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Sample records for neutron current formulations

  1. Current advances on polynomial resultant formulations

    NASA Astrophysics Data System (ADS)

    Sulaiman, Surajo; Aris, Nor'aini; Ahmad, Shamsatun Nahar

    2017-08-01

    Availability of computer algebra systems (CAS) lead to the resurrection of the resultant method for eliminating one or more variables from the polynomials system. The resultant matrix method has advantages over the Groebner basis and Ritt-Wu method due to their high complexity and storage requirement. This paper focuses on the current resultant matrix formulations and investigates their ability or otherwise towards producing optimal resultant matrices. A determinantal formula that gives exact resultant or a formulation that can minimize the presence of extraneous factors in the resultant formulation is often sought for when certain conditions that it exists can be determined. We present some applications of elimination theory via resultant formulations and examples are given to explain each of the presented settings.

  2. A quasilinear formulation of turbulence driven current

    SciTech Connect

    McDevitt, C. J.; Tang, Xian-Zhu; Guo, Zehua

    2014-02-15

    Non-inductive current drive mechanisms, such as the familiar neoclassical bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work, we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence. In analogy with the traditional neoclassical bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing electrons results in the formation of a steady state plasma current, here we show that resonant scattering of electrons by drift wave microturbulence provides an additional means of determining the equilibrium between trapped and passing electrons. The resulting collisionless equilibrium is shown to result in the formation of an equilibrium current whose magnitude is a function of the thermodynamic forces. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. Utilizing a linearized Fokker-Planck collision operator, the plasma current in the presence of both collisions as well as turbulent stresses is computed, allowing for the relative strength of these two mechanisms to be quantified as a function of collisionality and fluctuation amplitude.

  3. A Quasilinear Formulation of Turbulence Driven Current

    NASA Astrophysics Data System (ADS)

    McDevitt, C. J.; Tang, X. Z.; Guo, Z. H.

    2012-10-01

    Non-inductive current drive mechanisms such as the familiar bootstrap current correspond to an essential component to the realization of steady state tokamak operation. In this work we discuss a novel collisionless mechanism through which a mean plasma current may be driven in the presence of microturbulence (as seen in [1]). In analogy with the traditional bootstrap current drive mechanism, in which the collisional equilibrium established between trapped and passing particles results in the formation of a steady state plasma current, here we show that velocity space scattering by drift wave microturbulence is capable of modifying the equilibrium between trapped and passing particles leading to the generation of a mean plasma current. In the collisionless limit, this current drive mechanism can in turn be balanced either by turbulence mediated electron-ion momentum exchange or radial electron momentum transport. A mean field formulation is utilized to incorporate the above components into a unified framework through which both collisional as well as collisionless current drive mechanisms may be self-consistently treated. [4pt] [1] W. X. Wang et al., 53rd APS-DPP, Salt Lake City, Utah, 2011

  4. Gravitomagnetic tidal currents in rotating neutron stars

    NASA Astrophysics Data System (ADS)

    Poisson, Eric; Douçot, Jean

    2017-02-01

    It was recently revealed that a rotating compact body responds dynamically when it is subjected to a gravitomagnetic tidal field, even when this field is idealized as time independent. The dynamical response is characterized by time-changing internal currents, and it was suspected to originate from zero-frequency g -modes and r -modes driven by the tidal forces. In this paper, we provide additional insights into the phenomenon by examining the tidal response of a rotating body within the framework of post-Newtonian gravity. This approach allows us to develop an intuitive picture for the phenomenon, which relies on the close analogy between post-Newtonian gravity and Maxwell's theory of electromagnetism. In this picture, the coupling between the gravitomagnetic tidal field and the body's rotational velocity is naturally expected to produce an unbalanced Lorentz-like force within the body, and it is this force that is responsible for the tidal currents. The simplicity of the fluid equations in the post-Newtonian setting allows us to provide a complete description of the zero-frequency modes and demonstrate their precise role in the establishment of the tidal currents. We estimate the amplitude of these currents, and find that for neutron-star binaries of relevance to LIGO, the scale of the velocity perturbation is measured in kilometers per second when the rotation period is comparable to 100 milliseconds. This estimate indicates that the tidal currents may have a significant impact on the physics of neutron stars near merger.

  5. MEG forward problem formulation using equivalent surface current densities.

    PubMed

    von Ellenrieder, Nicolás; Muravchik, Carlos H; Nehorai, Arye

    2005-07-01

    We present a formulation for the magnetoencephalography (MEG) forward problem with a layered head model. Traditionally the magnetic field is computed based on the electric potential on the interfaces between the layers. We propose to express the effect of the volumetric currents in terms of an equivalent surface current density on each interface, and obtain the magnetic field based on them. The boundary elements method is used to compute the equivalent current density and the magnetic field for a realistic head geometry. We present numerical results showing that the MEG forward problem is solved correctly with this formulation, and compare it with the performance of the traditional formulation. We conclude that the traditional formulation generally performs better, but still the new formulation is useful in certain situations.

  6. Neutron spin evolution through broadband current sheet spin flippers

    NASA Astrophysics Data System (ADS)

    Stonaha, P.; Hendrie, J.; Lee, W. T.; Pynn, Roger

    2013-10-01

    Controlled manipulation of neutron spin is a critical tool for many neutron scattering techniques. We have constructed current-sheet, neutron spin flippers for use in Spin Echo Scattering Angle Measurement (SESAME) that comprise pairs of open-faced solenoids which introduce an abrupt field reversal at a shared boundary. The magnetic fields generated by the coils have been mapped and compared with both an analytical approximation and a numerical boundary integral calculation. The agreement is generally good, allowing the former method to be used for rapid calculations of the Larmor phase acquired by a neutron passing through the flipper. The evolution of the neutron spin through the current sheets inside the flipper is calculated for various geometries of the current-carrying conductors, including different wire shapes, arrangements, and common imperfections. The flipping efficiency is found to be sensitive to gaps between wires and between current sheets. SESAME requires flippers with high fields and flipping planes inclined to the neutron beam. To avoid substantial neutron depolarization, such flippers require an interdigitated arrangement of wires.

  7. Neutron spin evolution through broadband current sheet spin flippers.

    PubMed

    Stonaha, P; Hendrie, J; Lee, W T; Pynn, Roger

    2013-10-01

    Controlled manipulation of neutron spin is a critical tool for many neutron scattering techniques. We have constructed current-sheet, neutron spin flippers for use in Spin Echo Scattering Angle Measurement (SESAME) that comprise pairs of open-faced solenoids which introduce an abrupt field reversal at a shared boundary. The magnetic fields generated by the coils have been mapped and compared with both an analytical approximation and a numerical boundary integral calculation. The agreement is generally good, allowing the former method to be used for rapid calculations of the Larmor phase acquired by a neutron passing through the flipper. The evolution of the neutron spin through the current sheets inside the flipper is calculated for various geometries of the current-carrying conductors, including different wire shapes, arrangements, and common imperfections. The flipping efficiency is found to be sensitive to gaps between wires and between current sheets. SESAME requires flippers with high fields and flipping planes inclined to the neutron beam. To avoid substantial neutron depolarization, such flippers require an interdigitated arrangement of wires.

  8. A Review of Currently Available Fenofibrate and Fenofibric Acid Formulations.

    PubMed

    Ling, Hua; Luoma, John T; Hilleman, Daniel

    2013-04-01

    Fenofibrate is a third-generation fibric acid derivative indicated as a monotherapy to reduce elevated low-density lipoprotein cholesterol, total cholesterol, triglycerides, and apolipoprotein B; to increase high-density lipoprotein cholesterol in patients with primary hyperlipidemia or mixed dyslipidemia; and to reduce triglycerides in patients with severe hypertriglyceridemia. In this review, the key characteristics of available fenofibrate formulations are examined. A literature search was conducted, focusing on comparative studies examining bioavailability, food effects, absorption, and lipid efficacy. Fenofibrate is highly lipophilic, virtually insoluble in water, and poorly absorbed. Coadministration with meals was necessary to maximize bioavailability of early formulations. Micronized and nanoparticle formulations of fenofibrate with reduced particle sizes were developed, resulting in greater solubility, improved bioavailability, and in some cases, the ability to be given irrespective of food. A recently introduced hydrophilic choline salt of fenofibric acid also can be taken without regard to meals, is absorbed throughout the gastrointestinal tract, has the highest bioavailability among marketed formulations, and is approved for coadministration with a statin. Differences in bioavailability of fenofibrate formulations have resulted in low-dose (40 - 67) mg and standard-dose (120 - 200 mg) formulations. Different formulations are not equivalent on a milligram-to-milligram basis. In order to prevent medication errors, resulting in underdosing or overdosing with attendant consequences, it is important for healthcare providers to recognize that the formulations of fenofibrate and fenofibric acid that are currently available vary substantially in relation to food effect, equivalency on a milligram-to-milligram basis, and indication to be coadministered with a statin.

  9. A Review of Currently Available Fenofibrate and Fenofibric Acid Formulations

    PubMed Central

    Ling, Hua; Luoma, John T.; Hilleman, Daniel

    2013-01-01

    Fenofibrate is a third-generation fibric acid derivative indicated as a monotherapy to reduce elevated low-density lipoprotein cholesterol, total cholesterol, triglycerides, and apolipoprotein B; to increase high-density lipoprotein cholesterol in patients with primary hyperlipidemia or mixed dyslipidemia; and to reduce triglycerides in patients with severe hypertriglyceridemia. In this review, the key characteristics of available fenofibrate formulations are examined. A literature search was conducted, focusing on comparative studies examining bioavailability, food effects, absorption, and lipid efficacy. Fenofibrate is highly lipophilic, virtually insoluble in water, and poorly absorbed. Coadministration with meals was necessary to maximize bioavailability of early formulations. Micronized and nanoparticle formulations of fenofibrate with reduced particle sizes were developed, resulting in greater solubility, improved bioavailability, and in some cases, the ability to be given irrespective of food. A recently introduced hydrophilic choline salt of fenofibric acid also can be taken without regard to meals, is absorbed throughout the gastrointestinal tract, has the highest bioavailability among marketed formulations, and is approved for coadministration with a statin. Differences in bioavailability of fenofibrate formulations have resulted in low-dose (40 - 67) mg and standard-dose (120 - 200 mg) formulations. Different formulations are not equivalent on a milligram-to-milligram basis. In order to prevent medication errors, resulting in underdosing or overdosing with attendant consequences, it is important for healthcare providers to recognize that the formulations of fenofibrate and fenofibric acid that are currently available vary substantially in relation to food effect, equivalency on a milligram-to-milligram basis, and indication to be coadministered with a statin. PMID:28352420

  10. Gyrotron-driven high current ECR ion source for boron-neutron capture therapy neutron generator

    NASA Astrophysics Data System (ADS)

    Skalyga, V.; Izotov, I.; Golubev, S.; Razin, S.; Sidorov, A.; Maslennikova, A.; Volovecky, A.; Kalvas, T.; Koivisto, H.; Tarvainen, O.

    2014-12-01

    Boron-neutron capture therapy (BNCT) is a perspective treatment method for radiation resistant tumors. Unfortunately its development is strongly held back by a several physical and medical problems. Neutron sources for BNCT currently are limited to nuclear reactors and accelerators. For wide spread of BNCT investigations more compact and cheap neutron source would be much more preferable. In present paper an approach for compact D-D neutron generator creation based on a high current ECR ion source is suggested. Results on dense proton beams production are presented. A possibility of ion beams formation with current density up to 600 mA/cm2 is demonstrated. Estimations based on obtained experimental results show that neutron target bombarded by such deuteron beams would theoretically yield a neutron flux density up to 6·1010 cm-2/s. Thus, neutron generator based on a high-current deuteron ECR source with a powerful plasma heating by gyrotron radiation could fulfill the BNCT requirements significantly lower price, smaller size and ease of operation in comparison with existing reactors and accelerators.

  11. Reproducibility of neutron activated Sm-153 oral dose formulations intended for human administration.

    PubMed

    Yeong, C H; Blackshaw, P E; Ng, K H; Abdullah, B J J; Blaauw, M; Dansereau, R J; Perkins, A C

    2011-09-01

    Neutron activation of Sm-152 offers a method of radiolabeling for the in vivo study of oral dose formulations by gamma scintigraphy. Reproducibility measurements are needed to ensure the robustness of clinical studies. 204 enteric-coated guaifenesin core tablets (10mg of Sm(2)O(3)) were irradiated by thermal neutrons to achieve 1 MBq at 48 h. Administered activities were 0.86±0.03 MBq. Good reproducibility (CV=3.5%) was observed over 24 weeks ensuring that volunteer doses were within the dose reference level of 0.8 mSv. Copyright © 2011 Elsevier Ltd. All rights reserved.

  12. A neutron diagnostic for high current deuterium beams

    SciTech Connect

    Rebai, M.; Perelli Cippo, E.; Cavenago, M.; Dalla Palma, M.; Pasqualotto, R.; Tollin, M.; Croci, G.; Gervasini, G.; Ghezzi, F.; Grosso, G.; Tardocchi, M.; Murtas, F.; Gorini, G.

    2012-02-15

    A neutron diagnostic for high current deuterium beams is proposed for installation on the spectral shear interferometry for direct electric field reconstruction (SPIDER, Source for Production of Ion of Deuterium Extracted from RF plasma) test beam facility. The proposed detection system is called Close-contact Neutron Emission Surface Mapping (CNESM). The diagnostic aims at providing the map of the neutron emission on the beam dump surface by placing a detector in close contact, right behind the dump. CNESM uses gas electron multiplier detectors equipped with a cathode that also serves as neutron-proton converter foil. The cathode is made of a thin polythene film and an aluminium film; it is designed for detection of neutrons of energy >2.2 MeV with an incidence angle < 45 deg. CNESM was designed on the basis of simulations of the different steps from the deuteron beam interaction with the beam dump to the neutron detection in the nGEM. Neutron scattering was simulated with the MCNPX code. CNESM on SPIDER is a first step towards the application of this diagnostic technique to the MITICA beam test facility, where it will be used to resolve the horizontal profile of the beam intensity.

  13. Neutron detection using a current biased kinetic inductance detector

    NASA Astrophysics Data System (ADS)

    Shishido, Hiroaki; Miyajima, Shigeyuki; Narukami, Yoshito; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Arai, Masatoshi; Hidaka, Mutsuo; Fujimaki, Akira; Ishida, Takekazu

    2015-12-01

    We demonstrate neutron detection using a solid state superconducting current biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line of 1 μm width and 40 nm thickness. 10B-enriched neutron absorber layer of 150 nm thickness is placed on top of the CB-KID. Our neutron detectors are able to operate in a wide superconducting region in the bias current-temperature diagram. This is in sharp contrast with our preceding current-biased transition edge detector, which can operate only in a narrow range just below the superconducting critical temperature. The full width at half maximum of the signals remains of the order of a few tens of ns, which confirms the high speed operation of our detectors.

  14. Neutron detection using a current biased kinetic inductance detector

    SciTech Connect

    Shishido, Hiroaki Miyajima, Shigeyuki; Ishida, Takekazu; Narukami, Yoshito; Oikawa, Kenichi; Harada, Masahide; Oku, Takayuki; Arai, Masatoshi; Hidaka, Mutsuo; Fujimaki, Akira

    2015-12-07

    We demonstrate neutron detection using a solid state superconducting current biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line of 1 μm width and 40 nm thickness. {sup 10}B-enriched neutron absorber layer of 150 nm thickness is placed on top of the CB-KID. Our neutron detectors are able to operate in a wide superconducting region in the bias current–temperature diagram. This is in sharp contrast with our preceding current-biased transition edge detector, which can operate only in a narrow range just below the superconducting critical temperature. The full width at half maximum of the signals remains of the order of a few tens of ns, which confirms the high speed operation of our detectors.

  15. Secondary-neutron-yield measurements by current-mode detectors

    SciTech Connect

    Glebov, V. Yu.; Meyerhofer, D. D.; Stoeckl, C.; Zuegel, J. D.

    2001-01-01

    Secondary deuterium--tritium (DT) neutrons from pure-deuterium inertial confinement fusion targets can be used to diagnose the fuel areal density. Single-hit detectors like LaNSA at Lawrence Livermore National Laboratory or MEDUSA at the Laboratory for Laser Energetics (LLE) saturate for fairly low secondary DT- and primary DD-neutron yields. These detectors are not suitable for the high-yield, direct-drive implosion experiments currently carried out on the 30 kJ, 60 beam OMEGA laser system or for future cryogenic-capsule experiments on OMEGA. The status of several current-mode detectors (e.g., a single scintillator and a photomultiplier tube) now being developed at LLE for secondary-neutron-yield measurements is described.

  16. Axial U(1) current in Grabowska and Kaplan's formulation

    NASA Astrophysics Data System (ADS)

    Hamada, Yu; Kawai, Hikaru

    2017-06-01

    Recently, Grabowska and Kaplan [Phys. Rev. Lett. 116, 211602 (2016); Phys. Rev. D 94, 114504 (2016)] suggested a nonperturbative formulation of a chiral gauge theory, which consists of the conventional domain-wall fermion and a gauge field that evolves by gradient flow from one domain wall to the other. We introduce two sets of domain-wall fermions belonging to complex conjugate representations so that the effective theory is a 4D vector-like gauge theory. Then, as a natural definition of the axial-vector current, we consider a current that generates simultaneous phase transformations for the massless modes in 4 dimensions. However, this current is exactly conserved and does not reproduce the correct anomaly. In order to investigate this point precisely, we consider the mechanism of the conservation. We find that this current includes not only the axial current on the domain wall but also a contribution from the bulk, which is nonlocal in the sense of 4D fields. Therefore, the local current is obtained by subtracting the bulk contribution from it.

  17. The formulation of polyhedral boranes for the boron neutron capture therapy of cancer.

    PubMed

    Calabrese, Gianpiero; Nesnas, John J; Barbu, Eugen; Fatouros, Dimitris; Tsibouklis, John

    2012-02-01

    The early promise of boron neutron capture therapy as a method for the treatment of cancer has been inhibited by the inherent toxicity associated with therapeutically useful doses of ¹⁰B-containing pharmacophores, the need for target-tissue specificity and the challenges imposed by biological barriers. Although developments in the synthetic chemistry of polyhedral boranes have addressed issues of toxicity to a considerable extent, the optimisation of the transport and the delivery of boronated agents to the site of action--the subject of this review--is a challenge that is addressed by the development of innovative formulation strategies.

  18. Current status of amorphous formulation and other special dosage forms as formulations for early clinical phases.

    PubMed

    Kawakami, Kohsaku

    2009-09-01

    Although most chemists in the pharmaceutical industry have a good understanding on favorable physicochemical properties for drug candidates, formulators must still deal with many challenging candidates. On the other hand, formulators are not allowed to spend much time on formulation development for early phases of the clinical studies. Thus, it is basically difficult to apply special dosage form technologies to the candidates for the first-in-human formulations. Despite the availability of numerous reviews on oral special dosage forms, information on their applicability as the early phase formulation has been limited. This article describes quick review on the oral special dosage forms that may be applied to the early clinical formulations, followed by discussion focused on the amorphous formulations, which still has relatively many issues to be proved for the general use. The major problems that inhibit the use of the amorphous formulation are difficulty in the manufacturing and the poor chemical/physical stability. Notably, the poor physical stability can be critical, because of not the poor stability itself but the difficulty in the timely evaluation in the preclinical developmental timeframes. Research directions of the amorphous formulations are suggested to utilize this promising technology without disturbing the preclinical developmental timelines.

  19. Ernst formulation of axisymmetric fields in f (R ) gravity: Applications to neutron stars and gravitational waves

    NASA Astrophysics Data System (ADS)

    Suvorov, Arthur George; Melatos, Andrew

    2016-08-01

    The Ernst formulation of the Einstein equations is generalized to accommodate f (R ) theories of gravity. It is shown that, as in general relativity, the axisymmetric f (R ) field equations for a vacuum spacetime that is either stationary or cylindrically symmetric reduce to a single, nonlinear differential equation for a complex-valued scalar function. As a worked example, we apply the generalized Ernst equations to derive a f (R ) generalization of the Zipoy-Voorhees metric, which may be used to describe the gravitational field outside of an ellipsoidal neutron star. We also apply the theory to investigate the phase speed of large-amplitude gravitational waves in f (R ) gravity in the context of solitonlike solutions that display shock-wave behavior across the causal boundary.

  20. Current status of the PSG Monte Carlo neutron transport code

    SciTech Connect

    Leppaenen, J.

    2006-07-01

    PSG is a new Monte Carlo neutron transport code, developed at the Technical Research Centre of Finland (VTT). The code is mainly intended for fuel assembly-level reactor physics calculations, such as group constant generation for deterministic reactor simulator codes. This paper presents the current status of the project and the essential capabilities of the code. Although the main application of PSG is in lattice calculations, the geometry is not restricted in two dimensions. This paper presents the validation of PSG against the experimental results of the three-dimensional MOX fuelled VENUS-2 reactor dosimetry benchmark. (authors)

  1. Electromagnetic Emission from Long-lived Binary Neutron Star Merger Remnants. I. Formulation of the Problem

    NASA Astrophysics Data System (ADS)

    Siegel, Daniel M.; Ciolfi, Riccardo

    2016-03-01

    Binary neutron star (BNS) mergers are the leading model to explain the phenomenology of short gamma-ray bursts (SGRBs). Recent observations of long-lasting X-ray afterglows of SGRBs challenge standard paradigms and indicate that in a large fraction of events a long-lived neutron star (NS) may be formed rather than a black hole. Understanding the mechanisms underlying these afterglows is necessary in order to address the open questions concerning the nature of SGRB central engines. However, recent theoretical progress has been hampered by the fact that the timescales of interest for the afterglow emission are inaccessible to numerical relativity simulations. Here we present a detailed model to bridge the gap between numerical simulations of the merger process and the relevant timescales for the afterglows, assuming that the merger results in a long-lived NS. This model is formulated in terms of a set of coupled differential equations that follow the evolution of the post-merger system and predict its electromagnetic (EM) emission in a self-consistent way, starting from initial data that can be extracted from BNS merger simulations. The model presented here also allows us to search for suitable EM counterparts for multimessenger astronomy, which is expected to become reality within the next few years thanks to ground-based GW detectors such as advanced LIGO and Virgo. This paper discusses the formulation and implementation of the model. In a companion paper, we employ this model to predict the EM emission from ∼ {10}-2 to ∼ {10}7 {{s}} after a BNS merger and discuss the implications in the context of SGRBs and multimessenger astronomy.

  2. Constraint damping of the conformal and covariant formulation of the Z4 system in simulations of binary neutron stars

    NASA Astrophysics Data System (ADS)

    Alic, Daniela; Kastaun, Wolfgang; Rezzolla, Luciano

    2013-09-01

    Following previous work in vacuum spacetimes, we investigate the constraint-damping properties in the presence of matter of the recently developed traceless, conformal and covariant Z4 (CCZ4) formulation of the Einstein equations. First, we evolve an isolated neutron star with an ideal gas equation of state and subject to a constraint-violating perturbation. We compare the evolution of the constraints using the CCZ4 and Baumgarte-Shibata-Shapiro-Nakamura-Oohara-Kojima (BSSNOK) systems. Second, we study the collapse of an unstable spherical star to a black hole. Finally, we evolve binary neutron star systems over several orbits until the merger, the formation of a black hole, and up to the ringdown. We show that the CCZ4 formulation is stable in the presence of matter and that the constraint violations are 1 or more orders of magnitude smaller than for the BSSNOK formulation. Furthermore, by comparing the CCZ4 and the BSSNOK formulations also for neutron star binaries with large initial constraint violations, we investigate their influence on the errors on physical quantities. We also give a new, simple and robust prescription for the damping parameter that removes the instabilities found when using the fully covariant version of CCZ4 in the evolution of black holes. Overall, we find that at essentially the same computational costs, the CCZ4 formulation provides solutions that are stable and with a considerably smaller violation of the Hamiltonian constraint than the BSSNOK formulation. We also find that the performance of the CCZ4 formulation is very similar to another conformal and traceless, but noncovariant formulation of the Z4 system, i.e., the Z4c formulation.

  3. Review of current neutron detection systems for emergency response

    SciTech Connect

    Mukhopadhyay, Sanjoy; Maurer, Richard; Guss, Paul; Kruschwitz, Craig

    2014-09-05

    Neutron detectors are utilized in a myriad of applications—from safeguarding special nuclear materials (SNM) to determining lattice spacing in soft materials. The transformational changes taking place in neutron detection and imaging techniques in the last few years are largely being driven by the global shortage of helium-3 (3He). This article reviews the status of neutron sensors used specifically for SNM detection in radiological emergency response. These neutron detectors must be highly efficient, be rugged, have fast electronics to measure neutron multiplicity, and be capable of measuring direction of the neutron sources and possibly image them with high spatial resolution. Neutron detection is an indirect physical process: neutrons react with nuclei in materials to initiate the release of one or more charged particles that produce electric signals that can be processed by the detection system. Therefore, neutron detection requires conversion materials as active elements of the detection system; these materials may include boron-10 (10B), lithium-6 (6Li), and gadollinium-157 (157Gd), to name a few, but the number of materials available for neutron detection is limited. However, in recent years, pulse-shape-discriminating plastic scintillators, scintillators made of helium-4 (4He) under high pressure, pillar and trench semiconductor diodes, and exotic semiconductor neutron detectors made from uranium oxide and other materials have widely expanded the parameter space in neutron detection methodology. In this article we will pay special attention to semiconductor-based neutron sensors. Finally, modern microfabricated nanotubes covered inside with neutron converter materials and with very high aspect ratios for better charge transport will be discussed.

  4. Review of current neutron detection systems for emergency response

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sanjoy; Maurer, Richard; Guss, Paul; Kruschwitz, Craig

    2014-09-01

    Neutron detectors are used in a myriad of applications—from safeguarding special nuclear materials (SNM) to determining lattice spacing in soft materials. The transformational changes taking place in neutron detection and imaging techniques in the last few years are largely being driven by the global shortage of helium-3 (3He). This article reviews the status of neutron sensors used specifically for SNM detection in radiological emergency response. These neutron detectors must be highly efficient, be rugged, have fast electronics to measure neutron multiplicity, and be capable of measuring direction of the neutron sources and possibly image them with high spatial resolution. Neutron detection is an indirect physical process: neutrons react with nuclei in materials to initiate the release of one or more charged particles that produce electric signals that can be processed by the detection system. Therefore, neutron detection requires conversion materials as active elements of the detection system; these materials may include boron-10 (10B), lithium-6 (6Li), and gadollinium-157 (157Gd), to name a few, but the number of materials available for neutron detection is limited. However, in recent years, pulse-shape-discriminating plastic scintillators, scintillators made of helium-4 (4He) under high pressure, pillar and trench semiconductor diodes, and exotic semiconductor neutron detectors made from uranium oxide and other materials have widely expanded the parameter space in neutron detection methodology. In this article we will pay special attention to semiconductor-based neutron sensors. Modern microfabricated nanotubes covered inside with neutron converter materials and with very high aspect ratios for better charge transport will be discussed.

  5. Review of current neutron detection systems for emergency response

    DOE PAGES

    Mukhopadhyay, Sanjoy; Maurer, Richard; Guss, Paul; ...

    2014-09-05

    Neutron detectors are utilized in a myriad of applications—from safeguarding special nuclear materials (SNM) to determining lattice spacing in soft materials. The transformational changes taking place in neutron detection and imaging techniques in the last few years are largely being driven by the global shortage of helium-3 (3He). This article reviews the status of neutron sensors used specifically for SNM detection in radiological emergency response. These neutron detectors must be highly efficient, be rugged, have fast electronics to measure neutron multiplicity, and be capable of measuring direction of the neutron sources and possibly image them with high spatial resolution. Neutronmore » detection is an indirect physical process: neutrons react with nuclei in materials to initiate the release of one or more charged particles that produce electric signals that can be processed by the detection system. Therefore, neutron detection requires conversion materials as active elements of the detection system; these materials may include boron-10 (10B), lithium-6 (6Li), and gadollinium-157 (157Gd), to name a few, but the number of materials available for neutron detection is limited. However, in recent years, pulse-shape-discriminating plastic scintillators, scintillators made of helium-4 (4He) under high pressure, pillar and trench semiconductor diodes, and exotic semiconductor neutron detectors made from uranium oxide and other materials have widely expanded the parameter space in neutron detection methodology. In this article we will pay special attention to semiconductor-based neutron sensors. Finally, modern microfabricated nanotubes covered inside with neutron converter materials and with very high aspect ratios for better charge transport will be discussed.« less

  6. A time-dependent neutron transport method of characteristics formulation with time derivative propagation

    SciTech Connect

    Hoffman, Adam J. Lee, John C.

    2016-02-15

    A new time-dependent Method of Characteristics (MOC) formulation for nuclear reactor kinetics was developed utilizing angular flux time-derivative propagation. This method avoids the requirement of storing the angular flux at previous points in time to represent a discretized time derivative; instead, an equation for the angular flux time derivative along 1D spatial characteristics is derived and solved concurrently with the 1D transport characteristic equation. This approach allows the angular flux time derivative to be recast principally in terms of the neutron source time derivatives, which are approximated to high-order accuracy using the backward differentiation formula (BDF). This approach, called Source Derivative Propagation (SDP), drastically reduces the memory requirements of time-dependent MOC relative to methods that require storing the angular flux. An SDP method was developed for 2D and 3D applications and implemented in the computer code DeCART in 2D. DeCART was used to model two reactor transient benchmarks: a modified TWIGL problem and a C5G7 transient. The SDP method accurately and efficiently replicated the solution of the conventional time-dependent MOC method using two orders of magnitude less memory.

  7. A time-dependent neutron transport method of characteristics formulation with time derivative propagation

    NASA Astrophysics Data System (ADS)

    Hoffman, Adam J.; Lee, John C.

    2016-02-01

    A new time-dependent Method of Characteristics (MOC) formulation for nuclear reactor kinetics was developed utilizing angular flux time-derivative propagation. This method avoids the requirement of storing the angular flux at previous points in time to represent a discretized time derivative; instead, an equation for the angular flux time derivative along 1D spatial characteristics is derived and solved concurrently with the 1D transport characteristic equation. This approach allows the angular flux time derivative to be recast principally in terms of the neutron source time derivatives, which are approximated to high-order accuracy using the backward differentiation formula (BDF). This approach, called Source Derivative Propagation (SDP), drastically reduces the memory requirements of time-dependent MOC relative to methods that require storing the angular flux. An SDP method was developed for 2D and 3D applications and implemented in the computer code DeCART in 2D. DeCART was used to model two reactor transient benchmarks: a modified TWIGL problem and a C5G7 transient. The SDP method accurately and efficiently replicated the solution of the conventional time-dependent MOC method using two orders of magnitude less memory.

  8. High-Current Experiments for Accelerator-Based Neutron Capture Therapy Applications

    SciTech Connect

    Gierga, D.P.; Klinkowstein, R.E.; Hughey, B.H.; Shefer, R.E.; Yanch, J.C.; Blackburn, B.W.

    1999-06-06

    Several accelerator-based neutron capture therapy applications are under development. These applications include boron neutron capture therapy for glioblastoma multiform and boron neutron capture synovectomy (BNCS) for rheumatoid arthritis. These modalities use accelerator-based charged-particle reactions to create a suitable neutron source. Neutrons are produced using a high-current, 2-MV terminal tandem accelerator. For these applications to be feasible, high accelerator beam currents must be routinely achievable. An effort was undertaken to explore the operating regime of the accelerator in the milliampere range. In preparation for high-current operation of the accelerator, computer simulations of charged-particle beam optics were performed to establish high-current operating conditions. Herein we describe high beam current simulations and high beam current operation of the accelerator.

  9. High neutronic efficiency, low current targets for accelerator-based BNCT applications

    SciTech Connect

    Powell, J.R.; Ludewig, H.; Todosow, M.

    1998-08-01

    The neutronic efficiency of target/filters for accelerator-based BNCT applications is measured by the proton current required to achieve a desirable neutron current at the treatment port (10{sup 9} n/cm{sup 2}/s). In this paper the authors describe two possible targeyt/filter concepts wihch minimize the required current. Both concepts are based on the Li-7 (p,n)Be-7 reaction. Targets that operate near the threshold energy generate neutrons that are close tothe desired energy for BNCT treatment. Thus, the filter can be extremely thin ({approximately} 5 cm iron). However, this approach has an extremely low neutron yield (n/p {approximately} 1.0({minus}6)), thus requiring a high proton current. The proposed solutino is to design a target consisting of multiple extremely thin targets (proton energy loss per target {approximately} 10 keV), and re-accelerate the protons between each target. Targets operating at ihgher proton energies ({approximately} 2.5 MeV) have a much higher yield (n/p {approximately} 1.0({minus}4)). However, at these energies the maximum neutron energy is approximately 800 keV, and thus a neutron filter is required to degrade the average neutron energy to the range of interest for BNCT (10--20 keV). A neutron filter consisting of fluorine compounds and iron has been investigated for this case. Typically a proton current of approximately 5 mA is required to generate the desired neutron current at the treatment port. The efficiency of these filter designs can be further increased by incorporating neutron reflectors that are co-axial with the neutron source. These reflectors are made of materials which have high scattering cross sections in the range 0.1--1.0 MeV.

  10. An boldsymbol{E} -based mixed formulation for a time-dependent eddy current problem

    NASA Astrophysics Data System (ADS)

    Acevedo, Ramiro; Meddahi, Salim; Rodriguez, Rodolfo

    2009-12-01

    In this paper, we analyze a mixed form of a time-dependent eddy current problem formulated in terms of the electric field boldsymbol{E} . We show that this formulation admits a well-posed saddle point structure when the constraints satisfied by the primary unknown in the dielectric material are handled by means of a Lagrange multiplier. We use Nedelec edge elements and standard nodal finite elements to define a semi-discrete Galerkin scheme. Furthermore, we introduce the corresponding backward-Euler fully-discrete formulation and prove error estimates.

  11. High yield neutron generator based on a high-current gasdynamic electron cyclotron resonance ion source

    SciTech Connect

    Skalyga, V.; Sidorov, A.; Izotov, I.; Golubev, S.; Razin, S.; Strelkov, A.; Tarvainen, O.; Koivisto, H.; Kalvas, T.

    2015-09-07

    In present paper, an approach for high yield compact D-D neutron generator based on a high current gasdynamic electron cyclotron resonance ion source is suggested. Results on dense pulsed deuteron beam production with current up to 500 mA and current density up to 750 mA/cm{sup 2} are demonstrated. Neutron yield from D{sub 2}O and TiD{sub 2} targets was measured in case of its bombardment by pulsed 300 mA D{sup +} beam with 45 keV energy. Neutron yield density at target surface of 10{sup 9} s{sup −1} cm{sup −2} was detected with a system of two {sup 3}He proportional counters. Estimations based on obtained experimental results show that neutron yield from a high quality TiD{sub 2} target bombarded by D{sup +} beam demonstrated in present work accelerated to 100 keV could reach 6 × 10{sup 10} s{sup −1} cm{sup −2}. It is discussed that compact neutron generator with such characteristics could be perspective for a number of applications like boron neutron capture therapy, security systems based on neutron scanning, and neutronography.

  12. Neutron generator for BNCT based on high current ECR ion source with gyrotron plasma heating.

    PubMed

    Skalyga, V; Izotov, I; Golubev, S; Razin, S; Sidorov, A; Maslennikova, A; Volovecky, A; Kalvas, T; Koivisto, H; Tarvainen, O

    2015-12-01

    BNCT development nowadays is constrained by a progress in neutron sources design. Creation of a cheap and compact intense neutron source would significantly simplify trial treatments avoiding use of expensive and complicated nuclear reactors and accelerators. D-D or D-T neutron generator is one of alternative types of such sources for. A so-called high current quasi-gasdynamic ECR ion source with plasma heating by millimeter wave gyrotron radiation is suggested to be used in a scheme of D-D neutron generator in the present work. Ion source of that type was developed in the Institute of Applied Physics of Russian Academy of Sciences (Nizhny Novgorod, Russia). It can produce deuteron ion beams with current density up to 700-800 mA/cm(2). Generation of the neutron flux with density at the level of 7-8·10(10) s(-1) cm(-2) at the target surface could be obtained in case of TiD2 target bombardment with deuteron beam accelerated to 100 keV. Estimations show that it is enough for formation of epithermal neutron flux with density higher than 10(9) s(-1) cm(-2) suitable for BNCT. Important advantage of described approach is absence of Tritium in the scheme. First experiments performed in pulsed regime with 300 mA, 45 kV deuteron beam directed to D2O target demonstrated 10(9) s(-1) neutron flux. This value corresponds to theoretical estimations and proofs prospects of neutron generator development based on high current quasi-gasdynamic ECR ion source. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. CVD Diamond Detectors for Current Mode Neutron Time-of-Flight Spectroscopy at OMEGA/NIF

    SciTech Connect

    G. J. Schmid; V. Yu. Glebov; A. V. Friensehner; D. R. Hargrove; S. P. Hatchett; N. Izumi; R. A. Lerche; T. W. Phillips; T. C. Sangster; C. Silbernagel; C. Stoecki

    2001-07-01

    We have performed pulsed neutron and pulsed laser tests of a CVD diamond detector manufactured from DIAFILM, a commercial grade of CVD diamond. The laser tests were performed at the short pulse UV laser at Bechtel Nevada in Livermore, CA. The pulsed neutrons were provided by DT capsule implosions at the OMEGA laser fusion facility in Rochester, NY. From these tests, we have determined the impulse response to be 250 ps fwhm for an applied E-field of 500 V/mm. Additionally, we have determined the sensitivity to be 2.4 mA/W at 500 V/mm and 4.0 mA/W at 1000 V/mm. These values are approximately 2 to 5x times higher than those reported for natural Type IIa diamond at similar E-field and thickness (1mm). These characteristics allow us to conceive of a neutron time-of-flight current mode spectrometer based on CVD diamond. Such an instrument would sit inside the laser fusion target chamber close to target chamber center (TCC), and would record neutron spectra fast enough such that backscattered neutrons and x-rays from the target chamber wall would not be a concern. The acquired neutron spectra could then be used to extract DD fuel areal density from the downscattered secondary to secondary ratio.

  14. Current and emerging formulation strategies for the effective transdermal delivery of HIV inhibitors

    PubMed Central

    Ham, Anthony S; Buckheit, Robert W

    2015-01-01

    Current and emerging formulation strategies for skin permeation are poised to open the transdermal drug delivery to a broader range of small molecule compounds that do not fit the traditional requirements for successful transdermal drug delivery, allowing the development of new patch technologies to deliver antiretroviral drugs that were previously incapable of being delivered through transdermal means. Transdermal drug delivery offers several distinct advantages over traditional dosage forms. Current antiretroviral drugs used for the treatment of HIV infection include a variety of highly active small molecule compounds with significantly limited skin permeability, and thus new and novel means of enhancing transport through the skin are needed. Current and emerging formulation strategies are poised to open the transdermal drug delivery to a broader range of compounds that do not fit the traditional requirements for successful transdermal drug delivery, allowing the development of new patch technologies to deliver antiretroviral drugs that were previously incapable of being delivered through transdermal means. Thus, with continuing research into skin permeability and patch formulation strategies, there is a large potential for antiretroviral transdermal drug delivery. PMID:25690088

  15. Current and emerging formulation strategies for the effective transdermal delivery of HIV inhibitors.

    PubMed

    Ham, Anthony S; Buckheit, Robert W

    2015-02-01

    Current and emerging formulation strategies for skin permeation are poised to open the transdermal drug delivery to a broader range of small molecule compounds that do not fit the traditional requirements for successful transdermal drug delivery, allowing the development of new patch technologies to deliver antiretroviral drugs that were previously incapable of being delivered through transdermal means. Transdermal drug delivery offers several distinct advantages over traditional dosage forms. Current antiretroviral drugs used for the treatment of HIV infection include a variety of highly active small molecule compounds with significantly limited skin permeability, and thus new and novel means of enhancing transport through the skin are needed. Current and emerging formulation strategies are poised to open the transdermal drug delivery to a broader range of compounds that do not fit the traditional requirements for successful transdermal drug delivery, allowing the development of new patch technologies to deliver antiretroviral drugs that were previously incapable of being delivered through transdermal means. Thus, with continuing research into skin permeability and patch formulation strategies, there is a large potential for antiretroviral transdermal drug delivery.

  16. Clinical and experimental studies on polyherbal formulations for diabetes: current status and future prospective.

    PubMed

    Ghorbani, Ahmad

    2014-07-01

    Diabetes is a leading cause of morbidity and mortality in the world. There is currently an active search for antidiabetic drugs with greater effectiveness with fewer and less adverse side effects. Although numerous individual herbs have been experimentally or clinically reported to possess antidiabetic effects, considerably less research has been conducted on polyherbal compounds. It is believed that herbal compounds containing multiple plant products have synergistic antidiabetic effects and could enhance the desired actions. Several polyherbal formulations have been studied as therapeutic agents in diabetes management. To describe the current state of research on polyherbal compounds in the treatment of diabetes, an extensive review of literature was undertaken on several major databases. This paper presents what is known about the efficacy of these polyherbal formulations and compare their antidiabetic effects with those of current oral hypoglycemic drugs as reference. The percent decrease in blood glucose, lipids and other biochemical parameters achieved by each product in diabetic animals and patients is reported. Also, the possible mechanisms responsible for hypoglycemic action of polyherbal formulations are discussed.

  17. Formulation approaches to pediatric oral drug delivery: benefits and limitations of current platforms

    PubMed Central

    Lopez, Felipe L; Ernest, Terry B; Tuleu, Catherine; Gul, Mine Orlu

    2015-01-01

    Introduction: Most conventional drug delivery systems are not acceptable for pediatric patients as they differ in their developmental status and dosing requirements from other subsets of the population. Technology platforms are required to aid the development of age-appropriate medicines to maximize patient acceptability while maintaining safety, efficacy, accessibility and affordability. Areas covered: The current approaches and novel developments in the field of age-appropriate drug delivery for pediatric patients are critically discussed including patient-centric formulations, administration devices and packaging systems. Expert opinion: Despite the incentives provided by recent regulatory modifications and the efforts of formulation scientists, there is still a need for implementation of pharmaceutical technologies that enable the manufacture of licensed age-appropriate formulations. Harmonization of endeavors from regulators, industry and academia by sharing learning associated with data obtained from pediatric investigation plans, product development pathways and scientific projects would be the way forward to speed up bench-to-market age appropriate formulation development. A collaborative approach will benefit not only pediatrics, but other patient populations such as geriatrics would also benefit from an accelerated patient-centric approach to drug delivery. PMID:26165848

  18. Boron neutron capture therapy of brain tumors: past history, current status, and future potential.

    PubMed

    Barth, R F; Soloway, A H; Brugger, R M

    1996-01-01

    Boron neutron capture therapy (BNCT) is based on the nuclear reaction that occurs when boron-10 is irradiated with low-energy thermal neutrons to yield alpha particles and recoiling lithium-7 nuclei. High-grade astrocytomas, glioblastoma multiforme, and metastatic brain tumors constitute a major group of neoplasms for which there is no effective treatment. There is growing interest in using BNCT in combination with surgery to treat patients with primary, and possibly metastatic brain tumors. For BNCT to be successful, a large number of 10B atoms must be localized on or preferably within neoplastic cells, and a sufficient number of thermal neutrons must reach and be absorbed by the 10B atoms to sustain a lethal 10B(n, alpha)7 Li reaction. Two major questions will be addressed in this review. First, how can a large number of 10B atoms be delivered selectively to cancer cells? Second, how can a high fluence of neutrons be delivered to the tumor? Two boron compounds currently are being used clinically, sodium borocaptate (BSH) and boronophenylalanine (BPA), and a number of new delivery agents are under investigation, including boronated porphyrins, nucleosides, amino acids, polyamines, monoclonal and bispecific antibodies, liposomes, and epidermal growth factor. These will be discussed, and potential problems associated with their use as boron delivery agents will be considered. Nuclear reactors, currently, are the only source of neutrons for BNCT, and the fission process within the core produces a mixture of lower-energy thermal and epithermal neutrons, fast or high (> 10,000 eV) energy neutrons, and gamma rays. Although thermal neutron beams have been used clinically in Japan to treat patients with brain tumors and cutaneous melanomas, epithermal neutron beams should be more useful because of their superior tissue-penetrating properties. Beam sources and characteristics will be discussed in the context of current and future BNCT trials. Finally, the past and present

  19. Neutron detection using the superconducting Nb-based current-biased kinetic inductance detector

    NASA Astrophysics Data System (ADS)

    Shishido, Hiroaki; Yamaguchi, Hiroyuki; Miki, Yuya; Miyajima, Shigeyuki; Oikawa, Kenichi; Harada, Masahide; Hidaka, Mutsuo; Oku, Takayuki; Arai, Masatoshi; Fujimaki, Akira; Ishida, Takekazu

    2017-09-01

    We demonstrate neutron detection using a solid-state 3He-free superconducting current-biased kinetic inductance detector (CB-KID), which consists of a superconducting Nb meander line and 10B neutron absorption layer. The CB-KID is based on the transient process of kinetic inductance of Cooper pairs induced by the nuclear reaction between 10B and neutrons. Therefore, the CB-KID can be operated in a wide superconducting region in the bias current-temperature diagram, as demonstrated in this paper. The transient change of the kinetic inductance induces the electromagnetic wave pulse under a DC bias current. The signal propagates along the meander line toward both sides with opposite polarity, where the signal polarity is dominated by the bias current direction. The full width at half maximum of the signals remains on the order of a few tens of ns, which confirms the high-speed operation of our detectors. We determine the neutron incident position within 1.3 mm accuracy in one dimension using the multichannel CB-KIDs.

  20. Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress.

    PubMed

    Schooneveld, E M; Pietropaolo, A; Andreani, C; Perelli Cippo, E; Rhodes, N J; Senesi, R; Tardocchi, M; Gorini, G

    2016-09-01

    Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources.

  1. Radiative neutron capture as a counting technique at pulsed spallation neutron sources: a review of current progress

    NASA Astrophysics Data System (ADS)

    Schooneveld, E. M.; Pietropaolo, A.; Andreani, C.; Perelli Cippo, E.; Rhodes, N. J.; Senesi, R.; Tardocchi, M.; Gorini, G.

    2016-09-01

    Neutron scattering techniques are attracting an increasing interest from scientists in various research fields, ranging from physics and chemistry to biology and archaeometry. The success of these neutron scattering applications is stimulated by the development of higher performance instrumentation. The development of new techniques and concepts, including radiative capture based neutron detection, is therefore a key issue to be addressed. Radiative capture based neutron detectors utilize the emission of prompt gamma rays after neutron absorption in a suitable isotope and the detection of those gammas by a photon counter. They can be used as simple counters in the thermal region and (simultaneously) as energy selector and counters for neutrons in the eV energy region. Several years of extensive development have made eV neutron spectrometers operating in the so-called resonance detector spectrometer (RDS) configuration outperform their conventional counterparts. In fact, the VESUVIO spectrometer, a flagship instrument at ISIS serving a continuous user programme for eV inelastic neutron spectroscopy measurements, is operating in the RDS configuration since 2007. In this review, we discuss the physical mechanism underlying the RDS configuration and the development of associated instrumentation. A few successful neutron scattering experiments that utilize the radiative capture counting techniques will be presented together with the potential of this technique for thermal neutron diffraction measurements. We also outline possible improvements and future perspectives for radiative capture based neutron detectors in neutron scattering application at pulsed neutron sources.

  2. CVD Diamond Detectors for Current Mode Neutron Time-of-Flight Spectroscopy at OMEGA/NIF

    SciTech Connect

    Schmid, G J; Friensehner, A F; Glebov, V Y; Hargrove, D R; Hatchett, S P; Izumi, N; Lerche, R A; Phillips, T W; Sangster, T C; Sibernagel, C; Stoeckl, C

    2001-06-19

    As part of a laser fusion diagnostic development program, we have performed pulsed neutron and pulsed laser tests of a CVD diamond detector manufactured from DIAFILM, a commercial grade of CVD diamond. The laser tests were performed at the short pulse UV laser at Bechtel Nevada in Livermore, CA. The pulsed neutrons were provided by DT capsule implosions at the OMEGA laser fusion facility in Rochester, NY. From these tests, we have determined the impulse response to be 250 ps fwhm for an applied E-field of 500 V/mm. Additionally, we have determined the sensitivity to be 2.8 mA/W at 500 V/mm and 4.5 mA/W at 1000 V/mm (2 to 6x times higher than reported values for natural Type IIa diamond). These detector characteristics allow us to conceive of a neutron time-of-flight current mode spectrometer based on CVD diamond. Such an instrument would sit inside the laser fusion target chamber close to TCC, and would record neutron spectra fast enough such that backscattered neutrons and y rays from the target chamber wall would not be a concern. However, the data we have taken show that the Electromagnetic Pulse (EMP) noise could be a limiting factor in performance. Determining the degree to which this noise can be shielded will be an important subject of future tests.

  3. A review on bioadhesive buccal drug delivery systems: current status of formulation and evaluation methods

    PubMed Central

    Chinna Reddy, P; Chaitanya, K.S.C.; Madhusudan Rao, Y.

