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Sample records for heavy neutron clusters

  1. The Chemical Evolution of Heavy Elements in Globular Clusters

    NASA Astrophysics Data System (ADS)

    Shingles, Luke J.; Karakas, Amanda I.; Hirschi, Raphael

    2014-01-01

    We present preliminary results from a chemical evolution model that tracks the composition of heavy elements beyond iron in a globular cluster. The heavy elements can be used as tracers of the nucleosynthetic events that defined the formation and evolution of star clusters in the early Universe. In particular, the chemical evolution model focuses on the hypothesis that rapidly-rotating massive stars produced the heavy elements via the slow neutron-capture process and seeded the proto-cluster while the stars we see today were still forming. We compare our model with heavy element abundances in M4 and M5, and M22. Our results are strongly dependent on the highly uncertain rate of the 17O(α,γ)21Ne reaction, which determines the strength of 16O as a neutron poison. We find that the [Pb/Ba] ratio is too low to match the empirical value, which might suggest that a contribution from AGB stars is required.

  2. HEAVY WATER MODERATED NEUTRONIC REACTOR

    DOEpatents

    Szilard, L.

    1958-04-29

    A nuclear reactor of the type which utilizes uranium fuel elements and a liquid coolant is described. The fuel elements are in the form of elongated tubes and are disposed within outer tubes extending through a tank containing heavy water, which acts as a moderator. The ends of the fuel tubes are connected by inlet and discharge headers, and liquid bismuth is circulated between the headers and through the fuel tubes for cooling. Helium is circulated through the annular space between the outer tubes in the tank and the fuel tubes to cool the water moderator to prevent boiling. The fuel tubes are covered with a steel lining, and suitable control means, heat exchange means, and pumping means for the coolants are provided to complete the reactor assembly.

  3. Clusters in neutron-rich light nuclei

    NASA Astrophysics Data System (ADS)

    Jelavić Malenica, D.; Milin, M.; Di Pietro, A.; Figuera, P.; Lattuada, M.; Miljanić, D.; Musumarra, A.; Pellegriti, M. G.; Prepolec, L.; Scuderi, V.; Skukan, N.; Soić, N.; Torresi, D.; Uroić, M.

    2016-05-01

    Due to their high selectivity, transfer and sequential decay reactions are powerful tools for studies of both single particle (nucleon) and cluster states in light nuclei. Their use is particularly simple for investigations of α-particle clustering (because α-particle has Jπ=0+, which simplifies spin and parity assignments to observed cluster states), but they are also easily applicable to other types of clustering. Recent results on clustering in neutron-rich isotopes of beryllium, boron and carbon obtained measuring the 10B+10B reactions (at 50 and 72 MeV) are presented. The highly efficient and segmented detector systems used, built from 4 Double Sided Silicon Strip Detectors (DSSSD) allowed detection of double and multiple coincidences and, in that way, studies of states populated in transfer reactions, as well as their sequential decay.

  4. Production of 14 MeV neutrons by heavy ions

    DOEpatents

    Brugger, Robert M.; Miller, Lowell G.; Young, Robert C.

    1977-01-01

    This invention relates to a neutron generator and a method for the production of 14 MeV neutrons. Heavy ions are accelerated to impinge upon a target mixture of deuterium and tritium to produce recoil atoms of deuterium and tritium. These recoil atoms have a sufficient energy such that they interact with other atoms of tritium or deuterium in the target mixture to produce approximately 14 MeV neutrons.

  5. Fusion neutron yield from a laser-irradiated heavy-water spray

    SciTech Connect

    Ter-Avetisyan, S.; Schnuerer, M.; Hilscher, D.; Jahnke, U.; Busch, S.; Nickles, P.V.; Sandner, W.

    2005-01-01

    The fusion neutron yield from a laser-irradiated heavy-water (D{sub 2}O) spray target was studied. Heavy-water droplets of about 150 nm diameter in the spray were exposed to 35 fs laser pulses at an intensity of 1x10{sup 19} W/cm{sup 2}. Due to the 10-50 times bigger size of the spray droplets compared to usual cluster sizes, deuterons are accelerated to considerably higher kinetic energies of up to 1 MeV. Neutrons are generated by the deuterons escaping from the plasma and initiating a fusion reaction within the surrounding cold plume of the spray jet. For each 0.6 J of laser pulse energy, 6x10{sup 3} neutrons are produced by about 10{sup 11} accelerated deuterons. This corresponds to a D(d,n) reaction probability of about 6x10{sup -8}. Compared to cluster targets, the reaction probability in the spray target is found to be two orders of magnitude larger. This finding apparently is due to both the considerably higher deuteron energies and the larger effective target thickness in the spray target. The measured neutron yield per accelerated deuteron [i.e., the D(d,n) reaction probability], is employed to compare and extrapolate the neutron emission characteristics from different target arrangements.

  6. Formation of Heavy and Superheavy Neutron Rich Nuclei

    SciTech Connect

    Zagrebaev, Valery; Greiner, Walter

    2010-04-30

    A new way is proposed to discover and examine unknown neutron-rich heavy and superheavy nuclei at the 'north-east' part of the nuclear map. The present limits of the upper part of the nuclear map is very close to stability while the unexplored area of heavy neutron-rich nuclides to the east of the stability line (also those located along the neutron closed shell N = 126) is extremely important for nuclear astrophysics investigations and for the understanding of the r-process of astrophysical nucleo-genesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions using a gain given by the shell effects. This finding may spur new studies at heavy ion facilities and should have significant impact for future experiments. The use of the multi-nucleon transfer reactions in low-energy collisions of heavy actinide nuclei gives us also the only chance to approach the 'island of stability' of superheavy elements. A possibility for a three-body decay (heavy ternary fission) is predicted for superheavy nuclei.

  7. A Semi-microscopic Approach to Clusterization in Heavy Nuclei

    SciTech Connect

    Darai, J.; Cseh, J.; Antonenko, N. V.; Jolos, R. V.; Algora, A.; Hess, P. O.; Scheid, W.

    2009-08-26

    We present a semimicroscopic approach to clusterization in heavy nuclei. The method is largely based on symmetry-considerations. As an example we determine the possible binary clusterizations of the shape isomers of the {sup 56}Ni nucleus. We combine our structure-considerations with energy-calculations.

  8. Production of new neutron-rich heavy nuclei

    SciTech Connect

    Zagrebaev, Valery; Greiner, Walter

    2009-03-04

    A new way is found to discover and examine unknown neutron-rich heavy nuclei at the 'north-east' part of the nuclear map. This 'blank spot' of the nuclear map can be reached neither in fusion--fission reactions nor in fragmentation processes. The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N = 126(to the east of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. A novel idea is proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions with stable beams. The estimated yields of neutron-rich nuclei are found to be rather high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of {sup 136}Xe with {sup 208}Pb. This finding may spur new studies at heavy-ion facilities and should have significant impact on future experiments.

  9. Clustered DNA damage induced by heavy ion particles.

    PubMed

    Terato, Hiroaki; Ide, Hiroshi

    2004-12-01

    Clustered DNA damage (locally multiply damaged site) is thought to be a critical lesion caused by ionizing radiation, and high LET radiation such as heavy ion particles is believed to produce high yields of such damage. Since heavy ion particles are major components of ionizing radiation in a space environment, it is important to clarify the chemical nature and biological consequences of clustered DNA damage and its relationship to the health effects of exposure to high LET particles in humans. The concept of clustered DNA damage emerged around 1980, but only recently has become the subject of experimental studies. In this article, we review methods used to detect clustered DNA damage, and the current status of our understanding of the chemical nature and repair of clustered DNA damage. PMID:15858387

  10. Colliding Neutron Stars as the Source of Heavy Elements

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Where do the heavy elements the chemical elements beyond iron in our universe come from? One of the primary candidate sources is the merger of two neutron stars, but recent observations have cast doubt on this model. Can neutron-star mergers really be responsible?Elements from Collisions?Periodic table showing the origin of each chemical element. Those produced by the r-process are shaded orange and attributed to supernovae in this image; though supernovae are one proposed source of r-process elements, an alternative source is the merger of two neutron stars. [Cmglee]When a binary-neutron-star system inspirals and the two neutron stars smash into each other, a shower of neutrons are released. These neutrons are thought to bombard the surrounding atoms, rapidly producing heavy elements in what is known as r-process nucleosynthesis.So could these mergers be responsible for producing the majority of the universes heavy r-process elements? Proponents of this model argue that its supported by observations. The overall amount of heavy r-process material in the Milky Way, for instance, is consistent with the expected ejection amounts from mergers, based both on predicted merger rates for neutron stars in the galaxy, and on the observed rates of soft gamma-ray bursts (which are thought to accompany double-neutron-star mergers).Challenges from Ultra-Faint DwarfsRecently, however, r-process elements have been observed in ultra-faint dwarf satellite galaxies. This discovery raises two major challenges to the merger model for heavy-element production:When neutron stars are born during a core-collapse supernova, mass is ejected, providing the stars with asymmetric natal kicks. During the second collapse in a double-neutron-star binary, wouldnt the kick exceed the low escape velocity of an ultra-faint dwarf, ejecting the binary before it could merge and enrich the galaxy?Ultra-faint dwarfs have very old stellar populations and the observation of r-process elements in these stars

  11. Status and prospects of investigations into the collinear cluster decay of heavy nuclei

    SciTech Connect

    Pyatkov, Yu. V.; Kamanin, D. V.; Alexandrov, A. A.; Alexandrova, I. A.; Mkaza, N.; Zhuchko, V. E.; Kondratyev, N. A.; Kuznetsova, E. A. Mishinsky, G. V.; Malaza, V.; Strekalovsky, A. O.; Strekalovsky, O. V.

    2014-12-15

    Basic experimental results confirming the existence a new cluster-decay type called collinear cluster tripartition (CCT) are presented. Decays of this type manifest themselves, in particular, as a two-dimensional region of a locally enhanced yield of fragments (bump) that corresponds to specific missing-mass values in the mass-mass distribution of fission fragments. One of the decay modes that contribute to the bump can be treated as a cluster-decay type that is new in relation to the well-known heavy-ion or lead radioactivity. The conclusions drawn from an analysis of correlation mass distributions are confirmed by the results obtained from neutron-gated data, measurements of the nuclear charge for CCT events, and the direct detection of new-decay products.

  12. Neutron capture and stellar synthesis of heavy elements.

    PubMed

    Gibbons, J H; Macklin, R L

    1967-05-26

    The neutron buildup processes of heavy-element synthesis in stars have left us a number of tantalizing nuclear clues to the early history of solarsystem material. Considerable illumination of our past history has been achieved through studying the correlations between abundance and neutroncapture cross section. Measurement of these cross sections required the development of new techniques for measuring time of flight of pulsed neutron beams. A clear conclusion is that many of our heavy elements were produced inside stars, which can be thought of as giant fast reactors. Extensions of these capture studies have given a clearer picture of additional. violent processes which produced some heavy elements, particularly thorium and uranium. In addition, the correlations have been used for obtaining an independent measure of the time that has elapsed since the solar-system material was synthesized. Finally, data on capture cross section relative to abundance will enable us to determine rather accurately the solar-system abundances of gaseous, volatile, and highly segregated elements. PMID:17774043

  13. The heavy element yields of neutron capture nucleosynthesis

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1982-01-01

    Consideration of the contribution made to the abundances of the heavy element isotopes by the S- and R-processes of nucleosynthesis has led to the determination that the previous assumption concerning the exclusive alignment of isobars to one or the other of these processes is probably in error. If the relatively small odd and even mass number abundance fluctuations characterizing R-process abundances are always the case, as assumed by this study, S-process contributions to the abundances of R-process isobars are substantial, consistent with transient flashing episodes in the S-process neutron production processes. A smooth and monotonically-decreasing curve of the abundance of the S-process yields times the neutron capture cross-section versus mass number is therefore the primary tool for the separation of the abundances due to the two processes.

  14. Atmosphere composition of quiescent accreting neutron stars in globular clusters

    NASA Astrophysics Data System (ADS)

    Servillat, M.

    2012-12-01

    Through the study of the quiescent X-ray emission of neutron stars in low-mass X-ray binaries it is possible to constrain the equation of state of dense matter. However, the chemical composition of the neutron star atmosphere is still uncertain. Using deep Chandra observations, we report the detailed spectral analysis of a neutron star in the globular cluster M28. For the first time for this kind of object, different atmosphere models composed of hydrogen, helium or carbon are used. The carbon model can be ruled out, and the derived mass and radius are clearly distinct depending on the composition of the atmosphere, leading to different constraints on the equation of state. We compare those results with the other similar neutron stars studied with a hydrogen atmosphere model only and show that a helium model could be relevant in many cases. Measurements of neutron star masses/radii by spectral fitting should consider the possibility of heavier element atmospheres, which produce larger masses/radii for the same data, unless the composition of the accretor is known independently.

  15. Heavy elements in globular clusters: The role of asymptotic giant branch stars

    SciTech Connect

    Straniero, O.; Cristallo, S.; Piersanti, L.

    2014-04-10

    Recent observations of heavy elements in globular clusters reveal intriguing deviations from the standard paradigm of the early galactic nucleosynthesis. If the r-process contamination is a common feature of halo stars, s-process enhancements are found in a few globular clusters only. We show that the combined pollution of asymptotic giant branch (AGB) stars with a mass ranging between 3 to 6 M {sub ☉} may account for most of the features of the s-process overabundance in M4 and M22. In these stars, the s process is a mixture of two very different neutron-capture nucleosynthesis episodes. The first is due to the {sup 13}C(α, n){sup 16}O reaction and takes place during the interpulse periods. The second is due to the {sup 22}Ne(α, n){sup 25}Mg reaction and takes place in the convective zones generated by thermal pulses. The production of the heaviest s elements (from Ba to Pb) requires the first neutron burst, while the second produces large overabundances of light s (Rb, Sr, Y, Zr). The first mainly operates in the less massive AGB stars, while the second dominates in the more massive. From the heavy-s/light-s ratio, we derive that the pollution phase should last for 150 ± 50 Myr, a period short enough compared to the formation timescale of the globular cluster system, but long enough to explain why the s-process pollution is observed in a few cases only. With few exceptions, our theoretical prediction provides a reasonable reproduction of the observed s-process abundances, from Sr to Hf. However, Ce is probably underproduced by our models, while Rb and Pb are overproduced. Possible solutions are discussed.

  16. 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.

  17. Spectroscopic factors and cluster decay half-lives of heavy nuclei

    SciTech Connect

    Kuklin, S.N.; Adamian, G.G.; Antonenko, N.V.

    2005-01-01

    The cluster radioactivity is treated under the assumption that the light clusters are produced by a collective motion of the nuclear system in the charge asymmetry coordinate with further penetration through the Coulomb barrier. The known experimental data on cluster radioactivity are described. The half-lives of cluster emission of neutron-deficient actinides and medium-mass nuclei are predicted.

  18. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in massive stars

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1981-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using a hydrodynamical model of a 15-solar mass (Type II) supernova and an n-process nuclear reaction network. It is found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material, especially in the vicinity of Pt, nor are any actinides produced. These deficiencies reflect an inadequate supply of neutrons. However, some neutron-rich isotopes, normally associated with the r-process, are produced which may be significant for the production of isotopic anomalies in meteorites.

  19. Efficient generation of fusion neutrons from cryogenically cooled heteronuclear clusters irradiated by intense femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Lu, Haiyang; Li, Song; Xu, Yi; Guo, Xiaoyang; Leng, Yuxin; Liu, Jiansheng; Shen, Baifei; Li, Ruxin; Xu, Zhizhan

    2014-02-01

    We present experimental studies on the conversion efficiency of fusion neutrons generated from Coulomb explosion of cryogenically cooled heteronuclear deuterated methane (CD4) clusters irradiated by intense femtosecond laser pulses. A stronger nonlinear relationship between the cluster size and the stagnation temperature for CD4 clusters than that for monoatomic or diatomic clusters is revealed, resulting in marked increases in the average kinetic energy of deuterons and the fusion neutron yield. Finally, a significantly enhanced conversion efficiency of 1.9 × 107 neutrons/J of incident laser energy is achieved by lowering the stagnation temperature to 217 K under a backing pressure of 80 bars.

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

    NASA Astrophysics Data System (ADS)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2000-10-01

    The Heavy Water Neutron Irradiation Facility (HWNIF) of the Kyoto University Research Reactor (KUR) was updated in March 1996, mainly for the improvement in neutron capture therapy (NCT). A striking feature of the updated facility is that the energy spectrum of the neutron beam can be controlled from almost pure thermal to epi-thermal, within 5 min by remote control under a continuous reactor operation. This feature is advantageous not only to medical science such as NCT, but also to the other research fields such as physics, engineering, biology, etc. The performance of the updated facility as a neutron irradiation field with variable energy spectra, was characterized. Thermal neutron flux, cadmium ratio, gamma-ray dose rate, etc., at the normal irradiation position for various irradiation modes were determined, mainly on the basis of the measurement using gold activation foils and thermo-luminescent dosimeters (TLDs). The emphasis was on the performance of the new neutron energy spectrum shifter and cadmium thermal neutron filter, that control the mixing ratio of thermal and epi-thermal neutrons, through the change in the heavy water thickness of the spectrum shifter and the aperture size of the cadmium filter. The evaluation of neutron energy spectra at the normal irradiation position was also performed for three representative irradiation modes, in which the neutron intensities are largest of all the irradiation modes. In addition, the irradiation characteristics of two irradiation devices, namely the Irradiation Rail Device and the Remote Patient Carrier, which were updated concurrently with the facility update, were evaluated.

  1. LETTER TO THE EDITOR: The halo structure of neutron-drip line nuclei: (neutron) cluster-core model

    NASA Astrophysics Data System (ADS)

    Gupta, Raj K.; Balasubramaniam, M.; Puri, Rajeev K.; Scheid, Werner

    2000-02-01

    Nuclei at the neutron-drip line are studied. In particular, we analyse the binding energies with the effects of Coulomb repulsion, nuclear attraction due to proximity and rotational energy due to angular momentum. This includes the study of the `neutron-halo structure' of some 18 light neutron-rich nuclei. In terms of the neutron-cluster + core picture, the halo structures of these nuclei are identified which agree with the hypothesis of one/two neutron separation energies and are supported by available experimental information. All the studied nuclei possess 1n- or 2n-halo structure. It is further shown that these nuclei prefer stable cores with not only the neutron number N = 2Z but also with 2Z +/-2.

  2. New prospects in synthesis and study of neutron rich heavy nuclei

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, W.

    2011-10-01

    The present limits of the upper part of the nuclear map are rather close to the beta stability line while the unexplored area of heavy neutron rich nuclides (also those located along the neutron closed shell N = 126 to the right hand side of the stability line) is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleogenesis. For elements with Z > 100 only neutron deficient isotopes (located to the left of the stability line) have been synthesized so far. The "north-east" area of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of new nuclei. Multi-nucleon transfer processes in near barrier collisions of heavy ions seem to be the only reaction mechanism allowing us to produce and explore neutron rich heavy nuclei including those located at the superheavy island of stability. Neutron capture process can be also considered as an alternative method for the production of long-lived neutron rich superheavy nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in laboratory frame and by supernova explosions in nature.

  3. Neutron-Capture Nucleosynthesis and the Chemical Evolution of Globular Clusters

    NASA Astrophysics Data System (ADS)

    Shingles, Luke J.

    2015-09-01

    Elements heavier than iron are almost entirely produced in stars through neutron captures and radioactive decays. Of these heavy elements, roughly half are produced by the slow neutron-capture process (s-process), which takes place under extended exposure to low neutron densities. Most of the s-process production occurs in stars with initial masses between roughly 0.8 and 8 solar masses (Msun), which evolve through the Asymptotic Giant Branch (AGB) phase. This thesis explores several topics related to AGB stars and the s-process, with a focus on comparing theoretical models to observations in the literature on planetary nebulae, post-AGB stars, and globular cluster stars. A recurring theme is the uncertainty of carbon-13-pocket formation, which is crucial for building accurate models of s-process nucleosynthesis. We first investigated whether neutron-capture reactions in AGB stars are the cause of the low sulphur abundances in planetary nebulae and post-AGB stars relative to the interstellar medium. Accounting for uncertainties in the size of the partial mixing zone that forms carbon-13 pockets and the rates of neutron-capture and neutron-producing reactions, our models failed to reproduce the observed levels of sulphur destruction. From this, we concluded that AGB nucleosynthesis is not the cause of the sulphur anomaly. We also discovered a new method to constrain the extent of the partial mixing zone using neon abundances in planetary nebulae. We next aimed to discover the stellar sites of the s-process enrichment in globular clusters that have inter- and intra-cluster variation, with the examples of M4 (relative to M5) and M22, respectively. Using a new chemical evolution code developed by the candidate, we tested models with stellar yields from rotating massive stars and AGB stars. We compared our model predictions for the production of s-process elements with abundances from s-poor and s-rich populations. We found that rotating massive stars alone do not

  4. Calibration of the neutron detectors for the cluster fusion experiment on the Texas Petawatt Laser

    SciTech Connect

    Bang, W.; Quevedo, H. J.; Dyer, G.; Rougk, J.; Kim, I.; McCormick, M.; Bernstein, A. C.; Ditmire, T.

    2012-06-15

    Three types of neutron detectors (plastic scintillation detectors, indium activation detectors, and CR-39 track detectors) were calibrated for the measurement of 2.45 MeV DD fusion neutron yields from the deuterium cluster fusion experiment on the Texas Petawatt Laser. A Cf-252 neutron source and 2.45 MeV fusion neutrons generated from laser-cluster interaction were used as neutron sources. The scintillation detectors were calibrated such that they can detect up to 10{sup 8} DD fusion neutrons per shot in current mode under high electromagnetic pulse environments. Indium activation detectors successfully measured neutron yields as low as 10{sup 4} per shot and up to 10{sup 11} neutrons. The use of a Cf-252 neutron source allowed cross calibration of CR-39 and indium activation detectors at high neutron yields ({approx}10{sup 11}). The CR-39 detectors provided consistent measurements of the total neutron yield of Cf-252 when a modified detection efficiency of 4.6 Multiplication-Sign 10{sup -4} was used. The combined use of all three detectors allowed for a detection range of 10{sup 4} to 10{sup 11} neutrons per shot.

  5. Neutron attenuation characteristics of polyethylene, polyvinyl chloride, and heavy aggregate concrete and mortars

    SciTech Connect

    Abdul-Majid, S.; Othman, F.

    1994-03-01

    Polyethylene and polyvinyl chloride pellets were introduced into concrete to improve its neutron attenuation characteristics while several types of heavy coarse aggregates were used to improve its gamma ray attenuation properties. Neutron and gamma ray attenuation were studied in concrete samples containing coarse aggregates of barite, pyrite, basalt, hematite, and marble as well as polyethylene and polyvinyl chloride pellets in narrow-beam geometry. The highest neutron attenuation was shown by polyethylene mortar, followed by polyvinyl chloride mortar; barite and pyrite concrete showed higher gamma ray attenuation than ordinary concrete. Broad-beam and continuous (infinite) medium geometries were used to study the neutron attenuation of samples containing polymers at different concentrations with and without heavy aggregates, the fitting equations were established, and from these the neutron removal coefficients were deduced. In a radiation field of neutrons and gamma rays, the appropriate concentration of polymer and heavy aggregate can be selected to give the optimum total dose attenuation depending on the relative intensities of each type of radiation. This would give much better design flexibility over ordinary concrete. The compressive strength tests performed on mortar and concrete samples showed that their value, in general, decreases as polymer concentration increases and that the polyvinyl chloride mortar showed higher values than the polyethylene mortar. For general construction purposes, the compression strength was considered acceptable in these samples. 34 refs., 16 figs., 4 tabs.

  6. Neutron attenuation characteristics of polyethylene, polyvinyl chloride, and heavy aggregate concrete and mortars.

    PubMed

    Abdul-Majid, S; Othman, F

    1994-03-01

    Polyethylene and polyvinyl chloride pellets were introduced into concrete to improve its neutron attenuation characteristics while several types of heavy coarse aggregates were used to improve its gamma ray attenuation properties. Neutron and gamma ray attenuation were studied in concrete samples containing coarse aggregates of barite, pyrite, basalt, hematite, and marble as well as polyethylene and polyvinyl chloride pellets in narrow-beam geometry. The highest neutron attenuation was shown by polyethylene mortar, followed by polyvinyl chloride mortar; barite and pyrite concrete showed higher gamma ray attenuation than ordinary concrete. Broad-beam and continuous (infinite) medium geometries were used to study the neutron attenuation of samples containing polymers at different concentrations with and without heavy aggregates, the fitting equations were established, and from these the neutron removal coefficients were deduced. In a radiation field of neutrons and gamma rays, the appropriate concentration of polymer and heavy aggregate can be selected to give the optimum total dose attenuation depending on the relative intensities of each type of radiation. This would give much better design flexibility over ordinary concrete. The compressive strength tests performed on mortar and concrete samples showed that their value, in general, decreases as polymer concentration increases and that the polyvinyl chloride mortar showed higher values than the polyethylene mortar. For general construction purposes, the compression strength was considered acceptable in these samples.

  7. Heavy and Superheavy Elements Production in High Intensive Neutron Fluxes of Explosive Process

    NASA Astrophysics Data System (ADS)

    Lutostansky, Yu. S.; Lyashuk, V. I.; Panov, I. V.

    2015-06-01

    Mathematical model of heavy and superheavy nuclei production in intensive pulsed neutron fluxes of explosive process is developed. The pulse character of the process allows dividing it in time into two stages: very short rapid process of multiple neutron captures with higher temperature and very intensive neutron fluxes, and relatively slower process with lesser temperature and neutron fluxes. The model was also extended for calculation of the transuranium yields in nuclear explosions takes into account the adiabatic character of the process, the probabilities of delayed fission, and the emission of delayed neutrons. Also the binary starting target isotopes compositions were included. Calculations of heavy transuranium and transfermium nuclei production were made for "Mike", "Par" and "Barbel" experiments, performed in USA. It is shown that the production of transfermium neutron-rich nuclei and superheavy elements with A ~ 295 is only possible when using binary mixture of starting isotopes with the significant addition of heavy components, such as long-lived isotopes of curium, or californium.

  8. Flux dependence of cluster formation in neutron-irradiated weld material

    NASA Astrophysics Data System (ADS)

    Bergner, F.; Ulbricht, A.; Hein, H.; Kammel, M.

    2008-03-01

    The effect of neutron flux on the formation of irradiation-induced clusters in reactor pressure vessel (RPV) steels is an unresolved issue. Small-angle neutron scattering was measured for a neutron-irradiated RPV weld material containing 0.22 wt% impurity Cu. The experiment was focused on the influence of neutron flux on the formation of irradiation-induced clusters at fixed fluence. The aim was to separate and tentatively interpret the effect of flux on the characteristics of the cluster size distribution. We have observed a pronounced effect of neutron flux on cluster size, whereas the total volume fraction of irradiation-induced clusters is insensitive to the level of flux. The result is compatible with a rate theory model according to which the range of applied fluxes covers the transition from a flux-independent regime at lower fluxes to a regime of decelerating cluster growth. The results are confronted with measured irradiation-induced changes of mechanical properties. Despite the observed flux effect on cluster size, both yield stress increase and transition temperature shift turned out to be independent of flux. This is in agreement with the volume fraction of irradiation-induced clusters being insensitive to the level of flux.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  10. A high repetition rate laser-heavy water based neutron source

    NASA Astrophysics Data System (ADS)

    Hah, Jungmoo; He, Zhaohan; Nees, John; Krushelnick, Karl; Thomas, Alexander; CenterUltrafast Optical Science Team

    2015-11-01

    Neutrons have numerous applications in diverse areas, such as medicine, security, and material science. For example, sources of MeV neutrons may be used for active interrogation for nuclear security applications. Recently, alternative ways to generate neutron flux have been studied. Among them, ultrashort laser pulse interactions with dense plasma have attracted significant attention as compact, pulse sources of neutrons. To generate neutrons using a laser through fusion reactions, thin solid density targets have been used in a pitcher-catcher arrangement, using deuterated plastic for example. However, the use of solid targets is limited for high-repetition rate operation due to the need to refresh the target for every laser shot. Here, we use a free flowing heavy water target with a high repetition rate (500 Hz) laser without a catcher. From the interaction between a 10 micron scale diameter heavy water stream with the Lambda-cubed laser system at the Univ. of Michigan (12mJ, 800nm, 35fs), deuterons collide with each other resulting in D-D fusion reactions generating 2.45 MeV neutrons. Under best conditions a time average of ~ 105 n/s of neutrons are generated.

  11. Controllability of depth dose distribution for neutron capture therapy at the Heavy Water Neutron Irradiation Facility of Kyoto University Research Reactor.

    PubMed

    Sakurai, Yoshinori; Kobayashi, Tooru

    2002-10-01

    The updating construction of the Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor has been performed from November 1995 to March 1996 mainly for the improvement in neutron capture therapy. On the performance, the neutron irradiation modes with the variable energy spectra from almost pure thermal to epi-thermal neutrons became available by the control of the heavy-water thickness in the spectrum shifter and by the open-and-close of the cadmium and boral thermal neutron filters. The depth distributions of thermal, epi-thermal and fast neutron fluxes were measured by activation method using gold and indium, and the depth distributions of gamma-ray absorbed dose rate were measured using thermo-luminescent dosimeter of beryllium oxide for the several irradiation modes. From these measured data, the controllability of the depth dose distribution using the spectrum shifter and the thermal neutron filters was confirmed.

  12. Leap to explore the region of neutron-rich heavy element isotopes

    SciTech Connect

    Hoffman, D.C.

    1985-10-01

    The research aims of the Large Einsteinium Activation Program (LEAP) are described. This program is a major initiative to exploit currently existing expertise in heavy element research and the potential for producing very heavy actinide target materials such as 285-day /sup 254/Es at the High Flux Isotope Reactor at Oak Ridge National Laboratory. The stated aims of the program are to produce heavy element isotopes, to conduct chemical studies of these isotopes, to study the nuclear properties of such isotopes, and to produce a superheavy element (183 neutrons) by the using a /sup 254/Es target and /sup 48/Ca projectiles. 13 refs., 2 figs., 2 tabs. (DWL)

  13. New insights on Ba overabundance in open clusters. Evidence for the intermediate neutron-capture process at play?

    NASA Astrophysics Data System (ADS)

    Mishenina, T.; Pignatari, M.; Carraro, G.; Kovtyukh, V.; Monaco, L.; Korotin, S.; Shereta, E.; Yegorova, I.; Herwig, F.

    2015-02-01

    Recently, an increasing number of studies were devoted to measure the abundances of neutron-capture elements heavier than iron in stars belonging to Galactic Open Clusters (OCs). OCs span a sizeable range in metallicity (-0.6 ≤ [Fe/H] ≤ +0.4), and they show abundances of light elements similar to disc stars of the same age. A different pattern is observed for heavy elements. A large scatter is observed for Ba, with most OCs showing [Ba/Fe] and [Ba/La] overabundant with respect to the Sun. The origin of this overabundance is not clearly understood. With the goal of providing new observational insights, we determined radial velocities, atmospheric parameters and chemical composition of 27 giant stars members of five OCs: Cr 110, Cr 261, NGC 2477, NGC 2506 and NGC 5822. We used high-resolution spectra obtained with the UVES spectrograph at European Southern Observatory Paranal. We perform a detailed spectroscopic analysis of these stars to measure the abundance of up to 22 elements per star. We study the dependence of element abundance on metallicity and age with unprecedented detail, complementing our analysis with data culled from the literature. We confirm the trend of Ba overabundance in OCs, and show its large dispersion for clusters younger than ˜4 Gyr. Finally, the implications of our results for stellar nucleosynthesis are discussed. We show in this work that the Ba enrichment compared to other neutron-capture elements in OCs cannot be explained by the contributions from the slow neutron-capture process and the rapid neutron-capture process. Instead, we argue that this anomalous signature can be explained by assuming an additional contribution by the intermediate neutron-capture process.

  14. Neutron Production from In-situ Heavy Ice Coated Targets at Vulcan

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Laser based neutron production experiments have been performed utilizing ultra-high intensity laser accelerated ions impinging upon a secondary target. The neutron yield from such experiments may be improved if the accelerated ions were primarily deuterons taking advantage of the d-d cross section. Recent experiments have demonstrated that selective deuteron acceleration from in-situ heavy ice coating of targets can produce ion spectra where deuterons comprise > 99 % of the measured ions. Results will be presented from integrated neutron production experiments from heavy ice targets coated in-situ recently performed on the Vulcan laser at Rutherford Appleton Laboratory. We are grateful for the Staff at RAL and acknowledge funding from the US DoE. AFOSR, European Social Fund, and the Czech Republic.

  15. Calculation of dose contributions of electron and charged heavy particles inside phantoms irradiated by monoenergetic neutron.

    PubMed

    Satoh, Daiki; Takahashi, Fumiaki; Endo, Akira; Ohmachi, Yasushi; Miyahara, Nobuyuki

    2008-09-01

    The radiation-transport code PHITS with an event generator mode has been applied to analyze energy depositions of electrons and charged heavy particles in two spherical phantoms and a voxel-based mouse phantom upon neutron irradiation. The calculations using the spherical phantoms quantitatively clarified the type and energy of charged particles which are released through interactions of neutrons with the phantom elements and contribute to the radiation dose. The relative contribution of electrons increased with an increase in the size of the phantom and with a decrease in the energy of the incident neutrons. Calculations with the voxel-based mouse phantom for 2.0-MeV neutron irradiation revealed that the doses to different locations inside the body are uniform, and that the energy is mainly deposited by recoil protons. The present study has demonstrated that analysis using PHITS can yield dose distributions that are accurate enough for RBE evaluation. PMID:18580044

  16. 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.

  17. Laser desorption mass spectrometry and small angle neutron scattering of heavy fossil materials

    SciTech Connect

    Hunt, J.E.; Winans, R.E.; Thiyagarajan, P.

    1997-09-01

    The determination of the structural building blocks and the molecular weight range of heavy hydrocarbon materials is of crucial importance in research on their reactivity and for their processing. The chemically and physically heterogenous nature of heavy hydrocarbon materials, such as coals, heavy petroleum fractions, and residues, dictates that their structure and reactivity patterns be complicated. The problem is further complicated by the fact that the molecular structure and molecular weight distribution of these materials is not dependent on a single molecule, but on a complex mixture of molecules which vary among coals and heavy petroleum samples. Laser Desorption mass spectrometry (LDMS) is emerging as a technique for molecular weight determination having found widespread use in biological polymer research, but is still a relatively new technique in the fossil fuel area. Small angle neutron scattering (SANS) provides information on the size and shape of heavy fossil materials. SANS offers the advantages of high penetration power even in thick cells at high temperatures and high contrast for hydrocarbon systems dispersed in deuterated solvents. LDMS coupled with time of flight has the advantages of high sensitivity and transmission and high mass range. We have used LDMS to examine various heavy fossil-derived materials including: long chain hydrocarbons, asphaltenes from petroleum vacuum resids, and coals. This paper describes the application of laser desorption and small angle neutron scattering techniques to the analysis of components in coals, petroleum resids and unsaturated polymers.

  18. Single-particle selection and alignment with heavy atom cluster-antibody conjugates.

    PubMed

    Jensen, G J; Kornberg, R D

    1998-08-01

    A method is proposed for selecting and aligning images of single biological particles to obtain high-resolution structural information by cryoelectron microscopy. The particles will be labeled with multiple heavy atom clusters to permit the precise determination of particle locations and relative orientations even when imaged close to focus with a low electron dose, conditions optimal for recording high-resolution detail. Heavy atom clusters should also allow selection of images free from many kinds of defects, including specimen movement and particle inhomogeneity. Heavy atom clusters may be introduced in a general way by the construction of "adaptor" molecules based on single-chain Fv antibody fragments, consisting of a constant framework region engineered for optimal cluster binding and a variable antigen binding region selected for a specific target. The success of the method depends on the mobility of the heavy atom cluster on the particle, on the precision to which clusters can be located in an image, and on the sufficiency of cluster projections alone to orient and select particles for averaging. The necessary computational algorithms were developed and implemented in simulations that address the feasibility of the method.

  19. Symmetries in heavy nuclei and the proton-neutron interaction

    SciTech Connect

    Casten, R.F.

    1986-01-01

    The Interacting Boson Approximation (IBA) nuclear structure model can be expressed in terms of the U(6) group, and thereby leads to three dynamical symmetries (or group chains) corresponding to different nuclear coupling schemes and geometrical shapes. The status of the empirical evidence for these three symmetries is reviewed, along with brief comments on the possible existence of supersymmetries in nuclei. The relationships between these symmetries, the nuclear phase transitional regions linking them, and the residual proton-neutron interaction are discussed in terms of a particularly simple scheme for parameterizing the effects of that interaction. 34 refs., 15 figs.

  20. Cosmological quantum chromodynamics, neutron diffusion, and the production of primordial heavy elements

    NASA Technical Reports Server (NTRS)

    Applegate, J. H.; Hogan, Craig J.; Scherrer, R. J.

    1988-01-01

    A simple one-dimensional model is used to describe the evolution of neutron density before and during nucleosynthesis in a high-entropy bubble left over from the cosmic quark-hadron phase transition. It is shown why cosmic nucleosynthesis in such a neutron-rich environment produces a surfeit of elements heavier than lithium. Analytical and numerical techniques are used to estimate the abundances of carbon, nitrogen, and heavier elements up to Ne-22. A high-density neutron-rich region produces enough primordial N-14 to be observed in stellar atmospheres. It shown that very heavy elements may be created in a cosmological r-process; the neutron exposure in the neutron-rich regions is large enough for the Ne-22 to trigger a catastrophic r-process runaway in which the quantity of heavy elements doubles in much less than an expansion time due to fission cycling. A primordial abundance of r-process elements is predicted to appear as an excess of rare earth elements in extremely metal-poor stars.

  1. Constraining Properties of Rapidly Rotating Neutron Stars Using Data from Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Krastev, Plamen G.; Li, Bao-An; Worley, Aaron

    2008-04-01

    Properties, structure, and thermal evolution of neutron stars are determined by the equation of state of stellar matter. Recent data on isospin diffusion and isoscaling in heavy-ion collisions at intermediate energies as well as data on the size of the neutron skin in 208Pb have considerably constrained the density dependence of the nuclear symmetry energy and, in turn, the equation of state of neutron-rich nucleonic matter. These constraints could provide useful information about the global properties of rapidly rotating neutron stars. Models of rapidly rotating neutron stars are constructed by applying several nucleonic equations of state. Particular emphasis is placed on configurations rotating rigidly at 716 and 1122 Hz. The range of allowed hydrostatic equilibrium solutions is determined and tested for stability. The effect of rotation on the internal composition and thermal properties of neutron stars is also examined. At a given rotational frequency, each equation of state yields a range of possible neutron stars configurations restricted by the Keplerian (mass-shedding) limit, corresponding to the maximal circumferential radius, and the limit due to the onset of instabilities with respect to axisymmetric perturbations, corresponding to the minimal equatorial radius of a stable neutron star model. We show that the mass of a neutron star rotating uniformly at 1122 Hz is between 1.7 and 2.1 M⊙. Central stellar density and proton fraction decrease with increasing rotational frequency with respect to static models and, depending on the exact stellar mass and angular velocity, can drop below the direct Urca threshold, thus closing the fast cooling channel.

  2. Model of defect reactions and the influence of clustering in pulse-neutron-irradiated Si

    SciTech Connect

    Myers, S. M.; Cooper, P. J.; Wampler, W. R.

    2008-08-15

    Transient reactions among irradiation defects, dopants, impurities, and carriers in pulse-neutron-irradiated Si were modeled taking into account the clustering of the primal defects in recoil cascades. Continuum equations describing the diffusion, field drift, and reactions of relevant species were numerically solved for a submicrometer spherical volume, within which the starting radial distributions of defects could be varied in accord with the degree of clustering. The radial profiles corresponding to neutron irradiation were chosen through pair-correlation-function analysis of vacancy and interstitial distributions obtained from the binary-collision code MARLOWE, using a spectrum of primary recoil energies computed for a fast-burst fission reactor. Model predictions of transient behavior were compared with a variety of experimental results from irradiated bulk Si, solar cells, and bipolar-junction transistors. The influence of defect clustering during neutron bombardment was further distinguished through contrast with electron irradiation, where the primal point defects are more uniformly dispersed.

  3. Angular distribution of neutrons from deuterated cluster explosions driven by femtosecond laser pulses.

    PubMed

    Buersgens, F; Madison, K W; Symes, D R; Hartke, R; Osterhoff, J; Grigsby, W; Dyer, G; Ditmire, T

    2006-07-01

    We have studied experimentally the angular distributions of fusion neutrons from plasmas of multi-keV ion temperature, created by 40 fs, multi-TW laser pulses in dense plumes of D2 and CD4 clusters. A slight anisotropy in the neutron emission is observed. We attribute this anisotropy to the fact that the differential cross section for DD fusion is anisotropic even at low collision energies, and this, coupled with the geometry of the gas jet target, leads to beam-target neutrons that are slightly directed. The qualitative features of this anisotropy are confirmed by Monte Carlo simulations.

  4. Angular distribution of neutrons from deuterated cluster explosions driven by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Buersgens, F.; Madison, K. W.; Symes, D. R.; Hartke, R.; Osterhoff, J.; Grigsby, W.; Dyer, G.; Ditmire, T.

    2006-07-01

    We have studied experimentally the angular distributions of fusion neutrons from plasmas of multi-keV ion temperature, created by 40fs , multi-TW laser pulses in dense plumes of D2 and CD4 clusters. A slight anisotropy in the neutron emission is observed. We attribute this anisotropy to the fact that the differential cross section for DD fusion is anisotropic even at low collision energies, and this, coupled with the geometry of the gas jet target, leads to beam-target neutrons that are slightly directed. The qualitative features of this anisotropy are confirmed by Monte Carlo simulations.

  5. Collinear Cluster Tripartition as a Neutron Source--Evaluation of the Setup Parameters

    SciTech Connect

    Kamanin, D. V.; Kuznetsova, E. A.; Aleksandrov, A. A.; Aleksandrova, I. A.; Borzakov, S. B.; Chelnokov, M. L.; Pham Minh, D.; Kondratyev, N. A.; Kopach, Yu. N.; Panteleev, Ts.; Penionzhkevich, Yu. E.; Svirikhin, A. I.; Sokol, E. A.; Testov, D. A.; Zhuchko, V. E.; Yeremin, A. V.; Pyatkov, Yu. V.; Jacobs, N.; Ryabov, Yu. V.

    2010-04-30

    Forthcoming experiments aimed at studying the mechanism of collinear cluster tripartition are planning to be performed with the new facility. Charged products will be registered with the double arm time-of-flight spectrometer composed of mosaics of PIN -diodes and MCP (micro channel plates) based timing detectors. Several tens of {sup 3}He-filled counters will be gathered round the {sup 252}Cf source. In order to choose an optimal configuration of the neutron detector and other parameters of the experiment special modeling has performed using both 'neutron barrel' and known MCNP code. The first test run of the new facility is in progress also its 'neutron skin' in under construction.

  6. Nucleosynthesis of neutron-rich heavy nuclei during explosive helium burning in a 15 solar-mass supernova

    NASA Technical Reports Server (NTRS)

    Blake, J. B.; Woosley, S. E.; Weaver, T. A.; Schramm, D. N.

    1980-01-01

    The production of heavy nuclei during explosive helium burning has been calculated using the Weaver and Woosley self-consistent model of a complete 15 solar-mass star and the n-process code of Blake and Schramm. It was found that the resulting neutron-rich heavy nuclei are not produced in the relative abundances of solar-system r-process material (such as a Pt peak) nor are any actinides produced. Basically insufficient neutrons are available.

  7. Production of heavy and superheavy neutron-rich nuclei in neutron capture processes

    NASA Astrophysics Data System (ADS)

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, Walter

    2011-10-01

    The neutron capture process is considered as an alternative method for production of superheavy (SH) nuclei. Strong neutron fluxes might be provided by nuclear reactors and nuclear explosions in the laboratory frame and by supernova explosions in nature. All these cases are discussed in the paper. There are two gaps of short-lived nuclei (one is the well-known fermium gap and the other one is located in the region of Z=106-108 and N˜170) which impede the formation of SH nuclei by rather weak neutron fluxes realized at available nuclear reactors. We find that in the course of multiple (rather “soft”) nuclear explosions these gaps may be easily bypassed, and thus, a measurable amount of the neutron-rich long-living SH nuclei located at the island of stability may be synthesized. Existing pulsed reactors do not allow one to bypass these gaps. We formulate requirements for the pulsed reactors of the next generation that could be used for production of long-living SH nuclei. Natural formation of SH nuclei (in supernova explosions) is also discussed. The yield of SH nuclei relative to lead is estimated to be about 10-12, which is not beyond the experimental sensitivity for a search of SH elements in cosmic rays.

  8. Neutron star natal kicks and the long-term survival of star clusters

    NASA Astrophysics Data System (ADS)

    Contenta, Filippo; Varri, Anna Lisa; Heggie, Douglas C.

    2015-04-01

    We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks. We show that, even if neutron stars typically represent less than 2 per cent of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of 4. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass-loss or two-body relaxation. The competition between these effects shapes the mass-loss profile of star clusters, which may either dissolve abruptly (`jumping'), in the pre-core-collapse phase, or gradually (`skiing'), after having reached core collapse.

  9. Neutron Capture Elements in the Open Cluster Chemical Abundance & Mapping (OCCAM) Survey

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Hearty, Fred R.; Majewski, Steven R.; Zasowski, Gail; Sdss /Apogee-1, III

    2015-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. The high-resolution (R=22,500), near-infrared (H-band) APOGEE-1 survey allows for cluster membership probability determination and analysis of light and iron-peak elements. Neutron capture elements, however, prove to be elusive in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we conducted a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. We present results based on prominent resonance lines for Eu, La, Ba, and Ce in the ~5400-6750 AA range using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph.

  10. Di-Neutron Clustering and Deuteron-like Tensor Correlation in Nuclear Structure Focusing on 11Li

    NASA Astrophysics Data System (ADS)

    Ikeda, Kiyomi; Myo, Takayuki; Kato, Kiyoshi; Toki, Hiroshi

    11Li is a Borromean nucleus, where two out of three objects as 9Li + n and two neutrons independently do not form bound systems. Two neutrons should form a di-neutron cluster in the nuclear field generated by the 9Li core nucleus. We treat di-neutron clustering by solving the two neutron relative wave function precisely by using the bare nucleon-nucleon interaction so that the spatial clustering structure is obtained quantitatively within the whole 11Li nucleus. This di-neutron clustering is an essential dynamics to form the halo structure by making a compact di-neutron cluster, which distributes loosely around the 9Li core. This concept of di-neutron clustering should be clearly distinguished from the BCS pairing correlation, where no consideration of spatial clustering is made. The di-neutron clustering is a new concept and is a general phenomenon in neutron skin and neutron halo nuclei. This quantitative description of di-neutron clustering has made it necessary to consider another important deuteron-like tensor correlation, which is caused by strong tensor interaction in the nucleon-nucleon interaction. The tensor interaction originates from pion exchange and known to provide large attraction to form the 4He nucleus. The unique feature of the tensor correlation is to make highly correlated deuteron-like excitation, which interferes with shell model like structure in a unique way. This dynamical effect removes the magic number effect and makes easy the participation of the s-wave neutrons. Hence, there are pairing and deuteron-like tensor correlations in addition to the mean field structure in 9Li. The combined system of two additional neutrons with the correlated 9Li provides the halo phenomenon, in which the di-neutron clustering develops with the help of large s-wave component caused by the deuteron-like tensor correlation. These two effects, the di-neutron clustering and the deuteron-like tensor correlation, are quite new and essential to provide the halo

  11. 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.

  12. Secondary neutron-production cross sections from heavy-ioninteractions in composite targets.

    SciTech Connect

    Heilbronn, L.; Iwata, Y.; Iwase,H.; Murakami, T.; Sato, H.; Nakamura, T.; Ronningen, R.M.; Ieki, K.; Gudowska, I.; Sobolevsky, N.

    2005-12-19

    Secondary neutron-production cross-sections have been measured from interactions of 290 MeV/nucleon C and 600 MeV/nucleon Ne in a target composed of simulated Martian regolith and polyethylene, and from 400 MeV/nucleon Ne interactions in wall material from the International Space Station. The data were measured between 5 and 80 deg in the laboratory. We report the double-differential cross sections, angular distributions, and total neutron-production cross sections from all three systems. The spectra from all three systems exhibit behavior previously reported in other heavy-ion, neutron production experiments; namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by pre-equilibrium and equilibrium processes. The double differential cross sections are fitted with a moving-source parameterization. Also reported are the data without corrections for neutron flux attenuation in the target and other intervening materials, and for neutron production in non-target materials near the target position. These uncorrected spectra are compared with SHIELD-HIT and PHITS transport model calculations. The transport model calculations reproduce the spectral shapes well, but, on average, underestimate the magnitudes of the cross sections.

  13. Localization and orientation of heavy-atom cluster compounds in protein crystals using molecular replacement

    PubMed Central

    Dahms, Sven O.; Kuester, Miriam; Streb, Carsten; Roth, Christian; Sträter, Norbert; Than, Manuel E.

    2013-01-01

    Heavy-atom clusters (HA clusters) containing a large number of specifically arranged electron-dense scatterers are especially useful for experimental phase determination of large complex structures, weakly diffracting crystals or structures with large unit cells. Often, the determination of the exact orientation of the HA cluster and hence of the individual heavy-atom positions proves to be the critical step in successful phasing and subsequent structure solution. Here, it is demonstrated that molecular replacement (MR) with either anomalous or isomorphous differences is a useful strategy for the correct placement of HA cluster compounds. The polyoxometallate cluster hexasodium α-metatungstate (HMT) was applied in phasing the structure of death receptor 6. Even though the HA cluster is bound in alternate partially occupied orientations and is located at a special position, its correct localization and orientation could be determined at resolutions as low as 4.9 Å. The broad applicability of this approach was demonstrated for five different derivative crystals that included the compounds tantalum tetradeca­bromide and trisodium phosphotungstate in addition to HMT. The correct placement of the HA cluster depends on the length of the intramolecular vectors chosen for MR, such that both a larger cluster size and the optimal choice of the wavelength used for anomalous data collection strongly affect the outcome. PMID:23385464

  14. Method of using deuterium-cluster foils for an intense pulsed neutron source

    DOEpatents

    Miley, George H.; Yang, Xiaoling

    2013-09-03

    A method is provided for producing neutrons, comprising: providing a converter foil comprising deuterium clusters; focusing a laser on the foil with power and energy sufficient to cause deuteron ions to separate from the foil; and striking a surface of a target with the deuteron ions from the converter foil with energy sufficient to cause neutron production by a reaction selected from the group consisting of D-D fusion, D-T fusion, D-metal nuclear spallation, and p-metal. A further method is provided for assembling a plurality of target assemblies for a target injector to be used in the previously mentioned manner. A further method is provided for producing neutrons, comprising: splitting a laser beam into a first beam and a second beam; striking a first surface of a target with the first beam, and an opposite second surface of the target with the second beam with energy sufficient to cause neutron production.

  15. Cluster-transfer reactions with radioactive beams: A spectroscopic tool for neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Bottoni, S.; Leoni, S.; Fornal, B.; Raabe, R.; Rusek, K.; Benzoni, G.; Bracco, A.; Crespi, F. C. L.; Morales, A. I.; Bednarczyk, P.; Cieplicka-Oryńczak, N.; Królas, W.; Maj, A.; Szpak, B.; Callens, M.; Bouma, J.; Elseviers, J.; De Witte, H.; Flavigny, F.; Orlandi, R.; Reiter, P.; Seidlitz, M.; Warr, N.; Siebeck, B.; Hellgartner, S.; Mücher, D.; Pakarinen, J.; Vermeulen, M.; Bauer, C.; Georgiev, G.; Janssens, R. V. F.; Balabanski, D.; Sferrazza, M.; Kowalska, M.; Rapisarda, E.; Voulot, D.; Lozano Benito, M.; Wenander, F.

    2015-08-01

    An exploratory experiment performed at REX-ISOLDE to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier as a mechanism to explore the structure of exotic neutron-rich nuclei. The reactions 7Li(98Rb,α xn ) and 7Li(98Rb,t xn ) were studied through particle-γ coincidence measurements, and the results are presented in terms of the observed excitation energies and spins. Moreover, the reaction mechanism is qualitatively discussed as a transfer of a clusterlike particle within a distorted-wave Born approximation framework. The results indicate that cluster-transfer reactions can be described well as a direct process and that they can be an efficient method to investigate the structure of neutron-rich nuclei at medium-high excitation energies and spins.

  16. Stellar encounters involving neutron stars in globular cluster cores

    NASA Technical Reports Server (NTRS)

    Davies, M. B.; Benz, W.; Hills, J. G.

    1992-01-01

    Encounters between a 1.4 solar mass neutron star and a 0.8 solar mass red giant (RG) and between a 1.4 solar mass neutron star (NS) and an 0.8 solar mass main-sequence (MS) star have been successfully simulated. In the case of encounters involving an RG, bound systems are produced when the separation at periastron passage R(MIN) is less than about 2.5 R(RG). At least 70 percent of these bound systems are composed of the RG core and NS forming a binary engulfed in a common envelope of what remains of the former RG envelope. Once the envelope is ejected, a tight white dwarf-NS binary remains. For MS stars, encounters with NSs will produce bound systems when R(MIN) is less than about 3.5 R(MS). Some 50 percent of these systems will be single objects with the NS engulfed in a thick disk of gas almost as massive as the original MS star. The ultimate fate of such systems is unclear.

  17. New Neutron-capture Measurements in 23 Open Clusters. I. The r-Process

    NASA Astrophysics Data System (ADS)

    Overbeek, Jamie C.; Friel, Eileen D.; Jacobson, Heather R.

    2016-06-01

    Neutron-capture elements, those with Z > 35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r-process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s-process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with cluster age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3-10) lines for each element. We find that the pure r-process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r- and s-process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ˜0.04 dex kpc-1. The mixed elements also appear to have nonlinear relationships with R GC.

  18. New Neutron-capture Measurements in 23 Open Clusters. I. The r-Process

    NASA Astrophysics Data System (ADS)

    Overbeek, Jamie C.; Friel, Eileen D.; Jacobson, Heather R.

    2016-06-01

    Neutron-capture elements, those with Z > 35, are the least well understood in terms of nucleosynthesis and formation environments. The rapid neutron-capture, or r-process, elements are formed in the environments and/or remnants of massive stars, while the slow neutron-capture, or s-process, elements are primarily formed in low-mass AGB stars. These elements can provide much information about Galactic star formation and enrichment, but observational data are limited. We have assembled a sample of 68 stars in 23 open clusters that we use to probe abundance trends for six neutron-capture elements (Eu, Gd, Dy, Mo, Pr, and Nd) with cluster age and location in the disk of the Galaxy. In order to keep our analysis as homogeneous as possible, we use an automated synthesis fitting program, which also enables us to measure multiple (3–10) lines for each element. We find that the pure r-process elements (Eu, Gd, and Dy) have positive trends with increasing cluster age, while the mixed r- and s-process elements (Mo, Pr, and Nd) have insignificant trends consistent with zero. Pr, Nd, Eu, Gd, and Dy have similar, slight (although mostly statistically significant) gradients of ˜0.04 dex kpc‑1. The mixed elements also appear to have nonlinear relationships with R GC.

