B.E.; Roberts, J.B. Jr.

    1991-09-01

    An intense analysis effort on the data we obtained in a seven month run on E704 last year has produced a flood of new results on polarization effects in particle production at 200 GeV/c. We are fortunate to be able to report in detail on those results. Our other Fermilab experiment, E683 (photoproduction of jets) has been delayed an unbelievable amount of time by Fermilab schedule slippages. It was scheduled and ready for beam two years ago As this report is being written, we have been running for two months and are expecting four months of production data taking. In this report we show some of our preliminary results. In addition we are near the end of a six month run on our CERN experiment, NA47 (SMC) which will measure the spin dependent structure functions for the proton and neutron. It is with a sense of relief, mixed with pride, that we report that all the equipment which we constructed for that experiment is currently working as designed. The random coincidence of accelerator schedules has left us slightly dazed, but all experiments are getting done and analyzed in a timely fashion. As members of the Solenoidal Detector Collaboration, we have been preparing for the only currently approved experiment at the SSC. Here we report on our scintillating fiber tracker design and simulation activities. In addition we report the results of our investigation of the detector response to heavy Z particles. Since our last report, we have joined the D0 collaboration with the primary aim of contributing to the D0 upgrade over the next few years. It is also important for us to gain experience in collider physics during the period leading up to the SDC turn-on.

  16. GEM Applications Outside High Energy Physics

    NASA Astrophysics Data System (ADS)

    Pinto, Serge Duarte

    2013-04-01

    From its invention in 1997, the Gas Electron Multiplier (GEM) has been applied in nuclear and high energy physics experiments. Over time however, other applications have also exploited the favorable properties of GEMs. The use of GEMs in these applications will be explained in principle and practice. This paper reviews applications in research, beam instrumentation and homeland security. The detectors described measure neutral radiations such as photons, x-rays, gamma rays and neutrons, as well as all kinds of charged radiation. This paper provides an overview of the still expanding range of possibilities of this versatile detector concept.

  17. High-energy proton radiation belt.

    NASA Technical Reports Server (NTRS)

    White, R. S.

    1973-01-01

    The experiments and theories to explain the high-energy protons trapped in the earth's radiation belt are reviewed. The theory of cosmic ray albedo neutron decay injection of protons into the radiation belt is discussed. Radial diffusion and change in the earth's dipole moment are considered along with losses of protons by ionization and nuclear collision. It is found that the measured albedo neutron escape current is sufficient to supply trapped protons above 30 MeV. The theoretical calculations of the trapped protons are in agreement with the measurements for L less than or equal to 1.7 both on and off the equator. For L greater than or equal to 1.7, additional trapped proton differential energy measurements should be made before the theory can be adequately tested. It appears that an additional loss mechanism such as pitch angle scattering may be required.

  18. 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.

  19. The Need for Precise and Well-documented Experimental Data on Prompt Fission Neutron Spectra from Neutron-induced Fission of {sup 239}Pu

    SciTech Connect

    Neudecker, D. Taddeucci, T.N.; Haight, R.C.; Lee, H.Y.; White, M.C.; Rising, M.E.

    2016-01-15

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

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

    DOE PAGES

    Neudecker, Denise; Taddeucci, Terry Nicholas; Haight, Robert Cameron; ...

    2016-01-06

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