    2011-01-01

    Owing to the ease of the administration, the oral cavity is an attractive site for the delivery of drugs. Through this route it is possible to realize mucosal (local effect) and transmucosal (systemic effect) drug administration. In the first case, the aim is to achieve a site-specific release of the drug on the mucosa, whereas the second case involves drug absorption through the mucosal barrier to reach the systemic circulation. The main obstacles that drugs meet when administered via the buccal route derive from the limited absorption area and the barrier properties of the mucosa. The effective physiological removal mechanisms of the oral cavity that take the formulation away from the absorption site are the other obstacles that have to be considered. The strategies studied to overcome such obstacles include the employment of new materials that, possibly, combine mucoadhesive, enzyme inhibitory and penetration enhancer properties and the design of innovative drug delivery systems which, besides improving patient compliance, favor a more intimate contact of the drug with the absorption mucosa. This presents a brief description of advantages and limitations of buccal drug delivery and the anatomical structure of oral mucosa, mechanisms of drug permeation followed by current formulation design in line with developments in buccal delivery systems and methodology in evaluating buccal formulations. PMID:23008684

  4. New method of a "point-like" neutron source creation based on sharp focusing of high-current deuteron beam onto deuterium-saturated target for neutron tomography

    NASA Astrophysics Data System (ADS)

    Golubev, S.; Skalyga, V.; Izotov, I.; Sidorov, A.

    2017-02-01

    A possibility of a compact powerful point-like neutron source creation is discussed. Neutron yield of the source based on deuterium-deuterium (D-D) reaction is estimated at the level of 1011 s-1 (1013 s-1 for deuterium-tritium reaction). The fusion takes place due to bombardment of deuterium- (or tritium) loaded target by high-current focused deuterium ion beam with energy of 100 keV. The ion beam is formed by means of high-current quasi-gasdynamic ion source of a new generation based on an electron cyclotron resonance (ECR) discharge in an open magnetic trap sustained by powerful microwave radiation. The prospects of proposed generator for neutron tomography are discussed. Suggested method is compared to the point-like neutron sources based on a spark produced by powerful femtosecond laser pulses.

  5. Current algebra formulation of M-theory based on E11 Kac-Moody algebra

    NASA Astrophysics Data System (ADS)

    Sugawara, Hirotaka

    2017-02-01

    Quantum M-theory is formulated using the current algebra technique. The current algebra is based on a Kac-Moody algebra rather than usual finite dimensional Lie algebra. Specifically, I study the E11 Kac-Moody algebra that was shown recently1-5 to contain all the ingredients of M-theory. Both the internal symmetry and the external Lorentz symmetry can be realized inside E11, so that, by constructing the current algebra of E11, I obtain both internal gauge theory and gravity theory. The energy-momentum tensor is constructed as the bilinear form of the currents, yielding a system of quantum equations of motion of the currents/fields. Supersymmetry is incorporated in a natural way. The so-called “field-current identity” is built in and, for example, the gravitino field is itself a conserved supercurrent. One unanticipated outcome is that the quantum gravity equation is not identical to the one obtained from the Einstein-Hilbert action.

  6. Boron concentration measurements by alpha spectrometry and quantitative neutron autoradiography in cells and tissues treated with different boronated formulations and administration protocols.

    PubMed

    Bortolussi, Silva; Ciani, Laura; Postuma, Ian; Protti, Nicoletta; Luca Reversi; Bruschi, Piero; Ferrari, Cinzia; Cansolino, Laura; Panza, Luigi; Ristori, Sandra; Altieri, Saverio

    2014-06-01

    The possibility to measure boron concentration with high precision in tissues that will be irradiated represents a fundamental step for a safe and effective BNCT treatment. In Pavia, two techniques have been used for this purpose, a quantitative method based on charged particles spectrometry and a boron biodistribution imaging based on neutron autoradiography. A quantitative method to determine boron concentration by neutron autoradiography has been recently set-up and calibrated for the measurement of biological samples, both solid and liquid, in the frame of the feasibility study of BNCT. This technique was calibrated and the obtained results were cross checked with those of α spectrometry, in order to validate them. The comparisons were performed using tissues taken form animals treated with different boron administration protocols. Subsequently the quantitative neutron autoradiography was employed to measure osteosarcoma cell samples treated with BPA and with new boronated formulations. © 2013 Published by Elsevier Ltd.

  7. An eddy current vector potential formulation for estimating hysteresis losses of superconductors with FEM

    NASA Astrophysics Data System (ADS)

    Stenvall, A.; Tarhasaari, T.

    2010-12-01

    Many people these days employ only commercial finite element method (FEM) software when solving for the hysteresis losses of superconductors. Thus, the knowledge of a modeller is in the capability of using the black boxes of software efficiently. This has led to a relatively superficial examination of different formulations while the discussion stays mainly on the usage of the user interfaces of these programs. Also, if we stay only at the mercy of commercial software producers, we end up having less and less knowledge on the details of solvers. Then, it becomes more and more difficult to conceptually solve new kinds of problem. This may prevent us finding new kinds of method to solve old problems more efficiently, or finding a solution for a problem that was considered almost impossible earlier. In our earlier research, we presented the background of a co-tree gauged T-phiv FEM solver for computing the hysteresis losses of superconductors. In this paper, we examine the feasibility of FEM and eddy current vector potential formulation in the same problem.

  8. Determination of fluoxetine enantiomers in pharmaceutical formulations by electrokinetic chromatography-counter current technique.

    PubMed

    Asensi-Bernardi, Lucía; Martín-Biosca, Yolanda; Fornet-Herrero, Eder; Sagrado, Salvador; Medina-Hernández, María José

    2013-03-01

    In this work, an electrokinetic chromatography-counter current procedure for the separation of fluoxetine enantiomers using highly sulfated β-cyclodextrin was optimized and applied to the determination of the enantiomers in three pharmaceutical formulations according to the matrix features. Quality criteria were applied to facilitate its transferability to testing laboratories. Fluoxetine was used therapeutically as the racemate, although a stereospecificity associated with its interactions with the neuronal serotonin-uptake carrier was demonstrated. In this context, the development of enantioselective methods for the chiral analysis of pharmaceuticals allowing stereoisomer ratio estimations has increasing interest in pharmaceutical industry. The proposed method allows the quantification of both enantiomers in less than 2 min with high resolution (R(s) = 2.4).

  9. Neutron production in deuterium gas-puff z-pinch with outer plasma shell at current of 3 MA

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Z-pinch experiments at the current of about 3 MA were carried out on the GIT-12 generator. The outer plasma shell of deuterium gas-puff was generated by the system of 48 plasma guns. This configuration exhibits a high efficiency of the production of DD fusion neutrons with the yield of above 1012 neutrons produced in a single shot with the duration of about 20 ns. The maximum energy of the neutrons produced in this pulse exceeded 30 MeV. The neutron radiation was measured using scintillation TOF detectors, CR-39 nuclear track detectors, bubble detectors BD-PND and BDS-10000 and by several types of nuclear activation detectors. These diagnostic tools were used to measure the anisotropy of neutron fluence and neutron energy spectra. It allows us to estimate the total number of DD neutrons, the contribution of other nuclear reactions, the amount of scattered neutrons, and other parameters of neutron production. This work was supported by the MSMT grants LH13283, LD14089.

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

    SciTech Connect

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

    2015-01-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  12. Anticancer activities of Withania somnifera: Current research, formulations, and future perspectives.

    PubMed

    Rai, Mahendra; Jogee, Priti S; Agarkar, Gauravi; dos Santos, Carolina Alves

    2016-01-01

    Cancer, being a cause of death for major fraction of population worldwide, is one of the most studied diseases and is being investigated for the development of new technologies and more accurate therapies. Still the currently available therapies for cancer have many lacunae which affect the patient's health severely in the form of side effects. The natural drugs obtained from the medicinal plants provide a better alternative to fight against this devastating disease. Withania somnifera L. Dunal (Solanaceae), a well-known Ayurvedic medicinal plant, has been traditionally used to cure various ailments for centuries. Considering the immense potential of W. somnifera, this review provides a detail account of its vital phytoconstituents and summarizes the present status of the research carried out on its anticancerous activities, giving future directions. The sources of scientific literature were accessed from various electronic databases such as PubMed, Google Scholar, Science Direct, and library search. Various parts of W. somnifera especially the roots with its unique contents have been proved effective against different kinds of cancers. The most active components withanolides and withaferins along with a few other metabolites including withanone (WN) and withanosides have been reported effective against different types of cancer cell lines. This herb holds an important place among various anticancer medicinal plants. It is very essential to further screen and to investigate different formulations for anticancer therapy in vitro as well as in vivo in combination with established chemotherapy.

  13. History and current perspectives on the use of drug formulations to decrease the abuse of prescription drugs.

    PubMed

    Schuster, Charles R

    2006-06-01

    This article is part of a supplemental issue of the journal devoted entirely to papers on how abuse liability of medications is affected by their formulation for medical use. This article reviews the history of abuse and addiction to medications in the United States and the legislation designed to control these problems. The provisions in legislation related specifically to formulations of medications designed to decrease their abuse potential will be noted. In addition, the role of the College on Problems of Drug Dependence (CPDD) as an organization initially founded to develop analgesic medications with less abuse potential than morphine is briefly reviewed. Examples of current approaches to the development of formulations of medications to decrease their abuse potential discussed in detail in the articles to follow are outlined. Finally, the use of behavioral economic analyses to better delineate the relative abuse potential of new medication formulations is discussed.

  14. Continuous p-n junction with extremely low leakage current for micro-structured solid-state neutron detector applications

    NASA Astrophysics Data System (ADS)

    Huang, Kuan-Chih; Dahal, Rajendra; Lu, James J.-Q.; Danon, Yaron; Bhat, Ishwara B.

    2013-05-01

    Considerable progress has been achieved recently to enhance the thermal neutron detection efficiency of solid-state neutron detectors that incorporate neutron sensitive materials such as 10B and 6LiF in Si micro-structured p-n junction diode. Here, we describe the design, fabrication process optimization and characterization of an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction. Boron deposition and diffusion processes were carried out using a low pressure chemical vapor deposition to study the effect of diffusion temperature on current density-voltage characteristics of p+-n diodes. TSUPREM-4 was used to simulate the thickness and surface doping concentration of p+-Si layers. MEDICI was used to simulate the depletion width and the capacitance of the microstructured devices with continuous p+-n junction. Finally, current density-voltage and pulse height distribution of fabricated devices with 2.5×2.5 mm2 size were studied. A very low leakage current density of ~2×10-8 A/cm2 at -1 V (for both planar and honeycomb structured devices) and a bias-independent thermal neutron detection efficiency of ~26% under zero bias voltage were achieved for an enriched boron filled honeycomb structured neutron detector with a continuous p+-n junction.

  15. MEANDER-LINE CURRENT STRUCTURE DEVELOPMENT FOR SPALLATION NEUTRON SOURCE FAST CHOPPER

    SciTech Connect

    S. KURRENOY; J. POWER

    2000-10-01

    A new current structure for the fast traveling-wave 2.5-MeV beam chopper in the front end of the Spallation Neutron Source (SNS) has been suggested in [1]. The structure is based on the meander-folded notched stripline with dielectric supports and separators. Its design has been optimized using electromagnetic 3-D modeling with the MAFIA code package to provide rise and fall times in the range of 1 to 2 ns. A full-length (50 cm) prototype has been manufactured, and its preliminary measurements showed a good agreement with the calculations. Detailed measurements results and their comparison with simulations are presented. The latest front-end design requires a shorter, 35-cm chopper with a higher pulse voltage. Its meander-line current structure, based on the same principles, has also been optimized with MAFIA.

  16. Bootstrap current in enhanced reversed shear tokamaks for volume neutron source applications

    SciTech Connect

    Houlberg, W.A.

    1995-12-31

    The bootstrap current is evaluated for two reference tokamak designs for a Volume Neutron Source (VNS). One is a larger aspect ratio design using superconducting coils (VNS-SC) and the other is a small aspect ratio design using a solid core with normal conducting toroidal field coils (VNS-ST). The target plasma profiles are taken as representative of the recently observed enhanced reverse shear plasmas with hollow magnetic safety factor (q) profiles in the core and corresponding peaked density profiles. The higher q in the plasma center in combination with peaked density is shown to move the peak in the bootstrap current toward the plasma center. This reduces the current drive requirements to a very small axial seed current and a source localized around the location of the desired minimum in the q profile. Very high bootstrap current fractions can be attained in the VNS-SC design with normalized betas (defined in terms of the vacuum toroidal magnetic field at the geometric center of the plasma) of {beta}{sub N} {le} 3.5. The bootstrap current is lower in the VNS-ST design because of its lower aspect ratio; the highest bootstrap fraction found in these limited cases is 50% at {beta}{sub N} = 5.

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

    NASA Astrophysics Data System (ADS)

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

    2017-05-01

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

  18. Current Status of the Experiment on Direct Measurement of Neutron-Neutron Scattering Length at the Reactor YAGUAR

    SciTech Connect

    Furman, W. I.; Muzichka, A. Yu.; Lychagin, E. V.; Nekhaev, G. V.; Sharapov, E. I.; Shvetsov, V. N.; Strelkov, A. V.; Crawford, B. E.; Stephenson, S. L.; Howell, C. R.; Tornow, W.; Kandiev, Ya.; Levakov, B. G.; Litvin, V. I.; Lyzhin, A. E.; Tchernukhin, Yu. I.; Mitchell, G. E.

    2009-03-31

    A new experiment was proposed in 2002 to perform the first direct measurement of neutron-neutron scattering on the powerful pulsed reactor YAGUAR located at Snezhinsk, Ural region, Russia. Extensive efforts were made to model the background conditions and to optimize the set-up design. To make the experiment feasible it was necessary to suppress the background from various origins by more than 16 orders of magnitude for thermal neutrons and 14 orders of magnitude for fast neutrons. In 2003 a channel was drilled under the reactor and equipped for time-of-flight measurements. During the next two years at this channel there were carried out a series of test experiments aimed at verifying the accuracy of the background modeling. Good agreement of the measured results with the calculated values enabled us to make the final design of the full scale set-up. During 2005-2006 the experimental system was manufactured. After vacuum tests at JINR the set-up was mounted at the YAGUAR reactor hall. In 2006-2007 calibration measurements with noble gases were performed. The results confirmed the validity of the modeling of the full scale experiment and verified the calibration. The first preliminary experiments for nn-scattering were performed in April 2008. These recent results are discussed.

  19. Assessing the performance of formulations for nonlinear feedback of surface gravity waves on ocean currents over coastal waters

    NASA Astrophysics Data System (ADS)

    Wang, Pengcheng; Sheng, Jinyu; Hannah, Charles

    2017-08-01

    This study presents applications of a two-way coupled wave-circulation modelling system over coastal waters, with a special emphasis of performance assessments of two different methods for nonlinear feedback of ocean surface gravity waves on three-dimensional (3D) ocean currents. These two methods are the vortex force (VF) formulation suggested by Bennis et al. (2011) and the latest version of radiation stress (RS) formulation suggested by Mellor (2015). The coupled modelling system is first applied to two idealized test cases of surf-zone scales to validate implementations of these two methods in the coupled wave-circulation system. Model results show that the latest version of RS has difficulties in producing the undertow over the surf zone. The coupled system is then applied to Lunenburg Bay (LB) of Nova Scotia during Hurricane Juan in 2003. The coupled system using both the VF and RS formulations generates much stronger and more realistic 3D circulation in the Bay during Hurricane Juan than the circulation-only model, demonstrating the importance of surface wave forces to the 3D ocean circulation over coastal waters. However, the RS formulation generates some weak unphysical currents outside the wave breaking zone due to a less reasonable representation for the vertical distribution of the RS gradients over a slopping bottom. These weak unphysical currents are significantly magnified in a two-way coupled system when interacting with large surface waves, degrading the model performance in simulating currents at one observation site. Our results demonstrate that the VF formulation with an appropriate parameterization of wave breaking effects is able to produce reasonable results for applications over coastal waters during extreme weather events. The RS formulation requires a complex wave theory rather than the linear wave theory for the approximation of a vertical RS term to improve its performance under both breaking and non-breaking wave conditions.

  20. Current Aspects of Formulation Efforts and Pore Lifetime Related to Microneedle Treatment of Skin

    PubMed Central

    Milewski, Mikolaj; Brogden, Nicole K.; Stinchcomb, Audra L.

    2010-01-01

    Importance of this field The efficacy of microneedles in the area of transdermal drug delivery is well-documented. Multiple studies have shown that enhancement of skin permeation via creation of microscopic pores in the stratum corneum can greatly improve the delivery rates of drugs. However, skin pretreatment with microneedles is not the only factor affecting drug transport rates. Other factors including drug formulation and rate of micropore closure are also important for optimizing delivery via this route. Areas covered in this review This review aims at highlighting work that has been done in these areas, with an emphasis on drug formulation parameters that affect transdermal flux. What the reader will gain This review creates an appreciation for the many factors affecting microneedle-enhanced delivery. Most results clearly indicate that microneedle skin pretreatment by itself may have different effects on drug transport depending on the formulation used, and formulation characteristics have different effects on the transport through untreated skin and microneedle-treated skin. Several formulation approaches are reported to optimize microneedle-enhanced drug delivery, including cosolvent use, vesicular, nanoparticulate and gel systems. Take home message In addition to well-established factors that affect microneedle-assisted delivery (geometry, type of microneedles, etc), formulation and pore viability are also critical factors that must be considered. PMID:20205604

  1. Distribution of transport current in a type-II superconductor studied by small-angle neutron scattering.

    PubMed

    Pautrat, A; Goupil, C; Simon, Ch; Charalambous, D; Forgan, E M; Lazard, G; Mathieu, P; Brûlet, A

    2003-02-28

    We report small-angle neutron scattering measurements on the vortex lattice in a PbIn polycrystal in the presence of an applied current. Using the rocking curves as a probe of the distribution of current in the sample, we observe that vortex pinning is due to the surface roughness. This leads to a surface current that persists in the flux-flow region. We show the influence of surface treatments on the distribution of this current.

  2. Thermally stimulated current studies on neutron irradiation induced defects in GaN

    NASA Astrophysics Data System (ADS)

    Kuriyama, K.; Ooi, M.; Onoue, A.; Kushida, K.; Okada, M.; Xu, Q.

    2006-03-01

    The evaluation of the neutron irradiation induced defects in GaN is studied using a thermally stimulated current (TSC) method with excitation above (below) the energy band gap using ultraviolet (blue, green, red, and infrared) emitting diodes. Annealing at 1000°C, a broad TSC spectrum for excitation by the ultraviolet light is resolved by five traps, P1 (ionization energy is 200meV), P2 (270meV), P3 (380meV), P4 (490meV), and P5 (595meV). Infrared illumination shows a remarkable reduction in TSC for the P2 and P3 traps, indicating the photoquenching behavior. The possible origins of the observed five traps are discussed.

  3. Effects of cosmetic formulations containing hydroxyacids on sun-exposed skin: current applications and future developments.

    PubMed

    Kornhauser, Andrija; Coelho, Sergio G; Hearing, Vincent J

    2012-01-01

    This paper describes recent data on the effects of various skin formulations containing hydroxyacids (HAs) and related products on sun-exposed skin. The most frequently used classes of these products, such as α- and β-hydroxyacids, polyhydroxy acids, and bionic acids, are reviewed, and their application in cosmetic formulations is described. Special emphasis is devoted to the safety evaluation of these formulations, particularly on the effects of their prolonged use on sun-exposed skin. We also discuss the important contribution of cosmetic vehicles in these types of studies. Data on the effects of HAs on melanogenesis and tanning are also included. Up-to-date methods and techniques used in those explorations, as well as selected future developments in the cosmetic area, are presented.

  4. Effects of Cosmetic Formulations Containing Hydroxyacids on Sun-Exposed Skin: Current Applications and Future Developments

    PubMed Central

    Kornhauser, Andrija; Coelho, Sergio G.; Hearing, Vincent J.

    2012-01-01

    This paper describes recent data on the effects of various skin formulations containing hydroxyacids (HAs) and related products on sun-exposed skin. The most frequently used classes of these products, such as α- and β-hydroxyacids, polyhydroxy acids, and bionic acids, are reviewed, and their application in cosmetic formulations is described. Special emphasis is devoted to the safety evaluation of these formulations, particularly on the effects of their prolonged use on sun-exposed skin. We also discuss the important contribution of cosmetic vehicles in these types of studies. Data on the effects of HAs on melanogenesis and tanning are also included. Up-to-date methods and techniques used in those explorations, as well as selected future developments in the cosmetic area, are presented. PMID:22675344

  5. Simple Field Assays to Check Quality of Current Artemisinin-Based Antimalarial Combination Formulations

    PubMed Central

    Ioset, Jean-Robert; Kaur, Harparkash

    2009-01-01

    Introduction Malaria continues to be one of the major public health problems in Africa, Asia and Latin America. Artemisinin derivatives (ARTs; artesunate, artemether, and dihydroartemisinin) derived from the herb, Artemisia annua, are the most effective antimalarial drugs available providing rapid cures. The World Health Organisation (WHO) has recommended that all antimalarials must be combined with an artemisinin component (artemisinin-based combination therapy; ACT) for use as first line treatment against malaria. This class of drugs is now first-line policy in most malaria-endemic countries. Reports of ad hoc surveys from South East Asia show that up to 50% of the artesunate currently sold is counterfeit. Drug quality is rarely assessed in resource poor countries in part due to lack of dedicated laboratory facilities which are expensive to build, equip and maintain. With a view to address this unmet need we developed two novel colour reaction assays that can be used in the field to check the quality of ARTs. Methods and Findings Our assays utilise thin layer chromatography silica gel sheets and 2, 4 dinitrophenylhydrazine or 4-Benzoylamino-2, 5-dimethoxybenzenediazonium chloride hemi (zinc chloride) salt as the reagents showing a pink or blue product respectively only in the presence ARTs. We are able to detect as low as 10% of ARTs in ACTs (WINTHROP - artesunate/amodiaquine, Coartem®-artemether/lumefantrine and Duocortexcin - dihydroartemisinin/piperaquine). The assays have been validated extensively by testing eighty readily accessible and widely used drugs in malaria endemic countries. None of the other antimalarial drugs or a range of commonly used excipients, antiretroviral drugs or other frequently used drugs from the WHO essential drugs list such as analgesics or antibiotics are detected with our assays. Conclusions Our two independent assays requiring no specialist training are specific, simple to use, rapid, robust, reproducible, inexpensive and, have

  6. Investigation of Gate Current in Neutron Irradiated Al(x)Ga(1-x)N/GaN Heterogeneous Field Effect Transistors Using Voltage and Temperature Dependence

    DTIC Science & Technology

    2007-03-01

    responsible for the increase in gate current after neutron irradiation. Gallium Nitride Device Physics The device under study is an HFET based... Gallium Nitride, Current-Voltage, Temperature-dependent Current-Voltage, HFET, AlGaN, GaN, AlGaN/GaN, I-V, I-V-T, neutron , radiation, trap-assisted...

  7. Current perspectives on stability of protein drug products during formulation, fill and finish operations.

    PubMed

    Rathore, Nitin; Rajan, Rahul S

    2008-01-01

    Commercialization of protein-based therapeutics is a challenging task in part due to the difficulties in maintaining protein solutions safe and efficacious throughout the drug product development process, storage, transportation and patient administration. Bulk drug substance goes through a series of formulation, fill and finish operations to provide the final dosage form in the desired formulation and container or delivery device. Different process parameters during each of these operations can affect the purity, activity and efficacy of the final product. Common protein degradation pathways and the various physical and chemical factors that can induce such reactions have been extensively studied for years. This review presents an overview of the various formulation-fill-finish operations with a focus on processing steps and conditions that can impact product quality. Various manufacturing operations including bulk freeze-thaw, formulation, filtration, filling, lyophilization, inspection, labeling, packaging, storage, transport and delivery have been reviewed. The article highlights our present day understanding of protein instability issues during biopharmaceutical manufacturing and provides guidance on process considerations that can help alleviate these concerns.

  8. Formulation and experimental evaluation of closed-form control laws for the rapid maneuvering of reactor neutronic power

    SciTech Connect

    Bernard, J.A. . Nuclear Reactor Lab.)

    1989-09-01

    This report describes both the theoretical development and the experimental evaluation of a novel, robust methodology for the time-optimal adjustment of a reactor's neutronic power under conditions of closed-loop digital control. Central to the approach are the MIT-SNL Period-Generated Minimum Time Control Laws' which determine the rate at which reactivity should be changed in order to cause a reactor's neutronic power to conform to a specified trajectory. Using these laws, reactor power can be safely raised by five to seven orders of magnitude in a few seconds. The MIT-SNL laws were developed to facilitate rapid increases of neutronic power on spacecraft reactors operating in an SDI environment. However, these laws are generic and have other applications including the rapid recovery of research and test reactors subsequent to an unanticipated shutdown, power increases following the achievement of criticality on commercial reactors, power adjustments on commercial reactors so as to minimize thermal stress, and automated startups. The work reported here was performed by the Massachusetts Institute of Technology under contract to the Sandia National Laboratories. Support was also provided by the US Department of Energy's Division of University and Industry Programs. The work described in this report is significant in that a novel solution to the problem of time-optimal control of neutronic power was identified, in that a rigorous description of a reactor's dynamics was derived in that the rate of change of reactivity was recognized as the proper control signal, and in that extensive experimental trials were conducted of these newly developed concepts on actual nuclear reactors. 43 refs., 118 figs., 11 tabs.

  9. The complexity of medicinal plants: the traditional Artemisia annua formulation, current status and future perspectives.

    PubMed

    van der Kooy, Frank; Sullivan, Shaun Edward

    2013-10-28

    Artemisia annua has a long tradition of use for the treatment of intermittent fevers which we now relate to malarial infections. The active principle artemisinin has been isolated from Artemisia annua and today forms the backbone of the global fight against malaria. The traditionally prepared Artemisia annua formulation is however still being used on a global scale for the treatment of malaria, and it is claimed that its action is superior to the single purified drug. Artemisia annua is therefore on the forefront of the heated debate between the single drug-single target approach of western based medicine and the holistic approach of traditional medicinal systems. This review aims to highlight the complexities we face in the general study of medicinal plants at the hand of three levels of complexity. These levels consist of (a) the chemistry of the medicinal plant, (b) the influence of the preparation method on the chemistry of the final formulation and (c) the influence of metabolism on the chemistry of the formulation. We also aim to provide an up-to-date report on all scientific work that has been conducted and published in English on the traditional formulation of Artemisia annua. All English scientific literatures published until the first quarter of 2013 were retrieved from well-known scientific databases (Scifinder scholar, Web of Science, PubMed, Google scholar) and Non-governmental organisations active in this field were consulted. A draft version of this manuscript was sent to the African office of the World Health Organisation (WHO), and to the Non-governmental organisations "Action Médicine Naturelle" (ANAMED) and "Iwerliewen fir bedreete Volleker - Réseau belgo-luxembourgeois pour la valorisation des herbes médicinales" (IFBV-BELHERB) for comments. Very little scientific work has been conducted on the Artemisia annua formulation. The available literature contains many discrepancies which are unfortunately selectively being used by the two different

  10. Space experiment BTN-NEUTRON on INTERNATIONAL SPACE STATION - CURRENT STATUS and future stages

    NASA Astrophysics Data System (ADS)

    Tretyakov, V. I.; Kozyrev, A. S.; Laygushin, V. I.; Litvak, M. L.; Malakhov, A. V.; Mitrofanov, I. G.; Mokrousov, M. I.; Pronin, M. A.; Vostrukhin, A. A.; Sanin, A. B.

    2009-04-01

    Space experiment BTN (Board Telescope of Neutrons) was suggested in 1997 for the Russian segment of International Space Station. The first stage of this experiment was started in February 2007 with instrumentation BTN-M1, which contain two separate units: 1) the electronics unit for commanding and data handling, which is installed inside the Station; 2) the detector unit, which is installed at the outer surface of Russian Service Module "Zvezda". The total mass of this instrument without cables is about 15 kg and total power consumption is about 18 Watts. Detector unit of BTN-M1 has the set of four neutron detectors: three proportional counters of epithermal neutrons with 3He covered by cadmium shields and polyethylene moderators with different thickness and stylbene scintillator for fast neutrons at the energy range 0.4 Mev - 10 Mev. There are three sources of neutrons in the near-Earth space. Permanent flux of neutrons is produced due to interaction of energetic particles of galactic and solar cosmic rays with the upper atmosphere of the Earth ("natural neutrons") and with the body of the spacecraft ("technogenic neutrons"). The third transient sources of neutrons are active regions of the Sun, which may sporadically emit energetic neutrons during strong flares. Some of these particles have sufficiently high energy to neutrons cover the distance to the Earth before decay Data from BTN-M1 after 2 years of space operations is sufficient for preliminary estimation of neutron component of radiation environment in the near-Earth space. BTN-M1 detector unit is equal to the Russian instrument HEND, which also operates now onboard NASA's Mars Odyssey orbiter since May 2001. Simultaneous measurements of neutron radiation on orbits around Mars and Earth give the unique opportunity to compare neutron radiation environment around two planets. The technogenic component of neutron background may be estimated by analysis of data for different stages of flight. After evaluation

  11. Self-powered micro-structured solid state neutron detector with very low leakage current and high efficiency

    SciTech Connect

    Dahal, R.; Huang, K. C.; LiCausi, N.; Lu, J.-Q.; Bhat, I.; Clinton, J.; Danon, Y.

    2012-06-11

    We report on the design, fabrication, and performance of solid-state neutron detector based on three-dimensional honeycomb-like silicon micro-structures. The fabricated detectors use boron filled deep holes with aspect ratio of over 12 and showed a very low leakage current density of {approx}7 Multiplication-Sign 10{sup -7} A/cm{sup 2} at -1 V for device sizes varying from 2 Multiplication-Sign 2 to 5 Multiplication-Sign 5 mm{sup 2}. A thermal neutron detection efficiency of 4.5% {+-} 0.5% with discrimination setting of 500 keV and gamma to neutron sensitivity of (1.1 {+-} 0.1) Multiplication-Sign 10{sup -5} for single layer was measured without external bias for these devices. Monte-Carlo simulation predicts a maximum efficiency of 45% for such devices filled with 95% enriched {sup 10}boron.

  12. MCP PMT with high time response and linear output current for neutron time-of-flight detectors

    NASA Astrophysics Data System (ADS)

    Dolotov, A. S.; Konovalov, P. I.; Nurtdinov, R. I.

    2016-09-01

    A microchannel plate (MCP) photomultiplier tube (PMT) with a subnanosecond time response and a high linear output current has been developed. PMT is designed for detection of weak pulses of radiation in UV-, visible and nearer-IR ranges and can be used in neutron time-of-flight (nTOF) detectors in experiments on laser compression of thermonuclear fuel. The results of measurements of MCP PMT main parameters are presented: photocathode spectral sensitivity, gain, maximum linear output current, and time response.

  13. The "Biogenetic Law" in zoology: from Ernst Haeckel's formulation to current approaches.

    PubMed

    Olsson, Lennart; Levit, Georgy S; Hoßfeld, Uwe

    2017-06-01

    150 years ago, in 1866, Ernst Haeckel published a book in two volumes called "Generelle Morphologie der Organismen" (General Morphology of Organisms) in which he formulated his biogenetic law, famously stating that ontogeny recapitulates phylogeny. Here we describe Haeckel's original idea and follow its development in the thinking of two scientists inspired by Haeckel, Alexei Sewertzoff and Adolf Naef. Sewertzoff and Naef initially approached the problem of reformulating Haeckel's law in similar ways, and formulated comparable hypotheses at a purely descriptive level. But their theoretical viewpoints were crucially different. While Sewertzoff laid the foundations for a Darwinian evolutionary morphology and is regarded as a forerunner of the Modern Synthesis, Naef was one of the most important figures in 'idealistic morphology', usually seen as a type of anti-Darwinism. Both Naef and Sewertzoff aimed to revise Haeckel's biogenetic law and came to comparable conclusions at the empirical level. We end our review with a brief look at the present situation in which molecular data are used to test the "hour-glass model", which can be seen as a modern version of the biogenetic law.

  14. Investigation of chemical impurities in formulations, phytotherapics and polyvitaminic medicines by k0-instrumental neutron activation analysis

    NASA Astrophysics Data System (ADS)

    Leal, A. S.; Menezes, M. Â. B. C.; Vermaercke, P.; Sneyers, L.; Jensen, C. E. M.

    2006-08-01

    In this work, comparative k0-Instrumental Neutron-Activation Analysis was performed by CDTN/CNEN/Brazil and SCK.CEN/Belgium in order to investigate the elemental concentration in samples of the same industrialised and manipulated medicine, a phytotherapic and a polyvitaminic, commonly commercialised in Brazil. The preliminary results from both Institutes are in very good agreement. Any serious contamination with possible risks to human health were found in the medicines compared with the expected values. In the case of polyvitaminic, some impurities, unexpected elements, such as La, Ti and Sm, were found in very low concentration. This first assessment confirmed the effectiveness of the k0-method in analysing such matrices.

  15. Emission of neutron-proton and proton-proton pairs in electron scattering induced by meson-exchange currents

    NASA Astrophysics Data System (ADS)

    Simo, I. Ruiz; Amaro, J. E.; Barbaro, M. B.; De Pace, A.; Caballero, J. A.; Megias, G. D.; Donnelly, T. W.

    2016-11-01

    We use a relativistic model of meson-exchange currents to compute the proton-neutron and proton-proton yields in (e ,e') scattering from 12C in the 2p-2h channel. We compute the response functions and cross section with the relativistic Fermi gas model for a range of kinematics from intermediate- to high-momentum transfers. We find a large contribution of neutron-proton configurations in the initial state, as compared to proton-proton pairs. The different emission probabilities of distinct species of nucleon pairs are produced in our model only by meson-exchange currents, mainly by the Δ isobar current. We also analyze the effect of the exchange contribution and show that the direct-exchange interference strongly affects the determination of the n p /p p ratio.

  16. A review of current and novel levodopa formulations for the treatment of Parkinson's disease.

    PubMed

    Jimenez-Shahed, Joohi

    2016-01-01

    Parkinson's disease treatment is characterized by the nearly inevitable development of motor complications, including fluctuations and dyskinesias, in which the duration of benefit of a dose of medication is offset by involuntary movements that can be more disabling than the Parkinsonian features themselves. While levodopa remains the gold standard of therapy, it is the most likely to be associated with these complications. The concept of continuous dopaminergic stimulation has gained increasing acceptance as a potential mechanism by which to avoid or delay the development of motor complications, or to minimize their impact once they have already occurred. This article will explore existing and novel formulations of levodopa to identify their role in the spectrum of Parkinson's disease therapeutics.

  17. Orbit Correction Methods - Basic Formulation, Current Applications at Jefferson Lab, and Future Possibilities

    SciTech Connect

    Chao, Y.C.

    1999-12-01

    A. Orbit Correction System Optimization: Recipes for optimizing an orbit correction system configuration at the design level are presented. Linear algebraic tools are applied to various flavors of response matrices to uniformly control unobservability, uncorrectability, and response matrix singularity. Application at Jefferson Lab is discussed. B. Orbit Correction at Jefferson Lab: Unique challenges posed by orbit correction, as well as algorithms and tools developed at the CEBAF accelerator at Jefferson Lab are discussed. C. Orbit Interpretation and Virtual Monitors: A new approach to developing an orbit correction package with software structural, algorithmic and operational advantages is introduced. It consists of an orbit interpretation module, a virtual monitor module, and a generic steering engine. Mathematical formulation, algorithms prototyped and tested on simulated and real data, and future possibilities are discussed.

  18. Temperature Dependent Current-Voltage Measurements of Neutron Irradiated A10.27Ga0.73N/GaN Modulation Doped Field Effect Transistors

    DTIC Science & Technology

    2005-03-01

    locations within the reactor), the neutron energy spectrum is reduced to a monoenergetic source with a damage effectiveness equivalent to the entire...58], [59]. The 1 MeV Eq is the fluence required of 1 MeV monoenergetic neutrons to cause the same amount of damage as the entire spectrum for a...Can you TEMPERATURE DEPENDENT CURRENT-VOLTAGE MEASUREMENTS OF NEUTRON IRRADIATED Al0.27Ga0.73N/GaN

  19. The Effect of Driver Rise-Time on Pinch Current and its Impact on Plasma Focus Performance and Neutron Yield

    NASA Astrophysics Data System (ADS)

    Sears, Jason; Schmidt, Andrea; Link, Anthony; Welch, Dale

    2016-10-01

    Experiments have suggested that dense plasma focus (DPF) neutron yield increases with faster drivers [Decker NIMP 1986]. Using the particle-in-cell code LSP [Schmidt PRL 2012], we reproduce this trend in a kJ DPF [Ellsworth 2014], and demonstrate how driver rise time is coupled to neutron output. We implement a 2-D model of the plasma focus including self-consistent circuit-driven boundary conditions. Driver capacitance and voltage are varied to modify the current rise time, and anode length is adjusted so that run-in coincides with the peak current. We observe during run down that magnetohydrodynamic (MHD) instabilities of the sheath shed blobs of plasma that remain in the inter-electrode gap during run in. This trailing plasma later acts as a low-inductance restrike path that shunts current from the pinch during maximum compression. While the MHD growth rate increases slightly with driver speed, the shorter anode of the fast driver allows fewer e-foldings and hence reduces the trailing mass between electrodes. As a result, the fast driver postpones parasitic restrikes and maintains peak current through the pinch during maximum compression. The fast driver pinch therefore achieves best simultaneity between its ion beam and peak target density, which maximizes neutron production. Prepared by LLNL under Contract DE-AC52-07NA27344.

  20. Pixel pitch and particle energy influence on the dark current distribution of neutron irradiated CMOS image sensors.

    PubMed

    Belloir, Jean-Marc; Goiffon, Vincent; Virmontois, Cédric; Raine, Mélanie; Paillet, Philippe; Duhamel, Olivier; Gaillardin, Marc; Molina, Romain; Magnan, Pierre; Gilard, Olivier

    2016-02-22

    The dark current produced by neutron irradiation in CMOS Image Sensors (CIS) is investigated. Several CIS with different photodiode types and pixel pitches are irradiated with various neutron energies and fluences to study the influence of each of these optical detector and irradiation parameters on the dark current distribution. An empirical model is tested on the experimental data and validated on all the irradiated optical imagers. This model is able to describe all the presented dark current distributions with no parameter variation for neutron energies of 14 MeV or higher, regardless of the optical detector and irradiation characteristics. For energies below 1 MeV, it is shown that a single parameter has to be adjusted because of the lower mean damage energy per nuclear interaction. This model and these conclusions can be transposed to any silicon based solid-state optical imagers such as CIS or Charged Coupled Devices (CCD). This work can also be used when designing an optical imager instrument, to anticipate the dark current increase or to choose a mitigation technique.

  1. A half-analytical formulation for the impedance variation in axisymmetrical modelling of eddy current non destructive testing

    NASA Astrophysics Data System (ADS)

    Maouche, B.; Feliachi, M.; Khenfer, N.

    2006-01-01

    We present the calculation of the impedance variation using a half-analytical formulation based on coupled electromagnetic variables. Such a formulation concerns an axisymmetrical device constituted with a voltage supplied solenoïdal inductor and a conducting workpiece. In this field of modelling, authors have already developed a method [Maouche and Feliachi, J. Phys. III France 10, 1967 (1997)] that determines the current distribution inside inductor coil loops in the case of weak skin depth and a low number of these coil loops. In the proposed development, the number of loops is relatively large and the skin effect in these loops is negligible. This formulation uses a voltage excitation, which makes the source field depending on induced currents and permits to consider the real geometry of the inductor. The model is applied to study an eddy current non destructive testing (ECNDT) device. The variation of the system impedance is calculated in the case of an axisymmetrical device. The obtained modelling results are validated by comparison to measurements and finite element computations [Rémy, Ph.D. thesis, University of Compiègne, France, 1997; La et al., Rev. Prog. Quant. Non-Destructive Eval. 16A, 295 (1997)]. Once validated, the proposed model is applied to determine geometrical and physical characteristics of an ECNDT device. To assemble this interest, we visualise the evolution of the impedance variation according respectively to the air-gap, to the thickness of the workpiece and its electric conductivity. The model is implemented within a software tool (CECM: Coupling Electromagnetic Circuits Method) developed in Matlab environment.

  2. Impact of physical properties of formulations on bioavailability of active substance: current and novel drugs with cyclosporine.

    PubMed

    Andrysek, T

    2003-07-01

    During the long period of cyclosporine-containing dosage forms development a lot of significant findings have been done especially in the field of drug delivery systems. Currently available drugs are based, from technological point of view, on self-dispersible drug delivery systems, which contain cyclosporine solved in pharmaceutically acceptable vehicle. One can find difference among particular systems: (a) at particle size distribution after dispergation; (b) at composition; and (c) at bioavailability of cyclosporine. As far as improvement of bioavailability between original brand leader formulation Sandimmune and recent brand leader formulation Neoral was followed by significant improvement in particle size distribution, it was generally assumed that the reason for this improvement have been found. Several other formulations, e.g. Consupren or SangCyA-self-dispersible systems, more or less correspond with above-mentioned theory that smaller is better and by this principle bridged liquid based dosage forms with solid dosage forms. Bioavailability of novel drug delivery system which gives coarse dispersion with average particle size between 1-150 microm when dispersed have been tested on healthy volunteers. No difference among pharmacokinetic parameters of novel drug delivery system and microemulsion system have been observed in spite of fact that average particle size of novel system is almost 1000x bigger.

  3. Reaction Matrix Calculations in Neutron Matter with Alternating-Layer-Spin Structure under π0 Condensation. I ---Formulation---

    NASA Astrophysics Data System (ADS)

    Tamiya, K.; Tamagaki, R.

    1981-09-01

    Based on the viewpoint that a typical π0 condensation is realized with the [ALS] (Alternating-Layer-Spin) structure of nucleon system, a framework to calculate the energy of neutron matter under such a new phase is presented in the reaction matrix theory. This enables us to treat both effects on equal footing; the long-range effect dominated by the OPEP tensor component with the enhancement due to the mixing of Δ(1236MeV) and the sort-range effect much influenced by repulsive core and spin-orbit force. Starting with the [ALS] model wave function constructed on the Bloch basis which assures to take the limit of no localization, we have the expressions for energy quantities expressed by the partial-wave contributions. This scheme provides a way to understand the mechanism of energy gain in the new phase, by making use of the notions of the ordinary unclear matter theory such as the potential picture and the partial waves. Some numerical examples are shown.

  4. A simple formulation for magnetoresistance in metal-insulator granular films with increased current

    NASA Astrophysics Data System (ADS)

    Boff, M. A. S.; Canto, B.; Baibich, M. N.; Pereira, L. G.

    2013-02-01

    We studied the tunnel magnetoresistance in metal/insulator granular films when the applied current is varied. The tunnel magnetoresistance shows a strong modification related to a non-Ohmic behaviour of theses materials. It was verified that spin-dependent tunnelling is the main mechanism for magnetoresistance at low applied current. However, when the current is high, another mechanism gets to be important: it is independent of the magnetization and is associated to variable range hopping between metallic grains. In this work, we propose a simple modification of Inoue and Maekawa's model for tunnelling magnetoresistance in granulars, rewriting the expression for resistance as a function of magnetic field and temperature, also taking into account the two different contributions.

  5. Performance of Current-Mode Ion Chambers as Beam Monitors in a Pulsed Cold Neutron Beam for the NPDGamma experiment

    NASA Astrophysics Data System (ADS)

    Gillis, R. Chad

    2006-10-01

    The NPDGamma collaboration has built and commissioned an apparatus to measure the parity-violating gamma asymmetry A in the low energy np capture process n+p->d+ γ. The asymmetry in question is a 10-8 correlation between the spin of the incident (polarized) neutron and the outgoing 2.2 MeV gamma ray. A set of purpose-built, 3He-filled ionization chambers read out in current mode is used to monitor the incident neutron flux, the beam polarization, and the transmission of the liquid para-hydrogen target during the NPDGamma measurements. As will be described in the talk, these beam monitors are simple, reliable, low-noise detectors that have performed excellently for NPDGamma. We have verified that the beam monitor signals can be interpreted to reproduce the known time-of-flight dependence of beam flux from the LANSCE pulsed cold neutron source, and that the neutron beam polarization can be measured at the 2% level from direct measurements of the transmission of the beam through the beam polarizer.

  6. Scanning transient current study of the I-V stabilization phenomena in silicon detectors irradiated by fast neutrons

    SciTech Connect

    Eremin, V.; Verbitskaya, E.; Li, Z.; Sidorov, A.; Fretwurst, E.; Lindstrom, G.

    1996-03-01

    Investigation of the I-V stabilization phenomena in neutron irradiated silicon detectors has been carried out using scanning transient current technique (STCT) on non-irradiated PP{sup +}-p-n{sup +} detectors. The PP{sup +}-p-n{sup +} detectors were used to simulate the PP{sup +}-n-n{sup +} detectors irradiated beyond the space charge sign inversion (SCSI). Two mechanisms partially responsible for the I- V stabilization have been identified.

  7. Neutron Scattering Studies of the Effects of Formulating Amphotericin B with Cholesteryl Sulfate on the Drug's Interactions with Phospholipid and Phospholipid-Sterol Membranes.

    PubMed

    Foglia, F; Rogers, S E; Webster, J R P; Akeroyd, F A; Gascoyne, K F; Lawrence, M J; Barlow, D J

    2015-07-28

    Langmuir surface pressure, small-angle neutron scattering (SANS), and neutron reflectivity (NR) studies have been performed to determine how formulation of the antifungal drug amphotericin B (AmB), with sodium cholesteryl sulfate (SCS)-as in Amphotec-affects its interactions with ergosterol-containing (model fungal cell) and cholesterol-containing (model mammalian cell) membranes. The effects of mixing AmB in 1:1 molar ratio with cholesteryl sulfate (yielding AmB-SCS micelles) are compared against those of free AmB, using monolayers and bilayers formed from palmitoyloleoylphosphatidylcholine (POPC) in the absence and presence of 30 mol % ergosterol or cholesterol, in all cases employing a 1:0.05 molar ratio of lipid:AmB. Analyses of the (bilayer) SANS and (monolayer) NR data indicate that the equilibrium changes in membrane structure induced in sterol-free and sterol-containing membranes are the same for free AmB and AmB-SCS. Stopped-flow SANS experiments, however, reveal that the structural changes to vesicle membranes occur far more rapidly following exposure to AmB-SCS vs free drug, with the kinetics of these changes varying with membrane composition. With POPC vesicles, the structural changes induced by AmB-SCS become apparent only after several minutes, and equilibrium is reached after ∼30 min. The corresponding onset of changes in POPC-ergosterol and POPC-cholesterol vesicles, however, occurs within ∼5 s, with equilibrium reached after 10 and 120 s, respectively. The rate of insertion of AmB into POPC-sterol membranes is thus increased through formulation as AmB-SCS. Moreover, the differences in monolayer surface pressure and SANS structure-change equilibration times suggest significant rearrangement of AmB within these membranes following insertion. The reduced times to equilibrium for the POPC-ergosterol vs POPC-cholesterol systems are consistent with the known differences in affinity of AmB for these two sterols, and the reduced time to equilibrium for

  8. CaLMa Neutron Monitor: current status, first observations and future improvements

    NASA Astrophysics Data System (ADS)

    Blanco, J. J.; Medina, J.; García-Población, O.; Gómez-Herrero, R.; García-Tejedor, I.; Ayuso, S.; Catalán, E. J.

    2015-08-01

    Castilla-La Mancha Neutron Monitor (CaLMa) is a 15 boron trifluoride counter neutron monitor located in Guadalajara, Spain (40°38'N, 3°9'W) at 708 m above sea level (asl) and a vertical rigidity cut-off of 6.95 GV. CaLMa is able to measure neutrons produced by primary cosmic rays with energies above 6 GeV if protons are these primary cosmic rays. CaLMa has been continuously monitoring solar activity since October 2011, having reported more than 25 Forbush decreases. This work presents the preliminary results inferred from CaLMa's count rate variations, shows the latest improvements carried out in CaLMa and outlines our future plans to improve the station

  9. Scalable large-area solid-state neutron detector with continuous p-n junction and extremely low leakage current

    NASA Astrophysics Data System (ADS)

    Huang, Kuan-Chih; Dahal, Rajendra; Lu, James J.-Q.; Weltz, Adam; Danon, Yaron; Bhat, Ishwara B.