  19. Clustering of water molecules in ultramicroporous carbon: In-situ small-angle neutron scattering

    DOE PAGES

    Bahadur, Jitendra; Contescu, Cristian I.; Rai, Durgesh K.; Gallego, Nidia C.; Melnichenko, Yuri B.

    2016-10-19

    The adsorption of water is central to most of the applications of microporous carbon as adsorbent material. We report early kinetics of water adsorption in the microporous carbon using in-situ small-angle neutron scattering. It is observed that adsorption of water occurs via cluster formation of molecules. Interestingly, the cluster size remains constant throughout the adsorption process whereas number density of clusters increases with time. The role of surface chemistry of microporous carbon on the early kinetics of adsorption process was also investigated. Lastly, the present study provides direct experimental evidence for cluster assisted adsorption of water molecules in microporous carbonmore » (Do-Do model).« less

  20. Temperature dependence of clusters with attracting vortices in superconducting niobium studied by neutron scattering.

    PubMed

    Pautrat, A; Brûlet, A

    2014-06-11

    We investigated the intermediate mixed state of a superconducting niobium sample using very small angle neutron scattering. We show that this state is stabilized through a sequence where a regular vortex lattice appears, which then coexists with vortex clusters before vanishing at low temperature. Vortices in clusters have a constant periodicity regardless of the applied field and exhibit a temperature dependence close to the one of the penetration depth. The clusters disappear in the high temperature limit. All the results agree with an explanation in terms of vortex attraction due to non-local effects and indicate a negligible role for pinning. Phase coexistence between the Abrikosov vortex lattice and vortex clusters is reported, showing the first-order nature of the boundary line.

  1. Open Cluster Neutron Capture Element Abundances and Milky Way Disk Evolution

    NASA Astrophysics Data System (ADS)

    Jacobson, Heather R.; Friel, E. D.

    2012-01-01

    Open clusters, whose ages and distances can be precisely determined, are useful probes of the chemical evolution of the Milky Way disk. The sample sizes of clusters subject to homogeneous analysis of high resolution spectra have grown in recent years, and increased attention has turned to measuring the abundances of neutron capture elements. The relative abundances of r-process elements (e.g., europium) to s-process elements (e.g., barium, lanthanum and zirconium) in cluster stars reveal the relative contributions of Type II supernovae and low-mass AGB stars to the chemical evolution of the galactic disk. A recent study of cluster s-process element abundances has revealed a surprising trend of increasing s-process element abundance ([s/Fe]) with decreasing cluster age, at odds with current s-process yield predictions (D'Orazi et al. 2009, Maiorca et al. 2011). We have undertaken an analysis of Zr, Ba, La, and Eu abundances in 17 open clusters based on high resolution optical spectra. The sample spans 700 Myr to 10 Gyr in age and Rgc 7-22 kpc in galactocentric distance, allowing for the exploration of neutron capture [x/Fe] ratios as a function of age and location in the disk. Preliminary results confirm the trend of enhanced [s/Fe] with decreasing cluster age found by other studies, though with a weaker correlation. Here we present the latest results of this analysis, including newly-determined abundances for the r-process element Eu for an expanded cluster sample that includes outer disk objects. This research is supported by a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellowship to HRJ under award AST-0901919.

  2. Neutron stars and millisecond pulsars from accretion-induced collapse in globular clusters

    NASA Technical Reports Server (NTRS)

    Bailyn, Charles D.; Grindlay, Jonathan E.

    1990-01-01

    This paper examines the limits on the number of millisecond pulsars which could be formed in globular clusters by the generally accepted scenario (in which a neutron star is created by the supernova of an initially massive star and subsequently captures a companion to form a low-mass X-ray binary which eventually becomes a millisecond pulsar). It is found that, while the number of observed low-mass X-ray binaries can be adequately explained in this way, the reasonable assumption that the pulsar luminosity function in clusters extends below the current observational limits down to the luminosity of the faintest millisecond pulsars in the field suggests a cluster population of millisecond pulsars which is substantially larger than the standard model can produce. Alleviating this problem by postulating much shorter lifetimes for the X-ray binaries requires massive star populations sufficiently large that the mass loss resulting from their evolution would be likely to unbind the cluster. It is argued that neutron star formation in globular clusters by accretion-induced collapse of white dwarfs may resolve the discrepancy in birthrates.

  3. Neutron Capture Elements in the Open Cluster Chemical Abundance & Mapping (OCCAM) Survey

    NASA Astrophysics Data System (ADS)

    O'Connell, Julia; Frinchaboy, Peter M.; Shetrone, Matthew D.; Majewski, Steven R.; Zasowski, Gail; Hearty, Fred R.

    2016-01-01

    The Open Cluster Chemical Abundance & Mapping (OCCAM) survey is a systematic survey of Galactic open clusters using data primarily from the SDSS-III/APOGEE-1 survey. The high-resolution (R=22,500), near-infrared (H-band) APOGEE-1 survey allows for cluster membership probability determination and analysis of light and iron-peak elements. Neutron capture elements, however, prove to be elusive in the IR region covered by APOGEE. In an effort to fully study detailed Galactic chemical evolution, we conducted a high resolution (R~60,000) spectroscopic abundance analysis of neutron capture elements for OCCAM clusters in the optical regime to complement the APOGEE results. We present results for ten open clusters using data obtained at McDonald Observatory with the 2.1m Otto Struve telescope and Sandiford Echelle Spectrograph. We see abundance trends for Ba II, La II and Eu II that are consistent with Galactic abundance patterns for these elements. Ce II appears to be slightly enhanced in all program stars with a median value of ~0.1 dex and a spread of 0.5 dex for the entire sample.

  4. Experiment to find the neutron clusters in the decay of 238U nuclei

    NASA Astrophysics Data System (ADS)

    Bystritsky, V. M.; Dudkin, G. N.; Kuznetsov, S. I.; Varlachev, V. A.; Padalko, V. N.

    2016-10-01

    The first experiment was carried out, the task of which is the direct detection of neutron nuclei (number of bound neutrons ≥6) with a multineutron detector. The experimental results indicate that in the cluster decay of 238U there is a hexaneutrons and (or) octaneutrons. Multineutron detector made of 20 3He counters located in the moderator of polyethylene. The samples (emitters) from uranium trioxide (UO3) were the sources of neutron nuclei. The duration of the experiment was 112.66 days. For the probability of hexaneutrons and (or) octaneutrons emission of nuclei 238U with respect to the probability of α-decay mode are determined. The upper limits on the 90% confidence level are the following: λ(6n)/λα≤9.3×10-9and (or) λ(8n)/λα≤3.6×10-10.

  5. Gamma-ray spectroscopy of neutron-rich products of heavy-ion collisions

    SciTech Connect

    Carpenter, M.P.; Janssens, R.V.F.; Ahmad, I.

    1995-08-01

    Thick-target {gamma}{gamma} coincidence techniques are being used to explore the spectroscopy of otherwise hard-to-reach neutron-rich products of deep-inelastic heavy ion reactions. Extensive {gamma}{gamma} coincidence measurements were performed at ATLAS using pulsed beams of {sup 80}Se, {sup 136}Xe, and {sup 238}U on lead-backed {sup 122,124}Sn targets with energies 10-15% above the Coulomb barrier. Gamma-ray coincidence intensities were used to map out yield distributions with A and Z for even-even product nuclei around the target and around the projectile. The main features of the yield patterns are understandable in terms of N/Z equilibration. We had the most success in studying the decays of yrast isomers. Thus far, more than thirty new {mu}s isomers in the Z = 50 region were found and characterized. Making isotopic assignments for previously unknown {gamma}-ray cascades proves to be one of the biggest problems. Our assignments were based (a) on rare overlaps with radioactivity data, (b) on the relative yields with different beams, and (c) on observed cross-coincidences between {gamma} rays from light and heavy reaction partners. However, the primary products of deep inelastic collisions often are sufficiently excited for subsequent neutron evaporation, so {gamma}{gamma} cross-coincidence results require careful interpretation.

  6. Preequilibrium neutron emission in heavy ion reaction: Mean field effect and multiple emission

    NASA Astrophysics Data System (ADS)

    Paul, Sabyasachi; Nandy, Maitreyee; Mohanty, A. K.; Gambhir, Y. K.

    2016-09-01

    Effects of nuclear mean field and of multiple preequilibrium (PEQ) emission on double differential neutron multiplicity distribution from heavy ion reactions (12C+165Ho and 20Ne+165Ho ) at 10-30 MeV/u have been investigated in the framework of the semiclassical formalism for heavy ion reaction (henceforth termed "HION") developed earlier. HION follows the equilibration of a target+projectile composite system through the kinematics of two-body scattering. In the present work nuclear density distribution in the composite system is estimated in the relativistic mean field (RMF) approach. The nucleon-nucleon collision rates and subsequently the nucleon emission probability are calculated from this density distribution. A second approach based on a semiphenomenological formalism is also used for nuclear density distribution. Energy-angle distribution of neutron multiplicities calculated with this modified HION model coupled with multiple PEQ emission could reproduce the measured data of earlier workers in the projectile energy range of 10-30 MeV/u.

  7. The transient neutron star LMXB in the globular cluster Terzan 5 has turned into a Z-source

    NASA Astrophysics Data System (ADS)

    Altamirano, D.; Homan, J.; Linares, M.; Patruno, A.; Yang, Y.; Watts, A.; Kalamkar, M.; Casella, P.; Armas-Padilla, M.; Cavecchi, Y.; Degenaar, N.; Russell, D.; Kaur, R.; van der Klis, M.; Rea, N.; Wijnands, R.

    2010-10-01

    We report on the recent RXTE pointed observations of the the ongoing outburst of the neutron star (NS) transient source in the globular cluster Terzan 5 (Atel #2919, #2920, #2922, #2924, #2929, #2932, #2933, #2937, #2939, #2940, #2946).

  8. Density slope of the nuclear symmetry energy from the neutron skin thickness of heavy nuclei

    SciTech Connect

    Chen Liewen; Ko Che Ming; Xu Jun; Li Baoan

    2010-08-15

    Expressing explicitly the parameters of the standard Skyrme interaction in terms of the macroscopic properties of asymmetric nuclear matter, we show in the Skyrme-Hartree-Fock approach that unambiguous correlations exist between observables of finite nuclei and nuclear matter properties. We find that existing data on neutron skin thickness {Delta}r{sub np} of Sn isotopes give an important constraint on the symmetry energy E{sub sym}({rho}{sub 0}) and its density slope L at saturation density {rho}{sub 0}. Combining these constraints with those from recent analyses of isospin diffusion and the double neutron/proton ratio in heavy-ion collisions at intermediate energies leads to a more stringent limit on L approximately independent of E{sub sym}({rho}{sub 0}). The implication of these new constraints on the {Delta}r{sub np} of {sup 208}Pb as well as the core-crust transition density and pressure in neutron stars is discussed.

  9. Fuzzy hierarchical cross-clustering of data from abandoned mine site contaminated with heavy metals

    NASA Astrophysics Data System (ADS)

    Pourjabbar, A.; Sârbu, C.; Kostarelos, K.; Einax, J. W.; Büchel, G.

    2014-11-01

    The characteristics of pore water and slate samples are critically analyzed using fuzzy hierarchical cross-clustering statistical techniques. The main aim of this study was to investigate the source of contamination near an abandoned uranium mine in Germany. The mining activities were abandoned in 1990 the site was closed, and the surrounding area was remediated. However, heavy metal contamination is still detectable in water, soil and plants today. Hence, investigating the source of the current contamination is an important task. In order to achieve the goal, results from chemical analysis of both pore water samples and leachates from slate samples were initially analyzed using hard (classical) hierarchical clustering algorithms that did not provide meaningful results. By using two fuzzy clustering algorithms, Fuzzy Divisive Hierarchical Clustering (FDHC) and Fuzzy Hierarchical Cross-Clustering (FHCC), a relationship between the leachate from Ordovician-Silurian slate samples (10 samples collected from the test site and the surrounding area) and pore water samples (53 samples collected from 3 locations within the test site at 3 depths over the course of 4 years) was identified. The leachate data formed a cluster which was statistically similar to the cluster formed by the pore water samples collected from two of three locations. In addition, the fuzzy cross-clustering approach allowed for the identification of the characteristics (qualitative and quantitative) responsible for the observed similarities between all the samples. We conclude that the fuzzy algorithms were a better tool for the analysis and interpretation of geological/hydrogeological data where the data sets have an inherent vagueness/uncertainty.

  10. Heavy-baryon chiral perturbation theory approach to thermal neutron capture on {sup 3}He

    SciTech Connect

    Lazauskas, Rimantas; Park, Tae-Sun

    2011-03-15

    The cross section for radiative thermal neutron capture on {sup 3}He ({sup 3}He+n{yields}{sup 4}He+{gamma}; known as the hen reaction) is calculated based on heavy-baryon chiral perturbation theory. The relevant M1 operators are derived up to next-to-next-to-next-to-leading order (N{sup 3}LO). The initial and final nuclear wave functions are obtained from the rigorous Faddeev-Yakubovski equations for five sets of realistic nuclear interactions. Up to N{sup 3}LO, the M1 operators contain two low-energy constants, which appear as the coefficients of nonderivative two-nucleon contact terms. After determining these two constants using the experimental values of the magnetic moments of the triton and {sup 3}He, we carry out a parameter-free calculation of the hen cross section. The results are in good agreement with the data.

  11. Irradiation of nuclear track emulsions with thermal neutrons, heavy ions, and muons

    SciTech Connect

    Artemenkov, D. A. Bradnova, V.; Zaitsev, A. A.; Zarubin, P. I.; Zarubina, I. G.; Kattabekov, R. R.; Mamatkulov, K. Z.; Rusakova, V. V.

    2015-07-15

    Exposures of test samples of nuclear track emulsion were analyzed. Angular and energy correlations of products originating from the thermal-neutron-induced reaction n{sub th} +{sup 10} B → {sup 7} Li + (γ)+ α were studied in nuclear track emulsions enriched in boron. Nuclear track emulsions were also irradiated with {sup 86}Kr{sup +17} and {sup 124}Xe{sup +26} ions of energy about 1.2 MeV per nucleon. Measurements of ranges of heavy ions in nuclear track emulsionsmade it possible to determine their energies on the basis of the SRIM model. The formation of high-multiplicity nuclear stars was observed upon irradiating nuclear track emulsions with ultrarelativistic muons. Kinematical features studied in this exposure of nuclear track emulsions for events of the muon-induced splitting of carbon nuclei to three alpha particles are indicative of the nucleardiffraction interaction mechanism.

  12. Some remarks on in-situ studies using TEM-heavy-ion accelerator link from the stand point of extracting radiation damage caused by fast neutrons

    NASA Astrophysics Data System (ADS)

    Ishino, Shiori; Sekimura, Naoto; Murakami, Kenta; Abe, Hiroaki

    2016-04-01

    Radiation damage of materials for fission and fusion reactors has been scaled in terms of the number of displacements per atoms (dpa). The method of evaluating the dpa has been established and standardized. However, it has become obvious that more detailed analyses are required, particularly for the nature and spatial distribution of the introduced point defects and their clusters. Such detailed nature of the defects introduced is thought to be governed by the primary knock-on atom (PKA) spectrum, A number of trials to elucidate the PKA dependent radiation effects by choosing the mass and energy of the incident ions have been explored. In some cases, defect formation by a single impinging ion has been observed. However, it has also been recognized that there are a number of artefacts arising from energy deposition distributions, existence of surface sinks together with radiation induced surface modifications and so on. In this paper, discussion will be made on how to establish irradiation correlation between neutron and heavy ion irradiations in a cascade damage formation regime. For the past fifty years, the correlation between neutron and ion irradiations from the view point of simulating the neutron radiation damage by ion irradiations has been discussed many times. However, the correlation itself has not been fully discussed separately. This is the major objective of this paper.

  13. Characterization of neutron fields from bare and heavy water moderated (252)Cf spontaneous fission source using Bonner Sphere Spectrometer.

    PubMed

    Atanackovic, Jovica; Yonkeu, Andre; Dubeau, Jacques; Witharana, Sampath Hakmana; Priest, Nicholas

    2015-05-01

    In this work a calibrated Bonner Sphere Spectrometer (BSS), together with ISO shadow cones, was used to quantify the total and scattered components of bare and heavy water moderated (252)Cf neutron fields. All measurements were performed with a BSS that was calibrated at the National Physical Laboratory (NPL), Teddington, UK, which is a global primary standard laboratory and world-leading facility for neutron metrology and neutron instruments calibration. The fields were characterized for source-spectrometer distances of 80, 100, 150 and 200cm; and at heights of 103 and 200cm from the facility floor. As expected, the scattered contribution was greatest at the farthest distance from the source and closer to the floor. Hence, at a distance of 200cm and a height of 103cm, the scatter added to the direct field up to 162% of the total neutron fluence and up to 61% of the ambient dose equivalent, while at the same distance and height of 200cm above the floor, these values were up to 146% and 52%, respectively. In the case of heavy water moderated (252)Cf neutron fields, a shadow cone subtraction technique could not be implemented, however Monte Carlo simulations were utilized in order to differentiate between the direct and scatter components of the neutron fields. In this case, at a source-detector distance of 200cm and a height of 103cm, the scatter added to the direct field up to 148% of the total neutron fluence and up to 45% of the ambient dose equivalent, while at the same distance and a height of 200cm above the floor, these values were up to 134% and 42%, respectively.

  14. The Irradiation Characteristics of the Kur Heavy Water Facility (ii) - Neutron and Gamma-Ray Dose Measurements with a Twin-Chamber

    NASA Astrophysics Data System (ADS)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2003-06-01

    The Heavy Water Neutron Irradiation Facility of the Kyoto University Reactor can supply neutron energy spectra from almost pure thermal to mainly epi-thermal, using a spectrum shifter and thermal neutron filters. We will report about the measurement of the neutron and gamma-ray doses using a twin-chamber. The used twin-chamber is the combination of a tissue-equivalent ionization-chamber and a graphite ionization chamber, with detecting volumes of 80 cc. From the comparisons between the chamber-measured dose rates and the nominal values, it was confirmed that the relative dependencies of the neutron and gamma-ray doses on the heavy water thickness, were almost the same, excepting the smaller heavy-water-thickness mode, such as CB-0000-F.

  15. Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis.

    PubMed

    Nada, A; Abdel-Wahab, M; Sroor, A; Abdel-Haleem, A S; Abdel-Sabour, M F

    1999-07-01

    Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed.

  16. Heavy metals and rare earth elements source-sink in some Egyptian cigarettes as determined by neutron activation analysis.

    PubMed

    Nada, A; Abdel-Wahab, M; Sroor, A; Abdel-Haleem, A S; Abdel-Sabour, M F

    1999-07-01

    Heavy metals and rare earth elements in two types of cigarettes were studied. The contents of trace elements were determined by using delayed neutron activation analysis. In the present study 11 elements have been detected in popular and fine brand cigarettes marketed in Egypt. Evaluation of these elements with their potential hazards for smokers is briefly discussed. The material balance (source and sink) for each element was determined. Also the ratio of element recovery to the total amount was assessed. PMID:10376325

  17. Defect annealing in neutron and ion damaged silicon: Influence of defect clusters and doping

    NASA Astrophysics Data System (ADS)

    Fleming, R. M.; Seager, C. H.; Bielejec, E.; Vizkelethy, G.; Lang, D. V.; Campbell, J. M.

    2010-03-01

    We have explored defect annealing in radiation damaged silicon in a regime characterized by defect clusters and higher doping. Several types of pnp and npn Si bipolar transistors have been irradiated with ions and neutrons, then isochronally annealed from 300 to 600 K to study the evolution of deep level transient spectroscopy (DLTS) defect signatures. Variations in these data with radiation environment, Fermi level, annealing temperature, and doping density have been used to separate the contributions of three dominant defects to the DLTS defect spectra. We find that the normal Si divacancy and a divacancylike defect with similar properties make similar contributions to a DLTS peak normally associated with transitions from the single minus charge state of the divacancy. However the latter defect is clearly associated with the presence of defect clusters. The vacancy-donor center can also contribute to this high temperature DLTS signature, and its relative importance can be quantitatively assessed by varying doping density and the bias applied to the sample p/n junctions during annealing, and also by the observation that another, donor-related defect grows in as this center anneals. The ratio of vacancy-donor and vacancy-oxygen pairs appears to accurately follow that seen in earlier studies of gamma-irradiated Si. Discussions are presented concerning the effects of defect clustering on the structure, appearance, and evolution of the defects we have identified.

  18. Assessment of PM10 and heavy metals concentration in a Ceramic Cluster (NE Spain)

    NASA Astrophysics Data System (ADS)

    Belen Vicente, Ana; Pardo, Francisco; Sanfeliu, Teofilo; Bech, Joan

    2013-04-01

    Environmental pollution control is one of the most important goals in pollution risk assessment today. The aim of this study is conducting a retrospective view of the evolution of particulate matter (PM10) and heavy metals (As, Cd, Ni and Pb) at different localities in the Spanish cluster ceramic in the period between January 2007 and December 2011. The study area is in the province of Castellón. This province is a strategical area in the framework of European Union Pollution control. Approximately 80% of European ceramic tiles and ceramic frits manufacturers are concentrated in two areas, forming the so-called "Ceramics Clusters"; one is in Modena (Italy) and the other in Castellón (Spain). In this kind of areas, there are a lot of pollutants from this industry that represent an important contribution to soil contamination so it is necessary to control the air quality in them. These atmospheric particles are deposited in the ground through both dry and wet deposition. Soil is a major sink for heavy metals released into the environment. The level of pollution of soils by heavy metals depends on the retention capacity of the soil, especially on physical-chemical properties (mineralogy, grain size, organic matter) affecting soil particle surfaces and also on the chemical properties of the metal. The most direct consequences on the ground of air pollutants are acidification, salinization and the pollutions that can cause heavy metals as components of suspended particulate matter. For this purpose the levels of PM10 in ambient air and the corresponding annual and weekly trend were calculated. The results of the study show that the PM10 and heavy metals concentrations are below the limit values recommended by European Union Legislation for the protection of human health and ecosystems in the study period. There is an important reduction of them from 2009 in all control stations due to the economic crisis. References Moral, R., Gilkes, R.J., Jordán, M.M., 2005

  19. Clustering and relative velocity of heavy particles under gravitational settling in isotropic turbulent flows

    NASA Astrophysics Data System (ADS)

    Jin, Guodong; He, Guo-Wei

    2015-11-01

    Clustering and intermittency in radial relative velocity (RRV) of heavy particles of same size settling in turbulent flows can be remarkably changed due to gravity. Clustering is monotonically reduced at Stokes number less than 1 under gravity due to the disability of the centrifugal mechanism, however it is non-monotonically enhanced at Stokes number greater than 1 due to the multiplicative amplification in the case that the proposed effective Kubo number is less than 1. Although gravity causes monotonical reduction in the rms of RRV of particles at a given Stokes number with decreasing Froude number, the variation tendency in the tails of standardized PDF of RRV versus Froude number is obviously different: the tails become narrower at a small Stokes number, while they become broader at a large Stokes number. The mechanism of this variation stems from the compromise between the following two competing factors. The mitigation of correlation of particle positions and the regions of high strain rate which are more intermittent reduces the intermittency in RRV at small Stokes numbers, while the significant reduction in the backward-in-time relative separations will make particle pairs see small-scale structures, leading to a higher intermittency in RRV at large Stokes numbers. NSAF of China (grant number U1230126); NSFC (grant numbers 11072247 and 11232011).

  20. The collinear cluster tri-partition (CCT) of 252Cf (sf): New aspects from neutron gated data

    NASA Astrophysics Data System (ADS)

    Pyatkov, Yu. V.; Kamanin, D. V.; von Oertzen, W.; Alexandrov, A. A.; Alexandrova, I. A.; Falomkina, O. V.; Jacobs, N.; Kondratjev, N. A.; Kuznetsova, E. A.; Lavrova, Yu. E.; Malaza, V.; Ryabov, Yu. V.; Strekalovsky, O. V.; Tyukavkin, A. N.; Zhuchko, V. E.

    2012-07-01

    Results of two different experiments for the study of fission of 252Cf (sf) events in coincidence with neutrons are reported. Two time-of-flight-energy (TOF- E detectors systems have been used. The fission fragment masses were obtained in a double arm coincidence set-up, where the missing mass in the binary decay is used to characterise ternary fission as a collinear cluster tri-partition (CCT). The 3He filled neutron counters have been arranged so as to detect principally neutrons emitted from an isotropic source in the laboratory frame. The fission events connected to the larger experimental neutron multiplicities show a wide range in the missing-mass spectrum, down to α -particles, carbon and oxygen isotopes. These are linked with magic nuclei in the binary mass-mass correlations of the fission fragments. These neutron gated data are virtually free from background events from scattered binary fission fragments. The ungated spectra are compared to those of the previous data from our previous article (Eur. Phys. J. A. 45, 29 (2010)), the observed structures agree well with the manifestations of the collinear cluster tri-partition of 252Cf (sf) observed earlier. Several new families of the CCT modes are observed.

  1. Nano-cluster stability following neutron irradiation in MA957 oxide dispersion strengthened material

    NASA Astrophysics Data System (ADS)

    Ribis, J.; Lozano-Perez, S.

    2014-01-01

    ODS steels are promising materials for Sodium cooled Fast Reactors since their fine distribution of nano-clusters confers excellent mechanical properties. However, the nano-feature stability needs to be assessed under neutron irradiation. Before irradiation, the characterizations show that nano-particles are finely distributed within the ferritic matrix and are identified to have a pyrochlore type structure. After irradiation of the MA957 alloy in the Phenix French reactor at 412 °C up to 50 dpa and 430 °C up to 75 dpa, transmission electron microscopy characterization reveals a very slight density fall but no distinguishable difference in nano-features size before and after irradiation. In addition, after both irradiations, the nano-oxides are still (Y, Ti, O) compounds with orientation relationship with the matrix. A multislice simulation of high resolution images suggests that nano-particles still have a fcc pyrochlore type structure after irradiation. A possible change of lattice parameter seems to be highlighted, possibly due to disordering by cascade effect.

  2. ZIRCONIUM—HAFNIUM ISOTOPE EVIDENCE FROM METEORITES FOR THE DECOUPLED SYNTHESIS OF LIGHT AND HEAVY NEUTRON-RICH NUCLEI

    SciTech Connect

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-10

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope {sup 96}Zr (≤1ε in {sup 96}Zr/{sup 90}Zr) for bulk chondrites and CAIs (∼2ε). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the {sup 96}Zr isotope variations are of nucleosynthetic origin. The {sup 96}Zr enrichments are coupled with {sup 50}Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A ≤ 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. {sup 96}Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M{sub ☉}) SNII.

  3. Zirconium—Hafnium Isotope Evidence from Meteorites for the Decoupled Synthesis of Light and Heavy Neutron-rich Nuclei

    NASA Astrophysics Data System (ADS)

    Akram, W.; Schönbächler, M.; Sprung, P.; Vogel, N.

    2013-11-01

    Recent work based on analyses of meteorite and terrestrial whole-rock samples showed that the r- and s- process isotopes of Hf were homogeneously distributed throughout the inner solar system. We report new Hf isotope data for Calcium-Aluminum-rich inclusions (CAIs) of the CV3 carbonaceous chondrite Allende, and novel high-precision Zr isotope data for these CAIs and three carbonaceous chondrites (CM, CO, CK). Our Zr data reveal enrichments in the neutron-rich isotope 96Zr (<=1ɛ in 96Zr/90Zr) for bulk chondrites and CAIs (~2ɛ). Potential isotope effects due to incomplete sample dissolution, galactic and cosmic ray spallation, and the nuclear field shift are assessed and excluded, leading to the conclusion that the 96Zr isotope variations are of nucleosynthetic origin. The 96Zr enrichments are coupled with 50Ti excesses suggesting that both nuclides were produced in the same astrophysical environment. The same CAIs also exhibit deficits in r-process Hf isotopes, which provides strong evidence for a decoupling between the nucleosynthetic processes that produce the light (A <= 130) and heavy (A > 130) neutron-rich isotopes. We propose that the light neutron-capture isotopes largely formed in Type II supernovae (SNeII) with higher mass progenitors than the supernovae that produced the heavy r-process isotopes. In the context of our model, the light isotopes (e.g. 96Zr) are predominantly synthesized via charged-particle reactions in a high entropy wind environment, in which Hf isotopes are not produced. Collectively, our data indicates that CAIs sampled an excess of materials produced in a normal mass (12-25 M ⊙) SNII.

  4. Properties and synthesis of heavy nuclei and properties of neutron star matter

    NASA Technical Reports Server (NTRS)

    Buchler, J. R.

    1974-01-01

    The nuclear Thomas-Fermi model which is based on nuclear matter calculations has been successfully applied to the study of the bulk properties of nuclei. It is ideally suited for extrapolation into the region of very neutron-rich and of superheavy nuclei. It is therefore a valuable approach for r-process calculations as well as for the study of neutron star matter at subnuclear densities.

  5. Violence of heavy-ion reactions from neutron multiplicity: 11 to 20A-italic MeV /sup 20/Ne+ /sup 238/U

    SciTech Connect

    Jahnke, U.; Ingold, G.; Hilscher, D.; Lehmann, M.; Schwinn, E.; Zank, P.

    1986-07-14

    The suitability of the neutron multiplicity as a gauge for the violence of medium-energy heavy-ion reactions is investigated for the first time. For this purpose the number of neutrons emitted from fission reactions induced by 220-, 290-, and 400-MeV /sup 20/Ne on /sup 238/U is registered event-by-event with a large 4..pi.. scintillator tank. It is shown that the neutron multiplicity is indeed closely related to the two quantities characterizing the violence: the induced total intrinsic excitation and the linear momentum transfer.

  6. Neutron and X-Ray Diffraction Studies of Magnetic Order in Uranium-Based Heavy Fermion Superconductors

    NASA Astrophysics Data System (ADS)

    Lussier, Jean-Guy

    UPt_3, URu_2 Si_2, UNi_2 Al_3 and UPd_2 Al_3 form a special group among the uranium alloys because they exhibit heavy fermion character, magnetic order and superconductivity. This main interest in the study of this group of compounds resides in the simultaneous occurrence of magnetism and superconductivity at low temperature. Such a state could potentially involve an unconventional superconducting pairing mechanism, different from that contained in standard BCS theory. In this thesis, the magnetic states of three of these materials (URu_2Si _2, UNi_2Al _3 and UPd_2Al _3) is investigated with neutron and the relatively new resonant magnetic X-ray scattering techniques. The work presented here on URu_2Si _2 follows an earlier effort that demonstrated the applicabililty of the resonant X-ray technique to this weak magnetic system. Access to reciprocal space was extended in order to confirm the multipolar form of the resonant X-ray cross-section and to explore the limits of the technique compared to neutron scattering. The situation with the newly discovered UNi_2Al _3 and UPd_2Al _3 was different since their magnetic structure and phases needed first to be established. This task was achieved using two magnetic probes (neutron and X-ray scattering). Several magnetic order parameters in the normal and in the superconducting phase were also measured. The incommensurate magnetic order found in UNi_2Al_3 by neutron scattering constitutes the first observation of long range order in this compound. Other measurements on this compound provided some clues about the evolution of the magnetic structure in high magnetic fields.

  7. Neutrons as Party Animals: An Analogy for Understanding Heavy-Element Fissility

    NASA Astrophysics Data System (ADS)

    Reed, B. Cameron

    2012-12-01

    I teach a general education class on the history of nuclear physics and the Manhattan Project. About halfway through the course we come to the discovery of fission and Niels Bohr's insight that it is the rare isotope of uranium, U-235, which fissions under slow-neutron bombardment as opposed to the much more common U-238 isotope. As an "explanation" of the differing responses of the two isotopes to bombarding neutrons, I use the known (measured) masses of the various isotopes involved to compute the energies released upon neutron capture and then compare them to the fission barriers of the "compound" nuclei so formed (U-236 and U-239). The energy released in the (neutron + U-235) reaction exceeds the fission barrier by about one million electron-volts (1 MeV), while that for the (neutron + U-238) case falls about 1.6 MeV short. (The fission barriers are respectively about 5.7 and 6.5 MeV.)

  8. The mechanism of solute-enriched clusters formation in neutron-irradiated pressure vessel steels: The case of Fe-Cu model alloys

    NASA Astrophysics Data System (ADS)

    Subbotin, A. V.; Panyukov, S. V.

    2016-08-01

    Mechanism of solute-enriched clusters formation in neutron-irradiated pressure vessel steels is proposed and developed in case of Fe-Cu model alloys. The suggested solute-drag mechanism is analogous to the well-known zone-refining process. We show that the obtained results are in good agreement with available experimental data on the parameters of clusters enriched with the alloying elements. Our model explains why the formation of solute-enriched clusters does not happen in austenitic stainless steels with fcc lattice structure. It also allows to quantify the method of evaluation of neutron irradiation dose for the process of RPV steels hardening.

  9. Neutrons as Party Animals: An Analogy for Understanding Heavy-Element Fissility

    ERIC Educational Resources Information Center

    Reed, B. Cameron

    2012-01-01

    I teach a general education class on the history of nuclear physics and the Manhattan Project. About halfway through the course we come to the discovery of fission and Niels Bohr's insight that it is the rare isotope of uranium, U-235, which fissions under slow-neutron bombardment as opposed to the much more common U-238 isotope. As an…

  10. Isomeric states observed in heavy neutron-rich nuclei populated in the fragmentation of a 208Pb beam

    NASA Astrophysics Data System (ADS)

    Steer, S. J.; Podolyák, Zs.; Pietri, S.; Górska, M.; Grawe, H.; Maier, K. H.; Regan, P. H.; Rudolph, D.; Garnsworthy, A. B.; Hoischen, R.; Gerl, J.; Wollersheim, H. J.; Becker, F.; Bednarczyk, P.; Cáceres, L.; Doornenbal, P.; Geissel, H.; Grębosz, J.; Kelic, A.; Kojouharov, I.; Kurz, N.; Montes, F.; Prokopwicz, W.; Saito, T.; Schaffner, H.; Tashenov, S.; Heinz, A.; Pfützner, M.; Kurtukian-Nieto, T.; Benzoni, G.; Jungclaus, A.; Balabanski, D. L.; Bowry, M.; Brandau, C.; Brown, A.; Bruce, A. M.; Catford, W. N.; Cullen, I. J.; Dombrádi, Zs.; Estevez, M. E.; Gelletly, W.; Ilie, G.; Jolie, J.; Jones, G. A.; Kmiecik, M.; Kondev, F. G.; Krücken, R.; Lalkovski, S.; Liu, Z.; Maj, A.; Myalski, S.; Schwertel, S.; Shizuma, T.; Walker, P. M.; Werner-Malento, E.; Wieland, O.

    2011-10-01

    Heavy neutron-rich nuclei were populated via the fragmentation of a E/A=1 GeV 20882Pb beam. Secondary fragments were separated and identified and subsequently implanted in a passive stopper. By the detection of delayed γ rays, isomeric decays associated with these nuclei have been identified. A total of 49 isomers were detected, with the majority of them observed for the first time. The newly discovered isomers are in 204,20580Hg, 201,202,204,20579Au, 197,203,20478Pt, 195,199-20377Ir, 193,197-19976Os, 19675Re, 190,19174W, and 18973Ta. Possible level schemes are constructed and the structure of the nuclei discussed. To aid the interpretation, shell-model as well as BCS calculations were performed.

  11. Neutron excess number and nucleosynthesis of heavy elements in a type Ia supernova explosion

    NASA Astrophysics Data System (ADS)

    Panov, I. V.; Korneev, I. Y.; Blinnikov, S. I.; Röpke, F.

    2016-04-01

    Type Ia supernovae produce very powerful burst of light, which can be observed to high redshift. This fact is very attractive for cosmological applications. For supernova light curve modeling, it is very important to know the amount of Fe and Ni, formed during the explosion. In this paper, we explore both the chemical composition of the ejected supernova shells and the possibility of weak r-process under increased neutron excess number based on a set of trajectories of tracer particles, calculated in a hydrodynamic model of SNIa explosion. It is shown that no r-process elements are synthesized in the considered supernova model, even for an increased neutron excess number ( Y e ˜ 0.4) because of the slow evolution of temperature and density along chosen trajectories. The results of explosive nucleosynthesis are discussed.

  12. Probing the Equation of State of Neutron-Rich Matter with Heavy-Ion Collisions

    NASA Astrophysics Data System (ADS)

    Li, Bao-An

    2006-06-01

    The equation of state (EOS) of neutron-rich matter plays many important roles in both nuclear physics and astrophysics. However, it is still very poorly known, especially its isospin dependent part, namely the symmetry energy. Nuclear reactions with neutron-rich nuclei, stable and/or radioactive, provide a great opportunity to pin down the EOS of isospin asymmetric nuclear matter. In this talk, we report some recent theoretical progress in this field within an isospin and momentum dependent transport model (IBUU04). Using in-medium nucleon-nucleon cross sections consistent with the nuclear mean field used in the transport model, a symmetry energy of Esym(ρ) ≈ 31.6(ρ/ρ0)0.69 was found most acceptable compared with both the MSU isospin diffusion data and the presently acceptable neutron-skin thickness in 208Pb. The isospin dependent part Kasy(ρ0) of isobaric nuclear incompressibility was further narrowed down to -500 ± 50 MeV. Predictions on several observables sensitive to the density dependence of the symmetry energy at supranormal densities accessible at GSI and the planned Rare Isotope Accelerator (RIA) are also made.

  13. Contribution of neutron reactions in hybrid targets of inertial heavy ion fusion (HIF)

    NASA Astrophysics Data System (ADS)

    Imshennik, V. S.; Zhukov, V. T.

    2006-08-01

    Recently some simple estimations (Koskarev, Sharkov) were made for capability of achievement of critical conditions in an uranium shell of HIF energetic target, and afterwards it was proved use of an uranium shell (pusher) for substantial expansion of energy-release in a such hybrid target. The mentioned justification is included accounting of neutron-induced fission in the pusher. This accounting is formulated as generalization for cylindrical geometry of the well-known Axiezer-Pomeranchuk solution. A corresponding analytical solution of one-speed Payerls equation allows sufficiently accurately to compute the critical parameters of the uranium pusher in hydrodynamic model of compression and fusion of HIF target ( taking into account of development of chain nuclear fission reaction under critical condition achievement). Nevertheless the implemented computations show that the most essential effect is forced nuclear fission of uranium under the influence of thermonuclear neutrons generated by fusion of deuterium- tritium fuel in the central region of the target. In these computations we use a simple analytical description of forced nuclear fission of uranium by thermonuclear neutrons. The critical conditions are not achieved in the considered ( not optimized) hybrid targets but they are close to accomplishment in the investigated shock-free compression regime. This regime of compression is the most adequate one for hybrid HIF targets. The obtained results allow us to make conclusion of advisability of further development of energetic hybrid HIF targets particularly their optimization and utilization of natural uranium as pusher materials.

  14. Quasielastic small-angle neutron scattering from heavy water solutions of cyclodextrins.

    PubMed

    Kusmin, André; Lechner, Ruep E; Saenger, Wolfram

    2011-01-14

    We present a model for quasielastic neutron scattering (QENS) by an aqueous solution of compact and inflexible molecules. This model accounts for time-dependent spatial pair correlations between the atoms of the same as well as of distinct molecules and includes all coherent and incoherent neutron scattering contributions. The extension of the static theory of the excluded volume effect [A. K. Soper, J. Phys.: Condens. Matter 9, 2399 (1997)] to the time-dependent (dynamic) case allows us to obtain simplified model expressions for QENS spectra in the low Q region in the uniform fluid approximation. The resulting expressions describe the quasielastic small-angle neutron scattering (QESANS) spectra of D(2)O solutions of native and methylated cyclodextrins well, yielding in particular translational and rotational diffusion coefficients of these compounds in aqueous solution. Finally, we discuss the full potential of the QESANS analysis (that is, beyond the uniform fluid approximation), in particular, the information on solute-solvent interactions (e.g., hydration shell properties) that such an analysis can provide, in principle.

  15. On the internal pollution mechanisms in the globular cluster NGC 6121 (M4): heavy-element abundances and AGB models

    NASA Astrophysics Data System (ADS)

    D'Orazi, V.; Campbell, S. W.; Lugaro, M.; Lattanzio, J. C.; Pignatari, M.; Carretta, E.

    2013-07-01

    Globular clusters display significant variations in their light-element content, pointing to the existence of a second stellar generation formed from the ejecta of an earlier generation. The nature of these internal polluters is still a matter of debate: the two most popular scenarios indicate intermediate-mass asymptotic giant branch (IM-AGB) stars and fast rotating massive stars. Abundances determination for some key elements can help distinguish between these competitor candidates. We present in this paper Y abundances for a sample of 103 red giant branch stars in NGC 6121. Within measurement errors, we find that the [Y/Fe] is constant in this cluster contrary to a recent suggestion. For a subsample of six stars we also find [Rb/Fe] to be constant, consistent with previous studies showing no variation in other s-process elements. We also present a new set of stellar yields for IM-AGB stellar models of 5 and 6 M⊙, including heavy element s-process abundances. The uncertainties on the mass-loss rate, the mixing length parameter and the nuclear reaction rates have a major impact on the stellar abundances. Within the IM-AGB pollution scenario, the constant abundance of heavy elements inside the cluster requires a marginal s-process efficiency in IM-AGB stars. Such a constrain could still be satisfied by the present models assuming a stronger mass-loss rate. The uncertainties mentioned above are limiting the predictive power of IM-AGB models. For these reasons, at the moment we are not able to clearly rule out their role as main polluters of the second population stars in globular clusters.

  16. Shared Gene Structures and Clusters of Mutually Exclusive Spliced Exons within the Metazoan Muscle Myosin Heavy Chain Genes

    PubMed Central

    Kollmar, Martin; Hatje, Klas

    2014-01-01

    Multicellular animals possess two to three different types of muscle tissues. Striated muscles have considerable ultrastructural similarity and contain a core set of proteins including the muscle myosin heavy chain (Mhc) protein. The ATPase activity of this myosin motor protein largely dictates muscle performance at the molecular level. Two different solutions to adjusting myosin properties to different muscle subtypes have been identified so far: Vertebrates and nematodes contain many independent differentially expressed Mhc genes while arthropods have single Mhc genes with clusters of mutually exclusive spliced exons (MXEs). The availability of hundreds of metazoan genomes now allowed us to study whether the ancient bilateria already contained MXEs, how MXE complexity subsequently evolved, and whether additional scenarios to control contractile properties in different muscles could be proposed, By reconstructing the Mhc genes from 116 metazoans we showed that all intron positions within the motor domain coding regions are conserved in all bilateria analysed. The last common ancestor of the bilateria already contained a cluster of MXEs coding for part of the loop-2 actin-binding sequence. Subsequently the protostomes and later the arthropods gained many further clusters while MXEs got completely lost independently in several branches (vertebrates and nematodes) and species (for example the annelid Helobdella robusta and the salmon louse Lepeophtheirus salmonis). Several bilateria have been found to encode multiple Mhc genes that might all or in part contain clusters of MXEs. Notable examples are a cluster of six tandemly arrayed Mhc genes, of which two contain MXEs, in the owl limpet Lottia gigantea and four Mhc genes with three encoding MXEs in the predatory mite Metaseiulus occidentalis. Our analysis showed that similar solutions to provide different myosin isoforms (multiple genes or clusters of MXEs or both) have independently been developed several times

  17. Chiral vortaic effect and neutron asymmetries in heavy-ion collisions

    SciTech Connect

    Rogachevsky, Oleg V.; Sorin, Alexander S.; Teryaev, Oleg V.

    2010-11-15

    We study the possibility of testing experimentally signatures of P-odd effects related to the vorticity of the medium. The chiral vortaic effect is generalized to the case of conserved charges different from the electric one. In the case of baryonic charge and chemical potential, such an effect should manifest itself in neutron asymmetries measured by the Multipurpose Detector at the Nuclotron-Based Ion Collider Facility accelerator complex. The required accuracy may be achieved in a few months of accelerator running. We also discuss polarization of the hyperons and P-odd correlations of particle momenta (handedness) as probes of vorticity.

  18. Strong enhancement of dynamical emission of heavy fragments in the neutron-rich {sup 124}Sn+{sup 64}Ni reaction at 35A MeV

    SciTech Connect

    Russotto, P.; Amorini, F.; Cavallaro, S.; Di Toro, M.; Giustolisi, F.; Porto, F.; Rizzo, F.; De Filippo, E.; Pagano, A.; Cardella, G.; Lanzano, G.; Papa, M.; Pirrone, S.; Piasecki, E.; Auditore, L.; Trifiro, A.; Trimarchi, M.

    2010-06-15

    A quantitative comparison is made between the absolute cross sections associated with statistical and dynamical emission of heavy fragments in the {sup 124}Sn+{sup 64}Ni and {sup 112}Sn+{sup 58}Ni collisions experimentally investigated at 35A MeV beam energy using the multidetector CHIMERA. The result shows that the dynamical process is about twice as probable in the neutron-rich {sup 124}Sn+{sup 64}Ni system as in the {sup 112}Sn+{sup 58}Ni neutron-poor one. This unexpected and significant difference indicates that the reaction mechanism is strongly dependent on the entrance-channel isospin (N/Z) content.

  19. Demonstrating the likely neutron star nature of five M31 globular cluster sources with Swift-NuSTAR spectroscopy

    NASA Astrophysics Data System (ADS)

    Maccarone, Thomas J.; Yukita, Mihoko; Hornschemeier, Ann; Lehmer, Bret D.; Antoniou, Vallia; Ptak, Andrew; Wik, Daniel R.; Zezas, Andreas; Boyd, Padi; Kennea, Jamie; Page, Kim L.; Eracleous, Mike; Williams, Benjamin F.; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles J.; Harrison, Fiona A.; Stern, Daniel; Zhang, William W.

    2016-06-01

    We present the results of a joint Swift-NuSTAR spectroscopy campaign on M31. We focus on the five brightest globular cluster X-ray sources in our fields. Two of these had previously been argued to be black hole candidates on the basis of apparent hard-state spectra at luminosities above those for which neutron stars are in hard states. We show that these two sources are likely to be Z-sources (i.e. low magnetic field neutron stars accreting near their Eddington limits), or perhaps bright atoll sources (low magnetic field neutron stars which are just a bit fainter than this level) on the basis of simultaneous Swift and NuSTAR spectra which cover a broader range of energies. These new observations reveal spectral curvature above 6-8 keV that would be hard to detect without the broader energy coverage the NuSTAR data provide relative to Chandra and XMM-Newton. We show that the other three sources are also likely to be bright neutron star X-ray binaries, rather than black hole X-ray binaries. We discuss why it should already have been realized that it was unlikely that these objects were black holes on the basis of their being persistent sources, and we re-examine past work which suggested that tidal capture products would be persistently bright X-ray emitters. We discuss how this problem is likely due to neglecting disc winds in older work that predict which systems will be persistent and which will be transient.

  20. Production of new neutron-rich isotopes of heavy elements in fragmentation reactions of {sup 238}U projectiles at 1A GeV

    SciTech Connect

    Alvarez-Pol, H.; Benlliure, J.; Casarejos, E.; Cortina-Gil, D.; Fernandez-Dominguez, B.; Pereira, J.; Audouin, L.; Enqvist, T.; Schmidt, K.-H.; Yordanov, O.; Junghans, A. R.; Jurado, B.; Rejmund, F.

    2010-10-15

    The production of heavy neutron-rich nuclei has been investigated using cold-fragmentation reactions of {sup 238}U projectiles at relativistic energies. The experiment performed at the high-resolving-power magnetic spectrometer Fragment Separator at GSI made it possible to identify 40 new heavy neutron-rich nuclei: {sup 205}Pt, {sup 207-210}Au, {sup 211-216}Hg, {sup 214-217}Tl, {sup 215-220}Pb, {sup 219-224}Bi, {sup 223-227}Po, {sup 225-229}At, {sup 230,231}Rn, and {sup 233}Fr. The production cross sections of these nuclei were also determined and used to benchmark reaction codes that predict the production of nuclei far from stability.

  1. Energy Distributions of Neutrons Scattered from Graphite, Light and Heavy Water, Ice, Zirconium Hydride, Lithium Hydride, Sodium Hydride and Ammonium Chloride by the Beryllium Detector Method

    DOE R&D Accomplishments Database

    Woods, A. D. B.; Brockhouse, Bertram N.; Sakamoto, M.; Sinclair, R. N.

    1960-09-12

    Energy distributions of neutrons scattered from various moderators and from several hydrogenous substances were measured at energy transfers of 0.02 to 0.24 ev. Results from experiments on graphite, light and heavy water, ice, ZrH, LiH, NaH, and NH4Cl are included. It is noted that the results are of a preliminary character; however, they are probably the most accurate measurements of high-energy transfers yet made. (J.R.D.)

  2. Heavy ion collisions with A = 10/sup 57/: Aspects of nuclear stability and the nuclear equation of state in coalescing neutron-star binary systems

    SciTech Connect

    Mathews, G.J.; Wilson, J.R.; Evans, C.R.; Detweiler, S.L.

    1987-12-01

    The dynamics of the final stages of the coalescence of two neturon stars (such as the binary pulsar PSR 1913+16) is an unsolved problem in astrophysics. Such systems are probably efficient generators of gravitational radiation, and may be significant contributors to heavy-element nucleosynthesis. The input physics for the study of such systems is similar to that required for the strudy of heavy-ion collision hydrodynamics; e.g., a finite temperature nuclear equation of state, properties of nuclei away from stability, etc. We discuss the development of a relativistic hydrodynamics code in three spatial dimensions for the purpose of studying such neutron-star systems. The properties of the mass-radius relation (determined by the nuclear equation of state) may lead to a proposed mechanism by which hot, highly neutronized matter is ejected from the coalescing stars. This material is photodisintegrated into a free (mostly) neutron gas which may subsequently experience rapid-neutron capture (r-process) nucleosynthesis. 15 refs., 4 figs.

  3. A novel Al 2O 3 fluorescent nuclear track detector for heavy charged particles and neutrons

    NASA Astrophysics Data System (ADS)

    Akselrod, G. M.; Akselrod, M. S.; Benton, E. R.; Yasuda, N.

    2006-06-01

    A novel Al2O3 fluorescent nuclear track detector (FNTD), recently developed by Landauer, Inc., has demonstrated sensitivity and functionality superior to that of existing nuclear track detectors. The FNTD is based on single crystals of aluminum oxide doped with carbon and magnesium, and having aggregate oxygen vacancy defects (Al2O3:C,Mg). Radiation-induced color centers in the new material have an absorption band at 620 nm and produce fluorescence at 750 nm with a high quantum yield and a short, 75 ± 5 ns, fluorescence lifetime. Non-destructive readout of the detector is performed using a confocal fluorescence microscope. Scanning of the three-dimensional spatial distribution of fluorescence intensity along the track of a heavy charged particle (HCP) permits reconstruction of particle trajectories through the crystal and the LET can be determined as a function of distance along the trajectory based on the fluorescence intensity. Major advantages of Al2O3:C,Mg FNTD over conventionally processed CR-39 plastic nuclear track detector include superior spatial resolution, a wider range of LET sensitivity, no need for post-irradiation chemical processing of the detector and the capability to anneal and reuse the detector. Preliminary experiments have demonstrated that the material possesses a low-LET threshold of <1 keV/μm, does not saturate at LET in water as high as 1800 keV/μm, and is capable of irradiation to fluences in excess of 106 cm-2 without saturation (track overlap).

  4. Advances in implosion physics, alternative targets design, and neutron effects on heavy ion fusion reactors

    NASA Astrophysics Data System (ADS)

    Velarde, G.; Perlado, J. M.; Alonso, E.; Alonso, M.; Domínguez, E.; Rubiano, J. G.; Gil, J. M.; Gómez del Rio, J.; Lodi, D.; Malerba, L.; Marian, J.; Martel, P.; Martínez-Val, J. M.; Mínguez, E.; Piera, M.; Ogando, F.; Reyes, S.; Salvador, M.; Sanz, J.; Sauvan, P.; Velarde, M.; Velarde, P.

    2001-05-01

    The coupling of a new radiation transport (RT) solver with an existing multimaterial fluid dynamics code (ARWEN) using Adaptive Mesh Refinement named DAFNE, has been completed. In addition, improvements were made to ARWEN in order to work properly with the RT code, and to make it user-friendlier, including new treatment of Equations of State, and graphical tools for visualization. The evaluation of the code has been performed, comparing it with other existing RT codes (including the one used in DAFNE, but in the single-grid version). These comparisons consist in problems with real input parameters (mainly opacities and geometry parameters). Important advances in Atomic Physics, Opacity calculations and NLTE atomic physics calculations, with participation in significant experiments in this area, have been obtained. Early published calculations showed that a DT x fuel with a small tritium initial content ( x<3%) could work in a catalytic regime in Inertial Fusion Targets, at very high burning temperatures (≫100 keV). Otherwise, the cross-section of DT remains much higher than that of DD and no internal breeding of tritium can take place. Improvements in the calculation model allow to properly simulate the effect of inverse Compton scattering which tends to lower Te and to enhance radiation losses, reducing the plasma temperature, Ti. The neutron activation of all natural elements in First Structural Wall (FSW) component of an Inertial Fusion Energy (IFE) reactor for waste management, and the analysis of activation of target debris in NIF-type facilities has been completed. Using an original efficient modeling for pulse activation, the FSW behavior in inertial fusion has been studied. A radiological dose library coupled to the ACAB code is being generated for assessing impact of environmental releases, and atmospheric dispersion analysis from HIF reactors indicate the uncertainty in tritium release parameters. The first recognition of recombination barriers in Si

  5. Irradiation effects in 6H-SiC induced by neutron and heavy ions: Raman spectroscopy and high-resolution XRD analysis

    NASA Astrophysics Data System (ADS)

    Chen, Xiaofei; Zhou, Wei; Feng, Qijie; Zheng, Jian; Liu, Xiankun; Tang, Bin; Li, Jiangbo; Xue, Jianming; Peng, Shuming

    2016-09-01

    Irradiation effects of neutron and 3 MeV C+, Si+ in 6H-SiC were investigated by Raman spectroscopy and high-resolution XRD. The total disorder values of neutron irradiated SiC agree well with that of samples irradiated by ions at the same doses respectively. On the other hand, high-resolution XRD results shows that the lattice strain rate caused by neutron irradiation is 6.8%/dpa, while it is only 2.6%/dpa and 4.2%/dpa for Si+ and C+ irradiations respectively. Our results illustrate that the total disorder in neutron irradiated SiC can be accurately simulated by MeV Si+ or C+ irradiations at the same dose, but for the lattice strain and strain-related properties like surface hardness, the depth profile of irradiation damages induced by energetic ions must be considered. This research will contribute to a better understanding of the difference in irradiation effects between neutron and heavy ions.

  6. Formation of fragments in heavy-ion collisions using a modified clusterization method

    SciTech Connect

    Goyal, Supriya; Puri, Rajeev K.

    2011-04-15

    We study the formation and stability of the fragments by extending the minimum spanning tree method (MST) for clusterization. In this extension, each fragment is subjected to a binding-energy check calculated using the modified Bethe-Weizsaecker formula. Earlier, a constant binding-energy cut of 4 MeV/nucleon was imposed. Our results for {sup 197}Au+{sup 197}Au collisions are compared with ALADiN data and also with the calculations based on the simulated annealing technique. We shall show that the present modified version improves the agreement compared to the MST method.

  7. Neutron-scattering study of incommensurate magnetic order in the heavy-fermion superconductor UNi2Al3

    NASA Astrophysics Data System (ADS)

    Lussier, J. G.; Mao, M.; Schröder, A.; Garrett, J. D.; Gaulin, B. D.; Shapiro, S. M.; Buyers, W. J. L.

    1997-11-01

    Elastic neutron scattering from a single-crystal sample of the heavy-fermion superconductor UNi2Al3 has revealed the onset of long-range magnetic order below TN=4.6 K. This order is characterized by an incommensurate (IC) ordering wave vector given by (12+/-τ, 0, 12) with τ=0.11+/-0.003. The intensity of several magnetic satellite Bragg peaks within the (h,0,l) plane is well described by a model in which the spins lie within the basal plane and are modulated in amplitude from site to site. By applying a magnetic field to select from all the possible domains, we find that the moment is polarized along the a direction, with a maximum amplitude of 0.21+/-0.1μB per uranium atom. The order-parameter exponent β associated with this transition is 0.34+/-.03, which is typical of three-dimensional ordering transitions. Measurements down to ~0.3 K show that the magnetic order coexists with superconductivity below TC~1.2 K, and that these states are coupled as shown by anomalous behavior of the magnetic order parameter around TC. Measurements were also made in magnetic fields of up to 8 T applied perpendicular to the (h,0,l) plane, along (-1,1,0), a near-neighbor direction within the hexagonal basal plane. While the field does not influence TN, it does increase the intensity of the magnetic Bragg peaks by a factor of ~1.5, as well as increase the IC part of the ordering wave vector at low temperatures.

  8. Neutron diffraction study of magnetic field induced behavior in the heavy Fermion Ce3Co4Sn13

    SciTech Connect

    Christianson, Andrew D; Goremychkin, E. A.; Gardner, J. S.; Kang, H. J.; Chung, J.-H.; Manuel, P.; Thompson, J. D.; Sarrao, J. L.; Lawrence, J. M.

    2008-01-01

    The specific heat of Ce3Co4Sn13 exhibits a crossover from heavy Fermion behavior with antiferromagnetic correlations at low field to single impurity Kondo behavior above 2 T. We have performed neutron diffraction measurements in magnetic fields up to 6 Tesla on single crystal samples. The (001) position shows a dramatic increase in intensity in field which appears to arise from static polarization of the 4f level and which at 0.14 K also exhibits an anomaly near 2T reflecting the crossover to single impurity behavior.

  9. Prospects for further studies of effects of T-odd asymmetry in the emission of light particles in the polarized-neutron-induced ternary fission of heavy nuclei

    SciTech Connect

    Petrov, G. A. Gagarskii, A. M.; Guseva, I. S.; Kopatch, Yu. N.; Goennenwein, F.; Mutterer, M.

    2008-07-15

    Prospects for further studies of TRI and ROT effects of T-odd asymmetry in the emission of light particles in the ternary and binary fission of heavy nuclei that is induced by slow polarized neutrons are considered with a view to studying the mechanism for the formation of these effects and using them to get new information about fission dynamics. It is planned to investigate the dependence of the corresponding T-odd-asymmetry coefficients on the main characteristics of the fission reaction.

  10. Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D2-3He or CD4-3He clustering gases

    NASA Astrophysics Data System (ADS)

    Bang, W.; Barbui, M.; Bonasera, A.; Quevedo, H. J.; Dyer, G.; Bernstein, A. C.; Hagel, K.; Schmidt, K.; Gaul, E.; Donovan, M. E.; Consoli, F.; De Angelis, R.; Andreoli, P.; Barbarino, M.; Kimura, S.; Mazzocco, M.; Natowitz, J. B.; Ditmire, T.

    2013-09-01

    We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d,3He)n, D(d,t)p, and 3He(d,p)4He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time of flight and (2) utilizing the ratio of neutron yield to proton yield from D(d,3He)n and 3He(d,p)4He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

  11. Detailed chemical abundances in NGC 5824: another metal-poor globular cluster with internal heavy element abundance variations

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Mateo, Mario; Bailey, John I.; Spencer, Meghin; Crane, Jeffrey D.; Shectman, Stephen A.

    2016-01-01

    We present radial velocities, stellar parameters, and detailed abundances of 39 elements derived from high-resolution spectroscopic observations of red giant stars in the luminous, metal-poor globular cluster NGC 5824. We observe 26 stars in NGC 5824 using the Michigan/Magellan Fiber System (M2FS) and two stars using the Magellan Inamori Kyocera Echelle spectrograph. We derive a mean metallicity of [Fe/H] = -1.94 ± 0.02 (statistical) ±0.10 (systematic). The metallicity dispersion of this sample of stars, 0.08 dex, is in agreement with previous work and does not exceed the expected observational errors. Previous work suggested an internal metallicity spread only when fainter samples of stars were considered, so we cannot exclude the possibility of an intrinsic metallicity dispersion in NGC 5824. The M2FS spectra reveal a large internal dispersion in [Mg/Fe], 0.28 dex, which is found in a few other luminous, metal-poor clusters. [Mg/Fe] is correlated with [O/Fe] and anticorrelated with [Na/Fe] and [Al/Fe]. There is no evidence for internal dispersion among the other α- or Fe-group abundance ratios. 25 of the 26 stars exhibit a n-capture enrichment pattern dominated by r-process nucleosynthesis (<[Eu/Fe]> = +0.11 ± 0.12; <[Ba/Eu]> = -0.66 ± 0.05). Only one star shows evidence of substantial s-process enhancement ([Ba/Fe] = +0.56 ± 0.12; [Ba/Eu] = +0.38 ± 0.14), but this star does not exhibit other characteristics associated with s-process enhancement via mass transfer from a binary companion. The Pb and other heavy elements produced by the s-process suggest a time-scale of no more than a few hundred Myr for star formation and chemical enrichment, like the complex globular clusters M2, M22, and NGC 5286.

  12. On the idea of low-energy nuclear reactions in metallic lattices by producing neutrons from protons capturing "heavy" electrons

    NASA Astrophysics Data System (ADS)

    Tennfors, Einar

    2013-02-01

    The present article is a critical comment on Widom and Larsens speculations concerning low-energy nuclear reactions (LENR) based on spontaneous collective motion of protons in a room temperature metallic hydride lattice producing oscillating electric fields that renormalize the electron self-energy, adding significantly to the effective electron mass and enabling production of low-energy neutrons. The frequency and mean proton displacement estimated on the basis of neutron scattering from protons in palladium and applied to the Widom and Larsens model of the proton oscillations yield an electron mass enhancement less than one percent, far below the threshold for the proposed neutron production and even farther below the mass enhancement obtained by Widom and Larsen assuming a high charge density. Neutrons are not stopped by the Coulomb barrier, but the energy required for the neutron production is not low.

  13. Clustering of Color sources and the Equation of State in Heavy Ion Collisions at RHIC and LHC Energies

    NASA Astrophysics Data System (ADS)

    Scharenberg, R. P.

    2012-11-01

    The initial temperature Ti, energy density ɛi, and formation time τi of the initial state of the QGP formed in the heavy ion collisions at RHIC and LHC energies are determined using the data driven Color String Percolation Model (CSPM). Multiparticle production by interacting strings stretched between projectile and target form a spanning cluster at the percolation threshold. The relativistic kinetic theory relation for η/s is evaluated as a function of T and the mean free path (λmfp) using data and CSPM. η/s(Ti, λmfp) describes the transition from a strongly interacting QGP at T/Tc ~ 1 to a weakly coupled QGP at T/Tc >= 6. We find that the reciprocal of η/s is equal to the trace anomaly Δ = ɛ - 3P/T4 which also describes the transition. We couple this initial state of the QGP to a ID Bjorken expansion to determine the sound velocity c2s of the QGP for 0.85 <= T/Tc <= 3. The bulk thermodynamic quantities and the equation of state are in excellent agreement with LQCD results.

  14. Small-angle neutron scattering analysis of Mn–C clusters in high-manganese 18Mn–0.6C steel

    SciTech Connect

    Kang, Mihyun; Shin, Eunjoo; Woo, Wanchuck; Lee, Young-Kook

    2014-10-15

    Nanometer-scale particles (Mn–C clusters) were analyzed quantitatively using small-angle neutron scattering in 18Mn–0.6C (wt.%) austenite high-manganese steel. The size, number, and volume fraction of the particles were determined as a function of strain (0, 5, 15, 30, 45, 50%) at different temperatures (25 and 100 °C). The diameter of the cluster ranges from 2 to 14 nm in the matrix. The total volume fraction of the cluster significantly increases from 2.7 × 10{sup −6} to 8.7 × 10{sup −6} as the strain increases. Such clustering phenomenon is correlated to the serration behavior under loading in high-manganese steels. - Highlights: • Show Mn-C clustering as function of strain in 18Mn-0.6C TWIP steel. • Determine the size, number, and volume fraction of clusters quantitatively. • Compare the clustering behavior at 25 and 100 °C.

  15. Robust upward dispersion of the neutron spin resonance in the heavy fermion superconductor Ce1−xYbxCoIn5

    PubMed Central

    Song, Yu; Van Dyke, John; Lum, I. K.; White, B. D.; Jang, Sooyoung; Yazici, Duygu; Shu, L.; Schneidewind, A.; Čermák, Petr; Qiu, Y.; Maple, M. B.; Morr, Dirk K.; Dai, Pengcheng

    2016-01-01

    The neutron spin resonance is a collective magnetic excitation that appears in the unconventional copper oxide, iron pnictide and heavy fermion superconductors. Although the resonance is commonly associated with a spin-exciton due to the d(s±)-wave symmetry of the superconducting order parameter, it has also been proposed to be a magnon-like excitation appearing in the superconducting state. Here we use inelastic neutron scattering to demonstrate that the resonance in the heavy fermion superconductor Ce1−xYbxCoIn5 with x=0, 0.05 and 0.3 has a ring-like upward dispersion that is robust against Yb-doping. By comparing our experimental data with a random phase approximation calculation using the electronic structure and the momentum dependence of the -wave superconducting gap determined from scanning tunnelling microscopy (STM) for CeCoIn5, we conclude that the robust upward-dispersing resonance mode in Ce1−xYbxCoIn5 is inconsistent with the downward dispersion predicted within the spin-exciton scenario. PMID:27677397

  16. Transfer reactions with heavy elements

    SciTech Connect

    Hoffman, D.C.

    1986-04-01

    Transfer reactions for several transuranium elements are studied. (/sup 248/Cm, /sup 249/Bk, /sup 249/CF, /sup 254/Es), /sup 16,18/O, /sup 20,22/Ne, and /sup 40,48/Ca projectiles are used. The production of neutron-rich heavy actinides is enhanced by the use of neutron-rich projectiles /sup 18/O and /sup 22/Ne. The maxima of the isotopic distributions occur at only 2 to 3 mass numbers larger for /sup 48/Ca than for /sup 40/Ca reactions with /sup 248/Cm. The cross sections decrease rapidly with the number of nucleons transferred. The use of neutron-rich targets favors the production of neutron-rich isotopes. ''Cold'' heavy targets are produced. Comparisons with simple calculations of the product excitation energies assuming binary transfers indicate that the maxima of the isotopic distributions occur at the lightest product isotope for which the energy exceeds the reaction barrier. The cross sections for transfer of the same nucleon clusters appear to be comparable for a wide variety of systems. 23 refs., 4 figs., 4 tabs.

  17. Two-dimensional DORT discrete ordinates X-Y geometry neutron flux calculations for the Halden Heavy Boiling Water Reactor core configurations

    SciTech Connect

    Slater, C.O.

    1990-07-01

    Results are reported for two-dimensional discrete ordinates, X-Y geometry calculations performed for seven Halden Heavy Boiling Water Reactor core configurations. The calculations were performed in support of an effort to reassess the neutron fluence received by the reactor vessel. Nickel foil measurement data indicated considerable underprediction of fluences by the previously used multigroup removal- diffusion method. Therefore, calculations by a more accurate method were deemed appropriate. For each core configuration, data are presented for (1) integral fluxes in the core and near the vessel wall, (2) neutron spectra at selected locations, (3) isoflux contours superimposed on the geometry models, (4) plots of the geometry models, and (5) input for the calculations. The initial calculations were performed with several mesh sizes. Comparisons of the results from these calculations indicated that the uncertainty in the calculated fluxes should be less than 10%. However, three-dimensional effects (such as axial asymmetry in the fuel loading) could contribute to much greater uncertainty in the calculated neutron fluxes. 7 refs., 22 figs., 11 tabs.

  18. Heavy Metal Content in Airborne Dust of Childhood Leukemia Cluster Areas: Even Small Towns Have Air Pollutants

    NASA Astrophysics Data System (ADS)

    Sheppard, P. R.; Witten, M. L.

    2004-12-01

    Currently in the US, there are at least two ongoing clusters of childhood leukemia, where the incidence rate over the last several years has exceeded the national norm. In Fallon, Nevada, a town of 8,000 people, 16 children have been diagnosed with leukemia since 1995, three of whom have died. In Sierra Vista, Arizona, a town of 38,000 people, 12 children have been diagnosed since 1998, two of whom have died. A possible third cluster of childhood leukemia and other cancers is being monitored in Elk Grove, California, a suburb of Sacramento. For the purpose of characterizing the heavy metal content of airborne dust of these three communities, total suspended particulate samples were collected from each town as well as from nearby towns that could be considered as control comparisons. Sampling was done using portable high-volume blowers and glass- or quartz-fiber filter media. Filters were measured for elemental concentrations using inductively coupled plasma mass spectroscopy. To date, our most notable results are from the Nevada region. Compared to other control towns in the region, Fallon had significantly more tungsten in its airborne dust. Uranium was also higher in dust of Fallon than in other control towns. Uranium is a known health hazard, though it is not necessarily specifically related to childhood leukemia. The role of tungsten in childhood leukemia has not been widely studied. However, other research has identified tungsten exposure as an environmental concern in Fallon. A CDC study of human tissue samples from Fallon has shown high tungsten levels in people of Fallon, and a USGS study of drinking water in Fallon also has shown high tungsten there. Tree-ring research on selected trees has shown high tungsten values in recent rings compared to earlier rings. While these multiple indications of tungsten in the Fallon environment do not directly lead to the conclusion that tungsten causes leukemia, they do combine to suggest that biomedical research on the

  19. GLOBULAR CLUSTER ABUNDANCES FROM HIGH-RESOLUTION, INTEGRATED-LIGHT SPECTROSCOPY. IV. THE LARGE MAGELLANIC CLOUD: {alpha}, Fe-PEAK, LIGHT, AND HEAVY ELEMENTS

    SciTech Connect

    Colucci, Janet E.; Bernstein, Rebecca A.; McWilliam, Andrew E-mail: rab@ucolick.org E-mail: andy@ociw.edu

    2012-02-10

    We present detailed chemical abundances in eight clusters in the Large Magellanic Cloud (LMC). We measure abundances of 22 elements for clusters spanning a range in age of 0.05-12 Gyr, providing a comprehensive picture of the chemical enrichment and star formation history of the LMC. The abundances were obtained from individual absorption lines using a new method for analysis of high-resolution (R {approx} 25,000), integrated-light (IL) spectra of star clusters. This method was developed and presented in Papers I, II, and III of this series. In this paper, we develop an additional IL {chi}{sup 2}-minimization spectral synthesis technique to facilitate measurement of weak ({approx}15 mA) spectral lines and abundances in low signal-to-noise ratio data (S/N {approx} 30). Additionally, we supplement the IL abundance measurements with detailed abundances that we measure for individual stars in the youngest clusters (age < 2 Gyr) in our sample. In both the IL and stellar abundances we find evolution of [{alpha}/Fe] with [Fe/H] and age. Fe-peak abundance ratios are similar to those in the Milky Way (MW), with the exception of [Cu/Fe] and [Mn/Fe], which are sub-solar at high metallicities. The heavy elements Ba, La, Nd, Sm, and Eu are significantly enhanced in the youngest clusters. Also, the heavy to light s-process ratio is elevated relative to the MW ([Ba/Y] >+0.5) and increases with decreasing age, indicating a strong contribution of low-metallicity asymptotic giant branch star ejecta to the interstellar medium throughout the later history of the LMC. We also find a correlation of IL Na and Al abundances with cluster mass in the sense that more massive, older clusters are enriched in the light elements Na and Al with respect to Fe, which implies that these clusters harbor star-to-star abundance variations as is common in the MW. Lower mass, intermediate-age, and young clusters have Na and Al abundances that are lower and more consistent with LMC field stars. Our

  20. Heavy Cluster Knockout Reaction O16(C12,2C12)He4 and the Nature of the C12-C12 Interaction Potential

    NASA Astrophysics Data System (ADS)

    Joshi, B. N.; Jain, Arun K.; Gupta, Y. K.; Biswas, D. C.; Saxena, A.; John, B. V.; Danu, L. S.; Vind, R. P.; Choudhury, R. K.

    2011-01-01

    The heavy cluster knockout reaction O16(C12,2C12)He4 performed for the first time, reveals the true nature of the C12-C12 interaction. The observed cross section is enhanced by almost 2 orders of magnitude over the conventional zero range distorted wave impulse approximation (DWIA) predictions. An attractive C12-C12 optical potential, as obtained in the folding model, does not explain the enhanced cross section in the finite range (FR) DWIA framework. The inclusion of a hard core of fairly long range ˜3.65fm explains the data. The present investigation of O16(C12,2C12)He4 along with the C12-C12 elastic scattering also proves beyond doubt that the folding model’s deep attractive heavy ion potentials are unsuitable to describe the highly overlapping heavy ions. The application of FR-DWIA opens up new avenues to use the heavy core knockout for the detailed investigation of heavy as well as Borromean halo nuclei.

  1. RBE and genetic susceptibility of mouse and rat spermatogonial stem cells to protons, heavy charged particles and 1.5 MeV neutrons

    NASA Astrophysics Data System (ADS)

    Vaglenov, A.; Fedorenko, B.; Kaltenboeck, B.

    The main purpose of the present study is to provide data on RBE and genetic susceptibility in the mouse and the rat when exposed to protons, HZE particles and neutrons. Genetic damage from exposure to 50 MeV and 9 GeV protons, 4 GeV/nucleon helium ions, 4 GeV/nucleon carbon ions and 1.5 MeV neutrons was studied in adult (CBA × C57Bl/6J) F1 mice. Damage from 9 GeV protons and 4 GeV helium ions was studied in adult Wistar rats. The incidence of reciprocal translocations (RT) induced in the spermatogonial stem cells of each species was recorded. RBE values were derived by comparing linear regression coefficients from dose-responses within the same dose-range for each of the radiation types tested and 60Co γ-rays or by means of a direct nonparametric method. RT yields measured after mouse and rat spermatogonial irradiation with protons, heavy charged particles and neutrons fit the linear model of the dose-response relationship. Relative to 60Co γ-rays, RBE values are as follows for mouse spermatogonia: 0.9 for 50 MeV protons; 1.3 for 9 GeV protons; 0.7 for 4 GeV helium ions; and 1.3 for 4 GeV carbon ions. For rat spermatogonia, values were: 1.7 for 9 GeV protons and 1.3 for helium ions. Compared to mice irradiated using the same experimental design, rats were more susceptible to high-LET radiations, with susceptibility assessed by genetic damage to their spermatogonial stem cells. The RBE of 1.5 MeV neutron is about 6.6.

  2. Concomitant formation of different nature clusters and hardening in reactor pressure vessel steels irradiated by heavy ions

    NASA Astrophysics Data System (ADS)

    Fujii, K.; Fukuya, K.; Hojo, T.

    2013-11-01

    Specimens of A533B steels containing 0.04, 0.09 and 0.21 wt%Cu were irradiated at 290 °C to 3 dpa with 3 MeV Fe ions and subjected to atom probe analyses, transmission electron microscopy observations and hardness measurements. The atom probe analysis results showed that two types of solute clusters were formed: Cu-enriched clusters containing Mn, Ni and Si atoms as irradiation-enhanced solute atom clusters and Mn/Ni/Si-enriched clusters as irradiation-induced solute atom clusters. Both cluster types occurred in the highest Cu-content steel and the ratio of Mn/Ni/Si-enriched clusters to Cu-enriched clusters increased with irradiation doses. It was confirmed that the cluster formation was a key factor in the microstructure evolution until the high dose irradiation was reached even in the low Cu content steels though the dislocation loops with much lower density than that of the clusters were observed as matrix damage. The difference in the hardening efficiency due to the difference in the nature of the clusters was small. The irradiation-induced clustering of undersized Si atoms suggested that a clustering driving force other than vacancy-driven diffusion, probably an interstitial mechanism, may become important at higher dose rates.

  3. Use of boron cluster-containing redox nanoparticles with ROS scavenging ability in boron neutron capture therapy to achieve high therapeutic efficiency and low adverse effects.

    PubMed

    Gao, Zhenyu; Horiguchi, Yukichi; Nakai, Kei; Matsumura, Akira; Suzuki, Minoru; Ono, Koji; Nagasaki, Yukio

    2016-10-01

    A boron delivery system with high therapeutic efficiency and low adverse effects is crucial for a successful boron neutron capture therapy (BNCT). In this study, we developed boron cluster-containing redox nanoparticles (BNPs) via polyion complex (PIC) formation, using a newly synthesized poly(ethylene glycol)-polyanion (PEG-polyanion, possessing a (10)B-enriched boron cluster as a side chain of one of its segments) and PEG-polycation (possessing a reactive oxygen species (ROS) scavenger as a side chain of one of its segments). The BNPs exhibited high colloidal stability, selective uptake in tumor cells, specific accumulation, and long retention in tumor tissue and ROS scavenging ability. After thermal neutron irradiation, significant suppression of tumor growth was observed in the BNP-treated group, with only 5-ppm (10)B in tumor tissues, whereas at least 20-ppm (10)B is generally required for low molecular weight (LMW) (10)B agents. In addition, increased leukocyte levels were observed in the LMW (10)B agent-treated group after thermal neutron irradiation, and not in BNP-treated group, which might be attributed to its ROS scavenging ability. No visual metastasis of tumor cells to other organs was observed 1 month after irradiation in the BNP-treated group. These results suggest that BNPs are promising for enhancing the BNCT performance. PMID:27467416

  4. Use of boron cluster-containing redox nanoparticles with ROS scavenging ability in boron neutron capture therapy to achieve high therapeutic efficiency and low adverse effects.

    PubMed

    Gao, Zhenyu; Horiguchi, Yukichi; Nakai, Kei; Matsumura, Akira; Suzuki, Minoru; Ono, Koji; Nagasaki, Yukio

    2016-10-01

    A boron delivery system with high therapeutic efficiency and low adverse effects is crucial for a successful boron neutron capture therapy (BNCT). In this study, we developed boron cluster-containing redox nanoparticles (BNPs) via polyion complex (PIC) formation, using a newly synthesized poly(ethylene glycol)-polyanion (PEG-polyanion, possessing a (10)B-enriched boron cluster as a side chain of one of its segments) and PEG-polycation (possessing a reactive oxygen species (ROS) scavenger as a side chain of one of its segments). The BNPs exhibited high colloidal stability, selective uptake in tumor cells, specific accumulation, and long retention in tumor tissue and ROS scavenging ability. After thermal neutron irradiation, significant suppression of tumor growth was observed in the BNP-treated group, with only 5-ppm (10)B in tumor tissues, whereas at least 20-ppm (10)B is generally required for low molecular weight (LMW) (10)B agents. In addition, increased leukocyte levels were observed in the LMW (10)B agent-treated group after thermal neutron irradiation, and not in BNP-treated group, which might be attributed to its ROS scavenging ability. No visual metastasis of tumor cells to other organs was observed 1 month after irradiation in the BNP-treated group. These results suggest that BNPs are promising for enhancing the BNCT performance.

  5. Secondary Neutron-Production Cross Sections from Heavy-IonInteractions between 230 and 600 MeV/nucleon

    SciTech Connect

    Heilbronn, L.H.; Zeitlin, C.J.; Iwata, Y.; Murakami, T.; Iwase,H.; Nakamura, T.; Nunomiya, T.; Sato, H.; Yashima, H.; Ronningen, R.M.; Ieki, K.

    2006-10-04

    Secondary neutron-production cross-sections have beenmeasured from interactions of 230 MeV/nucleon He, 400 MeV/nucleon N, 400MeV/nucleon Kr, 400 MeV/nucleon Xe, 500 MeV/nucleon Fe, and 600MeV/nucleon Ne interacting in a variety of elemental and compositetargets. We report the double-differential production cross sections,angular distributions, energy spectra, and total cross sections from allsystems. Neutron energies were measured using the time-of-flighttechnique, and were measured at laboratory angles between 5 deg and 80deg. The spectra exhibit behavior previously reported in otherheavy-ion-induced neutron production experiments; namely, a peak atforward angles near the energy corresponding to the beam velocity, withthe remaining spectra generated by preequilibrium and equilibriumprocesses. The double-differential spectra are fitted with amoving-source parameterization. Observations on the dependence of thetotal cross sections on target and projectile mass arediscussed.

  6. Neutron Exposure Parameters for the Dosimetry Capsule in the Heavy-Section Steel Irradiation Program Tenth Irradiation Series

    SciTech Connect

    C.A. Baldwin; F.B.K. Kam; I. Remec

    1998-10-01

    This report describes the computational methodology for the least-squares adjustment of the dosimetry data from the HSSI 10.OD dosimetry capsule with neutronics calculations. It presents exposure rates at each dosimetry location for the neutron fluence greater than 1.0 MeV, fluence greater than 0.1 MeV, and displacements per atom. Exposure parameter distributions are also described in terms of three- dimensional fitting functions. When fitting functions are used it is suggested that an uncertainty of 6% (1 o) should be associated with the exposure rate values. The specific activity of each dosimeter at the end of irradiation is listed in the Appendix.

  7. [Relative biological effectiveness of accelerated heavy ions and fast neutrons estimated from frequency of aberration mytoses in the retinal epithelium].

    PubMed

    Vorozhtsova, S V; Shafirkin, A V; Fedorenko, B S

    2006-01-01

    Analyzed was the literature and authors' experimental data concerning lesion and recovery of epithelium cells of mice retina immediately and long after irradiation at different sources including single and partly fractionated irradiation by gamma- and X-rays, accelerated protons, helium, carbon and boron ions, and fast neutrons of the reactor range in a large spectrum of doses and LET. Reviewed are some new techniques of determining the RBE coefficient for these types of radiation; large values of the RBE coefficients for accelerated ions and neutrons (5-10 times higher than RBE coefficients calculated for the next day following irradiation) are a result of integration into calculation of the available data about the delayed disorders in retinal epithelium cell regeneration. PMID:17193969

  8. How the projectile neutron number influences the evaporation cross section in complete fusion reactions with heavy ions

    SciTech Connect

    Wang Chengbin; Zhang Jinjuan; Ren, Z. Z.; Shen, C. W.

    2010-11-15

    The influence of the projectile neutron number on the evaporation residue cross sections for the reactions {sup 208}Pb({sup 52,54}Cr,n,2n){sup 258-261}Sg and {sup 208}Pb({sup 48,50}Ti,n,2n){sup 254-257}Rf has been studied within the framework of a fusion-fission statistical model. The results obtained with the kewpie2 code are compared with recent experimental data. The excitation functions represent the experimental results well both in the maximum value and the lactation of the peak. The calculations show that the projectile neutron number greatly influences both the capture cross section and the fusion probability.

  9. Finding Groups Using Model-Based Cluster Analysis: Heterogeneous Emotional Self-Regulatory Processes and Heavy Alcohol Use Risk

    ERIC Educational Resources Information Center

    Mun, Eun Young; von Eye, Alexander; Bates, Marsha E.; Vaschillo, Evgeny G.

    2008-01-01

    Model-based cluster analysis is a new clustering procedure to investigate population heterogeneity utilizing finite mixture multivariate normal densities. It is an inferentially based, statistically principled procedure that allows comparison of nonnested models using the Bayesian information criterion to compare multiple models and identify the…

  10. Cs-137 geochronology, epithermal neutron activation analysis, and principal component analysis of heavy metals pollution of the Black Sea anoxic continental shelf sediments

    NASA Astrophysics Data System (ADS)

    Duliu, O. G.; Cristache, C.; Oaie, G.; Culicov, O. A.; Frontasyeva, M. V.

    2009-04-01

    concentrations; k represents the surface to plateau relative increment of concentration; Z represents concentration decrement: the depth at which the concentration becomes 1+k times greater than plateau one. Final results have shown with clarity that in the case of Zn, As, Br, Sn and Sb, the concentrations near sediment surface were 1.6 to 4.1 times greater then the plateau ones while Sc vertical profile, excepting some small fluctuations observed between 18 to 25 cm below surface, shown to be almost constant. Moreover, the concentration decrements Z of Zn, Br, Sn and Sb were almost coincident within one standard deviation while in the case of As, this coincidence appears within two standard deviation, these facts pleading for a comparable time evolution in the past 100 years. On the other hand, in the case of Sn and As, the maximum concentrations were reached 1 cm below the sediment surface, roughly corresponding to 1990 year, while the concentrations of all other three elements monotonously increases up to sediment surface. Further Principal Components Analysis of the data concerning the vertical distribution of all six elements illustrates the presence of two distinct clusters, one consisting of Zn, As, Br, Sn and Sb and the other on only of Sn, attesting both differences and similarities in the vertical distribution of considered elements. By comparing the experimental concentrations of all five elements with Romania Regulations concerning heavy metal pollution, we remarked that, by respect to these Regulations the only Zn, As, Br and Sb slightly exceeded normal accepted limits while the minimum alert concentrations were exceeded only in few cases by of As and Br, but no elements concentrations reached the intervention threshold. In our opinion, these results reflect the dynamics of the industrial activity in the riparian to Danube River European countries: a steady increase beginning with the last half of the XIX-th century followed by a slightly decline after the fall of

  11. Reaction dynamics and nuclear structure of moderately neutron-rich Ne isotopes by heavy-ion reactions

    NASA Astrophysics Data System (ADS)

    Bottoni, S.; Benzoni, G.; Leoni, S.; Montanari, D.; Bracco, A.; Azaiez, F.; Franchoo, S.; Stefan, I.; Blasi, N.; Camera, F.; Crespi, F. C. L.; Corsi, A.; Million, B.; Nicolini, R.; Vigezzi, E.; Wieland, O.; Zocca, F.; Corradi, L.; De Angelis, G.; Fioretto, E.; Guiot, B.; Marginean, N.; Napoli, D. R.; Orlandi, R.; Sahin, E.; Stefanini, A. M.; Valiente-Dobon, J. J.; Aydin, S.; Bazzacco, D.; Farnea, E.; Lenzi, S.; Lunardi, S.; Mason, P.; Mengoni, D.; Montagnoli, G.; Recchia, F.; Ur, C.; Scarlassara, F.; Gadea, A.; Maj, A.; Wrzesinski, J.; Zuber, K.; Dombradi, Zs.; Szilner, S.; Saltarelli, A.; Pollarolo, G.

    2012-06-01

    The heavy-ion reaction 22Ne+208Pb at 128 MeV beam energy has been studied using the PRISMA-CLARA experimental setup at Legnaro National Laboratories. Elastic, inelastic, and one-nucleon transfer differential cross sections are measured and global agreement is obtained with semiclassical and distorted-wave Born approximation (DWBA) calculations. In particular, the angular distribution of the 2+ state of 22Ne is analyzed by DWBA and a similar calculation is performed for the unstable 24Ne nucleus, using existing data from the reaction 24Ne+208Pb at 182 MeV (measured at SPIRAL with the VAMOS-EXOGAM setup). In both cases the DWBA model gives a good reproduction of the experiment, pointing to a strong reduction of the β2C charge deformation parameter in 24Ne. This follows the trend predicted for the evolution of the quadrupole deformation along the Ne isotopic chain.

  12. Effects of T-odd asymmetry of the emission of light charged particles and photons during fission of heavy nuclei by polarized neutrons

    SciTech Connect

    Gagarskii, A. M.; Guseva, I. S.; Goennenwein, F.; Kopach, Yu. N.; Mutterer, M.; Kuz'mina, T. E.; Petrov, G. A.; Tyurin, G.; Nesvizhevsky, V.

    2011-12-15

    The new physical effects of T-odd asymmetry of the emission of light charged particles (LCPs) during the ternary fission of some heavy nuclei by cold polarized neutrons have been experimentally studied. The coefficients of triple scalar and vector correlation of the pulses of light particles and fission fragments (TRI effect) and the fivefold correlation of the same vectors (ROT effect) have been measured. These effects are believed to be caused by the rotation of polarized fissioning system around its polarization direction. The treatment of the experimental data for LCPs in the framework of this hypothesis leads to a good agreement between the calculation results and experimental data. The calculated value of the angle of rotation of the fission axis in the ternary fission of the polarized fissioning {sup 236}U* compound nucleus was used to process the results of measuring the ROT effect for {gamma} photons from binary-fission fragments of the same nucleus. A satisfactory description of these experimental data is obtained which serves a convincing confirmation of the rotation hypothesis.

  13. Experimental Data of Neutron Yields from Thick Targets Bombarded by 100 to 800 MeV / Nucleon Heavy Ions.

    2001-05-15

    Version 02 The recent experimental data by the authors listed above are summarized in this paper on differential neutron yields in energy and angle produced by 100, 155 and 180 MeV/nucleon He, 100, 155, 180 and 400 MeV/nucleon C, 100, 180, 400 MeV/nucleon Ne, 400MeV/nucleon Ar, Xe and Fe, 272 and 435MeV/nucleon Nb and 800 MeV/nucleon Si ions stopping in thick targets of C, Al, Cu, Pb and Nb. The paper referenced above is availablemore » on the RSICC web site. The numerical values of the data, which were used to plot figures in References 3, 4, 5, 6 and 8 of this paper, are available for download at no charge. To get access to the data, complete a RSICC registration form and order form. Both are available by clicking on "Ordering" from the RSICC web pages. You will be contacted with details about how to proceed.« less

  14. On the structure of concentrated detonation nanodiamond hydrosols with a positive ζ potential: Analysis of small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Avdeev, Mikhail V.; Tomchuk, Oleksandr V.; Ivankov, Oleksandr I.; Alexenskii, Alexander E.; Dideikin, Artur T.; Vul, Alexander Ya.

    2016-08-01

    Small-angle neutron scattering (SANS) was applied for the structure characterization of detonation nanodiamond (DND) aqueous suspensions with a positive ζ potential. The contrast variation technique (based on mixtures of light and heavy water) was used to study the structure of DND particles and their clusters in solutions. The results were compared with the data of the previous similar experiments for DND suspensions with a negative ζ potential. The experimental range of the neutron scattering contrast in the system was extended to maximally possible by starting with the initial concentrated suspensions separately prepared in light and heavy water.

  15. Phasing and structure of bestrophin-1: a case study in the use of heavy-atom cluster compounds with multi-subunit transmembrane proteins

    PubMed Central

    Kane Dickson, Veronica

    2016-01-01

    The purification and three-dimensional crystallization of membrane proteins are commonly affected by a cumulation of pathologies that are less prevalent in their soluble counterparts. This may include severe anisotropy, poor spot shape, poor to moderate-resolution diffraction, crystal twinning, translational pseudo-symmetry and poor uptake of heavy atoms for derivatization. Such challenges must be circumvented by adaptations in the approach to crystallization and/or phasing. Here, an example of a protein that exhibited all of the above-mentioned complications is presented. Bestrophin-1 is a eukaryotic calcium-activated chloride channel, the structure of which was recently determined in complex with monoclonal antibody fragments using SAD phasing with tantalum bromide clusters (Ta6Br12·Br2). Some of the obstacles to obtaining improved diffraction and phasing for this particular channel are discussed, as well as the approach and adaptations that were key to determining the structure. PMID:26960119

  16. Phasing and structure of bestrophin-1: a case study in the use of heavy-atom cluster compounds with multi-subunit transmembrane proteins.

    PubMed

    Kane Dickson, Veronica

    2016-03-01

    The purification and three-dimensional crystallization of membrane proteins are commonly affected by a cumulation of pathologies that are less prevalent in their soluble counterparts. This may include severe anisotropy, poor spot shape, poor to moderate-resolution diffraction, crystal twinning, translational pseudo-symmetry and poor uptake of heavy atoms for derivatization. Such challenges must be circumvented by adaptations in the approach to crystallization and/or phasing. Here, an example of a protein that exhibited all of the above-mentioned complications is presented. Bestrophin-1 is a eukaryotic calcium-activated chloride channel, the structure of which was recently determined in complex with monoclonal antibody fragments using SAD phasing with tantalum bromide clusters (Ta6Br12·Br2). Some of the obstacles to obtaining improved diffraction and phasing for this particular channel are discussed, as well as the approach and adaptations that were key to determining the structure. PMID:26960119

  17. Analysis of the proposed relocation of the neutron criticality clusters in the process buildings for the Portsmouth Gaseous Diffusion Plant

    SciTech Connect

    Negron, S.B.; Tayloe, R.W. Jr.

    1994-01-01

    Radiation levels in Buildings X-326, X-330 and X-333 have been determined for the ANSI minimum accident of concern at both the current and the proposed locations of the criticality alum system neutron detectors. This was performed in order to evaluate whether or not the detectors could be lowered from their current positions and still respond to the minimum accident of concern. Relocating the detectors could reduce the potential for worker in injury when the approximately 90-pound alarms need to be removed for periodic maintenance. It could also decrease the incidence of battery failure from elevated temperatures which can exceed 160 degrees F. At the proposed 1-meter elevation the detectors would be surrounded by the cells containing the cascade equipment; therefore, the detectors would be less responsive to a criticality event. The results of this analysis indicate that the detectors could be lowered from their current height of 5 meters to a height of 1 meter and still respond to the minimum accident of concern. This analysis was performed using the MCNP monte carlo code with a source corresponding to a critical system of uranyl fluoride solutions of 1.2, 3.0, and 4.95 weight percent U-235 enrichment. The neutron dose rates were evaluated at positions of 69 meters and 100 meters radially outward from the source at 5 meter and 1 meter heights. All neutron detectors located in the three process buildings are located within 100 meters from any potential criticality. This report details the methodology used for this study, background on the data employed, and a comparison to a similar analysis performed in 1983.

  18. Computation of neutron fluxes in clusters of fuel pins arranged in hexagonal assemblies (2D and 3D)

    SciTech Connect

    Prabha, H.; Marleau, G.

    2012-07-01

    For computations of fluxes, we have used Carvik's method of collision probabilities. This method requires tracking algorithms. An algorithm to compute tracks (in 2D and 3D) has been developed for seven hexagonal geometries with cluster of fuel pins. This has been implemented in the NXT module of the code DRAGON. The flux distribution in cluster of pins has been computed by using this code. For testing the results, they are compared when possible with the EXCELT module of the code DRAGON. Tracks are plotted in the NXT module by using MATLAB, these plots are also presented here. Results are presented with increasing number of lines to show the convergence of these results. We have numerically computed volumes, surface areas and the percentage errors in these computations. These results show that 2D results converge faster than 3D results. The accuracy on the computation of fluxes up to second decimal is achieved with fewer lines. (authors)

  19. Field Dependence of the Magnetic Propagation Vector of the Heavy Fermion Compound CeCu2Ge2 Studied by Neutron Diffraction

    NASA Astrophysics Data System (ADS)

    Loewenhaupt, M.; Geselbracht, P.; Faulhaber, E.; Rotter, M.; Doerr, M.; Schmalzl, K.; Schneidewind, A.

    CeCu2Ge2, the counterpart of the heavy-fermion superconductor CeCu2Si2, exhibits an in-commensurate antiferromagnetically long-range ordered ground state with τ = (0.28 0.28 0.54) below TN = 4.15K. The magnetism is strongly affected by a Kondo screening of the Ce 4f-moments by conduction electrons. The similar energy scale of both, Kondo and exchange interactions, results in a complex magnetic phase diagram and gives rise to potential quantum critical phenomena at very low temperatures. We present elastic neutron diffraction data obtained on a CeCu2Ge2 single crystal employing the cold triple axis spectrometer PANDA at MLZ and the diffractometer D23 at ILL. The field dependence of the magnetic propagation vector was measured at T ≤ 400 mK in the [110]/[001] plane with vertical magnetic fields applied along [1¯10]. We observe a low-field incommensurate magnetic phase AF1, a first order phase transition around 7.8 T with the coexistence of two phases AF1 and AF2 with slightly different propagation vectors, the disappearance of AF1 at 8 T and the existence of AF2 up to 12 T with a possible modification at 10 T. At 12.6 T, yet still well below the value of 26 T of the saturation for magnetic fields in [110] direction, the AF2-type magnetic order is lost and magnetic intensities are not to be found at incommensurate positions in the [110]/[001] plane any more. These new results contradict a previously suggested scenario with a QCP located at 8 T and contribute new information to the B - T phase diagram of CeCu2Ge2 in [110] direction.

  20. Coupled cluster study of spectroscopic constants of ground states of heavy rare gas dimers with spin-orbit interaction

    NASA Astrophysics Data System (ADS)

    Tu, Zhe-Yan; Wang, Wen-Liang; Li, Ren-Zhong; Xia, Cai-Juan; Li, Lian-Bi

    2016-07-01

    The CCSD(T) approach based on two-component relativistic effective core potential with spin-orbit interaction just included in coupled cluster iteration is adopted to study the spectroscopic constants of ground states of Kr2, Xe2 and Rn2 dimers. The spectroscopic constants have significant basis set dependence. Extrapolation to the complete basis set limit provides the most accurate values. The spin-orbit interaction hardly affects the spectroscopic constants of Kr2 and Xe2. However, the equilibrium bond length is shortened about 0.013 Å and the dissociation energy is augmented about 18 cm-1 by the spin-orbit interaction for Rn2 in the complete basis set limit.

  1. Hydrido copper clusters supported by dithiocarbamates: oxidative hydride removal and neutron diffraction analysis of [Cu7(H){S2C(aza-15-crown-5)}6].

    PubMed

    Liao, Ping-Kuei; Fang, Ching-Shiang; Edwards, Alison J; Kahlal, Samia; Saillard, Jean-Yves; Liu, C W

    2012-06-18

    Reactions of Cu(I) salts with Na(S(2)CR) (R = N(n)Pr(2), NEt(2), aza-15-crown-5), and (Bu(4)N)(BH(4)) in an 8:6:1 ratio in CH(3)CN solution at room temperature yield the monocationic hydride-centered octanuclear Cu(I) clusters, [Cu(8)(H){S(2)CR}(6)](PF(6)) (R = N(n)Pr(2), 1(H); NEt(2), 2(H); aza-15-crown-5, 3(H)). Further reactions of [Cu(8)(H){S(2)CR}(6)](PF(6)) with 1 equiv of (Bu(4)N)(BH(4)) produced neutral heptanuclear copper clusters, [Cu(7)(H){S(2)CR}(6)] (R = N(n)Pr(2), 4(H); NEt(2), 5(H); aza-15-crown-5, 6(H)) and clusters 4-6 can also be generated from the reaction of Cu(BF(4))(2), Na(S(2)CR), and (Bu(4)N)(BH(4)) in a 7:6:8 molar ratio in CH(3)CN. Reformation of cationic Cu(I)(8) clusters by adding 1 equiv of Cu(I) salt to the neutral Cu(7) clusters in solution is observed. Intriguingly, the central hydride in [Cu(8)(H){S(2)CN(n)Pr(2)}(6)](PF(6)) can be oxidatively removed as H(2) by Ce(NO(3))(6)(2-) to yield [Cu(II)(S(2)CN(n)Pr(2))(2)] exploiting the redox-tolerant nature of dithiocarbamates. Regeneration of hydride-centered octanuclear copper clusters from the [Cu(II)(S(2)CN(n)Pr(2))(2)] can be achieved by reaction with Cu(I) ions and borohydride. The hydride release and regeneration of Cu(I)(8) was monitored by UV-visible titration experiments. To our knowledge, this is the first time that hydride encapsulated within a copper cluster can be released as H(2) via chemical means. All complexes have been fully characterized by (1)H NMR, FT-IR, UV-vis, and elemental analysis, and molecular structures of 1(H), 2(H), and 6(H) were clearly established by single-crystal X-ray diffraction. Both 1(H) and 2(H) exhibit a tetracapped tetrahedral Cu(8) skeleton, which is inscribed within a S(12) icosahedron constituted by six dialkyl dithiocarbamate ligands in a tetrametallic-tetraconnective (μ(2), μ(2)) bonding mode. The copper framework of 6(H) is a tricapped distorted tetrahedron in which the four-coordinate hydride is demonstrated to occupy the central site by

  2. Heavy particle radiotherapy: prospects and pitfalls

    SciTech Connect

    Faju, M.R.

    1980-01-01

    The use of heavy particles in radiotherapy of tumor volumes is examined. Particles considered are protons, helium ions, heavy ions, negative pions, and fast neutrons. Advantages and disadvantages are discussed. (ACR)

  3. Changes in the structure of nuclei between the magic neutron numbers 50 and 82 as indicated by a rotating-cluster analysis of the energy values of the first 2j excited states of isotopes of cadmium

    SciTech Connect

    Pauling, L.

    1981-09-01

    Values of R, the radius of rotation of the rotating cluster, are calculated from the observed values of the energy of the lowest 2/sup +/ states of the even isotopes of Cd, Sn, and Te with the assumption that the cluster is ..cap alpha.., pb, and ..cap alpha.., respectively. R shows a maximum at approx. N = 58, a minimum at approx. N = 62, and a second maximum at approx. N = 70. The increase to the first maximum is interpreted as resulting from the overcrowding of spherons (alphas and tritons) in the mantle (outer layer) of the nuclei, causing the cluster to change from rotating in the mantle to skimming over its surface; the decrease to the minimum results from the addition of three dineutrons to the core, expanding the mantle and permitting the rotating cluster to begin to drop back into it; and the increase to the second maximum results from the overcrowding of the larger mantle surrounding the core containing the semimagic number 14 of neutrons rather than the magic numbers 8 for N = 50. The decrease after the second maximum results from the further increase in the number of core neutrons to 20, corresponding to the magic number 82. Some additional evidence for the change to an intermediate structure between N = 50 and N = 82 is also discussed.

  4. PREFACE: Nuclear Cluster Conference; Cluster'07

    NASA Astrophysics Data System (ADS)

    Freer, Martin

    2008-05-01

    The Cluster Conference is a long-running conference series dating back to the 1960's, the first being initiated by Wildermuth in Bochum, Germany, in 1969. The most recent meeting was held in Nara, Japan, in 2003, and in 2007 the 9th Cluster Conference was held in Stratford-upon-Avon, UK. As the name suggests the town of Stratford lies upon the River Avon, and shortly before the conference, due to unprecedented rainfall in the area (approximately 10 cm within half a day), lay in the River Avon! Stratford is the birthplace of the `Bard of Avon' William Shakespeare, and this formed an intriguing conference backdrop. The meeting was attended by some 90 delegates and the programme contained 65 70 oral presentations, and was opened by a historical perspective presented by Professor Brink (Oxford) and closed by Professor Horiuchi (RCNP) with an overview of the conference and future perspectives. In between, the conference covered aspects of clustering in exotic nuclei (both neutron and proton-rich), molecular structures in which valence neutrons are exchanged between cluster cores, condensates in nuclei, neutron-clusters, superheavy nuclei, clusters in nuclear astrophysical processes and exotic cluster decays such as 2p and ternary cluster decay. The field of nuclear clustering has become strongly influenced by the physics of radioactive beam facilities (reflected in the programme), and by the excitement that clustering may have an important impact on the structure of nuclei at the neutron drip-line. It was clear that since Nara the field had progressed substantially and that new themes had emerged and others had crystallized. Two particular topics resonated strongly condensates and nuclear molecules. These topics are thus likely to be central in the next cluster conference which will be held in 2011 in the Hungarian city of Debrechen. Martin Freer Participants and Cluster'07

  5. Calculates Thermal Neutron Scattering Kernel.

    1989-11-10

    Version 00 THRUSH computes the thermal neutron scattering kernel by the phonon expansion method for both coherent and incoherent scattering processes. The calculation of the coherent part is suitable only for calculating the scattering kernel for heavy water.

  6. Reexamining cluster radioactivity in trans-lead nuclei with consideration of specific density distributions in daughter nuclei and clusters

    NASA Astrophysics Data System (ADS)

    Qian, Yibin; Ren, Zhongzhou; Ni, Dongdong

    2016-08-01

    We further investigate the cluster emission from heavy nuclei beyond the lead region in the framework of the preformed cluster model. The refined cluster-core potential is constructed by the double-folding integral of the density distributions of the daughter nucleus and the emitted cluster, where the radius or the diffuseness parameter in the Fermi density distribution formula is determined according to the available experimental data on the charge radii and the neutron skin thickness. The Schrödinger equation of the cluster-daughter relative motion is then solved within the outgoing Coulomb wave-function boundary conditions to obtain the decay width. It is found that the present decay width of cluster emitters is clearly enhanced as compared to that in the previous case, which involved the fixed parametrization for the density distributions of daughter nuclei and clusters. Among the whole procedure, the nuclear deformation of clusters is also introduced into the calculations, and the degree of its influence on the final decay half-life is checked to some extent. Moreover, the effect from the bubble density distribution of clusters on the final decay width is carefully discussed by using the central depressed distribution.

  7. Inelastic neutron scattering in valence fluctuation compounds

    SciTech Connect

    Jon M Lawrence

    2011-02-15

    The valence fluctuation compounds are rare earth intermetallics where hybridization of the nearly-localized 4f electrons with the conduction electrons leads to incorporation of the 4f's into the itinerant states. This hybridization slows down the conduction electrons and hence gives them a heavy effective mass, justifying application of the term 'heavy Fermion' (HF) to these materials. During the project period, we grew large single crystals of several such compounds and measured their properties using both standard thermodynamic probes and state-of-the-art inelastic neutron scattering. We obtained three main results. For the intermediate valence compounds CePd{sub 3} and YbAl{sub 3}, we showed that the scattering of neutrons by the fluctuations of the 4f magnetic moment does not have the momentum dependence expected for the itinerant heavy mass state; rather, the scattering is more typical of a localized spin fluctuation. We believe that incoherent scattering localizes the excitation. For the heavy Fermion compound Ce(Ni{sub 0.935}Pd{sub 0.065}){sub 2}Ge{sub 2}, which sits at a T = 0 critical point for transformation into an antiferromagnetic (AF) phase, we showed that the scattering from the AF fluctuations does not exhibit any of the divergences that are expected at a phase transition. We speculate that alloy disorder profoundly suppresses the growth of the fluctuating AF regions, leading to short range clusters rather than regions of infinite size. Finally, we explored the applicability of key concepts used to describe the behavior of rare earth heavy Fermions to uranium based HF compounds where the 5f electrons are itinerant as opposed to localized. We found that scaling laws relating the spin fluctuation energy measured in neutron scattering to the low temperature specific heat and susceptibility are valid for the uranium compounds, once corrections are made for AF fluctuations; however, the degeneracy of the high temperature moment is smaller than expected

  8. METHOD OF PRODUCING NEUTRONS

    DOEpatents

    Imhoff, D.H.; Harker, W.H.

    1964-01-14

    This patent relates to a method of producing neutrons in which there is produced a heated plasma containing heavy hydrogen isotope ions wherein heated ions are injected and confined in an elongated axially symmetric magnetic field having at least one magnetic field gradient region. In accordance with the method herein, the amplitude of the field and gradients are varied at an oscillatory periodic frequency to effect confinement by providing proper ratios of rotational to axial velocity components in the motion of said particles. The energetic neutrons may then be used as in a blanket zone containing a moderator and a source fissionable material to produce heat and thermal neutron fissionable materials. (AEC)

  9. Evaporation Residue Yields in Reactions of Heavy Neutron-Rich Radioactive Ion Beams with 64Ni and 96Zr Targets

    SciTech Connect

    Shapira, Dan; Liang, J Felix; Gross, Carl J; Varner Jr, Robert L; Beene, James R; Stracener, Daniel W; Mueller, Paul Edward; Kolata, Jim J; Roberts, Amy; Loveland, Walter; Vinodkumar, A. M.; Prisbrey, Landon; Sprunger, Peter H; Grzywacz-Jones, Kate L; Caraley, Anne L

    2009-01-01

    As hindrance sets in for the fusion of heavier systems, the effect of large neutron excess in the colliding nuclei on their probability to fuse is still an open question. The detection of evaporation residues (ERs), however, provides indisputable evidence for the fusion (complete and incomplete) in the reaction. We therefore devised a system with which we could measure ERs using low intensity neutron-rich radioactive ion beams with an efficiency close to 100%. We report on measurements of the production of ERs in collisions of {sup 132,134}Sn, {sup 134}Te and {sup 134}Sb ion beams with medium mass, neutron-rich targets. The data taken with {sup 132,134}Sn bombarding a {sup 64}Ni target are compared to available data (ERs and fusion) taken with stable Sn isotopes. Preliminary data on the fusion of {sup 132}Sn with {sup 96}Zr target are also presented.

  10. Spectroscopy of Neutron-rich Nuclei of the A{approx_equal}60 region populated through binary heavy-ion collisions

    SciTech Connect

    Lunardi, S.

    2008-11-11

    Neutron-rich nuclei of the mass A = 60 region (from V to Fe) have been studied through multi-nucleon transfer reactions by bombarding a {sup 238}U target with beams of {sup 64}Ni and {sup 70}Zn. Unambiguous identification of prompt {gamma} rays belonging to each nucleus has been achieved by using the efficient gamma-array CLARA coupled to the large-acceptance magnetic spectrometer PRISMA installed at the Legnaro National Laboratories. With the new data, the existence of the N = 32 sub-shell closure has been corroborated through the study of odd V isotopes, whereas a new region of deformation appears for neutron-rich Fe nuclei close to N = 40. The results obtained for all these nuclei are compared with shell model calculations which reproduces quite well the experimental data also for the most neutron-rich nuclei when excitations from the fp shell into the upper g{sub 9/2} orbital are allowed.

  11. Appearance of light clusters in post-bounce evolution of core-collapse supernovae

    SciTech Connect

    Sumiyoshi, Kohsuke; Roepke, Gerd

    2008-05-15

    We explore the abundance of light clusters in core-collapse supernovae at post-bounce stage in a quantum statistical approach. Adopting the profile of a supernova core from detailed numerical simulations, we study the distribution of light bound clusters up to {alpha} particles (2{<=}A{<=}4) as well as heavy nuclei (A>4) in dense matter at finite temperature. Within the frame of a cluster-mean-field approach, the abundances of light clusters are evaluated accounting for self-energy, Pauli blocking, and effects of continuum correlations. We find that deuterons and tritons, in addition to {sup 3}He and {sup 4}He, appear abundantly in a wide region from the surface of the proto-neutron star to the position of the shock wave. The appearance of light clusters may modify the neutrino emission in the cooling region and the neutrino absorption in the heating region and, thereby, influence the supernova mechanism.