    2014-11-01

    We report on the fabrication and characterization of solid-state thermal neutron detectors with detection areas up to 16 cm2 that require only a single preamplifier for data acquisition. These detectors consist of a honeycomb-like micro-structured Si diode with boron-10 filled deep holes. A continuous p-n junction formed over the entire surface of the microstructure helps to achieve a low leakage current density of ~6.1×10-9 A/cm2 at -1 V for a 2.5×2.5 mm2 detector. This low leakage current results in low electronic noise, which enables the fabrication of large-area detectors. An intrinsic thermal neutron detection efficiency of up to 26% was measured for a 2.5×2.5 mm2 detector module and up to 24% was measured for a 1 cm2 detector module. These measurements were obtained under zero bias voltage using a moderated californium-252 source. The relative efficiency remains almost the same when scaling the detector area up to 8 cm2 by connecting 1 cm2 detector modules in series. However, it decreases to 0.89 and 0.82, respectively, for 12 and 16 cm2. Nevertheless, these results demonstrate the promise of using boron filled micro-structured Si diodes as a cost effective alternative to the helium-3 based neutron detection technology and the potential of fabricating scalable large-area solid-state neutron detectors that are desirable for many applications.

  10. Current status of boron neutron capture therapy of high grade gliomas and recurrent head and neck cancer.

    PubMed

    Barth, Rolf F; Vicente, M Graca H; Harling, Otto K; Kiger, W S; Riley, Kent J; Binns, Peter J; Wagner, Franz M; Suzuki, Minoru; Aihara, Teruhito; Kato, Itsuro; Kawabata, Shinji

    2012-08-29

    Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Clinical interest in BNCT has focused primarily on the treatment of high grade gliomas, recurrent cancers of the head and neck region and either primary or metastatic melanoma. Neutron sources for BNCT currently have been limited to specially modified nuclear reactors, which are or until the recent Japanese natural disaster, were available in Japan, United States, Finland and several other European countries, Argentina and Taiwan. Accelerators producing epithermal neutron beams also could be used for BNCT and these are being developed in several countries. It is anticipated that the first Japanese accelerator will be available for therapeutic use in 2013. The major hurdle for the design and synthesis of boron delivery agents has been the requirement for selective tumor targeting to achieve boron concentrations in the range of 20 μg/g. This would be sufficient to deliver therapeutic doses of radiation with minimal normal tissue toxicity. Two boron drugs have been used clinically, a dihydroxyboryl derivative of phenylalanine, referred to as boronophenylalanine or "BPA", and sodium borocaptate or "BSH" (Na2B12H11SH). In this report we will provide an overview of other boron delivery agents that currently are under evaluation, neutron sources in use or under development for BNCT, clinical dosimetry, treatment planning, and finally a summary of previous and on-going clinical studies for high grade gliomas and recurrent tumors of the head and neck region. Promising results have been obtained with both groups of patients but these outcomes must be more rigorously evaluated in larger, possibly randomized clinical trials

  11. Current status of boron neutron capture therapy of high grade gliomas and recurrent head and neck cancer

    PubMed Central

    2012-01-01

    Boron neutron capture therapy (BNCT) is a biochemically targeted radiotherapy based on the nuclear capture and fission reactions that occur when non-radioactive boron-10, which is a constituent of natural elemental boron, is irradiated with low energy thermal neutrons to yield high linear energy transfer alpha particles and recoiling lithium-7 nuclei. Clinical interest in BNCT has focused primarily on the treatment of high grade gliomas, recurrent cancers of the head and neck region and either primary or metastatic melanoma. Neutron sources for BNCT currently have been limited to specially modified nuclear reactors, which are or until the recent Japanese natural disaster, were available in Japan, the United States, Finland and several other European countries, Argentina and Taiwan. Accelerators producing epithermal neutron beams also could be used for BNCT and these are being developed in several countries. It is anticipated that the first Japanese accelerator will be available for therapeutic use in 2013. The major hurdle for the design and synthesis of boron delivery agents has been the requirement for selective tumor targeting to achieve boron concentrations in the range of 20 μg/g. This would be sufficient to deliver therapeutic doses of radiation with minimal normal tissue toxicity. Two boron drugs have been used clinically, a dihydroxyboryl derivative of phenylalanine, referred to as boronophenylalanine or “BPA”, and sodium borocaptate or “BSH” (Na2B12H11SH). In this report we will provide an overview of other boron delivery agents that currently are under evaluation, neutron sources in use or under development for BNCT, clinical dosimetry, treatment planning, and finally a summary of previous and on-going clinical studies for high grade gliomas and recurrent tumors of the head and neck region. Promising results have been obtained with both groups of patients but these outcomes must be more rigorously evaluated in larger, possibly randomized

  12. Current and anticipated uses of thermalhydraulic and neutronic codes at PSI

    SciTech Connect

    Aksan, S.N.; Zimmermann, M.A.; Yadigaroglu, G.

    1997-07-01

    The thermalhydraulic and/or neutronic codes in use at PSI mainly provide the capability to perform deterministic safety analysis for Swiss NPPs and also serve as analysis tools for experimental facilities for LWR and ALWR simulations. In relation to these applications, physical model development and improvements, and assessment of the codes are also essential components of the activities. In this paper, a brief overview is provided on the thermalhydraulic and/or neutronic codes used for safety analysis of LWRs, at PSI, and also of some experiences and applications with these codes. Based on these experiences, additional assessment needs are indicated, together with some model improvement needs. The future needs that could be used to specify both the development of a new code and also improvement of available codes are summarized.

  13. A novel method for modeling the neutron time of flight detector response in current mode to inertial confinement fusion experiments (invited)

    SciTech Connect

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

    2012-10-15

    A novel method for modeling the neutron time of flight (nTOF) detector response in current mode for inertial confinement fusion experiments has been applied to the on-axis nTOF detectors located in the basement of the Z-Facility. It will be shown that this method can identify sources of neutron scattering, and is useful for predicting detector responses in future experimental configurations, and for identifying potential sources of neutron scattering when experimental set-ups change. This method can also provide insight on how much broadening neutron scattering contributes to the primary signals, which is then subtracted from them. Detector time responses are deconvolved from the signals, allowing a transformation from dN/dt to dN/dE, extracting neutron spectra at each detector location; these spectra are proportional to the absolute yield.

  14. Current and future capabilities of the neutron reflectometer MIRROR at Oak Ridge National Laboratory's High Flux Isotope Reactor

    NASA Astrophysics Data System (ADS)

    Hamilton, W. A.; Smith, G. S.; Taylor, G. B.; Larkins, B. M.; Porcar, L.

    2006-11-01

    The peripatetic ORNL HFIR Center for Neutron Scattering reflectometer instrument MIRROR has recently been re-installed in an interim beam line position in the reactor beam room. In 2006 an upgraded version of the instrument will move to a high intensity guide hall position fed by the new HFIR cold source. In this short note, we present some aspects of current instrument operation-particularly with respect to data reduction from the instrument's linear reflection plane detector-with examples of ongoing research and analysis, and a brief outline of the expected capabilities of the fully upgraded guide hall instrument.

  15. Self-consistent quasiparticle formulation of a multiphonon method and its application to the neutron-rich O20 nucleus

    NASA Astrophysics Data System (ADS)

    De Gregorio, G.; Knapp, F.; Lo Iudice, N.; Vesely, P.

    2016-04-01

    A Bogoliubov quasiparticle formulation of an equation-of-motion phonon method, suited for open-shell nuclei, is derived. Like its particle-hole version, it consists of deriving a set of equations of motions whose iterative solution generates an orthonormal basis of n -phonon states (n =0 ,1 ,2 ,... ), built of quasiparticle Tamm-Dancoff phonons, which simplifies the solution of the eigenvalue problem. The method is applied to the open-shell neutron-rich O20 for illustrative purposes. A Hartree-Fock-Bogoliubov canonical basis, derived from an intrinsic two-body optimized chiral Hamiltonian, is used to derive and solve the eigenvalue equations in a space encompassing a truncated two-phonon basis. The spurious admixtures induced by the violation of the particle number and the center-of-mass motion are eliminated to a large extent by a Gram-Schmidt orthogonalization procedure. The calculation takes into account the Pauli principle, is self-consistent, and is parameter free except for the energy cutoff used to truncate the two-phonon basis, which induces an increasing depression of the ground state through its strong coupling to the quasiparticle vacuum. Such a cutoff is fixed so as to reproduce the first 1- level. The two-phonon states are shown to enhance the level density of the low-energy spectrum, consistently with the data, and to induce a fragmentation of the E 1 strength which, while accounting for the very low E 1 transitions, is not sufficient to reproduce the experimental cross section in the intermediate energy region. This and other discrepancies suggest the need of including the three-phonon states. These are also expected to offset the action of the two phonons on the quasiparticle vacuum and, therefore, free the calculation from any parameter.

  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. Implementation and modification of a three-dimensional radiation stress formulation for surf zone and rip-current applications

    USGS Publications Warehouse

    Kumar, N.; Voulgaris, G.; Warner, J.C.

    2011-01-01

    Regional Ocean Modeling System (ROMS v 3.0), a three-dimensional numerical ocean model, was previously enhanced for shallow water applications by including wave-induced radiation stress forcing provided through coupling to wave propagation models (SWAN, REF/DIF). This enhancement made it suitable for surf zone applications as demonstrated using examples of obliquely incident waves on a planar beach and rip current formation in longshore bar trough morphology (Haas and Warner, 2009). In this contribution, we present an update to the coupled model which implements a wave roller model and also a modified method of the radiation stress term based on Mellor (2008, 2011a,b,in press) that includes a vertical distribution which better simulates non-conservative (i.e., wave breaking) processes and appears to be more appropriate for sigma coordinates in very shallow waters where wave breaking conditions dominate. The improvements of the modified model are shown through simulations of several cases that include: (a) obliquely incident spectral waves on a planar beach; (b) obliquely incident spectral waves on a natural barred beach (DUCK'94 experiment); (c) alongshore variable offshore wave forcing on a planar beach; (d) alongshore varying bathymetry with constant offshore wave forcing; and (e) nearshore barred morphology with rip-channels. Quantitative and qualitative comparisons to previous analytical, numerical, laboratory studies and field measurements show that the modified model replicates surf zone recirculation patterns (onshore drift at the surface and undertow at the bottom) more accurately than previous formulations based on radiation stress (Haas and Warner, 2009). The results of the model and test cases are further explored for identifying the forces operating in rip current development and the potential implication for sediment transport and rip channel development. Also, model analysis showed that rip current strength is higher when waves approach at angles of 5

  18. Neutron radiography

    SciTech Connect

    Berger, H.; Iddings, F.

    1998-08-01

    Neutron radiography is becoming a well established nondestructive testing (NDT) method. The American Society for Nondestructive Testing (ASNT) has recognized the method through its recommended practice SNT-TCIA which outlines training, knowledge, and experience necessary to obtain levels of competency in the method. Certification of nondestructive testing personnel is also covered in a military standard. Technical publications in the field of NDT and nuclear technology carry articles on neutron radiography and technical meetings include papers or even entire sessions on neutron radiography. There is an on-going series of international conferences on neutron radiography. Many books are available to provide introductory and advanced material on neutron radiographic techniques and applications. Neutron radiography as a service for hire is available, similar to that offered for other NDT services. The method is being adopted to solve NDT problems in specialty areas. The objective of this report is to provide a brief survey of the current state of the art in the use of neutron radiography. The survey will include information on the technique including principles of the method, sources of neutrons, detection methodology, standards and image quality indicators, and representative applications. An extensive reference list provides additional information for those who wish to investigate further and a Glossary is included which provides definitions for terms used in Neutron Radiography.

  19. Neutron measurements

    SciTech Connect

    McCall, R.C.

    1981-01-01

    Methods of neutron detection and measurement are discussed. Topics include sources of neutrons, neutrons in medicine, interactions of neutrons with matter, neutron shielding, neutron measurement units, measurement methods, and neutron spectroscopy. (ACR)

  20. Commissioning of the NPDGamma Detector Array: Counting Statistics in Current Mode Operation and Parity Violation in the Capture of Cold Neutrons on B 4 C and (27) Al.

    PubMed

    Gericke, M T; Bowman, J D; Carlini, R D; Chupp, T E; Coulter, K P; Dabaghyan, M; Desai, D; Freedman, S J; Gentile, T R; Gillis, R C; Greene, G L; Hersman, F W; Ino, T; Ishimoto, S; Jones, G L; Lauss, B; Leuschner, M B; Losowski, B; Mahurin, R; Masuda, Y; Mitchell, G S; Muto, S; Nann, H; Page, S A; Penttila, S I; Ramsay, W D; Santra, S; Seo, P-N; Sharapov, E I; Smith, T B; Snow, W M; Wilburn, W S; Yuan, V; Zhu, H

    2005-01-01

    The NPDGamma γ-ray detector has been built to measure, with high accuracy, the size of the small parity-violating asymmetry in the angular distribution of gamma rays from the capture of polarized cold neutrons by protons. The high cold neutron flux at the Los Alamos Neutron Scattering Center (LANSCE) spallation neutron source and control of systematic errors require the use of current mode detection with vacuum photodiodes and low-noise solid-state preamplifiers. We show that the detector array operates at counting statistics and that the asymmetries due to B4C and (27)Al are zero to with- in 2 × 10(-6) and 7 × 10(-7), respectively. Boron and aluminum are used throughout the experiment. The results presented here are preliminary.

  1. A detailed neutronics comparison of the university of Florida training reactor (UFTR) current HEU and proposed LEU cores

    SciTech Connect

    Dionne, B.; Haghighat, A.; Yi, C.; Smith, R.; Ghita, G.; Manalo, K.; Sjoden, G.; Huh, J.; Baciak, J.; Mock, T.; Wenner, M.; Matos, J.; Stillman, J.

    2006-07-01

    For over 35 years, the UFTR highly-enriched core has been safely operated. As part of the Reduced Enrichment for Research and Test Reactors Program, the core is currently being converted to low-enriched uranium fuel. The analyses presented in this paper were performed to verify that, from a neutronic perspective, a proposed low-enriched core can be operated as safely and as effectively as the highly-enriched core. Detailed Monte Carlo criticality calculations are performed to determine: i) Excess reactivity for different core configurations, ii) Individual integral blade worth and shutdown margin, iii) Reactivity coefficients and kinetic parameters, and iv) Flux profiles and core six-factor formula parameters. (authors)

  2. Current risk estimates based on the A-bomb survivors data - a discussion in terms of the ICRP recommendations on the neutron weighting factor.

    PubMed

    Rühm, W; Walsh, L

    2007-01-01

    Currently, most analyses of the A-bomb survivors' solid tumour and leukaemia data are based on a constant neutron relative biological effectiveness (RBE) value of 10 that is applied to all survivors, independent of their distance to the hypocentre at the time of bombing. The results of these analyses are then used as a major basis for current risk estimates suggested by the International Commission on Radiological Protection (ICRP) for use in international safety guidelines. It is shown here that (i) a constant value of 10 is not consistent with weighting factors recommended by the ICRP for neutrons and (ii) it does not account for the hardening of the neutron spectra in Hiroshima and Nagasaki, which takes place with increasing distance from the hypocentres. The purpose of this paper is to present new RBE values for the neutrons, calculated as a function of distance from the hypocentres for both cities that are consistent with the ICRP60 neutron weighting factor. If based on neutron spectra from the DS86 dosimetry system, these calculations suggest values of about 31 at 1000 m and 23 at 2000 m ground range in Hiroshima, while the corresponding values for Nagasaki are 24 and 22. If the neutron weighting factor that is consistent with ICRP92 is used, the corresponding values are about 23 and 21 for Hiroshima and 21 and 20 for Nagasaki, respectively. It is concluded that the current risk estimates will be subject to some changes in view of the changed RBE values. This conclusion does not change significantly if the new doses from the Dosimetry System DS02 are used.

  3. Glass Property Models and Constraints for Estimating the Glass to be Produced at Hanford by Implementing Current Advanced Glass Formulation Efforts

    SciTech Connect

    Vienna, John D.; Kim, Dong-Sang; Skorski, Daniel C.; Matyas, Josef

    2013-07-01

    Recent glass formulation and melter testing data have suggested that significant increases in waste loading in HLW and LAW glasses are possible over current system planning estimates. The data (although limited in some cases) were evaluated to determine a set of constraints and models that could be used to estimate the maximum loading of specific waste compositions in glass. It is recommended that these models and constraints be used to estimate the likely HLW and LAW glass volumes that would result if the current glass formulation studies are successfully completed. It is recognized that some of the models are preliminary in nature and will change in the coming years. Plus the models do not currently address the prediction uncertainties that would be needed before they could be used in plant operations. The models and constraints are only meant to give an indication of rough glass volumes and are not intended to be used in plant operation or waste form qualification activities. A current research program is in place to develop the data, models, and uncertainty descriptions for that purpose. A fundamental tenet underlying the research reported in this document is to try to be less conservative than previous studies when developing constraints for estimating the glass to be produced by implementing current advanced glass formulation efforts. The less conservative approach documented herein should allow for the estimate of glass masses that may be realized if the current efforts in advanced glass formulations are completed over the coming years and are as successful as early indications suggest they may be. Because of this approach there is an unquantifiable uncertainty in the ultimate glass volume projections due to model prediction uncertainties that has to be considered along with other system uncertainties such as waste compositions and amounts to be immobilized, split factors between LAW and HLW, etc.

  4. Optical absorption and thermally stimulated depolarization current studies of nickel chloride-doped poly(vinyl alcohol) irradiated with low-level fast neutron doses

    SciTech Connect

    Abd El-Kader, F.H.; Ibrahim, S.S. . Physics Dept.); Attia, G. . Faculty of Education)

    1993-11-15

    The influence of neutron irradiation on ultraviolet/visible absorption and thermally stimulated depolarization current in nickel chloride-poly(vinyl alcohol) (PVA) cast films has been investigated. The spectral measurements indicate the responsibility of the Ni[sup 2][sup +] ion in its octahedral symmetry. Dopant concentrations higher than 10 wt % NiCl[sub 2] are found to make the samples more resistant to a degradation effect caused by neutron irradiation. The thermally stimulated depolarization currents (TSDC) of pure PVA revealed the existence of the glass transition T[sub g] and space charge relaxation peaks, whereas doped-PVA samples show a new sub-T[sub g] relaxation peak. A proposed mechanism is introduced to account for the neutron effects on both glass transition and space charge relaxation peaks. The peak positions, peak currents, and stored charges of the sub-T[sub g] relaxation peak are strongly affected by both the concentration of the dopant and neutron exposure doses.

  5. Design of a high-current low-energy beam transport line for an intense D-T/D-D neutron generator

    NASA Astrophysics Data System (ADS)

    Lu, Xiaolong; Wang, Junrun; Zhang, Yu; Li, Jianyi; Xia, Li; Zhang, Jie; Ding, Yanyan; Jiang, Bing; Huang, Zhiwu; Ma, Zhanwen; Wei, Zheng; Qian, Xiangping; Xu, Dapeng; Lan, Changlin; Yao, Zeen

    2016-03-01

    An intense D-T/D-D neutron generator is currently being developed at the Lanzhou University. The Cockcroft-Walton accelerator, as a part of the neutron generator, will be used to accelerate and transport the high-current low-energy beam from the duoplasmatron ion source to the rotating target. The design of a high-current low-energy beam transport (LEBT) line and the dynamics simulations of the mixed beam were carried out using the TRACK code. The results illustrate that the designed beam line facilitates smooth transportation of a deuteron beam of 40 mA, and the number of undesired ions can be reduced effectively using two apertures.

  6. Computation of potentials from current electrodes in cylindrically stratified media: A stable, rescaled semi-analytical formulation

    NASA Astrophysics Data System (ADS)

    Moon, Haksu; Teixeira, Fernando L.; Donderici, Burkay

    2015-01-01

    We present an efficient and robust semi-analytical formulation to compute the electric potential due to arbitrary-located point electrodes in three-dimensional cylindrically stratified media, where the radial thickness and the medium resistivity of each cylindrical layer can vary by many orders of magnitude. A basic roadblock for robust potential computations in such scenarios is the poor scaling of modified-Bessel functions used for computation of the semi-analytical solution, for extreme arguments and/or orders. To accommodate this, we construct a set of rescaled versions of modified-Bessel functions, which avoids underflows and overflows in finite precision arithmetic, and minimizes round-off errors. In addition, several extrapolation methods are applied and compared to expedite the numerical evaluation of the (otherwise slowly convergent) associated Sommerfeld-type integrals. The proposed algorithm is verified in a number of scenarios relevant to geophysical exploration, but the general formulation presented is also applicable to other problems governed by Poisson equation such as Newtonian gravity, heat flow, and potential flow in fluid mechanics, involving cylindrically stratified environments.

  7. Improving Agreement between the Neutron Yield Scaling Model of Fast Z-pinches with Experimental Data Using the Time Derivative of the Current

    NASA Astrophysics Data System (ADS)

    Bures, Brian; Krishnan, Mahadevan

    2012-10-01

    The Z-pinch community has accepted a power law scaling of the DD neutron yield with current (Y=aI^d) for decades. While the exponent, d, in the power law has received much of the attention in literature (3.5neutron yield and the current has received little attention. Yet once an exponent is selected, typically around 4, the experimental data are observed to show a standard deviation of 3000% or more relative to the model prediction with a scalar value for a. We have revised the long standing scaling relationship by replacing this scalar constant with a linear function of the minimum in the time derivative of the current (Y=(bdI/dt+c)I^d). Our revised scaling relationship reduces the standard deviation in DD neutron yield to ˜100% from 25,000%, on Z-pinch machines with peak currents ranging from 60 kA to 18 MA. The improved correlation of measured yield on both I and dI/dt motivates an examination of microscopic dynamics in these pinches., The dI/dt term is related to the pinch voltage that in turn is the source term for the fast ion spectrum that drives beam-target fusion.

  8. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    industry, from the initial fuel enrichment and fabrication processes right through to storage or reprocessing, and neutron metrology is clearly important in this area. Neutron fields do, however, occur in other areas, for example where neutron sources are used in oil well logging and moisture measurements. They also occur around high energy accelerators, including photon linear accelerators used for cancer therapy, and are expected to be a more serious problem around the new hadron radiation therapy facilities. Roughly 50% of the cosmic ray doses experienced by fliers at the flight altitudes of commercial aircraft are due to neutrons. Current research on fusion presents neutron metrology with a whole new range of challenges because of the very high fluences expected. One of the most significant features of neutron fields is the very wide range of possible neutron energies. In the nuclear industry, for example, neutrons occur with energies from those of thermal neutrons at a few meV to the upper end of the fission spectrum at perhaps 10 MeV. For cosmic ray dosimetry the energy range extends into the GeV region. This enormous range sets a challenge for designing measuring devices and a parallel challenge of developing measurement standards for characterizing these devices. One of the major considerations when deciding on topics for this special issue was agreeing on what not to include. Modelling, i.e. the use of radiation transport codes, is now a very important aspect of neutron measurements. These calculations are vital for shielding and for instrument design; nevertheless, the topic has only been included here where it has a direct bearing on metrology and the development of standards. Neutron spectrometry is an increasingly important technique for unravelling some of the problems of dose equivalent measurements and for plasma diagnostics in fusion research. However, this topic is at least one step removed from primary metrology and so it was felt that it should not be

  9. Semiconductor neutron detector

    DOEpatents

    Ianakiev, Kiril D.; Littlewood, Peter B.; Blagoev, Krastan B.; Swinhoe, Martyn T.; Smith, James L.; Sullivan, Clair J.; Alexandrov, Boian S.; Lashley, Jason Charles

    2011-03-08

    A neutron detector has a compound of lithium in a single crystal form as a neutron sensor element. The lithium compound, containing improved charge transport properties, is either lithium niobate or lithium tantalate. The sensor element is in direct contact with a monitor that detects an electric current. A signal proportional to the electric current is produced and is calibrated to indicate the neutrons sensed. The neutron detector is particularly useful for detecting neutrons in a radiation environment. Such radiation environment may, e.g. include gamma radiation and noise.

  10. An Improved Neutron Transport Algorithm for HZETRN

    NASA Technical Reports Server (NTRS)

    Slaba, Tony C.; Blattnig, Steve R.; Clowdsley, Martha S.; Walker, Steven A.; Badavi, Francis F.

    2010-01-01

    Long term human presence in space requires the inclusion of radiation constraints in mission planning and the design of shielding materials, structures, and vehicles. In this paper, the numerical error associated with energy discretization in HZETRN is addressed. An inadequate numerical integration scheme in the transport algorithm is shown to produce large errors in the low energy portion of the neutron and light ion fluence spectra. It is further shown that the errors result from the narrow energy domain of the neutron elastic cross section spectral distributions, and that an extremely fine energy grid is required to resolve the problem under the current formulation. Two numerical methods are developed to provide adequate resolution in the energy domain and more accurately resolve the neutron elastic interactions. Convergence testing is completed by running the code for various environments and shielding materials with various energy grids to ensure stability of the newly implemented method.

  11. Non-covalent formulation of active principles with dendrimers: Current state-of-the-art and prospects for further development.

    PubMed

    Elkin, Igor; Banquy, Xavier; Barrett, Christopher J; Hildgen, Patrice

    2017-09-06

    During the last three decades, dendrimers, nano-sized highly-branched fractal-like symmetrical macromolecules, have been intensively studied as promising candidates for application as drug-delivery carriers. Among other important characteristics arising from their unique and highly-controlled architecture, size and surface properties, the possibility of hosting guest molecules in internal voids represents a key advantage underlying the potential of dendrimers as non-covalent drug-encapsulating agents. The impressive amount of accumulating experimental results to date allows researchers to identify the most important and promising theoretical and practical aspects of the use of dendrimers for this purpose. This review covers the main factors, phenomena, and mechanisms involved in this drug-vectorization approach, including mechanisms of non-covalent dendrimer-drug association, dendrimer-dendrimer interactions, as well as biological properties relevant to the host dendrimers. A discussion is then provided to illustrate some successful existing formulation strategies as well as to propose some new possible ones to optimize further development of the field. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Relativistic two-component formulation of time-dependent current-density functional theory: application to the linear response of solids.

    PubMed

    Romaniello, P; de Boeij, P L

    2007-11-07

    In this paper we derive the relativistic two-component formulation of time-dependent current-density-functional theory. To arrive at a two-component current-density formulation we apply a Foldy-Wouthuysen-type transformation to the time-dependent four-component Dirac-Kohn-Sham equations of relativistic density-functional theory. The two-component Hamiltonian is obtained as a regular expansion which is gauge invariant at each order of approximation, and to zeroth order it represents the time-dependent version of the relativistic zeroth order regular Hamiltonian obtained by van Lenthe et al., for the ground state [J. Chem. Phys.99, 4597 (1993)]. The corresponding zeroth order regular expression for the density is unchanged, whereas the current-density operator now comprises a paramagnetic, a diamagnetic, and a spin contribution, similar to the Gordon decomposition of the Dirac four current. The zeroth order current density is directly related to the mean velocity corresponding to the zeroth order Hamiltonian. These density and current density operators satisfy the continuity equation. This zeroth order approximation is therefore consistent and physically realistic. By combining this formalism with the formulation of the linear response of solids within time-dependent current-density functional theory [Romaniello and de Boeij, Phys. Rev. B71, 155108 (2005)], we derive a method that can treat orbital and spin contributions to the response in a unified way. The effect of spin-orbit coupling can now be taken into account. As first test we apply the method to calculate the relativistic effects in the linear response of several metals and nonmetals to a macroscopic electric field. Treatment of spin-orbit coupling yields visible changes in the spectra: a smooth onset of the interband transitions in the absorption spectrum of Au, a sharp onset with peak at about 0.46 eV in the absorption spectrum of W, and a low-frequency doublet structure in the absorption spectra of Zn

  13. Research on anisotropy of fusion-produced protons and neutrons emission from high-current plasma-focus discharges

    NASA Astrophysics Data System (ADS)

    Malinowski, K.; Skladnik-Sadowska, E.; Sadowski, M. J.; Szydlowski, A.; Czaus, K.; Kwiatkowski, R.; Zaloga, D.; Paduch, M.; Zielinska, E.

    2015-01-01

    The paper concerns fast protons and neutrons from D-D fusion reactions in a Plasma-Focus-1000U facility. Measurements were performed with nuclear-track detectors arranged in "sandwiches" of an Al-foil and two PM-355 detectors separated by a polyethylene-plate. The Al-foil eliminated all primary deuterons, but was penetrable for fast fusion protons. The foil and first PM-355 detector were penetrable for fast neutrons, which were converted into recoil-protons in the polyethylene and recorded in the second PM-355 detector. The "sandwiches" were irradiated by discharges of comparable neutron-yields. Analyses of etched tracks and computer simulations of the fusion-products behavior in the detectors were performed.

  14. Research on anisotropy of fusion-produced protons and neutrons emission from high-current plasma-focus discharges

    SciTech Connect

    Malinowski, K. Sadowski, M. J.; Szydlowski, A.; Skladnik-Sadowska, E.; Czaus, K.; Kwiatkowski, R.; Zaloga, D.; Paduch, M.; Zielinska, E.

    2015-01-15

    The paper concerns fast protons and neutrons from D-D fusion reactions in a Plasma-Focus-1000U facility. Measurements were performed with nuclear-track detectors arranged in “sandwiches” of an Al-foil and two PM-355 detectors separated by a polyethylene-plate. The Al-foil eliminated all primary deuterons, but was penetrable for fast fusion protons. The foil and first PM-355 detector were penetrable for fast neutrons, which were converted into recoil-protons in the polyethylene and recorded in the second PM-355 detector. The “sandwiches” were irradiated by discharges of comparable neutron-yields. Analyses of etched tracks and computer simulations of the fusion-products behavior in the detectors were performed.

  15. Addressing current medical needs in invasive fungal infection prevention and treatment with new antifungal agents, strategies and formulations.

    PubMed

    Pitman, Stuart K; Drew, Richard H; Perfect, John R

    2011-09-01

    Introduction: Morbidity and mortality associated with invasive fungal infections (IFIs) remains unacceptably high. Such diseases represent a substantial burden to the healthcare system. New options are needed to address antifungal resistance in existing and emerging pathogens and improve treatment outcomes while minimizing drug-related toxicities and interactions. Awareness of new and potential future options is of great value for those healthcare professionals who care for patients with IFIs. Areas covered: A search of PubMed, infectious diseases conference abstracts and reference lists from relevant publications was conducted and relevant information abstracted. This review describes the limitations of existing systemic antifungal therapies (e.g., resistance, drug-drug interactions, drug-related toxicities) and summarizes data regarding several emerging antifungal compounds including (but not limited to) new triazoles (e.g. isavuconazole, ravuconazole), echinocandins (e.g., aminocandin) and nikkomycin Z. Agents in clinical trials such as (but not limited to) new triazoles (e.g., isavuconazole, ravuconazole), echinocandins (e.g., aminocandin) and nikkomycin are included. New formulations of existing drugs including reformulations of miconazole, posaconazole and amphotericin B are also reviewed. Finally, new or novel administration strategies for existing drugs such as combination antifungal therapy, antifungal dose escalation, adjunctive use of iron chelators and preemptive therapy are discussed. Expert opinion: All present antifungal agents have some deficiencies in antifungal spectra, toxicity, pharmacokinetics and/or drug-drug interactions, making them less than ideal for some fungal infections. Therefore, there remains an urgent need to find safe, effective, rapidly fungicidal, broad-spectrum antifungal agents with excellent pharmacodynamics to effectively eliminate the fungus from the body with short antifungal courses.

  16. Solutions Network Formulation Report. Improving NOAA's Tides and Currents Through Enhanced Data Inputs from NASA's Ocean Surface Topography Mission

    NASA Technical Reports Server (NTRS)

    Guest, DeNeice C.

    2006-01-01

    The Nation uses water-level data for a variety of practical purposes, including hydrography, nautical charting, maritime navigation, coastal engineering, and tsunami and storm surge warnings (NOAA, 2002; Digby et al., 1999). Long-term applications include marine boundary determinations, tidal predictions, sea-level trend monitoring, oceanographic research, and climate research. Accurate and timely information concerning sea-level height, tide, and ocean current is needed to understand their impact on coastal management, disaster management, and public health. Satellite altimeter data products are currently used by hundreds of researchers and operational users to monitor ocean circulation and to improve scientists understanding of the role of the oceans in climate and weather. The NOAA (National Oceanic and Atmospheric Administration) National Ocean Service has been monitoring sea-level variations for many years (NOAA, 2006). NOAA s Tides & Currents DST (decision support tool, managed by the Center for Operational Oceanographic Products and Services, is the portal to a vast collection of oceanographic and meteorological data (historical and real-time), predictions, and nowcasts and forecasts. This report assesses the capacity of NASA s satellite altimeter data to meet societal decision support needs through incorporation into NOAA s Tides & Currents.

  17. Current distribution in skeletal muscle activated by functional electrical stimulation: image-series formulation and isometric recruitment curve.

    PubMed

    Livshitz, L M; Einziger, P D; Mizrahi, J

    2000-01-01

    The present work develops an analytical model that allows one to estimate the current distribution within the whole muscle and the resulting isometric recruitment curve (IRC). The quasistatic current distribution, expressed as an image series, i.e., a collection of properly weighted and shifted point-source responses, outlines an extension for more than three layers of the classical image theory in conductive plane-stratified media. Evaluation of the current distribution via the image series expansions requires substantially less computational time than the standard integral representation. The expansions use a unique recursive representation for Green's function, that is a generic characteristic of the stratification. This approach permits one to verify which of the tissue electrical properties are responsible for the current density distribution within the muscle, and how significant their combinations are. In addition, the model permits one to study the effect of different electrode placement on the shape and the magnitude of the potential distribution. A simple IRC model was used for parameter estimation and model verification by comparison with experimentally obtained isometric recruitment curves. Sensitivity of the model to different parameters such as conductivity of the tissues and activation threshold was verified. The resulting model demonstrated characteristic features that were similar to those of experimentally obtained data. The model also quantitatively confirmed the differences existing between surface (transcutaneous) and implanted (percutaneous) electrode stimulation.

  18. A novel method for modeling the neutron time of flight (nTOF) detector response in current mode to inertial confinement fusion experiments.

    SciTech Connect

    Nelson, Alan J.; Cooper, Gary Wayne; Ruiz, Carlos L.; Chandler, Gordon Andrew; Fehl, David Lee; Hahn, Kelly Denise; Leeper, Ramon Joe; Smelser, Ruth Marie; Torres, Jose A.

    2013-09-01

    There are several machines in this country that produce short bursts of neutrons for various applications. A few examples are the Zmachine, operated by Sandia National Laboratories in Albuquerque, NM; the OMEGA Laser Facility at the University of Rochester in Rochester, NY; and the National Ignition Facility (NIF) operated by the Department of Energy at Lawrence Livermore National Laboratory in Livermore, California. They all incorporate neutron time of flight (nTOF) detectors which measure neutron yield, and the shapes of the waveforms from these detectors contain germane information about the plasma conditions that produce the neutrons. However, the signals can also be %E2%80%9Cclouded%E2%80%9D by a certain fraction of neutrons that scatter off structural components and also arrive at the detectors, thereby making analysis of the plasma conditions more difficult. These detectors operate in current mode - i.e., they have no discrimination, and all the photomultiplier anode charges are integrated rather than counted individually as they are in single event counting. Up to now, there has not been a method for modeling an nTOF detector operating in current mode. MCNPPoliMiwas developed in 2002 to simulate neutron and gammaray detection in a plastic scintillator, which produces a collision data output table about each neutron and photon interaction occurring within the scintillator; however, the postprocessing code which accompanies MCNPPoliMi assumes a detector operating in singleevent counting mode and not current mode. Therefore, the idea for this work had been born: could a new postprocessing code be written to simulate an nTOF detector operating in current mode? And if so, could this process be used to address such issues as the impact of neutron scattering on the primary signal? Also, could it possibly even identify sources of scattering (i.e., structural materials) that

  19. 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.

  20. 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.

  1. Analytical drain current formulation for gate dielectric engineered dual material gate-gate all around-tunneling field effect transistor

    NASA Astrophysics Data System (ADS)

    Madan, Jaya; Gupta, R. S.; Chaujar, Rishu

    2015-09-01

    In this work, an analytical drain current model for gate dielectric engineered (hetero dielectric)-dual material gate-gate all around tunnel field effect transistor (HD-DMG-GAA-TFET) has been developed. Parabolic approximation has been used to solve the two-dimensional (2D) Poisson equation with appropriate boundary conditions and continuity equations to evaluate analytical expressions for surface potential, electric field, tunneling barrier width and drain current. Further, the analog performance of the device is studied for three high-k dielectrics (Si3N4, HfO2, and ZrO2), and it has been investigated that the problem of lower ION, can be overcome by using the hetero-gate architecture. Moreover, the impact of scaling the gate oxide thickness and bias variations has also been studied. The HD-DMG-GAA-TFET shows an enhanced ION of the order of 10-4 A. The effectiveness of the proposed model is validated by comparing it with ATLAS device simulations.

  2. Correlated evolution of barrier capacitance charging, generation, and drift currents and of carrier lifetime in Si structures during 25 MeV neutrons irradiation

    SciTech Connect

    Gaubas, E.; Ceponis, T.; Jasiunas, A.; Uleckas, A.; Vaitkus, J.; Cortina, E.; Militaru, O.

    2012-12-03

    The in situ examination of barrier capacitance charging, of generation and drift currents, and of carrier lifetime in Si structures during 25 MeV neutrons irradiation has been implemented to correlate radiation induced changes in carrier recombination, thermal release, and drift characteristics and to clarify their impact on detector performance. It has been shown that microwave probed photo-conductivity technique implemented in contact-less and distant manner can be a powerful tool for examination in wide dynamic range of carrier lifetime modified by radiation defects and for rather precise prediction of detector performance.

  3. Effect of high current electron beam in a 30 MeV radio frequency linac for neutron-time-of-flight applications

    NASA Astrophysics Data System (ADS)

    Nayak, B.; Acharya, S.; Rajawat, R. K.; DasGupta, K.

    2016-01-01

    A high power pulsed radio frequency electron linac is designed by BARC, India to accelerate 30 MeV, 10 A, 10 ns beam for neutron-time-of-flight applications. It will be used as a neutron generator and will produce ˜1012-1013 n/s. It is essential to reduce the beam instability caused by space charge effect and the beam cavity interaction. In this paper, the wakefield losses in the accelerating section due to bunch of RMS (Root mean square) length 2 mm (at the gun exit) is analysed. Loss and kick factors are numerically calculated using CST wakefield solver. Both the longitudinal and transverse wake potentials are incorporated in beam dynamics code ELEGANT to find the transverse emittance growth of the beam propagating through the linac. Beam loading effect is examined by means of numerical computation carried out in ASTRA code. Beam break up start current has been estimated at the end of the linac which arises due to deflecting modes excited by the high current beam. At the end, transverse beam dynamics of such high current beam has been analysed.

  4. Effect of high current electron beam in a 30 MeV radio frequency linac for neutron-time-of-flight applications

    SciTech Connect

    Nayak, B. Acharya, S.; Rajawat, R. K.; DasGupta, K.

    2016-01-15

    A high power pulsed radio frequency electron linac is designed by BARC, India to accelerate 30 MeV, 10 A, 10 ns beam for neutron-time-of-flight applications. It will be used as a neutron generator and will produce ∼10{sup 12}–10{sup 13} n/s. It is essential to reduce the beam instability caused by space charge effect and the beam cavity interaction. In this paper, the wakefield losses in the accelerating section due to bunch of RMS (Root mean square) length 2 mm (at the gun exit) is analysed. Loss and kick factors are numerically calculated using CST wakefield solver. Both the longitudinal and transverse wake potentials are incorporated in beam dynamics code ELEGANT to find the transverse emittance growth of the beam propagating through the linac. Beam loading effect is examined by means of numerical computation carried out in ASTRA code. Beam break up start current has been estimated at the end of the linac which arises due to deflecting modes excited by the high current beam. At the end, transverse beam dynamics of such high current beam has been analysed.

  5. 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)

  6. 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.

  7. Fast neutron damage in silicon detectors

    SciTech Connect

    Kraner, H.W.; Li, Z.; Poesnecker, K.U.

    1988-08-01

    Radiation effects of fast neutrons have been measured in silicon detectors of varying resistivity irradiated to approx. 10/sup 11/ n/cm/sup 2/ over periods of weeks. The principal damage effect is increased leakage current due to generation of carriers from defect levels in the depletion region. Damage and leakage current constants have been established for detector resistivities between 10 and 27,000 ohm-cm and lie in the range of 0.7 /minus/ 2 /times/ 10E7 sec/cm/sup 2/ (K) for PuBe neutrons. A slight increase in K was observed for higher resistivities which translates into somewhat improved radiation hardness. A fit of this data was attempted to a two-level recombination formulation of the damage constant. 13 refs., 6 figs., 1 tab.

  8. Constraints on the Formation of Double Neutron Stars from the Observed Eccentricities and Current Limits on Merger Rates

    NASA Astrophysics Data System (ADS)

    Chruslinska, M.; Belczynski, K.; Bulik, T.; Gladysz, W.

    2017-03-01

    We employ population synthesis method to model the double neutron star (DNS) population and test various possibilities on natal kick velocities gained by neutron stars after their formation. We first choose natal kicks after standard core collapse supernovae (CCSN) from a Maxwellian distribution with velocity dispersion of σ = 265 km/s as proposed by Hobbs and then modify this distribution by changing σ toward smaller and larger kick values. We also take into account the possibility of NS formation through electron capture supernova. In this case we test two scenarios: zero natal kick or small natal kick, drawn from Maxwellian distribution with σ = 26.5 km/s. We calculate the present-day orbital parameters of binaries and compare the resulting eccentricities with those known for observed DNSs. As an additional test we calculate Galactic merger rates for our model populations and confront them with observational limits. We do not find any model unequivocally consistent with both observational constraints simultaneously. The models with low kicks after CCSN for binaries with the second NS forming through core collapse SN are marginally consistent with the observations. This means that either 14 observed DNSs are not representative of the intrinsic Galactic population, or that our modeling of DNS formation needs revision.

  9. Studies of deep levels in high resistivity silicon detectors irradiated by high fluence fast neutrons using a thermally stimulated current spectrometer

    SciTech Connect

    Li, Z.; Kraner, H.W.; Chen, W.; Beuttenmuller, R.; Biggeri, U.; Bruzzi, M.; Borchi, E.; Baldini, A.; Spillantini, P. |

    1993-04-01

    Measurements of deep level spectrum of high resistivity silicon detectors irradiated by high fluence fast neutrons ({Phi}{sub n}: 2 {times} 10{sup 12}n/cm{sup 2}) have been made using a thermally stimulated current (TSC) spectrometer. It has been found that at least nine new defect levels, with peaking temperature of 19K, 27K, 36K, 44K, 49K, 83K, 93K, 105K, and 120K, begin to appear when {Phi}{sub n} {ge} 1 {times} 10{sup 13}n/cm. All peaks have strong dependences on the filling voltage (V{sub fill}, forward bias) or injection current especially for high fluence ({Phi}{sub n} {ge} 10{sup 13} n/cm{sup 2}) situations. The defect concentration, energy level in the band gap, and cross section of each deep level, totaling, at least 13, have been studied systematically and possible identifications of the levels have been discussed.

  10. Prototype Stilbene Neutron Collar

    SciTech Connect

    Prasad, M. K.; Shumaker, D.; Snyderman, N.; Verbeke, J.; Wong, J.

    2016-10-26

    A neutron collar using stilbene organic scintillator cells for fast neutron counting is described for the assay of fresh low enriched uranium (LEU) fuel assemblies. The prototype stilbene collar has a form factor similar to standard He-3 based collars and uses an AmLi interrogation neutron source. This report describes the simulation of list mode neutron correlation data on various fuel assemblies including some with neutron absorbers (burnable Gd poisons). Calibration curves (doubles vs 235U linear mass density) are presented for both thermal and fast (with Cd lining) modes of operation. It is shown that the stilbene collar meets or exceeds the current capabilities of He-3 based neutron collars. A self-consistent assay methodology, uniquely suited to the stilbene collar, using triples is described which complements traditional assay based on doubles calibration curves.

  11. Ultracold neutron detector for neutron lifetime measurements

    NASA Astrophysics Data System (ADS)

    Andreev, V.; Vassiljev, A.; Ivanov, E.; Ilyin, D.; Krivshich, A.; Serebrov, A.

    2017-02-01

    The gas-filled detector of ultracold neutrons has been designed and constructed for the spectrometer of the neutron lifetime measurements at the ILL, Grenoble, France. The detector has been successfully tested and is currently being used at this spectrometer. We could show that minimization of the ;wall; effect is a key factor to ensure efficient background suppression and to maximize the detection efficiency. This effect is primarily related to the composition of the gas mixture, which crucially depends on the neutron velocity spectrum.

  12. Formal analysis of the urban 'Dutch model' with aims of re-formulating spatial quality concerns for pedestrian precincts in current New Town developments.

    PubMed

    Ishida, Toshikazu

    2005-01-01

    In the Japanese post WWII urban planning and design field, concerns for formal features regarding the sequential street-front visual image in new high-density urban spaces have been a rather subordinated subject. Famous New Town schemes such as Tsukuba Science City (1963), or Minato Mirai 21 (1965) for instance, are typical inland and reclaimed land examples that summarize the validity and limitations of functional zoning systems applied to these artificial urban developments for the last half century. In those examples, the interaction between space mobility and land use has not been explored sufficiently in order to create attractive street-front images, yet such interaction is essential to the way the cityscape and its character are perceived by the eye. However, current insight regarding the sustainable New Town paradigm has brought a renewed perspective regarding design policy of the pedestrian precinct. This study investigates the formal features of the sequential street-front image of Dutch late-medieval town examples which could help re-formulate the existing design policies regarding the quality of pedestrian space especially in the artificial reclaimed land design field. The purpose is to find out how the principles of those old high-density artificial environmental design models generate such effective interaction between mobility and land usage, creating an enriched aesthetic visual image of street-front space as a result.

  13. Feasibility of creating a specialized reactimeter based on the inverse solution to kinetics equation with a current-mode neutron detector

    SciTech Connect

    Koshelev, A. S. Arapov, A. V.; Ovchinnikov, M. A.

    2016-12-15

    The file-evaluation results of a reactimeter based on the inverse solution to the kinetics equation (ISKE) are presented, which were obtained using an operating hardware-measuring complex with a KNK-4 neutron detector working in the current mode. The processing of power-recording files of the BR-1M, BR-K1, and VIR-2M reactors of the Russian Federal Nuclear Center—All-Russian Research Institute of Experimental Physics, which was performed with the use of Excel simulation of the ISKE formalism, demonstrated the feasibility of implementation of the reactivity monitoring (during the operation of these reactors at stationary power) beginning from the level of ~5 × 10{sup –4}β{sub eff}.

  14. Defects in {sup 6}LiInSe{sub 2} neutron detector investigated by photo-induced current transient spectroscopy and photoluminescence

    SciTech Connect

    Cui, Yunlong; Bhattacharya, Pijush; Buliga, Vladimir; Tupitsyn, Eugene; Rowe, Emmanuel; Wiggins, Brenden; Johnstone, Daniel; Stowe, Ashley; Burger, Arnold

    2013-08-26

    {sup 6}LiInSe{sub 2} is a promising thermal neutron semiconductor detector material. The performance of the detector is affected by the carrier mobility-lifetime products. Therefore, defects that function as carrier recombination centers need to be identified. In this letter, characterization of defect levels in {sup 6}LiInSe{sub 2} by photo-induced current transient spectroscopy (PICTS) and photoluminescence is reported. PICTS measurements revealed electron-related defects located at 0.22, 0.36, and 0.55 eV and hole-related defects at 0.19, 0.30, and 0.73 eV. Free exciton and donor-acceptor pairs (DAP) emissions were observed. The PICTS defect level values are consistent with those extracted from DAP transitions.

  15. Feasibility of creating a specialized reactimeter based on the inverse solution to kinetics equation with a current-mode neutron detector

    NASA Astrophysics Data System (ADS)

    Koshelev, A. S.; Arapov, A. V.; Ovchinnikov, M. A.

    2016-12-01

    The file-evaluation results of a reactimeter based on the inverse solution to the kinetics equation (ISKE) are presented, which were obtained using an operating hardware-measuring complex with a KNK-4 neutron detector working in the current mode. The processing of power-recording files of the BR-1M, BR-K1, and VIR-2M reactors of the Russian Federal Nuclear Center—All-Russian Research Institute of Experimental Physics, which was performed with the use of Excel simulation of the ISKE formalism, demonstrated the feasibility of implementation of the reactivity monitoring (during the operation of these reactors at stationary power) beginning from the level of 5 × 10-4βeff.

  16. The 14 MeV Neutron Irradiation Facility in MARIA Reactor

    SciTech Connect

    Prokopowicz, R.; Pytel, K.; Dorosz, M.; Zawadka, A.; Lechniak, J.; Lipka, M.; Marcinkowska, Z.; Wierzchnicka, M.; Malkiewicz, A.; Wilczek, I.; Krok, T.; Migdal, M.; Koziel, A.