  12. MEASUREMENT OF THE RADIUS OF NEUTRON STARS WITH HIGH SIGNAL-TO-NOISE QUIESCENT LOW-MASS X-RAY BINARIES IN GLOBULAR CLUSTERS

    SciTech Connect

    Guillot, Sebastien; Rutledge, Robert E.; Servillat, Mathieu; Webb, Natalie A. E-mail: rutledge@physics.mcgill.ca

    2013-07-20

    This paper presents the measurement of the neutron star (NS) radius using the thermal spectra from quiescent low-mass X-ray binaries (qLMXBs) inside globular clusters (GCs). Recent observations of NSs have presented evidence that cold ultra dense matter-present in the core of NSs-is best described by ''normal matter'' equations of state (EoSs). Such EoSs predict that the radii of NSs, R{sub NS}, are quasi-constant (within measurement errors, of {approx}10%) for astrophysically relevant masses (M{sub NS}>0.5 M{sub Sun }). The present work adopts this theoretical prediction as an assumption, and uses it to constrain a single R{sub NS} value from five qLMXB targets with available high signal-to-noise X-ray spectroscopic data. Employing a Markov chain Monte-Carlo approach, we produce the marginalized posterior distribution for R{sub NS}, constrained to be the same value for all five NSs in the sample. An effort was made to include all quantifiable sources of uncertainty into the uncertainty of the quoted radius measurement. These include the uncertainties in the distances to the GCs, the uncertainties due to the Galactic absorption in the direction of the GCs, and the possibility of a hard power-law spectral component for count excesses at high photon energy, which are observed in some qLMXBs in the Galactic plane. Using conservative assumptions, we found that the radius, common to the five qLMXBs and constant for a wide range of masses, lies in the low range of possible NS radii, R{sub NS}=9.1{sup +1.3}{sub -1.5} km (90%-confidence). Such a value is consistent with low-R{sub NS} equations of state. We compare this result with previous radius measurements of NSs from various analyses of different types of systems. In addition, we compare the spectral analyses of individual qLMXBs to previous works.

  13. Neutronic Reactor Structure

    DOEpatents

    Vernon, H. C.; Weinberg, A. M.

    1961-05-30

    The neutronic reactor is comprised of a core consisting of natural uranium and heavy water with a K-factor greater than unity. The core is surrounded by a reflector consisting of natural uranium and ordinary water with a Kfactor less than unity. (AEC)

  14. NEUTRONIC REACTOR STRUCTURE

    DOEpatents

    Weinberg, A.M.; Vernon, H.C.

    1961-05-30

    A neutronic reactor is described. It has a core consisting of natural uranium and heavy water and having a K-factor greater than unity which is surrounded by a reflector consisting of natural uranium and ordinary water having a Kfactor less than unity.

  15. Half-life systematics across the N=126 shell closure: role of first-forbidden transitions in the β decay of heavy neutron-rich nuclei.

    PubMed

    Morales, A I; Benlliure, J; Kurtukián-Nieto, T; Schmidt, K-H; Verma, S; Regan, P H; Podolyák, Z; Górska, M; Pietri, S; Kumar, R; Casarejos, E; Al-Dahan, N; Algora, A; Alkhomashi, N; Álvarez-Pol, H; Benzoni, G; Blazhev, A; Boutachkov, P; Bruce, A M; Cáceres, L S; Cullen, I J; Denis Bacelar, A M; Doornenbal, P; Estévez-Aguado, M E; Farrelly, G; Fujita, Y; Garnsworthy, A B; Gelletly, W; Gerl, J; Grebosz, J; Hoischen, R; Kojouharov, I; Kurz, N; Lalkovski, S; Liu, Z; Mihai, C; Molina, F; Mücher, D; Rubio, B; Shaffner, H; Steer, S J; Tamii, A; Tashenov, S; Valiente-Dobón, J J; Walker, P M; Wollersheim, H J; Woods, P J

    2014-07-11

    This Letter reports on a systematic study of β-decay half-lives of neutron-rich nuclei around doubly magic (208)Pb. The lifetimes of the 126-neutron shell isotone (204)Pt and the neighboring (200-202)Ir, (203)Pt, (204)Au are presented together with other 19 half-lives measured during the "stopped beam" campaign of the rare isotope investigations at GSI collaboration. The results constrain the main nuclear theories used in calculations of r-process nucleosynthesis. Predictions based on a statistical macroscopic description of the first-forbidden β strength reveal significant deviations for most of the nuclei with N<126. In contrast, theories including a fully microscopic treatment of allowed and first-forbidden transitions reproduce more satisfactorily the trend in the measured half-lives for the nuclei in this region, where the r-process pathway passes through during β decay back to stability. PMID:25062171

  16. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP-oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution.

    PubMed

    Howard, E I; Guillot, B; Blakeley, M P; Haertlein, M; Moulin, M; Mitschler, A; Cousido-Siah, A; Fadel, F; Valsecchi, W M; Tomizaki, Takashi; Petrova, T; Claudot, J; Podjarny, A

    2016-03-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface. PMID:27006775

  17. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP-oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution.

    PubMed

    Howard, E I; Guillot, B; Blakeley, M P; Haertlein, M; Moulin, M; Mitschler, A; Cousido-Siah, A; Fadel, F; Valsecchi, W M; Tomizaki, Takashi; Petrova, T; Claudot, J; Podjarny, A

    2016-03-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader's quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface.

  18. Measurement of neutron diffraction with compact neutron source RANS

    NASA Astrophysics Data System (ADS)

    Ikeda, Y.; Takamura, M.; Taketani, A.; Sunaga, H.; Otake, Y.; Suzuki, H.; Kumagai, M.; Oba, Y.; Hama, T.

    2016-11-01

    Diffraction is used as a measurement technique for crystal structure. X-rays or electron beam with wavelength that is close to the lattice constant of the crystal is often used for the measurement. They have sensitivity in surface (0.01mm) of heavy metals due to the mean free path for heavy ions. Neutron diffraction has the probe of the internal structure of the heavy metals because it has a longer mean free path than that of the X-rays or the electrons. However, the neutron diffraction measurement is not widely used because large facilities are required in the many neutron sources. RANS (Riken Accelerator-driven Compact Neutron Source) is developed as a neutron source which is usable easily in laboratories and factories. In RANS, fast neutrons are generated by 7MeV protons colliding on a Be target. Some fast neutrons are moderated with polyethylene to thermal neutrons. The thermal neutrons of 10meV which have wavelength of 10nm can be used for the diffraction measurement. In this study, the texture evolution in steels was measured with RANS and the validity of the compact neutron source was proved. The texture of IF steel sheets with the thickness of 1.0mm was measured with 10minutes run. The resolution is 2% and is enough to analyze a evolution in texture due to compression/tensile deformation or a volume fraction of two phases in the steel sample. These results have proven the possibility to use compact neutron source for the analysis of mesoscopic structure of metallic materials.

  19. The Abundances of Neutron-capture Species in the Very Metal-poor Globular Cluster M15: A Uniform Analysis of Red Giant Branch and Red Horizontal Branch Stars

    NASA Astrophysics Data System (ADS)

    Sobeck, Jennifer S.; Kraft, Robert P.; Sneden, Christopher; Preston, George W.; Cowan, John J.; Smith, Graeme H.; Thompson, Ian B.; Shectman, Stephen A.; Burley, Gregory S.

    2011-06-01

    The globular cluster M15 is unique in its display of star-to-star variations in the neutron-capture elements. Comprehensive abundance surveys have been previously conducted for handfuls of M15 red giant branch (RGB) and red horizontal branch (RHB) stars. No attempt has been made to perform a single, self-consistent analysis of these stars, which exhibit a wide range in atmospheric parameters. In the current effort, a new comparative abundance derivation is presented for three RGB and six RHB members of the cluster. The analysis employs an updated version of the line transfer code MOOG, which now appropriately treats coherent, isotropic scattering. The apparent discrepancy in the previously reported values for the metallicity of M15 RGB and RHB stars is addressed and a resolute disparity of Δ(RHB - RGB) ≈ 0.1 dex in the iron abundance was found. The anti-correlative behavior of the light neutron-capture elements (Sr, Y, Zr) is clearly demonstrated with both Ba and Eu, standard markers of the s- and r-process, respectively. No conclusive detection of Pb was made in the RGB targets. Consequently for the M15 cluster, this suggests that the main component of the s-process has made a negligible contribution to those elements normally dominated by this process in solar system material. Additionally for the M15 sample, a large Eu abundance spread is confirmed, which is comparable to that of the halo field at the same metallicity. These abundance results are considered in the discussion of the chemical inhomogeneity and nucleosynthetic history of M15.

  20. Formation and evolution of MnNi clusters in neutron irradiated dilute Fe alloys modelled by a first principle-based AKMC method

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, R.; Becquart, C. S.; Domain, C.; Malerba, L.

    2012-07-01

    An atomistic Monte Carlo model parameterised on electronic structure calculations data has been used to study the formation and evolution under irradiation of solute clusters in Fe-MnNi ternary and Fe-CuMnNi quaternary alloys. Two populations of solute rich clusters have been observed, which can be discriminated by whether or not the solute atoms are associated with self-interstitial clusters. Mn-Ni-rich clusters are observed at a very early stage of the irradiation in both modelled alloys, whereas the quaternary alloys contain also Cu-containing clusters. Mn-Ni-rich clusters nucleate very early via a self-interstitial-driven mechanism, earlier than Cu-rich clusters; the latter, however, which are likely to form via a vacancy-driven mechanism, grow in number much faster than the former, helped by the thermodynamic driving force to Cu precipitation in Fe, thereby becoming dominant in the low dose regime. The kinetics of the number density increase of the two populations is thus significantly different. Finally the main conclusion suggested by this work is that the so-called late blooming phases might as well be neither late, nor phases.

  1. Pre-equilibrium α-particle emission as a probe to study α-clustering in nuclei

    NASA Astrophysics Data System (ADS)

    Fotina, O. V.; Goncharov, S. A.; Eremenko, D. O.; Platonov, S. Yu.; Yuminov, O. A.; Kravchuk, V. L.; Gramegna, F.; Marchi, T.; Cinausero, M.; D'Agostino, M.; Bruno, M.; Baiocco, G.; Morelli, L.; Degerlier, M.; Casini, G.; Barlini, S.; Valdrè, S.; Piantelli, S.; Pasquali, G.; Bracco, A.; Camera, F.; Wieland, O.; Benzoni, G.; Blasi, N.; Giaz, A.; Corsi, A.; Fabris, D.

    2014-03-01

    A theoretical approach was developed to describe secondary particle emission in heavy ion collisions, with special regards to pre-equilibrium α-particle production. The probabilities of neutron, proton and α-particle emission have been evaluated for both the equilibrium and pre-equilibrium stages of the process. Effects due the possible cluster structure of the projectile which has been excited during the collisions have been experimentally evidenced studying the double differential cross sections of p and α-particles emitted in the E=250MeV 16O +116Sn reaction. Calculations within the present model with different clusterization probabilities have been compared to the experimental data.

  2. Review of Non-Neutron and Neutron Nuclear Data, 2004

    SciTech Connect

    Holden, Norman E.

    2005-05-24

    Review articles are in preparation for the 2004 edition of the CRC Handbook of Chemistry and Physics dealing with the evaluation of both non-neutron and neutron nuclear data. Data on the discovery of element 110, Darmstadtium, and element 111 have been officially accepted, while data on element 118 have been withdrawn. Data to be presented include revised values for very short-lived nuclides, long-lived nuclides, and beta-beta decay measurements. There has been a reassessment of the spontaneous fission (sf) half-lives, which distinguishes between sf decay half-lives and cluster decay half-lives, and with cluster-fission decay. New measurements of isotopic abundance values for many elements will be discussed with an emphasis on the minor isotopes of interest for use in neutron activation analysis measurements. Neutron resonance integrals will be discussed emphasizing the differences between the calculated values obtained from the analytical integration over neutron resonances and the measured values in a neutron reactor-spectrum, which does not quite conform to the assumed 1/E neutron energy spectrum. The method used to determine the neutron resonance integral from measurement, using neutron activation analysis, will be discussed.

  3. REVIEW OF NON-NEUTRON AND NEUTRON NUCLEAR DATA, 2004.

    SciTech Connect

    HOLDEN, N.E.

    2004-09-26

    Review articles are in preparation for the 2004 edition of the CRC Handbook of Chemistry and Physics dealing with the evaluation of both non-neutron and neutron nuclear data. Data on the discovery of element 110, Darmstadtium, and element 111 have been officially accepted, while data on element 11 8 have been withdrawn. Data to be presented include revised values for very short-lived nuclides, long-lived nuclides and beta-beta decay measurements. There has been a reassessment of the spontaneous fission (sf) half-lives, which distinguishes between sf decay half-lives and cluster decay half-lives and with cluster-fission decay. New measurements of isotopic abundance values for many elements will be discussed with an emphasis on the minor isotopes of interest for use in neutron activation analysis measurements. Neutron resonance integrals will be discussed emphasizing the differences between the calculated values obtained from the analytical integration over neutron resonances and the measured values in a neutron reactor-spectrum, which does not quite conform to the assumed 1/E neutron energy spectrum. The method used to determine the neutron resonance integral from measurement, using neutron activation analysis, will be discussed.

  4. Is near-``spectroscopic accuracy'' possible for heavy atoms and coupled cluster theory? An investigation of the first ionization potentials of the atoms Ga-Kr

    NASA Astrophysics Data System (ADS)

    DeYonker, Nathan J.; Peterson, Kirk A.

    2013-04-01

    Recent developments in ab initio coupled cluster (CC) theory and correlation consistent basis sets have ushered in an era of unprecedented accuracy when studying the spectroscopy and thermodynamics of molecules containing main group elements. These same developments have recently seen application to heavier inorganic or transition metal-containing species. The present work benchmarks conventional single reference coupled cluster theory (up to full configuration interaction for valence electron correlation and coupled cluster with up to full pentuple excitations (CCSDTQP) for core-valence correlation) and explicitly correlated coupled cluster methods [CC with single, double, and perturbative triple substitutions (CCSD(T)-F12)] for the atomic ionization potentials of the six 4p elements (Ga-Kr), a property with experimental error bars no greater than a few cm-1. When second-order spin orbit coupling effects are included, a composite methodology based on CCSD(T) calculations yielded a mean signed error of just -0.039 kcal mol-1 and a mean unsigned error of 0.043 kcal mol-1. Inclusion of post-CCSD(T) correlation corrections reduced both of these values to -0.008 kcal mol-1 and 0.025 kcal mol-1, respectively, with the latter corresponding to an average error of just 9 cm-1. The maximum signed error in the latter scheme was just -0.043 kcal mol-1 (15 cm-1).

  5. High-resolution neutron and X-ray diffraction room-temperature studies of an H-FABP–oleic acid complex: study of the internal water cluster and ligand binding by a transferred multipolar electron-density distribution

    PubMed Central

    Howard, E. I.; Guillot, B.; Blakeley, M. P.; Haertlein, M.; Moulin, M.; Mitschler, A.; Cousido-Siah, A.; Fadel, F.; Valsecchi, W. M.; Tomizaki, Takashi; Petrova, T.; Claudot, J.; Podjarny, A.

    2016-01-01

    Crystal diffraction data of heart fatty acid binding protein (H-FABP) in complex with oleic acid were measured at room temperature with high-resolution X-ray and neutron protein crystallography (0.98 and 1.90 Å resolution, respectively). These data provided very detailed information about the cluster of water molecules and the bound oleic acid in the H-FABP large internal cavity. The jointly refined X-ray/neutron structure of H-FABP was complemented by a transferred multipolar electron-density distribution using the parameters of the ELMAMII library. The resulting electron density allowed a precise determination of the electrostatic potential in the fatty acid (FA) binding pocket. Bader’s quantum theory of atoms in molecules was then used to study interactions involving the internal water molecules, the FA and the protein. This approach showed H⋯H contacts of the FA with highly conserved hydrophobic residues known to play a role in the stabilization of long-chain FAs in the binding cavity. The determination of water hydrogen (deuterium) positions allowed the analysis of the orientation and electrostatic properties of the water molecules in the very ordered cluster. As a result, a significant alignment of the permanent dipoles of the water molecules with the protein electrostatic field was observed. This can be related to the dielectric properties of hydration layers around proteins, where the shielding of electrostatic interactions depends directly on the rotational degrees of freedom of the water molecules in the interface. PMID:27006775

  6. Relative stability and magic numbers of nuclei deduced from behavior of cluster emission half-lives

    NASA Astrophysics Data System (ADS)

    Ismail, M.; Seif, W. M.; Abdurrahman, A.

    2016-08-01

    We calculated the half-life times (Tc) of the 14C, 20O, 20Ne, and 24Ne cluster emissions from heavy and superheavy nuclei. The variation of Tc with the neutron and proton numbers of daughter nuclei is studied to determine the minima in log10Tc at each neutron number for different daughter isotones. We found that each minimum for a given isotone corresponds to neutron magicity already indicated by other approaches. The proton numbers at neutron magic numbers were found to be also proton magic numbers or differ slightly from them. We arranged the different isotones at each neutron magic number according to their stability in the sense that the more stable daughter isotone corresponds to the lowest value of log10Tc . The magic neutron numbers predicted by the present study are N =126 , 148, 152, 154, 160, 162, 172, 176, 178, 180, 182, 184, and 200. The predicted magic proton numbers are Z =82 , 98, 100 102, 106, 108, 114, and 116. The values of N and Z mentioned above agree with magic numbers deduced in other studies.

  7. Pair correlations in neutron-rich nuclei

    SciTech Connect

    Esbensen, H.

    1995-08-01

    We started a program to study the ground-state properties of heavy, neutron-rich nuclei using the Hartree-Fock-Bogolyubov (HFB) approximation. This appears at present to be the most realistic approach for heavy nuclei that contain many loosely bound valence neutrons. The two-neutron density obtained in this approach can be decomposed into two components, one associated with the mean field and one associated with the pairing field. The latter has a structure that is quite similar to the pair-density obtained by diagonalizing the Hamiltonian for a two-neutron halo, which was studied earlier. This allows comparison of the HFB solutions against numerically exact solutions for two-neutron halos. This work is in progress. We intend to apply the HFB method to predict the ground-state properties of heavier, more neutron-rich nuclei that may be produced at future radioactive beam facilities.

  8. Crystallization of dense neutron matter

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Chitre, S. M.

    1974-01-01

    The equation of state for cold neutron matter at high density is studied in the t-matrix formulation, and it is shown that energetically it is convenient to have neutrons in a crystalline configuration rather than in a liquid state for values of the density exceeding 1600 Tg/cu cm. The study of the mechanical properties indicates that the system is stable against shearing stresses. A solid core in the deep interior of heavy neutron stars appears to offer the most plausible explanation of speed-ups observed in the Vela pulsar.

  9. Detection of Neutrons with Scintillation Counters

    DOE R&D Accomplishments Database

    Hofstadter, R.

    1948-11-01

    Detection of slow neutrons by: detection of single gamma rays following capture by cadmium or mercury; detection of more than one gamma ray by observing coincidences after capture; detection of heavy charged particles after capture in lithium or baron nuclei; possible use of anthracene for counting fast neutrons investigated briefly.

  10. Probing neutron rich matter with parity violation

    NASA Astrophysics Data System (ADS)

    Horowitz, Charles

    2016-03-01

    Many compact and energetic astrophysical systems are made of neutron rich matter. In contrast, most terrestrial nuclei involve approximately symmetric nuclear matter with more equal numbers of neutrons and protons. However, heavy nuclei have a surface region that contains many extra neutrons. Precision measurements of this neutron rich skin can determine properties of neutron rich matter. Parity violating electron scattering provides a uniquely clean probe of neutrons, because the weak charge of a neutron is much larger than that of a proton. We describe first results and future plans for the Jefferson Laboratory experiment PREX that measures the thickness of the neutron skin in 208Pb. Another JLAB experiment CREX will measure the neutron radius of 48Ca and test recent microscopic calculations of this neutron rich 48 nucleon system. Finally, we show how measuring parity violation at multiple momentum transfers can determine not just the neutron radius but the full radial structure of the neutron density in 48Ca. A neutron star is eighteen orders of magnitude larger than a nucleus (km vs fm) but both the star and the neutron rich nuclear skin are made of the same neutrons, with the same strong interactions, and the same equation of state. A large pressure pushes neutrons out against surface tension and gives a thick neutron skin. Therefore, PREX will constrain the equation of state of neutron rich matter and improve predictions for the structure of neutron stars. Supported in part by DOE Grants DE-FG02-87ER40365 (Indiana University) and DE-SC0008808 (NUCLEI SciDAC Collaboration).

  11. Proton Distribution in Heavy Nuclei

    DOE R&D Accomplishments Database

    Johnson, M. H; Teller, E.

    1953-11-13

    It is reasoned that, from considerations connected with beta-decay stability and Coulomb repulsion forces, a neutron excess is developed on the surface of heavy nuclei. Several consequences of this qualitative analysis in nucleon interactions are briefly noted. (K.S.)

  12. ACCELERATOR BASED CONTINUOUS NEUTRON SOURCE.

    SciTech Connect

    SHAPIRO,S.M.; RUGGIERO,A.G.; LUDEWIG,H.

    2003-03-25

    Until the last decade, most neutron experiments have been performed at steady-state, reactor-based sources. Recently, however, pulsed spallation sources have been shown to be very useful in a wide range of neutron studies. A major review of neutron sources in the US was conducted by a committee chaired by Nobel laureate Prof. W. Kohn: ''Neutron Sources for America's Future-BESAC Panel on Neutron Sources 1/93''. This distinguished panel concluded that steady state and pulsed sources are complementary and that the nation has need for both to maintain a balanced neutron research program. The report recommended that both a new reactor and a spallation source be built. This complementarity is recognized worldwide. The conclusion of this report is that a new continuous neutron source is needed for the second decade of the 20 year plan to replace aging US research reactors and close the US neutron gap. it is based on spallation production of neutrons using a high power continuous superconducting linac to generate protons impinging on a heavy metal target. There do not appear to be any major technical challenges to the building of such a facility since a continuous spallation source has been operating in Switzerland for several years.

  13. First principle-based AKMC modelling of the formation and medium-term evolution of point defect and solute-rich clusters in a neutron irradiated complex Fe-CuMnNiSiP alloy representative of reactor pressure vessel steels

    NASA Astrophysics Data System (ADS)

    Ngayam-Happy, R.; Becquart, C. S.; Domain, C.

    2013-09-01

    The formation and medium-term evolution of point defect and solute-rich clusters under neutron irradiation have been modelled in a complex Fe-CuMnNiSiP alloy representative of RPV steels, by means of first principle-based atomistic kinetic Monte Carlo simulations. The results obtained reproduce most features observed in available experimental studies, highlighting the very good agreement between both series. According to simulation, solute-rich clusters form and develop via an induced segregation mechanism on either the vacancy or interstitial clusters, and these point defect clusters are efficiently generated only in cascade debris and not Frenkel pair flux. The results have revealed the existence of two distinct populations of clusters with different characteristic features. Solute-rich clusters in the first group are bound essentially to interstitial clusters and they are enriched in Mn mostly, but also Ni to a lesser extent. Over the low dose regime, their density increases in the alloy as a result of the accumulation of highly stable interstitial clusters. In the second group, the solute-rich clusters are merged with vacancy clusters, and they contain mostly Cu and Si, but also substantial amount of Mn and Ni. The formation of a sub-population of pure solute clusters has been observed, which results from annihilation of the low stable vacancy clusters on sinks. The results indicate finally that the Mn content in clusters is up to 50%, Cu, Si, and Ni sharing the other half in more or less equivalent amounts. This composition has not demonstrated any noticeable modification with increasing dose over irradiation.

  14. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  15. Neutron guide

    DOEpatents

    Greene, Geoffrey L.

    1999-01-01

    A neutron guide in which lengths of cylindrical glass tubing have rectangular glass plates properly dimensioned to allow insertion into the cylindrical glass tubing so that a sealed geometrically precise polygonal cross-section is formed in the cylindrical glass tubing. The neutron guide provides easier alignment between adjacent sections than do the neutron guides of the prior art.

  16. Neutron dosimetry

    DOEpatents

    Quinby, Thomas C.

    1976-07-27

    A method of measuring neutron radiation within a nuclear reactor is provided. A sintered oxide wire is disposed within the reactor and exposed to neutron radiation. The induced radioactivity is measured to provide an indication of the neutron energy and flux within the reactor.

  17. Synergistic assembly of heavy metal clusters and luminescent organic bridging ligands in metal-organic frameworks for highly efficient X-ray scintillation.

    PubMed

    Wang, Cheng; Volotskova, Olga; Lu, Kuangda; Ahmad, Moiz; Sun, Conroy; Xing, Lei; Lin, Wenbin

    2014-04-30

    We have designed two metal-organic frameworks (MOFs) to efficiently convert X-ray to visible-light luminescence. The MOFs are constructed from M6(μ3-O)4(μ3-OH)4(carboxylate)12 (M = Hf or Zr) secondary building units (SBUs) and anthracene-based dicarboxylate bridging ligands. The high atomic number of Zr and Hf in the SBUs serves as effective X-ray antenna by absorbing X-ray photons and converting them to fast electrons through the photoelectric effect. The generated electrons then excite multiple anthracene-based emitters in the MOF through inelastic scattering, leading to efficient generation of detectable photons in the visible spectrum. The MOF materials thus serve as efficient X-ray scintillators via synergistic X-ray absorption by the metal-cluster SBUs and optical emission by the bridging ligands.

  18. Neutron sources: Present practice and future potential

    SciTech Connect

    Cierjacks, S.; Smith, A.B.

    1988-01-01

    The present capability and future potential of accelerator-based monoenergetic and white neutron sources are outlined in the context of fundamental and applied neutron-nuclear research. The neutron energy range extends from thermal to 500 MeV, and the time domain from steady-state to pico-second pulsed sources. Accelerator technology is summarized, including the production of intense light-ion, heavy-ion and electron beams. Target capabilities are discussed with attention to neutron-producing efficiency and power-handling capabilities. The status of underlying neutron-producing reactions is summarized. The present and future use of neutron sources in: fundamental neutron-nuclear research, nuclear data acquisition, materials damage studies, engineering tests, and biomedical applications are discussed. Emphasis is given to current status, near-term advances well within current technology, and to long-range projections. 90 refs., 4 figs.

  19. Neutron sources: present practice and future potential

    SciTech Connect

    Cierjacks, S.; Smith, A.B.

    1988-01-01

    The present capability and future potential of accelerator-based monoenergetic and white neutron sources are outlined in the context of fundamental and applied neutron-nuclear research. The neutron energy range extends from thermal to 500+ MeV, and the time domain from steady-state to pico-second pulsed sources. Accelerator technology is summarized, including the production of intense light-ion, heavy-ion and electron beams. Target capabilities are discussed with attention to neutron-production efficiency and power-handling capabilities. The status of underlying neutron-producing reactions is summarized. The present and future use of neutron sources in: (i) fundamental neutron-nuclear research, (ii) nuclear-data acquisition, (iii) materials-damage studies, (iv) engineering test, and (v) biomedical applications are discussed. Emphasis is given to current status, near-term advances well within current technology, and to long-range projections.

  20. One and two-neutron transfer reactions at REX-ISOLDE

    NASA Astrophysics Data System (ADS)

    Wimmer, Kathrin; T-REX Collaboration

    2011-10-01

    In this contribution we will report on one and two neutron transfer reaction experiments in inverse kinematics at the REX-ISOLDE facility (CERN). Light charged target-like reaction products were detected and identified by the T-REX particle detector while coincident γ-rays were detected by the MINIBALL Germanium detector array. Recent results on (d,p) as well as (t,p) reactions with radioactive beams ranging from 11Be to 78Zn isotopes will be presented. The two-neutron transfer reactions involved for the first time the use of a radioactive tritium target in combination with a radioactive heavy ion beam. Supported by BMBF 06MT238, 06DA9036I, EURONS (No. 506065), and the DFG cluster of excellence Universe.

  1. The Los ALamos Neutron Science Center Hydrogen Moderator System

    NASA Astrophysics Data System (ADS)

    Jarmer, J. J.; Knudson, J. N.

    2006-04-01

    At the Los Alamos Neutron Science Center (LANSCE), spallation neutrons are produced by an 800-MeV proton beam interacting with tungsten targets. Gun-barrel-type penetrations through the heavy concrete and steel shielding that surround the targets collimate neutrons to form neutron beams used for scattering experiments. Two liquid hydrogen moderators of one-liter volume each are positioned adjacent to the neutron-production targets. Some of the neutrons that pass through a moderator interact with or scatter from protons in the hydrogen. The neutron-proton interaction reduces the energy or moderates neutrons to lower energies. Lower energy "moderated" neutrons are the most useful for some neutron scattering experiments. We provide a description of the LANSCE hydrogen-moderator system and its cryogenic performance with proton beams of up to 125 micro-amp average current.

  2. Neutron Skin and Equation of State in Asymmetric Nuclear Matter

    NASA Astrophysics Data System (ADS)

    Yoshida, Satoshi; Sagawa, Hiroyuki

    2005-12-01

    Neutron skin thickness of stable and unstable nuclei are studied by using Skyrme Hartree-Fock (SHF) models and relativistic mean field (RMF) models in relation with the pressure of EOS in neutron matter. We found a clear linear correlation between the neutron skin sizes in heavy nuclei, 132Sn and 208Pb and the pressure of neutron matter in both SHF and RMF, while the correlation is weak in unstable nuclei 32Mg and 44Ar.

  3. Scintillating Fiber Technology for a High Neutron Spectrometer

    NASA Technical Reports Server (NTRS)

    Kuznetsov, Evgeny; Adams, James, Jr.; Christl, Mark; Norwood, Joseph; Watts, John

    2014-01-01

    Develop a compact low-power neutron spectrometer that uniquely identifies neutrons in the mixed radiation field expected on crewed deep-space missions. Secondary neutrons are generated by cosmic rays striking heavy crewed spacecraft as well as lunar and planetary surfaces1,2. It has been shown that secondary neutrons can account for up to 50% if the total dose-equivalent received by the crew.

  4. Phosphatidylinositol 4,5-Bisphosphate Clusters the Cell Adhesion Molecule CD44 and Assembles a Specific CD44-Ezrin Heterocomplex, as Revealed by Small Angle Neutron Scattering

    SciTech Connect

    Khajeh, Jahan Ali; Ju, Jeong Ho; Gupta, Yogesh K.; Stanley, Christopher B.; Do, Changwoo; Heller, William T.; Aggarwal, Aneel K.; Callaway, David J.E.; Bu, Zimei

    2015-01-08

    The cell adhesion molecule CD44 regulates diverse cellular functions, including cell-cell and cell-matrix interaction, cell motility, migration, differentiation, and growth. In cells, CD44 co-localizes with the membrane-cytoskeleton adapter protein Ezrin, which links the CD44 assembled receptor signaling complexes to the cytoskeletal actin and organizes the spatial and temporal localization of signaling events. Here we report that the cytoplasmic tail of CD44 (CD44ct) is largely disordered and adopts an autoinhibited conformation, which prevents CD44ct from binding directly to activated Ezrin in solution. Binding to the signaling lipid phosphatidylinositol 4,5-biphosphlate (PIP2) disrupts autoinhibition in CD44ct, and activates CD44ct to associate with Ezrin. Further, using contrast variation small angle neutron scattering, we show that PIP2 mediates the assembly of a specific hetero-tetramer complex of CD44ct with Ezrin. This study reveals a novel autoregulation mechanism in the cytoplasmic tail of CD44 and the role of PIP2 in mediating the assembly of multimeric CD44ct-Ezrin complexes. We hypothesize that polyvalent electrostatic interactions are responsible for the assembly of multimeric PIP2-CD44-Ezrin complexes.

  5. Phosphatidylinositol 4,5-Bisphosphate Clusters the Cell Adhesion Molecule CD44 and Assembles a Specific CD44-Ezrin Heterocomplex, as Revealed by Small Angle Neutron Scattering

    DOE PAGES

    Khajeh, Jahan Ali; Ju, Jeong Ho; Gupta, Yogesh K.; Stanley, Christopher B.; Do, Changwoo; Heller, William T.; Aggarwal, Aneel K.; Callaway, David J.E.; Bu, Zimei

    2015-01-08

    The cell adhesion molecule CD44 regulates diverse cellular functions, including cell-cell and cell-matrix interaction, cell motility, migration, differentiation, and growth. In cells, CD44 co-localizes with the membrane-cytoskeleton adapter protein Ezrin, which links the CD44 assembled receptor signaling complexes to the cytoskeletal actin and organizes the spatial and temporal localization of signaling events. Here we report that the cytoplasmic tail of CD44 (CD44ct) is largely disordered and adopts an autoinhibited conformation, which prevents CD44ct from binding directly to activated Ezrin in solution. Binding to the signaling lipid phosphatidylinositol 4,5-biphosphlate (PIP2) disrupts autoinhibition in CD44ct, and activates CD44ct to associate with Ezrin.more » Further, using contrast variation small angle neutron scattering, we show that PIP2 mediates the assembly of a specific hetero-tetramer complex of CD44ct with Ezrin. This study reveals a novel autoregulation mechanism in the cytoplasmic tail of CD44 and the role of PIP2 in mediating the assembly of multimeric CD44ct-Ezrin complexes. We hypothesize that polyvalent electrostatic interactions are responsible for the assembly of multimeric PIP2-CD44-Ezrin complexes.« less

  6. THE OPTICAL COLORS OF GIANT ELLIPTICAL GALAXIES AND THEIR METAL-RICH GLOBULAR CLUSTERS INDICATE A BOTTOM-HEAVY INITIAL MASS FUNCTION

    SciTech Connect

    Goudfrooij, Paul; Diederik Kruijssen, J. M. E-mail: kruijssen@mpa-garching.mpg.de

    2013-01-10

    We report a systematic and statistically significant offset between the optical (g - z or B - I) colors of seven massive elliptical galaxies and the mean colors of their associated massive metal-rich globular clusters (GCs) in the sense that the parent galaxies are redder by {approx}0.12-0.20 mag at a given galactocentric distance. However, spectroscopic indices in the blue indicate that the luminosity-weighted ages and metallicities of such galaxies are equal to that of their averaged massive metal-rich GCs at a given galactocentric distance, to within small uncertainties. The observed color differences between the red GC systems and their parent galaxies cannot be explained by the presence of multiple stellar generations in massive metal-rich GCs, as the impact of the latter to the populations' integrated g - z or B - I colors is found to be negligible. However, we show that this paradox can be explained if the stellar initial mass function (IMF) in these massive elliptical galaxies was significantly steeper at subsolar masses than canonical IMFs derived from star counts in the solar neighborhood, with the GC colors having become bluer due to dynamical evolution, causing a significant flattening of the stellar MF of the average surviving GC.

  7. Monte-Carlo Simulations of Heavy Ions Track Structures and Applications

    NASA Technical Reports Server (NTRS)

    Plante, Ianik; Cucinotta, Francia A.

    2013-01-01

    In space, astronauts are exposed to protons, high ]energy heavy (HZE) ions that have a high charge (Z) and energy (E), and secondary radiation, including neutrons and recoil nuclei produced by nuclear reactions in spacecraft walls or in tissue. The astronauts can only be partly shielded from these particles. Therefore, on travelling to Mars, it is estimated that every cell nucleus in an astronaut fs body would be hit by a proton or secondary electron (e.g., electrons of the target atoms ionized by the HZE ion) every few days and by an HZE ion about once a month. The risks related to these heavy ions are not well known and of concern for long duration space exploration missions. Medical ion therapy is another situation where human beings can be irradiated by heavy ions, usually to treat cancer. Heavy ions have a peculiar track structure characterized by high levels of energy ]deposition clustering, especially in near the track ends in the so ]called eBragg peak f region. In radiotherapy, these features of heavy ions can provide an improved dose conformation with respect to photons, also considering that the relative biological effectiveness (RBE) of therapeutic ions in the plateau region before the peak is sufficiently low. Therefore, several proton and carbon ion therapy facilities are under construction at this moment

  8. Nucleosynthesis of heavy elements in the r-process

    NASA Astrophysics Data System (ADS)

    Panov, I. V.

    2016-03-01

    The current state of the problem of heavy-element production in the astrophysical r-process is surveyed. The nucleosynthesis process in the neutron-star-merger scenario, within which the problem of free-neutron source is solved, is considered most comprehensively. A model that describes well the observed abundances of heavy elements is examined. Theoretical approaches used in this model to calculate a number of features of short-lived neutron-rich nuclei are described. The contributions of various fission processes to the production of heavy elements are assessed. The possibility of superheavy-element production in the r-process is demonstrated.

  9. POLARIZED NEUTRONS IN RHIC

    SciTech Connect

    COURANT,E.D.

    1998-04-27

    There does not appear to be any obvious way to accelerate neutrons, polarized or otherwise, to high energies by themselves. To investigate the behavior of polarized neutrons the authors therefore have to obtain them by accelerating them as components of heavier nuclei, and then sorting out the contribution of the neutrons in the analysis of the reactions produced by the heavy ion beams. The best neutron carriers for this purpose are probably {sup 3}He nuclei and deuterons. A polarized deuteron is primarily a combination of a proton and a neutron with their spins pointing in the same direction; in the {sup 3}He nucleus the spins of the two protons are opposite and the net spin (and magnetic moment) is almost the same as that of a free neutron. Polarized ions other than protons may be accelerated, stored and collided in a ring such as RHIC provided the techniques proposed for polarized proton operation can be adapted (or replaced by other strategies) for these ions. To accelerate polarized particles in a ring, one must make provisions for overcoming the depolarizing resonances that occur at certain energies. These resonances arise when the spin tune (ratio of spin precession frequency to orbit frequency) resonates with a component present in the horizontal field. The horizontal field oscillates with the vertical motion of the particles (due to vertical focusing); its frequency spectrum is dominated by the vertical oscillation frequency and its modulation by the periodic structure of the accelerator ring. In addition, the magnet imperfections that distort the closed orbit vertically contain all integral Fourier harmonics of the orbit frequency.

  10. Neutron detector

    DOEpatents

    Stephan, Andrew C.; Jardret; Vincent D.

    2011-04-05

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  11. Neutron detector

    SciTech Connect

    Stephan, Andrew C; Jardret, Vincent D

    2009-04-07

    A neutron detector has a volume of neutron moderating material and a plurality of individual neutron sensing elements dispersed at selected locations throughout the moderator, and particularly arranged so that some of the detecting elements are closer to the surface of the moderator assembly and others are more deeply embedded. The arrangement captures some thermalized neutrons that might otherwise be scattered away from a single, centrally located detector element. Different geometrical arrangements may be used while preserving its fundamental characteristics. Different types of neutron sensing elements may be used, which may operate on any of a number of physical principles to perform the function of sensing a neutron, either by a capture or a scattering reaction, and converting that reaction to a detectable signal. High detection efficiency, an ability to acquire spectral information, and directional sensitivity may be obtained.

  12. Neutron Star Mysteries

    NASA Astrophysics Data System (ADS)

    Mathews, G. J.; Fragile, P. C.; Suh, I.; Wilson, J. R.

    2003-04-01

    Neutron stars provide a unique laboratory in which to explore the nuclear equation of state at high densities. Nevertheless, their interior structure and equation of state have remained a mystery. Recently, a number of advances have been made toward unraveling this mystery. The first direct optical images of a nearby neutron star have been obtained from HST. High quality data for X-ray emission from low-mass X-ray binaries, including observations of nearly coherent oscillations (NCO's) and quasi-periodic oscillations (QPOs) now exist. The existence of a possible absorption feature as well as pulsar light curves and glitches, and studies of soft-gamma repeaters, have all led to significant new constraints on the mass-radius relation and maximum mass of neutron stars. We also discuss how models of supernova explosion dynamics and the associated r-process nucleosynthesis also constrain the nuclear equation of state, along with heavy-ion and monopole resonance data. Recent work on the search for the Friedman-Chandrasekhar-Schutz instability and the effects of internal magnetic fields are also discussed. The overall constraints on the neutron star equation of state are summarized.

  13. Heavy flavors

    SciTech Connect

    Cox, B.; Gilman, F.J.; Gottschalk, T.D.

    1986-11-01

    A range of issues pertaining to heavy flavors at the SSC is examined including heavy flavor production by gluon-gluon fusion and by shower evolution of gluon jets, flavor tagging, reconstruction of Higgs and W bosons, and the study of rare decays and CP violation in the B meson system. A specific detector for doing heavy flavor physics and tuned to this latter study at the SSC, the TASTER, is described. 36 refs., 10 figs.

  14. Heavy ion fusion--Using heavy ions to make electricity

    SciTech Connect

    Celata, C.M.

    2004-03-15

    The idea of using nuclear fusion as a source of commercial electrical power has been pursued worldwide since the 1950s. Two approaches, using magnetic and inertial confinement of the reactants, are under study. This paper describes the difference between the two approaches, and discusses in more detail the heavy-ion-driven inertial fusion concept. A multibeam induction linear accelerator would be used to bring {approx}100 heavy ion beams to a few GeV. The beams would then heat and compress a target of solid D-T. This approach is unique among fusion concepts in its ability to protect the reaction chamber wall from neutrons and debris.

  15. Strong color fields and heavy flavor production

    SciTech Connect

    Bautista, I.; Pajares, C.

    2010-09-15

    The clustering of color sources provides a natural framework for soft partonic interactions producing strong color fields. We study the consequences of these color fields in the production of heavy flavor and the behavior of the nuclear modification factor.

  16. Atmospheric neutrons

    NASA Technical Reports Server (NTRS)

    Preszler, A. M.; Moon, S.; White, R. S.

    1976-01-01

    Additional calibrations of the University of California double-scatter neutron detector and additional analysis corrections lead to slightly changed neutron fluxes. The theoretical angular distributions of Merker (1975) are in general agreement with the reported experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current is in agreement with the experimental values from 10 to 100 MeV. The experimental fluxes obtained agree with those of Kanbach et al. (1974) in the overlap region from 70 to 100 MeV.

  17. Neutron capture reactions at DANCE

    NASA Astrophysics Data System (ADS)

    Bredeweg, T. A.

    2008-05-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4π BaF2 array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (>~100 μg) and/or radioactive (<~100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on 241,243Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio (α = σγ/σf) for 235U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  18. Fission-fusion neutron source

    NASA Astrophysics Data System (ADS)

    Yu, Jinnan; Yu, Gang

    2009-04-01

    In order to meet the requirements of fusion power reactors and nuclear waste treatment, a concept of fission-fusion neutron source is proposed, which consists of a LiD assembly located in the heavy water region of the China Advanced Research Reactor. This assembly of LiD fuel rods will be irradiated with slow neutrons and will produce fusion neutrons in the central hole via the reaction 6Li(n, α). More precisely, tritium ions with a high energy of 2.739 MeV will be produced in LiD by the impinging slow neutrons. The tritium ions will in turn bombard the deuterium ions present in the LiD assembly, which will induce fusion reaction and then the production of 14 MeV neutrons. The fusion reaction rate will increase with the accumulation of tritium in LiD by the reaction between tritium and deuteron recoils produced by the 14 MeV neutrons. When the concentration of tritium reaches 0.5 · 10 22 and the fraction of fusion reactions between tritium and deuteron recoils approaches 1, the 14 MeV neutron flux is doubled and redoubled, an so forth, approaching saturation in which the tritium produced at a time t is exhausted by the fusion reactions to keep constant the tritium concentration in LiD.

  19. Neutron capture reactions at DANCE

    SciTech Connect

    Bredeweg, T. A.

    2008-05-12

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 4{pi} BaF{sub 2} array consisting of 160 active detector elements. The primary purpose of the array is to perform neutron capture cross section measurements on small (> or approx.100 {mu}g) and/or radioactive (< or approx. 100 mCi) species. The measurements made possible with this array will be useful in answering outstanding questions in the areas of national security, threat reduction, nuclear astrophysics, advanced reactor design and accelerator transmutation of waste. Since the commissioning of DANCE we have performed neutron capture cross section measurements on a wide array of medium to heavy mass nuclides. Measurements to date include neutron capture cross sections on {sup 241,243}Am, neutron capture and neutron-induced fission cross sections and capture-to-fission ratio ({alpha} = {sigma}{sub {gamma}}/{sigma}{sub f}) for {sup 235}U using a new fission-tagging detector as well as neutron capture cross sections for several astrophysics branch-point nuclei. Results from several of these measurements will be presented along with a discussion of additional physics information that can be extracted from the DANCE data.

  20. Symbolic clustering

    SciTech Connect

    Reinke, R.E.

    1991-01-01

    Clustering is the problem of finding a good organization for data. Because there are many kinds of clustering problems, and because there are many possible clusterings for any data set, clustering programs use knowledge and assumptions about individual problems to make clustering tractable. Cluster-analysis techniques allow knowledge to be expressed in the choice of a pairwise distance measure and in the choice of clustering algorithm. Conceptual clustering adds knowledge and preferences about cluster descriptions. In this study the author describes symbolic clustering, which adds representation choice to the set of ways a data analyst can use problem-specific knowledge. He develops an informal model for symbolic clustering, and uses it to suggest where and how knowledge can be expressed in clustering. A language for creating symbolic clusters, based on the model, was developed and tested on three real clustering problems. The study concludes with a discussion of the implications of the model and the results for clustering in general.

  1. Further study of α-decay in heavy isotopic chains considering the isospin effect

    NASA Astrophysics Data System (ADS)

    Qian, Yibin; Ren, Zhongzhou

    2016-06-01

    We have enhanced the deformed density-dependent cluster model to improve the quantitative description of α-decay in heavy even-even nuclei with 84≤slant Z≤slant 92. To preliminarily introduce the isospin effect into α-decay, the neutron excess term is added in the establishment of the crucial α-core potential. The proton and neutron density distributions are respectively considered in different parameterized formulas by combining them with available experimental data of both the charge radius and the neutron skin thickness. The calculated α-decay half-lives are found to be in somewhat better agreement with the experimental data as compared with our previous results. Strikingly, it is noted that the relatively large deviation between theory and experiment, along the tail of the isotopic chain, is obviously reduced and smoother. This may indicate the necessity of considering the isospin effect in α-decay, especially for extremely neutron-rich nuclei, which appears to be essential for the extended study of heaviest nuclei as well.

  2. Neutron fluctuations: The importance of being delayed.

    PubMed

    Houchmandzadeh, B; Dumonteil, E; Mazzolo, A; Zoia, A

    2015-11-01

    The neutron population in a nuclear reactor is subject to fluctuations in time and in space due to the competition of diffusion by scattering, births by fission events, and deaths by absorptions. As such, fission chains provide a prototype model for the study of spatial clustering phenomena. In order for the reactor to be operated in stationary conditions at the critical point, the population of prompt neutrons instantaneously emitted at fission must be in equilibrium with the much smaller population of delayed neutrons, emitted after a Poissonian time by nuclear decay of the fissioned nuclei. In this work, we will show that the delayed neutrons, although representing a tiny fraction of the total number of neutrons in the reactor, actually have a key impact on the fluctuations, and their contribution is very effective in quenching the spatial clustering. PMID:26651654

  3. Neutron fluctuations: The importance of being delayed

    NASA Astrophysics Data System (ADS)

    Houchmandzadeh, B.; Dumonteil, E.; Mazzolo, A.; Zoia, A.

    2015-11-01

    The neutron population in a nuclear reactor is subject to fluctuations in time and in space due to the competition of diffusion by scattering, births by fission events, and deaths by absorptions. As such, fission chains provide a prototype model for the study of spatial clustering phenomena. In order for the reactor to be operated in stationary conditions at the critical point, the population of prompt neutrons instantaneously emitted at fission must be in equilibrium with the much smaller population of delayed neutrons, emitted after a Poissonian time by nuclear decay of the fissioned nuclei. In this work, we will show that the delayed neutrons, although representing a tiny fraction of the total number of neutrons in the reactor, actually have a key impact on the fluctuations, and their contribution is very effective in quenching the spatial clustering.

  4. Octupole correlations in the heavy elements

    SciTech Connect

    Chasman, R.R.

    1986-01-01

    The effects of octupole correlations on the nuclear structure of the heavy elements are discussed. The cluster model description of the heavy elements is analyzed. The relevance of 2/sup 6/-pole deformation and fast El transitions to an octupole model is considered. 30 refs., 21 figs., 1 tab.

  5. Accelerator-based neutron source for boron neutron capture therapy (BNCT) and method

    DOEpatents

    Yoon, W.Y.; Jones, J.L.; Nigg, D.W.; Harker, Y.D.

    1999-05-11

    A source for boron neutron capture therapy (BNCT) comprises a body of photoneutron emitter that includes heavy water and is closely surrounded in heat-imparting relationship by target material; one or more electron linear accelerators for supplying electron radiation having energy of substantially 2 to 10 MeV and for impinging such radiation on the target material, whereby photoneutrons are produced and heat is absorbed from the target material by the body of photoneutron emitter. The heavy water is circulated through a cooling arrangement to remove heat. A tank, desirably cylindrical or spherical, contains the heavy water, and a desired number of the electron accelerators circumferentially surround the tank and the target material as preferably made up of thin plates of metallic tungsten. Neutrons generated within the tank are passed through a surrounding region containing neutron filtering and moderating materials and through neutron delimiting structure to produce a beam or beams of epithermal neutrons normally having a minimum flux intensity level of 1.0{times}10{sup 9} neutrons per square centimeter per second. Such beam or beams of epithermal neutrons are passed through gamma ray attenuating material to provide the required epithermal neutrons for BNCT use. 3 figs.

  6. Accelerator-based neutron source for boron neutron capture therapy (BNCT) and method

    DOEpatents

    Yoon, Woo Y.; Jones, James L.; Nigg, David W.; Harker, Yale D.

    1999-01-01

    A source for boron neutron capture therapy (BNCT) comprises a body of photoneutron emitter that includes heavy water and is closely surrounded in heat-imparting relationship by target material; one or more electron linear accelerators for supplying electron radiation having energy of substantially 2 to 10 MeV and for impinging such radiation on the target material, whereby photoneutrons are produced and heat is absorbed from the target material by the body of photoneutron emitter. The heavy water is circulated through a cooling arrangement to remove heat. A tank, desirably cylindrical or spherical, contains the heavy water, and a desired number of the electron accelerators circumferentially surround the tank and the target material as preferably made up of thin plates of metallic tungsten. Neutrons generated within the tank are passed through a surrounding region containing neutron filtering and moderating materials and through neutron delimiting structure to produce a beam or beams of epithermal neutrons normally having a minimum flux intensity level of 1.0.times.10.sup.9 neutrons per square centimeter per second. Such beam or beams of epithermal neutrons are passed through gamma ray attenuating material to provide the required epithermal neutrons for BNCT use.

  7. Neutronic reactor

    DOEpatents

    Wende, Charles W. J.

    1976-08-17

    A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

  8. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Zinn, W.H.; Anderson, H.L.

    1958-09-16

    Means are presenied for increasing the reproduction ratio of a gaphite- moderated neutronic reactor by diminishing the neutron loss due to absorption or capture by gaseous impurities within the reactor. This means comprised of a fluid-tight casing or envelope completely enclosing the reactor and provided with a valve through which the casing, and thereby the reactor, may be evacuated of atmospheric air.

  9. Neutron tubes

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui; Reijonen, Jani

    2008-03-11

    A neutron tube or generator is based on a RF driven plasma ion source having a quartz or other chamber surrounded by an external RF antenna. A deuterium or mixed deuterium/tritium (or even just a tritium) plasma is generated in the chamber and D or D/T (or T) ions are extracted from the plasma. A neutron generating target is positioned so that the ion beam is incident thereon and loads the target. Incident ions cause D-D or D-T (or T-T) reactions which generate neutrons. Various embodiments differ primarily in size of the chamber and position and shape of the neutron generating target. Some neutron generators are small enough for implantation in the body. The target may be at the end of a catheter-like drift tube. The target may have a tapered or conical surface to increase target surface area.

  10. Neutron source

    DOEpatents

    Cason, J.L. Jr.; Shaw, C.B.

    1975-10-21

    A neutron source which is particularly useful for neutron radiography consists of a vessel containing a moderating media of relatively low moderating ratio, a flux trap including a moderating media of relatively high moderating ratio at the center of the vessel, a shell of depleted uranium dioxide surrounding the moderating media of relatively high moderating ratio, a plurality of guide tubes each containing a movable source of neutrons surrounding the flux trap, a neutron shield surrounding one part of each guide tube, and at least one collimator extending from the flux trap to the exterior of the neutron source. The shell of depleted uranium dioxide has a window provided with depleted uranium dioxide shutters for each collimator. Reflectors are provided above and below the flux trap and on the guide tubes away from the flux trap.

  11. Population Synthesis of Double Neutron Stars

    NASA Astrophysics Data System (ADS)

    Tenney, Craig; Lorimer, D.; Bagchi, M.

    2014-01-01

    Globular clusters in our galaxy provide a fertile ground for stars to undergo supernova which leads to the creation of neutron stars. A population synthesis was created to study the population of double neutron stars (DNS) in our Galaxy that originated in globular clusters. The rate of DNS formation is proportional to the cluster's luminosity and the resulting kick from the supernova at birth ejects the DNS from the cluster. Initial conditions are given to the DNS after being ejected and allowed to evolve throughout the galaxy to the present time. With a simulated population of DNS we test to see how many of them are detectable from Earth with radio telescopes. DNS are being used as a way to detect gravitation waves when the two neutron stars spiral into each other. A better constraint on their formation and existence will lead to more accurate predictions for gravitational wave detectors.

  12. Cyclotron-based neutron source for BNCT

    NASA Astrophysics Data System (ADS)

    Mitsumoto, T.; Yajima, S.; Tsutsui, H.; Ogasawara, T.; Fujita, K.; Tanaka, H.; Sakurai, Y.; Maruhashi, A.

    2013-04-01

    Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation & treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutron collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8×109 neutrons/cm2/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with 10B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.

  13. Cyclotron-based neutron source for BNCT

    SciTech Connect

    Mitsumoto, T.; Yajima, S.; Tsutsui, H.; Ogasawara, T.; Fujita, K.; Tanaka, H.; Sakurai, Y.; Maruhashi, A.

    2013-04-19

    Kyoto University Research Reactor Institute (KURRI) and Sumitomo Heavy Industries, Ltd. (SHI) have developed a cyclotron-based neutron source for Boron Neutron Capture Therapy (BNCT). It was installed at KURRI in Osaka prefecture. The neutron source consists of a proton cyclotron named HM-30, a beam transport system and an irradiation and treatment system. In the cyclotron, H- ions are accelerated and extracted as 30 MeV proton beams of 1 mA. The proton beams is transported to the neutron production target made by a beryllium plate. Emitted neutrons are moderated by lead, iron, aluminum and calcium fluoride. The aperture diameter of neutron collimator is in the range from 100 mm to 250 mm. The peak neutron flux in the water phantom is 1.8 Multiplication-Sign 109 neutrons/cm{sup 2}/sec at 20 mm from the surface at 1 mA proton beam. The neutron source have been stably operated for 3 years with 30 kW proton beam. Various pre-clinical tests including animal tests have been done by using the cyclotron-based neutron source with {sup 10}B-p-Borono-phenylalanine. Clinical trials of malignant brain tumors will be started in this year.

  14. Overview of secondary neutron production relevant to shielding inspace

    SciTech Connect

    Heilbronn, L.; Nakamura, T.; Iwata, Y.; Kurosawa, T.; Iwase, H.; Townsend, L.W.

    2004-12-03

    An overview of experimental secondary neutron measurements relevant to space-related activities is presented. Stopping target yields and cross section measurements conducted at particle accelerators using heavy ions with energies >100 MeV per nucleon are discussed.

  15. NEUTRON SOURCE

    DOEpatents

    Bernander, N.K. et al.

    1960-10-18

    An apparatus is described for producing neutrons through target bombardment with deuterons. Deuterium gas is ionized by electron bombardment and the deuteron ions are accelerated through a magnetic field to collimate them into a continuous high intensity beam. The ion beam is directed against a deuteron pervious metal target of substantially the same nnaterial throughout to embed the deuterous therein and react them to produce neutrons. A large quantity of neutrons is produced in this manner due to the increased energy and quantity of ions bombarding the target.

  16. Thermal neutron detection system

    DOEpatents

    Peurrung, Anthony J.; Stromswold, David C.