    2015-07-01

    formulate its operation limits and conditions. During first tested operation of the converter the 14 MeV neutron flux density was estimated to 10{sup 9} cm{sup -2} s{sup -1}, whereas fast fission neutrons inside converter achieved 10{sup 12} cm{sup -2} s{sup -1}, and thermal neutrons were reduced down to 109 cm-2 s-1. Taking into account the feasibility of almost incessant converter operation for a number of months, its arisen as one of the most powerful (in terms of fluence), currently available 14 MeV neutron source. Such a converter currently under operation in the MARIA reactor core will be presented. (authors)

  17. The Fundamental Neutron Physics Beamline at the Spallation Neutron Source

    PubMed Central

    Greene, Geoffrey; Cianciolo, Vince; Koehler, Paul; Allen, Richard; Snow, William Michael; Huffman, Paul; Gould, Chris; Bowman, David; Cooper, Martin; Doyle, John

    2005-01-01

    The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory with an anticipated start-up in early 2006, will provide the most intense pulsed beams of cold neutrons in the world. At a projected power of 1.4 MW, the time averaged fluxes and fluences of the SNS will approach those of high flux reactors. One of the flight paths on the cold, coupled moderator will be devoted to fundamental neutron physics. The fundamental neutron physics beamline is anticipated to include two beam-lines; a broad band cold beam, and a monochromatic beam of 0.89 nm neutrons for ultracold neutron (UCN) experiments. The fundamental neutron physics beamline will be operated as a user facility with experiment selection based on a peer reviewed proposal process. An initial program of five experiments in neutron decay, hadronic weak interaction and time reversal symmetry violation have been proposed. PMID:27308112

  18. Boron nitride solid state neutron detector

    DOEpatents

    Doty, F. Patrick

    2004-04-27

    The present invention describes an apparatus useful for detecting neutrons, and particularly for detecting thermal neutrons, while remaining insensitive to gamma radiation. Neutrons are detected by direct measurement of current pulses produced by an interaction of the neutrons with hexagonal pyrolytic boron nitride.

  19. Formulation techniques for nanofluids.

    PubMed

    Rivera-Solorio, Carlos I; Payán-Rodríguez, Luis A; García-Cuéllar, Alejandro J; Ramón-Raygoza, E D; L Cadena-de-la-Peña, Natalia; Medina-Carreón, David

    2013-11-01

    Fluids with suspended nanoparticles, commonly known as nanofluids, may be formulated to improve the thermal performance of industrial heat transfer systems and applications. Nanofluids may show enhanced thermal and electrical properties such as thermal conductivity, viscosity, heat transfer coefficient, dielectric strength, etc. However, stability problems may arise as nanoparticles usually have the tendency to agglomerate and sediment producing deterioration in the increment of these properties. In this review, we discuss patents that report advances in the formulation of nanofluids including: production methods, selection of components (nanoparticles, base fluid and surfactants), their chemical compositions and morphologies, and characterization techniques. Finally, current and future directions in the development of nanofluid formulation are discussed.

  20. Study of the neutron beam line shield design for JSNS.

    PubMed

    Kawai, M; Saito, K; Sanami, T; Nakao, N; Maekawa, F

    2005-01-01

    The JSNS, a spallation neutron source of J-PARC (JAERI-KEK Joint Project of the High Intensity Proton Accelerator) has 23 neutron beam lines. In the present study, a database was formulated for an optimum shielding design using the MCNP-X code. The calculations involved two steps. In the first step, the neutron distributions were created in the typical neutron beam line with a model that included the spallation neutron source target. The neutron currents evaluated flowed from the duct into the duct wall which was the boundary source for the bulk shield surrounding the beam line. In the second step, bulk-shield calculations were performed for the various shielding materials (iron, concrete, heavy concrete and so on) used and their composites up to thicknesses of 3 m. The results were compared with each other. Composite material shields of iron and such hydrogeneous materials as polyethylene or concrete were more effective. A typical design was prepared for a beam line within 25 m distance from a moderator, as a sample.

  1. Coated Fiber Neutron Detector Test

    SciTech Connect

    Lintereur, Azaree T.; Ely, James H.; Kouzes, Richard T.; Stromswold, David C.

    2009-10-23

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Reported here are the results of tests of the 6Li/ZnS(Ag)-coated non-scintillating plastic fibers option. This testing measured the required performance for neutron detection efficiency and gamma ray rejection capabilities of a system manufactured by Innovative American Technology (IAT).

  2. 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.

  3. Neutron stars - General review

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.; Canuto, V.

    1974-01-01

    A review is presented of those properties of neutron stars upon which there is general agreement and of those areas which currently remain in doubt. Developments in theoretical physics of neutron star interiors are summarized with particular attention devoted to hyperon interactions and the structure of interior layers. Determination of energy states and the composition of matter is described for successive layers, beginning with the surface and proceeding through the central region into the core. Problems encountered in determining the behavior of matter in the ultra-high density regime are discussed, and the effects of the magnetic field of a neutron star are evaluated along with the behavior of atomic structures in the field. The evolution of a neutron star is outlined with discussion centering on carbon detonation, cooling, vibrational damping, rotation, and pulsar glitches. The role of neutron stars in cosmic-ray propagation is considered.

  4. Accelerator based epithermal neutron source

    NASA Astrophysics Data System (ADS)

    Taskaev, S. Yu.

    2015-11-01

    We review the current status of the development of accelerator sources of epithermal neutrons for boron neutron capture therapy (BNCT), a promising method of malignant tumor treatment. Particular attention is given to the source of epithermal neutrons on the basis of a new type of charged particle accelerator: tandem accelerator with vacuum insulation and lithium neutron-producing target. It is also shown that the accelerator with specialized targets makes it possible to generate fast and monoenergetic neutrons, resonance and monoenergetic gamma-rays, alpha-particles, and positrons.

  5. The COHERENT collaboration: an effort to observe coherent, elastic, neutral-current neutrino-nucleus scattering at the Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Rich, Grayson; Coherent Collaboration

    2014-09-01

    The phenomenon of coherent, neutral-current scattering of neutrinos from nuclei was first proposed by D.Z. Freedman in 1974, who posited that an effort to observe this effect experimentally ``may be an act of hubris'' owing to extreme experimental difficulties. Taking advantage of technologies which have come to maturity and new experience gained in the intervening 40 years, the newly-formed COHERENT collaboration seeks to measure for the first time coherent, elastic neutrino-nucleus scattering (CE ν NS). Using neutrinos created by stopped pions at the Spallation Neutron Source (SNS) of Oak Ridge National Laboratory, several detector systems will be deployed to limit systematic uncertainties and unambiguously observe the N2 -dependence on the cross section. The current status of the efforts of the collaboration will be addressed, focusing on detector technologies and calibration of these detectors for low-energy nuclear recoils. We will also discuss the longer-term physics goals of the collaboration, including astrophysical implications of the measurements and the use CE ν NS as a probe to search for non-standard neutrino interactions and as a way to measure the weak mixing angle.

  6. Current-carrying element based on second-generation high-temperature superconductor for the magnet system of a fusion neutron source

    SciTech Connect

    Novikov, M. S. Ivanov, D. P. E-mail: denis.ivanov30@mail.ru; Novikov, S. I. Shuvaev, S. A. E-mail: sergey.shuvaev@phystech.edu

    2015-12-15

    Application of current-carrying elements (CCEs) made of second-generation high-temperature superconductor (2G HTS) in magnet systems of a fusion neutron source (FNS) and other fusion devices will allow their magnetic field and thermodynamic stability to be increased substantially in comparison with those of low-temperature superconductor (LTS) magnets. For a toroidal magnet of the FNS, a design of a helical (partially transposed) CCE made of 2G HTS is under development with forced-flow cooling by helium gas, a current of 20–30 kA, an operating temperature of 10–20 K, and a magnetic field on the winding of 12–15 T (prospectively ∼20 T). Short-sized samples of the helical flexible heavy-current CCE are being fabricated and investigated; a pilot-line unit for production of long-sized CCE pieces is under construction. The applied fabrication technique allows the CCE to be produced which combines a high operating current, thermal and mechanical stability, manufacturability, and low losses in the alternating modes. The possibility of fabricating the CCE with the outer dimensions and values of the operating parameter required for the FNS (and with a significant margin) using already available serial 2G HTS tapes is substantiated. The maximum field of toroidal magnets with CCEs made of 2G HTS will be limited only by mechanical properties of the magnet’s casing and structure, while the thermal stability will be approximately two orders of magnitude higher than that of toroidal magnets with LTS-based CCEs. The helical CCE made of 2G HTS is very promising for fusion and hybrid electric power plants, and its design and technologies of production, as well as the prototype coils made of it for the FNS and other tokamaks, are worth developing now.

  7. Neutron skins and neutron stars

    SciTech Connect

    Piekarewicz, J.

    2013-11-07

    The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ('PREX') at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in {sup 208}Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron beams may impact the physics of neutron stars.

  8. Analytical applications for delayed neutrons

    SciTech Connect

    Eccleston, G.W.

    1983-01-01

    Analytical formulations that describe the time dependence of neutron populations in nuclear materials contain delayed-neutron dependent terms. These terms are important because the delayed neutrons, even though their yields in fission are small, permit control of the fission chain reaction process. Analytical applications that use delayed neutrons range from simple problems that can be solved with the point reactor kinetics equations to complex problems that can only be solved with large codes that couple fluid calculations with the neutron dynamics. Reactor safety codes, such as SIMMER, model transients of the entire reactor core using coupled space-time neutronics and comprehensive thermal-fluid dynamics. Nondestructive delayed-neutron assay instruments are designed and modeled using a three-dimensional continuous-energy Monte Carlo code. Calculations on high-burnup spent fuels and other materials that contain a mix of uranium and plutonium isotopes require accurate and complete information on the delayed-neutron periods, yields, and energy spectra. A continuing need exists for delayed-neutron parameters for all the fissioning isotopes.

  9. 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.

  10. 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.

  11. Current status of a time-of-flight single crystal neutron diffractometer SENJU at J-PARC

    NASA Astrophysics Data System (ADS)

    Tamura, I.; Oikawa, K.; Kawasaki, T.; Ohhara, T.; Kaneko, K.; Kiyanagi, R.; Kimura, H.; Takahashi, M.; Kiyotani, T.; Arai, M.; Noda, Y.; Ohshima, K.

    2012-02-01

    SENJU is a state-of-the-art single crystal time-of-flight Laue diffractometer in Materials and Life Science Experimental Facility at Japan Proton Accelerator Research Complex (J-PARC). The diffractometer is designed for precise crystal and magnetic structure analyses under multiple extreme conditions, such as low temperature, high-pressure, high-magnetic field. Measurements using small sample less than 1.0 mm3 will be also realized, which allows us to study wide variety of materials. SENJU is using a poisoned decoupled moderator to obtain peak profiles of Bragg reflection, and intensity distributions of superlattice reflections and diffuse scatterings with good accuracy. At the beginning, the diffractometer will have 31 two-dimensional scintillator detectors to cover wide area of reciprocal lattice space by a single measurement. The instrument is currently under construction and is scheduled to start on-beam commissioning in February 2012.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. A Compact Neutron Source for Boron Neutron Capture Therapy

    NASA Astrophysics Data System (ADS)

    Golubev, S. V.; Izotov, I. V.; Razin, S. V.; Sidorov, A. V.; Skalyga, V. A.

    2017-01-01

    We propose a neutron generator scheme based on a high-current ion source with electron cyclotron resonance plasma heating by high-power millimeter-wave gyrotron radiation. The most promising application of this neutron generator is a medical one, namely, boron neutron capture therapy of oncological diseases. A possibility for using a multi-aperture extraction system for high-current ion beam generation to increase the total current is studied. It is shown that the parameters of the plasma flow leaving a magnetic trap permit the effective use of multi-aperture systems without a significant loss in the ion beam current density. Thus, the use of multi-aperture systems in the ion source of a neutron generator can significantly increase the total neutron yield.

  17. Neutron Radiography

    NASA Astrophysics Data System (ADS)

    Heller, A. K.; Brenizer, J. S.

    Neutron radiography and its related two-dimensional (2D) neutron imaging techniques have been established as invaluable nondestructive inspection methods and quantitative measurement tools. They have been used in a wide variety of applications ranging from inspection of aircraft engine turbine blades to study of two-phase fluid flow in operating proton exchange membrane fuel cells. Neutron radiography is similar to X-ray radiography in that the method produces a 2D attenuation map of neutron radiation that has penetrated the object being examined. However, the images produced differ and are often complementary due to the differences between X-ray and neutron interaction mechanisms. The uses and types of 2D neutron imaging have expanded over the past 15 years as a result of advances in imaging technology and improvements in neutron generators/sources and computers. Still, high-intensity sources such as those from reactors and spallation neutron sources, together with conventional film radiography, remain the mainstay of high-resolution, large field-of-view neutron imaging. This chapter presents a summary of the history, methods, and related variations of neutron radiography techniques.

  18. Effective neutron targets

    SciTech Connect

    Gao, H.

    1997-07-01

    Because of the lack of a free neutron target, deuterium targets have been used extensively in studying the neutron structure. The unique spin structure of the {sup 3}He ground state wave function and the recent developments in laser technologies made polarized {sup 3}He targets widely used in many experiments from neutron electromagnetic form factor studies to nucleon spin structure function measurements at all major electron accelerator facilities. In this talk, the current status of the polarized {sup 3}He targets will be reviewed. The author will focus on neutron electromagnetic form factor studies using polarized {sup 3}He targets. The polarized nucleon spin structure function measurements using polarized {sup 3}He targets will also be discussed.

  19. Hybrid superconducting neutron detectors

    SciTech Connect

    Merlo, V.; Lucci, M.; Ottaviani, I.; Salvato, M.; Cirillo, M.; Scherillo, A.; Celentano, G.; Pietropaolo, A.

    2015-03-16

    A neutron detection concept is presented that is based on superconductive niobium (Nb) strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear reaction, {sup 10}B + n → α + {sup 7}Li, with α and Li ions generating a hot spot on the current-biased Nb strip which in turn induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T = 8 K and current-biased below the critical current I{sub c}, are driven into the normal state upon thermal neutron irradiation. As a result of the transition, voltage pulses in excess of 40 mV are measured while the bias current can be properly modulated to bring the strip back to the superconducting state, thus resetting the detector. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed.

  20. Hybrid superconducting neutron detectors

    NASA Astrophysics Data System (ADS)

    Merlo, V.; Salvato, M.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Scherillo, A.; Celentano, G.; Pietropaolo, A.

    2015-03-01

    A neutron detection concept is presented that is based on superconductive niobium (Nb) strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear reaction, 10B + n → α + 7Li, with α and Li ions generating a hot spot on the current-biased Nb strip which in turn induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T = 8 K and current-biased below the critical current Ic, are driven into the normal state upon thermal neutron irradiation. As a result of the transition, voltage pulses in excess of 40 mV are measured while the bias current can be properly modulated to bring the strip back to the superconducting state, thus resetting the detector. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed.

  1. 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.

  2. Neutron Stars

    NASA Technical Reports Server (NTRS)

    Cottam, J.

    2007-01-01

    Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

  3. Plutonium Immobilization Project Baseline Formulation

    SciTech Connect

    Ebbinghaus, B.

    1999-02-01

    A key milestone for the Immobilization Project (AOP Milestone 3.2a) in Fiscal Year 1998 (FY98) is the definition of the baseline composition or formulation for the plutonium ceramic form. The baseline formulation for the plutonium ceramic product must be finalized before the repository- and plant-related process specifications can be determined. The baseline formulation that is currently specified is given in Table 1.1. In addition to the baseline formulation specification, this report provides specifications for two alternative formulations, related compositional specifications (e.g., precursor compositions and mixing recipes), and other preliminary form and process specifications that are linked to the baseline formulation. The preliminary specifications, when finalized, are not expected to vary tremendously from the preliminary values given.

  4. Magnetic Fields of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Konar, Sushan

    2017-09-01

    This article briefly reviews our current understanding of the evolution of magnetic fields in neutron stars, which basically defines the evolutionary pathways between different observational classes of neutron stars. The emphasis here is on the evolution in binary systems and the newly emergent classes of millisecond pulsars.

  5. Neutron diffraction studies of bacteriorhodopsin

    SciTech Connect

    Trewhella, J.; Popot, J.L.; Engelman, D.M.; Zaccai, G.

    1985-01-01

    Neutron diffraction studies of bacteriorhodopsin have utilized the entire range of deuterium labeling techniques that are commonly used in biological neutron scattering experiments. We will review the work published in this area and report on current projects. 10 refs., 1 fig.

  6. 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.

  7. Theory of cooling neutron stars versus observations

    SciTech Connect

    Yakovlev, D. G.; Gnedin, O. Y.; Kaminker, A. D.; Potekhin, A. Y.

    2008-02-27

    We review current state of neutron star cooling theory and discuss the prospects to constrain the equation of state, neutrino emission and superfluid properties of neutron star cores by comparing the cooling theory with observations of thermal radiation from isolated neutron stars.

  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. 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.

  10. Gravitational Waves from Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kokkotas, Konstantinos

    2016-03-01

    Neutron stars are the densest objects in the present Universe, attaining physical conditions of matter that cannot be replicated on Earth. These unique and irreproducible laboratories allow us to study physics in some of its most extreme regimes. More importantly, however, neutron stars allow us to formulate a number of fundamental questions that explore, in an intricate manner, the boundaries of our understanding of physics and of the Universe. The multifaceted nature of neutron stars involves a delicate interplay among astrophysics, gravitational physics, and nuclear physics. The research in the physics and astrophysics of neutron stars is expected to flourish and thrive in the next decade. The imminent direct detection of gravitational waves will turn gravitational physics into an observational science, and will provide us with a unique opportunity to make major breakthroughs in gravitational physics, in particle and high-energy astrophysics. These waves, which represent a basic prediction of Einstein's theory of general relativity but have yet to be detected directly, are produced in copious amounts, for instance, by tight binary neutron star and black hole systems, supernovae explosions, non-axisymmetric or unstable spinning neutron stars. The focus of the talk will be on the neutron star instabilities induced by rotation and the magnetic field. The conditions for the onset of these instabilities and their efficiency in gravitational waves will be presented. Finally, the dependence of the results and their impact on astrophysics and especially nuclear physics will be discussed.

  11. 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.

  12. 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.

  13. Neutron irradiation effects on plasma facing materials

    NASA Astrophysics Data System (ADS)

    Barabash, V.; Federici, G.; Rödig, M.; Snead, L. L.; Wu, C. H.

    2000-12-01

    This paper reviews the effects of neutron irradiation on thermal and mechanical properties and bulk tritium retention of armour materials (beryllium, tungsten and carbon). For each material, the main properties affected by neutron irradiation are described and the specific tests of neutron irradiated armour materials under thermal shock and disruption conditions are summarized. Based on current knowledge, the expected thermal and structural performance of neutron irradiated armour materials in the ITER plasma facing components are analysed.

  14. Low dose neutron late effects: Cataractogenesis

    SciTech Connect

    Worgul, B.V.

    1991-12-01

    The work is formulated to resolve the uncertainty regarding the relative biological effectiveness (RBE) of low dose neutron radiation. The study exploits the fact that cataractogenesis is sensitive to the inverse dose-rate effect as has been observed with heavy ions and was an endpoint considered in the follow-up of the A-bomb survivors. The neutron radiations were initiated at the Radiological Research Accelerator facility (RARAF) of the Nevis Laboratory of Columbia University. Four week old ({plus minus} 1 day) rats were divided into eight dose groups each receiving single or fractionated total doses of 0.2, 1.0, 5.0 and 25.0 cGy of monoenergetic 435 KeV neutrons. Special restraining jigs insured that the eye, at the midpoint of the lens, received the appropriate energy and dose with a relative error of {plus minus}5%. The fractionation regimen consisted of four exposures, each administered at three hour ({plus minus}) intervals. The neutron irradiated groups are being compared to rats irradiated with 250kVp X-rays in doses ranging from 0.5 to 7 Gy. The animals are being examined on a biweekly basis utilizing conventional slit-lamp biomicroscopy and the Scheimpflug Slit Lamp Imaging System (Zeiss). The follows-ups, entering their second year, will continue throughout the life-span of the animals. This is essential inasmuch as given the extremely low doses which are being utilized clinically detectable opacities were not anticipated until a significant fraction of the life span has lapsed. Current data support this contention. At this juncture cataracts in the irradiated groups are beginning to exceed control levels.

  15. Compact neutron generator development at LBNL

    SciTech Connect

    Reijonen, J.; English, G.; Firestone, R.; Giquel, F.; King, M.; Leung, K-N.; Sun, M.

    2003-12-31

    A wide variety of applications ranging from medical (BNCT, Boron Neutron Capture Therapy) and basic science (neutron imaging, material studies) to homeland security (explosive detection and nuclear material non-proliferation) are in need of compact, high flux neutron generators. The Plasma and Ion Source Technology Group in the Lawrence Berkeley National Laboratory is developing various neutron generators for these applications. These neutron generators employed either the D-D or the D-T fusion reaction for the neutron production. The deuterium or deuterium-tritium gas mixture is ionized in an RF-driven plasma source. The ions are then accelerated to {approx}100 keV energy using high current, high voltage DC-power supply to a target where the 2.45 MeV (for D-D reaction) or 14 MeV (for the D-T reaction) neutrons are generated. The development of two different types of neutron tubes are being discussed in this presentation, namely compact, pulsed operation neutron generators and cw, high yield neutron generators. These generators are currently operating at D-D neutron yields of 108 n/s and 109 n/s respectively. A facility, incorporating the larger neutron generator, has been constructed for Prompt Gamma Activation Analysis (PGAA) and Neutron Activation Analysis (NAA) measurements.

  16. Life and Death of a Free Neutron

    NASA Astrophysics Data System (ADS)

    Fomin, Nadia

    2016-09-01

    Modern neutron sources provide extraordinary opportunities to study a wide variety of physics topics, including the physical system of the neutron itself. One of the processes under the microscope, neutron beta decay, is an archetype for all semi-leptonic charged-current weak processes. Precise measurements of the correlation parameters in neutron beta decay as well as the neutron lifetime itself are required for tests of the Standard Model and for searches of new physics. The state of the field will be presented and a program of current and future experiments and potential impacts explored.

  17. Superconducting thermal neutron detectors

    NASA Astrophysics Data System (ADS)

    Merlo, V.; Pietropaolo, A.; Celentano, G.; Cirillo, M.; Lucci, M.; Ottaviani, I.; Salvato, M.; Scherillo, A.; Schooneveld, E. M.; Vannozzi, A.

    2016-09-01

    A neutron detection concept is presented that is based on superconductive niobium nitride (NbN) strips coated by a boron (B) layer. The working principle is well described by a hot spot mechanism: upon the occurrence of the nuclear reactions n + 10B → α + 7Li + 2.8 MeV, the energy released by the secondary particles into the strip induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection principle has been experimentally assessed and verified by irradiating the samples with a pulsed neutron beam at the ISIS spallation neutron source (UK). It is found that the boron coated superconducting strips, kept at a temperature T below 11K and current-biased below the critical current IC, are driven into the normal state upon thermal neutron irradiation. Measurements on the counting rate of the device are presented and the basic physical features of the detector are discussed and compared to those of a borated Nb superconducting strip.

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

    PubMed

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

    2011-10-01

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

  19. Fast-neutron spectrometer developments

    NASA Technical Reports Server (NTRS)

    Moler, R. B.; Zagotta, W. E.; Baker, S. I.

    1973-01-01

    Li6 sandwich-type neutron spectrometer is equipped with proportional counter for particle identification. System uses current-sensitive preamplifiers to minimize pile-up of gamma-ray and particle pulses.

  20. 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.

  1. 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.

  2. Neutron star structure from QCD

    NASA Astrophysics Data System (ADS)

    Fraga, Eduardo S.; Kurkela, Aleksi; Vuorinen, Aleksi

    2016-03-01

    In this review article, we argue that our current understanding of the thermodynamic properties of cold QCD matter, originating from first principles calculations at high and low densities, can be used to efficiently constrain the macroscopic properties of neutron stars. In particular, we demonstrate that combining state-of-the-art results from Chiral Effective Theory and perturbative QCD with the current bounds on neutron star masses, the Equation of State of neutron star matter can be obtained to an accuracy better than 30% at all densities.

  3. Saltcrete formulation

    SciTech Connect

    Semones, G.B.; Connell, J.M.; Jorgensen, S.C.

    1994-09-28

    The information gathered since the first report shows that the currently generated waste and most of the waste in inventory has low concentrations of hazardous chemicals and is certifiable for disposable. This is based on preliminary analyses. Sampling and analysis for the purpose of gathering the legally defensible data required for certification and permanent disposal is in progress. The main technical issue is the expansion of the waste form. Some of the cemented waste expands and damages the containers. According to a petrology study, the expansion is caused by the formation of darapskite, a nitrate-sulfate salt. Darapskite occurs when there is high porosity causing microfractures and waste form expansion.

  4. NEUTRONIC REACTORS

    DOEpatents

    Wigner, E.P.

    1960-11-22

    A nuclear reactor is described wherein horizontal rods of thermal- neutron-fissionable material are disposed in a body of heavy water and extend through and are supported by spaced parallel walls of graphite.

  5. 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/.

  6. Neutron reflectivity

    NASA Astrophysics Data System (ADS)

    Cousin, Fabrice; Menelle, Alain

    2015-10-01

    The specular neutron reflectivity is a technique enabling the measurement of neutron scattering length density profile perpendicular to the plane of a surface or an interface, and thereby the profile of chemical composition. The characteristic sizes that are probed range from around 5 Å up 5000 Å. It is a scattering technique that averages information on the entire surface and it is therefore not possible to obtain information within the plane of the interface. The specific properties of neutrons (possibility of tuning the contrast by isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons) makes it particularly interesting in the fields of soft matter, biophysics and magnetic thin films. This course is a basic introduction to the technique and does not address the magnetic reflectivity. It is composed of three parts describing respectively its principle and its formalism, the experimental aspects of the method (spectrometers, samples) and two examples related to the materials for energy.

  7. 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)

  8. 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)

  9. Therapy of infections in mice irradiated in mixed neutron/photon fields and inflicted with wound trauma: A review of current work. (Reannouncement with new availability information)

    SciTech Connect

    Ledney, G.D.; Madonna, G.S.; Elliott, T.B.; Moore, M.M.; Jackson, W.E.

    1991-12-31

    When host antimicrobial defenses are severely compromised by radiation or trauma in conjunction with radiation, death from sepsis results. To evaluate therapies for sepsis in radiation casualties, the authors developed models of acquired and induced bacterial infections in irradiated and irradiated-wounded mice. Animals were exposed to either a mixed radiation field of equal proportions of neutrons and gamma rays (n/gamma = 1) from a TRIGA reactor or pure gamma rays from 60 (Co sources). Skin wounds (15% of total body surface area) were inflicted under methoxyflurane anesthesia 1 h after irradiation. In all mice, wounding after irradiation decreased resistance to infection. Treatments with the immunomodulator synthetic trehalose dicorynomycolate (S-TDCM) before or after mixed neutron-gamma irradiation or gamma irradiation increased survival. Therapy with S-TDCM for mice irradiated with either a mixed field or gamma rays increased resistance to Klebsiella pneumoniae-induced infections.

  10. Using instrumental neutron activation analysis for geochemical analyses of terrestrial impact structures: current analytical procedures at the university of vienna geochemistry activation analysis laboratory.

    PubMed

    Mader, Dieter; Koeberl, Christian

    2009-12-01

    The Instrumental Neutron Activation Analysis Gamma Spectroscopy Laboratory at the Department of Lithospheric Research, University of Vienna, has been upgraded in the year 2006. This paper describes the sample preparation, new instrumentation and data evaluation for hundreds of rock samples of two terrestrial impact structures. The measurement and data evaluation are done by using Genie 2000 and a custom-made batch software for the used analysis sequences.

  11. 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.

  12. 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.

  13. 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.

  14. Grand unification of neutron stars.

    PubMed

    Kaspi, Victoria M

    2010-04-20

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical "grand unification" of this wealth of observational phenomena, and comment on possibilities for Chandra's next decade in this field.

  15. Grand unification of neutron stars

    PubMed Central

    Kaspi, Victoria M.

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

  16. Iterative Reconstruction of Coded Source Neutron Radiographs

    SciTech Connect

    Santos-Villalobos, Hector J; Bingham, Philip R; Gregor, Jens

    2012-01-01

    Use of a coded source facilitates high-resolution neutron imaging but requires that the radiographic data be deconvolved. In this paper, we compare direct deconvolution with two different iterative algorithms, namely, one based on direct deconvolution embedded in an MLE-like framework and one based on a geometric model of the neutron beam and a least squares formulation of the inverse imaging problem.

  17. Liposomal formulations for inhalation.

    PubMed

    Cipolla, David; Gonda, Igor; Chan, Hak-Kim

    2013-08-01

    No marketed inhaled products currently use sustained release formulations such as liposomes to enhance drug disposition in the lung, but that may soon change. This review focuses on the interaction between liposomal formulations and the inhalation technology used to deliver them as aerosols. There have been a number of dated reviews evaluating nebulization of liposomes. While the information they shared is still accurate, this paper incorporates data from more recent publications to review the factors that affect aerosol performance. Recent reviews have comprehensively covered the development of dry powder liposomes for aerosolization and only the key aspects of those technologies will be summarized. There are now at least two inhaled liposomal products in late-stage clinical development: ARIKACE(®) (Insmed, NJ, USA), a liposomal amikacin, and Pulmaquin™ (Aradigm Corp., CA, USA), a liposomal ciprofloxacin, both of which treat a variety of patient populations with lung infections. This review also highlights the safety of inhaled liposomes and summarizes the clinical experience with liposomal formulations for pulmonary application.

  18. The Fate of Merging Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-08-01

    state. They then combined this information with Monte Carlo simulations based on the mass distribution of neutron-star binaries in our galaxy. From these simulations, Piro and collaborators could predict the distribution of fates expected for merging neutron-star binaries, given different equations of state.The authors found that the fate of the merger could vary greatly depending on the equation of state you assume. Intriguingly, all equations of state resulted in a surprisingly high fraction of systems that merged to form a neutron star or a supramassive neutron star in fact, four out of the five equations of state predicted that 80100% of systems would result in a neutron star or a supermassive neutron star.Lessons from ObservationsThe frequency bands covered by various current and planned gravitational wave observatories. Advanced LIGO has the right frequency coverage to be able to explore a neutron-star remnant if the signal is loud enough. [Christopher Moore, Robert Cole and Christopher Berry]These results have important implications for our future observations. The high predicted fraction of neutron stars resulting from these mergers tells us that its especially important for gravitational-wave observatories to probe 14 kHz emission. This frequency range will enable us to study the post-merger neutron-star or supramassive-neutron-star remnants.Even if we cant observe the remnants behavior after it forms, we can still compare the distribution of remnants that we observe in the future to the predictions made by Piro and collaborators. This will potentially allow us to constrain the neutron-star equation of state, revealing the physics of neutron-star interiors even without direct observations.CitationAnthony L. Piro et al 2017 ApJL 844 L19. doi:10.3847/2041-8213/aa7f2f

  19. 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.

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

    SciTech Connect

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

    2015-11-15

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

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

    PubMed

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

    2015-11-01

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

  2. 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.

  3. Why organic resources and current fertilizer formulations in Southern Africa cannot sustain maize productivity: Evidence from a long-term experiment in Zimbabwe

    PubMed Central

    Mtangadura, Tongai J.

    2017-01-01

    Sustainability of maize-based cropping systems is a major challenge for southern Africa, yet the demand for maize as staple food and animal feed in the region continues to increase. A study was conducted on a sandy clay loam (220 g clay kg-1 soil) at Domboshawa in Zimbabwe to investigate the long-term effects of organic resource quality and application rate, and nitrogen (N) fertilization on soil chemical properties and maize (Zea mays L.) productivity. Crotalaria juncea (high quality), Calliandra calothyrsus (medium quality), cattle manure (variable quality), maize stover and Pinus patula sawdust (both low quality) were incorporated into soil at 4.0 t C ha-1 (high rate) and 1.2 t C ha-1 (low rate) at the start of each cropping season for nine consecutive years. At both high and low application rates, each of the five organic resources was applied in combination with or without mineral nitrogen (N) fertilizer at 120 kg N ha-1. The nine-year period saw maize grain yields declining by 22% to 84% across treatments despite increases in soil organic carbon, total N and available P from 6% to 80%. Crotalaria, Calliandra and manure led to a less steep yield decline. Exchangeable calcium (Ca), magnesium (Mg) and potassium (K), and soil pH explained much of the variation in yield patterns observed under the different organic resource applications. Maize grain yield was positively correlated with exchangeable Ca (r = 0.51), Mg (r = 0.62) and K (r = 0.53), and soil pH (r = 0.49), but negatively correlated with other soil properties over the 9-year period. We concluded that declining soil exchangeable basic cations were the underlying causes of decreasing maize productivity, and was aggravated by use of low rates of organic resource inputs, particularly with N fertilization. Current nutrient management and fertilizer recommendations that emphasize inorganic N, P and K significantly undervalue the role played by organic resources in sustainability of maize cropping systems in

  4. Advances in personnel neutron dosimetry

    SciTech Connect

    Vallario, E.; Faust, L.

    1983-07-01

    A program to assess current personnel neutron dosimeter capabilities and to develop improved personnel neutron dosimeters examines the two types of passive dosimeters in use at DOE facilities: NTA film and TLD-albedo dosimeters. Two new neutron dosimeters under development to overcome some of their problems are combination/track-etch dosimeters and pocket rem-meters. The DOE program is investigating new materials and improved manufacturing processes using the CR-39 polymer and that is nearly free of surface defects. 1 figure.

  5. NEUTRON SOURCE

    DOEpatents

    Foster, J.S. Jr.

    1960-04-19

    A compact electronic device capable of providing short time high density outputs of neutrons is described. The device of the invention includes an evacuated vacuum housing adapted to be supplied with a deuterium, tritium, or other atmosphere and means for establishing an electrical discharge along a path through the gas. An energized solenoid is arranged to constrain the ionized gas (plasma) along the path. An anode bearing adsorbed or adherent target material is arranged to enclose the constrained plasma. To produce neutrons a high voltage is applied from appropriate supply means between the plasma and anode to accelerate ions from the plasma to impinge upcn the target material, e.g., comprising deuterium.

  6. 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.

  7. 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.

  8. The Fundamental Neutron Physics Facilities at NIST.

    PubMed

    Nico, J S; Arif, M; Dewey, M S; Gentile, T R; Gilliam, D M; Huffman, P R; Jacobson, D L; Thompson, A K

    2005-01-01

    The program in fundamental neutron physics at the National Institute of Standards and Technology (NIST) began nearly two decades ago. The Neutron Interactions and Dosimetry Group currently maintains four neutron beam lines dedicated to studies of fundamental neutron interactions. The neutrons are provided by the NIST Center for Neutron Research, a national user facility for studies that include condensed matter physics, materials science, nuclear chemistry, and biological science. The beam lines for fundamental physics experiments include a high-intensity polychromatic beam, a 0.496 nm monochromatic beam, a 0.89 nm monochromatic beam, and a neutron interferometer and optics facility. This paper discusses some of the parameters of the beam lines along with brief presentations of some of the experiments performed at the facilities.

  9. A polyethylene-B4C based concrete for enhanced neutron shielding at neutron research facilities

    NASA Astrophysics Data System (ADS)

    DiJulio, D. D.; Cooper-Jensen, C. P.; Perrey, H.; Fissum, K.; Rofors, E.; Scherzinger, J.; Bentley, P. M.

    2017-07-01

    We present the development of a specialized concrete for neutron shielding at neutron research facilities, based on the addition of hydrogen atoms in the form of polyethylene and also B4C for enhancing the neutron capture properties of the concrete. We show information on the mechanical properties of the concrete and the neutronics, in particular its relevance to modern spallation neutron sources, such as the European Spallation Source (ESS), currently under construction in Lund, Sweden. The new concrete exhibits a 15% lower mass density, a compressible strength of 50% relative to a standard concrete and a significant increase in performance of shielding against MeV neutrons and lower energies. The concrete could find application at the ESS in for example common shielding components, individual beamline shielding and instrument caves. Initial neutronic tests of the concrete, carried out at Lund University, have also verified the performance in the MeV neutron energy range and the results are presented.

  10. The accelerator neutron source for boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Kasatov, D.; Koshkarev, A.; Kuznetsov, A.; Makarov, A.; Ostreinov, Yu; Shchudlo, I.; Sorokin, I.; Sycheva, T.; Taskaev, S.; Zaidi, L.

    2016-11-01

    The accelerator based epithermal neutron source for Boron Neutron Capture Therapy (BNCT) is proposed, created and used in the Budker Institute of Nuclear Physics. In 2014, with the support of the Russian Science Foundation created the BNCT laboratory for the purpose to the end of 2016 get the neutron flux, suitable for BNCT. For getting 3 mA 2.3 MeV proton beam, was created a new type accelerator - tandem accelerator with vacuum isolation. On this moment, we have a stationary proton beam with 2.3 MeV and current 1.75 mA. Generation of neutrons is carried out by dropping proton beam on to lithium target as a result of threshold reaction 7Li(p,n)7Be. Established facility is a unique scientific installation. It provides a generating of neutron flux, including a monochromatic energy neutrons, gamma radiation, alpha-particles and positrons, and may be used by other research groups for carrying out scientific researches. The article describes an accelerator neutron source, presents and discusses the result of experiments and declares future plans.

  11. a Portable Pulsed Neutron Generator

    NASA Astrophysics Data System (ADS)

    Skoulakis, A.; Androulakis, G. C.; Clark, E. L.; Hassan, S. M.; Lee, P.; Chatzakis, J.; Bakarezos, M.; Dimitriou, V.; Petridis, C.; Papadogiannis, N. A.; Tatarakis, M.

    2014-02-01

    The design and construction of a pulsed plasma focus device to be used as a portable neutron source for material analysis such as explosive detection using gamma spectroscopy is presented. The device is capable of operating at a repetitive rate of a few Hz. When deuterium gas is used, up to 105 neutrons per shot are expected to be produced with a temporal pulse width of a few tens of nanoseconds. The pulsed operation of the device and its portable size are its main advantage in comparison with the existing continuous neutron sources. Parts of the device include the electrical charging unit, the capacitor bank, the spark switch (spark gap), the trigger unit and the vacuum-fuel chamber / anode-cathode. Numerical simulations are used for the simulation of the electrical characteristics of the device including the scaling of the capacitor bank energies with total current, the pinch current, and the scaling of neutron yields with energies and currents. The MCNPX code is used to simulate the moderation of the produced neutrons in a simplified geometry and subsequently, the interaction of thermal neutrons with a test target and the corresponding prompt γ-ray generation.

  12. 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.

  13. 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.

  14. Methods for absorbing neutrons

    DOEpatents

    Guillen, Donna P [Idaho Falls, ID; Longhurst, Glen R [Idaho Falls, ID; Porter, Douglas L [Idaho Falls, ID; Parry, James R [Idaho Falls, ID

    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.

  15. Neutron star evolutionary sequences

    NASA Technical Reports Server (NTRS)

    Richardson, M. B.; Van Horn, H. M.; Ratcliff, K. F.; Malone, R. C.

    1982-01-01

    Detailed numerical calculations which are solutions of the full set of general relativistic equations describing the evolution of a spherical star are presented, for the case of the evolution of neutron stars that are cooling over the central temperatures range of 10 to the 10th to 10 to the 7th K. The effects of nucleon superfluidity in the inner crust and core are included, and models are constructed with and without a pion condensate at high densities. It is found that the localized neutrino cooling which dominates the early evolution of neutron stars is so rapid that heat transport within the star cannot keep pace, and temperature distribution is not isothermal. The residual contraction of the neutron star during the early cooling phase contributes little to the heat budget of the star, and most of the gravitational energy released raises the Fermi energy of the degenerate nucleons. It is concluded that since calculations with and without pion condensate are consistent with the upper limits of current observations, these are not sufficient in distinguishing between the various models of neutron star cooling.

  16. Surface Mounted Neutron Generators

    NASA Astrophysics Data System (ADS)

    Elizondo-Decanini, Juan M.

    2012-10-01

    A deuterium-tritium (DT) base reaction pulsed neutron generator packaged in a flat computer chip shape of 1.54 cm (0.600 in) wide by 3.175 cm (1.25 in) length and 0.3 cm (0.120 in) thick has been successfully demonstrated to produce 14 MeV neutrons at a rate of 10^9 neutrons per second. The neutron generator is based on a deuterium ion beam accelerated to impact a tritium loaded target. The accelerating voltage is in the 15 to 20 kV in a 3 mm (0.120 in) gap, the ion beam is shaped by using a lens design to produce a flat ion beam that conforms to the flat rectangular target. The ion source is a simple surface mounted deuterium filled titanium film with a fused gap that operates at a current-voltage design to release the deuterium during a pulse length of about 1 μs. We present the general description of the working prototypes, which we have labeled the ``NEUTRISTOR.''[4pt] Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration. Work funded by the LDRD office.

  17. 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)

  18. 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)

  19. 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.

  20. 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.

  1. Neutronics calculation of RTP core

    NASA Astrophysics Data System (ADS)

    Rabir, Mohamad Hairie B.; Zin, Muhammad Rawi B. Mohamed; Karim, Julia Bt. Abdul; Bayar, Abi Muttaqin B. Jalal; Usang, Mark Dennis Anak; Mustafa, Muhammad Khairul Ariff B.; Hamzah, Na'im Syauqi B.; Said, Norfarizan Bt. Mohd; Jalil, Muhammad Husamuddin B.

    2017-01-01

    Reactor calculation and simulation are significantly important to ensure safety and better utilization of a research reactor. The Malaysian's PUSPATI TRIGA Reactor (RTP) achieved initial criticality on June 28, 1982. The reactor is designed to effectively implement the various fields of basic nuclear research, manpower training, and production of radioisotopes. Since early 90s, neutronics modelling were used as part of its routine in-core fuel management activities. The are several computer codes have been used in RTP since then, based on 1D neutron diffusion, 2D neutron diffusion and 3D Monte Carlo neutron transport method. This paper describes current progress and overview on neutronics modelling development in RTP. Several important parameters were analysed such as keff, reactivity, neutron flux, power distribution and fission product build-up for the latest core configuration. The developed core neutronics model was validated by means of comparison with experimental and measurement data. Along with the RTP core model, the calculation procedure also developed to establish better prediction capability of RTP's behaviour.

  2. Neutron polycapillary optics: back to future

    NASA Astrophysics Data System (ADS)

    Ioffe, Alexander

    2005-08-01

    At the sunrise of the Kumakhov optics, the latter was enormously attractive for neutron scientists eager to take advantage from focused neutron beams. However, in spite of this initial enthusiasm, rear neutron applications of polycapillary optics are mostly limited either to feasibility studies or to non-scattering techniques. The reason for such a drawback is a serious degradation in the momentum resolution of neutron scattering methods caused by increased divergence of focused beams. However, limited brightness of present day neutron sources (both existing and coming) requires rethinking the current situation. Neutron lenses are successfully tested for low Q-resolution applications providing an enormous increase of neutron flux at small samples. Moreover, some recent developments in the field of neutron instrumentation allow us to overcome the resolution problem by decoupling the angular resolution and the incident beam divergence thus opening the opportunity for the use of focusing neutron optics in some high Q-resolution application. Further advances in technology required to improve the performance of neutron polycapillary optics, also in combination with modem methods of polarization of neutron beams, are discussed.

  3. Alternative Neutron Detection Testing Summary

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Erikson, Luke E.; Kernan, Warnick J.; Lintereur, Azaree T.; Siciliano, Edward R.; Stromswold, David C.; Woodring, Mitchell L.

    2010-04-08

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. Most currently deployed radiation portal monitors (RPMs) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large area neutron detector. This type of neutron detector is used in the TSA and other RPMs installed in international locations and in the Ludlum and Science Applications International Corporation RPMs deployed primarily for domestic applications. There is a declining supply of 3He in the world and, thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated wavelength-shifting plastic fibers. Reported here is a summary of the testing carried out at Pacific Northwest National Laboratory on these technologies to date, as well as measurements on 3He tubes at various pressures. Details on these measurements are available in the referenced reports. Sponsors of these tests include the Department of Energy (DOE), Department of Homeland Security (DHS), and the Department of Defense (DoD), as well as internal Pacific Northwest National Laboratory funds.

  4. Analysis of Cadmium Based Neutron Detector Configurations

    NASA Astrophysics Data System (ADS)

    James, Brian; Rees, Lawrence; Czirr, J. Bart

    2012-10-01

    Due to national security concerns pertaining to the smuggling of special nuclear materials and a small supply of He-3 for use in neutron detectors, there is currently a need for a new kind of neutron detector. Using Monte Carlo techniques I have studied the neutron capture efficiency of an array of cadmium wedge detectors in the presence of a californium source. By using varying numbers of wedges and comparing their capture ratios we will be better able to design future detectors.

  5. Neutron Reflectivity and Grazing Angle Diffraction

    PubMed Central

    Ankner, J. F.; Majkrzak, C. F.; Satija, S. K.

    1993-01-01

    Over the last 10 years, neutron reflectivity has emerged as a powerful technique for the investigation of surface and interfacial phenomena in many different fields. In this paper, a short review of some of the work on neutron reflectivity and grazing-angle diffraction as well as a description of the current and planned neutron rcflectometers at NIST is presented. Specific examples of the characterization of magnetic, superconducting, and polymeric surfaces and interfaces are included. PMID:28053457

  6. Neutron multiplicity analysis tool

    SciTech Connect

    Stewart, Scott L

    2010-01-01

    I describe the capabilities of the EXCOM (EXcel based COincidence and Multiplicity) calculation tool which is used to analyze experimental data or simulated neutron multiplicity data. The input to the program is the count-rate data (including the multiplicity distribution) for a measurement, the isotopic composition of the sample and relevant dates. The program carries out deadtime correction and background subtraction and then performs a number of analyses. These are: passive calibration curve, known alpha and multiplicity analysis. The latter is done with both the point model and with the weighted point model. In the current application EXCOM carries out the rapid analysis of Monte Carlo calculated quantities and allows the user to determine the magnitude of sample perturbations that lead to systematic errors. Neutron multiplicity counting is an assay method used in the analysis of plutonium for safeguards applications. It is widely used in nuclear material accountancy by international (IAEA) and national inspectors. The method uses the measurement of the correlations in a pulse train to extract information on the spontaneous fission rate in the presence of neutrons from ({alpha},n) reactions and induced fission. The measurement is relatively simple to perform and gives results very quickly ({le} 1 hour). By contrast, destructive analysis techniques are extremely costly and time consuming (several days). By improving the achievable accuracy of neutron multiplicity counting, a nondestructive analysis technique, it could be possible to reduce the use of destructive analysis measurements required in safeguards applications. The accuracy of a neutron multiplicity measurement can be affected by a number of variables such as density, isotopic composition, chemical composition and moisture in the material. In order to determine the magnitude of these effects on the measured plutonium mass a calculational tool, EXCOM, has been produced using VBA within Excel. This

  7. 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.

  8. 3He spin filter based polarized neutron capability at the NIST Center for Neutron Research

    NASA Astrophysics Data System (ADS)

    Chen, W. C.; Gentile, T. R.; Erwin, R.; Watson, S.; Ye, Q.; Krycka, K. L.; Maranville, B. B.

    2014-07-01

    A 3He neutron spin filter (NSF) program for polarized neutron scattering was launched in 2006 as part of the National Institute of Standards and Technology (NIST) Center for Neutron Research (NCNR) Expansion Initiative. The goal of the project was to enhance the NCNR polarized neutron measurement capabilities. Benefitting from more than a decade's development of spin-exchange optical pumping (SEOP) at NIST, we planned to employ SEOP based 3He neutron spin filters for the polarized neutron scattering community. These 3He NSF devices were planned for use on different classes of polarized neutron instrumentation at the NCNR, including triple-axis spectrometers (TAS), small-angle neutron scattering instruments (SANS), reflectometers, and wide-angle polarization analysis. Among them, the BT-7 thermal TAS, NG-3 SANS, and MAGIK reflectometer have already been in the user program for routine polarized beam experiments. Wide-angle polarization analysis on Multi-Axis Crystal Spectrometer (MACS) has been developed for user experiments. We describe briefly the SEOP systems dedicated for polarized beam experiments and polarizing neutron development for each instrument class. We summarize the current status and polarized neutronic performance for each instrument. We present a 3He NSF hardware and software interface to allow for synchronization of 3He polarization inversion (neutron spin flipping) and free-induction decay (FID) nuclear magnetic resonance (NMR) measurements with neutron data collection.

  9. Possible Supernova Detection with Neutron Detectors near the SNO Laboratory

    NASA Astrophysics Data System (ADS)

    Duba, C. A.; Browne, M. C.; Robertson, R. G. H.

    1998-10-01

    Before neutron detectors are installed into the heavy water at SNO to detect neutral-current interactions, they are allowed to 'cool down' underground from surface cosmic-ray activation. During this time, they will be in a position to measure neutron flux from the INCO Creighton Mine's norite rock walls. A nearby galactic supernova will increase neutron production in the norite via charged- and neutral-current interactions. The increase in the neutron flux, as well as the neutral-current detectors' sensitivity to neutron flux, will be summarized and the possible use of these proportional counters as a supernova detector will be discussed.

  10. Methods for Neutron Spectrometry

    DOE R&D Accomplishments Database

    Brockhouse, Bertram N.