    2000-01-01

    According to the present invention, a system for measuring a thermal neutron emission from a neutron source, has a reflector/moderator proximate the neutron source that reflects and moderates neutrons from the neutron source. The reflector/moderator further directs thermal neutrons toward an unmoderated thermal neutron detector.

  17. 2013 Review of Neutron and Non-Neutron Nuclear Data

    SciTech Connect

    Holden, N. E.

    2014-05-23

    The results of a review and evaluation of neutron and non-neutron nuclear data published in the scientific literature over the past three years since the ISRD-14 Symposium has been performed and the highlights are presented. Included in the data review are the status of new chemical elements, new measurements of the isotopic composition for many chemical elements and the resulting change in the atomic weight values. New half-life measurements for both short-lived and longlived nuclides, some alpha decay and double beta decay measurements for quasistable nuclides are discussed. The latest evaluation of atomic masses has been published. Data from new measurements on the very heavy (trans-meitnerium) elements are discussed and tabulated. Data on various recent neutron cross section and resonance integral measurements are discussed and tabulated.

  18. 2013 Review of Neutron and Non-Neutron Nuclear Data

    NASA Astrophysics Data System (ADS)

    Holden, N. E.

    2016-02-01

    The results of a review and evaluation of neutron and non-neutron nuclear data published in the scientific literature over the past three years since the ISRD-14 Symposium has been performed and the highlights are presented. Included in the data review are the status of new chemical elements, new measurements of the isotopic composition for many chemical elements and the resulting change in the atomic weight values. New half-life measurements for both short-lived and long-lived nuclides, some alpha decay and double beta decay measurements for quasi-stable nuclides are discussed. The latest evaluation of atomic masses has been published. Data from new measurements on the very heavy (trans-meitnerium) elements are discussed and tabulated. Data on various recent neutron cross section and resonance integral measurements are discussed and tabulated.

  19. Clusterization in Ternary Fission

    NASA Astrophysics Data System (ADS)

    Kamanin, D. V.; Pyatkov, Y. V.

    This lecture notes are devoted to the new kind of ternary decay of low excited heavy nuclei called by us "collinear cluster tri-partition" (CCT) due to the features of the effect observed, namely, decay partners fly away almost collinearly and at least one of them has magic nucleon composition. At the early stage of our work the process of "true ternary fission" (fission of the nucleus into three fragments of comparable masses) was considered to be undiscovered for low excited heavy nuclei. Another possible prototype—three body cluster radioactivity—was also unknown. The most close to the CCT phenomenon, at least cinematically, stands so called "polar emission", but only very light ions (up to isotopes of Be) were observed so far.

  20. CLUSTER CHEMISTRY

    SciTech Connect

    Muetterties, Earl L.

    1980-05-01

    Metal cluster chemistry is one of the most rapidly developing areas of inorganic and organometallic chemistry. Prior to 1960 only a few metal clusters were well characterized. However, shortly after the early development of boron cluster chemistry, the field of metal cluster chemistry began to grow at a very rapid rate and a structural and a qualitative theoretical understanding of clusters came quickly. Analyzed here is the chemistry and the general significance of clusters with particular emphasis on the cluster research within my group. The importance of coordinately unsaturated, very reactive metal clusters is the major subject of discussion.

  1. Super-heavy element research

    NASA Astrophysics Data System (ADS)

    Oganessian, Yu Ts; Utyonkov, V. K.

    2015-02-01

    A review of the discovery and investigation of the ‘island of stability’ of super-heavy nuclei at the separator DGFRS (FLNR, JINR) in the fusion reactions of 48Ca projectiles with target nuclei 238U-249Cf is presented. The synthesis of the heaviest nuclei, their decay properties, and methods of identification are discussed. The role of shell effects in the stability of super-heavy nuclei is demonstrated by comparison of the experimental data and results of theoretical calculations. The radioactive properties of the new nuclei, the isotopes of elements 112-118 as well as of their decay products, give evidence of the significant increase of the stability of the heavy nuclei with rise of their neutron number and approaching magic number N = 184.

  2. NEUTRONIC REACTOR

    DOEpatents

    Wade, E.J.

    1958-09-16

    This patent relates to a reflector means for a neutronic reactor. A reflector comprised of a plurality of vertically movable beryllium control members is provided surrounding the sides of the reactor core. An absorber of fast neutrons comprised of natural uramum surrounds the reflector. An absorber of slow neutrons surrounds the absorber of fast neutrons and is formed of a plurality of beryllium blocks having natural uranium members distributcd therethrough. in addition, a movable body is positioned directly below the core and is comprised of a beryllium reflector and an absorbing member attached to the botiom thereof, the absorbing member containing a substance selected from the goup consisting of natural urantum and Th/sup 232/.

  3. NEUTRONIC REACTOR

    DOEpatents

    Fraas, A.P.; Mills, C.B.

    1961-11-21

    A neutronic reactor in which neutron moderation is achieved primarily in its reflector is described. The reactor structure consists of a cylindrical central "island" of moderator and a spherical moderating reflector spaced therefrom, thereby providing an annular space. An essentially unmoderated liquid fuel is continuously passed through the annular space and undergoes fission while contained therein. The reactor, because of its small size, is particularly adapted for propulsion uses, including the propulsion of aircraft. (AEC)

  4. NEUTRON SOURCES

    DOEpatents

    Richmond, J.L.; Wells, C.E.

    1963-01-15

    A neutron source is obtained without employing any separate beryllia receptacle, as was formerly required. The new method is safer and faster, and affords a source with both improved yield and symmetry of neutron emission. A Be container is used to hold and react with Pu. This container has a thin isolating layer that does not obstruct the desired Pu--Be reaction and obviates procedures previously employed to disassemble and remove a beryllia receptacle. (AEC)

  5. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1958-04-22

    A nuclear reactor for isotope production is described. This reactor is designed to provide a maximum thermal neutron flux in a region adjacent to the periphery of the reactor rather than in the center of the reactor. The core of the reactor is generally centrally located with respect tn a surrounding first reflector, constructed of beryllium. The beryllium reflector is surrounded by a second reflector, constructed of graphite, which, in tune, is surrounded by a conventional thermal shield. Water is circulated through the core and the reflector and functions both as a moderator and a coolant. In order to produce a greatsr maximum thermal neutron flux adjacent to the periphery of the reactor rather than in the core, the reactor is designed so tbat the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the materials in the reflector is approximately twice the ratio of neutron scattering cross section to neutron absorption cross section averaged over all of the material of the core of the reactor.

  6. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  7. The s-process enrichment of the globular clusters M4 and M22

    SciTech Connect

    Shingles, Luke J.; Karakas, Amanda I.; Fishlock, Cherie K.; Yong, David; Da Costa, Gary S.; Marino, Anna F.; Hirschi, Raphael

    2014-11-01

    We investigate the enrichment in elements produced by the slow neutron-capture process (s-process) in the globular clusters M4 (NGC 6121) and M22 (NGC 6656). Stars in M4 have homogeneous abundances of Fe and neutron-capture elements, but the entire cluster is enhanced in s-process elements (Sr, Y, Ba, Pb) relative to other clusters with a similar metallicity. In M22, two stellar groups exhibit different abundances of Fe and s-process elements. By subtracting the mean abundances of s-poor from s-rich stars, we derive s-process residuals or empirical s-process distributions for M4 and M22. We find that the s-process distribution in M22 is more weighted toward the heavy s-peak (Ba, La, Ce) and Pb than M4, which has been enriched mostly with light s-peak elements (Sr, Y, Zr). We construct simple chemical evolution models using yields from massive star models that include rotation, which dramatically increases s-process production at low metallicity. We show that our massive star models with rotation rates of up to 50% of the critical (break-up) velocity and changes to the preferred {sup 17}O(α, γ){sup 21}Ne rate produce insufficient heavy s-elements and Pb to match the empirical distributions. For models that incorporate asymptotic giant branch yields, we find that intermediate-mass yields (with a {sup 22}Ne neutron source) alone do not reproduce the light-to-heavy s-element ratios for M4 and M22, and that a small contribution from models with a {sup 13}C pocket is required. With our assumption that {sup 13}C pockets form for initial masses below a transition range between 3.0 and 3.5 M {sub ☉}, we match the light-to-heavy s-element ratio in the s-process residual of M22 and predict a minimum enrichment timescale of between 240 and 360 Myr. Our predicted value is consistent with the 300 Myr upper limit age difference between the two groups derived from isochrone fitting.

  8. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

    Thomas, David J.; Nolte, Ralf; Gressier, Vincent

    2011-12-01

    The International Committee for Weights and Measures (CIPM) has consultative committees covering various areas of metrology. The Consultative Committee for Ionizing Radiation (CCRI) differs from the others in having three sections: Section (I) deals with radiation dosimetry, Section (II) with radionuclide metrology and Section (III) with neutron metrology. In 2003 a proposal was made to publish special issues of Metrologia covering the work of the three Sections. Section (II) was the first to complete their task, and their special issue was published in 2007, volume 44(4). This was followed in 2009 by the special issue on radiation dosimetry, volume 46(2). The present issue, volume 48(6), completes the trilogy and attempts to explain neutron metrology, the youngest of the three disciplines, the neutron only having been discovered in 1932, to a wider audience and to highlight the relevance and importance of this field. When originally approached with the idea of this special issue, Section (III) immediately saw the value of a publication specifically on neutron metrology. It is a topic area where papers tend to be scattered throughout the literature in journals covering, for example, nuclear instrumentation, radiation protection or radiation measurements in general. Review articles tend to be few. People new to the field often ask for an introduction to the various topics. There are some excellent older textbooks, but these are now becoming obsolete. More experienced workers in specific areas of neutron metrology can find it difficult to know the latest position in related areas. The papers in this issue attempt, without presenting a purely historical outline, to describe the field in a sufficiently logical way to provide the novice with a clear introduction, while being sufficiently up-to-date to provide the more experienced reader with the latest scientific developments in the different topic areas. Neutron radiation fields obviously occur throughout the nuclear

  9. Biomembranes research using thermal and cold neutrons.

    PubMed

    Heberle, F A; Myles, D A A; Katsaras, J

    2015-11-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: "whatever the radiation from Be may be, it has most remarkable properties." Where it concerns hydrogen-rich biological materials, the "most remarkable" property is the neutron's differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. This article describes recent biomembranes research using a variety of neutron scattering techniques. PMID:26241882

  10. Biomembranes research using thermal and cold neutrons.

    PubMed

    Heberle, F A; Myles, D A A; Katsaras, J

    2015-11-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: "whatever the radiation from Be may be, it has most remarkable properties." Where it concerns hydrogen-rich biological materials, the "most remarkable" property is the neutron's differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. This article describes recent biomembranes research using a variety of neutron scattering techniques.

  11. Two neutron correlations in photo-fission

    NASA Astrophysics Data System (ADS)

    Dale, D. S.; Kosinov, O.; Forest, T.; Burggraf, J.; Stave, S.; Warren, G.; Starovoitova, V.

    2016-09-01

    A large body of experimental work has established the strong kinematical correlation between fission fragments and fission neutrons. Here, we report on the progress of investigations of the potential for strong two neutron correlations arising from the nearly back-to-back nature of the two fission fragments that emit these neutrons in the photo-fission process. In initial measurements, a pulsed electron linear accelerator was used to generate bremsstrahlung photons that impinged upon an actinide target, and the energy and opening angle distributions of coincident neutrons were measured using a large acceptance neutron detector array. A planned comprehensive set of measurements of two neutron correlations in the photo-fission of actinides is expected to shed light on several fundamental aspects of the fission process including the multiplicity distributions associated with the light and heavy fission fragments, the nuclear temperatures of the fission fragments, and the mass distribution of the fission fragments as a function of energy released. In addition to these measurements providing important nuclear data, the unique kinematics of fission and the resulting two neutron correlations have the potential to be the basis for a new tool to detect fissionable materials. A key technical challenge of this program arises from the need to perform coincidence measurements with a low duty factor, pulsed electron accelerator. This has motivated the construction of a large acceptance neutron detector array, and the development of data analysis techniques to directly measure uncorrelated two neutron backgrounds.

  12. Experimental Verification of Heavy Ion Irradiation Simulation

    NASA Astrophysics Data System (ADS)

    Zhu, Shengyun; Iwata, T.; Xu, Yongjun; Zheng, Yongnan; Zhou, Dongmei; Zhu, Jiazheng; Wang, Zhiqqiang; Yuan, Daqing; Du, Enpeng; Zuo, Yi

    The heavy ion irradiation simulation of neutron and/or proton irradiation has been verified experimentally by the detailed study of radiation damage in α-Al2O3 irradiated at the equivalent dose by 5.28×1015 cm-285 MeV 19F ions and by 3×1020 cm-2 En≥1MeV neutrons, respectively. The radiation damage created by irradiation was examined by a positron annihilation lifetime technique. The positron annihilation parameters of lifetime and intensity obtained for both irradiations in α-Al2O3 are all in good agreement. This demonstrates that the heavy ion irradiation can well simulate the neutron and/or proton irradiation.

  13. Neutron therapy of cancer

    NASA Technical Reports Server (NTRS)

    Frigerio, N. A.; Nellans, H. N.; Shaw, M. J.

    1969-01-01

    Reports relate applications of neutrons to the problem of cancer therapy. The biochemical and biophysical aspects of fast-neutron therapy, neutron-capture and neutron-conversion therapy with intermediate-range neutrons are presented. Also included is a computer program for neutron-gamma radiobiology.

  14. 2002 REVIEW OF NEUTRON AND NON NEUTRON NUCLEAR DATA.

    SciTech Connect

    HOLDEN,N.E.

    2002-08-18

    Review articles are in preparation for the 2003 edition of the CRC's Handbook of Chemistry and Physics dealing with both non-neutron and neutron nuclear data. Highlights include: withdrawal of the claim for discovery of element 118; new measurements of isotopic abundances have led to changes for many elements; a new set of recommended standards for calibration of {gamma}-ray energies have been published for many nuclides; new half-life measurements reported for very short lived isotopes, many long-lived nuclides and {beta}{beta} decay measurements for quasi-stable nuclides; a new reassessment of spontaneous fission (sf) half-lives for ground state nuclides, distinguishing half-lives from sf decay and cluster decay half-lives and the new cluster-fission decay; charged particle cross sections, (n,p) and (n,{alpha}) measurements for thermal neutrons incident on light nuclides; new thermal (n,{gamma}) cross sections and neutron resonance integrals measured. Details are presented.

  15. NEUTRONIC REACTOR

    DOEpatents

    Hurwitz, H. Jr.; Brooks, H.; Mannal, C.; Payne, J.H.; Luebke, E.A.

    1959-03-24

    A reactor of the heterogeneous, liquid cooled type is described. This reactor is comprised of a central region of a plurality of vertically disposed elongated tubes surrounded by a region of moderator material. The central region is comprised of a central core surrounded by a reflector region which is surrounded by a fast neutron absorber region, which in turn is surrounded by a slow neutron absorber region. Liquid sodium is used as the primary coolant and circulates through the core which contains the fuel elements. Control of the reactor is accomplished by varying the ability of the reflector region to reflect neutrons back into the core of the reactor. For this purpose the reflector is comprised of moderator and control elements having varying effects on reactivity, the control elements being arranged and actuated by groups to give regulation, shim, and safety control.

  16. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Szilard, L.

    1957-09-24

    Reactors of the type employing plates of natural uranium in a moderator are discussed wherein the plates are um-formly disposed in parallel relationship to each other thereby separating the moderator material into distinct and individual layers. Each plate has an uninterrupted sunface area substantially equal to the cross-sectional area of the active portion of the reactor, the particular size of the plates and the volume ratio of moderator to uranium required to sustain a chain reaction being determinable from the known purity of these materials and other characteristics such as the predictable neutron losses due to the formation of radioactive elements of extremely high neutron capture cross section.

  17. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.; Weinberg, A.W.; Young, G.J.

    1958-04-15

    A nuclear reactor which uses uranium in the form of elongated tubes as fuel elements and liquid as a coolant is described. Elongated tubular uranium bodies are vertically disposed in an efficient neutron slowing agent, such as graphite, for example, to form a lattice structure which is disposed between upper and lower coolant tanks. Fluid coolant tubes extend through the uranium bodies and communicate with the upper and lower tanks and serve to convey the coolant through the uranium body. The reactor is also provided with means for circulating the cooling fluid through the coolant tanks and coolant tubes, suitable neutron and gnmma ray shields, and control means.

  18. Delayed neutrons in fission of polonium isotopes

    SciTech Connect

    Ramazanov, R.; Urikbaev, Z.S.; Maksyutenko, B.P.; Ignat'ev, S.V.

    1988-06-01

    A strong difference is found in the relative yields of delayed neutrons in the production of compound nuclei of polonium isotopes in reactions in which bismuth and lead are bombarded by various charged particles. The effect can be partially explained by the different lengths of the ..beta..-decay chains of the light and heavy fission products.

  19. METHOD OF OPERATING A NEUTRONIC REACTOR

    DOEpatents

    Turkevich, A.

    1963-01-22

    This patent relates to one step in a method of operating a neutronic reactor consisting of a slurry of fissionable material in heavy water. Deuterium gas is passed through the slurry to sweep gaseous fission products therefrom and the deuterium is then separated from the gaseous fission products. (AEC)

  20. Martian Neutron Energy Spectrometer (MANES)

    NASA Technical Reports Server (NTRS)

    Maurer, R. H.; Roth, D. R.; Kinnison, J. D.; Goldsten, J. O.; Fainchtein, R.; Badhwar, G.

    2000-01-01

    High energy charged particles of extragalactic, galactic, and solar origin collide with spacecraft structures and planetary atmospheres. These primaries create a number of secondary particles inside the structures or on the surfaces of planets to produce a significant radiation environment. This radiation is a threat to long term inhabitants and travelers for interplanetary missions and produces an increased risk of carcinogenesis, central nervous system (CNS) and DNA damage. Charged particles are readily detected; but, neutrons, being electrically neutral, are much more difficult to monitor. These secondary neutrons are reported to contribute 30-60% of the dose equivalent in the Shuttle and MIR station. The Martian atmosphere has an areal density of 37 g/sq cm primarily of carbon dioxide molecules. This shallow atmosphere presents fewer mean free paths to the bombarding cosmic rays and solar particles. The secondary neutrons present at the surface of Mars will have undergone fewer generations of collisions and have higher energies than at sea level on Earth. Albedo neutrons produced by collisions with the Martian surface material will also contribute to the radiation environment. The increased threat of radiation damage to humans on Mars occurs when neutrons of higher mean energy traverse the thin, dry Martian atmosphere and encounter water in the astronaut's body. Water, being hydrogeneous, efficiently moderates the high energy neutrons thereby slowing them as they penetrate deeply into the body. Consequently, greater radiation doses can be deposited in or near critical organs such as the liver or spleen than is the case on Earth. A second significant threat is the possibility of a high energy heavy ion or neutron causing a DNA double strand break in a single strike.

  1. Formation of super-heavy elements in astrophysical nucleosynthesis

    SciTech Connect

    Zagrebaev, V. I.; Karpov, A. V.; Mishustin, I. N.; Greiner, Walter

    2012-10-20

    The unexplored area of heavy neutron-rich nuclides is extremely important for the understanding of the r process of astrophysical nucleogenesis. For elements with Z>100 only neutron deficient isotopes (located to the left of the stability line) have been synthesized so far. The 'north-east' area of the nuclear map can be reached neither in fusion reactions nor in fragmentation processes. Low energy multi-nucleon transfer reactions are quite promising for the production and study of neutron-rich heavy nuclei including those located at the superheavy (SH) island of stability [1]. The neutron capture process is considered here as an alternative method for the production of SH nuclei. Requirements for the pulsed reactors of the next generation that could be used for the synthesis of long-living neutron rich SH nuclei are formulated. Formation of SH nuclei in supernova explosions is also discussed and the abundance of SH elements in nature is estimated.

  2. Progress Toward Heavy Ion IFE

    SciTech Connect

    Meier, W R; Logan, B G; Waldron, W L; Sabbi, G L; Callahan-Miller, D A; Peterson, P F; Goodin, D T

    2002-01-17

    Successful development of Heavy Ion Fusion (HIF) will require scientific and technology advances in areas of targets, drivers and chambers. Design work on heavy ion targets indicates that high gain (60-130) may be possible with a -3-6 MJ driver depending on the ability to focus the beams to small spot sizes. Significant improvements have been made on key components of heavy ion drivers, including sources, injectors, insulators and ferromagnetic materials for long-pulse induction accelerator cells, solid-state pulsers, and superconducting quadrupole magnets. The leading chamber concept for HIF is the thick-liquid-wall HYLEE-II design, which uses an array of flibe jets to protect chamber structures from x-ray, debris, and neutron damage. Significant progress has been made in demonstrating the ability to create and control the types of flow needed to form the protective liquid blanket. Progress has also been made on neutron shielding for the final focus magnet arrays with predicted lifetimes now exceeding the life of the power plant. Safety analyses have been completed for the HYLEE-II design using state-of-the-art codes. Work also continues on target fabrication and injection for HE. A target injector experiment capable of > 5 Hz operation has been designed and construction will start in 2002. Methods for mass production of hohlraum targets are being evaluated with small-scale experiments and analyses. Progress in these areas will be reviewed.

  3. Pairing gap in the inner crust of neutron stars

    SciTech Connect

    Esbensen, H.; Broglia, R.A.; Vigezzi, E.; Barranco, F.

    1995-08-01

    The pairing gap in the inner crust of a neutron star can be strongly affected by the presence of heavy nuclei. The effect is commonly estimated in a semiclassical description, using the local density approximation. It was found that the nuclear specific heat can become comparable to the electronic specific heat at certain densities and temperatures. The quantitative result depends critically upon the magnitude of the pairing gap. We therefore decided to assess the validity of the semiclassical approach. This is done by solving the quantal BCS pairing gap equation for neutrons that are confined to the Wigner-Seitz cell that surrounds a heavy nucleus. We performed calculations that are based on the Gogny pairing force. They are feasible for realistic densities of neutrons and heavy nuclei that are expected to be found in the inner crust of neutron stars. The results will be compared to the semiclassical predictions. This work is in progress.

  4. Exotic shapes and exotic clusterization

    SciTech Connect

    Cseh, J.; Darai, J.; Algora, A.

    2011-10-28

    The interrelation of the largely elongated nuclear shapes and clusterization is discussed by applying semimicroscopic methods. {sup 36}Ar is considered as a specific example, where recent experimental heavy-ion scattering data seem to justify the theoretical predictions on the hyperdeformed states. Alpha-emitting reactions are also suggested for its population.

  5. Neutronic reactor

    DOEpatents

    Carleton, John T.

    1977-01-25

    A graphite-moderated nuclear reactor includes channels between blocks of graphite and also includes spacer blocks between adjacent channeled blocks with an axis of extension normal to that of the axis of elongation of the channeled blocks to minimize changes in the physical properties of the graphite as a result of prolonged neutron bombardment.

  6. NEUTRONIC REACTORS

    DOEpatents

    Anderson, H.L.

    1958-10-01

    The design of control rods for nuclear reactors are described. In this design the control rod consists essentially of an elongated member constructed in part of a neutron absorbing material and having tube means extending therethrough for conducting a liquid to cool the rod when in use.

  7. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1960-09-27

    A unit assembly is described for a neutronic reactor comprising a tube and plurality of spaced parallel sandwiches in the tube extending lengthwise thereof, each sandwich including a middle plate having a central opening for plutonium and other openings for fertile material at opposite ends of the plate.

  8. Neutron-Resonance Capture Analysis of Materials

    SciTech Connect

    Postma, H.; Bode, P.; Blaauw, M.; Corvi, F.

    1999-11-14

    Epithermal neutron activation analysis is a well-established approach to improve the sensitivity for certain elements by suppressing the activation of interfering elements. If epithermal neutrons of a given energy could be selected, the signal-to-noise ratio might be further improved by taking advantage of resonance capture. This reaction occurs mainly by intermediate and heavy nuclei. Moreover, most of these reactions take place with epithermal or fast neutrons. Intense epithermal neutrons are available as ''white'' beams at accelerator-driven neutron sources. Neutron resonance capture offers interesting analytical opportunities. Low-Z elements have little capture of epithermal neutrons and are thus virtually absent in the time-of-flight spectrum. Relatively large objects can be placed in the neutron beam and analyzed nondestructively. The induced radioactivity is relatively low. If an element has several stable isotopes, each of these isotopes can be recognized by its specific resonances. This would allow for multitracer studies with several isotopically labeled compounds. Different from mass spectrometry, the sample remains intact and can be used for further studies after analysis. Applications may be in the field of archaeology, metallurgy, and certification of reference materials.

  9. Coated semiconductor devices for neutron detection

    DOEpatents

    Klann, Raymond T.; McGregor, Douglas S.

    2002-01-01

    A device for detecting neutrons includes a semi-insulated bulk semiconductor substrate having opposed polished surfaces. A blocking Schottky contact comprised of a series of metals such as Ti, Pt, Au, Ge, Pd, and Ni is formed on a first polished surface of the semiconductor substrate, while a low resistivity ("ohmic") contact comprised of metals such as Au, Ge, and Ni is formed on a second, opposed polished surface of the substrate. In one embodiment, n-type low resistivity pinout contacts comprised of an Au/Ge based eutectic alloy or multi-layered Pd/Ge/Ti/Au are also formed on the opposed polished surfaces and in contact with the Schottky and ohmic contacts. Disposed on the Schottky contact is a neutron reactive film, or coating, for detecting neutrons. The coating is comprised of a hydrogen rich polymer, such as a polyolefin or paraffin; lithium or lithium fluoride; or a heavy metal fissionable material. By varying the coating thickness and electrical settings, neutrons at specific energies can be detected. The coated neutron detector is capable of performing real-time neutron radiography in high gamma fields, digital fast neutron radiography, fissile material identification, and basic neutron detection particularly in high radiation fields.

  10. Single event phenomena in atmospheric neutron environments

    SciTech Connect

    Gossett, C.A.; Hughlock, B.W.; Katoozi, M.; LaRue, G.S. ); Wender, S.A. )

    1993-12-01

    As integrated circuit technology achieves higher density through smaller feature sizes and as the airplane manufacturing industry integrates more sophisticated electronic components into the design of new aircraft, it has become increasingly important to evaluate the contribution of single event effects, primarily Single Event Upset (SEU), to the safety and reliability of commercial aircraft. In contrast to the effects of radiation on electronic systems in space applications for which protons and heavy ions are of major concern, in commercial aircraft applications the interactions of high energy neutrons are the dominant cause of single event effects. These high energy neutrons are produced by the interaction of solar and galactic cosmic rays, principally protons and heavy ions, in the upper atmosphere. This paper will describe direct experimental measurements of neutron-induced Single Event Effect (SEE) rates in commercial high density static random access memories in a neutron environment characteristic of that at commercial airplane altitudes. The first experimental measurements testing current models for neutron-silicon burst generation rates will be presented, as well as measurements of charge collection in silicon test structures as a function of neutron energy. These are the first laboratory SEE and charge collection measurements using a particle beam having a continuum energy spectrum and with a shape nearly identical to that observed during flight.

  11. Cluster headache

    MedlinePlus

    Histamine headache; Headache - histamine; Migrainous neuralgia; Headache - cluster; Horton's headache; Vascular headache - cluster ... be related to the body's sudden release of histamine (chemical in the body released during an allergic ...

  12. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P.; Longhurst, Glen R.; Porter, Douglas L.; Parry, James R.

    2012-07-24

    A conduction cooled neutron absorber may include a metal matrix composite that comprises a metal having a thermal neutron cross-section of at least about 50 barns and a metal having a thermal conductivity of at least about 1 W/cmK. Apparatus for providing a neutron flux having a high fast-to-thermal neutron ratio may include a source of neutrons that produces fast neutrons and thermal neutrons. A neutron absorber positioned adjacent the neutron source absorbs at least some of the thermal neutrons so that a region adjacent the neutron absorber has a fast-to-thermal neutron ratio of at least about 15. A coolant in thermal contact with the neutron absorber removes heat from the neutron absorber.

  13. On the possibility of measuring the gravitational interaction of the neutron with a macroscopic body

    SciTech Connect

    Frank, A. I.

    2009-11-15

    The possibility of experimentally observing the gravitational interaction of the neutron with a macroscopic body is discussed. It is shown that the sensitivity of neutron-optics experiments may be one to two orders of magnitude higher than that which is necessary for observing the gravitational effect. Either the deflection of the neutron trajectory in the gravitational field of a heavy attractor or the gravitation-induced shift of the neutron-wave phase can be recorded experimentally.

  14. Recent Advances in Neutron Physics

    ERIC Educational Resources Information Center

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

    Discusses new studies in neutron physics within the last decade, such as ultracold neutrons, neutron bottles, resonance behavior, subthreshold fission, doubly radiative capture, and neutron stars. (MLH)

  15. Meaningful Clusters

    SciTech Connect

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  16. Abell Clusters

    NASA Astrophysics Data System (ADS)

    Katgert, P.; Murdin, P.

    2000-11-01

    Abell clusters are the most conspicuous groupings of galaxies identified by George Abell on the plates of the first photographic survey made with the SCHMIDT TELESCOPE at Mount Palomar in the 1950s. Sometimes, the term Abell clusters is used as a synonym of nearby, optically selected galaxy clusters....

  17. Neutron reflecting supermirror structure

    DOEpatents

    Wood, J.L.

    1992-12-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. 2 figs.

  18. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources.

  19. Fast neutron environments.

    SciTech Connect

    Buchheit, Thomas Edward; Kotula, Paul Gabriel; Lu, Ping; Brewer, Luke N.; Goods, Steven Howard; Foiles, Stephen Martin; Puskar, Joseph David; Hattar, Khalid Mikhiel; Doyle, Barney Lee; Boyce, Brad Lee; Clark, Blythe G.

    2011-10-01

    The goal of this LDRD project is to develop a rapid first-order experimental procedure for the testing of advanced cladding materials that may be considered for generation IV nuclear reactors. In order to investigate this, a technique was developed to expose the coupons of potential materials to high displacement damage at elevated temperatures to simulate the neutron environment expected in Generation IV reactors. This was completed through a high temperature high-energy heavy-ion implantation. The mechanical properties of the ion irradiated region were tested by either micropillar compression or nanoindentation to determine the local properties, as a function of the implantation dose and exposure temperature. In order to directly compare the microstructural evolution and property degradation from the accelerated testing and classical neutron testing, 316L, 409, and 420 stainless steels were tested. In addition, two sets of diffusion couples from 316L and HT9 stainless steels with various refractory metals. This study has shown that if the ion irradiation size scale is taken into consideration when developing and analyzing the mechanical property data, significant insight into the structural properties of the potential cladding materials can be gained in about a week.

  20. Dose spectra from energetic particles and neutrons

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  1. Double-differential heavy-ion production cross sections.

    PubMed

    Miller, T M; Townsend, L W

    2004-01-01

    Current computational tools used for space or accelerator shielding studies transport energetic heavy ions either using a one-dimensional straight-ahead approximation or by dissociating the nuclei into protons and neutrons and then performing neutron and proton transport using Monte Carlo techniques. Although the heavy secondary particles generally travel close to the beam direction, a proper treatment of the light ions produced in these reactions requires that double-differential cross sections should be utilised. Unfortunately, no fundamental nuclear model capable of serving as an event generator to provide these cross sections for all ions and energies of interest exists currently. Herein, we present a model for producing double-differential heavy-ion production cross sections that uses heavy-ion fragmentation yields produced by the NUCFRG2 fragmentation code coupled with a model of energy degradation in nucleus-nucleus collisions and systematics of momentum distributions to provide energy and angular dependences of the heavy-ion production.

  2. Time-resolved neutron imaging at ANTARES cold neutron beamline

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Dangendorf, V.; Tittelmeier, K.; Schillinger, B.; Schulz, M.; Lerche, M.; Feller, W. B.

    2015-07-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and integrated over multiple cycles. A fast MCP/Timepix neutron counting detector was used to image the water distribution within a model steam engine operating at 10 Hz frequency. Within <10 minutes integration the amount of water was measured as a function of cycle time with a sub-mm spatial resolution, thereby demonstrating the capabilities of time-resolved neutron radiography for the future applications. The neutron spectrum of the ANTARES beamline as well as transmission spectra of a Fe sample were also measured with the Time Of Flight (TOF) technique in combination with a high resolution beam chopper. The energy resolution of our setup was found to be ~ 0.8% at 5 meV and ~ 1.7% at 25 meV. The background level (most likely gammas and epithermal/fast neutrons) of the ANTARES beamline was also measured in our experiments and found to be on the scale of 3% when no filters are installed in the beam. Online supplementary data available from stacks.iop.org/jinst/10

  3. A study of heavy-heavy nuclear reactions. [nuclear research/nuclear particles

    NASA Technical Reports Server (NTRS)

    Khandelwal, G. S.

    1975-01-01

    Calculations are presented for the reaction products in high energy collisions and of the atmospheric transport of particles such as protons, neutrons and other nucleons. The magnetic moments of charmed baryons are examined. Total cross sections which are required for cosmic heavy ion transport and shielding studies are also examined.

  4. Experimental approach to neutron stars

    SciTech Connect

    Leifels, Yvonne

    2014-05-09

    The equation of state (EOS) of nuclear matter is of fundamental importance in many areas of nuclear physics and astrophysics In the laboratory, there are different means to study the nuclearmatter equation of state and its density dependence in particular: nuclear masses, neutron skins, pygmy resonance, and nuclear structure at the drip line give access to nuclear matter properties at densities lower than and at saturation density ρ0. Heavy ion reactions at energies above 0.1 AGeV are the only means to study nuclear matter at densities larger than normal nuclear matter density ρ0. In the beamenergy range of 0.1 to 2A GeV nuclear matter is compressed upto three times ρ0. Access to nuclear matter properties is achieved by simulating nuclear collisions by means of microscopic transport codes, or statistical or hydrodynamicalmodels. Characteristics of heavy-ion collisions are discussed, and experimental observables which allow to constrain nuclear matter properties by comparing experimental results with those of transport codes are presented. Special emphasis will be given to the density dependence of the symmetry energy which is the most relevant connection between neutron stars and heavy ion collisions.

  5. Experimental approach to neutron stars

    NASA Astrophysics Data System (ADS)

    Leifels, Yvonne

    2014-05-01

    The equation of state (EOS) of nuclear matter is of fundamental importance in many areas of nuclear physics and astrophysics In the laboratory, there are different means to study the nuclearmatter equation of state and its density dependence in particular: nuclear masses, neutron skins, pygmy resonance, and nuclear structure at the drip line give access to nuclear matter properties at densities lower than and at saturation density ρ0. Heavy ion reactions at energies above 0.1 AGeV are the only means to study nuclear matter at densities larger than normal nuclear matter density ρ0. In the beamenergy range of 0.1 to 2A GeV nuclear matter is compressed upto three times ρ0. Access to nuclear matter properties is achieved by simulating nuclear collisions by means of microscopic transport codes, or statistical or hydrodynamicalmodels. Characteristics of heavy-ion collisions are discussed, and experimental observables which allow to constrain nuclear matter properties by comparing experimental results with those of transport codes are presented. Special emphasis will be given to the density dependence of the symmetry energy which is the most relevant connection between neutron stars and heavy ion collisions.

  6. Computer analysis of nuclear track emulsion exposed to thermal neutrons and Cf source

    NASA Astrophysics Data System (ADS)

    Mamatkulov, K. Z.; Ambřozová, I.; Artemenkov, D. A.; Bradnova, V.; Kamanin, D. V.; Kattabekov, R. R.; Majling, L.; Marey, A.; Ploc, O.; Rusakova, V. V.; Stanoeva, R.; Turek, K.; Zaitsev, A. A.; Zarubin, P. I.; Zarubina, I. G.

    2016-02-01

    Application of the nuclear track emulsion technique (NTE) in radioactivity and nuclear fission studies is discussed. It is suggested to use a HSP-1000 automated microscope for searching for a collinear cluster tri-partition of heavy nuclei implanted in NTE. Calibrations of α-particles and ion ranges in a novel NTE are carried out. Surface exposures of NTE samples to a Cf-252 source started. Planar events containing fragments and long-range α-particles as well as fragment triples only are studied. Splittings induced by thermal neutrons are studied in boron-enriched emulsion. Use of the image recognition program ”ImageJ” for obtaining characteristics of individual events and for events from the large scan area is presented.

  7. Biomembranes research using thermal and cold neutrons

    DOE PAGES

    Heberle, Frederick A.; Myles, Dean A. A.; Katsaras, John

    2015-08-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: “whatever the radiation from Be may be, it has most remarkable properties.” Where it concerns hydrogen-rich biological materials, the “most remarkable” property is the neutron’s differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, impartingmore » sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. Furthermore, this article describes recent biomembranes research using a variety of neutron scattering techniques.« less

  8. Biomembranes research using thermal and cold neutrons

    SciTech Connect

    Heberle, Frederick A.; Myles, Dean A. A.; Katsaras, John

    2015-08-01

    In 1932 James Chadwick discovered the neutron using a polonium source and a beryllium target (Chadwick, 1932). In a letter to Niels Bohr dated February 24, 1932, Chadwick wrote: “whatever the radiation from Be may be, it has most remarkable properties.” Where it concerns hydrogen-rich biological materials, the “most remarkable” property is the neutron’s differential sensitivity for hydrogen and its isotope deuterium. Such differential sensitivity is unique to neutron scattering, which unlike X-ray scattering, arises from nuclear forces. Consequently, the coherent neutron scattering length can experience a dramatic change in magnitude and phase as a result of resonance scattering, imparting sensitivity to both light and heavy atoms, and in favorable cases to their isotopic variants. Furthermore, this article describes recent biomembranes research using a variety of neutron scattering techniques.

  9. NEUTRONIC REACTORS

    DOEpatents

    Vernon, H.C.

    1959-01-13

    A neutronic reactor of the heterogeneous, fluid cooled tvpe is described. The reactor is comprised of a pressure vessel containing the moderator and a plurality of vertically disposed channels extending in spaced relationship through the moderator. Fissionable fuel material is placed within the channels in spaced relationship thereto to permit circulation of the coolant fluid. Separate means are provided for cooling the moderator and for circulating a fluid coolant thru the channel elements to cool the fuel material.

  10. Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

    NASA Astrophysics Data System (ADS)

    Gozani, Tsahi; King, Michael J.

    2016-01-01

    Extension of the well-established Differential Die Away Analysis (DDAA) into a faster time domain, where more penetrating epithermal neutrons induce fissions, is proposed and demonstrated via simulations and experiments. In the proposed method the fissions stimulated by thermal, epithermal and even higher-energy neutrons are measured after injection of a narrow pulse of high-energy 14 MeV (d,T) or 2.5 MeV (d,D) source neutrons, appropriately moderated. The ability to measure these fissions stems from the inherent correlation of neutron energy and time ("E-T" correlation) during the process of slowing down of high-energy source neutrons in common moderating materials such as hydrogenous compounds (e.g., polyethylene), heavy water, beryllium and graphite. The kinetic behavior following injection of a delta-function-shaped pulse (in time) of 14 MeV neutrons into such moderators is studied employing MCNPX simulations and, when applicable, some simple "one-group" models. These calculations served as a guide for the design of a source moderator which was used in experiments. Qualitative relationships between slowing-down time after the pulse and the prevailing neutron energy are discussed. A laboratory system consisting of a 14 MeV neutron generator, a polyethylene-reflected Be moderator, a liquid scintillator with pulse-shape discrimination (PSD) and a two-parameter E-T data acquisition system was set up to measure prompt neutron and delayed gamma-ray fission signatures in a 19.5% enriched LEU sample. The measured time behavior of thermal and epithermal neutron fission signals agreed well with the detailed simulations. The laboratory system can readily be redesigned and deployed as a mobile inspection system for SNM in, e.g., cars and vans. A strong pulsed neutron generator with narrow pulse (<75 ns) at a reasonably high pulse frequency could make the high-energy neutron induced fission modality a realizable SNM detection technique.

  11. Heavy loads

    SciTech Connect

    Metz, D.

    1982-01-01

    The extreme pressures on the roof and walls of an earth-sheltered residential home are discussed and the need for careful planning is stressed. Pertinent terms are defined. Footings and wall structure (reinforced concrete walls and concrete block walls) are described. Roofing systems are discussed in detail and illustrated: (1) poured-in-place concrete roof slabs; (2) pre-cast concrete planks; and (3) heavy timber roofs. Insulation of earth-sheltered homes is reviewed in terms of using: (1) urethanes; (2) extruded polystyrene; and (3) expanded polystyrene. Advantages, disadvantages, R-factors, costs, and installation are discussed. (MJJ)

  12. Data Clustering

    NASA Astrophysics Data System (ADS)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  13. Boron neutron capture therapy for cancer

    SciTech Connect

    Barth, R.E.; Soloway, A.H. ); Fairchild, R.G. State Univ. of New York, Stony Brook )

    1990-10-01

    Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of these two conditions at the site of a tumor releases intense radiation that can destroy malignant tissues. BNCT is based on the nuclear reaction that occurs when boron 10 is irradiated with an absorbs neutrons. The neutrons that it takes up are called thermal, or slow, neutrons. They are of such low energy that they cause little tissue damage as compared with other forms of radiation such as protons, gamma rays and fast neutrons. When an atom of boron 10 captures a neutron, an unstable isotope, boron 11, forms. The boron 11 instantly fissions, yielding lithium 7 nuclei and energetic alpha particles. These heavy particles, which carry 2.79 million electron volts of energy, are a highly lethal form of radiation. If the treatment proceeds as intended, the destructive effects of the capture reaction would occur primarily in those cancer cells that have accumulated boron 10. Normal cells with low concentrations of boron would be spared.

  14. Biomedical irradiation system for boron neutron capture therapy at the Kyoto University Reactor.

    PubMed

    Kobayashi, T; Kanda, K; Ujeno, Y; Ishida, M R

    1990-01-01

    Physics studies related to radiation source, spectroscopy, beam quality, dosimetry, and biomedical applications using the Kyoto University Reactor Heavy Water Facility are described. Also, described are a Nickel Mirror Neutron Guide Tube and a Super Mirror Neutron Guide Tube that are used both for the measurement of boron concentration in phantom and living tissue and for precise measurements of neutron flux in phantom in the presence of both light and heavy water. Discussed are: (1) spectrum measurements using the time of flight technique, (2) the elimination of gamma rays and fast neutrons from a thermal neutron irradiation field, (3) neutron collimation without producing secondary gamma rays, (4) precise neutron flux measurements, dose estimation, and the measurement of boron concentration in tumor and its periphery using guide tubes, (5) the dose estimation of boron-10 for the first melanoma patient, and (6) special-purpose biological irradiation equipment. Other related subjects are also described.

  15. Heavy Metal Stars

    NASA Astrophysics Data System (ADS)

    2001-08-01

    atomic mass and hence, increasing positive charge of the nuclei, the electric repulsion between the nuclei becomes stronger and stronger. In fact, the fusion process only works up to a certain mass limit, corresponding to the element Iron [2]. All elements that are heavier than Iron cannot be produced via this path. But then, how were those heavy elements we now find on the Earth produced in the first place? From where comes the Zirconium in artificial diamonds, the Barium that colours fireworks, the Tungsten in the filaments in electric bulbs? Which process made the Lead in your car battery? Beyond iron The production of elements heavier than Iron takes place by adding neutrons to the atomic nuclei . These neutral particles do not feel any electrical repulsion from the charged nuclei. They can therefore easily approach them and thereby create heavier nuclei. This is indeed the way the heaviest chemical elements are built up. There are actually two different stellar environments where this process of "neutron capture" can happen. One place where this process occurs is inside very massive stars when they explode as supernovae . In such a dramatic event, the build-up proceeds very rapidly, via the so-called "r-process" ( "r" for rapid ). The AGB stars But not all heavy elements are created in such an explosive way. A second possibility follows a more "peaceful" road. It takes place in rather normal stars, when they burn their Helium towards the end of their lives. In the so-called "s-process" ( "s" for slow ), heavier elements are then produced by a rather gentle addition of neutral neutrons to atomic nuclei. In fact, roughly half of all the elements heavier than Iron are believed to be synthesized by this process during the late evolutionary phases of stars. This process takes place during a specific stage of stellar evolution, known as the "AGB" phase [3]. It occurs just before an old star expels its gaseous envelope into the surrounding interstellar space and sometime

  16. Superheavy Elements Production in High Intensive Neutron Fluxes

    NASA Astrophysics Data System (ADS)

    Lutostansky, Yu. S.; Lyashuk, V. I.; Panov, I. V.

    2013-06-01

    The possibility of superheavy elements production in high intensive neutron fluxes is being studied. A model of the transuranium isotopes production under conditions of pulse nucleosynthesis in a neutron flux with densities of up to ~1025 neutron/cm2 is considered. The pulse process allows us to divide it in time into two stages: the process of multiple neutron captures (with t < 10-6 s) and the subsequent β-decay of neutron-rich nuclei. The modeling of the transuranium yields takes into account the adiabatic character of the process, the probability of delayed fission, and the emission of delayed neutrons. A target with a binary composition of 238U and 239Pu, 248Cm, and 251Cf isotopes is used to predict the yields of heavy and superheavy isotopes.

  17. Neutron Scattering Studies of Cement

    NASA Astrophysics Data System (ADS)

    Allen, Andrew

    2010-03-01

    Despite more than a century of research, basic questions remain regarding both the internal structure and the role of water in Ordinary Portland cement (OPC) concrete, the world's most widely used manufactured material. Most such questions concern the primary hydration product and strength-building phase of OPC paste, the calcium silicate hydrate (C-S-H) gel. When cement and water are mixed, this phase precipitates as clusters of nanoscale (nearly amorphous) colloidal particles with an associated water-filled inter-particle pore system. Most attempts to characterize the C-S-H gel and the behavior of the associated water involve drying or other processes that, themselves, change the bound water content within and around the gel. Neutron scattering methods do not suffer from this disadvantage. Furthermore, the neutron isotope effect and the neutron's sensitivity to molecular motion have enabled considerable progress to be made in recent years by: (i) determining the C-S-H composition, density and gel structure in small-angle neutron scattering (SANS) H/D contrast variation studies; (ii) elucidating the changing state of water within cement as hydration progresses using quasielastic neutron scattering (QENS); and (iii) measuring the production and consumption of nanoscale calcium hydroxide (CH), a by-product of cement hydration that co-exists with the C-S-H gel, using inelastic neutron scattering (INS). These experiments have provided new insights into the physics and chemistry of cement hydration, and have implications for the design of new concretes with pozzolanic cement additions that are intended to address environmental concerns and sustainability issues.

  18. Heavy Stars Thrive among Heavy Elements

    NASA Astrophysics Data System (ADS)

    2002-08-01

    VLT Observes Wolf-Rayet Stars in Virgo Cluster Galaxies [1] Summary Do very massive stars form in metal-rich regions of the Universe and in the nuclei of galaxies ? Or does "heavy element poisoning" stop stellar growth at an early stage, before young stars reach the "heavyweight class"? What may at the first glance appear as a question for specialists actually has profound implications for our understanding of the evolution of galaxies, those systems of billions of stars - the main building blocks of the Universe. With an enormous output of electromagnetic radiation and energetic elementary particles, massive stars exert a decisive influence on the surrounding (interstellar) gas and dust clouds . They also eject large amounts of processed elements, thereby participating in the gradual build-up of the many elements we see today. Thus the presence or absence of such stars at the centres of galaxies can significantly change the overall development of those regions and hence, presumably, that of the entire galaxy. A team of European astronomers [2] has now directly observed the presence of so-called Wolf-Rayet stars (born with masses of 60 - 90 times that of the Sun or more) within metal-rich regions in some galaxies in the Virgo cluster, some 50 million light-years away. This is the first unambiguous detection of such massive stellar objects in metal-rich regions . PR Photo 20a/02 : H II regions in the Virgo cluster galaxy NGC 4254 . PR Photo 20b/02 : Multi-object-slit observation of galaxy NGC 4303 . PR Photo 20c/02 : Spectrum of H II region in NGC 4254 with Wolf-Rayet signatures. Production of heavy elements in the Universe Most scientists agree that the Universe in which we live underwent a dramatic event, known as the Big Bang , approximately 15,000 million years ago. During the early moments, elementary particles were formed which after some time united into more complex nuclei and in turn resulted in the production of hydrogen and helium atoms and their isotopes

  19. NEUTRON COUNTER

    DOEpatents

    Curtis, C.D.; Carlson, R.L.; Tubinis, M.P.

    1958-07-29

    An ionization chamber instrument is described for cylindrical electrodes with an ionizing gag filling the channber. The inner electrode is held in place by a hermetic insulating seal at one end of the outer electrode, the other end of the outer electrode being closed by a gas filling tube. The outer surface of the inner electrode is coated with an active material which is responsive to neutron bombardment, such as uranium235 or boron-10, to produce ionizing radiations in the gas. The transverse cross sectional area of the inner electrode is small in relation to that of the channber whereby substantially all of the radiations are directed toward the outer electrode.

  20. NEUTRON SOURCE

    DOEpatents

    Reardon, W.A.; Lennox, D.H.; Nobles, R.G.

    1959-01-13

    A neutron source of the antimony--beryllium type is presented. The source is comprised of a solid mass of beryllium having a cylindrical recess extending therein and a cylinder containing antimony-124 slidably disposed within the cylindrical recess. The antimony cylinder is encased in aluminum. A berylliunn plug is removably inserted in the open end of the cylindrical recess to completely enclose the antimony cylinder in bsryllium. The plug and antimony cylinder are each provided with a stud on their upper ends to facilitate handling remotely.

  1. Neutron capture rates on radioactive nuclides - DANCE

    NASA Astrophysics Data System (ADS)

    Reifarth, R.; Agvaanluvsan, U.; Alpizar-Vicente, A.; Bredeweg, T. A.; Esch, E.-I.; Greife, U.; Haight, R. C.; Hatarik, R.; Herwig, F.; O'Donnell, J. M.; Rundberg, R. S.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.

    2006-10-01

    The nucleosynthesis of the elements including their stellar sites is one of the most interesting nuclear physics challenges. Information on reaction rates for neutron induced reactions have a direct impact on existing stellar models. Except for the stable isotopes, very few neutron-induced reactions in the energy range of interest have been measured to date. DANCE measurements on stable and unstable isotopes can provide many of the missing key reactions that are needed to understand the nucleosynthesis of the heavy elements, which is illustrated at the example of the 151Sm(n,γ) reaction.

  2. ASTROPHYSICS: Neutron Stars Imply Relativity's a Drag.

    PubMed

    Schilling, G

    2000-09-01

    A new finding, based on x-rays from distant neutron stars, could be the first clear evidence of a weird relativistic effect called frame dragging, in which a heavy chunk of spinning matter wrenches the space-time around it like an eggbeater. Using data from NASA's Rossi X-ray Timing Explorer, three astronomers in Amsterdam found circumstantial evidence for frame dragging in the flickering of three neutron stars in binary systems. They announced their results in the 1 September issue of The Astrophysical Journal. PMID:17839511

  3. Exploring Heavy Drinking Patterns Among Black and White Young Adults

    PubMed Central

    Klima, Tali; Skinner, Martie L; Haggerty, Kevin P; Crutchfield, Robert D; Catalano, Richard F

    2014-01-01

    Objective: This investigation examined patterns of heavy drinking among Black and White young adults from a person-centered perspective and linked family and individual factors in adolescence to young adult drinking patterns. Method: The analysis focuses on 331 10th-grade students (168 Whites, 163 Blacks; 51% males) who were followed into young adulthood (ages 20 and 22). Cluster analyses using heavy episodic drinking, drunkenness, and alcohol problems in young adulthood resulted in groups of drinkers with different patterns. Groups were examined across and within race. Associations between young adult drinking groups and adolescent family and individual factors were tested. Results: Groups followed well-established race differences, with Whites clustering into frequent drinking groups more than Blacks, and Blacks clustering into non–heavy drinking groups more than Whites. Further, Black heavy drinkers reported fewer alcohol problems than White counterparts. Parental monitoring, consistent discipline, ethnic identity, and delinquency were associated with adult heavy episodic drinking groups for both races. Monitoring and delinquency, along with parental norms, were associated with drunkenness groups for both races. However, race differences were observed for drunkenness clusters such that attachment was predictive for White clusters, and parental guidelines and discipline were predictive for Black clusters. Conclusions: Large race differences in heavy drinking at young adulthood were confirmed. Family dynamics in 10th grade were identified as important for the development of different drinking patterns in the early 20s, when many individuals have left home, which suggests a key target for substance use prevention programs. PMID:25208202

  4. Neutron transport study of a beam port based dynamic neutron radiography facility

    NASA Astrophysics Data System (ADS)

    Khaial, Anas M.

    -Carlo simulations (using MCNP-4B code) are conducted to confirm the neutron parameters along the beam path and at the imaging plane. Good agreement between the analytical and the numerical values for the thermal neutron flux at the imaging plane to within 5% has been achieved. The MCNP simulations show that neutron back scattering, due to the presence of the back-wall biological shielding and the beam catcher, have an insignificant effect on the thermal neutron flux at the imaging plane, however, the epithermal and fast neutron fluxes have increased by 4-11%. Experimental results show that the thermal neutron flux is nearly uniform over an imaging area of 20.0-cm diameter. The thermal neutron flux ranges from 1.0x107 -- 1.26x107 n/cm 2-s at a reactor operating power of 3.0 MW. The measured value for the neutron-to-gamma ratio is 6.0x105 n/cm2-muSv and the Cadmium-ratio is observed to be 1.22. These values promote real-time neutron radiography with relatively high neutron attenuating materials such as light water and high-speed neutron radiography with relatively low neutron attenuating materials such as heavy water and Freon type fluids with a minimal contrast degradation resulting from non-thermal neutron content of the beam. A dynamic neutron radiography system has been developed and modified to obtain less neutron damage to the low-light level video camera. The system is used to visualize air-water two-phase flow in a natural-circulation loop to examine the dynamic capabilities of the radiography facility. Measurements of bubble velocity, void fraction, and phase distribution are successfully made. Single frames (˜33 ms) of neutron images were captured using the dynamic neutron radiography system for air-water two-phase flow. The system was able to resolve single bubbles interfaces with an image spatial resolution of approximately 0.44 mm. Thermal neutron detectors are placed at the periphery of the neutron beam to detect neutrons scattered by a non-flowing two-phase object

  5. PRIMORDIAL r-PROCESS DISPERSION IN METAL-POOR GLOBULAR CLUSTERS

    SciTech Connect

    Roederer, Ian U.

    2011-05-01

    Heavy elements, those produced by neutron-capture reactions, have traditionally shown no star-to-star dispersion in all but a handful of metal-poor globular clusters (GCs). Recent detections of low [Pb/Eu] ratios or upper limits in several metal-poor GCs indicate that the heavy elements in these GCs were produced exclusively by an r-process. Re-examining GC heavy element abundances from the literature, we find unmistakable correlations between the [La/Fe] and [Eu/Fe] ratios in four metal-poor GCs (M5, M15, M92, and NGC 3201), only two of which were known previously. This indicates that the total r-process abundances vary from star to star (by factors of 2-6) relative to Fe within each GC. We also identify potential dispersion in two other GCs (M3 and M13). Several GCs (M12, M80, and NGC 6752) show no evidence of r-process dispersion. The r-process dispersion is not correlated with the well-known light element dispersion, indicating that it was present in the gas throughout the duration of star formation. The observations available at present suggest that star-to-star r-process dispersion within metal-poor GCs may be a common but not ubiquitous phenomenon that is neither predicted by nor accounted for in current models of GC formation and evolution.