    1961-01-09

    The appropriate theories and the general philosophy of methods of measurement and treatment of data neutron spectrometry are discussed. Methods of analysis of results for liquids using the Van Hove formulation, and for crystals using the Born-von Karman theory, are reviewed. The most useful of the available methods of measurement are considered to be the crystal spectrometer methods and the pulsed monoenergetic beam/time-of-flight method. Pulsed-beam spectrometers have the advantage of higher counting rates than crystal spectrometers, especially in view of the fact that simultaneous measurements in several counters at different angles of scattering are possible in pulsed-beam spectrometers. The crystal spectrometer permits several valuable new types of specialized experiments to be performed, especially energy distribution measurements at constant momentum transfer. The Chalk River triple-axis crystal-spectrometer is discussed, with reference to its use in making the specialized experiments. The Chalk River rotating crystal (pulsed-beam) spectrometer is described, and a comparison of this type instrument with other pulsed-beam spectrometers is made. A partial outline of the theory of operation of rotating-crystal spectrometers is presented. The use of quartz-crystal filters for fast neutron elimination and for order elimination is discussed. (auth)

  11. Neutron Generators for Spent Fuel Assay

    SciTech Connect

    Ludewigt, Bernhard A

    2010-12-30

    The Next Generation Safeguards Initiative (NGSI) of the U.S. DOE has initiated a multi-lab/university collaboration to quantify the plutonium (Pu) mass in, and detect the diversion of pins from, spent nuclear fuel (SNF) assemblies with non-destructive assay (NDA). The 14 NDA techniques being studied include several that require an external neutron source: Delayed Neutrons (DN), Differential Die-Away (DDA), Delayed Gammas (DG), and Lead Slowing-Down Spectroscopy (LSDS). This report provides a survey of currently available neutron sources and their underlying technology that may be suitable for NDA of SNF assemblies. The neutron sources considered here fall into two broad categories. The term 'neutron generator' is commonly used for sealed devices that operate at relatively low acceleration voltages of less than 150 kV. Systems that employ an acceleration structure to produce ion beam energies from hundreds of keV to several MeV, and that are pumped down to vacuum during operation, rather than being sealed units, are usually referred to as 'accelerator-driven neutron sources.' Currently available neutron sources and future options are evaluated within the parameter space of the neutron generator/source requirements as currently understood and summarized in section 2. Applicable neutron source technologies are described in section 3. Commercially available neutron generators and other source options that could be made available in the near future with some further development and customization are discussed in sections 4 and 5, respectively. The pros and cons of the various options and possible ways forward are discussed in section 6. Selection of the best approach must take a number of parameters into account including cost, size, lifetime, and power consumption, as well as neutron flux, neutron energy spectrum, and pulse structure that satisfy the requirements of the NDA instrument to be built.

  12. Formulation of Nematodes.

    PubMed

    Peters, Arne

    2016-01-01

    The enduring stages of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis are infective juveniles, which require a high humidity and sufficient ventilation for survival. Formulations must account for these requirements. Nematodes may be formulated inside the insects in which they reproduced or they need to be cleaned and mixed with a suitable binder to maintain humidity but allowing for gas exchange. Another method for formulation is the encapsulation in beads of Ca-alginate. Generic procedures for these formulation techniques are described.

  13. Status of the advanced neutron source. [Advanced Neutron Source Reactor

    SciTech Connect

    Hayter, J.B.

    1990-01-01

    Research reactors in the United States are becoming more and more outdated, at a time when neutron scattering is being recognized as an increasingly important technique in areas vital to the US scientific and technological future. The last US research reactor was constructed over 25 years ago, whereas new facilities have been built or are under construction in Japan, Russia and, especially, Western Europe, which now has a commanding lead in this important field. Concern over this situation in the early 1980's by a number of organizations, including the National Academy of Sciences, led to a recommendation that design work start urgently on an advanced US neutron research facility. This recommendation is realized in the Advanced Neutron Source Project. The centerpiece of the Advanced Neutron Source will be a new research reactor of unprecedented flux (>7.5 {times} 10{sup 19} m{sup {minus}2}{center dot}s{sup {minus}1}), equipped with a wide variety of state-of-the-art spectrometers and diffractometers on hot, thermal, and cold neutron beams. Very cold and ultracold neutron beams will also be provided for specialized experiments. This paper will discuss the current status of the design and the plans for scattering instrumentation. 5 refs.

  14. Neutron Lifetime Measurement Using Magnetically Trapped Ultracold Neutrons

    NASA Astrophysics Data System (ADS)

    Huffer, Craig; Huffman, P. R.; Schelhammer, K. W.; Dewey, M. S.; Huber, M. G.; Hughes, P. P.; Mumm, H. P.; Thompson, A. K.; Coakley, K.; Yue, A. T.; O'Shaughnessy, C. M.

    2017-01-01

    The neutron beta-decay lifetime is important in both nuclear astrophysics and in understanding weak interactions in the framework of the Standard Model. An experiment based at the NIST Center for Neutron Research was designed to address statistical and systematic limitations of former measurements. In our approach, a beam of 0.89 nm neutrons is incident on a superfluid 4He target within the minimum field region of an Ioffe-type magnetic trap. Some of the neutrons are subsequently downscattered by single phonons in the helium to low energies (< 100 neV) and those in the appropriate spin state become trapped. The inverse process, upscattering of UCN, is suppressed by the low phonon density in the < 300 mK helium, allowing the neutron to travel undisturbed through the helium. When the neutron decays the energetic electron produces a scintillation signal in the helium that is detected in real time using photomultiplier tubes. The current measurement is limited by larger than expected systematic corrections. We will discuss the result of the latest dataset and comment on the potential of future measurements.

  15. PLANS FOR A NEUTRON EDM EXPERIMENT AT SNS

    SciTech Connect

    ITO, TAKEYASU

    2007-01-31

    The electric dipole moment of the neutron, leptons, and atoms provide a unique window to Physics Beyond the Standard Model. They are currently developing a new neutron EDM experiment (the nEDM Experiment). This experiment, which will be run at the 8.9 {angstrom} Neutron Line at the Fundamental Neutron Physics Beamline (FNPB) at the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory, will search for the neutron EDM with a sensitivity two orders of magnitude higher than the present limit. In this paper, the motivation for the experiment, the experimental method, and the present status of the experiment are discussed.

  16. Burst Oscillations: Watching Neutron Stars Spin

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2010-01-01

    It is now almost 15 years since the first detection of rotationally modulated emission from X-ray bursting neutron stars, "burst oscillations," This phenomenon enables us to see neutron stars spin, as the X-ray burst flux asymmetrically lights up the surface. It has enabled a new way to probe the neutron star spin frequency distribution, as well as to elucidate the multidimensional nature of nuclear burning on neutron stars. I will review our current observational understanding of the phenomenon, with an eye toward highlighting some of the interesting remaining puzzles, of which there is no shortage.

  17. Gamma compensated, self powered neutron detector

    DOEpatents

    Brown, Donald P.

    1977-01-01

    An improved, self-powered, gamma compensated, neutron detector having two electrically conductive concentric cylindrical electrodes and a central rod emitter formed from a material which emits beta particles when bombarded by neutrons. The outer electrode and emitter are maintained at a common potential and the neutron representative current is furnished at the inner cylindrical electrode which serves as a collector. The two concentric cylindrical electrodes are designed to exhibit substantially equal electron emission induced by Compton scattering under neutron bombardment to supply the desired gamma compensation.

  18. Compact neutron generator developement and applications

    SciTech Connect

    Leung, Ka-Ngo; Reijonen, Jani; Gicquel, Frederic; Hahto, Sami; Lou, Tak-Pui

    2004-01-18

    The Plasma and Ion Source Technology Group at the Lawrence Berkeley National Laboratory has been engaging in the development of high yield compact neutron generators for the last ten years. Because neutrons in these generators are formed by using either D-D, T-T or D-T fusion reaction, one can produce either mono-energetic (2.4 MeV or 14 MeV) or white neutrons. All the neutron generators being developed by our group utilize 13.5 MHz RF induction discharge to produce a pure deuterium or a mixture of deuterium-tritium plasma. As a result, ion beams with high current density and almost pure atomic ions can be extracted from the plasma source. The ion beams are accelerated to {approx}100 keV and neutrons are produced when the beams impinge on a titanium target. Neutron generators with different configurations and sizes have been designed and tested at LBNL. Their applications include neutron activation analysis, oil-well logging, boron neutron capture therapy, brachytherapy, cargo and luggage screening. A novel small point neutron source has recently been developed for radiography application. The source size can be 2 mm or less, making it possible to examine objects with sharper images. The performance of these neutron generators will be described in this paper.

  19. Magneto-thermal evolution of neutron stars

    NASA Astrophysics Data System (ADS)

    Pons, J. A.; Miralles, J. A.; Geppert, U.

    2009-03-01

    Context: The presence of magnetic fields in the crust of neutron stars (NSs) causes a non-spherically symmetric temperature distribution. The strong temperature dependence of the magnetic diffusivity and thermal conductivity, together with the heat generated by magnetic dissipation, couple the magnetic and thermal evolution of NSs, which can no longer be formulated as separated one-dimensional problems. Aims: We study the mutual influence of thermal and magnetic evolution in a neutron star's crust in axial symmetry. Taking realistic microphysical inputs into account, we find the heat released by Joule effect consistent with the circulation of currents in the crust, and we incorporate its effects in 2D cooling calculations. Methods: We solve the induction equation numerically using a hybrid method (spectral in angles, but a finite-differences scheme in the radial direction), coupled to the thermal diffusion equation. To improve the boundary conditions, we also revisit the envelope stationary solutions updating the well known T_b-T_s-relations to include the effect of 2D heat transfer calculations and new microphysical inputs. Results: We present the first longterm 2D simulations of the coupled magneto-thermal evolution of neutron stars. This substantially improves previous works in which a very crude approximation in at least one of the parts (thermal or magnetic diffusion) has been adopted. Our results show that the feedback between Joule heating and magnetic diffusion is strong, resulting in a faster dissipation of the stronger fields during the first 10^5-106 years of an NS's life. As a consequence, all neutron stars born with fields over a critical value (>5 × 1013 G) reach similar field strengths (≈2-3 × 1013 G) at late times. Irrespective of the initial magnetic field strength, the temperature becomes so low after 106 years that the magnetic diffusion timescale becomes longer than the typical ages of radiopulsars, thus apparently resulting in no

  20. High energy neutron radiography

    SciTech Connect

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

    1996-06-01

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

  1. Current Research Developments at NASA Goddard Space Flight Center on the Neutron Star Interior Composition ExploreR (NICER) X-ray Concentrators

    NASA Astrophysics Data System (ADS)

    Balsamo, Erin; Okajima, T.; Gendreau, K.; Arzoumanian, Z.; Jalota, L.; Soong, Y.; Serlemitsos, P. J.

    2013-04-01

    NICER is a proposed NASA Explorer Mission of Opportunity and will study the extreme gravitational, electromagnetic, and nuclear physics of neutron stars. Observations will be performed by an X-ray timing and spectroscopy instrument on board the International Space Station (ISS) with launch scheduled for late 2016. NICER consists of grazing incident optics coupled with silicon drift detectors that will provide high throughput photon collection with relatively low background. The optical system consists of 56 X-ray optics, each of which comprise of 24 individual concentrators made from thin aluminum shells with epoxy replicated gold surface. These specialized concentrators focus incident X-rays allowing for small detectors thus increasing the signal to noise while minimizing mass and fabrication cost. The concentrators have three distinct design differences from traditional thin foil epoxy replicated imaging optics. Firstly, the concentrators use only a single reflection and therefore have degraded imaging resolution for extended sources. They also have a full shell structure to further improve the effective area to mass ratio and a curved axial profile to improve resolution and hence concentration at a short focal length. NICER is the second project using these style concentrators, the first of which was the X-ray Advanced Concepts Testbed (XACT) sounding rocket payload (expected to launch in December 2013). The fabrication of the NICER optics began in spring 2012 and were tested using a collimated X-ray beam in summer 2012. In the following months, the concentrators’ fabrication method has been improved and adapted from the method used with XACT. X-ray measurements have been made to characterize the concentrators by calculating half power diameters, off-axis performance, and effective area measurements. These have been compared to ray tracing and theoretical calculations. Here we report the performance to date with comparisons to the theoretical calculations as

  2. Neutrons scattering studies in the actinide region

    SciTech Connect

    Kegel, G.H.R.; Egan, J.J.

    1992-09-01

    During the report period were investigated the following areas: prompt fission neutron energy spectra measurements; neutron elastic and inelastic scattering from [sup 239]Pu; neutron scattering in [sup 181]Ta and [sup 197]Au; response of a [sup 235]U fission chamber near reaction thresholds; two-parameter data acquisition system; black'' neutron detector; investigation of neutron-induced defects in silicon dioxide; and multiple scattering corrections. Four Ph.D. dissertations and one M.S. thesis were completed during the report period. Publications consisted of three journal articles, four conference papers in proceedings, and eleven abstracts of presentations at scientific meetings. There are currently four Ph.D. and one M.S. candidates working on dissertations directly associated with the project. In addition, three other Ph.D. candidates are working on dissertations involving other aspects of neutron physics in this laboratory.

  3. Cold neutrons trapped in external fields.

    PubMed

    Gandolfi, S; Carlson, J; Pieper, Steven C

    2011-01-07

    The properties of inhomogeneous neutron matter are crucial to the physics of neutron-rich nuclei and the crust of neutron stars. Advances in computational techniques now allow us to accurately determine the binding energies and densities of many neutrons interacting via realistic microscopic interactions and confined in external fields. We perform calculations for different external fields and across several shells to place important constraints on inhomogeneous neutron matter, and hence the large isospin limit of the nuclear energy density functionals that are used to predict properties of heavy nuclei and neutron star crusts. We find important differences between microscopic calculations and current density functionals; in particular, the isovector gradient terms are significantly more repulsive than in traditional models, and the spin-orbit and pairing forces are comparatively weaker.

  4. Data assimilation in a coupled physical-biogeochemical model of the California Current System using an incremental lognormal 4-dimensional variational approach: Part 1-Model formulation and biological data assimilation twin experiments

    NASA Astrophysics Data System (ADS)

    Song, Hajoon; Edwards, Christopher A.; Moore, Andrew M.; Fiechter, Jerome

    2016-10-01

    A quadratic formulation for an incremental lognormal 4-dimensional variational assimilation method (incremental L4DVar) is introduced for assimilation of biogeochemical observations into a 3-dimensional ocean circulation model. L4DVar assumes that errors in the model state are lognormally rather than Gaussian distributed, and implicitly ensures that state estimates are positive definite, making this approach attractive for biogeochemical variables. The method is made practical for a realistic implementation having a large state vector through linear assumptions that render the cost function quadratic and allow application of existing minimization techniques. A simple nutrient-phytoplankton-zooplankton-detritus (NPZD) model is coupled to the Regional Ocean Modeling System (ROMS) and configured for the California Current System. Quadratic incremental L4DVar is evaluated in a twin model framework in which biological fields only are in error and compared to G4DVar which assumes Gaussian distributed errors. Five-day assimilation cycles are used and statistics from four years of model integration analyzed. The quadratic incremental L4DVar results in smaller root-mean-squared errors and better statistical agreement with reference states than G4DVar while maintaining a positive state vector. The additional computational cost and implementation effort are trivial compared to the G4DVar system, making quadratic incremental L4DVar a practical and beneficial option for realistic biogeochemical state estimation in the ocean.

  5. Neutron-neutron and neutron-photon correlations with FREYA

    NASA Astrophysics Data System (ADS)

    Vogt, R.; Randrup, J.

    2017-09-01

    For many years, the state of the art for modeling fission in radiation transport codes has involved sampling from average distributions. However, in a true fission event, the energies, momenta and multiplicities of emitted particles are correlated. The FREYA (Fission Reaction Event Yield Algorithm) code generates complete fission events. Event-by-event techniques such as those of FREYA are particularly useful because it is possible to obtain complete kinematic information on the prompt neutrons and photons emitted during the fission process. It is therefore possible to extract any desired correlation observables. We describe FREYA and compare our results with neutron-neutron, neutron-light fragment and neutron-photon correlation data.

  6. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy.

    PubMed

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-03-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 10(5) n/cm(2)/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources.

  7. Application of an ultraminiature thermal neutron monitor for irradiation field study of accelerator-based neutron capture therapy

    PubMed Central

    Ishikawa, Masayori; Tanaka, Kenichi; Endo, Satrou; Hoshi, Masaharu

    2015-01-01

    Phantom experiments to evaluate thermal neutron flux distribution were performed using the Scintillator with Optical Fiber (SOF) detector, which was developed as a thermal neutron monitor during boron neutron capture therapy (BNCT) irradiation. Compared with the gold wire activation method and Monte Carlo N-particle (MCNP) calculations, it was confirmed that the SOF detector is capable of measuring thermal neutron flux as low as 105 n/cm2/s with sufficient accuracy. The SOF detector will be useful for phantom experiments with BNCT neutron fields from low-current accelerator-based neutron sources. PMID:25589504

  8. Effects of thermal neutron irradiation on some potential excipients for colonic delivery systems.

    PubMed

    Ahrabi, S F; Sande, S A; Waaler, T; Graffner, C

    1999-04-01

    Different excipients, which are currently being studied for colon delivery systems, were examined with respect to their stability toward neutron irradiation as a potential method of radiolabeling the formulations for gamma-scintigraphic studies. Three different pectin and four different hydroxypropyl methylcellulose (HPMC) types, in addition to two types of polymethacrylate films, were exposed to 1, 2, and 3 min of thermal neutron irradiation in a flux of 1.1 x 10(13) n cm-2 s-1. The physicochemical characteristics of pectins and HPMCs and the mechanical properties of the polymethacrylate films were examined after the radioactivity of the samples had declined to background levels. Methods included ultraviolet (UV) and Fourier transform infrared (FTIR) spectroscopy, pH measurements, loss on drying, thermogravimetric analysis (TGA), viscosimetry, gas chromatographic (GC) analysis of pectin monosaccharides, and tensile strength testing of the films. The results suggest that pectins and HPMCs undergo degradation, as expressed by a significant reduction in the dynamic and intrinsic viscosities of the samples. Generally, HPMCs were more sensitive than pectins to neutron irradiation. However, calcium pectinate proved to be the most sensitive among all the investigated polymers. Both polymethacrylate films (Eudragit L and S) resisted loss of mechanical properties following 1 and 2 min of neutron irradiation, whereas irradiation for 3 min implied significant changes in the appearance and the mechanical properties of Eudragit L films. As a conclusion, neutron irradiation results in dose-dependent degradation of the investigated polysaccharides and polymethacrylates. The consequences on the in vitro behavior of a formulation containing such polymers are discussed.

  9. Highly concentrated foam formulation for blast mitigation

    DOEpatents

    Tucker, Mark D.; Gao, Huizhen

    2010-12-14

    A highly concentrated foam formulation for blast suppression and dispersion mitigation for use in responding to a terrorism incident involving a radiological dispersion device. The foam formulation is more concentrated and more stable than the current blast suppression foam (AFC-380), which reduces the logistics burden on the user.

  10. Neutron-proton bremsstrahlung experiments

    SciTech Connect

    Koster, J.E.; Nelson, R.O.; Schillaci, M.E.; Wender, S.A.; Mayo, D.; Brady, F.P.; Romero, J.; Krofcheck, D.; Blann, M.; Anthony, P.; Brown, V.R.; Hansen, L.; Pohl, B.; Sangster, T.C.; Nifenecker, H.; Pinston, J.A.

    1992-12-01

    It is well known that charged particles emit bremsstrahlung radiation when they are accelerated. Classical electron bremsstrahlung occurs when a photon is emitted by an electron accelerated in the field of a nucleus. The bremsstrahlung process also occurs in the scattering of nucleons, for which it is the lowest energy inelastic process that can occur. Like electron bremsstrahlung, nucleon-nucleon bremsstrahlung also requires the exchange of a virtual particle to conserve energy and momentum. In electron bremsstrahlung a virtual photon is exchanged but with two nucleons a meson can be exchanged. Unlike electron bremsstrahlung, in nucleon-nucleon bremsstrahlung the photon can originate from the exchanged meson. This exchange contribution has been shown in calculations to be a significant fraction of bremsstrahlung events. Thus bremsstrahlung serves as a probe of exchange currents in the nucleon-nucleon interaction. Because of a lack of a free neutron target or an intense neutron beam, few measurements of neutron-proton bremsstrahlung exist, each having poor statistical accuracy and poor energy resolution. The white neutron source at the Weapons Neutron Research (WNR) target area at the Los Alamos Meson Physics Facility (LAMPF) produces neutrons with energies from below 50 to above 400 MeV. Using time-of-flight techniques and a liquid hydrogen target, we are measuring the outgoing photons of energies up to 250 MeV at gamma ray angles of around 90{degree} relative to the incident beam. Protons scattered at very forward angles are also detected in coincidence with the gamma rays.

  11. 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.

  12. 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.

  13. In operando neutron diffraction study of the temperature and current rate-dependent phase evolution of LiFePO4 in a commercial battery

    NASA Astrophysics Data System (ADS)

    Sharma, N.; Yu, D. H.; Zhu, Y.; Wu, Y.; Peterson, V. K.

    2017-02-01

    In operando NPD data of electrodes in lithium-ion batteries reveal unusual LiFePO4 phase evolution after the application of a thermal step and at high current. At low current under ambient conditions the LiFePO4 to FePO4 two-phase reaction occurs during the charge process, however, following a thermal step and at higher current this reaction appears at the end of charge and continues into the next electrochemical step. The same behavior is observed for the FePO4 to LiFePO4 transition, occurring at the end of discharge and continuing into the following electrochemical step. This suggests that the bulk (or the majority of the) electrode transformation is dependent on the battery's history, current, or temperature. Such information concerning the non-equilibrium evolution of an electrode allows a direct link between the electrode's functional mechanism that underpins lithium-ion battery behavior and the real-life operating conditions of the battery, such as variable temperature and current, to be made.

  14. Intense neutron source

    SciTech Connect

    Walko, R.J.; Bacon, F.M.; Brainard, J.P.; O'Hagan, J.B.; Riedel, A.A.

    1983-04-01

    A ScD/sub 2/ target film 5x10/sup -5/ m thick, tested in a UHV compatible 200 keV deuterium accelerator baked to 470/sup 0/C, maintained a D-D neutron output rate of 1.0-1.2x10/sup 11//s for 80 out of 140 hours of operation. This result demonstrates that a D-T neutron generator capable of a neutron output rate of 1x10/sup 13//s and having a target lifetime suitable for cancer therapy is possible. Contrary to sputter rate data, ErD/sub 2/ target films appear to erode about twice as fast as ScD/sub 2/ films, making ErD/sub 2/ unsuitable as a target material. A low pressure ion source has been developed to replace the high pressure duopigatron. Experiments have verified that the single ring magnetic cusp ion source can deliver 200 mA of deuterium ions (approx. =60% D/sup +/) at 10-15 A of arc current with a background deuterium pressure of 0.27-0.40 Pa. This source will improve the safety of a D-T machine by reducing the tritium inventory by a factor of 6, and by utilizing the Zr-Al getter as the gas reservoir.

  15. Intense neutron source

    SciTech Connect

    Walko, R.J.; Brainard, J.P.; Riedel, A.A.; O'Hagan, J.B.; Bacon, F.M.

    1982-01-01

    A ScD/sub 2/ target film 5 x 10/sup -5/ m thick, tested in a UHV compatible 200 keV deuterium accelerator baked to 470/sup 0/C, maintained a D-D neutron output rate of 1.0-1.2x10'' /s for 80 out of 140 hours of operation. This result demonstrates that a D-T neutron generator capable of a neutron output rate of 1 x 10/sup 13//s and having a target lifetime suitable for cancer therapy is possible. Contrary to sputter rate data, ErD/sub 2/ target films appear to erode about twice as fast as ScD/sub 2/ films, making ErD/sub 2/ unsuitable as a target material. A low pressure ion source has been developed to replace the more complicated duopigatron. Experiments have verified that the single ring magnetic cusp ion source can deliver 200 mA of deuterium ions (approx. = 60% D/sup +/) at 10-15 A of arc current with a background deuterium pressure of 0.27-0.40 Pa. This source will improve the safety of a D-T machine by reducing the tritium inventory by a factor of 6, and by utilizing the Zr-Al getter as the gas reservoir.

  16. Personnel neutron dosimetry at Department of Energy facilities

    SciTech Connect

    Brackenbush, L.W.; Endres, G.W.R.; Selby, J.M.; Vallario, E.J.

    1980-08-01

    This study assesses the state of personnel neutron dosimetry at DOE facilities. A survey of the personnel dosimetry systems in use at major DOE facilities was conducted, a literature search was made to determine recent advances in neutron dosimetry, and several dosimetry experts were interviewed. It was concluded that personnel neutron dosimeters do not meet current needs and that serious problems exist now and will increase in the future if neutron quality factors are increased and/or dose limits are lowered.

  17. An Evaluation of Grazing-Incidence Optics for Neutron Imaging

    NASA Technical Reports Server (NTRS)

    Gubarev, M. V.; Ramsey, B. D.; Engelhaupt, D. E.; Burgess, J.; Mildner, D. F. R.

    2007-01-01

    The focusing capabilities of neutron imaging optic based on the Wolter-1 geometry have been successfully demonstrated with a beam of long wavelength neutrons with low angular divergence.. A test mirror was fabricated using an electroformed nickel replication process at Marshall Space Flight Center. The neutron current density gain at the focal spot of the mirror is found to be at least 8 for neutron wavelengths in the range from 6 to 20 A. Possible applications of the optics are briefly discussed.

  18. Lithium Loaded Glass Fiber Neutron Detector Tests

    SciTech Connect

    Ely, James H.; Erikson, Luke E.; Kouzes, Richard T.; Lintereur, Azaree T.; Stromswold, David C.

    2009-11-12

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world and, thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. Reported here are the results of tests of the lithium-loaded glass fibers option. This testing measured the neutron detection efficiency and gamma ray rejection capabilities of a small system manufactured by Nucsafe (Oak Ridge, TN).

  19. Neutron Stars

    NASA Astrophysics Data System (ADS)

    van den Heuvel, Ed

    Radio pulsars are unique laboratories for a wide range of physics and astrophysics. Understanding how they are created, how they evolve and where we find them in the Galaxy, with or without binary companions, is highly constraining of theories of stellar and binary evolution. Pulsars' relationship with a recently discovered variety of apparently different classes of neutron stars is an interesting modern astrophysical puzzle which we consider in Part I of this review. Radio pulsars are also famous for allowing us to probe the laws of nature at a fundamental level. They act as precise cosmic clocks and, when in a binary system with a companion star, provide indispensable venues for precision tests of gravity. The different applications of radio pulsars for fundamental physics will be discussed in Part II. We finish by making mention of the newly discovered class of astrophysical objects, the Fast Radio Bursts, which may or may not be related to radio pulsars or neutron stars, but which were discovered in observations of the latter.

  20. Neutron spectroscopy with the Spherical Proportional Counter based on nitrogen gas

    NASA Astrophysics Data System (ADS)

    Bougamont, E.; Dastgheibi, A.; Derre, J.; Galan, J.; Gerbier, G.; Giomataris, I.; Gros, M.; Katsioulas, I.; Jourde, D.; Magnier, P.; Navick, X. F.; Papaevangelou, T.; Savvidis, I.; Tsiledakis, G.

    2017-03-01

    A novel large volume spherical proportional counter, recently developed, is used for neutron measurements. The pure N2 gas is studied for thermal and fast neutron detection, providing a new way for neutron spectroscopy. The neutrons are detected via the 14N (n , p)C14 and 14N (n , α)B11 reactions. The detector is tested for thermal and fast neutrons detection with 252Cf and 241Am -9Be neutron sources. The atmospheric neutrons are successfully measured from thermal up to several MeV, well separated from the cosmic ray background. A comparison of the spherical proportional counter with the current available neutron counters is also presented.

  1. Neutron detectors at IPNS

    SciTech Connect

    Crawford, R.K.; Haumann, J.R.; Ostrowski, G.E.

    1990-01-01

    The heart of each time-of-flight neutron scattering instrument is its complement of detectors and the associated encoding and counting electronics. Currently there are ten fully-scheduled neutron scattering instruments in operation at IPNS, with three more instruments under development. Six of these instruments use position-sensitive neutron detectors (PSDs) of various types. These PSDs include a 30 cm {times} 30 cm, {approximately}3 mm resolution, neutron Anger camera area PSD with {sup 6}Li-glass scintillator; a 2.5 cm dia, {approximately}0.7 mm resolution, microchannel-plate area PSD with {sup 6}Li-glass scintillator; a 20 cm {times} 20 cm, {approximately}5 mm resolution, {sup 3}He proportional counter area PSD; a 40 cm {times} 40 cm, {approximately}4 mm resolution, {sup 3}He proportional counter area PSD; a flat 25 cm long, {approximately}1.6 mm resolution, {sup 3}He proportional counter linear PSD; and 160 cylindrical {sup 3}He proportional counter linear PSDs, each of which is 1.27 cm in dia and 60 cm long and has {approximately}14 mm resolution. In addition to these PSDs, {approximately}750 standard cylindrical {sup 3}He proportional counters of various sizes are utilized on IPNS instruments, and {approximately}20 BF{sub 3} pulsed ion chambers are in use as beam monitors. This paper discusses these various detectors and associated electronics, with emphasis on the instrumental specifications and the reasons for the selection of the different types of detectors. Observed performance of these detectors is also discussed. 19 refs., 5 figs., 2 tabs.

  2. Excision technique in constrained formulations of Einstein equations: collapse scenario

    NASA Astrophysics Data System (ADS)

    Cordero-Carrión, I.; Vasset, N.; Novak, J.; Jaramillo, J. L.

    2015-04-01

    We present a new excision technique used in constrained formulations of Einstein equations to deal with black hole in numerical simulations. We show the applicability of this scheme in several scenarios. In particular, we present the dynamical evolution of the collapse of a neutron star to a black hole, using the CoCoNuT code and this excision technique.

  3. BF3 Neutron Detector Tests

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Siciliano, Edward R.; Woodring, Mitchell L.

    2009-12-09

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world; thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and detection capabilities are being investigated. Reported here are the results of tests of the efficiency of BF3 tubes at a pressure of 800 torr. These measurements were made partially to validate models of the RPM system that have been modified to simulate the performance of BF3-filled tubes. While BF3 could be a potential replacement for 3He, there are limitations to its use in deployed systems.

  4. 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.

  5. Neutron matter, symmetry energy and neutron stars

    NASA Astrophysics Data System (ADS)

    Gandolfi, S.; Steiner, A. 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.

  6. Neutron standard data

    SciTech Connect

    Peelle, R.; Conde, H.

    1988-01-01

    The neutron standards are reviewed with emphasis on the evaluation for ENDFB-VI. Also discussed are the neutron spectrum of /sup 252/Cf spontaneous fission, activation cross sections for neutron flux measurement, and standards for neutron energies greater than 20 MeV. Recommendations are made for future work. 21 refs., 6 figs., 3 tabs.

  7. Borner Ball Neutron Detector

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Bonner Ball Neutron Detector measures neutron radiation. Neutrons are uncharged atomic particles that have the ability to penetrate living tissues, harming human beings in space. The Bonner Ball Neutron Detector is one of three radiation experiments during Expedition Two. The others are the Phantom Torso and Dosimetric Mapping.

  8. Current and potential role of specially formulated foods and food supplements for preventing malnutrition among 6- to 23-month-old children and for treating moderate malnutrition among 6- to 59-month-old children.

    PubMed

    de Pee, Saskia; Bloem, Martin W

    2009-09-01

    Reducing child malnutrition requires nutritious food, breastfeeding, improved hygiene, health services, and (prenatal) care. Poverty and food insecurity seriously constrain the accessibility of nutritious diets that have high protein quality, adequate micronutrient content and bioavailability, macrominerals and essential fatty acids, low antinutrient content, and high nutrient density. Diets based largely on plant sources with few animal-source and fortified foods do not meet these requirements and need to be improved by processing (dehulling, germinating, fermenting), fortification, and adding animal-source foods, e.g., milk, or other specific nutrients. Options include using specially formulated foods (fortified blended foods, commercial infant cereals, or ready-to-use foods [RUFs; pastes, compressed bars, or biscuits]) or complementary food supplements (micronutrient powders or powdered complementary food supplements containing micronutrients, protein, amino acids, and/or enzymes or lipid-based nutrient supplements (120 to 250 kcal/day), typically containing milk powder, high-quality vegetable oil, peanut paste, sugar, and micronutrients. Most supplementary feeding programs for moderately malnourished children supply fortified blended foods, such as corn-soy blend, with oil and sugar, which have shortcomings, including too many antinutrients, no milk (important for growth), suboptimal micronutrient content, high bulk, and high viscosity. Thus, for feeding young or malnourished children, fortified blended foods need to be improved or replaced. Based on success with ready-to-use therapeutic foods (RUTFs) for treating severe acute malnutrition, modifying these recipes is also considered. Commodities for reducing child malnutrition should be chosen on the basis of nutritional needs, program circumstances, availability of commodities, and likelihood of impact. Data are urgently required to compare the impact of new or modified commodities with that of current

  9. Plutonium Detection with Straw Neutron Detectors

    SciTech Connect

    Mukhopadhyay, Sanjoy; Maurer, Richard; Guss, Paul

    2014-03-27

    A kilogram of weapons grade plutonium gives off about 56,000 neutrons per second of which 55,000 neutrons come from spontaneous fission of 240Pu (~6% by weight of the total plutonium). Actually, all even numbered isotopes (238Pu, 240Pu, and 242Pu) produce copious spontaneous fission neutrons. These neutrons induce fission in the surrounding fissile 239Pu with an approximate multiplication of a factor of ~1.9. This multiplication depends on the shape of the fissile materials and the surrounding material. These neutrons (typically of energy 2 MeV and air scattering mean free path >100 meters) can be detected 100 meters away from the source by vehicle-portable neutron detectors. [1] In our current studies on neutron detection techniques, without using 3He gas proportional counters, we designed and developed a portable high-efficiency neutron multiplicity counter using 10B-coated thin tubes called straws. The detector was designed to perform like commercially available fission meters (manufactured by Ortec Corp.) except instead of using 3He gas as a neutron conversion material, we used a thin coating of 10B.

  10. Improved Determination of the Neutron Lifetime

    NASA Astrophysics Data System (ADS)

    Yue, A. T.; Dewey, M. S.; Gilliam, D. M.; Greene, G. L.; Laptev, A. B.; Nico, J. S.; Snow, W. M.; Wietfeldt, F. E.

    2013-11-01

    The most precise determination of the neutron lifetime using the beam method was completed in 2005 and reported a result of τn=(886.3±1.2[stat]±3.2[syst])s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was measured with a neutron monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized Li6 deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the evaluated nuclear data file, ENDF/B-VI Li6(n,t)He4 thermal neutron cross section. In the current work, we measure the detection efficiency of the same monitor used in the neutron lifetime measurement with a second, totally absorbing neutron detector. This direct approach does not rely on the Li6(n,t)He4 cross section or any other nuclear data. The detection efficiency is consistent with the value used in 2005 but is measured with a precision of 0.057%, which represents a fivefold improvement in the uncertainty. We verify the temporal stability of the neutron monitor through ancillary measurements, allowing us to apply the measured neutron monitor efficiency to the lifetime result from the 2005 experiment. The updated lifetime is τn=(887.7±1.2[stat]±1.9[syst])s.

  11. 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.

  12. Continuum quasiparticle random-phase approximation for astrophysical direct neutron capture reactions on neutron-rich nuclei

    NASA Astrophysics Data System (ADS)

    Matsuo, Masayuki

    2015-03-01

    I formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random-phase approximation (QRPA). A focus is put on very-neutron-rich nuclei and low-energy neutron kinetic energy in the range from 1 keV to several MeV, which is relevant to the rapid neutron capture process of nucleosynthesis. I begin with the photoabsorption cross section and the E 1 strength function. Next, in order to apply the reciprocity theorem, I decompose the cross section into partial cross sections corresponding to different channels of one- and two-neutron emission decays of photo-excited states. A numerical example is shown for the photo-absorption of 142Sn and the neutron capture of 141Sn .

  13. Neutrons in cancer therapy

    NASA Astrophysics Data System (ADS)

    Allen, Barry J.

    1995-03-01

    The role of neutrons in the management of cancer has a long history. However, it is only in recent years that neutrons are beginning to find an accepted place as an efficacious radiation modality. Fast neutron therapy is already well established for the treatment of certain cancers, and clinical trials are ongoing. Californium neutron sources are being used in brachytherapy. Boron neutron capture therapy has been well tested with thermal neutrons and epithermal neutron dose escalation studies are about to commence in the USA and Europe. Possibilities of neutron induced auger electron therapy are also discussed. With respect to chemotherapy, prompt neutron capture analysis is being used to study the dose optimization of chemotherapy in the management of breast cancer. The rationales behind these applications of neutrons in the management of cancer are examined.

  14. Nuclear reactor neutron shielding

    DOEpatents

    Speaker, Daniel P; Neeley, Gary W; Inman, James B

    2017-09-12

    A nuclear reactor includes a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel. The lower portion of the reactor pressure vessel is disposed in a reactor cavity. An annular neutron stop is located at an elevation above the uppermost elevation of the nuclear reactor core. The annular neutron stop comprises neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity. The annular neutron stop may comprise an outer neutron stop ring attached to the wall of the reactor cavity, and an inner neutron stop ring attached to the reactor pressure vessel. An excore instrument guide tube penetrates through the annular neutron stop, and a neutron plug comprising neutron absorbing material is disposed in the tube at the penetration through the neutron stop.

  15. Psychiatrists' use of formulation

    PubMed Central

    Hughes, Patricia M.

    2016-01-01

    Both psychologists and psychiatrists are trained to write formulations of their patients' illnesses, with some differences in how they do this. Psychologists focus on psychological understanding, while psychiatrists' formulation brings together aetiology, functioning and a management plan. Mohtashemi et al's study records how some psychiatrists understand formulation and its usefulness. Time pressure was an important barrier to making a full formulation, and some believed the medical role of the psychiatrist was a priority. The study illustrates some of the challenges facing psychiatrists working in the NHS in terms of maintaining high clinical standards and a holistic approach to patient care. PMID:27512593

  16. [Lipid formulations of amphotericin].

    PubMed

    Botero, Martha C; Puentes-Herrera, Marcela; Cortés, Jorge A

    2014-10-01

    Amphotericin B deoxycholate use has increased during the past years in parallel with the increase in the number of immunosuppressed patients suffering invasive fungal infections. This drug is associated with a high rate of side effects, especially renal toxicity. Lipid formulations (liposomal, lipid complex, colloidal suspension and the Indian liposomal formulation) have been developed, which share the same antifungal spectrum but differ in efficacy and toxicity. A review of amphotericin lipid formulations is presented, focusing on differences in efficacy and, especially renal toxicity. The main problem for use of these formulations in Latin America is their highcost.

  17. 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.

  18. 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.

  19. Neutron lab hits second target

    NASA Astrophysics Data System (ADS)

    Banks, Michael

    2008-07-01

    In ancient Egyptian mythology, Isis was the mother goddess from whom all beginnings arose. Although the ISIS facility at the Rutherford Appleton Laboratory in Oxfordshire, UK, has no connections with ancient Egypt, it was so named because it marked the beginning for the field of "pulsed neutron science". Completed in 1984, ISIS remains Europe's only source of pulsed neutron beams and currently has over 20 beamlines that cater for a range of experiments from condensed-matter physics to biomedicine. Some 9000 papers have been published in the last 20 years based on work carried at the facility.

  20. CHINA SPALLATION NEUTRON SOURCE DESIGN.

    SciTech Connect

    WEI,J.

    2007-01-29

    The China Spallation Neutron Source (CSNS) is an accelerator-based high-power project currently in preparation under the direction of the Chinese Academy of Sciences (CAS). The complex is based on an H- linear accelerator, a rapid cycling proton synchrotron accelerating the beam to 1.6 GeV, a solid tungsten target station, and five initial instruments for spallation neutron applications. The facility will operate at 25 Hz repetition rate with a phase-I beam power of about 120 kW. The major challenge is to build a robust and reliable user's facility with upgrade potential at a fractional of ''world standard'' cost.

  1. Neutron storage time measurement for the neutron EDM experiment

    NASA Astrophysics Data System (ADS)

    Griffith, W. Clark; Ito, Takeyasu; Ramsey, John; Makela, Mark; Clayton, Steven; Hennings-Yeomans, Raul; Saidur Rahaman, M.; Currie, Scott; Womack, Todd; Sondheim, Walter; Cooper, Martin

    2010-11-01

    A new experiment to search for the neutron electric dipole moment (nEDM) is under development for installation at the Spallation Neutron Source (SNS) at Oakridge National Laboratory. The experiment will use ultra-cold neutrons (UCN) stored in superfluid helium, along with ^3He atoms acting as a neutron spin analyzer and comagnetometer. One crucial factor affecting the ultimate sensitivity of the experiment is the neutron storage time that can be obtained in the acrylic measurement cell. The acrylic cell walls will be coated with deuterated polystyrene (dPS), which is expected to give a wall loss factor of ˜< 10-5 per bounce when cooled below the point where upscattering by hydrogen impurities contribute to UCN losses. We are currently preparing a measurement at Los Alamos to verify that a 10-5 wall loss factor can be achieved in a dPS coated acrylic test cell. The planned measurement will investigate the temperature dependence of the UCN storage time in the dPS coated test cell between room temperature and below 20 K.

  2. Precision Neutron Scattering Length Measurements with Neutron Interferometry

    NASA Astrophysics Data System (ADS)

    Huber, M. G.; Arif, M.; Jacobson, D. L.; Pushin, D. A.; Abutaleb, M. O.; Shahi, C. B.; Wietfeldt, F. E.; Black, T. C.

    2011-10-01

    Since its inception, single-crystal neutron interferometry has often been utilized for precise neutron scattering length, b, measurements. Scattering length data of light nuclei is particularly important in the study of few nucleon interactions as b can be predicted by two + three nucleon interaction (NI) models. As such they provide a critical test of the accuracy 2+3 NI models. Nuclear effective field theories also make use of light nuclei b in parameterizing mean-field behavior. The NIST neutron interferometer and optics facility has measured b to less than 0.8% relative uncertainty in polarized 3He and to less than 0.1% relative uncertainty in H, D, and unpolarized 3He. A neutron interferometer consists of a perfect silicon crystal machined such that there are three separate blades on a common base. Neutrons are Bragg diffracted in the blades to produce two spatially separate (yet coherent) beam paths much like an optical Mach-Zehnder interferometer. A gas sample placed in one of the beam paths of the interferometer causes a phase difference between the two paths which is proportional to b. This talk will focus on the latest scattering length measurement for n-4He which ran at NIST in Fall/Winter 2010 and is currently being analyzed.

  3. Neutron yield for chemical compounds of actinides

    SciTech Connect

    Vukolov, V.A.; Chukreev, F.E.

    1987-10-01

    The authors assess the neutron yield for a variety of nuclear fuels--uranium hexafluoride, plutonium dioxide, plutonium carbide, plutonium fluoride, americium dioxide, americium fluoride, curium dioxide, and alloys of beryllium with plutonium and americium--by analyzing and configuring experimental data on the cross sections of alpha reactions with lithium 6, lithium 7, beryllium 9, boron 10, boron 11, carbon 13, and fluorine 19 targets. They present a mathematical formulation which, when compared to experimentally derived values, shows comparable accuracy in forecasting neutron yield. They find that the inclusion of stopping power data increases the agreement between experimental and theoretical yields.

  4. Production and applications of neutrons using particle accelerators

    SciTech Connect

    Chichester, David L.

    2009-11-01

    Advances in neutron science have gone hand in hand with the development and of particle accelerators from the beginning of both fields of study. Early accelerator systems were developed simply to produce neutrons, allowing scientists to study their properties and how neutrons interact in matter, but people quickly realized that more tangible uses existed too. Today the diversity of applications for industrial accelerator-based neutron sources is high and so to is the actual number of instruments in daily use is high, and they serve important roles in the fields where they're used. This chapter presents a technical introduction to the different ways particle accelerators are used to produce neutrons, an historical overview of the early development of neutron-producing particle accelerators, a description of some current industrial accelerator systems, narratives of the fields where neutron-producing particle accelerators are used today, and comments on future trends in the industrial uses of neutron producing particle accelerators.

  5. Fabrication of thin copper mesh for electromagnetic interference of display panel by pulse reverse current method and study on the microstructure by small angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Kim, Man; Lee, Joo-Yul; Choi, Yong

    2012-10-01

    A copper sheet with mesh was mass-produced by continuously combining three techniques, electroforming with pulse-reverse current, transfer technique onto a transparent polyimide (PI) film and oxidation processes. Thiourea as an organic additive in a modified copper sulfate bath changes the reduction potentials of copper complexes, which results in effectively controlling the crystal orientation, surface roughness and microstructure of the copper layer. An electroformed copper layer without thiourea has a relatively rough surface with an average surface roughness of about 144.7 nm, whereas, the copper layers with thiourea have a smooth surface with an average surface roughness in the range of 6.3 to 12.1 nm. The copper layers with thiourea have a preferred orientation of crystal structure such that Cu (111) peak intensity increases, whereas, Cu(220) peak intensity decreases with thiourea addition. Electroforming with a rectangular pulse current density including etching at +640 mAcm-2 for 1.8 msec and plating at -160 mAcm-2 for 4 msec in a modified copper sulfate bath with 200 ppm-thiourea at 25 °C is one of optimum conditions to massproduce a copper mesh sheet roll with 300 μm pitch, 10 μm mesh width and thickness, and 200 m long.

  6. Data acquisition system for the neutron scattering instruments at the intense pulsed neutron source

    SciTech Connect

    Crawford, R.K.; Daly, R.T.; Haumann, J.R.; Hitterman, R.L.; Morgan, C.B.; Ostrowski, G.E.; Worlton, T.G.

    1981-01-01

    The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a major new user-oriented facility which is now coming on line for basic research in neutron scattering and neutron radiation damage. This paper describes the data-acquisition system which will handle data acquisition and instrument control for the time-of-flight neutron-scattering instruments at IPNS. This discussion covers the scientific and operational requirements for this system, and the system architecture that was chosen to satisfy these requirements. It also provides an overview of the current system implementation including brief descriptions of the hardware and software which have been developed.

  7. Analysis of the response of innovative neutron detectors with monoenergetic neutron beams

    SciTech Connect

    Romei, C.; Ciolini, R.; Mirzajani, N.; Selici, S.; Di Fulvio, A.; D'Errico, F.; Souza, S. O.; Piotto, M.; Esposito, J.; Colautti, P.

    2013-07-18

    Various neutron detectors are currently under development at the University of Pisa. The response of these devices is investigated using monoenergetic neutron beams produced at the CN accelerator of INFN Legnaro National Laboratories with thin lithium target bombarded by protons at different energies, exploiting the {sup 7}Li(p,n){sup 7}Be reaction.

  8. Neutron field for boron neutron capture therapy

    SciTech Connect

    Kanda, K.; Kobayashi, T.

    1986-01-01

    Recently, the development of an epithermal neutron source has been required by medical doctors for deeper neutron penetrations, which is to be used for deep tumor treatment and diagnosis of metastasis. Several attempts have already been made to realize an epithermal neutron field, such as the undermoderated neutron beam, the filtered neutron beam, and the use of a fission plate. At present, these facilities can not be used for actual therapy. For the treatment of deep tumor, another method has been also proposed in normal water in the body is replaced by heavy water to attain a deeper neutron penetration. At Kyoto University's Research Reactor Institute, almost all physics problems have been settled relative to thermal neutron capture therapy that has been used for treating brain tumors and for biological experiments on malignant melanoma. Very recently feasibility studies to use heavy water have been started both theoretically and experimentally. The calculation shows the deeper penetration of neutrons as expected. Two kinds of experiments were done by using the KUR guide tube: 1. Thermal neutron penetration measurement. 2. Heavy water uptake in vitro sample. In addition to the above experiment using heavy water, the development of a new epithermal neutron source using a large fission plate is in progress, which is part of a mockup experiment of an atomic bomb field newly estimated.

  9. Enhanced NIF neutron activation diagnostics.

    PubMed

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

    2012-10-01

    The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the (89)Zr/(89 m)Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

  10. Enhanced NIF neutron activation diagnostics

    SciTech Connect

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

    2012-10-15

    The NIF neutron activation diagnostic suite relies on removable activation samples, leading to operational inefficiencies and a fundamental lower limit on the half-life of the activated product that can be observed. A neutron diagnostic system measuring activation of permanently installed samples could remove these limitations and significantly enhance overall neutron diagnostic capabilities. The physics and engineering aspects of two proposed systems are considered: one measuring the {sup 89}Zr/{sup 89m}Zr isomer ratio in the existing Zr activation medium and the other using potassium zirconate as the activation medium. Both proposed systems could improve the signal-to-noise ratio of the current system by at least a factor of 5 and would allow independent measurement of fusion core velocity and fuel areal density.

  11. How to Attain an Ultralow Interfacial Tension and a Three-Phase Behavior with a Surfactant Formulation for Enhanced Oil Recovery: A Review. Part 2. Performance Improvement Trends from Winsor's Premise to Currently Proposed Inter- and Intra-Molecular Mixtures.

    PubMed

    Salager, Jean-Louis; Forgiarini, Ana M; Márquez, Laura; Manchego, Lisbeth; Bullón, Johnny

    2013-01-01

    The minimum interfacial tension occurrence along a formulation scan at the so-called optimum formulation is discussed to be related to the interfacial curvature. The attained minimum tension is inversely proportional to the domain size of the bicontinuous microemulsion and to the interfacial layer rigidity, but no accurate prediction is available. The data from a very simple ternary system made of pure products accurately follows the correlation for optimum formulation, and exhibit a linear relationship between the performance index as the logarithm of the minimum tension at optimum, and the formulation variables. This relation is probably too simple when the number of variables is increased as in practical cases. The review of published data for more realistic systems proposed for enhanced oil recovery over the past 30 years indicates a general guidelines following Winsor's basic studies concerning the surfactant-oil-water interfacial interactions. It is well known that the major performance benefits are achieved by blending amphiphilic species at the interface as intermolecular or intramolecular mixtures, sometimes in extremely complex formulations. The complexity is such that a good knowledge of the possible trends and an experienced practical know-how to avoid trial and error are important for the practitioner in enhanced oil recovery.

  12. Dark neutron stars

    NASA Astrophysics Data System (ADS)

    Jones, P. B.

    2017-06-01

    There is good evidence that electron-positron pair formation is not present in that section of the pulsar open magnetosphere, which is the source of coherent radio emission, but the possibility of two-photon pair creation in an outer gap remains. Calculation of transition rates for this process based on measured whole-surface temperatures, combined with a survey of γ-ray, X-ray and optical luminosities, expressed per primary beam lepton, shows that few Fermi-LAT pulsars have significant outer-gap pair creation. For radio-loud pulsars with positive polar-cap corotational charge density and an ion-proton plasma, there must be an outward flow of electrons from some other part of the magnetosphere to maintain a constant net charge on the star. In the absence of pair creation, it is likely that this current is the source of GeV γ-emission observed by the Fermi-LAT and its origin is in the region of the outer gap. With negative polar-cap corotational charge density, the compensating current in the absence of pair creation can consist only of ions or protons. These neutron stars are likely to be radio-quiet, have no observable γ-emission, and hence can be described as dark neutron stars.

  13. Neutron Radiography of Irradiated Nuclear Fuel at Idaho National Laboratory

    NASA Astrophysics Data System (ADS)

    Craft, Aaron E.; Wachs, Daniel M.; Okuniewski, Maria A.; Chichester, David L.; Williams, Walter J.; Papaioannou, Glen C.; Smolinski, Andrew T.

    Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiography. The Neutron Radiography reactor (NRAD) sits beneath a shielded hot cell facility where neutron radiography and other evaluation techniques are performed on these highly radioactive objects. The NRAD currently uses the foil-film transfer technique for imaging fuel that is time consuming but provides high spatial resolution. This paper describes the NRAD and hot cell facilities, the current neutron radiography capabilities available at INL, planned upgrades to the neutron imaging systems, and new facilities being brought online at INL related to neutron imaging.

  14. Neutron radiography of irradiated nuclear fuel at Idaho National Laboratory

    SciTech Connect

    Craft, Aaron E.; Wachs, Daniel M.; Okuniewski, Maria A.; Chichester, David L.; Williams, Walter J.; Papaioannou, Glen C.; Smolinski, Andrew T.

    2015-09-10

    Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiography. The Neutron Radiography reactor (NRAD) sits beneath a shielded hot cell facility where neutron radiography and other evaluation techniques are performed on these highly radioactive objects. The NRAD currently uses the foil-film transfer technique for imaging fuel that is time consuming but provides high spatial resolution. This study describes the NRAD and hot cell facilities, the current neutron radiography capabilities available at INL, planned upgrades to the neutron imaging systems, and new facilities being brought online at INL related to neutron imaging.

  15. Neutron radiography of irradiated nuclear fuel at Idaho National Laboratory

    DOE PAGES

    Craft, Aaron E.; Wachs, Daniel M.; Okuniewski, Maria A.; ...

    2015-09-10

    Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiography. The Neutron Radiography reactor (NRAD) sits beneath a shielded hot cell facility where neutron radiography and other evaluation techniques are performed on these highly radioactive objects. The NRAD currently uses the foil-film transfer technique for imaging fuel that is time consuming but provides high spatial resolution. This study describes the NRAD and hot cell facilities,more » the current neutron radiography capabilities available at INL, planned upgrades to the neutron imaging systems, and new facilities being brought online at INL related to neutron imaging.« less

  16. Neutron radiography of irradiated nuclear fuel at Idaho National Laboratory

    DOE PAGES

    Craft, Aaron E.; Wachs, Daniel M.; Okuniewski, Maria A.; ...

    2015-09-10

    Neutron radiography of irradiated nuclear fuel provides more comprehensive information about the internal condition of irradiated nuclear fuel than any other non-destructive technique to date. Idaho National Laboratory (INL) has multiple nuclear fuels research and development programs that routinely evaluate irradiated fuels using neutron radiography. The Neutron Radiography reactor (NRAD) sits beneath a shielded hot cell facility where neutron radiography and other evaluation techniques are performed on these highly radioactive objects. The NRAD currently uses the foil-film transfer technique for imaging fuel that is time consuming but provides high spatial resolution. This study describes the NRAD and hot cell facilities,more » the current neutron radiography capabilities available at INL, planned upgrades to the neutron imaging systems, and new facilities being brought online at INL related to neutron imaging.« less

  17. 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.

  18. Analysis of the neutron generation from a D-Li neutron source

    SciTech Connect

    Gomes, I.

    1994-02-01

    The study of the neutron generation from the D-Li reaction is an important issue to define the optimum combination of the intervening parameters during the design phase of a D-Li neutron source irradiation facility. The major players in defining the neutron yield from the D-Li reaction are the deuteron incident energy and the beam current, provided that the lithium target is thick enough to stop all incident deuterons. The incident deuteron energy also plays a role on the angular distribution of the generated neutrons, on the energy distribution of the generated neutrons, and on the maximum possible energy of the neutrons. The D-Li reaction produces neutrons with energies ranging from eV`s to several MeV`s. The angular distribution of these neutrons is dependent on the energy of both, incident deuterons and generated neutrons. The deuterons lose energy interacting with the lithium target material in such a way that the energy of the deuterons inside the lithium target varies from the incident deuteron energy to essentially zero. The first part of this study focuses in analyzing the neutron generation rate from the D-Li reaction as a function of the intervening parameters, in defining the source term, in terms of the energy and angular distributions of the generated neutrons, and finally in providing some insights of the impact of varying input parameters on the generation rate and correlated distributions. In the second part an analytical description of the Monte Carlo sampling procedure of the neutron from the D-Li reaction is provided with the aim at further Monte Carlo transport of the D-Li neutrons.

  19. An Accelerator Neutron Source for BNCT

    SciTech Connect

    Blue, Thomas, E

    2006-03-14

    The overall goal of this project was to develop an accelerator-based neutron source (ABNS) for Boron Neutron Capture Therapy (BNCT). Specifically, our goals were to design, and confirm by measurement, a target assembly and a moderator assembly that would fulfill the design requirements of the ABNS. These design requirements were 1) that the neutron field quality be as good as the neutron field quality for the reactor-based neutron sources for BNCT, 2) that the patient treatment time be reasonable, 3) that the proton current required to treat patients in reasonable times be technologially achievable at reasonable cost with good reliability, and accelerator space requirements which can be met in a hospital, and finally 4) that the treatment be safe for the patients.

  20. Neutron crystallography: opportunities, challenges, and limitations.

    PubMed

    Blakeley, Matthew P; Langan, Paul; Niimura, Nobuo; Podjarny, Alberto

    2008-10-01

    Neutron crystallography has had an important, but relatively small role in structural biology over the years. In this review of recently determined neutron structures, a theme emerges of a field currently expanding beyond its traditional boundaries, to address larger and more complex problems, with smaller samples and shorter data collection times, and employing more sophisticated structure determination and refinement methods. The origin of this transformation can be found in a number of advances including first, the development of neutron image-plates and quasi-Laue methods at nuclear reactor neutron sources and the development of time-of-flight Laue methods and electronic detectors at spallation neutron sources; second, new facilities and methods for sample perdeuteration and crystallization; third, new approaches and computational tools for structure determination.

  1. Future of Semiconductor Based Thermal Neutron Detectors

    SciTech Connect

    Nikolic, R J; Cheung, C L; Reinhardt, C E; Wang, T F

    2006-02-22

    Thermal neutron detectors have seen only incremental improvements over the last decades. In this paper we overview the current technology of choice for thermal neutron detection--{sup 3}He tubes, which suffer from, moderate to poor fieldability, and low absolute efficiency. The need for improved neutron detection is evident due to this technology gap and the fact that neutrons are a highly specific indicator of fissile material. Recognizing this need, we propose to exploit recent advances in microfabrication technology for building the next generation of semiconductor thermal neutron detectors for national security requirements, for applications requiring excellent fieldability of small devices. We have developed an innovative pathway taking advantage of advanced processing and fabrication technology to produce the proposed device. The crucial advantage of our Pillar Detector is that it can simultaneously meet the requirements of high efficiency and fieldability in the optimized configuration, the detector efficiency could be higher than 70%.

  2. 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.

  3. Reactivity studies on the advanced neutron source. [Advanced Neutron Source

    SciTech Connect

    Ryskamp, J.M.; Redmond, E.L. II; Fletcher, C.D.

    1990-01-01

    An Advanced Neutron Source (ANS) with a peak thermal neutron flux of about 8.5 {times} 10{sup 19} m{sup {minus}2}s{sup {minus}1} is being designed for condensed matter physics, materials science, isotope production, and fundamental physics research. The ANS is a new reactor-based research facility being planned by Oak Ridge National Laboratory (ORNL) to meet the need for an intense steady-state source of neutrons. The design effort is currently in the conceptual phase. A reference reactor design has been selected in order to examine the safety, performance, and costs associated with this one design. The ANS Project has an established, documented safety philosophy, and safety-related design criteria are currently being established. The purpose of this paper is to present analyses of safety aspects of the reference reactor design that are related to core reactivity events. These analyses include control rod worth, shutdown rod worth, heavy water voiding, neutron beam tube flooding, light water ingress, and single fuel element criticality. Understanding these safety aspects will allow us to make design modifications that improve the reactor safety and achieve the safety related design criteria. 8 refs., 3 tabs.

  4. Subscale testing of prompt agent defeat formulations

    NASA Astrophysics Data System (ADS)

    Knott, A.; Stamatis, D.; Svingala, F.; Lightstone, J.; Miller, K.; Bensman, M.; Bohmke, M.

    2017-01-01

    There is a need to improve the current bioagent defeat systems with formulations that produce lower peak pressure and impulse, sustained high temperatures, and release of biocidal species for prompt defeat applications. In this work, explosive charge configurations similar to fuel-air explosives were detonated in a semi-enclosed chamber configuration. Binder type and fuel-to-oxidizer ratios were varied to observe the effects on combustion performance. Thermocouple measurements and high-speed video were used to monitor the combustion of the dispersed formulation. The down-selected formulations were then tested in a sub-scale vented agent defeat system developed to evaluate performance of formulations against aerosolized Bacillus thuringiensis (Bt) spores. Diagnostics including thermocouples and piezoelectric pressure gauges were utilized to characterize the detonation event. Biological sampling with surface coupons, liquid impingement, and filters of the post detonation environment were utilized to determine spore survivability and to rank the relative effectiveness of each formulation.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Audits of radiopharmaceutical formulations

    SciTech Connect

    Castronovo, F.P. Jr. )

    1992-03-01

    A procedure for auditing radiopharmaceutical formulations is described. To meet FDA guidelines regarding the quality of radiopharmaceuticals, institutional radioactive drug research committees perform audits when such drugs are formulated away from an institutional pharmacy. All principal investigators who formulate drugs outside institutional pharmacies must pass these audits before they can obtain a radiopharmaceutical investigation permit. The audit team meets with the individual who performs the formulation at the site of drug preparation to verify that drug formulations meet identity, strength, quality, and purity standards; are uniform and reproducible; and are sterile and pyrogen free. This team must contain an expert knowledgeable in the preparation of radioactive drugs; a radiopharmacist is the most qualified person for this role. Problems that have been identified by audits include lack of sterility and apyrogenicity testing, formulations that are open to the laboratory environment, failure to use pharmaceutical-grade chemicals, inadequate quality control methods or records, inadequate training of the person preparing the drug, and improper unit dose preparation. Investigational radiopharmaceutical formulations, including nonradiolabeled drugs, must be audited before they are administered to humans. A properly trained pharmacist should be a member of the audit team.

  11. Status of the Neutron Imaging and Diffraction Instrument IMAT

    NASA Astrophysics Data System (ADS)

    Kockelmann, Winfried; Burca, Genoveva; Kelleher, Joe F.; Kabra, Saurabh; Zhang, Shu-Yan; Rhodes, Nigel J.; Schooneveld, Erik M.; Sykora, Jeff; Pooley, Daniel E.; Nightingale, Jim B.; Aliotta, Francesco; Ponterio, Rosa C.; Salvato, Gabriele; Tresoldi, Dario; Vasi, Cirino; McPhate, Jason B.; Tremsin, Anton S.

    A cold neutron imaging and diffraction instrument, IMAT, is currently being constructed at the ISIS second target station. IMAT will capitalize on time-of-flight transmission and diffraction techniques available at a pulsed neutron source. Analytical techniques will include neutron radiography, neutron tomography, energy-selective neutron imaging, and spatially resolved diffraction scans for residual strain and texture determination. Commissioning of the instrument will start in 2015, with time-resolving imaging detectors and two diffraction detector prototype modules. IMAT will be operated as a user facility for material science applications and will be open for developments of time-of-flight imaging methods.

  12. Nonequilibrium Dynamics and the Evolution of Superfluid Neutron Stars

    NASA Astrophysics Data System (ADS)

    Sauls, Jame

    2016-07-01

    The interior crust and the liquid core of neutron stars are predicted to be a mixture of neutron and proton superfluids and a liquid of relativistic electrons and muons. Quantized vortices in the neutron superfluid and quantized flux lines in the proton superconductor are topological defects of these hadronic condensates. I discuss the roles of nucleation, interaction and evolution of topological defects under non-equilibrium conditions in the context of our current understanding and models of the rotational dynamics of pulsars, as well as thermal and magnetic field evolution of neutron stars. I include some speculative ideas on possibile turbulent vortex states in neutron star interiors.

  13. 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)

  14. 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.

  15. Reactive decontamination formulation

    DOEpatents

    Giletto, Anthony; White, William; Cisar, Alan J.; Hitchens, G. Duncan; Fyffe, James

    2003-05-27

    The present invention provides a universal decontamination formulation and method for detoxifying chemical warfare agents (CWA's) and biological warfare agents (BWA's) without producing any toxic by-products, as well as, decontaminating surfaces that have come into contact with these agents. The formulation includes a sorbent material or gel, a peroxide source, a peroxide activator, and a compound containing a mixture of KHSO.sub.5, KHSO.sub.4 and K.sub.2 SO.sub.4. The formulation is self-decontaminating and once dried can easily be wiped from the surface being decontaminated. A method for decontaminating a surface exposed to chemical or biological agents is also disclosed.

  16. Intercomparison of high energy neutron personnel dosimeters

    SciTech Connect

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

    1993-03-01

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

  17. Neutron-transport equation in a general curvelinear coordinate system

    SciTech Connect

    Takahashi, H

    1981-01-01

    Different from a fission reactor, a fusion reactor has complex geometry, such as toroidal geometry. Neutron transport equation for the toroidal coordinate system has been derived by using coordinate transformation from the cartesian coordinate. These methods require rather tedious calculations. Presented here is a simple method to formulate the neutron transport equation in the general curvelinear coordinate system. The equations for parabolic cylinder and toroidal coordinate systems are derived as an example.

  18. Neutron scattering instrumentation for biology at spallation neutron sources

    SciTech Connect

    Pynn, R.

    1994-12-31

    Conventional wisdom holds that since biological entities are large, they must be studied with cold neutrons, a domain in which reactor sources of neutrons are often supposed to be pre-eminent. In fact, the current generation of pulsed spallation neutron sources, such as LANSCE at Los Alamos and ISIS in the United Kingdom, has demonstrated a capability for small angle scattering (SANS) - a typical cold- neutron application - that was not anticipated five years ago. Although no one has yet built a Laue diffractometer at a pulsed spallation source, calculations show that such an instrument would provide an exceptional capability for protein crystallography at one of the existing high-power spoliation sources. Even more exciting is the prospect of installing such spectrometers either at a next-generation, short-pulse spallation source or at a long-pulse spallation source. A recent Los Alamos study has shown that a one-megawatt, short-pulse source, which is an order of magnitude more powerful than LANSCE, could be built with today`s technology. In Europe, a preconceptual design study for a five-megawatt source is under way. Although such short-pulse sources are likely to be the wave of the future, they may not be necessary for some applications - such as Laue diffraction - which can be performed very well at a long-pulse spoliation source. Recently, it has been argued by Mezei that a facility that combines a short-pulse spallation source similar to LANSCE, with a one-megawatt, long-pulse spallation source would provide a cost-effective solution to the global shortage of neutrons for research. The basis for this assertion as well as the performance of some existing neutron spectrometers at short-pulse sources will be examined in this presentation.

  19. Neutron quality factor

    SciTech Connect

    1995-06-01

    Both the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP) have recommended that the radiation quality weighting factor for neutrons (Q{sub n}, or the corresponding new modifying factor, w{sub R}) be increased by a value of two for most radiation protection practices. This means an increase in the recommended value for Q{sub n} from a nominal value of 10 to a nominal value of 20. This increase may be interpreted to mean that the biological effectiveness of neutrons is two times greater than previously thought. A decision to increase the value of Q{sub n} will have a major impact on the regulations and radiation protection programs of Federal agencies responsible for the protection of radiation workers. Therefore, the purposes of this report are: (1) to examine the general concept of {open_quotes}quality factor{close_quotes} (Q) in radiation protection and the rationale for the selection of specific values of Q{sub n}; and (2) to make such recommendations to the Federal agencies, as appropriate. This report is not intended to be an exhaustive review of the scientific literature on the biological effects of neutrons, with the aim of defending a particular value for Q{sub n}. Rather, the working group examined the technical issues surrounding the current recommendations of scientific advisory bodies on this matter, with the aim of determining if these recommendations should be adopted by the Federal agencies. Ultimately, the group concluded that there was no compelling basis for a change in Q{sub n}. The report was prepared by Federal scientists working under the auspices of the Science Panel of the Committee on Interagency Radiation Research and Policy Coordination (CIRRPC).

  20. Imprinted spiral structures as neutron polarizers.

    SciTech Connect

    Lohstroh, W.

    1998-10-07

    Neutron diffraction from magnetic spiral structures is governed by strong selection rules for the polarization of the outgoing beam. When the sample is entirely of one chirality--for instance a right handed spiral--the neutrons diffracted by some Bragg reflections are fully polarized. While the scattering theory has been formulated long ago, attempts to controllably modify the population of left handed and right handed spiral domains in natural magnetic structures (which for instance occur in some rare earth metals) have been largely unsuccessful. In contrast, we have been able to imprint helical magnetic structures in La/Fe multilayers (each layer approximately 30 {angstrom} thick) simply by rotating the growing sample in a weak external field (30e). A first estimate is given of the efficiency of these multilayers as polarizers of neutron beams.

  1. Iterative Reconstruction of Coded Source Neutron Radiographs

    NASA Astrophysics Data System (ADS)

    Santos-Villalobos, Hector J.; Bingham, Philip R.; Gregor, Jens

    2013-06-01

    A coded source facilitates high-resolution neutron imaging through magnification but requires that the radiographic data be deconvolved. A comparison of convolution-based and model-based de-blurring algorithms has been performed. Two convolution-based approaches are assessed, direct deconvolution and an iterative algorithm based on a maximum likelihood estimation (MLE)-like framework. The model-based approach specifies a geometric model of the neutron beam with a least squares formulation of the inverse imaging problem. Simulated data for both uniform and Gaussian shaped source distributions was used to study the impact of non-uniformities present in neutron beam distributions on the reconstructed images. Results indicate that the model based reconstruction method will match resolution and improve on contrast over convolution methods in the presence of non-uniform sources. Additionally, the model based iterative algorithm provides direct calculation of quantitative transmission values while the convolution based methods must be normalized based on known values.

  2. Iterative Reconstruction of Coded Source Neutron Radiographs

    SciTech Connect

    Santos-Villalobos, Hector J; Bingham, Philip R; Gregor, Jens

    2013-01-01

    Use of a coded source facilitates high-resolution neutron imaging through magnifications but requires that the radiographic data be deconvolved. A comparison of direct deconvolution with two different iterative algorithms has been performed. One iterative algorithm is based on a maximum likelihood estimation (MLE)-like framework and the second is based on a geometric model of the neutron beam within a least squares formulation of the inverse imaging problem. Simulated data for both uniform and Gaussian shaped source distributions was used for testing to understand the impact of non-uniformities present in neutron beam distributions on the reconstructed images. Results indicate that the model based reconstruction method will match resolution and improve on contrast over convolution methods in the presence of non-uniform sources. Additionally, the model based iterative algorithm provides direct calculation of quantitative transmission values while the convolution based methods must be normalized base on known values.

  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. Accelerated Neutron Testing of Semiconductor Devices at the LANSCE

    NASA Astrophysics Data System (ADS)

    Wender, S. A.; Bateman, F. B.; Haight, R. C.; Ullmann, J. L.

    1998-04-01

    The high-energy neutron source at the Los Alamos Neutron Science Center (LANSCE) produces beams of neutrons for accelerated testing of integrated circuit devices. Neutrons produced in the atmosphere by cosmic-rays are thought to be a significant threat to integrated circuits both at aircraft altitudes as well as at lower elevations. Neutrons have been shown to cause single event upsets, multiple event upsets, latchup and burnout in semiconductor devices. Neutrons are produced at LANSCE via spallation reactions with the 800 MeV pulsed proton beam. Proton beam currents of about 2 microamperes strike a tungsten target and produce a spectrum of neutrons whose energy and intensity can be precisely measured by time-of-flight techniques. The neutron spectrum produced in this manner has energies up to approximately 600 MeV and is very similar in shape to the atmospheric neutron spectrum at 40,000 ft. A flight path located at 20 m from the neutron production target is dedicated to accelerated testing of semiconductor devices. The integrated neutron flux above 1 MeV is about 10^6 n/cm^2/sec over an area about 10 cm in diameter. This intensity is about 10^5 (10^7) times greater than the cosmic-ray neutron flux at 40,000 ft (sea level).

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Neutron Lifetime Measurements

    NASA Astrophysics Data System (ADS)

    Nico, J. S.

    2006-11-01

    Precision measurements of neutron beta decay address basic questions in nuclear and particle physics, astrophysics, and cosmology. As the simplest semileptonic decay system, the free neutron plays an important role in understanding the physics of the weak interaction, and improving the precision of the neutron lifetime is fundamental to testing the validity of the theory. The neutron lifetime also directly affects the relative abundance of primordial helium in big bang nucleosynthesis. There are two distinct strategies for measuring the lifetime. Experiments using cold neutrons measure the absolute specific activity of a beam of neutrons by counting decay protons; experiments using confined, ultracold neutrons determine the lifetime by counting neutrons that remain after some elapsed time. The status of the recent lifetime measurements using both of these techniques is discussed.

  11. Neutron Lifetime Measurements

    SciTech Connect

    Nico, J. S.

    2006-11-17

    Precision measurements of neutron beta decay address basic questions in nuclear and particle physics, astrophysics, and cosmology. As the simplest semileptonic decay system, the free neutron plays an important role in understanding the physics of the weak interaction, and improving the precision of the neutron lifetime is fundamental to testing the validity of the theory. The neutron lifetime also directly affects the relative abundance of primordial helium in big bang nucleosynthesis. There are two distinct strategies for measuring the lifetime. Experiments using cold neutrons measure the absolute specific activity of a beam of neutrons by counting decay protons; experiments using confined, ultracold neutrons determine the lifetime by counting neutrons that remain after some elapsed time. The status of the recent lifetime measurements using both of these techniques is discussed.

  12. 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.

  13. 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.

  14. Intermediate energy neutron beams from the MURR.

    PubMed

    Brugger, R M; Herleth, W H

    1990-01-01

    Several reactors in the United States are potential candidates to deliver beams of intermediate energy neutrons for NCT. At this time, moderators, as compared to filters, appear to be the more effective means of tailoring the flux of these reactors. The objective is to sufficiently reduce the flux of fast neutrons while producing enough intermediate energy neutrons for treatments. At the University of Missouri Research Reactor (MURR), the code MCNP has recently been used to calculate doses in a phantom. First, "ideal" beams of 1, 35, and 1000 eV neutrons were analyzed to determine doses and advantage depths in the phantom. Second, a high quality beam that had been designed to fit in the thermal column of the MURR, was reanalyzed. MCNP calculations of the dose in phantom in this beam confirmed previous calculations and showed that this beam would be a nearly ideal one with neutrons of the desired energy and also a high neutron current. However, installation of this beam will require a significant modification of the thermal column of the MURR. Therefore, a second beam that is less difficult to build and install, but of lower neutron current, has been designed to fit in MURR port F. This beam is designed using inexpensive A1, S, and Pb. The doses calculated in the phantom placed in this beam show that it will be satisfactory for sample tests, animal tests, and possible initial patient trials. Producing this beam will require only modest modifications of the existing tube.

  15. Formulation and stability of cytokine therapeutics.

    PubMed

    Lipiäinen, Tiina; Peltoniemi, Marikki; Sarkhel, Sanjay; Yrjönen, Teijo; Vuorela, Heikki; Urtti, Arto; Juppo, Anne

    2015-02-01

    Cytokines are messenger proteins that regulate the proliferation and differentiation of cells and control immune responses. Interferons, interleukins, and growth factors have applications in cancer, autoimmune, and viral disease treatment. The cytokines are susceptible to chemical and physical instability. This article reviews the structure and stability issues of clinically used cytokines, as well as formulation strategies for improved stability. Some general aspects for identifying most probable stability concerns, selecting excipients, and developing stable cytokine formulations are presented. The vast group of cytokines offers possibilities for new biopharmaceuticals. The formulation approaches of the current cytokine products could facilitate development of new biopharmaceuticals.

  16. Development of a sealed-accelerator-tube neutron generator

    PubMed

    Verbeke; Leung; Vujic

    2000-10-01

    Sealed-accelerator-tube neutron generators are being developed in Lawrence Berkeley National Laboratory (LBNL) for applications ranging from neutron radiography to boron neutron capture therapy and neutron activation analysis. The new generation of high-output neutron generators is based on the D-T fusion reaction, producing 14.1-MeV neutrons. The main components of the neutron tube--the ion source, the accelerator and the target--are all housed in a sealed metal container without external pumping. Thick-target neutron yield computations are performed in this paper to estimate the neutron yield of titanium and scandium targets. With an average deuteron beam current of 1 A and an energy of 120 keV, a time-averaged neutron production of approximately 10(14) n/s can be estimated for a tritiated target, for both pulsed and cw operations. In mixed deuteron/triton beam operation, a beam current of 2 A at 150 keV is required for the same neutron output. Recent experimental results on ion sources and accelerator columns are presented and discussed.

  17. Characteristics of the neutron flux from a D-Li neutron source

    SciTech Connect

    Gomes, I.; Smith, D.L.

    1994-07-01

    A D-Li neutron source produces a high flux of neutrons which can be used for testing fusion materials. The characteristics exhibited by the neutron flux inside the test assembly volume of a D-Li neutron source irradiation facility is a function of several design options, such as deuteron energy, beam current, beam cross sectional area, and lithium target configuration, among others. The influence of each of these parameters on the overall performance of the machine, in terms of best results for irradiation of materials for fusion applications, can be inferred by scoping their impact on the uncollided neutron flux magnitude and distribution. The first part of this paper describes an analysis performed on the uncollided neutron flux (without material inside the test assembly region) for different beam-target configurations for determining the effect of varying the elements of the configuration on the uncollided neutron flux gradient. The second section deals with the neutron energy spectrum from the D-Li reaction and a brief discussion on {open_quotes}fusion reactor spectrum{close_quotes} is also presented. In the third section results from calculations of the volume with uncollided neutron above a threshold value are presented.

  18. Modification of the University of Washington Neutron Radiotherapy Facility for optimization of neutron capture enhanced fast-neutron therapy.

    PubMed

    Nigg, D W; Wemple, C A; Risler, R; Hartwell, J K; Harker, Y D; Laramore, G E

    2000-02-01

    A modified neutron production target assembly has been developed to provide improved performance of the proton-cyclotron-based neutron radiotherapy facility at the University of Washington for applications involving neutron capture enhanced fast-neutron therapy. The new target produces a neutron beam that yields essentially the same fast-neutron physical depth-dose distribution as is produced by the current UW clinical system, but that also has an increased fraction of BNCT enhancement relative to the total therapeutic dose. The modified target is composed of a 5-millimeter layer of beryllium, followed by a 2.5-millimeter layer of tungsten, with a water-cooled copper backing. Measurements of the free-field neutron spectrum of the beam produced by the new target were performed using activation foils with a direct spectral unfolding technique. Water phantom measurements were performed using a tissue-equivalent ion chamber to characterize the fast-neutron depth-dose curve and sodium activation in soda-lime glass beads to characterize the thermal-neutron flux (and thus the expected neutron capture dose enhancement) as a function of depth. The results of the various measurements were quite consistent with expectations based on the design calculations for the modified target. The spectrum of the neutron beam produced by the new target features an enhanced low-energy flux component relative to the spectrum of the beam produced by the standard UW target. However, it has essentially the same high-energy neutron flux, with a reduced flux component in the mid-range of the energy spectrum. As a result, the measured physical depth-dose curve in a large water phantom has the same shape compared to the case of the standard UW clinical beam, but approximately twice the level of BNCT enhancement per unit background neutron dose at depths of clinical interest. In-vivo clinical testing of BNCT-enhanced fast-neutron therapy for canine lung tumors using the new beam was recently

  19. 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.

  20. 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.

  1. Neutron stars: A cosmic hadron physics laboratory

    NASA Technical Reports Server (NTRS)

    Pines, David

    1989-01-01

    A progress report is given on neutron stars as a cosmic hadron physics laboratory. Particular attention is paid to the crustal neutron superfluid, and to the information concerning its properties which may be deduced from observations of pulsar glitches and postglitch behavior. Current observational evidence concerning the softness or stiffness of the high density neutron matter equation of state is reviewed briefly, and the (revolutionary) implications of a confirmation of the existence of a 0.5 ms pulsar at the core of (Supernova) SN1987A are discussed.

  2. Neutron stars - A cosmic hadron physics laboratory

    NASA Technical Reports Server (NTRS)

    Pines, David

    1989-01-01

    A progress report is given on neutron stars as a cosmic hadron physics laboratory. Particular attention is paid to the crustal neutron superfluid, and to the information concerning its properties which may be deduced from observations of pulsar glitches and postglitch behavior. Current observational evidence concerning the softness or stiffness of the high density neutron matter equation of state is reviewed briefly, and the (revolutionary) implications of a confirmation of the existence of a 0.5 ms pulsar at the core of (Supernova) SN1987A are discussed.

  3. Neutron removal cross section as a measure of neutron skin

    SciTech Connect

    Fang, D. Q.; Ma, Y. G.; Cai, X. Z.; Tian, W. D.; Wang, H. W.

    2010-04-15

    We study the relation between neutron removal cross section (sigma{sub -N}) and neutron skin thickness for finite neutron-rich nuclei using the statistical abrasion ablation model. Different sizes of neutron skin are obtained by adjusting the diffuseness parameter of neutrons in the Fermi distribution. It is demonstrated that there is a good linear correlation between sigma{sub -N} and the neutron skin thickness for neutron-rich nuclei. Further analysis suggests that the relative increase of neutron removal cross section could be used as a quantitative measure for neutron skin thickness in neutron-rich nuclei.

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

    NASA Astrophysics Data System (ADS)

    Lavelle, Christopher M.

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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. Producing Mono-energetic Neutrons for Research

    NASA Astrophysics Data System (ADS)

    Jepeal, Steven

    2014-09-01

    Free neutrons are seldom produced in nature and are unstable, decaying back to protons with a mean life of 881s. The only natural sources are spontaneous fission of actinides and cosmic ray interactions, both of which are rare processes. The detection of neutrons indicates unusual nuclear activity, allowing neutron detection the roll of the ``smoking gun'' for seeking potential nuclear terrorism. Recently, there has been a push for the development of new neutron detectors, ideally sufficiently inexpensive that a detector can be carried by all first responders such as police and fire fighters. One promising new material is the inorganic scintillator CLYC, a crystal of chlorine, lithium, yttrium and cesium. CLYC has a high energy resolution not only for gamma rays, but also for fast neutrons. At the University of Massachusetts, Lowell, CLYC is being developed in collaboration with local industrial companies. To evaluate its response to neutrons, in to 500 keV to 4 MeV energy range, the CN Van de Graaff generator is used to produce neutrons, via the 7Li(p,n)7Be reaction. However, the important energy regime of 4--10 MeV is currently inaccessible. This current project is to build a gas-cell target to enable the D(d,n)3He reaction and produce neutrons of energy up to 9 MeV, an approach that has been used successfully at the University of Kentucky. The project involves some mechanical engineering management, then chamber construction, vacuum testing, developing thin window technology, and finally commissioning of the gas cell using accelerated beams. The commissioning will be physics rich in quantifying the flux and energy resolution of the neutron beam produced. Free neutrons are seldom produced in nature and are unstable, decaying back to protons with a mean life of 881s. The only natural sources are spontaneous fission of actinides and cosmic ray interactions, both of which are rare processes. The detection of neutrons indicates unusual nuclear activity, allowing

  11. Saltstone Clean Cap Formulation

    SciTech Connect

    Langton, C

    2005-04-22

    The current operation strategy for using Saltstone Vault 4 to receive 0.2 Ci/gallon salt solution waste involves pouring a clean grout layer over the radioactive grout prior to initiating pour into another cell. This will minimize the radiating surface area and reduce the dose rate at the vault and surrounding area. The Clean Cap will be used to shield about four feet of Saltstone poured into a Z-Area vault cell prior to moving to another cell. The minimum thickness of the Clean Cap layer will be determined by the cesium concentration and resulting dose levels and it is expected to be about one foot thick based on current calculations for 0.1 Ci Saltstone that is produced in the Saltstone process by stabilization of 0.2 Ci salt solution. This report documents experiments performed to identify a formulation for the Clean Cap. Thermal transient calculations, adiabatic temperature rise measurements, pour height, time between pour calculations and shielding calculations were beyond the scope and time limitations of this study. However, data required for shielding calculations (composition and specific gravity) are provided for shielding calculations. The approach used to design a Clean Cap formulation was to produce a slurry from the reference premix (10/45/45 weight percent cement/slag/fly ash) and domestic water that resembled as closely as possible the properties of the Saltstone slurry. In addition, options were investigated that may offer advantages such as less bleed water and less heat generation. The options with less bleed water required addition of dispersants. The options with lower heat contained more fly ash and less slag. A mix containing 10/45/45 weight percent cement/slag/fly ash with a water to premix ratio of 0.60 is recommended for the Clean Cap. Although this mix may generate more than 3 volume percent standing water (bleed water), it has rheological, mixing and flow properties that are similar to previously processed Saltstone. The recommended

  12. Direct URCA process in neutron stars

    NASA Technical Reports Server (NTRS)

    Lattimer, James M.; Prakash, Madappa; Pethick, C. J.; Haensel, Pawel

    1991-01-01

    It is shown that the direct URCA process can occur in neutron stars if the proton concentration exceeds some critical value in the range 11-15 percent. The proton concentration, which is determined by the poorly known symmetry energy of matter above nuclear density, exceeds the critical value in many current calculations. If it occurs, the direct URCA process enhances neutrino emission and neutron star cooling rates by a large factor compared to any process considered previously.

  13. Performance of a gas target neutron source for radiotherapy.

    PubMed

    Deluca, P M; Torti, R P; Chenevert, G M; Detorie, N A; Tesmer, J R; Kelsey, C A

    1978-09-01

    The performance of a compact and efficient neutron generator, using the 3H(d, n) reaction and a gas target, is reported. The target is formed in a windowless, differentially pumped vessel pressurised to 7.5 Torr. An extended source of 15 MeV neutrons is produced when the target is bombarded by a 10 mA beam of 210 keV deuterons. Measurements are reported of the neutron energy spectra, neutron and gamma-ray dose rates, target lifetime and tritium handling. The neutron flux distribution of the extended target was measured and compared with the predictions of a simple beam-gas interaction model. The measured neutron source strength is 1.7 +/- 0.4 X 10(12) neutrons per second. The source output is limited by target beam current, not target power considerations.

  14. Design and characterisation of a pulsed neutron interrogation facility.

    PubMed

    Favalli, A; Pedersen, B

    2007-01-01

    The Joint Research Centre recently obtained a license to operate a new experimental device intended for research in the field of nuclear safeguards. The research projects currently being planned for the new device includes mass determination of fissile materials in matrices and detection of contraband non-nuclear materials. The device incorporates a commercial pulsed neutron generator and a large graphite mantle surrounding the sample cavity. In this configuration, a relatively high thermal neutron flux with a long lifetime is achieved inside the sample cavity. By pulsing the neutron generator, a sample may be interrogated by a pure thermal neutron flux during repeated time periods. The paper reports on the design of the new device and the pulsed fast and thermal neutron source. The thermal neutron flux caused by the neutron generator and the graphite structure has been characterised by foil activation, fission chamber and (3)He proportional counter measurements.

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

    NASA Astrophysics Data System (ADS)

    Hoogerheide, Shannon Fogwell; BL2 Collaboration

    2017-01-01

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

  16. Neutron computed tomography.

    PubMed

    Koeppe, R A; Brugger, R M; Schlapper, G A; Larsen, G N; Jost, R J

    1981-02-01

    A neutron-transmission computed tomography scanning system has been built for scanning biological materials. An oxygen filtered beam of 2.35 MeV neutrons was used for the measurements. The studies to date show that the interactions of these energy neutrons with samples simulating biological materials are more sensitive than X-rays to variations in the content of the material, thus providing the ability to produce high quality images. The neutron scans suggest that neutrons can be an effective radiation for the imaging of biological materials.

  17. 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.

  18. 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.

  19. 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)

  20. High energy neutron dosimeter

    DOEpatents

    Sun, Rai Ko S.F.

    1994-01-01

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

  1. 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.

  2. Formulations and nebulizer performance.

    PubMed

    O'Riordan, Thomas G

    2002-11-01

    To deliver a drug by nebulization, the drug must first be dispersed in a liquid (usually aqueous) medium. After application of a dispersing force (either a jet of gas or ultrasonic waves), the drug particles are contained within the aerosol droplets, which are then inhaled. Some drugs readily dissolve in water, whereas others need a cosolvent such as ethanol or propylene glycol. Some drugs are delivered as suspensions, and the efficiency of nebulizers can be different for solutions and suspensions. Solutions are delivered more efficiently with most devices. In general, conventional ultrasonic nebulizers should not be used to aerosolize suspensions, because of low efficiency. Newer strategies to improve the delivery of non-water-soluble drugs include the use of liposomes and the milling of the drug into very small "nanoparticles." In addition to the active therapeutic ingredient and solvents, drug formulations may include buffers (the solubility of some medications is influenced by pH), stabilizers, and, in the case of multi-dose preparations, antibacterial agents. Though formulations are designed to optimize drug solubility and stability, changes in formulation can also affect inhaled mass, particle size, and treatment time, though the differences between nebulizer brands probably have a greater impact than differences in formulation. Ultrasonic and jet nebulizers may damage protein and other complex agents through heat or shear stress. Additives to multi-dose formulations, especially antimicrobial and chelating agents, may cause adverse events, so there is a trend towards single-use, preservative-free vials.

  3. Granulated decontamination formulations

    DOEpatents

    Tucker, Mark D.

    2007-10-02

    A decontamination formulation and method of making that neutralizes the adverse health effects of both chemical and biological compounds, especially chemical warfare (CW) and biological warfare (BW) agents, and toxic industrial chemicals. The formulation provides solubilizing compounds that serve to effectively render the chemical and biological compounds, particularly CW and BW compounds, susceptible to attack, and at least one reactive compound that serves to attack (and detoxify or kill) the compound. The formulation includes at least one solubilizing agent, a reactive compound, a sorbent additive, and water. A highly adsorbent sorbent additive (e.g., amorphous silica, sorbitol, mannitol, etc.) is used to "dry out" one or more liquid ingredients into a dry, free-flowing powder that has an extended shelf life, and is more convenient to handle and mix in the field.

  4. Sunscreen product formulation.

    PubMed

    Tanner, Paul R

    2006-01-01

    On the surface, sunscreen products are pretty simple. They consist of a delivery vehicle containing one or more sunscreen active ingredients. When applied to the skin, these sunscreen actives intercept solar ultraviolet (UV) rays before they can damage the underlying skin. However, while conceptually simple, a detailed analysis reveals that sunscreen formulations are quite complex, requiring careful selection of sunscreen active and vehicle components to control multiple performance and in-use parameters.Thus, to enable a better understanding and appreciation of sunscreen products, the typical steps in formulating a sunscreen product are described. Throughout this process, the key is to apply scientific principles together with a bit of formulation art to holistically create the best sunscreen product that meets the design targets--a sunscreen product that people will use regularly and properly.

  5. Advanced protein formulations

    PubMed Central

    Wang, Wei

    2015-01-01

    It is well recognized that protein product development is far more challenging than that for small-molecule drugs. The major challenges include inherent sensitivity to different types of stresses during the drug product manufacturing process, high rate of physical and chemical degradation during long-term storage, and enhanced aggregation and/or viscosity at high protein concentrations. In the past decade, many novel formulation concepts and technologies have been or are being developed to address these product development challenges for proteins. These concepts and technologies include use of uncommon/combination of formulation stabilizers, conjugation or fusion with potential stabilizers, site-specific mutagenesis, and preparation of nontraditional types of dosage forms—semiaqueous solutions, nonfreeze-dried solid formulations, suspensions, and other emerging concepts. No one technology appears to be mature, ideal, and/or adequate to address all the challenges. These gaps will likely remain in the foreseeable future and need significant efforts for ultimate resolution. PMID:25858529

  6. Commissioning of the upgraded ultracold neutron source at Los Alamos Neutron Science Center

    NASA Astrophysics Data System (ADS)

    Pattie, Robert; LANL-UCN Team Team

    2016-09-01

    The spallation-driven solid-deuterium ultracold neutron (UCN) source at Los Alamos Neutron Science Center (LANSCE) has provided a facility for precision measurements of fundamental symmetries via the decay observables from neutron beta decay for nearly a decade. In preparation for a new room temperature neutron electric dipole moment (nEDM) experiment and to increase the statistical sensitivity of all experiments using the source an effort to upgrade the existing source has been carried out during 2016. This upgrade includes installing a redesigned cold neutron moderator and with optimized UCN converter geometries, improved coupling and nickel-phosphorus coating of the UCN transport system through the biological shielding, optimization of beam timing structure, and increase of the proton beam current. We will present the result of the commissioning run of the new source.

  7. Beam characterization at the Neutron Radiography Reactor

    SciTech Connect

    Sarah W. Morgan; Jeffrey C. King; Chad L. Pope

    2013-12-01

    The quality of a neutron-imaging beam directly impacts the quality of radiographic images produced using that beam. Fully characterizing a neutron beam, including determination of the beam's effective length-to-diameter ratio, neutron flux profile, energy spectrum, potential image quality, and beam divergence, is vital for producing quality radiographic images. This paper provides a characterization of the east neutron imaging beamline at the Idaho National Laboratory Neutron Radiography Reactor (NRAD). The experiments which measured the beam's effective length-to-diameter ratio and potential image quality are based on American Society for Testing and Materials (ASTM) standards. An analysis of the image produced by a calibrated phantom measured the beam divergence. The energy spectrum measurements consist of a series of foil irradiations using a selection of activation foils, compared to the results produced by a Monte Carlo n-Particle (MCNP) model of the beamline. The NRAD has an effective collimation ratio greater than 125, a beam divergence of 0.3 +_ 0.1 degrees, and a gold foil cadmium ratio of 2.7. The flux profile has been quantified and the facility is an ASTM Category 1 radiographic facility. Based on bare and cadmium covered foil activation results, the neutron energy spectrum used in the current MCNP model of the radiography beamline over-samples the thermal region of the neutron energy spectrum.

  8. Lubrication in tablet formulations.

    PubMed

    Wang, Jennifer; Wen, Hong; Desai, Divyakant

    2010-05-01

    Theoretical aspects and practical considerations of lubrication in tablet compression are reviewed in this paper. Properties of the materials that are often used as lubricants, such as magnesium stearate, in tablet dosage form are summarized. The manufacturing process factors that may affect tablet lubrication are discussed. As important as the lubricants in tablet formulations are, their presence can cause some changes to the tablet physical and chemical properties. Furthermore, a detailed review is provided on the methodologies used to characterize lubrication process during tablet compression with relevant process analytical technologies. Finally, the Quality-by-Design considerations for tablet formulation and process development in terms of lubrication are discussed.

  9. Birth accelerations of neutron stars

    NASA Astrophysics Data System (ADS)

    Heras, Ricardo

    2013-03-01

    We suggest that neutron stars experienced at birth three related physical changes, which may originate in magneto-rotational instabilities: (i) an increase in period from the initial value P 0 to the current value Ps , implying a change of rotational energy Δ E rot; (ii) an exponential decay of its magnetic field from the initial value B 0 to the current surface value Bs , implying a change of radiative energy Δ E rad; and (iii) an increase of space velocity from the initial value v 0 to the current value v, implying a change of kinetic energy Δ E kin. These changes are assumed to be connected by Δ E rad + Δ E kin = Δ E rot. This means that the radiation loss and increase of kinetic energy are both at the expense of a rotational energy loss. It is shown that this energy conversion occurs during times of order of 10-4 s if the neutron stars are born with magnetic fields in the range of 1015-1016 G and initial periods in range 1-20 ms. It is shown that the birth accelerations of neutron stars are of the order of 108g.

  10. BL3: A Next Generation Beam Neutron Lifetime Experiment

    NASA Astrophysics Data System (ADS)

    Wietfeldt, F. E.; Fomin, N.; Greene, G. L.; Snow, W. M.; Liu, C.-Y.; Crawford, C. B.; Korsch, W.; Plaster, B.; Jones, G. L.; Collett, B.; Dewey, M. S.

    2016-09-01

    BL3 (Beam Lifetime 3) is a proposed next generation neutron lifetime experiment using the beam method. It continues a program, spanning more than three decades, of experiments at the ILL (France) and the NIST Center for Neutron Research that achieved the most precise beam method neutron lifetime measurements to date. A collimated cold neutron beam passes through a quasi-Penning trap where recoil protons from neutron decay are trapped. Periodically the trap is opened and these protons follow a bend in the magnetic field to a silicon detector. The same neutron beam passes through a thin-foil neutron counter that measures the neutron density. The ratio of neutron and proton count rates, along with efficiency factors, gives the neutron lifetime. The main goal of BL3 is to thoroughly investigate and test systematic effects in the beam method in an effort to address the current 4 σ discrepancy between the beam and bottle methods. It will employ a much larger, higher flux neutron beam, a large area position-sensitive proton detector, and an improved magnet design, with a proton trapping rate 100 times higher than past experiments. National Science Foundation, U.S. Dept. of Energy Office of Science.

  11. Compositional terranes on Mercury: Information from fast neutrons

    NASA Astrophysics Data System (ADS)

    Lawrence, David J.; Peplowski, Patrick N.; Beck, Andrew W.; Feldman, William C.; Frank, Elizabeth A.; McCoy, Timothy J.; Nittler, Larry R.; Solomon, Sean C.

    2017-01-01

    We report measurements of the flux of fast neutrons at Mercury from 20ºS to the north pole. On the basis of neutron transport simulations and remotely sensed elemental compositions, cosmic-ray-induced fast neutrons are shown to provide a measure of average atomic mass, , a result consistent with earlier studies of the Moon and Vesta. The dynamic range of fast neutron flux at Mercury is 3%, which is smaller than the fast-neutron dynamic ranges of 30% and 6% at the Moon and Vesta, respectively. Fast-neutron data delineate compositional terranes on Mercury that are complementary to those identified with X-ray, gamma-ray, and slow-neutron data. Fast neutron measurements confirm the presence of a region with high , relative to the mean for the planet, that coincides with the previously identified high-Mg region and reveal the existence of at least two additional compositional terranes: a low- region within the northern smooth plains and a high- region near the equator centered near 90ºE longitude. Comparison of the fast-neutron map with elemental composition maps show that variations predicted from the combined element maps are not consistent with the measured variations in fast-neutron flux. This lack of consistency could be due to incomplete coverage for some elements or uncertainties in the interpretations of compositional and neutron data. Currently available data and analyses do not provide sufficient constraints to resolve these differences.