  6. Heavy Equipment. Trade and Industrial Education Trade Preparatory Training Guide.

    ERIC Educational Resources Information Center

    Nebraska State Dept. of Education, Lincoln. Div. of Vocational Education.

    One of a series of curriculum guides prepared for the building occupations cluster of the construction/fabrication occupational group, this guide identifies the essentials of the heavy equipment trade as recommended by the successful heavy equipment operator. An instructional program based upon the implementation of the guide is expected to…

  7. Neutron capture measurements for nuclear astrophysics

    NASA Astrophysics Data System (ADS)

    Reifarth, Rene

    2005-04-01

    Almost all of the heavy elements are produced via neutron capture reactions in a multitude of stellar production sites. The predictive power of the underlying stellar models is currently limited because they contain poorly constrained physics components such as convection, rotation or magnetic fields. Neutron captures measurements on heavy radioactive isotopes provide a unique opportunity to largely improve these physics components, and thereby address important questions of nuclear astrophysics. Such species are branch-points in the otherwise uniquely defined path of subsequent n-captures along the s-process path in the valley of stability. These branch points reveal themselves through unmistakable signatures recovered from pre-solar meteoritic grains that originate in individual element producing stars. Measurements on radioactive isotopes for neutron energies in the keV region represent a stringent challenge for further improvements of experimental techniques. This holds true for the neutron sources, the detection systems and the technology to handle radioactive material. Though the activation method or accelerator mass spectroscopy of the reaction products could be applied in a limited number of cases, Experimental facilities like DANCE at LANL, USA and n-TOF at CERN, Switzerland are addressing the need for such measurements on the basis of the more universal method of detecting the prompt capture gamma-rays, which is required for the application of neutron time-of-flight (TOF) techniques. With a strongly optimized neutron facility at the Rare Isotope Accelerator (RIA) isotopes with half-lives down to tens of days could be investigated, while present facilities require half-lives of a few hundred days. Recent neutron capture experiments on radioactive isotopes with relevance for nuclear astrophysics and possibilities for future experimental setups will be discussed during the talk.

  8. Recent applications of the Boltzmann master equation to heavy ion precompound decay phenomena

    SciTech Connect

    Blann, M.; Remington, B.A.

    1988-06-01

    The Boltzmann master equation (BME) is described and used as a tool to interpret preequilibrium neutron emission from heavy ion collisions gated on evaporation residue or fission fragments. The same approach is used to interpret neutron spectra gated on deep inelastic and quasi-elastic heavy ion collisions. Less successful applications of BME to proton inclusive data with 40 MeV/u incident /sup 12/C ions are presented, and improvements required in the exciton injection term are discussed.

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

    USGS Publications Warehouse

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

    1966-01-01

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

  10. Relativistic simulations of eccentric binary neutron star mergers: One-arm spiral instability and effects of neutron star spin

    NASA Astrophysics Data System (ADS)

    East, William E.; Paschalidis, Vasileios; Pretorius, Frans; Shapiro, Stuart L.

    2016-01-01

    We perform general-relativistic hydrodynamical simulations of dynamical capture binary neutron star mergers, emphasizing the role played by the neutron star spin. Dynamical capture mergers may take place in globular clusters, as well as other dense stellar systems, where most neutron stars have large spins. We find significant variability in the merger outcome as a function of initial neutron star spin. For cases where the spin is aligned with the orbital angular momentum, the additional centrifugal support in the remnant hypermassive neutron star can prevent the prompt collapse to a black hole, while for antialigned cases the decreased total angular momentum can facilitate the collapse to a black hole. We show that even moderate spins can significantly increase the amount of ejected material, including the amount unbound with velocities greater than half the speed of light, leading to brighter electromagnetic signatures associated with kilonovae and interaction of the ejecta with the interstellar medium. Furthermore, we find that the initial neutron star spin can strongly affect the already rich phenomenology in the postmerger gravitational wave signatures that arise from the oscillation modes of the hypermassive neutron star. In several of our simulations, the resulting hypermassive neutron star develops the one-arm (m =1 ) spiral instability, the most pronounced cases being those with small but non-negligible neutron star spins. For long-lived hypermassive neutron stars, the presence of this instability leads to improved prospects for detecting these events through gravitational waves, and thus may give information about the neutron star equation of state.

  11. Neutron matter, symmetry energy and neutron stars

    SciTech Connect

    Stefano, Gandolfi; Steiner, Andrew W

    2016-01-01

    Recent progress in quantum Monte Carlo with modern nucleon-nucleon interactions have enabled the successful description of properties of light nuclei and neutron-rich matter. Of particular interest is the nuclear symmetry energy, the energy cost of creating an isospin asymmetry, and its connection to the structure of neutron stars. Combining these advances with recent observations of neutron star masses and radii gives insight into the equation of state of neutron-rich matter near and above the saturation density. In particular, neutron star radius measurements constrain the derivative of the symmetry energy.

  12. Quintuplet Cluster

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Penetrating 25,000 light-years of obscuring dust and myriad stars, NASA's Hubble Space Telescope has provided the clearest view yet of one of the largest young clusters of stars inside our Milky Way galaxy, located less than 100 light-years from the very center of the Galaxy. Having the equivalent mass greater than 10,000 stars like our sun, the monster cluster is ten times larger than typical young star clusters scattered throughout our Milky Way. It is destined to be ripped apart in just a few million years by gravitational tidal forces in the galaxy's core. But in its brief lifetime it shines more brightly than any other star cluster in the Galaxy. Quintuplet Cluster is 4 million years old. It has stars on the verge of blowing up as supernovae. It is the home of the brightest star seen in the galaxy, called the Pistol star. This image was taken in infrared light by Hubble's NICMOS camera in September 1997. The false colors correspond to infrared wavelengths. The galactic center stars are white, the red stars are enshrouded in dust or behind dust, and the blue stars are foreground stars between us and the Milky Way's center. The cluster is hidden from direct view behind black dust clouds in the constellation Sagittarius. If the cluster could be seen from earth it would appear to the naked eye as a 3rd magnitude star, 1/6th of a full moon's diameter apart.

  13. System for studying a sample of material using a heavy ion induced mass spectrometer source

    DOEpatents

    Fries, D.P.; Browning, J.F.

    1998-07-21

    A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high (n,f) reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu. 3 figs.

  14. Method for studying a sample of material using a heavy ion induced mass spectrometer source

    DOEpatents

    Fries, D.P.; Browning, J.F.

    1999-02-16

    A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu. 3 figs.

  15. Method for studying a sample of material using a heavy ion induced mass spectrometer source

    DOEpatents

    Fries, David P.; Browning, James F.

    1999-01-01

    A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

  16. System for studying a sample of material using a heavy ion induced mass spectrometer source

    DOEpatents

    Fries, David P.; Browning, James F.

    1998-01-01

    A heavy ion generator is used with a plasma desorption mass spectrometer to provide an appropriate neutron flux in the direction of a fissionable material in order to desorb and ionize large molecules from the material for mass analysis. The heavy ion generator comprises a fissionable material having a high n,f reaction cross section. The heavy ion generator also comprises a pulsed neutron generator that is used to bombard the fissionable material with pulses of neutrons, thereby causing heavy ions to be emitted from the fissionable material. These heavy ions impinge on a material, thereby causing ions to desorb off that material. The ions desorbed off the material pass through a time-of-flight mass analyzer, wherein ions can be measured with masses greater than 25,000 amu.

  17. Neutron density profile in the lunar subsurface produced by galactic cosmic rays

    NASA Astrophysics Data System (ADS)

    Ota, Shuya; Sihver, Lembit; Kobayashi, Shingo; Hasebe, Nobuyuki

    Neutron production by galactic cosmic rays (GCR) in the lunar subsurface is very important when performing lunar and planetary nuclear spectroscopy and space dosimetry. Further im-provements to estimate the production with increased accuracy is therefore required. GCR, which is a main contributor to the neutron production in the lunar subsurface, consists of not only protons but also of heavy components such as He, C, N, O, and Fe. Because of that, it is important to precisely estimate the neutron production from such components for the lunar spectroscopy and space dosimetry. Therefore, the neutron production from GCR particles in-cluding heavy components in the lunar subsurface was simulated with the Particle and Heavy ion Transport code System (PHITS), using several heavy ion interaction models. This work presents PHITS simulations of the neutron density as a function of depth (neutron density profile) in the lunar subsurface and the results are compared with experimental data obtained by Apollo 17 Lunar Neutron Probe Experiment (LNPE). From our previous study, it has been found that the accuracy of the proton-induced neutron production models is the most influen-tial factor when performing precise calculations of neutron production in the lunar subsurface. Therefore, a benchmarking of proton-induced neutron production models against experimental data was performed to estimate and improve the precision of the calculations. It was found that the calculated neutron production using the best model of Cugnon Old (E < 3 GeV) and JAM (E > 3 GeV) gave up to 30% higher values than experimental results. Therefore, a high energy nuclear data file (JENDL-HE) was used instead of the Cugnon Old model at the energies below 3 GeV. Then, the calculated neutron density profile successfully reproduced the experimental data from LNPE within experimental errors of 15% (measurement) + 30% (systematic). In this presentation, we summarize and discuss our calculated results of neutron

  18. 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.

  19. 2010 Review of neutron and non-neutron nuclear data

    SciTech Connect

    Holden, N.E.

    2011-07-01

    The results of a review and evaluation of neutron and non-neutron nuclear data published in the scientific literature over the past three years are presented. The status of new chemical elements is examined. Ten elements have had their atomic weight and uncertainty replaced by interval values of upper and lower bounds. Data on revised values for the isotopic composition of the elements are reviewed and new recommended values are presented for germanium. Radioactive half-lives are reviewed and latest values presented which include measurements on nuclides of interest and very long-lived nuclides such as double beta decay, double electron capture, long-lived alpha decay, and long-lived beta decay. The latest information and the status on the evaluation of atomic masses are discussed. Data from new measurements on the very heavy elements (trans-meitnerium elements) are discussed and tabulated. Data on various recent neutron cross-section and resonance integral measurements are also discussed and the latest measurements are tabulated in both cases. The JENDL-4.0 and ENDF/B-VII.1 nuclear data libraries are discussed. A new initiative on the existence and importance of isotopes is presented. (authors)

  20. Neutron reflecting supermirror structure

    DOEpatents

    Wood, James L.

    1992-01-01

    An improved neutron reflecting supermirror structure comprising a plurality of stacked sets of bilayers of neutron reflecting materials. The improved neutron reflecting supermirror structure is adapted to provide extremely good performance at high incidence angles, i.e. up to four time the critical angle of standard neutron mirror structures. The reflection of neutrons striking the supermirror structure at a high critical angle provides enhanced neutron throughput, and hence more efficient and economical use of neutron sources. One layer of each set of bilayers consist of titanium, and the second layer of each set of bilayers consist of an alloy of nickel with carbon interstitially present in the nickel alloy.

  1. NEUTRONIC REACTOR

    DOEpatents

    Stewart, H.B.

    1958-12-23

    A nuclear reactor of the type speclfically designed for the irradiation of materials is discussed. In this design a central cyllndrical core of moderating material ls surrounded by an active portlon comprlsed of an annular tank contalning fissionable material immersed ln a liquid moderator. The active portion ls ln turn surrounded by a reflector, and a well ls provided in the center of the core to accommodate the materlals to be irradiated. The over-all dimensions of the core ln at least one plane are equal to or greater than twice the effective slowing down length and equal to or less than twlce the effective diffuslon length for neutrons in the core materials.

  2. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.; Young, G.J.

    1958-10-14

    A method is presented for loading and unloading rod type fuel elements of a neutronic reactor of the heterogeneous, solld moderator, liquid cooled type. In the embodiment illustrated, the fuel rods are disposed in vertical coolant channels in the reactor core. The fuel rods are loaded and unloaded through the upper openings of the channels which are immersed in the coolant liquid, such as water. Unloading is accomplished by means of a coffer dam assembly having an outer sleeve which is placed in sealing relation around the upper opening. A radiation shield sleeve is disposed in and reciprocable through the coffer dam sleeve. A fuel rod engaging member operates through the axial bore in the radiation shield sleeve to withdraw the fuel rod from its position in the reactor coolant channel into the shield, the shield snd rod then being removed. Loading is accomplished in the reverse procedure.

  3. Direct Measurement of Neutron-Neutron Scattering

    SciTech Connect

    Sharapov, E.I.; Furman, W.I.; Lychagin, W.I.; Muzichka, G.V.; Nekhaev, G.V.; Safronov, Yu.V.; Shvetsov, V.N.; Strelkov, A.V.; Bowman, C.D.; Crawford, B.E.; Stephenson, S.L.; Howell, C.R.; Tornow, W.; Levakov, B.G.; Litvin, V.I.; Lyzhin, A.E.; Magda, E.P.; Mitchell, G.E.

    2003-08-26

    In order to resolve long-standing discrepancies in indirect measurements of the neutron-neutron scattering length ann and contribute to solving the problem of the charge symmetry of the nuclear force, the collaboration DIANNA (Direct Investigation of ann Association) plans to measure the neutron-neutron scattering cross section {sigma}nn. The key issue of our approach is the use of the through-channel in the Russia reactor YAGUAR with a peak neutron flux of 10{sup 18} /cm2/s. The proposed experimental setup is described. Results of calculations are presented to connect {sigma}nn with the nn-collision detector count rate and the neutron flux density in the reactor channel. Measurements of the thermal neutron fields inside polyethylene converters show excellent prospects for the realization of the direct nn-experiment.

  4. Neutron Capture Cross Sections for Radioactive Nuclei

    NASA Astrophysics Data System (ADS)

    Tonchev, Anton; Bedrossian, Peter; Escher, Jutta; Scielzo, Nicholas

    2015-10-01

    Accurate neutron-capture cross sections for radioactive nuclei near or far away from the line of beta stability are crucial for understanding the nucleosynthesis of heavy elements. However, neutron-capture cross sections for short-lived radionuclides are difficult to measure due to the fact that the measurements require both highly radioactive samples and intense neutron sources. Essential ingredients for describing the γ decays following neutron capture are the γ-ray strength function and level densities. We will compare different indirect approaches for obtaining observables that can constrain Hauser-Feshbach statistical model calculations of capture cross sections. Specifically, we will consider photon scattering, transfer reactions, and beta-delayed neutron emission. Challenges that exist on the path to obtaining neutron-capture cross sections for reactions on isotopes far from stability will be discussed. This work was performed under the auspices of US DOE by LLNL under contract DE-AC52-07NA27344. Funding was provided via the LDRD-ERD-069 project.

  5. Neutron environments on the Martian surface.

    PubMed

    Clowdsley, M S; Wilson, J W; Kim, M H; Singleterry, R C; Tripathi, R K; Heinbockel, J H; Badavi, F F; Shinn, J L

    2001-01-01

    Radiation is a primary concern in the planning of a manned mission to Mars. Recent studies using NASA Langley Research Center's HZETRN space radiation transport code show that the low energy neutron fluence on the Martian surface is larger than previously expected. The upper atmosphere of Mars is exposed to a background radiation field made up of a large number of protons during a solar particle event and mixture of light and heavy ions caused by galactic cosmic rays at other times. In either case, these charged ions interact with the carbon and oxygen atoms of the Martian atmosphere through ionization and nuclear collisions producing secondary ions and neutrons which then interact with the atmospheric atoms in a similar manner. In the past, only these downward moving particles have been counted in evaluating the neutron energy spectrum on the surface. Recent enhancements in the HZETRN code allow for the additional evaluation of those neutrons created within the Martian regolith through the same types of nuclear reactions, which rise to the surface. New calculations using this improved HZETRN code show that these upward moving neutrons contribute significantly to the overall neutron spectrum for energies less than 10 MeV. PMID:11770546

  6. Neutron skin thickness and equation of state in asymmetric nuclear matter

    NASA Astrophysics Data System (ADS)

    Yoshida, Satoshi; Sagawa, Hiroyuki

    2004-02-01

    The neutron skin thickness of stable and unstable nuclei is studied in Skyrme Hartree-Fock (SHF) and relativistic mean field (RMF) models to investigate the relation between the pressure and the equation of state in neutron matter. We found a clear linear correlation between the neutron skin thickness in heavy nuclei 132 Sn and 208 Pb and the pressure of neutron matter in both SHF and RMF models, while the correlation is weak in the unstable nuclei 32 Mg and 44 Ar . Relations between the neutron skin thickness and other nuclear matter properties such as the symmetry energy coefficients and the nuclear incompressibility are discussed.

  7. Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Miller, Christopher J. Miller

    2012-03-01

    There are many examples of clustering in astronomy. Stars in our own galaxy are often seen as being gravitationally bound into tight globular or open clusters. The Solar System's Trojan asteroids cluster at the gravitational Langrangian in front of Jupiter’s orbit. On the largest of scales, we find gravitationally bound clusters of galaxies, the Virgo cluster (in the constellation of Virgo at a distance of ˜50 million light years) being a prime nearby example. The Virgo cluster subtends an angle of nearly 8◦ on the sky and is known to contain over a thousand member galaxies. Galaxy clusters play an important role in our understanding of theUniverse. Clusters exist at peaks in the three-dimensional large-scale matter density field. Their sky (2D) locations are easy to detect in astronomical imaging data and their mean galaxy redshifts (redshift is related to the third spatial dimension: distance) are often better (spectroscopically) and cheaper (photometrically) when compared with the entire galaxy population in large sky surveys. Photometric redshift (z) [Photometric techniques use the broad band filter magnitudes of a galaxy to estimate the redshift. Spectroscopic techniques use the galaxy spectra and emission/absorption line features to measure the redshift] determinations of galaxies within clusters are accurate to better than delta_z = 0.05 [7] and when studied as a cluster population, the central galaxies form a line in color-magnitude space (called the the E/S0 ridgeline and visible in Figure 16.3) that contains galaxies with similar stellar populations [15]. The shape of this E/S0 ridgeline enables astronomers to measure the cluster redshift to within delta_z = 0.01 [23]. The most accurate cluster redshift determinations come from spectroscopy of the member galaxies, where only a fraction of the members need to be spectroscopically observed [25,42] to get an accurate redshift to the whole system. If light traces mass in the Universe, then the locations

  8. Neutron scattering from a ferrofluid

    SciTech Connect

    Lin, M.Y. |; Luo, W.; Lynn, J.

    1995-12-31

    Small angle neutron scattering experiments were performed on a eicosane-based ferrofluid. An average size of 88 {angstrom} can be extracted from the data, in agreement with results from electron microscopy. Below the frozen temperature of eicosane, however, the particles are seen to be in larger aggregates with a fractal dimension of 2.15, similar to those formed under reaction-limited cluster aggregation (RLCA) conditions. At high concentrations, particles form larger aggregates even in the liquid state. Applying a magnetic field introduces new structure and changes the density inside the aggregates.

  9. Thermal neutron imaging in an active interrogation environment

    SciTech Connect

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

    2009-03-10

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

  10. Occupational Clusters.

    ERIC Educational Resources Information Center

    Pottawattamie County School System, Council Bluffs, IA.

    The 15 occupational clusters (transportation, fine arts and humanities, communications and media, personal service occupations, construction, hospitality and recreation, health occupations, marine science occupations, consumer and homemaking-related occupations, agribusiness and natural resources, environment, public service, business and office…

  11. Neutron-rich B isotopes studied with antisymmetrized molecular dynamics

    SciTech Connect

    Kanada-En`yo, Y.; Horiuchi, H.

    1995-08-01

    Structure of odd-even B isotopes up to the neutron dripline is studied systematically with the antisymmetrized molecular dynamics (AMD). The AMD method has already proved to be a powerful theoretical approach for the systematic study of nuclear structure in extensive region including exotic neutron-rich nuclei as well as ordinary nuclei. It is owing to its flexible nature free from any model assumptions such as the existence of clusters. The energies and other observed data of B isotopes are reproduced well. Especially very good reproduction of electromagnetic properties is obtained. The systematic behavior of the electromagnetic properties is explained in relation to the drastic change between clustering structure and shell-model-like structure. This explanation gives us an important indication that clustering structure in neutron-rich B nuclei is strongly suggested by the experimental data. It is shown that the structure change with increase of the neutron number is largely governed by the shell effect of neutron orbits. Exotic structure with new type of clustering is suggested to evolve in neutron-rich nuclei near the dripline.

  12. Cluster generator

    DOEpatents

    Donchev, Todor I.; Petrov, Ivan G.

    2011-05-31

    Described herein is an apparatus and a method for producing atom clusters based on a gas discharge within a hollow cathode. The hollow cathode includes one or more walls. The one or more walls define a sputtering chamber within the hollow cathode and include a material to be sputtered. A hollow anode is positioned at an end of the sputtering chamber, and atom clusters are formed when a gas discharge is generated between the hollow anode and the hollow cathode.

  13. VizieR Online Data Catalog: Abundances in Galactic open clusters (Marsakov+, 2016)

    NASA Astrophysics Data System (ADS)

    Marsakov, V. A.; Gozha, M. L.; Koval', V. V.; Shpigel', L. V.

    2016-07-01

    Spectroscopic determinations of the relative abundances of alpha-elements (O, Mg, Si, Ca, and Ti), slow neutron capture elements (Y, Ba, La, Ce, Nd, and Zr), rapid neutron capture element (Eu), and elements with an odd number of protons (Na, Al) are collected for 90 open clusters of the Galaxy. Metallicities are presented for 346 clusters. In addition catalog contains positions, ages, velocities, elements of Galactic orbits for open clusters. (2 data files).

  14. Astrophysics of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Ettori, Stefano

    2016-07-01

    As the nodes of the cosmic web, clusters of galaxies trace the large-scale distribution of matter in the Universe. They are thus privileged sites in which to investigate the complex physics of structure formation. However, the complete story of how these structures grow, and how they dissipate the gravitational and non-thermal components of their energy budget over cosmic time, is still beyond our grasp. Most of the baryons gravitationally bound to the cluster's halo is in the form of a diffuse, hot, metal-enriched plasma that radiates primarily in the X-ray band. X-ray observations of the evolving cluster population provide a unique opportunity to address such fundamental open questions as: How do hot diffuse baryons accrete and dynamically evolve in dark matter potentials? How and when was the energy that we observe in the ICM generated and distributed? Where and when are heavy elements produced and how are they circulated? We will present the ongoing activities to define the strategy on how an X-ray observatory with large collecting area and an unprecedented combination of high spectral and angular resolution, such as Athena, can address these questions.

  15. Neutron capture by hook or by crook

    NASA Astrophysics Data System (ADS)

    Mosby, Shea

    2016-03-01

    The neutron capture reaction is a topic of fundamental interest for both heavy element (A>60) nucleosynthesis and applications in such fields as nuclear energy and defense. The full suite of interesting isotopes ranges from stable nuclei to the most exotic, and it is not possible to directly measure all the relevant reaction rates. The DANCE instrument at Los Alamos provides direct access to the neutron capture reaction for stable and long-lived nuclei, while Apollo coupled to HELIOS at Argonne has been developed as an indirect probe for cases where a direct measurement is impossible. The basic techniques and their implications will be presented, and the status of ongoing experimental campaigns to address neutron capture in the A=60 and A=100 mass regions will be discussed.

  16. Realistic fission model and the r-process in neutron star mergers

    SciTech Connect

    Shibagaki, S.; Kajino, T.; Chiba, S.; Mathews, G. J.

    2014-05-09

    About half of heavy elements are considered to be produced by the rapid neutron-capture process, r-process. The neutron star merger is one of the viable candidates for the astrophysical site of r-process nucleosynthesis. Nuclear fission reactions play an important role in the r-process of neutron star mergers. However theoretical predictions about fission properties of neutron-rich nuclei have some uncertainties. Especially, their fission fragment distributions are totally unknown and the phenomenologically extrapolated distribution was often applied to nucleosynthesis calculations. In this study, we have carried out r-process nucleosynthesis calculations based upon new theoretical estimates of fission fragment distributions. We discuss the effects on the r-process in neutron star mergers from the nuclear fission of heavy neutron-rich actinide elements. We also discuss how variations in the fission fragment distributions affect the abundance pattern.

  17. Millisecond radio pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Verbunt, Frank; Lewin, Walter H. G.; Van Paradijs, Jan

    1989-01-01

    It is shown that the number of millisecond radio pulsars, in globular clusters, should be larger than 100, applying the standard scenario that all the pulsars descend from low-mass X-ray binaries. Moreover, most of the pulsars are located in a small number of clusters. The prediction that Teran 5 and Liller 1 contain at least about a dozen millisecond radio pulsars each is made. The observations of millisecond radio pulsars in globular clusters to date, in particular the discovery of two millisecond radio pulsars in 47 Tuc, are in agreement with the standard scenario, in which the neutron star is spun up during the mass transfer phase.

  18. Studies of light neutron-excess systems from bounds to continuum

    SciTech Connect

    Ito, Makoto; Otsu, Hideaki

    2012-10-20

    The generalized two-center cluster model (GTCM), which can handle various single particle configurations in general two center systems, is applied to the light neutron-rich system, {sup 12}Be = {alpha}+{alpha}+4N. We discuss the change of the neutrons' configuration around two {alpha}-cores as a variation of an excitation energy. We show that the excess neutrons form various chemical-bondinglike configurations around two {alpha} cores in the unbound region above the {alpha} decay threshold. The possibility of the {alpha} cluster formation in the heavier neutron-excess system, {sup 28}Ne, is also discussed.

  19. Advanced Neutron Source: Plant Design Requirements

    SciTech Connect

    Not Available

    1990-07-01

    The Advanced Neutron Source will be a new world-class facility for research using hot, thermal, cold, and ultra-cold neutrons. The heart of the facility will be a 330-MW (fission), heavy-water cooled and heavy-water moderated reactor. The reactor will be housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides will fan out into a large guide hall, housing about 30 neutron research stations. Appropriate office, laboratory, and shop facilities will be included to provide a complete facility for users. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory early in the next decade. This PDR document defines the plant-level requirements for the design, construction, and operation of ANS. It also defines and provides input to the individual System Design Description (SDD) documents. Together, this PDR document and the set of SDD documents will define and control the baseline configuration of ANS.

  20. Experience of boron neutron capture therapy in Japan

    NASA Astrophysics Data System (ADS)

    Kanda, Keiji

    1997-02-01

    In Japan the boron neutron capture therapy has been applied to more than 200 patients, mostly brain tumors and some melanomas. For brain tumors, Kyoto University, Kyoto Prefectural University of Medicine, Tsukuba University and National Kagawa Children's Hospital accept patients, and for melanomas, Kobe University and Mishima Institute of Dermatological Research accept patients so far. Recently the heavy water facility of Kyoto University Reactor has been upgraded for epithermal neutron as well as thermal neutron irradiations, and for the patient treatment during the continuous operation of the KUR.

  1. NEUTRON REACTOR HAVING A Xe$sup 135$ SHIELD

    DOEpatents

    Stanton, H.E.

    1957-10-29

    Shielding for reactors of the type in which the fuel is a chain reacting liquid composition comprised essentially of a slurry of fissionable and fertile material suspended in a liquid moderator is discussed. The neutron reflector comprises a tank containing heavy water surrounding the reactor, a shield tank surrounding the reflector, a gamma ray shield surrounding said shield tank, and a means for conveying gaseous fission products, particularly Xe/sup 135/, from the reactor chamber to the shield tank, thereby serving as a neutron shield by capturing the thermalized neutrons that leak outwardly from the shield tank.

  2. Heavy Stars Thrive among Heavy Elements

    NASA Astrophysics Data System (ADS)

    2002-08-01

    VLT Observes Wolf-Rayet Stars in Virgo Cluster Galaxies [1] Summary Do very massive stars form in metal-rich regions of the Universe and in the nuclei of galaxies ? Or does "heavy element poisoning" stop stellar growth at an early stage, before young stars reach the "heavyweight class"? What may at the first glance appear as a question for specialists actually has profound implications for our understanding of the evolution of galaxies, those systems of billions of stars - the main building blocks of the Universe. With an enormous output of electromagnetic radiation and energetic elementary particles, massive stars exert a decisive influence on the surrounding (interstellar) gas and dust clouds . They also eject large amounts of processed elements, thereby participating in the gradual build-up of the many elements we see today. Thus the presence or absence of such stars at the centres of galaxies can significantly change the overall development of those regions and hence, presumably, that of the entire galaxy. A team of European astronomers [2] has now directly observed the presence of so-called Wolf-Rayet stars (born with masses of 60 - 90 times that of the Sun or more) within metal-rich regions in some galaxies in the Virgo cluster, some 50 million light-years away. This is the first unambiguous detection of such massive stellar objects in metal-rich regions . PR Photo 20a/02 : H II regions in the Virgo cluster galaxy NGC 4254 . PR Photo 20b/02 : Multi-object-slit observation of galaxy NGC 4303 . PR Photo 20c/02 : Spectrum of H II region in NGC 4254 with Wolf-Rayet signatures. Production of heavy elements in the Universe Most scientists agree that the Universe in which we live underwent a dramatic event, known as the Big Bang , approximately 15,000 million years ago. During the early moments, elementary particles were formed which after some time united into more complex nuclei and in turn resulted in the production of hydrogen and helium atoms and their isotopes

  3. Neutron range spectrometer

    DOEpatents

    Manglos, Stephen H.

    1989-06-06

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

  4. Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars

    NASA Technical Reports Server (NTRS)

    Eichler, David; Livio, Mario; Piran, Tsvi; Schramm, David N.

    1989-01-01

    It is pointed out here that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process). Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts. It is argued that observed r-process abundances and gamma-ray burst rates predict rates for these collisions that are both significant and consistent with other estimates.

  5. Cluster Features of Normal-, Super- and Hyperdeformed nuclei

    SciTech Connect

    Adamian, G.G.; Antonenko, N.V.; Kuklin, S.N.

    2005-11-21

    It is shown that an important mode of nuclear excitations in different processes like as cluster radioactivity, parity splitting in normal deformed bands, decay out phenomenon of the yrast superdeformed states in the heavy nuclei and formation of super- and hyper-deformed states in induced fission and heavy ion reactions is related to the motion in charge (mass) asymmetry coordinate. With the suggested cluster model one can try to unify all phenomena mentioned above.

  6. Experimental Neutron Capture Rate Constraint Far from Stability

    NASA Astrophysics Data System (ADS)

    Liddick, S. N.; Spyrou, A.; Crider, B. P.; Naqvi, F.; Larsen, A. C.; Guttormsen, M.; Mumpower, M.; Surman, R.; Perdikakis, G.; Bleuel, D. L.; Couture, A.; Crespo Campo, L.; Dombos, A. C.; Lewis, R.; Mosby, S.; Nikas, S.; Prokop, C. J.; Renstrom, T.; Rubio, B.; Siem, S.; Quinn, S. J.

    2016-06-01

    Nuclear reactions where an exotic nucleus captures a neutron are critical for a wide variety of applications, from energy production and national security, to astrophysical processes, and nucleosynthesis. Neutron capture rates are well constrained near stable isotopes where experimental data are available; however, moving far from the valley of stability, uncertainties grow by orders of magnitude. This is due to the complete lack of experimental constraints, as the direct measurement of a neutron-capture reaction on a short-lived nucleus is extremely challenging. Here, we report on the first experimental extraction of a neutron capture reaction rate on 69Ni, a nucleus that is five neutrons away from the last stable isotope of Ni. The implications of this measurement on nucleosynthesis around mass 70 are discussed, and the impact of similar future measurements on the understanding of the origin of the heavy elements in the cosmos is presented.

  7. Experimental Neutron Capture Rate Constraint Far from Stability.

    PubMed

    Liddick, S N; Spyrou, A; Crider, B P; Naqvi, F; Larsen, A C; Guttormsen, M; Mumpower, M; Surman, R; Perdikakis, G; Bleuel, D L; Couture, A; Crespo Campo, L; Dombos, A C; Lewis, R; Mosby, S; Nikas, S; Prokop, C J; Renstrom, T; Rubio, B; Siem, S; Quinn, S J

    2016-06-17

    Nuclear reactions where an exotic nucleus captures a neutron are critical for a wide variety of applications, from energy production and national security, to astrophysical processes, and nucleosynthesis. Neutron capture rates are well constrained near stable isotopes where experimental data are available; however, moving far from the valley of stability, uncertainties grow by orders of magnitude. This is due to the complete lack of experimental constraints, as the direct measurement of a neutron-capture reaction on a short-lived nucleus is extremely challenging. Here, we report on the first experimental extraction of a neutron capture reaction rate on ^{69}Ni, a nucleus that is five neutrons away from the last stable isotope of Ni. The implications of this measurement on nucleosynthesis around mass 70 are discussed, and the impact of similar future measurements on the understanding of the origin of the heavy elements in the cosmos is presented.

  8. Experimental Neutron Capture Rate Constraint Far from Stability.

    PubMed

    Liddick, S N; Spyrou, A; Crider, B P; Naqvi, F; Larsen, A C; Guttormsen, M; Mumpower, M; Surman, R; Perdikakis, G; Bleuel, D L; Couture, A; Crespo Campo, L; Dombos, A C; Lewis, R; Mosby, S; Nikas, S; Prokop, C J; Renstrom, T; Rubio, B; Siem, S; Quinn, S J

    2016-06-17

    Nuclear reactions where an exotic nucleus captures a neutron are critical for a wide variety of applications, from energy production and national security, to astrophysical processes, and nucleosynthesis. Neutron capture rates are well constrained near stable isotopes where experimental data are available; however, moving far from the valley of stability, uncertainties grow by orders of magnitude. This is due to the complete lack of experimental constraints, as the direct measurement of a neutron-capture reaction on a short-lived nucleus is extremely challenging. Here, we report on the first experimental extraction of a neutron capture reaction rate on ^{69}Ni, a nucleus that is five neutrons away from the last stable isotope of Ni. The implications of this measurement on nucleosynthesis around mass 70 are discussed, and the impact of similar future measurements on the understanding of the origin of the heavy elements in the cosmos is presented. PMID:27367386

  9. Production of neutrons from interactions of GCR-like particles

    NASA Technical Reports Server (NTRS)

    Heilbronn, L.; Frankel, K.; Holabird, K.; Zeitlin, C.; McMahan, M. A.; Rathbun, W.; Cronqvist, M.; Gong, W.; Madey, R.; Htun, M.; Elaasar, M.; Anderson, B. D.; Baldwin, A. R.; Jiang, J.; Keane, D.; Scott, A.; Shao, Y.; Watson, J. W.; Zhang, W. M.; Galonsky, A.; Ronningen, R.; Zecher, P.; Kruse, J.; Wang, J.; Miller, J. (Principal Investigator)

    1998-01-01

    In order to help assess the risk to astronauts due to the long-term exposure to the natural radiation environment in space, an understanding of how the primary radiation field is changed when passing through shielding and tissue materials must be obtained. One important aspect of the change in the primary radiation field after passing through shielding materials is the production of secondary particles from the breakup of the primary. Neutrons are an important component of the secondary particle field due to their relatively high biological weighting factors, and due to their relative abundance, especially behind thick shielding scenarios. Because of the complexity of the problem, the estimation of the risk from exposure to the secondary neutron field must be handled using calculational techniques. However, those calculations will need an extensive set of neutron cross section and thicktarget neutron yield data in order to make an accurate assessment of the risk. In this paper we briefly survey the existing neutron-production data sets that are applicable to the space radiation transport problem, and we point out how neutron production from protons is different than neutron production from heavy ions. We also make comparisons of one the heavy-ion data sets with Boltzmann-Uehling-Uhlenbeck (BUU) calculations.

  10. NGC 7789: An open cluster case study

    SciTech Connect

    Overbeek, Jamie C.; Friel, Eileen D.; Pilachowski, Catherine A.; Mészáros, Szabolcs; Jacobson, Heather R.; Johnson, Christian I.

    2015-01-01

    We have obtained high-resolution spectra of 32 giants in the open cluster NGC 7789 using the Wisconsin–Indiana–Yale–NOAO Hydra spectrograph. We explore differences in atmospheric parameters and elemental abundances caused by the use of the linelist developed for the Gaia-ESO Survey (GES) compared to one based on Arcturus used in our previous work. [Fe/H] values decrease when using the GES linelist instead of the Arcturus-based linelist; these differences are probably driven by systematically lower (∼−0.1 dex) GES surface gravities. Using the GES linelist we determine abundances for 10 elements—Fe, Mg, Si, Ca, Ti, Na, Ni, Zr, Ba, and La. We find the cluster's average metallicity [Fe/H] = 0.03 ± 0.07 dex, in good agreement with literature values, and a lower [Mg/Fe] abundance than has been reported before for this cluster (0.11 ± 0.05 dex). We also find the neutron-capture element barium to be highly enhanced—[Ba/Fe] = +0.48 ± 0.08—and disparate from cluster measurements of neutron-capture elements La and Zr (−0.08 ± 0.05 and 0.08 ± 0.08, respectively). This is in accordance with recent discoveries of supersolar Ba enhancement in young clusters along with more modest enhancement of other neutron-capture elements formed in similar environments.

  11. NEUTRONIC REACTOR

    DOEpatents

    Ohlinger, L.A.; Wigner, E.P.; Weinberg, A.M.; Young, G.J.

    1958-09-01

    This patent relates to neutronic reactors of the heterogeneous water cooled type, and in particular to a fuel element charging and discharging means therefor. In the embodiment illustrated the reactor contains horizontal, parallel coolant tubes in which the fuel elements are disposed. A loading cart containing a magnzine for holding a plurality of fuel elements operates along the face of the reactor at the inlet ends of the coolant tubes. The loading cart is equipped with a ram device for feeding fuel elements from the magazine through the inlot ends of the coolant tubes. Operating along the face adjacent the discharge ends of the tubes there is provided another cart means adapted to receive irradiated fuel elements as they are forced out of the discharge ends of the coolant tubes by the incoming new fuel elements. This cart is equipped with a tank coataining a coolant, such as water, into which the fuel elements fall, and a hydraulically operated plunger to hold the end of the fuel element being discharged. This inveation provides an apparatus whereby the fuel elements may be loaded into the reactor, irradiated therein, and unloaded from the reactor without stopping the fiow of the coolant and without danger to the operating personnel.

  12. Relativistic effective interaction for nuclei, giant resonances, and neutron stars

    SciTech Connect

    Fattoyev, F. J.; Piekarewicz, J.; Horowitz, C. J.; Shen, G.

    2010-11-15

    Nuclear effective interactions are useful tools in astrophysical applications especially if one can guide the extrapolations to the extremes regions of isospin and density that are required to simulate dense, neutron-rich systems. Isospin extrapolations may be constrained in the laboratory by measuring the neutron skin thickness of a heavy nucleus, such as {sup 208}Pb. Similarly, future observations of massive neutron stars will constrain the extrapolations to the high-density domain. In this contribution we introduce a new relativistic effective interaction that is simultaneously constrained by the properties of finite nuclei, their collective excitations, and neutron-star properties. By adjusting two of the empirical parameters of the theory, one can efficiently tune the neutron skin thickness of {sup 208}Pb and the maximum neutron-star mass. We illustrate this procedure in response to the recent interpretation of x-ray observations by Steiner, Lattimer, and Brown that suggests that the FSUGold effective interaction predicts neutron-star radii that are too large and a maximum stellar mass that is too small. The new effective interaction is fitted to a neutron skin thickness in {sup 208}Pb of only R{sub n}-R{sub p}=0.16 fm and yields a moderately large maximum neutron-star mass of 1.94 M{sub {center_dot}}.

  13. Spectroscopic Factors and Barrier Penetrabilities in Cluster Radioactivity

    SciTech Connect

    Kuklin, S.N.; Adamian, G.G.; Antonenko, N.V.

    2005-09-01

    The cold cluster decay model is presented in the framework of a dinuclear system concept. Spectroscopic factors are extracted from barrier penetrabilities and measured half-lives. The deformation of the light cluster and residual nucleus is shown to affect the nucleus-nucleus potential and decay characteristics. Half-lives are predicted for neutron-deficient actinides and intermediate-mass nuclei. The connection between spontaneous fission and cluster radioactivity is discussed.

  14. Electromagnetic heavy-lepton pair production in relativistic heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Şengül, M. Y.; Güçlü, M. C.; Mercan, Ö.; Karakuş, N. G.

    2016-08-01

    We calculate the cross sections of electromagnetic productions of muon- and tauon-pair productions from the ultra-relativistic heavy ion collisions. Since the Compton wavelengths of muon and tauon are comparable to the radius of the colliding ions, nuclear form factors play important roles for calculating the cross sections. Recent measurement (Abrahamyan et al., Phys Rev Lett 108:112502, 2012) indicates that the neutrons are differently distributed from the protons; therefore this affects the cross section of the heavy-lepton pair production. In order to see the effects of the neutron distributions in the nucleus, we used analytical expression of the Fourier transforms of the Wood-Saxon distribution. Cross section calculations show that the Wood-Saxon distribution function is more sensitive to the parameter R compared to the parameter a.

  15. Neutron streak camera

    DOEpatents

    Wang, Ching L.

    1983-09-13

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  16. Layered semiconductor neutron detectors

    DOEpatents

    Mao, Samuel S; Perry, Dale L

    2013-12-10

    Room temperature operating solid state hand held neutron detectors integrate one or more relatively thin layers of a high neutron interaction cross-section element or materials with semiconductor detectors. The high neutron interaction cross-section element (e.g., Gd, B or Li) or materials comprising at least one high neutron interaction cross-section element can be in the form of unstructured layers or micro- or nano-structured arrays. Such architecture provides high efficiency neutron detector devices by capturing substantially more carriers produced from high energy .alpha.-particles or .gamma.-photons generated by neutron interaction.

  17. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1981-05-14

    Apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon.

  18. Neutron streak camera

    DOEpatents

    Wang, C.L.

    1983-09-13

    Disclosed is an apparatus for improved sensitivity and time resolution of a neutron measurement. The detector is provided with an electrode assembly having a neutron sensitive cathode which emits relatively low energy secondary electrons. The neutron sensitive cathode has a large surface area which provides increased sensitivity by intercepting a greater number of neutrons. The cathode is also curved to compensate for differences in transit time of the neutrons emanating from the point source. The slower speeds of the secondary electrons emitted from a certain portion of the cathode are matched to the transit times of the neutrons impinging thereupon. 4 figs.

  19. Organic metal neutron detector

    DOEpatents

    Butler, M.A.; Ginley, D.S.

    1984-11-21

    A device for detection of neutrons comprises: as an active neutron sensing element, a conductive organic polymer having an electrical conductivity and a cross-section for said neutrons whereby a detectable change in said conductivity is caused by impingement of said neutrons on the conductive organic polymer which is responsive to a property of said polymer which is altered by impingement of said neutrons on the polymer; and means for associating a change in said alterable property with the presence of neutrons at the location of said device.

  20. Neutronic Reactor Design to Reduce Neutron Loss

    DOEpatents

    Miles, F. T.

    1961-05-01

    A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall. The wall is surrounded by successive layers of pure fertile material and moderator containing fertile material. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. Since the steel has a smaller capture cross section for the fast neutrons, greater nunnbers of neutrons will pass into the blanket, thereby increasing the over-all efficiency of the reactor. (AEC)

  1. NEUTRONIC REACTOR DESIGN TO REDUCE NEUTRON LOSS

    DOEpatents

    Mills, F.T.

    1961-05-01

    A nuclear reactor construction is described in which an unmoderated layer of the fissionable material is inserted between the moderated portion of the reactor core and the core container steel wall which is surrounded by successive layers of pure fertile material and fertile material having moderator. The unmoderated layer of the fissionable material will insure that a greater portion of fast neutrons will pass through the steel wall than would thermal neutrons. As the steel has a smaller capture cross-section for the fast neutrons, then greater numbers of the neutrons will pass into the blanket thereby increasing the over-all efficiency of the reactor.

  2. ARE THERE ANY STARS LACKING NEUTRON-CAPTURE ELEMENTS? EVIDENCE FROM STRONTIUM AND BARIUM

    SciTech Connect

    Roederer, Ian U.

    2013-01-01

    The cosmic dispersion in the abundances of the heavy elements strontium and barium in halo stars is well known. Strontium and barium are detected in most cool, metal-poor giants, but are these elements always detectable? To identify stars that could be considered probable candidates for lacking these elements, I examine the stellar abundance data available in the literature for 1148 field stars and 226 stars in dwarf galaxies, 776 of which have metallicities lower than [Fe/H] <-2.0. Strontium or barium have been detected in all field, globular cluster, and dwarf galaxy environments studied. All upper limits are consistent with the lowest detected ratios of [Sr/H] and [Ba/H]. The frequent appearance of these elements raises the intriguing prospect that at least one kind of neutron-capture reaction operates as often as the nucleosynthesis mechanisms that produce lighter elements, such as magnesium, calcium, or iron, although the yields of heavy elements may be more variable.

  3. Neutron anatomy

    SciTech Connect

    Bacon, G.E.

    1994-12-31

    The familiar extremes of crystalline material are single-crystals and random powders. In between these two extremes are polycrystalline aggregates, not randomly arranged but possessing some preferred orientation and this is the form taken by constructional materials, be they steel girders or the bones of a human or animal skeleton. The details of the preferred orientation determine the ability of the material to withstand stress in any direction. In the case of bone the crucial factor is the orientation of the c-axes of the mineral content - the crystals of the hexagonal hydroxyapatite - and this can readily be determined by neutron diffraction. In particular it can be measured over the volume of a piece of bone, utilizing distances ranging from 1mm to 10mm. The major practical problem is to avoid the intense incoherent scattering from the hydrogen in the accompanying collagen; this can best be achieved by heat-treatment and it is demonstrated that this does not affect the underlying apatite. These studies of bone give leading anatomical information on the life and activities of humans and animals - including, for example, the life history of the human femur, the locomotion of sheep, the fracture of the legs of racehorses and the life-styles of Neolithic tribes. We conclude that the material is placed economically in the bone to withstand the expected stresses of life and the environment. The experimental results are presented in terms of the magnitude of the 0002 apatite reflection. It so happens that for a random powder the 0002, 1121 reflections, which are neighboring lines in the powder pattern, are approximately equal in intensity. The latter reflection, being of manifold multiplicity, is scarcely affected by preferred orientation so that the numerical value of the 0002/1121 ratio serves quite accurately as a quantitative measure of the degree of orientation of the c-axes in any chosen direction for a sample of bone.

  4. 2010 Neutron Review: ORNL Neutron Sciences Progress Report

    SciTech Connect

    Bardoel, Agatha A; Counce, Deborah M; Ekkebus, Allen E; Horak, Charlie M; Nagler, Stephen E; Kszos, Lynn A

    2011-06-01

    During 2010, the Neutron Sciences Directorate focused on producing world-class science, while supporting the needs of the scientific community. As the instrument, sample environment, and data analysis tools at High Flux Isotope Reactor (HFIR ) and Spallation Neutron Source (SNS) have grown over the last year, so has promising neutron scattering research. This was an exciting year in science, technology, and operations. Some topics discussed are: (1) HFIR and SNS Experiments Take Gordon Battelle Awards for Scientific Discovery - Battelle Memorial Institute presented the inaugural Gordon Battelle Prizes for scientific discovery and technology impact in 2010. Battelle awards the prizes to recognize the most significant advancements at national laboratories that it manages or co-manages. (2) Discovery of Element 117 - As part of an international team of scientists from Russia and the United States, HFIR staff played a pivotal role in the discovery by generating the berkelium used to produce the new element. A total of six atoms of ''ununseptium'' were detected in a two-year campaign employing HFIR and the Radiochemical Engineering Development Center at Oak Ridge National Laboratory (ORNL) and the heavy-ion accelerator capabilities at the Joint Institute for Nuclear Research in Dubna, Russia. The discovery of the new element expands the understanding of the properties of nuclei at extreme numbers of protons and neutrons. The production of a new element and observation of 11 new heaviest isotopes demonstrate the increased stability of super-heavy elements with increasing neutron numbers and provide the strongest evidence to date for the existence of an island of enhanced stability for super-heavy elements. (3) Studies of Iron-Based High-Temperature Superconductors - ORNL applied its distinctive capabilities in neutron scattering, chemistry, physics, and computation to detailed studies of the magnetic excitations of iron-based superconductors (iron pnictides and

  5. Neutron dosimetric measurements in shuttle and MIR.

    PubMed

    Reitz, G

    2001-06-01

    Detector packages consisting of thermoluminescence detectors (TLD), nuclear emulsions and plastic track detectors were exposed at identical positions inside MIR space station and on shuttle flights inside Spacelab and Spacehab during different phases of the solar cycle. The objectives of the investigations are to provide data on charge and energy spectra of heavy ions, and the contribution of events with low-energy deposit (protons, electrons, gamma, etc.) to the dose, as well as the contribution of secondaries, such as nuclear disintegration stars and neutrons. For neutron dosimetry 6LiF (TLD600) and 7LiF (TLD700) chips were used both of which have almost the same response to gamma rays but different response to neutrons. Neutrons in space are produced mainly in evaporation and knock-on processes with energies mainly of 1-10 MeV and up to several 100 MeV, respectively. The energy spectrum undergoes continuous changes toward greater depth in the attenuating material until an equilibrium is reached. In equilibrium, the spectrum is a wide continuum extending down to thermal energies to which the 6LiF is sensitive. Based on the difference of absorbed doses in the 6LiF and 7LiF chips, thermal neutron fluxes from 1 to 2.3 cm-2 s-1 are calculated using the assumption that the maximum induced dose in TLD600 for 1 neutron cm-2 is 1.6 x 10(-10) Gy (Horowitz and Freeman, Nucl. Instr. and Meth. 157 (1978) 393). It is assumed that the flux of high-energy neutrons is at least of that quantity. Tissue doses were calculated taking as a mean ambient absorbed dose per neutron 6 x10(-12) Gy cm2 (for a10 MeV neutron). The neutron equivalent doses for the above-mentioned fluxes are 52 micro Gy d-1 and 120 micro Gy d-1. In recent experiments, a personal neutron dosimeter was integrated into the dosimeter packages. First results of this dosimeter which is based on nuclear track detectors with converter foils are reported. For future measurements, a scintillator counter with

  6. Neutron dosimetric measurements in shuttle and MIR.

    PubMed

    Reitz, G

    2001-06-01

    Detector packages consisting of thermoluminescence detectors (TLD), nuclear emulsions and plastic track detectors were exposed at identical positions inside MIR space station and on shuttle flights inside Spacelab and Spacehab during different phases of the solar cycle. The objectives of the investigations are to provide data on charge and energy spectra of heavy ions, and the contribution of events with low-energy deposit (protons, electrons, gamma, etc.) to the dose, as well as the contribution of secondaries, such as nuclear disintegration stars and neutrons. For neutron dosimetry 6LiF (TLD600) and 7LiF (TLD700) chips were used both of which have almost the same response to gamma rays but different response to neutrons. Neutrons in space are produced mainly in evaporation and knock-on processes with energies mainly of 1-10 MeV and up to several 100 MeV, respectively. The energy spectrum undergoes continuous changes toward greater depth in the attenuating material until an equilibrium is reached. In equilibrium, the spectrum is a wide continuum extending down to thermal energies to which the 6LiF is sensitive. Based on the difference of absorbed doses in the 6LiF and 7LiF chips, thermal neutron fluxes from 1 to 2.3 cm-2 s-1 are calculated using the assumption that the maximum induced dose in TLD600 for 1 neutron cm-2 is 1.6 x 10(-10) Gy (Horowitz and Freeman, Nucl. Instr. and Meth. 157 (1978) 393). It is assumed that the flux of high-energy neutrons is at least of that quantity. Tissue doses were calculated taking as a mean ambient absorbed dose per neutron 6 x10(-12) Gy cm2 (for a10 MeV neutron). The neutron equivalent doses for the above-mentioned fluxes are 52 micro Gy d-1 and 120 micro Gy d-1. In recent experiments, a personal neutron dosimeter was integrated into the dosimeter packages. First results of this dosimeter which is based on nuclear track detectors with converter foils are reported. For future measurements, a scintillator counter with

  7. Cluster aspects of p-shell and sd-shell nuclei

    SciTech Connect

    Kanada-En'yo, Y.; Kobayashi, F.; Suhara, T.; Kimura, M.; Taniguchi, Y.

    2011-05-06

    We report some topics on cluster structures studied by using a theoretical method of antisymmetrized molecular dynamics(AMD). Cluster features of p-shell and sd-shell nuclei are discussed. In particular, three alpha cluster structures in the excited states of {sup 12}C and {sup 14}C are focused. Dineutron correlations in neutron-rich nuclei are also discussed.

  8. Dose equivalent neutron dosimeter

    DOEpatents

    Griffith, Richard V.; Hankins, Dale E.; Tomasino, Luigi; Gomaa, Mohamed A. M.

    1983-01-01

    A neutron dosimeter is disclosed which provides a single measurements indicating the amount of potential biological damage resulting from the neutron exposure of the wearer, for a wide range of neutron energies. The dosimeter includes a detecting sheet of track etch detecting material such as a carbonate plastic, for detecting higher energy neutrons, and a radiator layer containing conversion material such as .sup.6 Li and .sup.10 B lying adjacent to the detecting sheet for converting moderate energy neutrons to alpha particles that produce tracks in the adjacent detecting sheet. The density of conversion material in the radiator layer is of an amount which is chosen so that the density of tracks produced in the detecting sheet is proportional to the biological damage done by neutrons, regardless of whether the tracks are produced as the result of moderate energy neutrons striking the radiator layer or as the result of higher energy neutrons striking the sheet of track etch material.

  9. Ultrafast neutron detector

    DOEpatents

    Wang, C.L.

    1985-06-19

    A neutron detector of very high temporal resolution is described. It may be used to measure distributions of neutrons produced by fusion reactions that persist for times as short as about 50 picoseconds.

  10. On neutron surface waves

    SciTech Connect

    Ignatovich, V. K.

    2009-01-15

    It is shown that neutron surface waves do not exist. The difference between the neutron wave mechanics and the wave physics of electromagnetic and acoustic processes, which allows the existence of surface waves, is analyzed.

  11. Neutron dose equivalent meter

    DOEpatents

    Olsher, Richard H.; Hsu, Hsiao-Hua; Casson, William H.; Vasilik, Dennis G.; Kleck, Jeffrey H.; Beverding, Anthony

    1996-01-01

    A neutron dose equivalent detector for measuring neutron dose capable of accurately responding to neutron energies according to published fluence to dose curves. The neutron dose equivalent meter has an inner sphere of polyethylene, with a middle shell overlying the inner sphere, the middle shell comprising RTV.RTM. silicone (organosiloxane) loaded with boron. An outer shell overlies the middle shell and comprises polyethylene loaded with tungsten. The neutron dose equivalent meter defines a channel through the outer shell, the middle shell, and the inner sphere for accepting a neutron counter tube. The outer shell is loaded with tungsten to provide neutron generation, increasing the neutron dose equivalent meter's response sensitivity above 8 MeV.

  12. Pulsed-neutron monochromator

    DOEpatents

    Mook, H.A. Jr.

    1984-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The waves are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

  13. Pulsed-neutron monochromator

    DOEpatents

    Mook, Jr., Herbert A.

    1985-01-01

    In one aspect, the invention is an improved pulsed-neutron monochromator of the vibrated-crystal type. The monochromator is designed to provide neutron pulses which are characterized both by short duration and high density. A row of neutron-reflecting crystals is disposed in a neutron beam to reflect neutrons onto a common target. The crystals in the row define progressively larger neutron-scattering angles and are vibrated sequentially in descending order with respect to the size of their scattering angles, thus generating neutron pulses which arrive simultaneously at the target. Transducers are coupled to one end of the crystals to vibrate them in an essentially non-resonant mode. The transducers propagate transverse waves in the crystal which progress longitudinally therein. The wave are absorbed at the undriven ends of the crystals by damping material mounted thereon. In another aspect, the invention is a method for generating neutron pulses characterized by high intensity and short duration.