  12. Improving neutron dosimetry using bubble detector technology

    SciTech Connect

    Buckner, M.A.

    1993-02-01

    Providing accurate neutron dosimetry for a variety of neutron energy spectra is a formidable task for any dosimetry system. Unless something is known about the neutron spectrum prior to processing the dosimeter, the calculated dose may vary greatly from that actually encountered; that is until now. The entrance of bubble detector technology into the field of neutron dosimetry has eliminated the necessity of having an a priori knowledge of the neutron energy spectra. Recently, a new approach in measuring personnel neutron dose equivalent was developed at Oak Ridge National Laboratory. By using bubble detectors in combination with current thermoluminescent dosimeters (TLDs) as a Combination Personnel Neutron Dosimeter (CPND), not only is it possible to provide accurate dose equivalent results, but a simple four-interval neutron energy spectrum is obtained as well. The components of the CPND are a Harshaw albedo TLD and two bubble detectors with theoretical energy thresholds of 100 key and 1500 keV. Presented are (1) a synoptic history surrounding emergence of bubble detector technology, (2) a brief overview of the current theory on mechanisms of interaction, (3) the data and analysis process involved in refining the response functions, (4) performance evaluation of the original CPND and a reevaluation of the same data under the modified method, (5) the procedure used to determine the reference values of component fluence and dose equivalent for field assessment, (6) analysis of the after-modification results, (7) a critique of some currently held assumptions, offering some alternative explanations, and (8) thoughts concerning potential applications and directions for future research.

  13. Improving neutron dosimetry using bubble detector technology

    SciTech Connect

    Buckner, M.A.

    1993-02-01

    Providing accurate neutron dosimetry for a variety of neutron energy spectra is a formidable task for any dosimetry system. Unless something is known about the neutron spectrum prior to processing the dosimeter, the calculated dose may vary greatly from that actually encountered; that is until now. The entrance of bubble detector technology into the field of neutron dosimetry has eliminated the necessity of having an a priori knowledge of the neutron energy spectra. Recently, a new approach in measuring personnel neutron dose equivalent was developed at Oak Ridge National Laboratory. By using bubble detectors in combination with current thermoluminescent dosimeters (TLDs) as a Combination Personnel Neutron Dosimeter (CPND), not only is it possible to provide accurate dose equivalent results, but a simple four-interval neutron energy spectrum is obtained as well. The components of the CPND are a Harshaw albedo TLD and two bubble detectors with theoretical energy thresholds of 100 key and 1500 keV. Presented are (1) a synoptic history surrounding emergence of bubble detector technology, (2) a brief overview of the current theory on mechanisms of interaction, (3) the data and analysis process involved in refining the response functions, (4) performance evaluation of the original CPND and a reevaluation of the same data under the modified method, (5) the procedure used to determine the reference values of component fluence and dose equivalent for field assessment, (6) analysis of the after-modification results, (7) a critique of some currently held assumptions, offering some alternative explanations, and (8) thoughts concerning potential applications and directions for future research.

  14. 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.

  15. Ionization signals from diamond detectors in fast-neutron fields

    NASA Astrophysics Data System (ADS)

    Weiss, C.; Frais-Kölbl, H.; Griesmayer, E.; Kavrigin, P.

    2016-09-01

    In this paper we introduce a novel analysis technique for measurements with single-crystal chemical vapor deposition (sCVD) diamond detectors in fast-neutron fields. This method exploits the unique electronic property of sCVD diamond sensors that the signal shape of the detector current is directly proportional to the initial ionization profile. In fast-neutron fields the diamond sensor acts simultaneously as target and sensor. The interaction of neutrons with the stable isotopes 12 C and 13 C is of interest for fast-neutron diagnostics. The measured signal shapes of detector current pulses are used to identify individual types of interactions in the diamond with the goal to select neutron-induced reactions in the diamond and to suppress neutron-induced background reactions as well as γ-background. The method is verified with experimental data from a measurement in a 14.3 MeV neutron beam at JRC-IRMM, Geel/Belgium, where the 13C(n, α)10Be reaction was successfully extracted from the dominating background of recoil protons and γ-rays and the energy resolution of the 12C(n, α)9Be reaction was substantially improved. The presented analysis technique is especially relevant for diagnostics in harsh radiation environments, like fission and fusion reactors. It allows to extract the neutron spectrum from the background, and is particularly applicable to neutron flux monitoring and neutron spectroscopy.

  16. Neutron beam design, development, and performance for neutron capture therapy

    SciTech Connect

    Harling, O.K.; Bernard, J.A. ); Zamenhof, R.G. )

    1990-01-01

    The report presents topics presented at a workshop on neutron beams and neutron capture therapy. Topics include: neutron beam design; reactor-based neutron beams; accelerator-based neutron beams; and dosimetry and treatment planning. Individual projects are processed separately for the databases. (CBS)

  17. Replica neutron guides for experiments with ultracold neutrons

    NASA Astrophysics Data System (ADS)

    Serebrov, A. P.; Vasil'ev, A. V.; Lasakov, M. S.; Siber, E. V.; Murashkin, A. N.; Egorov, A. I.; Fomin, A. K.; Sbitnev, S. V.; Geltenbort, P.; Zimmer, O.

    2017-01-01

    The method for producing neutron guides for ultracold neutrons based on the replica method has been described. A comparative analysis of the quality of replica neutron guides, neutron guides made from polished anode-mechanical steel tubes, and neutron guides from electropolished tubes has been given.

  18. Neutron Stars and NuSTAR

    NASA Astrophysics Data System (ADS)

    Bhalerao, Varun

    2012-05-01

    My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses

  19. Overview of neutron radiology

    SciTech Connect

    Berger, H.

    1993-12-31

    Neutron radiography is a recognized method for nondestructive testing (NDT). It is one of eight established NDT methods offered for certification by ASNT. There are ASTM standards describing selected characteristics associated with neutron radiography, as discussed later in this session. Neutron radiography standards are proceeding in the international community (International Organization for Standardization, ISO). A primary advantage of using neutrons for radiologic inspection follows from the fact that the attenuation of thermal neutrons is very different from that of X-rays. A comparison of the attenuation of the elements for thermal neutrons (small dots) and 125 kV X-rays (solid line) is shown. As opposed to the increasing attenuation with increasing atomic number (Z) for X-rays, the neutron attenuation pattern is scattered. If there is a pattern for the neutrons, it tends to be the reverse of the X-ray case, namely, high neutron attenuation for light materials, such as hydrogen, lithium, and boron (H, Li, and B) and low attenuation for the heavy materials, such as lead, bismuth, and uranium (Pb, Bi, and U). The capability of thermal neutrons to image low-Z material, particularly hydrogen, in metal assemblies is in sharp contrast to that of X-rays. This opens up many practical inspection applications involving, for example, explosives, adhesives, corrosion, water intrusion, and hydriding of metals.

  20. Neutron flux characterization of californium-252 Neutron Research Facility at the University of Texas - Pan American by nuclear analytical technique

    NASA Astrophysics Data System (ADS)

    Wahid, Kareem; Sanchez, Patrick; Hannan, Mohammad

    2014-03-01

    In the field of nuclear science, neutron flux is an intrinsic property of nuclear reaction facilities that is the basis for experimental irradiation calculations and analysis. In the Rio Grande Valley (Texas), the UTPA Neutron Research Facility (NRF) is currently the only neutron facility available for experimental research purposes. The facility is comprised of a 20-microgram californium-252 neutron source surrounded by a shielding cascade containing different irradiation cavities. Thermal and fast neutron flux values for the UTPA NRF have yet to be fully investigated and may be of particular interest to biomedical studies in low neutron dose applications. Though a variety of techniques exist for the characterization of neutron flux, neutron activation analysis (NAA) of metal and nonmetal foils is a commonly utilized experimental method because of its detection sensitivity and availability. The aim of our current investigation is to employ foil activation in the determination of neutron flux values for the UTPA NSRF for further research purposes. Neutron spectrum unfolding of the acquired experimental data via specialized software and subsequent comparison for consistency with computational models lends confidence to the results.

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

    PubMed

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

    2014-12-01

    A new deuterium-deuterium (D-D) neutron generator has been developed by Adelphi Technology for prompt gamma neutron activation analysis (PGNAA), neutron activation analysis (NAA), and fast neutron radiography. The generator makes an excellent fast, intermediate, and thermal neutron source for laboratories and industrial applications that require the safe production of neutrons, a small footprint, low cost, and small regulatory burden. The generator has three major components: a Radio Frequency Induction Ion Source, a Secondary Electron Shroud, and a Diode Accelerator Structure and Target. Monoenergetic neutrons (2.5MeV) are produced with a yield of 10(10)n/s using 25-50mA of deuterium ion beam current and 125kV of acceleration voltage. The present study characterizes the performance of the neutron generator with respect to neutron yield, neutron production efficiency, and the ionic current as a function of the acceleration voltage at various RF powers. In addition the Monte Carlo N-Particle Transport (MCNP) simulation code was used to optimize the setup with respect to thermal flux and radiation protection. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Z-pinch plasma neutron sources

    SciTech Connect

    Velikovich, A. L.; Clark, R. W.; Davis, J.; Chong, Y. K.; Deeney, C.; Coverdale, C. A.; Ruiz, C. L.; Cooper, G. W.; Nelson, A. J.; Franklin, J.; Rudakov, L. I.

    2007-02-15

    A deuterium gas-puff load imploded by a multi-MA current driver from a large initial diameter could be a powerful source of fusion neutrons, a plasma neutron source (PNS). Unlike the beam-target neutrons produced in Z-pinch plasmas in the 1950s and deuterium-fiber experiments in the 1980s, the neutrons generated in deuterium gas-puffs with current levels achieved in recent experiments on the Z facility at Sandia National Laboratories could contain a substantial fraction of thermonuclear origin. For recent deuterium gas-puff shots on Z, our analytic estimates and one- and two-dimensional simulations predict thermal neutron yields {approx}3x10{sup 13}, in fair agreement with the yields recently measured on Z [C. A. Coverdale et al., Phys. Plasmas (to be published)]. It is demonstrated that the hypothesis of a beam-target origin of the observed fusion neutrons implies a very high Z-pinch-driver-to-fast-ions energy transfer efficiency, 5 to 10%, which would make a multi-MA deuterium Z-pinch the most efficient light-ion accelerator. No matter what mechanism is eventually determined to be responsible for generating fusion neutrons in deuterium gas-puff shots on Z, the deuterium neutron yield is shown to scale as Y{sub n}{approx}I{sub m}{sup 4}, where I{sub m} is the peak current of the pinch. Theoretical estimates and numerical modeling of deuterium gas-puff implosions demonstrate that the yields of thermonuclear fusion neutrons that can be produced on ZR and the next-generation machines are sufficiently high to make PNS the most powerful, cost- and energy-efficient laboratory sources of 2.5-14 MeV fusion neutrons, just like plasma radiation sources are the most powerful sources of soft and keV x rays. In particular, the predicted deuterium-tritium thermal neutron-producing capability of PNS driven by the next-generation ZR and ZX accelerators is {approx}5x10{sup 16} and {approx}10{sup 18}, respectively.

  3. Neutron and high speed photogrammetric arcjet diagnosis

    NASA Technical Reports Server (NTRS)

    Stewart, P. A. E.; Rogers, J. D.; Fowler, P. H.; Deininger, W. D.; Taylor, A. D.

    1989-01-01

    Two methods for real time internal diagnostics of arcjet engines are described. One method uses cold, thermal, or epithermal neutrons. Cold neutrons are used to detect the presence and location of hydrogenous propellants. Thermal neutrons are used to delineate the edge contours of anode and cathode surfaces and to measure stress/strain. Epithermal neutrons are used to measure temperatures on arcjet surfaces, bulk material temperatures, and point temperatures in bulk materials. It is found that this method, with an exposure time of 10 min, produces at temperature accuracy for W or Re of + or - 2.5 C. The other method uses visible-light high-speed photogrammetry to obtain images of the transient behavior of the arc during start-up and to relate this behavior to electrial supply characteristics such as voltage, current, and ripple.

  4. Advanced digital detectors for neutron imaging.

    SciTech Connect

    Doty, F. Patrick

    2003-12-01

    Neutron interrogation provides unique information valuable for Nonproliferation & Materials Control and other important applications including medicine, airport security, protein crystallography, and corrosion detection. Neutrons probe deep inside massive objects to detect small defects and chemical composition, even through high atomic number materials such as lead. However, current detectors are bulky gas-filled tubes or scintillator/PM tubes, which severely limit many applications. Therefore this project was undertaken to develop new semiconductor radiation detection materials to develop the first direct digital imaging detectors for neutrons. The approach relied on new discovery and characterization of new solid-state sensor materials which convert neutrons directly to electronic signals via reactions BlO(n,a)Li7 and Li6(n,a)T.

  5. 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.

  6. 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.

  7. Neutrino Processes in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Kolomeitsev, E. E.; Voskresensky, D. N.

    2010-10-01

    included within the Green’s function formalism. Softening of the pion mode with an baryon density increase is explicitly incorporated. We show examples of inconsistencies in calculations without inclusion of medium effects. Then we demonstrate calculations of different reaction rates in non-superfluid nuclear matter with taking into account medium effects. Many new reaction channels are open up in the medium and should be analyzed. Part IV: We discuss the neutrino production reactions in superfluid nuclear systems. The reaction rates of processes associated with the pair breaking and formation are calculated. Special attention is focused on the gauge invariance and the exact fulfillment of the Ward identities for the vector current. Finally we present comparison of calculations of neutron star cooling performed within nuclear medium cooling scenario with the available data.

  8. Accelerator-based epithermal neutron sources for boron neutron capture therapy of brain tumors.

    PubMed

    Blue, Thomas E; Yanch, Jacquelyn C

    2003-01-01

    This paper reviews the development of low-energy light ion accelerator-based neutron sources (ABNSs) for the treatment of brain tumors through an intact scalp and skull using boron neutron capture therapy (BNCT). A major advantage of an ABNS for BNCT over reactor-based neutron sources is the potential for siting within a hospital. Consequently, light-ion accelerators that are injectors to larger machines in high-energy physics facilities are not considered. An ABNS for BNCT is composed of: (1) the accelerator hardware for producing a high current charged particle beam, (2) an appropriate neutron-producing target and target heat removal system (HRS), and (3) a moderator/reflector assembly to render the flux energy spectrum of neutrons produced in the target suitable for patient irradiation. As a consequence of the efforts of researchers throughout the world, progress has been made on the design, manufacture, and testing of these three major components. Although an ABNS facility has not yet been built that has optimally assembled these three components, the feasibility of clinically useful ABNSs has been clearly established. Both electrostatic and radio frequency linear accelerators of reasonable cost (approximately 1.5 M dollars) appear to be capable of producing charged particle beams, with combinations of accelerated particle energy (a few MeV) and beam currents (approximately 10 mA) that are suitable for a hospital-based ABNS for BNCT. The specific accelerator performance requirements depend upon the charged particle reaction by which neutrons are produced in the target and the clinical requirements for neutron field quality and intensity. The accelerator performance requirements are more demanding for beryllium than for lithium as a target. However, beryllium targets are more easily cooled. The accelerator performance requirements are also more demanding for greater neutron field quality and intensity. Target HRSs that are based on submerged-jet impingement and

  9. Measurement of the neutron spectrum and ambient neutron dose rate equivalent from the small 252Cf source at 1 meter

    SciTech Connect

    Radev, R.

    2015-07-07

    NASA Langley Research Center requested a measurement of the neutron spectral distribution and fluence from the 252Cf source (model NS-120, LLNL serial # 7001677, referred as the SMALL Cf source) and determination of the ambient neutron dose rate equivalent and kerma at 100 cm for the Radiation Budget Instrument Experiment (Rad-X). The dosimetric quantities should be based on the neutron spectrum and the current neutron-to-dose conversion coefficients.

  10. Neutron radiography using neutron imaging plate.

    PubMed

    Chankow, Nares; Punnachaiya, Suvit; Wonglee, Sarinrat

    2010-01-01

    The aims of this research are to study properties of a neutron imaging plate (NIP) and to test it for use in nondestructive testing (NDT) of materials. The experiments were carried out by using a BAS-ND 2040 Fuji NIP and a neutron beam from the Thai Research Reactor TRR-1/M1. The neutron intensity and Cd ratio at the specimen position were approximately 9x10(5) ns/cm(2) s and 100 respectively. It was found that the photostimulated luminescence (PSL) readout of the imaging plate was directly proportional to the exposure time and approximately 40 times faster than the conventional NR using Gd converter screen/X-ray film technique. The sensitivities of the imaging plate to slow neutron and to Ir-192 gamma-rays were found to be approximately 4.2x10(-3) PSL/mm(2) per neutron and 6.7x10(-5) PSL/mm(2) per gamma-ray photon respectively. Finally, some specimens containing light elements were selected to be radiographed with neutrons using the NIP and the Gd converter screen/X-ray film technique. The image quality obtained from the two recording media was found to be comparable. Crown Copyright 2009. Published by Elsevier Ltd. All rights reserved.

  11. Status of the LEgnaro NeutrOn Source facility (LENOS)

    NASA Astrophysics Data System (ADS)

    Mastinu, Pierfrancesco; Praena, J.; Martìn-Hernàndez, G.; Dzysiuk, N.; Prete, G.; Capote, R.; Pignatari, M.; Ventura, A.

    LENOS is a new facility under development at Laboratori Nazionali di Legnaro (LNL). It is based on a new technic for neutron beam shaping in accelerator based neutron sources. The main advantage of this method is to be able to shape the primary charged-particle beam to a defined energy distribution that, impinging on a neutron producing target, generates the desired neutron spectra at the sample position. Together with the proton energy distribution, other degrees of freedom are used to obtain the desired neutron energy spectra, e.g. the angular distribution of produced neutrons, the nuclear reactions used for the neutron spectra production, and the convolution of neutron spectra coming from different target materials. The main advantage of this new approach is the good control over the energy and spatial distribution of the produced neutron spectrum avoiding most of the problems due to neutron moderation, since it is easier to work with charged particles than with neutrons. The goal of the LENOS facility is to obtain a Maxwell-Boltzmann neutron energy spectrum with tunable temperature and a high neutron flux at sample position by using the 7Li(p,n) reaction. To maximize the neutron flux a very narrow primary proton beam has to be used, so the target has to remove a very high specific power. Currently available lithium targets are inadequate to sustain the high specific power that needs to be dissipated in the LENOS facility. A dedicated target based on micro-channel geometry and liquid metal cooling has been developed and tested. This contribution describes the status of the LENOS facility.

  12. Italian neutron sources

    NASA Astrophysics Data System (ADS)

    Prata, M.; Alloni, D.; De Felice, P.; Palomba, M.; Pietropaolo, A.; Pillon, M.; Quintieri, L.; Santagata, A.; Valente, P.

    2014-11-01

    Many research activities, instrumental analysis, studies of radiation damage, etc., require neutron sources. The main neutron sources present in Italy are described in three different sections: nuclear research reactors, accelerator driven, and metrology stations. The nuclear research reactors of LENA (University of Pavia) and ENEA Casaccia are described in terms of irradiation facilities available, neutron flux for each of them and the main activities carried out by each research centre. In the second section, the Frascati Neutron Generator (FNG), the Frascati Beam-Test Facility (BTF) and their main features are reported. In the last section there is a detailed description of the institutional role and the main activities carried out in the field of neutron metrology by the National Institute for Metrology of Ionizing Radiation (INMRI) with a brief description of neutron sources of which the institute is endowed.

  13. Optimization of a neutron detector design using adjoint transport simulation

    SciTech Connect

    Yi, C.; Manalo, K.; Huang, M.; Chin, M.; Edgar, C.; Applegate, S.; Sjoden, G.

    2012-07-01

    A synthetic aperture approach has been developed and investigated for Special Nuclear Materials (SNM) detection in vehicles passing a checkpoint at highway speeds. SNM is postulated to be stored in a moving vehicle and detector assemblies are placed on the road-side or in chambers embedded below the road surface. Neutron and gamma spectral awareness is important for the detector assembly design besides high efficiencies, so that different SNMs can be detected and identified with various possible shielding settings. The detector assembly design is composed of a CsI gamma-ray detector block and five neutron detector blocks, with peak efficiencies targeting different energy ranges determined by adjoint simulations. In this study, formulations are derived using adjoint transport simulations to estimate detector efficiencies. The formulations is applied to investigate several neutron detector designs for Block IV, which has its peak efficiency in the thermal range, and Block V, designed to maximize the total neutron counts over the entire energy spectrum. Other Blocks detect different neutron energies. All five neutron detector blocks and the gamma-ray block are assembled in both MCNP and deterministic simulation models, with detector responses calculated to validate the fully assembled design using a 30-group library. The simulation results show that the 30-group library, collapsed from an 80-group library using an adjoint-weighting approach with the YGROUP code, significantly reduced the computational cost while maintaining accuracy. (authors)

  14. [Fast neutron cross section measurements

    SciTech Connect

    Knoll, G.F.

    1992-10-26

    From its inception, the Nuclear Data Project at the University of Michigan has concentrated on two major objectives: (1) to carry out carefully controlled nuclear measurements of the highest possible reliability in support of the national nuclear data program, and (2) to provide an educational opportunity for students with interests in experimental nuclear science. The project has undergone a successful transition from a primary dependence on our photoneutron laboratory to one in which our current research is entirely based on a unique pulsed 14 MeV fast neutron facility. The new experimental facility is unique in its ability to provide nanosecond bursts of 14 MeV neutrons under conditions that are clean'' and as scatter-free as possible, and is the only one of its type currently in operation in the United States. It has been designed and put into operation primarily by graduate students, and has met or exceeded all of its important initial performance goals. We have reached the point of its routine operation, and most of the data are now in hand that will serve as the basis for the first two doctoral dissertations to be written by participating graduate students. Our initial results on double differential neutron cross sections will be presented at the May 1993 Fusion Reactor Technology Workshop. We are pleased to report that, after investing several years in equipment assembly and optimization, the project has now entered its data production'' phase.

  15. Reality in neutron interference experiments

    SciTech Connect

    Rauch, H. )

    1993-01-01

    The wave-particle dualism becomes very obvious in matter wave interference experiments. Neutron interferometers based on wave front and amplitude division have been developed in the past. Most experiments have been performed with the perfect crystal neutron interferometer, which provides widely separated coherent beams allowing new experiments in the field of fundamental, nuclear, and solid-state physics. A nondispersive sample arrangement and the difference of stochastic and deterministic absorption have been investigated. In case of a deterministic absorption process the attenuation of the interference pattern is proportional to the beam attenuation, whereas in case of stochastic absorption it is proportional to the square root of the attenuation. This permits the formulation of Bell-like inequalities which will be discussed in detail. The verification of the 4[pi] symmetry of spinors and of the quantum mechanical spin-superposition experiment on a macroscopic scale are typical examples of interferometry in spin space. These experiments were continued with two resonance coils in the beams, where the results showed that coherence persists, even it an energy exchange between the neutron and the resonator system occurs with certainty. A quantum beat effect was observed when slightly different resonance frequencies were applied to both beams. In this case, the extremely high energy sensitivity of 2.7 [times] 10[sup [minus]19] eV was achieved. This effect can be interpreted as a magnetic Josephson-effect analog. Phase echo systems and experiments with pulsed beams show how interference phenomena can be made visible by a proper beam handling inside and behind the interferometer. All the results obtained until now are in agreement with the formalism of quantum mechanics but stimulate the discussion about the interpretation of this basic theory.

  16. The advanced neutron source

    SciTech Connect

    Raman, S.; Hayter, J.B.

    1990-01-01

    The Advanced Neutron Source (ANS) is a new user experimental facility planned to be operational at Oak Ridge in the late 1990's. The centerpiece of the ANS will be a steady-state research reactor of unprecedented thermal neutron flux ({phi}{sub th} {approx} 8 {times} 10{sup 19} m{sup {minus}2} {center dot}s{sup {minus}1}) accompanied by extensive and comprehensive equipment and facilities for neutron-based research.

  17. The Advanced Neutron Source

    SciTech Connect

    Hayter, J.B.

    1989-01-01

    The Advanced Neutron Source (ANS) is a new user experimental facility planned to be operational at Oak Ridge in the late 1990's. The centerpiece of the ANS will be a steady-state research reactor of unprecedented thermal neutron flux ({phi}{sub th} {approx} 9{center dot}10{sup 19} m{sup -2}{center dot}s{sup -1}) accompanied by extensive and comprehensive equipment and facilities for neutron-based research. 5 refs., 5 figs.

  18. The DIORAMA Neutron Emitter

    SciTech Connect

    Terry, James Russell

    2016-05-05

    Emission of neutrons in a given event is modeled by the DioramaEmitterNeutron object, a subclass of the abstract DioramaEmitterModule object. The GenerateEmission method of this object is the entry point for generation of a neutron population for a given event. Shown in table 1, this method requires a number of parameters to be defined in the event definition.

  19. Portable Neutron Source

    DTIC Science & Technology

    2008-05-30

    distribution were studied as a function of peak laser intensity, laser pulse duration and primary target thickness. The proposed scheme for neutron ...Fig. 2. The next step is to calculate the neutron yield from the ion beam-target deposition model. The secondary target is a thick (~ 1mm) slab of...specific directions of observations. Figure 4 displays a typical angular distribution function of neutrons from a CD2 target. In Fig. 4 we plot the

  20. Neutron radiographic viewing system

    NASA Technical Reports Server (NTRS)

    1972-01-01

    The design, development and application of a neutron radiographic viewing system for use in nondestructive testing applications is considered. The system consists of a SEC vidicon camera, neutron image intensifier system, disc recorder, and TV readout. Neutron bombardment of the subject is recorded by an image converter and passed through an optical system into the SEC vidicon. The vidicon output may be stored, or processed for visual readout.

  1. Neutron absorptiometric titration.

    PubMed

    Tölgyessy, J; Varga, S; Dillinger, P

    1967-03-01

    A method is outlined for detection of two-phase titration end-points by means of an abrupt change in the neutron-absorption characteristics of one of the phases. One of the components of the precipitate must have a large neutron absorption cross-section, and the disappearance or appearance of neutron absorption by the supernatant liquid from the precipitation reaction then marks the completion of precipitation.

  2. Neutron cross sections

    SciTech Connect

    Not Available

    1988-01-01

    This handbook displays curves of neutron cross sections in the energy range of 0.01 eV to 200 MeV (and associated information) as a function of incident neutron energy. Tables include reference to all data. Information on isomeric state production is also included. This book represents the fourth edition of what was previously known as BNL-325, Neutron Cross Sections, Volume 2, the third edition of which was published in 1976.

  3. 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.

  4. Simulations towards optimization of a neutron/anti-neutron oscillation experiment at the European Spallation Source

    NASA Astrophysics Data System (ADS)

    Frost, Matthew; Kamyshkov, Yuri; Castellanos, Luis; Klinkby, Esben; US NNbar Collaboration

    2015-04-01

    The observation of Neutron/Anti-neutron oscillation would prove the existence of Baryon Number Violation (BNV), and thus an explanation for the dominance of matter over anti-matter in the universe. The latest experiments have shown the oscillation time to be greater than 8.6 x 107 seconds, whereas current theoretical predictions suggest times on the order of 108 to 109 seconds. A neutron oscillation experiment proposed at the European Spallation Source (ESS) would provide sensitivity of more than 1000 times previous experiments performed, thus providing a result well-suited to confirm or deny current theory. A conceptual design of the proposed experiment will be presented, as well as the optimization of key experiment components using Monte-Carlo simulation methods, including the McStas neutron ray-trace simulation package. This work is supported by the Organized Research Units Program funded by The University of Tennessee, Knoxville Office of Research and Engagement.

  5. Advanced Neutron Source enrichment study

    SciTech Connect

    Bari, R.A.; Ludewig, H.; Weeks, J.R.

    1994-12-31

    A study has been performed of the impact on performance of using low enriched uranium (20% {sup 235}U) or medium enriched uranium (35% {sup 235}U) as an alternative fuel for the Advanced Neutron Source, which is currently designed to use uranium enriched to 93% {sup 235}U. Higher fuel densities and larger volume cores were evaluated at the lower enrichments in terms of impact on neutron flux, safety, safeguards, technical feasibility, and cost. The feasibility of fabricating uranium silicide fuel at increasing material density was specifically addressed by a panel of international experts on research reactor fuels. The most viable alternative designs for the reactor at lower enrichments were identified and discussed. Several sensitivity analyses were performed to gain an understanding of the performance of the reactor at parametric values of power, fuel density, core volume, and enrichment that were interpolations between the boundary values imposed on the study or extrapolations from known technology.

  6. ANS cold source neutronics analysis

    SciTech Connect

    Lillie, R.A.

    1994-06-01

    This paper describes the calculational procedures employed in the ongoing neutronics analysis of the ANS cold source and presents in chronological order some of the more important results from the one- and two-dimensional discrete calculations performed to date in support of the ANS cold source design. In particular, cold neutron currents from cryostat shapes which can be adequately modeled with two-dimensional geometries are compared with and without reentrant cavities. Also, results are presented from one-dimensional comparative liquid hydrogen vs liquid deuterium calculations in which the density, placement, and para-ortho mixture of liquid hydrogen is investigated. In addition, the evolution of the ANS conceptual design cold source from an initial short cylindrical cryostat with hemispherical upper and lower heads employing a natural convection liquid deuterium circulation system to the final spherical design employing a pumped system is described. Finally, performance data and heating rates are presented for some possible alternate ANS cryostat and vacuum jacket materials.

  7. 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.

  8. 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.

  9. Probing the Potential of Neutron Imaging for Biomedical and Biological Applications

    NASA Astrophysics Data System (ADS)

    Watkin, K. L.; Bilheux, H. Z.; Ankner, J. F.

    Neutron imaging of biological specimens began soon after the discovery of the neutron by Chadwick in 1932. The first samples included tumors in tissues, internal organs in rats, and bones. These studies mainly employed thermal neutrons and were often compared with X-ray images of the same or equivalent samples. Although neutron scattering is widely used in biological studies, neutron imaging has yet to be exploited to its full capability in this area. This chapter summarizes past and current research efforts to apply neutron radiography to the study of biological specimens, in the expectation that clinical and medical research, as well as forensic science, may benefit from it.

  10. Probing the potential of neutron imaging for biomedical and biological applications

    SciTech Connect

    Watkin, Kenneth L; Bilheux, Hassina Z; Ankner, John Francis

    2009-01-01

    Neutron imaging of biological specimens began soon after the discovery of the neutron by Chadwick in 1932. The first samples included tumors in tissues, internal organs in rats, and bones. These studies mainly employed thermal neutrons and were often compared with X-ray images of the same or equivalent samples. Although neutron scattering is widely used in biological studies, neutron imaging has yet to be exploited to its full capability in this area. This chapter summarizes past and current research efforts to apply neutron radiography to the study of biological specimens, in the expectation that clinical and medical research, as well as forensic science, may benefit from it.

  11. Burst Oscillations: A New Spin on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2007-01-01

    Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the X-ray flux during thermonuclear X-ray bursts fr-om accreting neutron stars is often strongly pulsed at frequencies as high as 620 Hz. We now know that these oscillations are produced by spin modulation of the thermonuclear flux from the neutron star surface. In addition to revealing the spin frequency, they provide new ways to probe the properties and physics of accreting neutron stars. I will briefly review our current observational and theoretical understanding of these oscillations and discuss what they are telling us about neutron stars.

  12. Burst Oscillations: A New Spin on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2007-01-01

    Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the X-ray flux during thermonuclear X-ray bursts fr-om accreting neutron stars is often strongly pulsed at frequencies as high as 620 Hz. We now know that these oscillations are produced by spin modulation of the thermonuclear flux from the neutron star surface. In addition to revealing the spin frequency, they provide new ways to probe the properties and physics of accreting neutron stars. I will briefly review our current observational and theoretical understanding of these oscillations and discuss what they are telling us about neutron stars.

  13. Merger of binary neutron stars: Gravitational waves and electromagnetic counterparts

    NASA Astrophysics Data System (ADS)

    Shibata, Masaru

    2016-12-01

    Late inspiral and merger phases of binary neutron stars are the valuable new experimental fields for exploring nuclear physics because (i) gravitational waves from them will bring information for the neutron-star equation of state and (ii) the matter ejected after the onset of the merger could be the main site for the r-process nucleosynthesis. We will summarize these aspects of the binary neutron stars, describing the current understanding for the merger process of binary neutron stars that has been revealed by numerical-relativity simulations.

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

    PubMed

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

    2012-03-16

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

  15. Novel neutron sources at the Radiological Research Accelerator Facility

    PubMed Central

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

    2012-01-01

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

  16. Novel neutron sources at the Radiological Research Accelerator Facility

    SciTech Connect

    Xu, Yanping; Garty, G.; Marino, S. A.; Massey, Thomas Neal; Johnson, G. W.; Randers-Pehrson, Gerhard; Brenner, D. J.

    2012-03-16

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

  17. Novel neutron sources at the Radiological Research Accelerator Facility

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  18. D-D neutron generator development at LBNL.

    PubMed

    Reijonen, J; Gicquel, F; Hahto, S K; King, M; Lou, T-P; Leung, K-N

    2005-01-01

    The plasma and ion source technology group in Lawrence Berkeley National Laboratory is developing advanced, next generation D-D neutron generators. There are three distinctive developments, which are discussed in this presentation, namely, multi-stage, accelerator-based axial neutron generator, high-output co-axial neutron generator and point source neutron generator. These generators employ RF-induction discharge to produce deuterium ions. The distinctive feature of RF-discharge is its capability to generate high atomic hydrogen species, high current densities and stable and long-life operation. The axial neutron generator is designed for applications that require fast pulsing together with medium to high D-D neutron output. The co-axial neutron generator is aimed for high neutron output with cw or pulsed operation, using either the D-D or D-T fusion reaction. The point source neutron generator is a new concept, utilizing a toroidal-shaped plasma generator. The beam is extracted from multiple apertures and focus to the target tube, which is located at the middle of the generator. This will generate a point source of D-D, T-T or D-T neutrons with high output flux. The latest development together with measured data will be discussed in this article.

  19. Neutron polycapillary optics: present status and future trends

    NASA Astrophysics Data System (ADS)

    Ioffe, A.

    2005-07-01

    Up to present, neutron applications of polycapillary optics have been rather rear and mostly limited either to feasibility studies or to non-scattering techniques. The practical use of polycapillary focusing neutron optics for purposes of neutron scattering have been hindered by a serious degradation of momentum resolution caused by increased divergence of focused beams. However, limited size of samples available for research as well as limited brightness of present day neutron sources (both reactors and spallation sources) requires to rethink the current situation. Neutron lenses are successfully tested for low Q-resolution applications providing an enormous increase of neutron flux at small samples. Moreover, some recent developments in the field of neutron instrumentation allow us to overcome the resolution problem by decoupling the angular resolution and the incident beam divergence thus opening the opportunity for the use of focusing neutron optics in some high Q-resolution application. Further advances in technology required to improve the performance of neutron polycapillary optics, also in combination with modem methods of polarization of neutron beams, are discussed.

  20. Novel neutron sources at the Radiological Research Accelerator Facility

    DOE PAGES

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

    2012-03-16

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

  1. Control of kinematics of neutrons in a coaxial magnetic trap

    SciTech Connect

    Rivlin, Lev A

    2011-12-31

    We discuss the physical basis of how to control changes in basic kinematic parameters of neutrons (energy, velocity, density, etc.) through variation in the current of a coaxial magnetic trap containing neutrons. We present quantitative assessment of possible changes in the parameters by several orders of magnitude and outline potentials and prospects for application of the approach discussed.

  2. Neutron Capture Experiments Using the DANCE Array at Los Alamos

    SciTech Connect

    Dashdorj, D.; Mitchell, G. E.; Baramsai, B.; Chyzh, A.; Walker, C.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krticka, M.; Becvar, F.

    2009-03-31

    The Detector for Advanced Neutron Capture Experiments (DANCE) is designed for neutron capture measurements on very small and/or radioactive targets. The DANCE array of 160 BaF{sub 2} scintillation detectors is located at the Lujan Center at the Los Alamos Neutron Science Center (LANSCE). Accurate measurements of neutron capture data are important for many current applications as well as for basic understanding of neutron capture. The gamma rays following neutron capture reactions have been studied by the time-of-flight technique using the DANCE array. The high granularity of the array allows measurements of the gamma-ray multiplicity. The gamma-ray multiplicities and energy spectra for different multiplicities can be measured and analyzed for spin and parity determination of the resolved resonances.

  3. SuperCDMS SNOLAB Experiment and Active Neutron Veto

    NASA Astrophysics Data System (ADS)

    Chen, Yu

    2014-03-01

    The SuperCDMS SNOLAB experiment will attempt direct detection of the most promising candidate for dark matter, Weakly Interacting Massive Particles (WIMPs) using cryogenically cooled germanium and silicon semiconductors that provide sub-keV thresholds and excellent rejection of most radioactivity or cosmic-ray-induced backgrounds. An active neutron veto with high efficiency for tagging neutron-induced backgrounds will not only directly reduce the neutron background rate, but also provide an in-situ measurement of the neutron activity near the dark matter target. This active veto will consist of liquid scintillator doped with an isotope with high neutron-capture cross section. I will present a brief overview of the experiment, and report in detail on the current status of simulation and prototyping of this neutron veto.

  4. Hexagonal boron nitride epitaxial layers as neutron detector materials

    NASA Astrophysics Data System (ADS)

    Li, J.; Dahal, R.; Majety, S.; Lin, J. Y.; Jiang, H. X.

    2011-10-01

    Micro-strip metal-semiconductor-metal detectors for thermal neutron sensing were fabricated from hexagonal boron nitride (hBN) epilayers synthesized by metal organic chemical vapor deposition. Experimental measurements indicated that the thermal neutron absorption coefficient and length of natural hBN epilayers are about 0.00361 μm -1 and 277 μm, respectively. A continuous irradiation with a thermal neutron beam generated an appreciable current response in hBN detectors, corresponding to an effective conversion efficiency approaching ˜80% for absorbed neutrons. Our results indicate that hBN semiconductors would enable the development of essentially ideal solid-state thermal neutron detectors in which both neutron capture and carrier collection are accomplished in the same hBN semiconductor. These solid-state detectors have the potential to replace 3He gas detectors, which faces the very serious issue of 3He gas shortage.

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

    SciTech Connect

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

    2006-09-08

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

  6. Neutron Capture Reactions on lu Isotopes at Dance

    NASA Astrophysics Data System (ADS)

    Roig, O.; Meot, V.; Daugas, J.-M.; Morel, P.; Jandel, M.; Vieira, D. J.; Bond, E. M.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Keksis, A. L.; Rundberg, R. S.; Ullmann, J. L.; Wouters, J. M.

    2013-03-01

    The DANCE1 (Detector for Advanced Neutron Capture Experiments) array at LANSCE spallation neutron source in Los Alamos has been used to obtain the neutron radiative capture cross sections for 175Lu and 176Lu with neutron energies from thermal up to 100 keV. Both isotopes are of current interest for the nucleosynthesis s-process.2,3 Three targets were used to perform these measurements. One was natural Lu foil of 31 mg/cm2 and the other two were isotope-enriched targets of 175Lu and 176Lu. Firstly, the cross sections were obtained by normalizing yield to a well-known cross section at the thermal neutron energy. Now, we want to obtain absolute cross sections of radiative capture through a precise neutron flux determination, an accurate target mass measurement and an efficiency determination of the DANCE array.

  7. Neutron Capture Experiments Using the DANCE Array at Los Alamos

    NASA Astrophysics Data System (ADS)

    Dashdorj, D.; Mitchell, G. E.; Baramsai, B.; Chyzh, A.; Walker, C.; Agvaanluvsan, U.; Becker, J. A.; Parker, W.; Sleaford, B.; Wu, C. Y.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Jandel, M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wouters, J. M.; Krtička, M.; Bečvář, F.

    2009-03-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is designed for neutron capture measurements on very small and/or radioactive targets. The DANCE array of 160 BaF2 scintillation detectors is located at the Lujan Center at the Los Alamos Neutron Science Center (LANSCE). Accurate measurements of neutron capture data are important for many current applications as well as for basic understanding of neutron capture. The gamma rays following neutron capture reactions have been studied by the time-of-flight technique using the DANCE array. The high granularity of the array allows measurements of the gamma-ray multiplicity. The gamma-ray multiplicities and energy spectra for different multiplicities can be measured and analyzed for spin and parity determination of the resolved resonances.

  8. Experimental and numerical characterization of the neutron field produced in the n@BTF Frascati photo-neutron source

    NASA Astrophysics Data System (ADS)

    Bedogni, R.; Quintieri, L.; Buonomo, B.; Esposito, A.; Mazzitelli, G.; Foggetta, L.; Gómez-Ros, J. M.

    2011-12-01

    A photo-neutron irradiation facility is going to be established at the Frascati National Laboratories of INFN on the base of the successful results of the n@BTF experiment. The photo-neutron source is obtained by an electron or positron pulsed beam, tuneable in energy, current and in time structure, impinging on an optimized tungsten target located in a polyethylene-lead shielding assembly. The resulting neutron field, through selectable collimated apertures at different angles, is released into a 100 m2 irradiation room. The neutron beam, characterized by an evaporation spectrum peaked at about 1 MeV, can be used in nuclear physics, material science, calibration of neutron detectors, studies of neutron hardness, ageing and study of single event effect. The intensity of the neutron beam obtainable with 510 MeV electrons and its fluence energy distribution at a point of reference in the irradiation room were predicted by Monte Carlo simulations and experimentally determined with a Bonner Sphere Spectrometer (BSS). Due to the large photon contribution and the pulsed time structure of the beam, passive photon-insensitive thermal neutron detectors were used as sensitive elements of the BSS. For this purpose, a set of Dy activation foils was used. This paper presents the numerical simulations and the measurements, and compares their results in terms of both neutron spectrum and total neutron fluence.

  9. Used Fuel Cask Identification through Neutron Profile

    SciTech Connect

    Rauch, Eric Benton

    2015-11-20

    Currently, most spent fuel is stored near reactors. An interim consolidated fuel storage facility would receive fuel from multiple sites and store it in casks on site for decades. For successful operation of such a facility there is need for a way to restore continuity of knowledge if lost as well as a method that will indicate state of fuel inside the cask. Used nuclear fuel is identifiable by its radiation emission, both gamma and neutron. Neutron emission from fission products, multiplication from remaining fissile material, and the unique distribution of both in each cask produce a unique neutron signature. If two signatures taken at different times do not match, either changes within the fuel content or misidentification of a cask occurred. It was found that identification of cask loadings works well through the profile of emitted neutrons in simulated real casks. Even casks with similar overall neutron emission or average counts around the circumference can be distinguished from each other by analyzing the profile. In conclusion, (1) identification of unaltered casks through neutron signature profile is viable; (2) collecting the profile provides insight to the condition and intactness of the fuel stored inside the cask; and (3) the signature profile is stable over time.

  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. LiNA - Lifetime of neutron apparatus with time projection chamber and solenoid coil

    NASA Astrophysics Data System (ADS)

    Otono, H.

    2017-02-01

    Among measurements of the neutron lifetime, there is a 1% difference between proton-counting and neutron-counting methods. In this paper, a new electron-counting method with a magnetic field aiming for a 0.1% accuracy is proposed, which would possibly allow to resolve the current discrepancy between the different neutron lifetime measurements.

  12. Neutron resonance data exclude random matrix theory

    NASA Astrophysics Data System (ADS)

    Koehler, P. E.; Bečvář, F.; Krtička, M.; Guber, K. H.; Ullmann, J. L.

    2013-02-01

    Almost since the time it was formulated, the overwhelming consensus has been that random matrix theory (RMT) is in excellent agreement with neutron resonance data. However, over the past few years, we have obtained new neutron-width data at Oak Ridge and Los Alamos National Laboratories that are in stark disagreement with this theory. We also have reanalyzed neutron widths in the most famous data set, the nuclear data ensemble (NDE), and found that it is seriously flawed, and, when analyzed carefully, excludes RMT with high confidence. More recently, we carefully examined energy spacings for these same resonances in the NDE using the $\\Delta_{3}$ statistic. We conclude that the data can be found to either confirm or refute the theory depending on which nuclides and whether known or suspected p-wave resonances are included in the analysis, in essence confirming results of our neutron-width analysis of the NDE. We also have examined radiation widths resulting from our Oak Ridge and Los Alamos measurements, and find that in some cases they do not agree with RMT. Although these disagreements presently are not understood, they could have broad impact on basic and applied nuclear physics, from nuclear astrophysics to nuclear criticality safety.

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

    SciTech Connect

    Chen, Yu

    2016-01-01

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

  14. The Neutron's Discovery - 80 Years on

    NASA Astrophysics Data System (ADS)

    Rogers, John D.

    A brief review is given of selected highlights in scientific developments from the birth of modern nuclear physics at the end of the 19th century to the discovery of the neutron in 1932. This is followed by some important milestones in neutron and reactor physics that have led to our current understanding and implementation of nuclear technologies. The beginnings can be traced back to the discovery of X-rays by Roentgen, the identification of natural radioactivity by Becquerel and the discovery of the electron by Thomson, towards the end of the 19th Century. Rutherford was a key figure in experimental physics who determined the structure of the atom and who inspired his students at McGill, Manchester and Cambridge Universities (many of whom would become Nobel laureates) in the pursuit of their physics research. One of Rutherford's students, James Chadwick, had studied the work carried out by Bothe and Becker on alpha particle-induced disintegration of light elements which had led to their observation of high energy penetrating radiation that neither they nor the Joliot-Curies could identify. Chadwick knew that the only possible explanation was the emission of a neutron in the nuclear reaction. He carried out tests in the Cavendish Laboratory and submitted his now classical paper identifying the neutron to the periodical Nature in 1932. The discovery of the neutron and of nuclear fission in 1939 opened up new areas for scientific investigation, in, for example, astrophysics, geology, neutron and nuclear physics. The prospects for nuclear power in particular appeared to be unlimited and both civil and military applications have been actively pursued. Many new experimental facilities have been designed and built to provide intense sources of neutrons for research purposes. Work carried out in such centres is included in the programme of the 7th International Topical Meeting on Neutron Radiography, an important forum for discussion of the latest research work of this

  15. Can neutron stars have auroras ? : electromagnetic coupling process between neutron star and magnetized accretion disk

    NASA Astrophysics Data System (ADS)

    Kimura, T.; Iwakiri, W. B.; Enoto, T.; Wada, T.; Tao, C.

    2015-12-01

    In the binary neutron star system, angular momentum transfer from accretion disk to a star is essential process for spin-up/down of stars. The angular momentum transfer has been well formulated for the accretion disk strongly magnetized by the neutron star [e.g., Ghosh and Lamb, 1978, 1979a, b]. However, the electromagnetic (EM) coupling between the neutron star and accretion disk has not been self-consistently solved in the previous studies although the magnetic field lines from the star are strongly tied with the accretion disk. In this study, we applied the planet-magnetosphere coupling process established for Jupiter [Hill, 1979] to the binary neutron star system. Angular momentum distribution is solved based on the torque balance between the neutron star's surface and accretion disk coupled by the magnetic field tensions. We found the EM coupling can transfer significantly larger fraction of the angular momentum from the magnetized accretion disk to the star than the unmagnetized case. The resultant spin-up rate is estimated to ~10^-14 [sec/sec] for the nominal binary system parameters, which is comparable with or larger than the other common spin-down/up processes: e.g., the magnetic dipole radiation spin-down. The Joule heating energy dissipated in the EM coupling is estimated to be up to ~10^36 [erg/sec] for the nominal binary system parameters. The release is comparable to that of gravitation energy directly caused by the matters accreting onto the neutron star. This suggests the EM coupling at the neutron star can accompany the observable radiation as auroras with a similar manner to those at the rotating planetary magnetospheres like Jupiter, Saturn, and other gas giants.

  16. Neutron radiographic viewing system

    NASA Technical Reports Server (NTRS)

    Leysath, W.; Brown, R. L.

    1972-01-01

    Neutron radiographic viewing system consisting of camera head and control processor is developed for use in nondestructive testing applications. Camera head consists of neutron-sensitive image intensifier system, power supply, and SEC vidicon camera head. Both systems, with their optics, are housed on test mount.

  17. Neutron capture therapies

    SciTech Connect

    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.

  18. 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.

  19. 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.

  20. Hyperons in neutron stars

    SciTech Connect

    Glendenning, N.K.

    1986-04-01

    Generalized beta equilibrium involving nucleons, hyperons, and isobars is examined for neutron star matter. The hyperons produce a considerable softening of the equation of state. It is shown that the observed masses of neutron stars can be used to settle a recent controversy concerning the nuclear compressibility. Compressibilities less than 200 MeV are incompatible with observed masses. 7 refs., 9 figs.