  14. ULTRASONIC NEUTRON DOSIMETER

    DOEpatents

    Truell, R.; de Klerk, J.; Levy, P.W.

    1960-02-23

    A neutron dosimeter is described which utilizes ultrasonic waves in the megacycle region for determination of the extent of neutron damage in a borosilicate glass through ultrasonic wave velocity and attenuation measurements before and after damage.

  15. Intense fusion neutron sources

    NASA Astrophysics Data System (ADS)

    Kuteev, B. V.; Goncharov, P. R.; Sergeev, V. Yu.; Khripunov, V. I.

    2010-04-01

    The review describes physical principles underlying efficient production of free neutrons, up-to-date possibilities and prospects of creating fission and fusion neutron sources with intensities of 1015-1021 neutrons/s, and schemes of production and application of neutrons in fusion-fission hybrid systems. The physical processes and parameters of high-temperature plasmas are considered at which optimal conditions for producing the largest number of fusion neutrons in systems with magnetic and inertial plasma confinement are achieved. The proposed plasma methods for neutron production are compared with other methods based on fusion reactions in nonplasma media, fission reactions, spallation, and muon catalysis. At present, intense neutron fluxes are mainly used in nanotechnology, biotechnology, material science, and military and fundamental research. In the near future (10-20 years), it will be possible to apply high-power neutron sources in fusion-fission hybrid systems for producing hydrogen, electric power, and technological heat, as well as for manufacturing synthetic nuclear fuel and closing the nuclear fuel cycle. Neutron sources with intensities approaching 1020 neutrons/s may radically change the structure of power industry and considerably influence the fundamental and applied science and innovation technologies. Along with utilizing the energy produced in fusion reactions, the achievement of such high neutron intensities may stimulate wide application of subcritical fast nuclear reactors controlled by neutron sources. Superpower neutron sources will allow one to solve many problems of neutron diagnostics, monitor nano-and biological objects, and carry out radiation testing and modification of volumetric properties of materials at the industrial level. Such sources will considerably (up to 100 times) improve the accuracy of neutron physics experiments and will provide a better understanding of the structure of matter, including that of the neutron itself.

  16. Dibaryons in neutron stars

    NASA Technical Reports Server (NTRS)

    Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

    1991-01-01

    The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

  17. Neutron-capture nucleosynthesis in the first stars

    SciTech Connect

    Roederer, Ian U.; Preston, George W.; Thompson, Ian B.; Shectman, Stephen A.; Sneden, Christopher

    2014-04-01

    Recent studies suggest that metal-poor stars enhanced in carbon but containing low levels of neutron-capture elements may have been among the first to incorporate the nucleosynthesis products of the first generation of stars. We have observed 16 stars with enhanced carbon or nitrogen using the MIKE Spectrograph on the Magellan Telescopes at Las Campanas Observatory and the Tull Spectrograph on the Smith Telescope at McDonald Observatory. We present radial velocities, stellar parameters, and detailed abundance patterns for these stars. Strontium, yttrium, zirconium, barium, europium, ytterbium, and other heavy elements are detected. In four stars, these heavy elements appear to have originated in some form of r-process nucleosynthesis. In one star, a partial s-process origin is possible. The origin of the heavy elements in the rest of the sample cannot be determined unambiguously. The presence of elements heavier than the iron group offers further evidence that zero-metallicity rapidly rotating massive stars and pair instability supernovae did not contribute substantial amounts of neutron-capture elements to the regions where the stars in our sample formed. If the carbon- or nitrogen-enhanced metal-poor stars with low levels of neutron-capture elements were enriched by products of zero-metallicity supernovae only, then the presence of these heavy elements indicates that at least one form of neutron-capture reaction operated in some of the first stars.

  18. Arsenic activation neutron detector

    DOEpatents

    Jacobs, E.L.

    1980-01-28

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

  19. Arsenic activation neutron detector

    DOEpatents

    Jacobs, Eddy L.

    1981-01-01

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

  20. Perforated diode neutron sensors

    NASA Astrophysics Data System (ADS)

    McNeil, Walter J.

    A novel design of neutron sensor was investigated and developed. The perforated, or micro-structured, diode neutron sensor is a concept that has the potential to enhance neutron sensitivity of a common solid-state sensor configuration. The common thin-film coated diode neutron sensor is the only semiconductor-based neutron sensor that has proven feasible for commercial use. However, the thin-film coating restricts neutron counting efficiency and severely limits the usefulness of the sensor. This research has shown that the perforated design, when properly implemented, can increase the neutron counting efficiency by greater than a factor of 4. Methods developed in this work enable detectors to be fabricated to meet needs such as miniaturization, portability, ruggedness, and adaptability. The new detectors may be used for unique applications such as neutron imaging or the search for special nuclear materials. The research and developments described in the work include the successful fabrication of variant perforated diode neutron detector designs, general explanations of fundamental radiation detector design (with added focus on neutron detection and compactness), as well as descriptive theory and sensor design modeling useful in predicting performance of these unique solid-state radiation sensors. Several aspects in design, fabrication, and operational performance have been considered and tested including neutron counting efficiency, gamma-ray response, perforation shapes and depths, and silicon processing variations. Finally, the successfully proven technology was applied to a 1-dimensional neutron sensor array system.

  1. Advanced neutron absorber materials

    DOEpatents

    Branagan, Daniel J.; Smolik, Galen R.

    2000-01-01

    A neutron absorbing material and method utilizing rare earth elements such as gadolinium, europium and samarium to form metallic glasses and/or noble base nano/microcrystalline materials, the neutron absorbing material having a combination of superior neutron capture cross sections coupled with enhanced resistance to corrosion, oxidation and leaching.

  2. LGB neutron detector

    NASA Astrophysics Data System (ADS)

    Quist, Nicole

    2012-10-01

    The double pulse signature of the Gadolinium Lithium Borate Cerium doped plastic detector suggests its effectiveness for analyzing neutrons while providing gamma ray insensitivity. To better understand this detector, a californium gamma/neutron time of flight facility was constructed in our lab. Reported here are efforts to understand the properties and applications of the LGB detector with regards to neutron spectroscopy.

  3. Young Massive Clusters in the Galactic Center

    NASA Astrophysics Data System (ADS)

    Figer, D. F.

    2004-12-01

    The three young clusters in the Galactic Center represent the closest examples of massive starbursts and they define the upper mass limit of the Galactic cluster mass functions. In this review, I describe the characteristics and content of the Arches, Quintuplet, and Central clusters. They each are more massive than any other cluster in the Galaxy, and the Arches cluster, in particular, has a mass and age that make it ideal for studies of massive stellar evolution and dense stellar systems. A preliminary measurement indicates that the initial mass function in the Galactic center is top-heavy, suggesting an environmental effect that has otherwise been absent in similar observations for Galactic clusters. Given the relatively more evolved nature of the Quintuplet and Central clusters, these clusters contain stars in a wide range of evolutionary states, including Luminous Blue Variables and Wolf-Rayet stars. The Quintuplet cluster provides a particularly interesting view of the most massive stars that are known, the Pistol Star and FMM362. An analysis of the mass spectrum in the Arches cluster suggests an upper mass cutoff of ˜150-200 M⊙.

  4. Star Cluster Buzzing With Pulsars

    NASA Astrophysics Data System (ADS)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  5. Gravity-driven clustering of inertial particles in turbulence.

    PubMed

    Park, Yongnam; Lee, Changhoon

    2014-06-01

    We report a different kind of particle clustering caused purely by gravity, discovered in our simulation of particle-laden turbulence. Clustering in a vertical strip pattern forms when strong gravity acts on heavy particles. This phenomenon is explained by the skewness of the flow velocity gradient in the gravitational direction experienced by particles, which causes horizontal convergence of particles.

  6. Neutronic calculations for a final focus system

    NASA Astrophysics Data System (ADS)

    Mainardi, E.; Premuda, F.; Lee, E.

    2001-05-01

    For heavy-ion fusion and for "liquid-protected" reactor designs such as HYLIFE-II (Moir et al., Fusion Technol. 25 (1994); HYLIFE-II-Progress Report, UCID-21816, 4-82-100), a mixture of molten salts made of F 10, Li 6, Li 7, Be 9 called flibe allows highly compact target chambers. Smaller chambers will have lower costs and will allow the final-focus magnets to be closer to the target with decreased size of the focus spot and of the driver, as well as drastically reduced costs of IFE electricity. Consequently the superconducting coils of the magnets closer to the chamber will suffer higher radiation damage though they can stand only a certain amount of energy deposited before quenching. The scope of our calculations is essentially the total energy deposited on the magnetic lens system by fusion neutrons and induced γ-rays. Such a study is important for the design of the final focus system itself from the neutronic point of view and indicates some guidelines for a design with six magnets in the beam line. The entire chamber consists of 192 beam lines to provide access of heavy ions that will implode the pellet. A 3-D transport calculation of the radiation penetrating through ducts that takes into account the complexity of the system, requires Monte Carlo methods. The development of efficient and precise models for geometric representation and nuclear analysis is necessary. The parameters are optimized thanks to an accurate analysis of six geometrical models that are developed starting from the simplest. Different configurations are examined employing TART 98 (D.E. Cullen, Lawrence Livermore National Laboratory, UCRL-ID-126455, Rev. 1, November, 1997) and MCNP 4B (Briesmeister (Ed.), Version 4B, La-12625-m, March 1997, Los Alamos National Laboratory): two Monte Carlo codes for neutrons and photons. The quantities analyzed include: energy deposited by neutrons and gamma photons, values of the total fluence integrated on the whole energy range, neutron fluence spectrum

  7. Neutron scatter camera

    DOEpatents

    Mascarenhas, Nicholas; Marleau, Peter; Brennan, James S.; Krenz, Kevin D.

    2010-06-22

    An instrument that will directly image the fast fission neutrons from a special nuclear material source has been described. This instrument can improve the signal to background compared to non imaging neutron detection techniques by a factor given by ratio of the angular resolution window to 4.pi.. In addition to being a neutron imager, this instrument will also be an excellent neutron spectrometer, and will be able to differentiate between different types of neutron sources (e.g. fission, alpha-n, cosmic ray, and D-D or D-T fusion). Moreover, the instrument is able to pinpoint the source location.

  8. PERSONNEL NEUTRON DOSIMETER

    DOEpatents

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

    1960-05-24

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

  9. Organic metal neutron detector

    DOEpatents

    Butler, Michael A.; Ginley, David S.

    1987-01-01

    A device for detecting neutrons comprises a layer of conductive polymer sandwiched between electrodes, which may be covered on each face with a neutron transmissive insulating material layer. Conventional electrodes are used for a non-imaging integrating total neutron fluence-measuring embodiment, while wire grids are used in an imaging version of the device. The change in conductivity of the polymer after exposure to a neutron flux is determined in either case to provide the desired data. Alternatively, the exposed conductive polymer layer may be treated with a chemical reagent which selectively binds to the sites altered by neutrons to produce an image of the flux detected.

  10. Grazing incidence neutron optics

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)

    2012-01-01

    Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20 .ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.

  11. Grazing Incidence Neutron Optics

    NASA Technical Reports Server (NTRS)

    Gubarev, Mikhail V. (Inventor); Ramsey, Brian D. (Inventor); Engelhaupt, Darell E. (Inventor)

    2013-01-01

    Neutron optics based on the two-reflection geometries are capable of controlling beams of long wavelength neutrons with low angular divergence. The preferred mirror fabrication technique is a replication process with electroform nickel replication process being preferable. In the preliminary demonstration test an electroform nickel optics gave the neutron current density gain at the focal spot of the mirror at least 8 for neutron wavelengths in the range from 6 to 20.ANG.. The replication techniques can be also be used to fabricate neutron beam controlling guides.

  12. Neutron activation analysis system

    DOEpatents

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

    1973-12-25

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

  13. The Sensitivity of r-PROCESS Nucleosynthesis to the Properties of Neutron-Rich Nuclei

    NASA Astrophysics Data System (ADS)

    Surman, R.; Mumpower, M. R.; Cass, J.; Aprahamian, A.

    2014-09-01

    About half of the heavy elements in the Solar System were created by rapid neutron capture, or r-process, nucleosynthesis. In the r-process, heavy elements are built up via a sequence of neutron captures and beta decays in which an intense neutron flux pushes material out towards the neutron drip line. The nuclear network simulations used to test potential astrophysical scenarios for the r-process therefore require nuclear physics data (masses, beta decay lifetimes, neutron capture rates, fission probabilities) for thousands of nuclei far from stability. Only a small fraction of this data has been experimentally measured. Here we discuss recent sensitivity studies that aim to determine the nuclei whose properties are most crucial for r-process calculations.

  14. Nuclear and neutron matter studies

    SciTech Connect

    Wiringa, R.B.; Akmal, A.; Pandharipande, V.R.

    1995-08-01

    We are studying nuclear and neutron matter with the new Argonne v{sub 18} NN and Urbana 3N potentials. We use variational wave functions and a diagrammatic cluster expansion with Fermi hypernetted and single-operator chain (FHNC/SOC) integral equations to evaluate the energy expectation value. Initial results show some interesting differences with our previous calculations with the older Argonne v{sub 14} potential. In particular, there are a number of diagrams involving L{center_dot}S and L{sup 2} terms which were small with the older model and were rather crudely estimated or even neglected. It appears that these terms are more important with the new potential and will have to be evaluated more accurately. Work on this subject is in progress. A simple line of attack is to just add additional diagrams at the three-body cluster level. A longer term approach may be to adapt some of the methods for evaluating nucleon clusters used in the few-body and closed shell nuclei described above.

  15. NEUTRON DENSITY CONTROL IN A NEUTRONIC REACTOR

    DOEpatents

    Young, G.J.

    1959-06-30

    The method and means for controlling the neutron density in a nuclear reactor is described. It describes the method and means for flattening the neutron density distribution curve across the reactor by spacing the absorbing control members to varying depths in the central region closer to the center than to the periphery of the active portion of the reactor to provide a smaller neutron reproduction ratio in the region wherein the members are inserted, than in the remainder of the reactor thereby increasing the over-all potential power output.

  16. Neutron detection by scintillation of noble-gas excimers

    NASA Astrophysics Data System (ADS)

    McComb, Jacob Collin

    Neutron detection is a technique essential to homeland security, nuclear reactor instrumentation, neutron diffraction science, oil-well logging, particle physics and radiation safety. The current shortage of helium-3, the neutron absorber used in most gas-filled proportional counters, has created a strong incentive to develop alternate methods of neutron detection. Excimer-based neutron detection (END) provides an alternative with many attractive properties. Like proportional counters, END relies on the conversion of a neutron into energetic charged particles, through an exothermic capture reaction with a neutron absorbing nucleus (10B, 6Li, 3He). As charged particles from these reactions lose energy in a surrounding gas, they cause electron excitation and ionization. Whereas most gas-filled detectors collect ionized charge to form a signal, END depends on the formation of diatomic noble-gas excimers (Ar*2, Kr*2,Xe* 2) . Upon decaying, excimers emit far-ultraviolet (FUV) photons, which may be collected by a photomultiplier tube or other photon detector. This phenomenon provides a means of neutron detection with a number of advantages over traditional methods. This thesis investigates excimer scintillation yield from the heavy noble gases following the boron-neutron capture reaction in 10B thin-film targets. Additionally, the thesis examines noble-gas excimer lifetimes with relationship to gas type and gas pressure. Experimental data were collected both at the National Institute of Standards and Technology (NIST) Center for Neutron Research, and on a newly developed neutron beamline at the Maryland University Training Reactor. The components of the experiment were calibrated at NIST and the University of Maryland, using FUV synchrotron radiation, neutron imaging, and foil activation techniques, among others. Computer modeling was employed to simulate charged-particle transport and excimer photon emission within the experimental apparatus. The observed excimer

  17. Neutron conversion and cascaded cooling in paramagnetic systems for a high-flux source of very cold neutrons

    NASA Astrophysics Data System (ADS)

    Zimmer, Oliver

    2016-03-01

    A new neutron-cooling mechanism is proposed with potential benefits for novel intense sources of very cold neutrons with wavelengths >2 nm, and for enhancing the production of ultracold neutrons. It employs inelastic magnetic scattering in weakly absorbing, cold paramagnetic systems. Kinetic energy is removed from the neutron stepwise in constant decrements determined by the Zeeman energy of paramagnetic atoms or ions in an external magnetic field, or by zero-field level splittings in magnetic molecules. The stationary neutron transport equation is analyzed for an infinite, homogeneous medium with Maxwellian neutron sources, using inelastic scattering cross sections derived in an appendix. Nonmagnetic inelastic scattering processes are neglected. The solution therefore still underestimates very cold neutron densities that should be achievable in a real medium. Molecular oxygen with its triplet ground state appears particularly promising, notably as a host in fully deuterated O2-clathrate hydrate. Other possibilities are dry O2-4He van der Waals clusters and O2 intercalated in fcc-C60. For conversion of cold to ultracold neutrons, where an incident neutron imparts only a single energy quantum to the medium, the paramagnetic scattering in the clathrate system is found to be stronger, by more than an order of magnitude, than the single-phonon emission in superfluid helium, when evaluated for an incident neutron spectrum with the optimum temperature for the respective medium. Moreover, the multistep paramagnetic cooling cascade leads to further strong enhancements of very cold neutron densities, e.g., by a factor 14 (57) for an initial neutron temperature of 30 K (100 K ), for the moderator held at about 1.3 K . Due to a favorable Bragg cutoff of the O2 clathrate, the cascade-cooling can take effect in a moderator with linear extensions smaller than a meter.

  18. Cosmic Ray Neutron Flux Measurements

    NASA Astrophysics Data System (ADS)

    Dayananda, Mathes

    2009-11-01

    Cosmic rays are high-energetic particles originating from outer space that bombard the upper atmosphere of the Earth. Almost 90% of cosmic ray particles consist of protons, electrons and heavy ions. When these particles hit the Earth's atmosphere, cascade of secondary particles are formed. The most abundant particles reach to the surface of the Earth are muons, electrons and neutrons. In recent years many research groups are looking into potential applications of the effects of cosmic ray radiation at the surface of the Earth [1, 2]. At Georgia State University we are working on a long-term measurement of cosmic ray flux distribution. This study includes the simultaneous measurement of cosmic ray muons, neutrons and gamma particles at the Earth surface in downtown Atlanta. The initial effort is focusing on the correlation studies of the cosmic ray particle flux distribution and the atmospheric weather conditions. In this presentation, I will talk about the development of a cosmic ray detector using liquid scintillator and the preliminary results. [4pt] [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, ``Radiographic imaging with cosmic-ray muons'', Nature, Vol.422, p.277, Mar.2003[0pt] [2] Svensmark Henrik, Physical Review 81, 3, (1998)

  19. Calculated shielding characteristics of eight materials for neutrons and secondary photons produced by monoenergetic source neutrons with energies less than 400 MeV

    SciTech Connect

    Nakanishi, Noriyoshi; Shikata, Takashi; Fujita, Shin; Kosako, Toshiso

    1995-10-01

    Shielding characteristics of iron, lead, ordinary concrete, heavy concrete, graphite, marble, water, and paraffin were calculated for monoenergetic source neutrons with energies < 400 MeV. The depth dependence of neutron and secondary photon transmitted dose equivalents at the exit surfaces of shields of varying thickness is exhibited for some monoenergetic source neutrons and for each material. Their shielding characteristics are compared and discussed in terms of the degradation process of neutron energy and the change of neutron spectrum in typical shielding materials. Calculations were carried out by using the one-dimensional discrete ordinates code ANISN-JR and the cross-section library DLC-87/HILO. Systematic knowledge concerning the shielding of neutrons with energies < 400 MeV was successfully obtained.

  20. Measurement of the Neutron Radius of 208Pb Through Parity-Violation in Electron Scattering

    DOE PAGES

    Abrahamyan, Sergey; Albataineh, Hisham; Aniol, Konrad; Armstrong, David; Armstrong, Whitney; Averett, Todd; Babineau, Benjamin; Barbieri, A.; Bellini, Vincenzo; Beminiwattha, Rakitha; et al

    2012-03-15

    We report the first measurement of the parity-violating asymmetry APV in the elastic scattering of polarized electrons from 208Pb. APV is sensitive to the radius of the neutron distribution (Rn). The result APV = 0.656 ± 0.060 (stat) ± 0.013 (syst) corresponds to a difference between the radii of the neutron and proton distributions Rn-Rp = 0.33-0.18+0.16 fm and provides the first electroweak observation of the neutron skin which is expected in a heavy, neutron-rich nucleus.

  1. Cubic potential models for cluster radioactivity

    NASA Astrophysics Data System (ADS)

    Shanmugam, G.

    1999-09-01

    Cluster radioactivity is a process by which nuclei equal and heavier than the a-particleis emitted spontaneously. The clusters usually emitted in this process are the a-particle, carbon, oxygen, neon, magnesium, silicon etc. When the mass of the cluster becomes comparable with the mass of the daughter, symmetric fission takes place. Thus the cluster radioactivity is an intermediate process between the well known a-decay and the spontaneous fission. In earlier years such cluster radioactivity was found mostly in actinide nuclei like radium, uranium etc. Very recently it has been predicted that such decays are possible in a new region around 114Ba. There has been an exciting experimental detection of the emission of 12C from 114Ba leading to 102Sn, which is attracting a lot of attention recently. To study the phenomenon of cluster radioactivity there are various theoretical models in vogue. The existing models generally fall under two categories: the unified fission model (UFM) and the preformed cluster model (PCM). The physics of the UFM and the PCM are completely different. The UFM considers cluster radioactivity simply as a barrier penetration phenomenon in between the fission and the a-decay without worrying about the cluster being or not being preformed in the parent nucleus. In the PCM clusters are assumed to be preborn in a parent nucleus before they could penetrate the potential barrier with a given Q-value. The basic assumption of the UFM is that heavy clusters as well as the a-particle have equal probability of being preformed. In PCM, clusters of different sizes have different probabilities of their being preformed in the parent nucleus. We have developed three fission models during the last decade using the cubic potential for the pre-scission region. The use of these models in the study of cluster radioactivity in both the actinide and barium regions will be discussed in this talk in comparison with the other existing theories.

  2. Final Report for the “WSU Neutron Capture Therapy Facility Support”

    SciTech Connect

    Gerald E. Tripard; Keith G. Fox

    2006-08-24

    The objective for the cooperative research program for which this report has been written was to provide separate NCT facility user support for the students, faculty and scientists who would be doing the U.S. Department of Energy Office (DOE) of Science supported advanced radiotargeted research at the WSU 1 megawatt TRIGA reactor. The participants were the Idaho National laboratory (INL, P.I., Dave Nigg), the Veterinary Medical Research Center of Washington State University (WSU, Janean Fidel and Patrick Gavin), and the Washington State University Nuclear Radiation Center (WSU, P.I., Gerald Tripard). A significant number of DOE supported modifications were made to the WSU reactor in order to create an epithermal neutron beam while at the same time maintaining the other activities of the 1 MW reactor. These modifications were: (1) Removal of the old thermal column. (2) Construction and insertion of a new epithermal filter, collimator and shield. (3) Construction of a shielded room that could accommodate the very high radiation field created by an intense neutron beam. (4) Removal of the previous reactor core fuel cluster arrangement. (5) Design and loading of the new reactor core fuel cluster arrangement in order to optimize the neutron flux entering the epithermal neutron filter. (6) The integration of the shielded rooms interlocks and radiological controls into the SCRAM chain and operating electronics of the reactor. (7) Construction of a motorized mechanism for moving and remotely controlling the position of the entire reactor bridge. (8) The integration of the reactor bridge control electronics into the SCRAM chain and operating electronics of the reactor. (9) The design, construction and attachment to the support structure of the reactor of an irradiation box that could be inserted into position next to the face of the reactor. (Necessitated by the previously mentioned core rearrangement). All of the above modifications were successfully completed and tested

  3. Faster Heavy Ion Transport for HZETRN

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.

    2013-01-01

    The deterministic particle transport code HZETRN was developed to enable fast and accurate space radiation transport through materials. As more complex transport solutions are implemented for neutrons, light ions (Z < 2), mesons, and leptons, it is important to maintain overall computational efficiency. In this work, the heavy ion (Z > 2) transport algorithm in HZETRN is reviewed, and a simple modification is shown to provide an approximate 5x decrease in execution time for galactic cosmic ray transport. Convergence tests and other comparisons are carried out to verify that numerical accuracy is maintained in the new algorithm.

  4. Cluster headache

    PubMed Central

    2010-01-01

    Introduction The revised International Headache Society (IHS) criteria for cluster headache are: attacks of severe or very severe, strictly unilateral pain, which is orbital, supraorbital, or temporal pain, lasting 15 to 180 minutes and occurring from once every other day to eight times daily. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions to abort cluster headache? What are the effects of interventions to prevent cluster headache? We searched: Medline, Embase, The Cochrane Library, and other important databases up to June 2009 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations, such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 23 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: baclofen (oral); botulinum toxin (intramuscular); capsaicin (intranasal); chlorpromazine; civamide (intranasal); clonidine (transdermal); corticosteroids; ergotamine and dihydroergotamine (oral or intranasal); gabapentin (oral); greater occipital nerve injections (betamethasone plus xylocaine); high-dose and high-flow-rate oxygen; hyperbaric oxygen; leuprolide; lidocaine (intranasal); lithium (oral); melatonin; methysergide (oral); octreotide (subcutaneous); pizotifen (oral); sodium valproate (oral); sumatriptan (oral, subcutaneous, and intranasal); topiramate (oral); tricyclic antidepressants (TCAs); verapamil; and zolmitriptan (oral and intranasal). PMID:21718584

  5. Dynamical processes in heavy ion reactions

    SciTech Connect

    Blann, M.; Remington, B.A.

    1988-07-25

    In this report I review the physical assumptions of the Boltzmann Master Equation (BME). Comparisons of the model with experimental neutron spectra gated on evaporation residues for a range of incident projectile energies and masses are presented; next, I compare n spectra gated on projectile-like fragments, followed by comparisons with ungated, inclusive proton spectra. I will then consider secondary effects from the nucleon-nucleon processes involved in the heavy ion relaxation processes, specifically the high energy ..gamma..-rays which have been observed at energies up to 140 MeV in collisions of heavy ions of 20/endash/84 MeV/..mu... Another secondary effect, subthreshold pion production, was covered in the XVII School and will not be repeated. 39 refs., 16 figs.

  6. Removal of gadolinium nitrate from heavy water

    SciTech Connect

    Wilde, E.W.

    2000-03-22

    Work was conducted to develop a cost-effective process to purify 181 55-gallon drums containing spent heavy water moderator (D2O) contaminated with high concentrations of gadolinium nitrate, a chemical used as a neutron poison during former nuclear reactor operations at the Savannah River Site (SRS). These drums also contain low level radioactive contamination, including tritium, which complicates treatment options. Presently, the drums of degraded moderator are being stored on site. It was suggested that a process utilizing biological mechanisms could potentially lower the total cost of heavy water purification by allowing the use of smaller equipment with less product loss and a reduction in the quantity of secondary waste materials produced by the current baseline process (ion exchange).

  7. Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

    PubMed

    Shan, Qing; Chu, Shengnan; Jia, Wenbao

    2015-11-01

    Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer. PMID:26325583

  8. Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

    PubMed

    Shan, Qing; Chu, Shengnan; Jia, Wenbao

    2015-11-01

    Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer.

  9. Enhanced E1 transitions and {alpha}-clustering in {sup 212}Po

    SciTech Connect

    Suzuki, Y.; Ohkubo, S.

    2011-05-06

    An {alpha}+{sup 208}Pb(0{sup +},3{sup -}) cluster model explains the recently observed enhanced E1 transitions from the new negative-parity levels to the yrast states in {sup 212}Po. Heavy and light nuclei present good examples of surface clustering and well-localized clustering.

  10. Neutron chopper development at LANSCE

    SciTech Connect

    Nutter, M.; Lewis, L.; Tepper, S.; Silver, R.N.; Heffner, R.H.

    1985-01-01

    Progress is reported on neutron chopper systems for the Los Alamos Neutron Scattering Center pulsed spallation neutron source. This includes the development of 600+ Hz active magnetic bearing neutron chopper and a high speed control system designed to operate with the Proton Storage Ring to phase the chopper to the neutron source. 5 refs., 3 figs.

  11. Neutron metrology laboratory facility simulation.

    PubMed

    Pereira, Mariana; Salgado, Ana P; Filho, Aidano S; Pereira, Walsan W; Patrão, Karla C S; Fonseca, Evaldo S

    2014-10-01

    The Neutron Low Scattering Laboratory in Brazil has been completely rebuilt. Evaluation of air attenuation parameters and neutron component scattering in the room was done using Monte Carlo simulation code. Neutron fields produced by referenced neutron source were used to calculate neutron scattering and air attenuation.

  12. Neutron metrology laboratory facility simulation.

    PubMed

    Pereira, Mariana; Salgado, Ana P; Filho, Aidano S; Pereira, Walsan W; Patrão, Karla C S; Fonseca, Evaldo S

    2014-10-01

    The Neutron Low Scattering Laboratory in Brazil has been completely rebuilt. Evaluation of air attenuation parameters and neutron component scattering in the room was done using Monte Carlo simulation code. Neutron fields produced by referenced neutron source were used to calculate neutron scattering and air attenuation. PMID:24864318

  13. Spectroscopy of the Perseus Cluster

    NASA Technical Reports Server (NTRS)

    Jones, Christine; Mushotzky, Richard F. (Technical Monitor)

    2004-01-01

    We present preliminary results of a XMM-Newton 50 ks observation of the Perseus Cluster that provides an unprecedented view of the central 0.5 Mpc region. The projected gas temperature declines smoothly by a factor of 2 from a maximum value of approx. 7 keV in the outer regions to just above 3 keV at the cluster center. Over this same range, the heavy-element abundance rises slowly from 0.4 to 0.5 solar as the radius decreases from 14 ft. to 5 ft., and then it rises to a peak of almost 0.7 solar at 1&farcm;25 before declining to 0.4 at the center. Th global east-west asymmetry of the gas temperature and surface brightness distributions, approximately aligned with the chain of bright galaxies, suggests an ongoing merger, although the modest degree of the observed asymmetry certainly excludes a major merger interpretation. The chain of galaxies probably traces the filament along which accretion started some time ago and is continuing at the present time. A cold and dense (low-entropy) cluster core like Perseus is probably well "protected" against the penetration of the gas of infalling groups and poor clusters, whereas in non-cooling core clusters such as Coma and A1367, infalling subclusters can penetrate deeply into the core region. In Perseus, gas associated with infalling groups may be stripped completely at the outskirts of the main cluster and only compression waves (shocks) may reach the central regions. We argue, and show supporting simulations, that the passage of such a wave(s) can qualitatively explain the overall horseshoe shaped appearance of the gas temperature map (the hot horseshoe surrounds the colder, low-entropy core) as well as other features of the Perseus Cluster core. These simulations also show that as compression waves traverse the cluster core, they can induce oscillatory motion of the cluster gas that can generate multiple sharp "edges" on opposite sides of the central galaxy. Gas motions induced by mergers may be a natural way to explain

  14. Cluster decay half-lives of trans-lead nuclei within the Coulomb and proximity potential model

    NASA Astrophysics Data System (ADS)

    Santhosh, K. P.; Priyanka, B.; Unnikrishnan, M. S.

    2012-09-01

    Within the Coulomb and proximity potential model (CPPM) the cluster decay process in 199-226Fr, 206-232Ac, 209-237Th, 212-238Pa, 217-241U, 225-242Np, 225-244Pu, 231-246Am, 202-230Ra and 233-249Cm isotopes leading to the doubly magic 208Pb and neighboring nuclei are studied. The computed half-lives are compared with available experimental data and are in good agreement with each other. The half-lives are also computed using the Universal formula for cluster decay (UNIV) of Poenaru et al., Universal Decay Law (UDL) and the Scaling Law of Horoi et al., and their comparisons with CPPM values are found to be in agreement. The calculations for the emission of 22O from the parent 209-237Th, 20O from the parents 202-230Ra and 217-240U, were the experimental values are not available are also done. It is found that most of the decay modes are favorable for measurement (T<1030 s), and this observation will serve as a guide to the future experiments. The odd-even staggering (OES) are found to be more prominent in the emission of odd mass clusters. The Geiger-Nuttall plots of log10(T) versus Q for various clusters ranging from C14 to Si34 from different isotopes of heavy parent nuclei with atomic numbers within the range 87⩽Z⩽96 have been studied and are found to be linear. Our study reveals the role of doubly magic Pb208 daughter nuclei in cluster decay process and also reveal the fact that the role of neutron shell closure is crucial than proton shell closure.

  15. Effective moment of inertia for several fission reaction systems induced by nucleons, light particles, and heavy ions

    NASA Astrophysics Data System (ADS)

    Soheyli, S.

    2011-10-01

    The effective moment of inertia of the compound nucleus is calculated for several fission reaction systems induced by nucleons, light particles, and heavy ions. The determination of this quantity for these systems is based upon the comparison between the experimental data of the fission fragment angular distributions as well as the prediction of the standard saddle-point statistical model. For the systems, the two cases, namely with and without neutron emission corrections, were considered. Afterward, our theoretical results are compared with the data obtained from the rotational liquid drop model as well as the Sierk model and satisfactory agreements were found. We also calculated the quadrupole deformation and mass asymmetry parameters of the fissioning nuclei at the saddle point by two methods, the first method is based on an ellipsoid shape assumption for the fissioning nucleus, and the other is based on dinuclear system model, since in heavy ion induced fission reactions, the compound nuclei which undergo fission can be considered as states of two touching clusters (dinuclear system). Afterward, the results of these two methods were compared and satisfactory agreements were found between them.

  16. Neutron sources and applications

    SciTech Connect

    Price, D.L.; Rush, J.J.

    1994-01-01

    Review of Neutron Sources and Applications was held at Oak Brook, Illinois, during September 8--10, 1992. This review involved some 70 national and international experts in different areas of neutron research, sources, and applications. Separate working groups were asked to (1) review the current status of advanced research reactors and spallation sources; and (2) provide an update on scientific, technological, and medical applications, including neutron scattering research in a number of disciplines, isotope production, materials irradiation, and other important uses of neutron sources such as materials analysis and fundamental neutron physics. This report summarizes the findings and conclusions of the different working groups involved in the review, and contains some of the best current expertise on neutron sources and applications.

  17. Advanced Neutron Sources: Plant Design Requirements

    SciTech Connect

    Not Available

    1990-07-01

    The Advanced Neutron Source (ANS) is a new, world class facility for research using hot, thermal, cold, and ultra-cold neutrons. At the heart of the facility is a 350-MW{sub th}, heavy water cooled and moderated reactor. The reactor is housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides fans out into a large guide hall, housing about 30 neutron research stations. Office, laboratory, and shop facilities are included to provide a complete users facility. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory at the end of the decade. This Plant Design Requirements document defines the plant-level requirements for the design, construction, and operation of the ANS. This document also defines and provides input to the individual System Design Description (SDD) documents. Together, this Plant Design Requirements document and the set of SDD documents will define and control the baseline configuration of the ANS.

  18. The advanced neutron source reactor: An overview

    SciTech Connect

    West, C.D.

    1990-01-01

    The Advanced Neutron Source (ANS) will be a new user facility for all kinds of neutron research, including neutron scattering, materials testing, materials analysis, isotope production and nuclear physics experiments. The centerpiece of the facility is to be the world's highest flux beam reactor. There will be beams of hot, cold and thermal neutrons for more than 40 simultaneous scattering and nuclear physics experiments. In addition, there will be irradiation positions and rabbit tubes for in-pile experiments, testing and isotopes production (including transuranium isotopes). To reduce technical risks and to minimize safety issues, the reactor design is based on technology already employed in existing research reactors. The fuel elements are annular assemblies of aluminum clad involute fuel plates, similar to the design of the High Flux Isotope Reactor (HFIR) at Oak Ridge and the Institut Laue-Langevin (ILL) Reactor in Grenoble. As is common with many other research reactors, the core is cooled, moderated and reflected by heavy water. The preferred fuel is U{sub 3}Si{sub 2} - a high-density fuel form developed by Argonne National Laboratory and Babcock and Wilcox that has been extensively tested in reactors in the United States, Europe and Japan. 7 figs., 2 tabs.

  19. The Fascinating World of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Piekarewicz, J.

    2009-07-01

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the EOS of cold baryonic matter with special emphasis on its impact on the structure and dynamics of neutron stars. In particular, I will discuss the many fascinating phases that one encounters in the journey from the low-density crust to the high-density core.

  20. The Fascinating World of Neutron Stars

    SciTech Connect

    Piekarewicz, J.

    2009-07-06

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the EOS of cold baryonic matter with special emphasis on its impact on the structure and dynamics of neutron stars. In particular, I will discuss the many fascinating phases that one encounters in the journey from the low-density crust to the high-density core.

  1. ATR neutron spectral characterization

    SciTech Connect

    Rogers, J.W.; Anderl, R.A.

    1995-11-01

    The Advanced Test Reactor (ATR) at INEL provides intense neutron fields for irradiation-effects testing of reactor material samples, for production of radionuclides used in industrial and medical applications, and for scientific research. Characterization of the neutron environments in the irradiation locations of the ATR has been done by means of neutronics calculations and by means of neutron dosimetry based on the use of neutron activation monitors that are placed in the various irradiation locations. The primary purpose of this report is to present the results of an extensive characterization of several ATR irradiation locations based on neutron dosimetry measurements and on least-squares-adjustment analyses that utilize both neutron dosimetry measurements and neutronics calculations. This report builds upon the previous publications, especially the reference 4 paper. Section 2 provides a brief description of the ATR and it tabulates neutron spectral information for typical irradiation locations, as derived from the more historical neutron dosimetry measurements. Relevant details that pertain to the multigroup neutron spectral characterization are covered in section 3. This discussion includes a presentation on the dosimeter irradiation and analyses and a development of the least-squares adjustment methodology, along with a summary of the results of these analyses. Spectrum-averaged cross sections for neutron monitoring and for displacement-damage prediction in Fe, Cr, and Ni are given in section 4. In addition, section4 includes estimates of damage generation rates for these materials in selected ATR irradiation locations. In section 5, the authors present a brief discussion of the most significant conclusions of this work and comment on its relevance to the present ATR core configuration. Finally, detailed numerical and graphical results for the spectrum-characterization analyses in each irradiation location are provided in the Appendix.

  2. Final Report on Actinide Glass Scintillators for Fast Neutron Detection

    SciTech Connect

    Bliss, Mary; Stave, Jean A.

    2012-10-01

    This is the final report of an experimental investigation of actinide glass scintillators for fast-neutron detection. It covers work performed during FY2012. This supplements a previous report, PNNL-20854 “Initial Characterization of Thorium-loaded Glasses for Fast Neutron Detection” (October 2011). The work in FY2012 was done with funding remaining from FY2011. As noted in PNNL-20854, the glasses tested prior to July 2011 were erroneously identified as scintillators. The decision was then made to start from “scratch” with a literature survey and some test melts with a non-radioactive glass composition that could later be fabricated with select actinides, most likely thorium. The normal stand-in for thorium in radioactive waste glasses is cerium in the same oxidation state. Since cerium in the 3+ state is used as the light emitter in many scintillating glasses, the next most common substitute was used: hafnium. Three hafnium glasses were melted. Two melts were colored amber and a third was clear. It barely scintillated when exposed to alpha particles. The uses and applications for a scintillating fast neutron detector are important enough that the search for such a material should not be totally abandoned. This current effort focused on actinides that have very high neutron capture energy releases but low neutron capture cross sections. This results in very long counting times and poor signal to noise when working with sealed sources. These materials are best for high flux applications and access to neutron generators or reactors would enable better test scenarios. The total energy of the neutron capture reaction is not the only factor to focus on in isotope selection. Many neutron capture reactions result in energetic gamma rays that require large volumes or high densities to detect. If the scintillator is to separate neutrons from gamma rays, the capture reactions should produce heavy particles and few gamma rays. This would improve the detection of a

  3. Introduction to neutron stars

    SciTech Connect

    Lattimer, James M.

    2015-02-24

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  4. Neutron Emission in Fission and Quasi-Fission

    NASA Astrophysics Data System (ADS)

    Itkis, I.; Bogatchev, A. A.; Chizhov, A. Yu.; Itkis, M. G.; Kliman, J.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Korzyukov, I. V.; Krupa, L.; Oganessian, Yu. Ts.; Pokrovski, I. V.; Prokhorova, E. V.; Sagaidak, R. N.; Voskressenski, V. M.; Rusanov, A. Ya.; Corradi, L.; Stefanini, A. M.; Trotta, M.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Chubarian, G.; Hanappe, F.; Materna, T.; Dorvaux, O.; Rowley, N.; Stuttge, L.; Giardina, G.

    2005-09-01

    The work presents the results of the study of characteristics of the neutron emission in fission and quasi-fission of heavy and super-heavy nuclei, produced in the reactions with heavy ions. These experiments have been performed at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR), tandem accelerator in Legnaro (LNL) and VIVITRON accelerator in Strasbourg (IReS) with the use of the time-of-flight spectrometer of fission fragments CORSET and neutron multidetector DEMON. Mass-energy distributions (MED) of the 48Ca + 168Er, 208Pb, 238U and 18O + 208Pb reactions products at energies close to and below the Coulomb barrier have been studied. The pre- and post-fission neutron multiplicities as a function of the fragment mass have been obtained. A significant yield of the asymmetric component observed in the fragment mass distributions in the case of 18O + 208Pb reaction denotes the multimodal nature of the fission process. At the same time an increase in the yield of fragment masses ML ≅ 75-85 and MH ≅ 200-210 in the case 48Ca+208Pb, 238U reactions and ML ≅ 75-85 and MH ≅ 130-140 in the case 48Ca+168Er is rather connected with a quasi-fission process. The obtained neutron multiplicities dependences on fragment masses showed the validity of these assumptions.

  5. Neutron-emission measurements at a white neutron source

    SciTech Connect

    Haight, Robert C

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  6. Physics and technology of spallation neutron sources

    NASA Astrophysics Data System (ADS)

    Bauer, G. S.

    2001-05-01

    A substantial body of research is necessary in order to be able to make reliable predictions on the performance and safety of Accelerator Driven Systems (ADS), in particular of their spallation targets. So far, practical experience has resulted from the development of research neutron sources only. Next to fission and fusion, spallation is an efficient process for releasing neutrons from nuclei. Unlike the other two reactions, it is an endothermal process and can, therefore, not be used per se in energy generation. In order to sustain a spallation reaction, an energetic beam of particles, most commonly protons, must be supplied onto a heavy target. Spallation can, however, play an important role as a source of neutrons whose flux can be easily controlled via the driving beam. Although sophisticated Monte Carlo codes exist to compute all aspects of a spallation facility, many features can be understood on the basis of simple physics arguments. Technically a spallation facility is very demanding, not only because a reliable and economic accelerator of high power is needed to drive the reaction, but also, and in particular, because high levels of radiation and heat are generated in the target which are difficult to cope with. Radiation effects in a spallation environment are different from those commonly encountered in a reactor and are probably even more temperature dependent than the latter because of the high gas production rate. A commonly favored solution is the use of molten heavy metal targets. While radiation damage is not a problem in this case, except for the container, other issues need to be considered. R&D carried out for the development of spallation neutron sources will thus be beneficial also directly for ADS.

  7. Small angle neutron scattering from nanometer grain sized materials

    SciTech Connect

    Epperson, J.E.; Siegel, R.W.

    1991-11-01

    Small angie neutron scattering has been utilized, along with a number of complementary characterization methods suitable to the nanometer size scale, to investigate the structures of cluster-assembled nanophase materials. Results of these investigations are described and problems and opportunities in using small angle scattering for elucidating nanostructures are discussed.

  8. Baryonic dark clusters in galactic halos and their observable consequences

    NASA Technical Reports Server (NTRS)

    Wasserman, Ira; Salpeter, Edwin E.

    1994-01-01

    We consider the possibility that approximately 10% of the mass of a typical galaxy halo is in the form of massive (approximately 10(exp 7) solar masses), compact (escape speeds approximately 100 km/s) baryonic clusters made of neutron stars (approximately 10% by mass), black holes (less than or approximately equal to 1%) and brown dwarfs, asteroids, and other low-mass debris (approximately 90%). These general properties are consistent with several different observational and phenomenological constraints on cluster properties subject to the condition that neutron stars comprise approximately 1% of the total halo mass. Such compact, dark clusters could be the sites of a variety of collisional phenomena involving neutron stars. We find that integrated out to the Hubble distance approximately one neutron star-neutron star or neutron star-black hole collision occurs daily. Of order 0.1-1 asteroid-neutron star collisions may also happen daily in the halo of the Milky Way if there is roughly equal cluster mass per logarithmic particle mass interval between asteroids and brown dwarfs. These event rates are comparable to the frequency of gamma-ray burst detections by the Burst and Transient Source Experiment (BATSE) on the Compton Observatory, implying that if dark halo clusters are the sites of most gamma-ray bursts, perhaps approximately 90% of all bursts are extragalactic, but approximately 10% are galactic. It is possible that dark clusters of the kind discussed here could be detected directly by the Infrared Space Observatory (ISO) or Space Infrared Telescope Facility (SIRTF). If the clusters considered in this paper exist, they should produce spatially correlated gravitational microlensing of stars in the Large Magellanic Cloud (LMC). If 10% of the halo is in the form of dark baryonic clusters, and the remaining 90% is in brown dwarfs and other dark objects which are either unclustered or collected into low-mass clusters, then we expect that two events within

  9. Heavy quark masses

    NASA Technical Reports Server (NTRS)

    Testa, Massimo

    1990-01-01

    In the large quark mass limit, an argument which identifies the mass of the heavy-light pseudoscalar or scalar bound state with the renormalized mass of the heavy quark is given. The following equation is discussed: m(sub Q) = m(sub B), where m(sub Q) and m(sub B) are respectively the mass of the heavy quark and the mass of the pseudoscalar bound state.

  10. Shell states of neutron-rich matter

    NASA Astrophysics Data System (ADS)

    Horowitz, C. J.; Shen, G.

    2008-07-01

    The equation of state (EOS) for nuclear and neutron rich matter is investigated in a relativistic mean field (RMF) model. New shell states are found that minimize the free energy per baryon, calculated in a spherical Wigner-Seitz (WS) approximation, over a significant range of baryon densities. These shell states, that have both inside and outside surfaces, minimize the Coulomb energy of large proton number configurations at the expense of a larger surface energy. This is related to a possible depression in the central density of super heavy nuclei. As the baryon density increases, we find the system changes from normal nuclei, to shell states, and then to uniform matter.

  11. Shell states of neutron-rich matter

    SciTech Connect

    Horowitz, C. J.; Shen, G.

    2008-07-15

    The equation of state (EOS) for nuclear and neutron rich matter is investigated in a relativistic mean field (RMF) model. New shell states are found that minimize the free energy per baryon, calculated in a spherical Wigner-Seitz (WS) approximation, over a significant range of baryon densities. These shell states, that have both inside and outside surfaces, minimize the Coulomb energy of large proton number configurations at the expense of a larger surface energy. This is related to a possible depression in the central density of super heavy nuclei. As the baryon density increases, we find the system changes from normal nuclei, to shell states, and then to uniform matter.

  12. Mutagenicity of heavy metals

    SciTech Connect

    Wong, P.K.

    1988-04-01

    Certain heavy metals are required, as trace elements for normal cellular functions. However, heavy metals are toxic to cells once their levels exceed their low physiological values. The toxicity of heavy metals on microorganisms, and on animals has been well-documented. These interactions may induce the alteration of the primary as well as secondary structures of the DNA and result in mutation(s). The present communication reports the results in determining the mutagenicity and carcinogenicity of ten heavy metals commonly found in polluted areas by using the Salmonella/mammalian-microsome mutagenicity test.

  13. Heavy-Quark Production

    NASA Astrophysics Data System (ADS)

    Frixione, Stefano; Mangano, Michelangelo L.; Nason, Paolo; Ridolfi, Giovanni

    The following sections are included: * INTRODUCTION * FIXED-TARGET PRODUCTION * Total cross sections * Single-inclusive distributions * Double-differential distributions * HEAVY-FLAVOUR PRODUCTION AT HERA * Photoproduction cross sections * Charm photoproduction * Bottom photoproduction * Deep-inelastic production * Future physics * Determination of f^{(p)}_{g} * Polarization asymmetries * HERA-B * HEAVY-QUARK PRODUCTION AT HADRON COLLIDERS * Inclusive bottom production * Preliminaries * The effect of higher-order corrections * Comparison with experimental results * boverline{b} correlations * Heavy-quark jets in perturbative QCD * Preliminaries * The structure of heavy-quark jets at the Tevatron * Associated production of heavy quarks with W or γ * Photon plus heavy quarks * W bosons plus heavy quarks * Production of top quarks * Total toverline{t} production cross sections * Top kinematical distributions * HIGHER ORDERS AND RESUMMATION * What are soft-gluon effects * Problems with the x-space resummation formula * Phenomenological applications * HEAVY-FLAVOUR PRODUCTION IN e+e- COLLISIONS * Preliminaries * Fragmentation function * Heavy-quark production via gluon splitting * Correlations * CONCLUSIONS AND OUTLOOK * Acknowledgements * REFERENCES

  14. The Advanced Neutron Source (ANS) project: A world-class research reactor facility

    SciTech Connect

    Thompson, P.B.; Meek, W.E.

    1993-07-01

    This paper provides an overview of the Advanced Neutron Source (ANS), a new research facility being designed at Oak Ridge National Laboratory. The facility is based on a 330 MW, heavy-water cooled and reflected reactor as the neutron source, with a thermal neutron flux of about 7.5{times}10{sup 19}m{sup {minus}2}{center_dot}sec{sup {minus}1}. Within the reflector region will be one hot source which will serve 2 hot neutron beam tubes, two cryogenic cold sources serving fourteen cold neutron beam tubes, two very cold beam tubes, and seven thermal neutron beam tubes. In addition there will be ten positions for materials irradiation experiments, five of them instrumented. The paper touches on the project status, safety concerns, cost estimates and scheduling, a description of the site, the reactor, and the arrangements of the facilities.

  15. Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

    NASA Astrophysics Data System (ADS)

    Khodel, V. A.; Clark, J. W.; Shaginyan, V. R.; Zverev, M. V.

    2014-09-01

    The nature of pairing correlations in neutron matter is re-examined. Working within the conventional approximation in which the nn pairing interaction is provided by a realistic bare nn potential fitted to scattering data, it is demonstrated that the standard BCS theory fails in regions of neutron number density, where the pairing constant λ, depending crucially on density, has a non-BCS negative sign. We are led to propose a non-BCS scenario for pairing phenomena in neutron matter that involves the formation of a hidden dineutron state. In low-density neutron matter, where the pairing constant has the standard BCS sign, two phases organized by pairing correlations are possible and compete energetically: a conventional BCS phase and a dineutron phase. In dense neutron matter, where λ changes sign, only the dineutron phase survives and exists until the critical density for termination of pairing correlations is reached at approximately twice the neutron density in heavy atomic nuclei.

  16. Final report on Seed Money Project 3210-0346: Feasibility study for californium cold neutron source

    SciTech Connect

    Alsmiller, R.G.; Henderson, D.L.; Montgomery, B.H.

    1988-10-01

    A study has been completed of the feasibility and cost of building a cold neutron source that is not dependent on a reactor or accelerator. The neutron source is provided by up to ten /sup 252/Cf capsules, each containing 50 mg of the isotope produced in the High-Flux Isotope Reactor. The neutrons are moderated by heavy water and liquid deuterium to attain, in practice, a peak cold neutron flux of 1.4 /times/ 10/sup 13/ neutrons/(m/sup 2//center dot/s). The new facility would be located in the TURF Californium Facility. The estimated cost of the Californium Cold Neutron Source Facility is $6.5 million. 6 figs., 1 tab.

  17. Preliminary study of MAGAT polymer gel dosimetry for boron-neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Hayashi, Shin-ichiro; Sakurai, Yoshinori; Uchida, Ryohei; Suzuki, Minoru; Usui, Shuji; Tominaga, Takahiro

    2015-01-01

    MAGAT gel dosimeter with boron is irradiated in Heavy Water Neutron Irradiation Facility (HWNIF) of Kyoto University Research Reactor (KUR). The cylindrical gel phantoms are exposed to neutron beams of three different energy spectra (thermal neutron rich, epithermal and fast neutron rich and the mixed modes) in air. Preliminary results corresponding to depth-dose responses are obtained as the transverse relaxation rate (R2=1/T2) from magnetic resonance imaging data. As the results MAGAT gel dosimeter has the higher sensitivity on thermal neutron than on epi-thermal and fast neutron, and the gel with boron showed an enhancement and a change in the depth-R2 response explicitly. From these results, it is suggested that MAGAT gel dosimeter can be an effective tool in BNCT dosimetry.

  18. The early development of neutron diffraction: science in the wings of the Manhattan Project.

    PubMed

    Mason, T E; Gawne, T J; Nagler, S E; Nestor, M B; Carpenter, J M

    2013-01-01

    Although neutron diffraction was first observed using radioactive decay sources shortly after the discovery of the neutron, it was only with the availability of higher intensity neutron beams from the first nuclear reactors, constructed as part of the Manhattan Project, that systematic investigation of Bragg scattering became possible. Remarkably, at a time when the war effort was singularly focused on the development of the atomic bomb, groups working at Oak Ridge and Chicago carried out key measurements and recognized the future utility of neutron diffraction quite independent of its contributions to the measurement of nuclear cross sections. Ernest O. Wollan, Lyle B. Borst and Walter H. Zinn were all able to observe neutron diffraction in 1944 using the X-10 graphite reactor and the CP-3 heavy water reactor. Subsequent work by Wollan and Clifford G. Shull, who joined Wollan's group at Oak Ridge in 1946, laid the foundations for widespread application of neutron diffraction as an important research tool.

  19. DEVELOPMENT OF SIMULATED WORKPLACE FIELDS AT KRISS FOR PERFORMANCE TEST OF NEUTRON PERSONAL DOSEMETERS.

    PubMed

    Kim, Jungho; Park, Hyeonseo; Kim, Yunho

    2016-09-01

    Simulated workplace neutron fields have been developed at the Korea Research Institute of Standards and Science (KRISS). An (241)Am-Be neutron source and a cylindrical moderator composed of stainless steel and heavy water were installed in a 10-cm-thick concrete block with dimensions of 150 × 120 × 120 cm(3) The neutron energy spectrum at a distance of 66.5 cm was measured using a Bonner sphere spectrometer and was found to agree with the spectrum obtained from the Monte Carlo N-Particle Extended simulation to within 5 %. The neutron fluence-to-personal dose equivalent conversion coefficients were (20.8-43.6) pSv·cm(2) and were thus in good agreement with those of reactor fields. The results showed that the KRISS-simulated workplace neutron fields can be used for performance tests and the calibration service of neutron personal dosemeters. PMID:26541186

  20. 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.