  1. Shielding for thermal neutrons.

    PubMed

    McCall, R C

    1997-01-01

    The problem of calculating the neutron capture gamma-ray dose rate due to thermal neutron capture in a boron or cadmium rectangular shield is considered. An example is given for shielding for a door at the exit of medical accelerator room maze in order to determine the optimum location of lead relative to the borated polyethylene.

  2. 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.

  3. Hypernuclei and massive neutron stars

    NASA Astrophysics Data System (ADS)

    Fortin, M.; Avancini, S. S.; Providência, C.; Vidaña, I.

    2017-06-01

    Background: The recent accurate measurement of the mass of two pulsars close to or above 2 M⊙ has raised the question of whether such large pulsar masses allow for the existence of exotic degrees of freedom, such as hyperons, inside neutron stars. Purpose: In the present work, we will investigate, within a phenomenological relativistic mean field approach, how the existing hypernuclei properties may constrain the neutron star equation of state and confront the neutron star maximum masses obtained with equations of state calibrated to hypernuclei properties with the astrophysical 2 M⊙ constraint. Method: The study is performed using a relativistic mean field approach to describe both the hypernuclei and the neutron star equations of state. Unified equations of state are obtained. A set of five models that describe 2 M⊙ when only nucleonic degrees of freedom are employed. Some of these models also satisfy other well-established laboratory or theoretical constraints. Results: The Λ -meson couplings are determined for all the models considered, and the Λ potential in symmetric nuclear matter and Λ matter at saturation are calculated. Maximum neutron star masses are determined for two values of the Λ -ω meson coupling, gω Λ=2 gω N/3 and gω Λ=gω N , and a wide range of values for gϕ Λ. Hyperonic stars with the complete baryonic octet are studied, restricting the coupling of the Σ and Ξ hyperons to the ω ,ρ , and σ mesons due to the lack of experimental data, and maximum star masses calculated. Conclusions: We conclude that, within a phenomenological relativistic mean field approach, the currently available hypernuclei experimental data and the lack of constraints on the asymmetric equation of state of nuclear matter at high densities set only a limited number of constraints on the neutron star matter equation of state using the recent 2 M⊙ observations. It is shown that the Λ potential in symmetric nuclear matter takes a value of ˜30 -32 Me

  4. Formulating hospital strategy: moving beyond a market mentality.

    PubMed

    Liedtka, J M

    1992-01-01

    Hospitals face a set of issues critical to strategy formulation that are markedly different than those faced by traditional corporations. Given this, the relevance of current business approaches to strategy formulation that focus exclusively on a narrow set of market-driven factors is questionable. Hospitals, it is argued, must take a more comprehensive view of strategy formulation that goes beyond issues of internal competency and environmental opportunities to incorporate the values of caregivers and the societal responsibilities of the institution as well.

  5. Neutron filters for producing monoenergetic neutron beams

    SciTech Connect

    Harvey, J.A.; Hill, N.W.; Harvey, J.R.

    1982-01-01

    Neutron transmission measurements have been made on high-purity, highly-enriched samples of /sup 58/Ni (99.9%), /sup 60/Ni (99.7%), /sup 64/Zn (97.9%) and /sup 184/W (94.5%) to measure their neutron windows and to assess their potential usefulness for producing monoenergetic beams of intermediate energies from a reactor. Transmission measurements on the Los Alamos Sc filter (44.26 cm Sc and 1.0 cm Ti) have been made to determine the characteristics of the transmitted neutron beam and to measure the total cross section of Sc at the 2.0 keV minimum. When corrected for the Ti and impurities, a value of 0.35 +- 0.03 b was obtained for this minimum.

  6. Formulations of entomopathogens as bioinsecticides

    USDA-ARS?s Scientific Manuscript database

    Developing a proper formulation is a necessary component for commercialization of entomopathogenic microbes as biological insecticides. The objective of this chapter is to present broad-ranging information about formulations to foster research toward developing commercial microbial-based insecticide...

  7. Advances in Neutron Spectroscopy with Deuterated Organic Scintillators

    NASA Astrophysics Data System (ADS)

    Febbraro, Michael; Pain, Steve; Becchetti, Frederick

    2015-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Nnamani, Nnaemeka; HFNG Collaboration

    2015-04-01

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

  9. Oxybutynin: an overview of the available formulations

    PubMed Central

    McCrery, Rebecca J; Appell, Rodney A

    2006-01-01

    Overactive bladder (OAB) is a common problem presented to by physicians. Standard treatment with antimuscarinic medication is directed at suppressing involuntary detrusor contractions by blocking the binding of acetylcholine to muscarinic receptors in the bladder. Oxybutynin chloride is the first of several antimuscarinic medications to be marketed for OAB. Although efficacious for treating OAB symptoms, the side effects and suboptimal dosing regimen decrease its utility. To improve patient compliance and tolerability, alternative delivery systems for oxybutynin have subsequently been developed and include a once-daily formulation and a transdermal system. The currently available formulations of oxybutynin are the subject of this review. PMID:18360578

  10. 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)

  11. 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.

  12. 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.

  13. 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.

  14. The Neutron Structure Function

    NASA Astrophysics Data System (ADS)

    Holt, Roy

    2013-10-01

    Knowledge of the neutron structure function is important for testing models of the nucleon, for a complete understanding of deep inelastic scattering (DIS) from nuclei, and for high energy experiments. As there exist no free neutron targets, neutron structure functions have been determined from deep inelastic scattering from the deuteron. Unfortunately, the short-range part of the deuteron wave function becomes important in extracting the neutron structure function at very high Bjorken x. New methods have been devised for Jefferson Lab experiments to mitigate this problem. The BONUS experiment involves tagging spectator neutrons in the deuteron, while the MARATHON experiment minimizes nuclear structure effects by a comparison of DIS from 3H and 3He. A summary of the status and future plans will be presented. This work supported by the U. S. Department of Energy, Office of Nuclear Physics, under contract DE-AC02-06CH11357.

  15. New class of neutron detectors

    SciTech Connect

    Czirr, J.B.

    1997-09-01

    An optimized neutron scattering instrument design must include all significant components, including the detector. For example, useful beam intensity is limited by detector dead time; detector pixel size determines the optimum beam diameter, sample size, and sample to detector distance; and detector efficiency vs. wavelength determines the available energy range. As an example of the next generation of detectors that could affect overall instrumentation design, we will describe a new scintillator material that is potentially superior to currently available scintillators. We have grown and tested several small, single crystal scintillators based upon the general class of cerium-activated lithium lanthanide borates. The outstanding characteristic of these materials is the high scintillation efficiency-as much as five times that of Li-glass scintillators. This increase in light output permits the practical use of the exothermic B (n, alpha) reaction for low energy neutron detection. This reaction provides a four-fold increase in capture cross section relative to the Li (n, alpha) reaction, and the intriguing possibility of demanding a charged-particle/gamma ray coincidence to reduce background detection rates. These new materials will be useful in the thermal and epithermal energy ran at reactors and pulsed neutron sources.

  16. Performance study of polycrystalline CVD diamond detectors for fast neutron monitoring

    SciTech Connect

    Singh, Arvind Kumar, Amit Topkar, Anita

    2014-04-24

    Diamond detectors using polycrystalline CVD diamond substrates of thickness 300μm and 100μm were fabricated for fast neutron monitoring application.. The characterization of detectors was carried out using various tests such as leakage current, capacitance and alpha particle response. The performance of detectors was evaluated for fast neutrons at different neutron yields. The results presented in this work demonstrate that the diamond detectors will be suitable for monitoring fast neutrons.

  17. Plutonium Measurements with a Fast-Neutron Multiplicity Counter for Nuclear Safeguards Applications

    SciTech Connect

    Jennifer L. Dolan; Marek Flaska; Alexis Poitrasson-Riviere; Andreas Enqvist; Paolo Peerani; David L. Chichester; Sara A. Pozzi

    2014-11-01

    Measurements were performed at the Joint Research Centre in Ispra, Italy to field test a fast-neutron multiplicity counter developed at the University of Michigan. The measurements allowed the illustration of the system’s photon discrimination abilities, efficiency when measuring neutron multiplicity, ability to characterize 240Pueff mass, and performance relative to a currently deployed neutron coincidence counter. This work is motivated by the need to replace and improve upon 3He neutron detection systems for nuclear safeguards applications.

  18. Single crystal neutron diffraction for the inorganic chemist - a practical guide.

    SciTech Connect

    Piccoli, P.; Koetzle, T. F.; Schultz, A. J.; Intense Pulsed Neutron Source

    2007-01-01

    Advances and upgrades in neutron sources and instrumentation are poised to make neutron diffraction more accessible to inorganic chemists than ever before. These improvements will pave the way for single crystal investigations that currently may be difficult, for example due to small crystal size or large unit cell volume. This article aims to highlight what can presently be achieved in neutron diffraction and looks forward toward future applications of neutron scattering in inorganic chemistry.

  19. Low dose neutron late effects: Cataractogenesis. Progress report, April 1, 1991--December 15, 1991

    SciTech Connect

    Worgul, B.V.

    1991-12-01

    The work is formulated to resolve the uncertainty regarding the relative biological effectiveness (RBE) of low dose neutron radiation. The study exploits the fact that cataractogenesis is sensitive to the inverse dose-rate effect as has been observed with heavy ions and was an endpoint considered in the follow-up of the A-bomb survivors. The neutron radiations were initiated at the Radiological Research Accelerator facility (RARAF) of the Nevis Laboratory of Columbia University. Four week old ({plus_minus} 1 day) rats were divided into eight dose groups each receiving single or fractionated total doses of 0.2, 1.0, 5.0 and 25.0 cGy of monoenergetic 435 KeV neutrons. Special restraining jigs insured that the eye, at the midpoint of the lens, received the appropriate energy and dose with a relative error of {plus_minus}5%. The fractionation regimen consisted of four exposures, each administered at three hour ({plus_minus}) intervals. The neutron irradiated groups are being compared to rats irradiated with 250kVp X-rays in doses ranging from 0.5 to 7 Gy. The animals are being examined on a biweekly basis utilizing conventional slit-lamp biomicroscopy and the Scheimpflug Slit Lamp Imaging System (Zeiss). The follows-ups, entering their second year, will continue throughout the life-span of the animals. This is essential inasmuch as given the extremely low doses which are being utilized clinically detectable opacities were not anticipated until a significant fraction of the life span has lapsed. Current data support this contention. At this juncture cataracts in the irradiated groups are beginning to exceed control levels.

  20. LANSCE beam current limiter

    NASA Astrophysics Data System (ADS)

    Gallegos, Floyd R.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the beam current limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beamline below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described.

  1. LANSCE beam current limiter

    SciTech Connect

    Gallegos, F.R.

    1996-06-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the Beam Current Limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beam line below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described.

  2. LANSCE beam current limiter

    SciTech Connect

    Gallegos, F.R.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. Active instrumentation, such as the beam current limiter, is a component of the RSS. The current limiter is designed to limit the average current in a beamline below a specific level, thus minimizing the maximum current available for a beam spill accident. The beam current limiter is a self-contained, electrically isolated toroidal beam transformer which continuously monitors beam current. It is designed as fail-safe instrumentation. The design philosophy, hardware design, operation, and limitations of the device are described. {copyright} {ital 1997 American Institute of Physics.}

  3. 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.

  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. Boron-Lined Straw-Tube Neutron Detector Test

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Stromswold, David C.

    2010-08-07

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. Reported here are the results of tests of a boron-lined proportional counter design variation. In the testing described here, the neutron detection efficiency and gamma ray rejection capabilities of a system manufactured by Proportional Technologies, Inc, was tested.

  6. Boron-Lined Multichamber and Conventional Neutron Proportional Counter Tests

    SciTech Connect

    Woodring, Mitchell L.; Ely, James H.; Kouzes, Richard T.; Stromswold, David C.

    2010-09-07

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride (BF3)-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated non-scintillating plastic fibers. In addition, a few other companies have detector technologies that might be competitive in the near term as an alternative technology. Reported here are the results of tests of a boron-lined, multichamber proportional counter manufactured by LND, Inc. Also reported are results obtained with an earlier design of conventional, boron-lined, proportional counters from LND. This testing measured the required performance for neutron detection efficiency and gamma-ray rejection capabilities of the detectors.

  7. Boron-Lined Multitube Neutron Proportional Counter Test

    SciTech Connect

    Woodring, Mitchell L.; Ely, James H.; Kouzes, Richard T.; Stromswold, David C.

    2010-09-07

    Radiation portal monitors used for interdiction of illicit materials at borders include highly sensitive neutron detection systems. The main reason for having neutron detection capability is to detect fission neutrons from plutonium. The currently deployed radiation portal monitors (RPMs) from Ludlum and Science Applications International Corporation (SAIC) use neutron detectors based upon 3He-filled gas proportional counters, which are the most common large neutron detector. There is a declining supply of 3He in the world, and thus, methods to reduce the use of this gas in RPMs with minimal changes to the current system designs and sensitivity to cargo-borne neutrons are being investigated. Four technologies have been identified as being currently commercially available, potential alternative neutron detectors to replace the use of 3He in RPMs. These technologies are: 1) Boron trifluoride (BF3)-filled proportional counters, 2) Boron-lined proportional counters, 3) Lithium-loaded glass fibers, and 4) Coated non-scintillating plastic fibers. In addition, a few other companies have detector technologies that might be competitive in the near term as an alternative technology. Reported here are the results of tests of a boron-lined, “multitube” proportional counter manufactured by Centronic Ltd. (Surry, U.K. and Houston, TX). This testing measured the required performance for neutron detection efficiency and gamma-ray rejection capabilities of the detector.

  8. Neutron dosimetry, moderated energy spectrum, and neutron capture therapy for californium-252 medical sources

    NASA Astrophysics Data System (ADS)

    Rivard, Mark Joseph

    Examination of neutron dosimetry for 252Cf has been conducted using calculative and experimental means. Monte Carlo N-Particle (MCNP) transport code was used in a distributed computing environment as a parallel virtual machine (PVM) to determine the absorbed neutron dose and neutron energy spectrum from 252Cf in a variety of clinically relevant materials. Herein, a Maxwellian spectrum was used to model the 252Cf neutron emissions within these materials. 252Cf mixed-field dosimetry of Applicator Tube (AT) type sources was measured using 1.0 and 0.05 cm3 tissue-equivalent ion chambers and a miniature GM counter. A dosimetry protocol was formulated similar that of ICRU 45. The 252Cf AT neutron dosimetry was determined in the cylindrical coordinate system formalism recommended by the AAPM Task Group 43. These results demonstrated the overwhelming dependence of dosimetry on the source geometry factor as there was no significant neutron attenuation within the source or encapsulation. Gold foils and TLDs were used to measure the thermal flux in the vicinity of 252Cf AT sources to compare with the results calculated using MCNP. As the fast neutron energy spectrum did not markedly changed at increasing distances from the AT source, neutron dosimetry results obtained with paired ion chambers using fixed sensitivity factors agreed well with MCNP results and those in the literature. Calculations of moderated 252Cf neutron energy spectrum with various loadings of 10B and 157Gd were performed, in addition to analysis of neutron capture therapy dosimetry with these isotopes. Radiological concerns such as personnel exposure and shielding of 252Cf emissions were examined. Feasibility of a high specific-activity 252Cf HDR source was investigated through radiochemical and metallurgical studies using stand-ins such as Tb, Gd and 249Cf. Issues such as capsule burst strength due to helium production for a variety of proposed HDR sources were addressed. A recommended 252Cf source

  9. 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.

  10. PREFACE: Fundamental Neutron Physics: Introduction and Overview Fundamental Neutron Physics: Introduction and Overview

    NASA Astrophysics Data System (ADS)

    Holstein, Barry R.

    2009-10-01

    In the 77 years since its discovery by Chadwick in 1932, the neutron has come to play an increasingly important role in contemporary physics. As the next to lightest baryon, it is, of course, one of the two primary components of the atomic nucleus and studies of isotopes (nuclei with varying numbers of neutrons but the same proton number) and of the neutron drip line are one of the important focuses of the recently approved radioactive beam machine to be built at Michigan State University. Precise knowledge of its ~900 second lifetime is crucial to determination of the time at which nucleosynthesis occurs in the early universe. Because it is electrically neutral, the neutron can penetrate the atomic cloud and neutron scattering has become a powerful tool in the study of the structure of materials in condensed matter and biophysics. These are all important issues, but will not be addressed in the articles presented below. Rather, in the set of manuscripts published herein, we show various ways in which the neutron has come to probe fundamental questions in physics. We present six such articles: Because of its simple structure, neutron beta decay has served as a laboratory for the study of possible symmetry violations, including search for possible Script T-violation via measurement of the D coefficient, search for second class currents and/or possible CVC violation via examination of recoil terms, search for right-handed currents via examination of correlations, search for S, T couplings via measurement of the b parameter, etc. The study of neutron decay is reviewed in the article by Jeff Nico. The use of the neutron as a probe of possible Script T-violation via the existence of a non-zero electric dipole moment is discussed in the article by Steve Lamoreaux. The neutron is a prime player in the experimental study of hadronic parity violation, via experiments involving radiative capture and spin rotation, as examined in the article by Barry Holstein. Because of its

  11. The Frankfurt neutron source FRANZ

    NASA Astrophysics Data System (ADS)

    Alzubaidi, Suha; Bartz, Ulrich; Basten, Markus; Bechtold, Alexander; Chau, Long Phi; Claessens, Christine; Dinter, Hannes; Droba, Martin; Fix, Christopher; Hähnel, Hendrik; Heilmann, Manuel; Hinrichs, Ole; Huneck, Simon; Klump, Batu; Lotz, Marcel; Mäder, Dominik; Meusel, Oliver; Noll, Daniel; Nowottnick, Tobias; Obermayer, Marcus; Payir, Onur; Petry, Nils; Podlech, Holger; Ratzinger, Ulrich; Schempp, Alwin; Schmidt, Stefan; Schneider, Philipp; Seibel, Anja; Schwarz, Malte; Schweizer, Waldemar; Volk, Klaus; Wagner, Christopher; Wiesner, Christoph

    2016-05-01

    A 2MeV proton beam will produce a quasi-Maxwellian neutron spectrum of around 30 keV by the 7Li(p, n)7Be reaction. The experiments are mainly focused on the measurement of differential neutron capture cross sections relevant for the astrophysical s-process in nuclear synthesis. Moreover, proton capture cross sections for the astrophysical p-process can be measured directly with the proton beam. For an efficient time of flight measurement of the neutron energies along the 0.7 m long drift from the Li-target to the sample, 1ns short, intense proton pulses are needed at the target. Additionally, to reach 107 n/cm2/s at the sample, a pulse repetition rate of 250 kHz is intended. After completion and successful running in, FRANZ will become a user facility with internal and external users. The 120 kV injector terminal and the 200mA proton source as well as the low-energy beam transport section and the FRANZ cave have been realized successfully. The 1.9 MV RF accelerator consists of a combined 4-Rod-RFQ/IH-DTL-resonator and is in the RF tuning and power testing phase. The 2 MeV transport and rebuncher section is ready for installation. In a first step FRANZ will offer experimental areas for neutron activation experiments and for proton beam experiments, as mentioned above. From the accelerator physics point of view, FRANZ will be an excellent facility for high current beam investigations and for beam wall interaction studies.

  12. Eleventh DOE workshop on personnel neutron dosimetry

    SciTech Connect

    Not Available

    1991-12-31

    Since its formation, the Office of Health (EH-40) has stressed the importance of the exchange of information related to and improvements in neutron dosimetry. This Workshop was the eleventh in the series sponsored by the Department of Energy (DOE). It provided a forum for operational personnel at DOE facilities to discuss current issues related to neutron dosimetry and for leading investigators in the field to discuss promising approaches for future research. A total of 26 papers were presented including the keynote address by Dr. Warren K. Sinclair, who spoke on, ``The 1990 Recommendations of the ICRP and their Biological Background.`` The first several papers discussed difficulties in measuring neutrons of different energies and ways of compensating or deriving correction factors at individual facilities. Presentations were also given by the US Navy and Air Force. Current research in neutron dosimeter development was the subject of the largest number of papers. These included a number on the development of neutron spectrometers. Selected papers were processed separately for inclusion in the Energy Science and Technology Database.

  13. Toxicity of agrochemical formulations.

    PubMed

    Carmichael, Neil G

    2005-01-01

    Most agrochemicals have physicochemical properties that make it impractical to apply them directly to crops and other targets. It is necessary to provide a concentrate of the active ingredient, to which formulation agents have been added to allow dilution with water for spraying. These ingredients perform several functions, including emulsifying, solubilizing, antifoaming, and the like. The properties of these materials are not intended to include pesticidal activity. However, some of these materials may have intrinsic toxicologic properties that should be taken into account in an overall evaluation of the safety of the product. In agriculture, exposure to these materials is sporadic and seasonal. The testing of the complete formulation is based on the evaluation of this risk, and it is concentrated on the evaluation of the short-term exposure to the concentrated product. Many of these substances are rather banal and are generally regarded as safe. Exceptions to this rule do exist, particularly concerning solvents; in such cases a fuller data package is necessary to perform risk assessment.

  14. Patented herbal formulations and their therapeutic applications.

    PubMed

    Musthaba, Mohamed; Baboota, Sanjula; Athar, Tanwir M D; Thajudeen, Kamal Y; Ahmed, Sayeed; Ali, Javed

    2010-11-01

    Recently, there is a greater global interest in non synthetic, natural medicines derived from plant sources due to better tolerance and minimum adverse drug reactions as compared to synthetic medicines. Herbal products are also commonly used by the patients with certain chronic medical conditions, including breast cancer, liver disease, human immunodeficiency, asthma and rheumatological disorders. WHO estimates that about three-quarters of the world's population currently uses herbs and other forms of traditional medicines for the treatment of various diseases. The herbs are formulated in different modern dosage forms, such as Tablets, Capsules, Topical cream, Gel, Ointment and even some novel drug delivery forms, like extended release, sustained release, and microencapsules dosage forms. Patenting of herbal formulations has increased over the past few years and scientific evidence of therapeutic activity has been reported by performing various in vitro and in vivo experiments. This manuscript deals with various patented herbal formulations with their therapeutic application against various diseases.

  15. Experience with position-sensitive neutron detectors at the Intense Pulsed Neutron Source

    NASA Astrophysics Data System (ADS)

    Crawford, R. K.; Haumann, J. R.; Epperson, J. E.; Thiyagarajan, P.; Schultz, A. J.; Felcher, G. P.; Montague, D. G.; Dejus, R. J.

    1990-12-01

    At the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory, pulses of protons accelerated in a synchrotron produce pulses of fast neutrons via the spallation process in an enriched uranium target. After moderation, the resulting pulses of slow neutrons are directed into beams which serve a variety of neutron-scattering instruments. Currently there are thirteen neutron-scattering instruments in operation or under development at IPNS, and six of these use position-sensitive neutron detectors (PSDs). These PSDs are: a 30 cm × 30 cm, ˜3 mm resolution, neutron Anger camera area PSD with 6Li-glass scintillator; a 2.5 cm diameter, ˜0.7 mm resolution, microchannel-plate area PSD with 6Li-glass scintillator; a 20 cm × 20 cm, ˜5 mm resolution, 3He proportional-counter area PSD; a 40 cm × 40 cm, ˜4 mm resolution, 3He proportional-counter area PSD; a flat 20 cm long, ˜1.6 mm resolution, 3He proportional-counter linear PSD; and 160 cylindrical 3He proportional-counter linear PSDs, each of which is 1.27 cm in diameter and 60 cm long and has ˜14 mm resolution. These detectors, in addition to being position-sensitive, resolve the time of the neutron capture with ˜1 μs precision for neutron time-of-flight measurements. This paper will discuss these various PSDs with emphasis on the instrumental specifications and the reasons for the selection of the different types of PSDs, and will also discuss the observed performances of these PSDs.

  16. Experience with position sensitive neutron detectors at the Intense Pulsed Neutron Source

    SciTech Connect

    Crawford, R.K.; Haumann, J.R.; Schultz, A.J.; Felcher, G.P.; Epperson, J.E.; Thiyagarajan, P.; Montague, D.G.; Dejus, R.J.

    1990-05-07

    At the Intense Pulsed Neutron Source (IPNS) pulses of protons accelerated in a synchrotron produce pulses of fast neutrons via the spallation process in an enriched uranium target. After moderation, the resulting pulses of slow neutrons are directed into beams which serve a variety of neutron scattering instruments. Currently there are thirteen neutron scattering instruments in operation or under development at IPNS, and six of these use position-sensitive neutron detectors (PSDs). These PSDs are: a 30 cm {times} 30 cm, {approximately}3 mm resolution, neutron Anger camera area PSD with {sup 6}Li-glass scintillator; a 2.5 cm dia, {approximately}0.7 mm resolution, microchannel-plate area PSD with {sup 6}Li-glass scintillator; a 20 cm {times} 20 cm, {approximately}5 mm resolution, {sup 3}He proportional counter area PSD; a 40 cm {times} 40 cm, {approximately}4 mm resolution, {sup 3}He proportional counter area PSD; a flat 20 cm long, {approximately}1.6 mm resolution, {sup 3}He proportional counter linear PSD; and 160 cylindrical {sup 3}He proportional counter linear PSDs, each of which is 1.27 cm in dia 60 cm long and has {approximately}14 mm resolution. These detectors, in addition to being position-sensitive, resolve the time of the neutron capture with {approximately}1 {mu}s precision for neutron time-of-flight measurements. This paper will discuss these various PSDs with emphasis on the instrumental specifications and the reasons for the selection of the different types of PSDs, and will also discuss the observed performances of these PSDs. 14 refs., 6 figs., 1 tab.

  17. Systematic neutron guide misalignment for an accelerator-driven spallation neutron source

    NASA Astrophysics Data System (ADS)

    Zendler, C.; Bentley, P. M.

    2016-08-01

    The European Spallation Source (ESS) is a long pulse spallation neutron source that is currently under construction in Lund, Sweden. A considerable fraction of the 22 planned instruments extend as far as 75-150 m from the source. In such long beam lines, misalignment between neutron guide segments can decrease the neutron transmission significantly. In addition to a random misalignment from installation tolerances, the ground on which ESS is built can be expected to sink with time, and thus shift the neutron guide segments further away from the ideal alignment axis in a systematic way. These systematic errors are correlated to the ground structure, position of buildings and shielding installation. Since the largest deformation is expected close to the target, even short instruments might be noticeably affected. In this study, the effect of this systematic misalignment on short and long ESS beam lines is analyzed, and a possible mitigation by overillumination of subsequent guide sections investigated.

  18. A Sealed-Accelerator-Tube Neutron Generator for Boron Neutron Capture Therapy Application

    SciTech Connect

    Leung, K.-N.; Leung, K.N.; Lee, Y.; Verbeke, J.M.; Vurjic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1998-06-01

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator applications. By using a 2.5-cm-diameter RF-driven multicusp source and a computer designed 100 keV accelerator column, peak extractable hydrogen current exceeding 1 A from a 3-mm-diameter aperture, together with H{sup +} yields over 94% have been achieved. These experimental findings together with recent moderator design will enable one to develop compact 14 MeV neutron generators based on the D-T fusion reaction. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without pumping. With a 120 keV and 1 A deuteron beam, it is estimated that a treatment time of {approx} 45 minutes is needed for boron neutron capture therapy.

  19. The National Ignition Facility neutron imaging system.

    PubMed

    Wilke, Mark D; Batha, Steven H; Bradley, Paul A; Day, Robert D; Clark, David D; Fatherley, Valerie E; Finch, Joshua P; Gallegos, Robert A; Garcia, Felix P; Grim, Gary P; Jaramillo, Steven A; Montoya, Andrew J; Moran, Michael J; Morgan, George L; Oertel, John A; Ortiz, Thomas A; Payton, Jeremy R; Pazuchanics, Peter; Schmidt, Derek W; Valdez, Adelaida C; Wilde, Carl H; Wilson, Doug C

    2008-10-01

    The National Ignition Facility (NIF) is scheduled to begin deuterium-tritium (DT) shots possibly in the next several years. One of the important diagnostics in understanding capsule behavior and to guide changes in Hohlraum illumination, capsule design, and geometry will be neutron imaging of both the primary 14 MeV neutrons and the lower-energy downscattered neutrons in the 6-13 MeV range. The neutron imaging system (NIS) described here, which we are currently building for use on NIF, uses a precisely aligned set of apertures near the target to form the neutron images on a segmented scintillator. The images are recorded on a gated, intensified charge coupled device. Although the aperture set may be as close as 20 cm to the target, the imaging camera system will be located at a distance of 28 m from the target. At 28 m the camera system is outside the NIF building. Because of the distance and shielding, the imager will be able to obtain images with little background noise. The imager will be capable of imaging downscattered neutrons from failed capsules with yields Y(n)>10(14) neutrons. The shielding will also permit the NIS to function at neutron yields >10(18), which is in contrast to most other diagnostics that may not work at high neutron yields. The following describes the current NIF NIS design and compares the predicted performance with the NIF specifications that must be satisfied to generate images that can be interpreted to understand results of a particular shot. The current design, including the aperture, scintillator, camera system, and reconstruction methods, is briefly described. System modeling of the existing Omega NIS and comparison with the Omega data that guided the NIF design based on our Omega results is described. We will show NIS model calculations of the expected NIF images based on component evaluations at Omega. We will also compare the calculated NIF input images with those unfolded from the NIS images generated from our NIS numerical

  20. Neutrons and Fundamental Symmetries

    SciTech Connect

    Plaster, Bradley

    2016-01-11

    The research supported by this project addressed fundamental open physics questions via experiments with subatomic particles. In particular, neutrons constitute an especially ideal “laboratory” for fundamental physics tests, as their sensitivities to the four known forces of nature permit a broad range of tests of the so-called “Standard Model”, our current best physics model for the interactions of subatomic particles. Although the Standard Model has been a triumphant success for physics, it does not provide satisfactory answers to some of the most fundamental open questions in physics, such as: are there additional forces of nature beyond the gravitational, electromagnetic, weak nuclear, and strong nuclear forces?, or why does our universe consist of more matter than anti-matter? This project also contributed significantly to the training of the next generation of scientists, of considerable value to the public. Young scientists, ranging from undergraduate students to graduate students to post-doctoral researchers, made significant contributions to the work carried out under this project.

  1. Neutron-neutron correlations in ^6He

    NASA Astrophysics Data System (ADS)

    Atramentov, Oleksiy; Vary, James; Navrátil, Petr

    2004-05-01

    We evaluate 2-neutron correlations in ^6He within the ab initio no-core nuclear shell model using a realistic effective 2-body Hamiltonian. The distribution of relative separation between neutrons, including spin dependence, is obtained for the ground, and lowest 2^+ and 1^- states. We compare angular distributions and relative kinetic energy distributions of neutron-pairs in these ^6He states directly with 2-neutron correlation measurements from dissociation experiments (Aumann, Phys. Rev. C 59, 1252 (1999); Wang, Phys. Rev. C 65,034306 (2002)). The reasonable agreement between these theoretical 1^- and experimental distributions supports an interpretation of the experiment as a simple process: Coulomb excitation of the 1^- followed by dissociation without significant final state interactions. We argue that such a simple picture may be reasonable for the breakup of this halo nucleus. We present predictions for additional spin-dependent correlation experiments that will sensitively test this simple picture. Work supported in part by USDOE grant DE-FG02-87ER40371 and was performed, in part, under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  2. An Exploration of Neutron Detection in Semiconducting Boron Carbide

    NASA Astrophysics Data System (ADS)

    Hong, Nina

    The 3He supply problem in the U.S. has necessitated the search for alternatives for neutron detection. The neutron detection efficiency is a function of density, atomic composition, neutron absorption cross section, and thickness of the neutron capture material. The isotope 10B is one of only a handful of isotopes with a high neutron absorption cross section---3840 barns for thermal neutrons. So a boron carbide semiconductor represents a viable alternative to 3He. This dissertation provides an evaluation of the performance of semiconducting boron carbide neutron detectors grown by plasma enhance chemical vapor deposition (PECVD) in order to determine the advantages and drawbacks of these devices for neutron detection. Improved handling of the PECVD system has resulted in an extremely stable plasma, enabling deposition of thick films of semiconducting boron carbide. A variety of material and semiconducting characterization tools have been used to investigate the structure and electronic properties of boron carbide thin films, including X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, infrared/Raman spectroscopy, current-voltage measurements and capacitance-voltage measurements. Elemental concentrations in the boron carbide films have been obtained from Rutherford backscattering and elastic recoil detection analysis. Solid state neutron detection devices have been fabricated in the form of heterostructured p-n diodes, p-type boron carbide/n-type Si. Operating conditions, including applied bias voltage, and time constants, have been optimized for maximum detection efficiency and correlated to the semiconducting properties investigated in separate electronic measurements. Accurate measurements of the neutron detection efficiency and the response of the detector to a wide range of neutron wavelengths have been performed at a well calibrated, tightly collimated, "white" cold neutron beam source using time-of-flight neutron detection technique

  3. Colloquium: The neutron lifetime

    SciTech Connect

    Wietfeldt, Fred E.; Greene, Geoffrey L.

    2011-10-01

    The decay of the free neutron into a proton, electron, and antineutrino is the prototype semileptonic weak decay and is the simplest example of nuclear beta decay. It played a key role in the early Universe as it determined the ratio of neutrons to protons during the era of primordial light element nucleosynthesis. Neutron decay is physically related to important processes in solar physics and neutrino detection. The mean neutron lifetime has been the subject of more than 20 major experiments done, using a variety of methods, between 1950 and the present. The most precise recent measurements have stated accuracies approaching 0.1%, but are not in good agreement as they differ by as much as 5{sigma} using quoted uncertainties. The history of neutron lifetime measurements is reviewed and the different methods used are described, giving important examples of each. The discrepancies and some systematic issues in the experiments that may be responsible are discussed, and it is shown by means of global averages that the neutron lifetime is likely to lie in the range of 880-884 s. Plans and prospects for future experiments are considered that will address these systematic issues and improve our knowledge of the neutron lifetime.

  4. Colloquium: The neutron lifetime

    SciTech Connect

    Greene, Geoffrey L; Wietfeldt, F

    2011-01-01

    The decay of the free neutron into a proton, electron, and antineutrino is the prototype semileptonic weak decay and is the simplest example of nuclear beta decay. It played a key role in the early Universe as it determined the ratio of neutrons to protons during the era of primordial light element nucleosynthesis. Neutron decay is physically related to important processes in solar physics and neutrino detection. The mean neutron lifetime has been the subject of more than 20 major experiments done, using a variety of methods, between 1950 and the present. The most precise recent measurements have stated accuracies approaching 0.1%, but are not in good agreement as they differ by as much as 5 sigma using quoted uncertainties. The history of neutron lifetime measurements is reviewed and the different methods used are described, giving important examples of each. The discrepancies and some systematic issues in the experiments that may be responsible are discussed, and it is shown by means of global averages that the neutron lifetime is likely to lie in the range of 880 884 s. Plans and prospects for future experiments are considered that will address these systematic issues and improve our knowledge of the neutron lifetime.

  5. Self-Setting Calcium Orthophosphate Formulations

    PubMed Central

    Dorozhkin, Sergey V.

    2013-01-01

    In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes, which set and harden forming either a non-stoichiometric calcium deficient hydroxyapatite or brushite. Since both of them are remarkably biocompartible, bioresorbable and osteoconductive, self-setting calcium orthophosphate formulations appear to be promising bioceramics for bone grafting. Furthermore, such formulations possess excellent molding capabilities, easy manipulation and nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation. In addition, reinforced formulations have been introduced, which might be described as calcium orthophosphate concretes. The discovery of self-setting properties opened up a new era in the medical application of calcium orthophosphates and many commercial trademarks have been introduced as a result. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as pourability and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules and even cells for tissue engineering purposes. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided. PMID:24956191

  6. Stabilized Glucagon Formulation for Bihormonal Pump Use

    PubMed Central

    Steiner, Solomon S; Li, Ming; Hauser, Robert; Pohl, Roderike

    2010-01-01

    Background A promising approach to treat diabetes is the development of an automated bihormonal pump administering glucagon and insulin. A physically and chemically stable glucagon formulation does not currently exist. Our goal is to develop a glucagon formulation that is stable as a clear ungelled solution, free of fibrils at a pH of 7 for at least 7 days at 37 °C. Methods Experimental glucagon formulations were studied for stability at 25 and 37 °C. Chemical degradation was quantified by reverse phase ultra-performance liquid chromatography. Physical changes were studied using light obscuration and visual observations. Results Glucagon content of Biodel glucagon and Lilly glucagon at pH 2 and pH 4, as measured by high-performance liquid chromatography at 25 °C, was 100% at 7 days compared to 87% and <7%, respectively. Light obscuration measurements indicated Lilly glucagon at pH 4 formed an opaque gel, while Biodel glucagon formulation remained a clear solution beyond 50 days at 37 °C. Visual observations confirmed these results. Conclusions Biodel glucagon is a stabilized formulation at physiological pH and remains chemically and physically stable beyond 7 days at 37 °C, suggesting its utility for use in a bihormonal pump. PMID:21129327

  7. Subscale Testing of Prompt Agent Defeat Formulations

    NASA Astrophysics Data System (ADS)

    Milby, Christopher; Stamatis, Demitrios; Daniels, Amber; Svingala, Forrest; Lightstone, Jim; Miller, Kendra; Bensman, Misty; Bohmke, Matthew

    2015-06-01

    There is a need to improve the current bioagent defeat systems with formulations that produce lower peak pressure, impulse, sustained high temperatures, and release of biocidal species for prompt defeat applications. In this work, explosive charge configurations similar to fuel-air explosives were detonated in a semi-enclosed chamber configuration. Binder type and fuel-to-oxidizer ratios were varied to observe the effects on combustion performance. Thermocouple measurements and high-speed video were used to monitor the combustion of the dispersed formulation. The down-selected formulations were then tested in a sub-scale vented agent defeat system developed to evaluate performance of formulations against aerosolized Bacillus thuringiensis (BT) spores. Diagnostics such as thermocouples, piezoelectric pressure gauges, and pyrometry were utilized to characterize the detonation event. Biological sampling with surface coupons, liquid impingement, and filters of the post detonation environment were utilized to determine spore survivability and rank the relative effectiveness of each formulation. Distribution Statement A: Approved for Public Release; Distribution is Unlimited

  8. Optics for Advanced Neutron Imaging and Scattering

    SciTech Connect

    Moncton, David E.; Khaykovich, Boris

    2016-03-30

    During the report period, we continued the work as outlined in the original proposal. We have analyzed potential optical designs of Wolter mirrors for the neutron-imaging instrument VENUS, which is under construction at SNS. In parallel, we have conducted the initial polarized imaging experiment at Helmholtz Zentrum, Berlin, one of very few of currently available polarized-imaging facilities worldwide.

  9. Radiation environment in the region of thunderstorm neutrons generation

    NASA Astrophysics Data System (ADS)

    Drozdov, A.; Grigoriev, A. V.; Malyshkin, Y.

    2011-12-01

    There exist a number of experimental data favoring the idea of the connection between thunderstorm activity and rises of neutron count rate, registered in on-ground [1,2] as well as space experiments [3]. Recent investigations in this area showed that the observation of thunderstorm neutrons onboard low-orbiting satellites is in principal possible [4]. The current view on the problem of thunderstorm neutrons origin assumes their generation in photonuclear reactions of the TGF radiation and atmosphere components [5]. Such neutron radiation has almost no effect on the dosimetric environment in low orbits due to dispersion in the atmosphere [6]. However it could be of considerable importance in the region of the neutrons generation (on altitudes of 10 - 20 km). The indicated values match altitudes of aviation flights so that, taking into account high penetration power of neutron radiation, one may expect some connected hazard. In the present study we perform a numerical simulation of the thunderstorm neutron radiation near the generation area. The modeling includes generation of the neutrons from TGF and further propagation with account of interaction with background nuclei. On the basis of modeling results we obtain estimates of the absorbed dose for various configurations and altitudes of the neutrons source.

  10. The neutron channeling phenomenon.

    PubMed

    Khanouchi, A; Sabir, A; Boulkheir, M; Ichaoui, R; Ghassoun, J; Jehouani, A

    1997-01-01

    Shields, used for protection against radiation, are often pierced with vacuum channels for passing cables and other instruments for measurements. The neutron transmission through these shields is an unavoidable phenomenon. In this work we study and discuss the effect of channels on neutron transmission through shields. We consider an infinite homogeneous slab, with a fixed thickness (20 lambda, with lambda the mean free path of the neutron in the slab), which contains a vacuum channel. This slab is irradiated with an infinite source of neutrons on the left side and on the other side (right side) many detectors with windows equal to 2 lambda are placed in order to evaluate the neutron transmission probabilities (Khanouchi, A., Aboubekr, A., Ghassoun, J. and Jehouani, A. (1994) Rencontre Nationale des Jeunes Chercheurs en Physique. Casa Blanca Maroc; Khanouchi, A., Sabir, A., Ghassoun, J. and Jehouani, A. (1995) Premier Congré International des Intéractions Rayonnements Matière. Eljadida Maroc). The neutron history within the slab is simulated by the Monte Carlo method (Booth, T. E. and Hendricks, J. S. (1994) Nuclear Technology 5) and using the exponential biasing technique in order to improve the Monte Carlo calculation (Levitt, L. B. (1968) Nuclear Science and Engineering 31, 500-504; Jehouani, A., Ghassoun, J. and Aboubker, A. (1994) In Proceedings of the 6th International Symposium on Radiation Physics, Rabat, Morocco). Then different geometries of the vacuum channel have been studied. For each geometry we have determined the detector response and calculated the neutron transmission probability for different detector positions. This neutron transmission probability presents a peak for the detectors placed in front of the vacuum channel. This study allowed us to clearly identify the neutron channeling phenomenon. One application of our study is to detect vacuum defects in materials.

  11. ATW neutronics design studies.

    SciTech Connect

    Wade, D. C.; Yang, W. S.; Khalil, H.

    2000-11-10

    The Accelerator Transmutation of Waste (ATW) concept has been proposed as a transuranics (TRU) (and long-lived fission product) incinerator for processing the 87,000 metric tonnes of Light Water Reactor used fuel which will have been generated by the time the currently deployed fleet of commercial reactors in the US reach the end of their licensed lifetime. The ATW is proposed to separate the uranium from the transuranics and fission products in the LWR used fuel, to fission the transuranics, to send the LWR and ATW generated fission products to the geologic repository and to send the uranium to either a low level waste disposal site or to save it for future use. The heat liberated in fissioning the transuranics would be converted to electricity and sold to partially offset the cost of ATW construction and operations. Options for incineration of long-lived fission products are under evaluation. A six-year science-based program of ATW trade and system studies was initiated in the US FY 2000 to achieve two main purposes: (1) ''to evaluate ATW within the framework of nonproliferation, waste management, and economic considerations,'' and (2) ''to evaluate the efficacy of the numerous technical options for ATW system configuration.'' This paper summarizes the results from neutronics and thermal/hydraulics trade studies which were completed at Argonne National Laboratory during the first year of the program. Core designs were developed for Pb-Bi cooled and Na cooled 840 MW{sub th} fast spectrum transmuter designs employing recycle. Additionally, neutronics analyses were performed at Argonne for a He cooled 600 MW{sub th} hybrid thermal and fast core design proposed by General Atomics Co. which runs critical for 3/4 and subcritical for 1/4 of its four year once-thin burn cycle. The mass flows and the ultimate loss of transuranic isotopes to the waste stream per unit of heat generated during transmutation have been calculated on a consistent basis and are compared. (Long

  12. High-Order Entropy Stable Formulations for Computational Fluid Dynamics

    NASA Technical Reports Server (NTRS)

    Carpenter, Mark H.; Fisher, Travis C.

    2013-01-01

    A systematic approach is presented for developing entropy stable (SS) formulations of any order for the Navier-Stokes equations. These SS formulations discretely conserve mass, momentum, energy and satisfy a mathematical entropy inequality. They are valid for smooth as well as discontinuous flows provided sufficient dissipation is added at shocks and discontinuities. Entropy stable formulations exist for all diagonal norm, summation-by-parts (SBP) operators, including all centered finite-difference operators, Legendre collocation finite-element operators, and certain finite-volume operators. Examples are presented using various entropy stable formulations that demonstrate the current state-of-the-art of these schemes.

  13. The psychiatric cultural formulation: translating medical anthropology into clinical practice.

    PubMed

    Aggarwal, Neil Krishan

    2012-03-01

    This article reviews proposed revisions to the DSM-IV Outline for Cultural Formulation for clinical practice. The author begins by exploring the theoretical development of and assumptions involved in the Cultural Formulation. A case presentation is then used to demonstrate shortcomings in the current implementation of the Cultural Formulation based on older definitions of culture. Finally, the author recommends practical questions based on the growing anthropological literature concerning the interpersonal elements of culture and the social course of illness. A simple clear format that clinically translates social science concepts has the potential to increase use of the Cultural Formulation by all psychiatrists, not just those specializing in cultural psychiatry.

  14. Novel Materials and Devices for Solid-State Neutron Detection

    SciTech Connect

    Manginell, Ronald P.; Pfeifer, Kent B.

    2015-11-01

    There is a need in many fields, such as nuclear medicine, non-proliferation, energy exploration, national security, homeland security, nuclear energy, etc, for miniature, thermal neutron detectors. Until recently, thermal neutron detection has required physically large devices to provide sufficient neutron interaction and transduction signal. Miniaturization would allow broader use in the fields just mentioned and open up other applications potentially. Recent research shows promise in creating smaller neutron detectors through the combination of high-neutron-cross-section converter materials and solid-state devices. Yet, till recently it is difficult to measure low neutron fluxes by solidstate means given the need for optimized converter materials (purity, chemical composition and thickness) and a lack of designs capable of efficient transduction of the neutron conversion products (x-rays, electrons, gamma rays). Gadolinium-based semiconductor heterojunctions have detected electrons produced by Gd-neutron reactions but only at high neutron fluxes. One of the main limitations to this type of approach is the use of thin converter layers and the inability to utilize all the conversion products. In this LDRD we have optimized the converter material thickness and chemical composition to improve capture of conversion electrons and have detected thermal neutrons with high fidelity at low flux. We are also examining different semiconductor materials and converter materials to attempt to capture a greater percentage of the conversion electrons, both low and higher energy varieties. We have studied detector size and bias scaling, and cross-sensitivity to xrays and shown that we can detect low fluxes of thermal neutrons in less than 30 minutes with high selectivity by our approach. We are currently studying improvements in performance with direct placement of the Gd converter on the detector. The advancement of sensitive, miniature neutron detectors will have benefits in

  15. Accelerator Based Neutron Beams for Neutron Capture Therapy

    SciTech Connect

    Yanch, Jacquelyn C.

    2003-04-11

    The DOE-funded accelerator BNCT program at the Massachusetts Institute of Technology has resulted in the only operating accelerator-based epithermal neutron beam facility capable of generating significant dose rates in the world. With five separate beamlines and two different epithermal neutron beam assemblies installed, we are currently capable of treating patients with rheumatoid arthritis in less than 15 minutes (knee joints) or 4 minutes (finger joints) or irradiating patients with shallow brain tumors to a healthy tissue dose of 12.6 Gy in 3.6 hours. The accelerator, designed by Newton scientific Incorporated, is located in dedicated laboratory space that MIT renovated specifically for this project. The Laboratory for Accelerator Beam Applications consists of an accelerator room, a control room, a shielded radiation vault, and additional laboratory space nearby. In addition to the design, construction and characterization of the tandem electrostatic accelerator, this program also resulted in other significant accomplishments. Assemblies for generating epithermal neutron beams were designed, constructed and experimentally evaluated using mixed-field dosimetry techniques. Strategies for target construction and target cooling were implemented and tested. We demonstrated that the method of submerged jet impingement using water as the coolant is capable of handling power densities of up to 6 x 10(sup 7) W/m(sup 2) with heat transfer coefficients of 10(sup 6)W/m(sup 2)-K. Experiments with the liquid metal gallium demonstrated its superiority compared with water with little effect on the neutronic properties of the epithermal beam. Monoenergetic proton beams generated using the accelerator were used to evaluate proton RBE as a function of LET and demonstrated a maximum RBE at approximately 30-40 keV/um, a finding consistent with results published by other researchers. We also developed an experimental approach to biological intercomparison of epithermal beams and

  16. Neutron Radiation Effect On 2N2222 And NTE 123 NPN Silicon Bipolar Junction Transistors

    NASA Astrophysics Data System (ADS)

    Oo, Myo Min; Rashid, N. K. A. Md; Karim, J. Abdul; Zin, M. R. Mohamed; Hasbullah, N. F.

    2013-12-01

    This paper examines neutron radiation with PTS (Pneumatic Transfer System) effect on silicon NPN bipolar junction transistors (2N2222 and NTE 123) and analysis of the transistors in terms of electrical characterization such as current gain after neutron radiation. The key parameters are measured with Keithley 4200SCS. Experiment results show that the current gain degradation of the transistors is very sensitive to neutron radiation. The neutron radiation can cause displacement damage in the bulk layer of the transistor structure. The current degradation is believed to be governed by increasing recombination current between the base and emitter depletion region.

  17. 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.

  18. 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)

  19. 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.

  20. 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.