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

    SciTech Connect

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

    2004-10-07

    We are developing a new active interrogation system based on a kinematically focused low energy neutron beam. The key idea is that one of the defining characteristics of SNM (Special Nuclear Materials) is the ability for low energy or thermal neutrons to induce fission. Thus by using low energy neutrons for the interrogation source we can accomplish three goals, (1) Energy discrimination allows us to measure the prompt fast fission neutrons produced while the interrogation beam is on; (2) Neutrons with an energy of approximately 60 to 100 keV do not fission 238U and Thorium, but penetrate bulk material nearly as far as high energy neutrons do and (3) below about 100keV neutrons lose their energy by kinematical collisions rather than via the nuclear (n,2n) or (n,n') processes thus further simplifying the prompt neutron induced background. 60 keV neutrons create a low radiation dose and readily thermal capture in normal materials, thus providing a clean spectroscopic signature of the intervening materials. The kinematically beamed source also eliminates the need for heavy backward and sideway neutron shielding. We have designed and built a very compact pulsed neutron source, based on an RFQ proton accelerator and a lithium target. We are developing fast neutron detectors that are nearly insensitive to the ever-present thermal neutron and neutron capture induced gamma ray background. The detection of only a few high energy fission neutrons in time correlation with the linac pulse will be a clear indication of the presence of SNM.

  2. Two-neutron transfer reactions with heavy-deformed nuclei

    SciTech Connect

    Price, C.; Landowne, S.; Esbensen, H.

    1988-01-01

    In a recent communication we pointed out that one can combine the macroscopic model for two-particle transfer reactions on deformed nuclei with the sudden limit approximation for rotational excitation, and thereby obtain a practical method for calculating transfer reactions leading to high-spin states. As an example, we presented results for the reaction WSDy(VYNi,WNi) WDy populating the ground-state rotational band up to the spin I = 14 state. We have also tested the validity of the sudden limit for the inelastic excitation of high spin states and we have noted how the macroscopic model may be modified to allow for more microscopic nuclear structure effects in an application to diabolic pair-transfer processes. This paper describes our subsequent work in which we investigated the systematic features of pair-transfer reactions within the macroscopic model by using heavier projectiles to generate higher spins and by decomposing the cross sections according to the multipolarity of the transfer interaction. Particular attention is paid to characteristic structures in the angular distributions for the lower spin states and how they depend on the angular momentum carried by the transferred particles. 11 refs., 3 figs.

  3. Cluster physics and the importance of forbiddenness

    NASA Astrophysics Data System (ADS)

    Hess, P. O.; Yépez-Martínez, H.

    2016-07-01

    We review the concept of forbiddenness as introduced by Smirnov and Yu M. Tchuvil'sky [1], which states that most of the properties of nuclear reactions and cluster structure is based on structural effects (Pauli exclusion principle). This becomes also clear when one tries to obtain the ground state of the united nucleus by two heavy clusters, which is not possible when all excitations are put into the relative motion. Smirnov et al. introduced the concept of forbiddenness, which is defined as the minimal number of relative oscillation quanta which have to be shifted to internal excitations of the clusters, such that the ground state can be reached. We show that Smirnov et al. committed and error in the derivation, leading us to reevaluate the derivation of the forbiddenness. We deduce the correct expression for the forbiddenness, leading to a simple interpretation and implementation in a cluster model and some applications are presented.

  4. Spectrum evaluation at the filter-modified neutron irradiation field for neutron capture therapy in Kyoto University Research Reactor

    NASA Astrophysics Data System (ADS)

    Sakurai, Yoshinori; Kobayashi, Tooru

    2004-10-01

    The Heavy Water Neutron Irradiation Facility of the Kyoto University Research Reactor (KUR-HWNIF) was updated in March 1996, mainly to improve the facility for neutron capture therapy (NCT). In this facility, neutron beams with various energy spectra, from almost pure thermal to epithermal, are available. The evaluation of the neutron energy spectra by multi-activation-foil method was performed as a series of the facility characterization. The spectra at the normal irradiation position were evaluated for the combinations of heavy-water thickness of the spectrum shifter and the open-close condition of the cadmium and boral filters. The initial spectra were made mainly using a two-dimensional transport code, and the final spectra were obtained using an adjusting code. For the verification of the evaluated spectra, simulation calculations using a phantom were performed on the assumption of NCT-clinical-irradiation conditions. It resulted that the calculated data for the depth neutron-flux distributions were in good agreement with the experimental ones.

  5. Neutron Capture Cross Sections of 236U and 234U

    NASA Astrophysics Data System (ADS)

    Rundberg, R. S.; Bredeweg, T. A.; Bond, E. M.; Haight, R. C.; Hunt, L. F.; Kronenberg, A.; O'Donnell, J. M.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2006-03-01

    Accurate neutron capture cross sections of the actinide elements at neutron energies up to 1 MeV are needed to better interpret archived nuclear test data, for post-detonation nuclear attribution, and the Advanced Fuel Cycle Initiative. The Detector for Advance Neutron Capture Experiments, DANCE, has unique capabilities that allow the differentiation of capture gamma rays from fission gamma rays and background gamma rays from scattered neutrons captured by barium isotopes in the barium fluoride scintillators. The DANCE array has a high granularity, 160 scintillators, high efficiency, and nearly 4-π solid angle. Through the use of cuts in cluster multiplicity and calorimetric energy the capture gamma-rays are differentiated from other sources of gamma rays. The preliminary results for the capture cross sections of 236U are in agreement with the ENDF/B-VI evaluation. The preliminary results for 234U lower are than ENDF/B-VI evaluation and are closer to older evaluations.

  6. Neutron Capture Cross Sections of 236U and 234U

    SciTech Connect

    Rundberg, R. S.; Bredeweg, T. A.; Bond, E. M.; Haight, R. C.; Hunt, L. F.; O'Donnell, J. M.; Schwantes, J. M.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.; Kronenberg, A.

    2006-03-13

    Accurate neutron capture cross sections of the actinide elements at neutron energies up to 1 MeV are needed to better interpret archived nuclear test data, for post-detonation nuclear attribution, and the Advanced Fuel Cycle Initiative. The Detector for Advance Neutron Capture Experiments, DANCE, has unique capabilities that allow the differentiation of capture gamma rays from fission gamma rays and background gamma rays from scattered neutrons captured by barium isotopes in the barium fluoride scintillators. The DANCE array has a high granularity, 160 scintillators, high efficiency, and nearly 4-{pi} solid angle. Through the use of cuts in cluster multiplicity and calorimetric energy the capture gamma-rays are differentiated from other sources of gamma rays. The preliminary results for the capture cross sections of 236U are in agreement with the ENDF/B-VI evaluation. The preliminary results for 234U lower are than ENDF/B-VI evaluation and are closer to older evaluations.

  7. The Many Faces - and Phases - of Neutron Stars

    SciTech Connect

    Piekarewicz, J.

    2007-10-26

    Understanding the equation of state (EOS) of nuclear matter is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the EOS of cold baryonic matter with special emphasis on its impact on the structure and dynamics of neutron stars. In particular, I will discuss the many fascinating phases that one encounters as one travels from the low-density crust to the high-density core.

  8. Neutron capture therapies

    SciTech Connect

    Yanch, J.C.; Shefer, R.E.; Klinkowstein, R.E.

    1999-11-02

    In one embodiment there is provided an application of the {sup 10}B(n,{alpha}){sup 7}Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  9. Fundamental Neutron Physics

    NASA Astrophysics Data System (ADS)

    Marciano, William J.

    A precise connection between Vud, gA ≡ GA/GV and rn is reviewed. Implications for CKM unitarity and muon capture are discussed. The neutron electric dipole moment and CP violation in H → yy are related. ΔB = 2 n oscillations are shown to probe the neutron's Majorana nature and provide a possible paradigm for dark matter behavior.

  10. NEUTRONIC REACTOR CONTROL

    DOEpatents

    Untermyer, S.; Hutter, E.

    1959-08-01

    This patent relates to "shadow" control of a nuclear reactor. The control means comprises a plurality ot elongated rods disposed adjacent and parallel to each other, The morphology and effects of gases generated within sections of neutron absorbing materials and equal length sections of neutron permeable materials together with means for longitudinally pcsitioning the rcds relative to each other.

  11. Neutron capture therapies

    DOEpatents

    Yanch, Jacquelyn C.; Shefer, Ruth E.; Klinkowstein, Robert E.

    1999-01-01

    In one embodiment there is provided an application of the .sup.10 B(n,.alpha.).sup.7 Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  12. Compact neutron generator

    DOEpatents

    Leung, Ka-Ngo; Lou, Tak Pui

    2005-03-22

    A compact neutron generator has at its outer circumference a toroidal shaped plasma chamber in which a tritium (or other) plasma is generated. A RF antenna is wrapped around the plasma chamber. A plurality of tritium ion beamlets are extracted through spaced extraction apertures of a plasma electrode on the inner surface of the toroidal plasma chamber and directed inwardly toward the center of neutron generator. The beamlets pass through spaced acceleration and focusing electrodes to a neutron generating target at the center of neutron generator. The target is typically made of titanium tubing. Water is flowed through the tubing for cooling. The beam can be pulsed rapidly to achieve ultrashort neutron bursts. The target may be moved rapidly up and down so that the average power deposited on the surface of the target may be kept at a reasonable level. The neutron generator can produce fast neutrons from a T-T reaction which can be used for luggage and cargo interrogation applications. A luggage or cargo inspection system has a pulsed T-T neutron generator or source at the center, surrounded by associated gamma detectors and other components for identifying explosives or other contraband.

  13. Measurement of the Radius of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Guillot, Sebastien

    2012-07-01

    A physical understanding of the behavior of cold ultra-dense matter -- at and above nuclear density -- can only be achieved by the study of neutron stars. The recent 1.97+/-0.04 Msun measurement for PSR 1614-2230 suggests that strange quark matter and hyperons/kaons condensate equations of state (EoSs) are disfavored, in favor of hadronic EoSs. Over much of the neutron star mass-radius parameter space, the latter EoSs produce lines of nearly constant radii (within about 10%). We present a simultaneous spectral analysis of several globular cluster quiescent low-mass x-ray binaries where we require the radius to be the same among all neutron stars analyzed. Our (preliminary) results suggest a neutron star radius much smaller than previously reported, in the range 7.5-10 km (90% confidence). The Markov-Chain Monte-Carlo method and the Bayesian approach developed in this analysis permits including uncertainties in the distance, in the hydrogen column density, and possible contributions to the spectra due to unmodelled spectrally hard components.

  14. Measurement of the Radius of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Guillot, Sebastien; Rutledge, R. E.; Servillat, M.; Webb, N.

    2013-01-01

    A physical understanding of the behavior of cold ultra dense matter - at and above nuclear density - can only be achieved by the study of neutron stars. The recent 1.97 ± 0.04 M⊙ measurement for PSR 1614-2230 suggests that strange quark matter and hyperons/kaons condensate equations of state (EoSs) are disfavored, in favor of hadronic EoSs. Over much of the neutron star mass-radius parameter space, the latter EoSs produce lines of nearly constant radii (within about 10%). We present a simultaneous spectral analysis of several globular cluster quiescent low-mass X-ray binaries where we require the radius to be the same among all neutron stars analyzed. Our (preliminary) results suggest a neutron star radius much smaller than previously reported, in the range 7.5-10 km (90% confidence). The Markov-Chain Monte-Carlo method and the Bayesian approach developed in this analysis permits including uncertainties in the distance, in the hydrogen column density, and possible contributions to the spectra due to unmodeled spectrally hard components.

  15. Probing neutron-proton dynamics by pions

    NASA Astrophysics Data System (ADS)

    Ikeno, Natsumi; Ono, Akira; Nara, Yasushi; Ohnishi, Akira

    2016-04-01

    In order to investigate the nuclear symmetry energy at high density, we study the pion production in central collisions of neutron-rich nuclei 132Sn+124Sn at 300 MeV/nucleon using a new approach that combines antisymmetrized molecular dynamics (AMD) and a hadronic cascade model (JAM). The dynamics of neutrons and protons is solved by AMD, and then pions and Δ resonances in the reaction process are handled by JAM. We see the mechanism by which the Δ resonance and pions are produced, reflecting the dynamics of neutrons and protons. We also investigate the impacts of cluster correlations as well as of the high-density symmetry energy on the nucleon dynamics and consequently on the pion ratio. We find that the Δ-/Δ++ production ratio agrees very well with the neutron-proton squared ratio (N/Z ) 2 in the high-density and high-momentum region. We show quantitatively that the Δ production ratio, and therefore (N/Z ) 2, are directly reflected in the π-/π+ ratio, with modification in the final stage of the reaction.

  16. Simulated asymptotic giant branch populations for Magellanic Cloud clusters

    SciTech Connect

    Frantsman, IU.L.

    1986-04-01

    An approximate numerical calculation for an evolving 100,000-star cluster simulates the asymptotic giant branch (AGB) populations of two Magellanic Cloud globular clusters. Several laws of mass loss by AGB stars and various initial heavy-element abundances and cluster ages are considered. In the H-R diagram the early-AGB stars differ in both luminosity and Teff from AGB stars passing through the helium shell thermal-flash stage. The numbers of M- and C-type stars in this second phase are predicted for model clusters with different parameters. 18 references.

  17. Pocked surface neutron detector

    DOEpatents

    McGregor, Douglas; Klann, Raymond

    2003-04-08

    The detection efficiency, or sensitivity, of a neutron detector material such as of Si, SiC, amorphous Si, GaAs, or diamond is substantially increased by forming one or more cavities, or holes, in its surface. A neutron reactive material such as of elemental, or any compound of, .sup.10 B, .sup.6 Li, .sup.6 LiF, U, or Gd is deposited on the surface of the detector material so as to be disposed within the cavities therein. The portions of the neutron reactive material extending into the detector material substantially increase the probability of an energetic neutron reaction product in the form of a charged particle being directed into and detected by the neutron detector material.

  18. Neutrons against cancer

    NASA Astrophysics Data System (ADS)

    Dovbnya, A. N.; Kuplennikov, E. L.; Kandybey, S. S.; Krasiljnikov, V. V.

    2014-09-01

    The review is devoted to the analysis and generalization of the research carried out during recent years in industrially advanced countries on the use of fast, epithermal, and thermal neutrons for therapy of malignant tumors. Basic facilities for neutron production used for cancer treatment are presented. Optimal parameters of therapeutic beams are described. Techniques using neutrons of different energy regions are discussed. Results and medical treatment efficiency are given. Comparison of the current state of neutron therapy of tumors and alternative treatments with beams of protons and carbon ions has been conducted. Main attention is given to the possibility of the practical use of accumulated experience of application of neutron beams for cancer therapy.

  19. THERMAL NEUTRON BACKSCATTER IMAGING.

    SciTech Connect

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  20. Pulsed neutron detector

    DOEpatents

    Robertson, deceased, J. Craig; Rowland, Mark S.

    1989-03-21

    A pulsed neutron detector and system for detecting low intensity fast neutron pulses has a body of beryllium adjacent a body of hydrogenous material the latter of which acts as a beta particle detector, scintillator, and moderator. The fast neutrons (defined as having En>1.5 MeV) react in the beryllium and the hydrogenous material to produce larger numbers of slow neutrons than would be generated in the beryllium itself and which in the beryllium generate hellium-6 which decays and yields beta particles. The beta particles reach the hydrogenous material which scintillates to yield light of intensity related to the number of fast neutrons. A photomultiplier adjacent the hydrogenous material (scintillator) senses the light emission from the scintillator. Utilization means, such as a summing device, sums the pulses from the photo-multiplier for monitoring or other purposes.

  1. NEUTRON SHIELDING STRUCTURE

    DOEpatents

    Mattingly, J.T.

    1962-09-25

    A lightweight neutron shielding structure comprises a honeycomb core which is filled with a neutron absorbing powder. The honeycomb core is faced with parallel planar facing sheets to form a lightweight rigid unit. Suitable absorber powders are selected from among the following: B, B/sub 4/C, B/sub 2/O/ sub 3/, CaB/sub 6/, Li/sub 2/CO3, LiOH, LiBO/sub 2/, Li/s ub 2/O. The facing sheets are constructed of a neutron moderating material, so that fast neutrons will be moderated while traversing the facing sheets, and ultimately be absorbed by the absorber powder in the honeycomb. Beryllium is a preferred moderator material for use in the facing sheets. The advantage of the structure is that it combines the rigidity and light weight of a honeycomb construction with the neutron absorption properties of boron and lithium. (AEC)

  2. Simulated workplace neutron fields

    NASA Astrophysics Data System (ADS)

    Lacoste, V.; Taylor, G.; Röttger, S.

    2011-12-01

    The use of simulated workplace neutron fields, which aim at replicating radiation fields at practical workplaces, is an alternative solution for the calibration of neutron dosemeters. They offer more appropriate calibration coefficients when the mean fluence-to-dose equivalent conversion coefficients of the simulated and practical fields are comparable. Intensive Monte Carlo modelling work has become quite indispensable for the design and/or the characterization of the produced mixed neutron/photon fields, and the use of Bonner sphere systems and proton recoil spectrometers is also mandatory for a reliable experimental determination of the neutron fluence energy distribution over the whole energy range. The establishment of a calibration capability with a simulated workplace neutron field is not an easy task; to date only few facilities are available as standard calibration fields.

  3. Early and late mammalian responses to heavy charged particles

    NASA Technical Reports Server (NTRS)

    Ainsworth, E. J.

    1986-01-01

    This overview summarizes murine results on acute lethality responses, inactivation of marrow CFU-S and intestinal microcolonies, testes weight loss, life span shortening, and posterior lens opacification in mice irradiated with heavy charged particles. RBE-LET relationships for these mammalian responses are compared with results from in vitro studies. The trend is that the maximum RBE for in vivo responses tends to be lower and occurs at a lower LET than for inactivation of V79 and T-1 cells in culture. Based on inactivation cross sections, the response of CFU-S in vivo conforms to expectations from earlier studies with prokaryotic systems and mammalian cells in culture. Effects of heavy ions are compared with fission spectrum neutrons, and the results are consistent with the interpretation that RBEs are lower than for fission neutrons at about the same LET, probably due to differences in track structure.

  4. SINGLE CRYSTAL NEUTRON DIFFRACTION.

    SciTech Connect

    KOETZLE,T.F.

    2001-03-13

    Single-crystal neutron diffraction measures the elastic Bragg reflection intensities from crystals of a material, the structure of which is the subject of investigation. A single crystal is placed in a beam of neutrons produced at a nuclear reactor or at a proton accelerator-based spallation source. Single-crystal diffraction measurements are commonly made at thermal neutron beam energies, which correspond to neutron wavelengths in the neighborhood of 1 Angstrom. For high-resolution studies requiring shorter wavelengths (ca. 0.3-0.8 Angstroms), a pulsed spallation source or a high-temperature moderator (a ''hot source'') at a reactor may be used. When complex structures with large unit-cell repeats are under investigation, as is the case in structural biology, a cryogenic-temperature moderator (a ''cold source'') may be employed to obtain longer neutron wavelengths (ca. 4-10 Angstroms). A single-crystal neutron diffraction analysis will determine the crystal structure of the material, typically including its unit cell and space group, the positions of the atomic nuclei and their mean-square displacements, and relevant site occupancies. Because the neutron possesses a magnetic moment, the magnetic structure of the material can be determined as well, from the magnetic contribution to the Bragg intensities. This latter aspect falls beyond the scope of the present unit; for information on magnetic scattering of neutrons see Unit 14.3. Instruments for single-crystal diffraction (single-crystal diffractometers or SCDs) are generally available at the major neutron scattering center facilities. Beam time on many of these instruments is available through a proposal mechanism. A listing of neutron SCD instruments and their corresponding facility contacts is included in an appendix accompanying this unit.

  5. Mutagenicity of heavy metals

    SciTech Connect

    Wong, P.K. )

    1988-05-01

    Certain heavy metals are required, as trace elements for normal cellular functions. However, heavy metals are toxic to cells once their levels exceed their low physiological values. The toxicity of heavy metals on microorganisms, on plants and on animals has been well-documented. These interactions may induce the alteration of the primary as well as secondary structures of the DNA and result in mutation(s). Though the rec assay with Bacillus subtilis and the reversion assay with Escherichia coli were used to assess the mutagenicity of some heavy metals, the present communication reports the results in determining the mutagenicity and carcinogenicity of ten heavy metals commonly found in polluted areas by using the Salmonella/mammalian-microsome mutagenicity test.

  6. Optical polarizing neutron devices designed for pulsed neutron sources

    SciTech Connect

    Takeda, M.; Kurahashi, K.; Endoh, Y.; Itoh, S.

    1997-09-01

    We have designed two polarizing neutron devices for pulsed cold neutrons. The devices have been tested at the pulsed neutron source at the Booster Synchrotron Utilization Facility of the National Laboratory for High Energy Physics. These two devices proved to have a practical use for experiments to investigate condensed matter physics using pulsed cold polarized neutrons.

  7. Neutron Capture Gamma-Ray Libraries for Nuclear Applications

    NASA Astrophysics Data System (ADS)

    Sleaford, B. W.; Firestone, R. B.; Summers, N.; Escher, J.; Hurst, A.; Krticka, M.; Basunia, S.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H. D.

    2011-06-01

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

  8. Neutron Capture Gamma-Ray Libraries for Nuclear Applications

    SciTech Connect

    Sleaford, B W; Firestone, R B; Summers, N; Escher, J; Hurst, A; Krticka, M; Basunia, S; Molnar, G; Belgya, T; Revay, Z; Choi, H D

    2010-11-04

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. this can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. They are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

  9. Neutron Capture Gamma-Ray Libraries for Nuclear Applications

    SciTech Connect

    Sleaford, B. W.; Summers, N.; Escher, J.; Firestone, R. B.; Basunia, S.; Hurst, A.; Krticka, M.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H. D.

    2011-06-28

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

  10. A neutron tomography facility at a low power research reactor

    NASA Astrophysics Data System (ADS)

    Koerner, S.; Schillinger, B.; Vontobel, P.; Rauch, H.

    2001-09-01

    Neutron radiography (NR) provides a very efficient tool in the field of non-destructive testing as well as for many applications in fundamental research. A neutron beam penetrating a specimen is attenuated by the sample material and detected by a two-dimensional (2D) imaging device. The image contains information about materials and structure inside the sample because neutrons are attenuated according to the basic law of radiation attenuation. Contrary to X-rays, neutrons can be attenuated by some light materials, as for example, hydrogen and boron, but penetrate many heavy materials. Therefore, NR can yield important information not obtainable by more traditional methods. Nevertheless, there are many aspects of structure, both quantitative and qualitative, that are not accessible from 2D transmission images. Hence, there is an interest in three-dimensional neutron imaging. At the 250 kW TRIGA Mark II reactor of the Atominstitut in Austria a neutron tomography facility has been installed. The neutron flux at this beam position is 1.3×10 5 neutrons/cm 2 s and the beam diameter is 8 cm. For a 3D tomographic reconstruction of the sample interior, transmission images of the object taken from different view angles are required. Therefore, a rotary table driven by a step motor connected to a computerized motion control system has been installed at the sample position. In parallel a suitable electronic imaging device based on a neutron sensitive scintillator screen and a CCD-camera has been designed. It can be controlled by a computer in order to synchronize the software of the detector and of the rotary table with the aim of an automation of measurements. Reasonable exposure times can get as low as 20 s per image. This means that a complete tomography of a sample can be performed within one working day. Calculation of the 3D voxel array is made by using the filtered backprojection algorithm.

  11. Precision neutron flux measurement with a neutron beam monitor

    NASA Astrophysics Data System (ADS)

    Ino, T.; Otono, H.; Mishima, K.; Yamada, T.

    2014-07-01

    Neutron beam monitors are regularly used in various neutron beam experiments to compare two or more sets of data taken in different experimental conditions. A neutron lifetime experiment at BL05, the NOP beamline, in J-PARC requires to monitor the initial neutron intensity with an precision of 0.1% to measure the neutron lifetime with the same accuracy. The performance of a thin 3He gas neutron beam monitor used for the experiment was studied to estimate the systematic uncertainties in the neutron lifetime measurement.

  12. Heavy ion collisions and the pre-equilibrium exciton model

    SciTech Connect

    Betak, E.

    2012-10-20

    We present a feasible way to apply the pre-equilibrium exciton model in its masterequation formulation to heavy-ion induced reactions including spin variables. Emission of nucleons, {gamma}'s and also light clusters is included in our model.

  13. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.

    1979-01-01

    The heavy isotopic anomalies observed recently in the fractionation and unknown nuclear inclusions from the Allende meteorite are explained by neutron reactions during the explosive carbon burning (ECB). This model produces heavy anomalies in the same zone where Al-26 and O-16 are produced, thus reducing the number of source zones required for the isotopic anomalies. Unlike the classical r-process, the ECB n-process avoids the problem with the Sr anomaly and may resolve the problem of conflicting time scales between Al-26 and the r-process isotopes I-129 and Pu-244. Experimental studies of Zr and Ce isotopic composition are proposed to test this model.

  14. Changes of Heavy Metals in Pollutant Release and Transfer Registers (PRTRs) in Korea

    PubMed Central

    Kwon, Yong-Su; Bae, Mi-Jung; Park, Young-Seuk

    2014-01-01

    Industrial effluent containing heavy metals discharged into streams may pose high toxicity risks to aquatic organisms and to human health. Therefore, it is important to understand how to change the amount of effluent with heavy metals discharged from industries into open aquatic ecosystems both for effective management of heavy metals and to foster sustainable ecosystems. This study was conducted to characterize the release of heavy metals from industries based on the Pollutant Release and Transfer Registers database in Korea from 1999 to 2010. From the database, we selected nine heavy metals (Pb, Cd, Mn, Sb, Cu, Zn, Cr, Sn, and Ni) and compared the differences in their effluent for different types of industries. The heavy metal effluents released into freshwater ecosystems were classified into four clusters through the learning process of the self-organizing map. Cluster 1 was characterized by the relatively higher effluent volumes of heavy metals, whereas cluster 4 had lower effluent volumes. The different patterns of the effluent volumes in heavy metals were closely associated with the differences of industrial types, and the changes of effluents of heavy metals reflected the changes in regulations and laws for aquatic ecosystem management. PMID:24577281

  15. ZIRCONIUM, BARIUM, LANTHANUM, AND EUROPIUM ABUNDANCES IN OPEN CLUSTERS

    SciTech Connect

    Jacobson, Heather R.; Friel, Eileen D. E-mail: efriel@indiana.edu

    2013-04-15

    We present an analysis of the s-process elements Zr, Ba, and La and the r-process element Eu in a sample of 50 stars in 19 open clusters. Stellar abundances of each element are based on measures of a minimum of two lines per species via both equivalent width and spectrum synthesis techniques. We investigate cluster mean neutron-capture abundance trends as a function of cluster age and location in the Milky Way disk and compare them to results found in other studies in the literature. We find a statistically significant trend of increasing cluster [Ba/Fe] as a function of decreasing cluster age, in agreement with recent findings for other open cluster samples, supporting the increased importance of low-mass asymptotic giant branch stars to the generation of s-process elements. However, the other s-process elements, [La/Fe] and [Zr/Fe], do not show similar dependences, in contrast to theoretical expectations and the limited observational data from other studies. Conversely, cluster [Eu/Fe] ratios show a slight increase with increasing cluster age, although with marginal statistical significance. Ratios of [s/r]-process abundances, [Ba/Eu] and [La/Eu], however, show more clearly the increasing efficiency of s-process relative to r-process enrichment in open cluster chemical evolution, with significant increases among younger clusters. Last, cluster neutron-capture element abundances appear to be independent of Galactocentric distance. We conclude that a homogeneous analysis of a larger sample of open clusters is needed to resolve the apparent discrepant conclusions between different studies regarding s-process element abundance trends with age to better inform models of galactic chemical evolution.

  16. Advanced Monte Carlo modeling of prompt fission neutrons for thermal and fast neutron-induced fission reactions on Pu239

    NASA Astrophysics Data System (ADS)

    Talou, P.; Becker, B.; Kawano, T.; Chadwick, M. B.; Danon, Y.

    2011-06-01

    Prompt fission neutrons following the thermal and 0.5 MeV neutron-induced fission reaction of Pu239 are calculated using a Monte Carlo approach to the evaporation of the excited fission fragments. Exclusive data such as the multiplicity distribution P(ν), the average multiplicity as a function of fragment mass ν¯(A), and many others are inferred in addition to the most used average prompt fission neutron spectrum χ(Ein,Eout), as well as average neutron multiplicity ν¯. Experimental information on these more exclusive data help constrain the Monte Carlo model parameters. The calculated average total neutron multiplicity is ν¯c=2.871 in very close agreement with the evaluated value ν¯e=2.8725 present in the ENDF/B-VII.0 library. The neutron multiplicity distribution P(ν) is in very good agreement with the evaluation by Holden and Zucker. The calculated average spectrum differs in shape from the ENDF/B-VII.0 spectrum, evaluated with the Madland-Nix model. In particular, we predict more neutrons in the low-energy tail of the spectrum (below about 300 keV) than the Madland-Nix calculations, casting some doubts on how much scission neutrons contribute to the shape of the low-energy tail of the spectrum. The spectrum high-energy tail is very sensitive to the total kinetic energy distribution of the fragments as well as to the total excitation energy sharing at scission. Present experimental uncertainties on measured spectra above 6 MeV are too large to distinguish between various theoretical hypotheses. Finally, comparisons of the Monte Carlo results with experimental data on ν¯(A) indicate that more neutrons are emitted from the light fragments than the heavy ones, in agreement with previous works.

  17. Neutron Capture Reactions for Stockpile Stewardship and Basic Science

    SciTech Connect

    Parker, W; Agvaanluvsan, U; Becker, J; Wilk, P; Wu, C; Bredeweg, T; Couture, A; Haight, R; Jandel, M; O'Donnell, J; Reifarth, R; Rundberg, R; Ullmann, J; Vieira, D; Wouters, J; Sheets, S; Mitchell, G; Becvar, F; Krticka, M

    2007-08-04

    The capture process is a nuclear reaction in which a target atom captures an incident projectile, e.g. a neutron. The excited-state compound nucleus de-excites by emitting photons. This process creates an atom that has one more neutron than the target atom, so it is a different isotope of the same element. With low energy (slow) neutron projectiles, capture is the dominant reaction, other than elastic scattering. However, with very heavy nuclei, fission competes with capture as a method of de-excitation of the compound nucleus. With higher energy (faster) incident neutrons, additional reactions are also possible, such as emission of protons or emission of multiple neutrons. The probability of a particular reaction occurring (such as capture) is referred to as the cross section for that reaction. Cross sections are very dependent on the incoming neutron's energy. Capture reactions can be studied either using monoenergetic neutron sources or 'white' neutron sources. A 'white' neutron source has a wide range of neutron energies in one neutron beam. The advantage to the white neutron source is that it allows the study of cross sections as they depend on neutron energies. The Los Alamos Neutron Science Center, located at Los Alamos National Laboratory, provides an intense white neutron source. Neutrons there are created by a high-energy proton beam from a linear accelerator striking a heavy metal (tungsten) target. The neutrons range in energy from subthermal up to very fast - over 100 MeV in energy. Low-energy neutron reaction cross sections fluctuate dramatically from one target to another, and they are very difficult to predict by theoretical modeling. The cross sections for particular capture reactions are important for defense sciences, advanced reactor concepts, transmutation of radioactive wastes and nuclear astrophysics. We now have a strong collaboration between Lawrence Livermore National Laboratory, Los Alamos National Laboratory, North Carolina State

  18. Genetic effects on heavy ions in drosophila

    NASA Technical Reports Server (NTRS)

    Kale, P. G.

    1986-01-01

    Drosophila sex-linked recessive lethal mutation test was used to study the dose response relation and relative biological effectiveness of heavy ions. The experiments were performed using the heavy ion beams at BEVALAC of Lawrence Berkeley Laboratory. These experiments were undertaken according to the proposed milestones and included Ne-20, A-40 and Fe-65 ions with respective energies of 600 MeV, 840 MeV and 850 MeV. At these energies several doses of these radiations ranging from 20 to 1280 R were used. Space radiation exposure to astronauts is supposed to be quite low and therefore very low dose experiments i.e., 20 R, were also performed for the three ions. The mutation response was measured in all germ cell types i.e., spermatozoa, spermatids, spermatocytes and spermatogonia of treated Drosophila males. A linear dose frequency relation was observed for most of the range except at high doses where the saturation effect was observed. Also, a very significant difference was observed among the sensitivity of the four germ cell stages where spermatozoa and spermatids were more sensitive. At the higher doses of this range, most of the spermatogonia and spermatocytes were killed. Although comparative and identical experiments with X-rays or neutrons have not been performed, the compassion of our data with the ones available in literature suggest that the heavy ions have a high rbe and that they are several times more effective than low LET X-rays. The rbe compared to neutrons however appears to be only slightly higher.

  19. Heavy metals detection in sediments using PGNAA method.

    PubMed

    Da-Qian, Hei; Wen-Bao, Jia; Zhou, Jiang; Can, Cheng; Jia-Tong, Li; Hong-Tao, Wang

    2016-06-01

    A prompt gamma ray neutron activation analysis detection system was developed to detect the heavy metals in sediments by using an (241)Am-Be neutron source and BGO detector. The samples containing cadmium and mercury were used to test the performance of setup. The linear relationship between prompt gamma ray counts and the concentrations was studied. The results showed the counts of the prompt gamma rays from cadmium do not increase linearly with its concentrations, while the prompt gamma ray counts from Hg vary nearly linearly with the concentrations, due to the neutron self-shielding. Then a method was used to correct the effect and the non-linearly response was restored after the correction. And the minimum detectable concentration of Cd and Hg were 52.8 (at 8.484MeV) and 81.6 (at 5.967MeV) ppm, respectively. PMID:27015649

  20. Isotopic anomalies from neutron reactions during explosive carbon burning

    NASA Technical Reports Server (NTRS)

    Lee, T.; Schramm, D. N.; Wefel, J. P.; Blake, J. B.

    1978-01-01

    The possibility that the newly discovered correlated isotopic anomalies for heavy elements in the Allende meteorite were synthesized in the secondary neutron capture episode during the explosive carbon burning, the possible source of the O-16 and Al-26 anomalies, is examined. Explosive carbon burning calculations under typical conditions were first performed to generate time profiles of temperature, density, and free particle concentrations. These quantities were inputted into a general neutron capture code which calculates the resulting isotopic pattern from exposing the preexisting heavy seed nuclei to these free particles during the explosive carbon burning conditions. The interpretation avoids the problem of the Sr isotopic data and may resolve the conflict between the time scales inferred from 1-129, Pu-244, and Al-26.

  1. Isospin effects on neutrons as a probe of nuclear dissipation

    SciTech Connect

    Ye, W.

    2009-03-15

    Based on a dynamical Langevin equation coupled with a statistical decay model, we calculate the excess of the precision neutron multiplicity of the heavy nuclei {sup 240}Cf, {sup 246}Cf, {sup 252}Cf, and {sup 240}U over that predicted by the standard statistical model as a function of the postsaddle dissipation strength. We find that with increasing isospin of the system, the sensitivity of the excess to the dissipation strength decreases substantially. Moreover, for {sup 240}U, this excess is no longer sensitive to the nuclear dissipation. These results suggest that, on the experimental side, to accurately obtain information of the postsaddle dissipation strength by measuring the neutron multiplicity evaporated during the fission process of heavy nuclei, it is best to populate those compound systems with low isospin.

  2. FABRICATION OF NEUTRON SOURCES

    DOEpatents

    Birden, J.H.

    1959-04-21

    A method is presented for preparing a neutron source from polonium-210 and substances, such as beryllium and boron, characterized by emission of neutrons upon exposure to alpha particles from the polonium. According to the invention, a source is prepared by placing powdered beryllium and a platinum foil electroplated with polonium-2;.0 in a beryllium container. The container is sealed and then heated by induction to a temperature of 450 to 1100 deg C to volatilize the polonium off the foil into the powder. The heating step is terminated upon detection of a maximum in the neutron flux level.

  3. Coupled moderator neutronics

    SciTech Connect

    Russell, G.J.; Pitcher, E.J.; Ferguson, P.D.

    1995-12-01

    Optimizing the neutronic performance of a coupled-moderator system for a Long-Pulse Spallation Source is a new and challenging area for the spallation target-system designer. For optimal performance of a neutron source, it is essential to have good communication with instrument scientists to obtain proper design criteria and continued interaction with mechanical, thermal-hydraulic, and materials engineers to attain a practical design. A good comprehension of the basics of coupled-moderator neutronics will aid in the proper design of a target system for a Long-Pulse Spallation Source.

  4. Fruits of neutron research

    SciTech Connect

    Krause, C.

    1994-12-31

    Car windshields that don`t break during accidents and jets that fly longer without making a refueling stop. Compact discs, credit cards, and pocket calculators. Refrigerator magnets and automatic car window openers. Beach shoes, food packaging, and bulletproof vests made of tough plastics. The quality and range of consumer products have improved steadily since the 1970s. One of the reasons: neutron research. Industries, employing neutron scattering techniques, to study materials properties, to act as diagnostics in tracing system performance, or as sources for radioactive isotopes used in medical fields for diagnostics or treatment, have all benefited from the fruits of advanced work with neutron sources.

  5. NEUTRONIC REACTOR CONTROL

    DOEpatents

    Metcalf, H.E.

    1958-10-14

    Methods of controlling reactors are presented. Specifically, a plurality of neutron absorber members are adjustably disposed in the reactor core at different distances from the center thereof. The absorber members extend into the core from opposite faces thereof and are operated by motive means coupled in a manner to simultaneously withdraw at least one of the absorber members while inserting one of the other absorber members. This feature effects fine control of the neutron reproduction ratio by varying the total volume of the reactor effective in developing the neutronic reaction.

  6. Heavy-ion dosimetry

    SciTech Connect

    Schimmerling, W.

    1980-03-01

    This lecture deals with some of the more important physical characteristics of relativistic heavy ions and their measurement, with beam delivery and beam monitoring, and with conventional radiation dosimetry as used in the operation of the BEVALAC biomedical facility for high energy heavy ions (Lyman and Howard, 1977; BEVALAC, 1977). Even so, many fundamental aspects of the interaction of relativistic heavy ions with matter, including important atomic physics and radiation chemical considerations, are not discussed beyond the reminder that such additional understanding is required before an adequte perspective of the problem can be attained.

  7. Computer model evaluates heavy oil pumping units

    SciTech Connect

    Brunings, C.; Moya, J.; Morales, J.

    1989-04-10

    The need for Corpoven, S.A., affiliate of Petroleos de Venezuela, S.A., to obtain a model for use in the evaluation of pumping units and downhole equipment in heavy oil wells resulted in the development of an applicable design and optimization technique. All existing models are based on parameters related to wells and equipment for light and medium crudes. Because Venezuela continues to produce large quantities of nonconventional heavy oil, a new computer model was developed. The automation of the artificial lift operations, developed as a pilot project, permitted the monitoring of four wells in a cluster within the Orinoco heavy oil field by a telemetry system and comparison of the new model with existing models. In addition, remote control of sucker rod systems appears to have many advantages such as permanent supervision of a pumping unit, monitoring of preventive maintenance requirements, and close observation of the well behavior. The results of this pilot project are very encouraging, and a study is under way to expand the telemetry system to include more wells from the Orinoco heavy oil field.

  8. Isotope-Identifying neutron reflectometry

    SciTech Connect

    Nikitenko, Yu. V. Petrenko, A. V.; Gundorin, N. A.; Gledenov, Yu. M.; Aksenov, V. L.

    2015-07-15

    The possibilities of an isotope-indentifying study of layered structures in different regimes of a neutron wave field are considered. The detection of specularly reflected neutrons and secondary radiation (caused by neutron capture) in the form of charged particles, γ quanta, and nuclear fission fragments, as well as neutrons spin-flipped in a noncollinear magnetic field and on nuclei of elements with spin, makes it possible to implement isotope-indentifying neutron reflectometry.

  9. Switchable radioactive neutron source device

    DOEpatents

    Boyar, Robert E.; DeVolpi, Alexander; Stanford, George S.; Rhodes, Edgar A.

    1989-01-01

    This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons.

  10. Switchable radioactive neutron source device

    DOEpatents

    Stanford, G.S.; Rhodes, E.A.; Devolpi, A.; Boyar, R.E.

    1987-11-06

    This invention is a switchable neutron generating apparatus comprised of a pair of plates, the first plate having an alpha emitter section on it and the second plate having a target material portion on it which generates neutrons when its nuclei absorb an alpha particle. In operation, the alpha portion of the first plate is aligned with the neutron portion of the second plate to produce neutrons and brought out of alignment to cease production of neutrons. 3 figs.

  11. Hydrogen clusters in clathrate hydrate.

    PubMed

    Mao, Wendy L; Mao, Ho-Kwang; Goncharov, Alexander F; Struzhkin, Viktor V; Guo, Quanzhong; Hu, Jingzhu; Shu, Jinfu; Hemley, Russell J; Somayazulu, Maddury; Zhao, Yusheng

    2002-09-27

    High-pressure Raman, infrared, x-ray, and neutron studies show that H2 and H2O mixtures crystallize into the sII clathrate structure with an approximate H2/H2O molar ratio of 1:2. The clathrate cages are multiply occupied, with a cluster of two H2 molecules in the small cage and four in the large cage. Substantial softening and splitting of hydrogen vibrons indicate increased intermolecular interactions. The quenched clathrate is stable up to 145 kelvin at ambient pressure. Retention of hydrogen at such high temperatures could help its condensation in planetary nebulae and may play a key role in the evolution of icy bodies. PMID:12351785

  12. Strangeness in nuclei and neutron stars: A challenging puzzle

    DOE PAGES

    Lonardoni, Diego; Lovato, Alessandro; Gandolfi, Stefano; Pederiva, Francesco

    2016-03-25

    The prediction of neutron stars properties is strictly connected to the employed nuclear interactions. The appearance of hyperons in the inner core of the star is strongly dependent on the details of the underlying hypernuclear force. Here, we summarize our recent quantum Monte Carlo results on the development of realistic two- and threebody hyperon-nucleon interactions based on the available experimental data for light- and medium-heavy hypernuclei.

  13. New Neutron Rich Nuclei Near {sup 208}Pb

    SciTech Connect

    Aeystoe, J.; Andreyev, A.; Evensen, A.-H.; Hoff, P.; Huhta, M.; Huyse, M.; ISOLDE Collaboration; Jokinen, A.; Karny, M.; Kugler, E.; Kurpeta, J.; Lettry, J.; Nieminen, A.; Plochocki, A.; Ramdhane, M.; Ravn, H.; Rykaczewski, K.; Szerypo, J.; VanDuppen, P.; Walter, G.; Woehr, A.

    1998-11-13

    The level properties near the stable doubly-magic nuclei formed the experimental grounds for the theoretical description of nuclear structure. However with a departure from the beta-stability line, the classical well-established shell structure might be modified. In particular, it may even vanish for extremely exotic neutron-rich nuclei near the neutron-drip line. Presently, it is impossible to verify such predictions by a direct experimental studies of these exotic objects. However, one may try to observe and understand the evolution of the nuclear structure while departing in the experiment as far as possible from the stable nuclei. An extension of experimental nuclear structure studies towards the nuclei characterized by high neutron excess is crucial for such verifications as well as for the {tau}-process nucleosynthesis scenario. Heavy neutron-rich nuclei, south-east of doubly-magic {sup 208}Pb, were always very difficult to produce and investigate. The nuclei like {sup 218}Po and {sup 214}Pb or {sup 210}Tl marked the border line of known nuclei from the beginning of the radioactivity era for over ninety years. To illustrate the difficulties, one can refer to the experiments employing the on-line mass separator technique. A spallation of heavy targets like {sup 232}Th and {sup 238}U by high-energy protons was proven as a source of heavy neutron-rich nuclei. The isotopes near and beyond doubly-magic {sup 208}Pb were produced too. However, such studies often suffered from an isobaric contamination of much more strongly produced and efficiently released elements like francium or radon and their decay products. A new experimental technique, based on the pulsed release element selective method recently developed at the PS Booster-ISOLDE at CERN [7,8,9] greatly reduces the contamination of these very short-lived {alpha}-emitters (Z {ge} 84) for the isobaric mass chains A=215 to A=218.

  14. APPARATUS FOR MEASURING TOTAL NEUTRON CROSS SECTIONS

    DOEpatents

    Cranberg, L.

    1959-10-13

    An apparatus is described for measuring high-resolution total neutron cross sections at high counting rate in the range above 50-kev neutron energy. The pulsed-beam time-of-flight technique is used to identify the neutrons of interest which are produced in the target of an electrostatic accelerator. Energy modulation of the accelerator . makes it possible to make observations at 100 energy points simultaneously. 761O An apparatus is described for monitoring the proton resonance of a liquid which is particulariy useful in the continuous purity analysis of heavy water. A hollow shell with parallel sides defines a meander chamber positioned within a uniform magnetic fieid. The liquid passes through an inlet at the outer edge of the chamber and through a spiral channel to the central region of the chamber where an outlet tube extends into the chamber perpendicular to the magnetic field. The radiofrequency energy for the monitor is coupled to a coil positioned coaxially with the outlet tube at its entrance point within the chamber. The improvement lies in the compact mechanical arrangement of the monitor unit whereby the liquid under analysis is subjected to the same magnetic field in the storage and sensing areas, and the entire unit is shielded from external electrostatic influences.

  15. Neutron personnel dosimetry

    SciTech Connect

    Griffith, R.V.

    1981-06-16

    The current state-of-the-art in neutron personnel dosimetry is reviewed. Topics covered include dosimetry needs and alternatives, current dosimetry approaches, personnel monitoring devices, calibration strategies, and future developments. (ACR)

  16. NEUTRON-COUNTER

    DOEpatents

    Gunst, S.B.; Bayard, R.T.

    1960-12-20

    A heat- aud pressure-resistant radiation counter adaptable to the counting of thermal neutrons comprising a spheroidal chamber electrode having a coating of fissionable material and containing a spherical electrode is described.

  17. Shifting scintillator neutron detector

    SciTech Connect

    Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

    2014-03-04

    Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

  18. Temperature of neutron stars

    NASA Astrophysics Data System (ADS)

    Tsuruta, Sachiko

    2016-07-01

    We start with a brief introduction to the historical background in the early pioneering days when the first neutron star thermal evolution calculations predicted the presence of neutron stars hot enough to be observable. We then report on the first detection of neutron star temperatures by ROSAT X-ray satellite, which vindicated the earlier prediction of hot neutron stars. We proceed to present subsequent developments, both in theory and observation, up to today. We then discuss the current status and the future prospect, which will offer useful insight to the understanding of basic properties of ultra-high density matter beyond the nuclear density, such as the possible presence of such exotic particles as pion condensates.

  19. Cooling of neutron stars

    NASA Technical Reports Server (NTRS)

    Pethick, C. J.

    1992-01-01

    It is at present impossible to predict the interior constitution of neutron stars based on theory and results from laboratory studies. It has been proposed that it is possible to obtain information on neutron star interiors by studying thermal radiation from their surfaces, because neutrino emission rates, and hence the temperature of the central part of a neutron star, depend on the properties of dense matter. The theory predicts that neutron stars cool relatively slowly if their cores are made up of nucleons, and cool faster if the matter is in an exotic state, such as a pion condensate, a kaon condensate, or quark matter. This view has recently been questioned by the discovery of a number of other processes that could lead to copious neutrino emission and rapid cooling.

  20. Neutron resonance averaging

    SciTech Connect

    Chrien, R.E.

    1986-10-01

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs.

  1. NEUTRONIC REACTOR FUEL COMPOSITION

    DOEpatents

    Thurber, W.C.

    1961-01-10

    Uranium-aluminum alloys in which boron is homogeneously dispersed by adding it as a nickel boride are described. These compositions have particular utility as fuels for neutronic reactors, boron being present as a burnable poison.

  2. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2008-04-22

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  3. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2005-06-14

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  4. Cylindrical neutron generator

    DOEpatents

    Leung, Ka-Ngo

    2009-12-29

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  5. Coulomb explosions of deuterium clusters studied by compact design of Nomarski interferometer

    NASA Astrophysics Data System (ADS)

    Martinkova, Michaela; Kalal, Milan; Rhee, Yong Joo

    2010-08-01

    Interactions of high-intensity femtosecond lasers with deuterium clusters leading to Coulombic explosions and subsequent production of fusion neutrons attracted in recent years considerable attention. In order to maximize the neutron yield finding a dependence of clusters size and their spatial distribution on experimental conditions became very important. In this paper a possibility to measure the deuterium clusters spatial distributions experimentally was analyzed. In combination with experiments recently performed in the Laboratory of Quantum Optics at the Korea Atomic Energy Research Institute (KAERI) interferometry was identified as the diagnostics suitable for such measurements.

  6. FABRICATION OF NEUTRON SOURCES

    DOEpatents

    Birden, J.H.

    1959-01-20

    A method is presented for preparing a more efficient neutron source comprising inserting in a container a quantity of Po-210, inserting B powder coated with either Ag, Pt, or Ni. The container is sealed and then slowly heated to about 450 C to volatilize the Po and effect combination of the coated powder with the Po. The neutron flux emitted by the unit is moritored and the heating step is terminated when the flux reaches a maximum or selected level.

  7. NEUTRON FLUX INTENSITY DETECTION

    DOEpatents

    Russell, J.T.

    1964-04-21

    A method of measuring the instantaneous intensity of neutron flux in the core of a nuclear reactor is described. A target gas capable of being transmuted by neutron bombardment to a product having a resonance absorption line nt a particular microwave frequency is passed through the core of the reactor. Frequency-modulated microwave energy is passed through the target gas and the attenuation of the energy due to the formation of the transmuted product is measured. (AEC)

  8. Pulsed spallation neutron sources

    SciTech Connect

    Carpenter, J.M.

    1996-05-01

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology.

  9. Neutron ion temperature measurement

    SciTech Connect

    Strachan, J.D.; Hendel, H.W.; Lovberg, J.; Nieschmidt, E.B.

    1986-11-01

    One important use of fusion product diagnostics is in the determination of the deuterium ion temperature from the magnitude of the 2.5 MeV d(d,n)/sup 3/He neutron emission. The detectors, calibration methods, and limitations of this technique are reviewed here with emphasis on procedures used at PPPL. In most tokamaks, the ion temperature deduced from neutrons is in reasonable agreement with the ion temperature deduced by other techniques.

  10. Pulsed spallation Neutron Sources

    SciTech Connect

    Carpenter, J.M.

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  11. High-energy neutron detection and spectrometry with superheated emulsions

    NASA Astrophysics Data System (ADS)

    d'Errico, Francesco; Prokofiev, Alexander; Sannikov, Alexander; Schuhmacher, Helmut

    2003-06-01

    The response of some superheated emulsions was investigated using quasi-monoenergetic neutron beams in the 46-134 MeV energy range at the Université Catholique de Louvain, Louvain la Neuve, Belgium and at The Svedberg Laboratory, Uppsala, Sweden. In order to determine the detector response to the high-energy beams, the spectra of incident neutrons were folded over functions modeled after the cross-sections for the neutron-induced production of heavy ions from the detector elements. The cross-sections for fluorine and chlorine were produced in this work by means of the Monte Carlo high-energy transport code HADRON based on the cascade-exciton model of nuclear interactions.

  12. Aerodynamics of Heavy Vehicles

    NASA Astrophysics Data System (ADS)

    Choi, Haecheon; Lee, Jungil; Park, Hyungmin

    2014-01-01

    We present an overview of the aerodynamics of heavy vehicles, such as tractor-trailers, high-speed trains, and buses. We introduce three-dimensional flow structures around simplified model vehicles and heavy vehicles and discuss the flow-control devices used for drag reduction. Finally, we suggest important unsteady flow structures to investigate for the enhancement of aerodynamic performance and future directions for experimental and numerical approaches.

  13. Modes of decay in neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Kumar, B.; Biswal, S. K.; Singh, S. K.; Lahiri, C.; Patra, S. K.

    2016-03-01

    We calculate the ground, first intrinsic excited states and density distribution for neutron-rich thorium and uranium isotopes, within the framework of relativistic mean field (RMF) approach using axially deformed basis. The total nucleon densities are calculated, from which the cluster-structures inside the parent nuclei are determined. The possible modes of decay, like α-decay and β-decay are analyzed. We find the neutron-rich isotopes are stable against α-decay, however they are very much unstable against β-decay. The life time of these nuclei predicted to be tens of second against β-decay.

  14. Integrity of neutron-absorbing components of LWR fuel systems

    SciTech Connect

    Bailey, W.J.; Berting, F.M.

    1991-03-01

    A study of the integrity and behavior of neutron-absorbing components of light-water (LWR) fuel systems was performed by Pacific Northwest Laboratory (PNL) and sponsored by the US Department of Energy (DOE). The components studies include control blades (cruciforms) for boiling-water reactors (BWRs) and rod cluster control assemblies for pressurized-water reactors (PWRs). The results of this study can be useful for understanding the degradation of neutron-absorbing components and for waste management planning and repository design. The report includes examples of the types of degradation, damage, or failures that have been encountered. Conclusions and recommendations are listed. 84 refs.

  15. Comments on the Formation of Globular Clusters from Coalesced Clouds.

    PubMed

    Smith

    1999-11-20

    If a substantial fraction of the proto-Galactic halo was constituted of cloudy structures of sizes 1 kpc or larger, then collisions between these clouds would have been common during the infall of the Galaxy. Such collisions would have shaped the properties of the clouds from which globular clusters formed. If Milky Way globular clusters formed from progenitor clouds which in turn had been constructed from the coalescence of smaller cloud structures, then cluster properties that could naturally be accounted for include: (1) the low percentage of stars in globular clusters relative to the halo field, (2) the chemical homogeneity of globular clusters with respect to heavy elements, and (3) the fact that the lowest metallicity globular clusters are not as metal-poor as some halo field stars.

  16. Process for removing heavy metal compounds from heavy crude oil

    DOEpatents

    Cha, Chang Y.; Boysen, John E.; Branthaver, Jan F.

    1991-01-01

    A process is provided for removing heavy metal compounds from heavy crude oil by mixing the heavy crude oil with tar sand; preheating the mixture to a temperature of about 650.degree. F.; heating said mixture to up to 800.degree. F.; and separating tar sand from the light oils formed during said heating. The heavy metals removed from the heavy oils can be recovered from the spent sand for other uses.

  17. Neutron scattering in Australia

    SciTech Connect

    Knott, R.B.

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  18. Neutron Nucleic Acid Crystallography.

    PubMed

    Chatake, Toshiyuki

    2016-01-01

    The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination. PMID:26227050

  19. Neutron Nucleic Acid Crystallography.

    PubMed

    Chatake, Toshiyuki

    2016-01-01

    The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination.

  20. Coded source neutron imaging

    SciTech Connect

    Bingham, Philip R; Santos-Villalobos, Hector J

    2011-01-01

    Coded aperture techniques have been applied to neutron radiography to address limitations in neutron flux and resolution of neutron detectors in a system labeled coded source imaging (CSI). By coding the neutron source, a magnified imaging system is designed with small spot size aperture holes (10 and 100 m) for improved resolution beyond the detector limits and with many holes in the aperture (50% open) to account for flux losses due to the small pinhole size. An introduction to neutron radiography and coded aperture imaging is presented. A system design is developed for a CSI system with a development of equations for limitations on the system based on the coded image requirements and the neutron source characteristics of size and divergence. Simulation has been applied to the design using McStas to provide qualitative measures of performance with simulations of pinhole array objects followed by a quantitative measure through simulation of a tilted edge and calculation of the modulation transfer function (MTF) from the line spread function. MTF results for both 100um and 10um aperture hole diameters show resolutions matching the hole diameters.