Science.gov

Sample records for cold neutron moderator

  1. Cold moderators for pulsed neutron sources

    SciTech Connect

    Carpenter, J.M.

    1990-01-01

    This paper reviews cold moderators in pulsed neutron sources and provides details of the performance of different cold moderator materials and configurations. Analytical forms are presented which describe wavelength spectra and emission time distributions. Several types of cooling arrangements used in pulsed source moderators are described. Choices of materials are surveyed. The author examines some of the radiation damage effects in cold moderators, including the phenomenon of burping'' in irradiated cold solid methane. 9 refs., 15 figs., 4 tabs.

  2. The Isis cold moderators

    SciTech Connect

    Allen, G. M.; Broome, T. A.; Burridge, R. A.; Cragg, D.; Hall, R.; Haynes, D.; Hirst, J.; Hogston, J. R.; Jones, H. H.; Sexton, J.; Wright, P.

    1997-09-01

    ISIS is a pulsed spallation neutron source where neutrons are produced by the interaction of a 160 kW proton beam of energy 800 MeV in a water-cooled Tantalum Target. The fast neutrons produced are thermalized in four moderators: two ambient water, one liquid methane operating at 100K and a liquid hydrogen moderator at 20 K. This paper gives a description of the construction of both cold moderator systems, details of the operating experience and a description of the current development program.

  3. Study on void fraction distribution in the moderator cell of Cold Neutron Source systems in China Advanced Research Reactor

    NASA Astrophysics Data System (ADS)

    Li, Liangxing; Li, Huixiong; Hu, Jinfeng; Bi, Qincheng; Chen, Tingkuan

    2007-04-01

    A physical model is developed for analyzing and evaluating the void fraction profiles in the moderator cell of the Cold Neutron Source (CNS) of the China Advanced Research Reactor (CARR), which is now constructing in the China Institute of Atomic Energy (CIAE). The results derived from the model are compared with the related experimental data and its propriety is verified. The model is then used to explore the influence of various factors, including the diameter of boiling vapor bubbles, liquid density, liquid viscosity and the total heating power acted on the moderator cell, on the void fraction profiles in the cell. The results calculated with the present model indicate that the void fraction in the moderator cell increases linearly with heating power, and increases with the liquid viscosity, but decreases as the size of bubbles increases, and increases linearly with heating power. For the case where hydrogen is being used as a moderator, calculation results show that the void fraction in the moderator cell may be less than 30%, which is the maximum void fraction permitted from the nuclear physics point of view. The model and the calculation results will help to obtain insight of the mechanism that controls the void fraction distribution in the moderator cell, and provide theoretical supports for the moderator cell design.

  4. Coupled moderator neutronics

    SciTech Connect

    Russell, G.J.; Pitcher, E.J.; Ferguson, P.D.

    1995-12-01

    Optimizing the neutronic performance of a coupled-moderator system for a Long-Pulse Spallation Source is a new and challenging area for the spallation target-system designer. For optimal performance of a neutron source, it is essential to have good communication with instrument scientists to obtain proper design criteria and continued interaction with mechanical, thermal-hydraulic, and materials engineers to attain a practical design. A good comprehension of the basics of coupled-moderator neutronics will aid in the proper design of a target system for a Long-Pulse Spallation Source.

  5. Fracture probability and leak before break analysis for the cold neutron source moderator vessel

    SciTech Connect

    Chang, S.J.

    1998-04-01

    Fracture mechanics calculations are made to ensure the safety of the moderator vessel against failure by fracture. The 6061-T6 aluminum alloy is used for the moderator vessel structure. The fracture analysis of the moderator vessel consists of: (1) the probability of fracture calculations at the locations of the moderator where either the primary stress or the secondary stress assumes the highest value, (2) the vessel wall leak-before-break analysis by applying an edge crack solution, and (3) the crack penetration calculation as a result of radiation embrittlement by applying the flaw assessment diagram (FAD). The probability of fracture for the capsule is calculated by using a direct probability integration method instead of the Monte Carlo simulation method used by the PRAISE Code or the FAVOR Code developed in Oak Ridge. The probability of fracture as a function of radiation embrittlement is obtained. The leak before break analysis indicates that the vessel will fail by leak before fail by catastrophic fracture. A mass spectrometer will be installed to monitor the leak of hydrogen circulating within the moderator.

  6. Thermal hydraulic analysis of two-phase closed thermosyphon cooling system for new cold neutron source moderator of Breazeale research reactor at Penn State

    NASA Astrophysics Data System (ADS)

    Habte, Melaku

    A cold neutron source cooling system is required for the Penn State's next generation cold neutron source facility that can accommodate a variable heat load up to about ˜10W with operating temperature of about 28K. An existing cold neutron source cooling system operating at the University of Texas Cold Neutron Source (TCNS) facility failed to accommodate heat loads upwards of 4W with the moderator temperature reaching a maximum of 44K, which is the critical temperature for the operating fluid neon. The cooling system that was used in the TCNS cooling system was a two-phase closed thermosyphon with a reservoir (TPCTR). The reservoir containing neon gas is kept at room temperature. In this study a detailed thermal analysis of the fundamental operating principles of a TPCTR were carried out. A detailed parametric study of the various geometric and thermo-physical factors that affect the limits of the operational capacity of the TPCTR investigated. A CFD analysis is carried out in order to further refine the heat transfer analysis and understand the flow structure inside the thermosyphon and the two-phase nucleate boiling in the evaporator section of the thermosyphon. In order to help the new design, a variety of ways of increasing the operating range and heat removal capacity of the TPCTR cooling system were analyzed so that it can accommodate the anticipated heat load of 10W or more. It is found, for example, that doubling the pressure of the system will increase the capacity index zeta by 50% for a system with an initial fill ratio FR of 1. A decrease in cryorefrigeration performance angle increases the capacity index. For example taking the current condition of the TCNS system and reducing the angle from the current value of ˜700 by half (˜350) will increase the cooling power 300%. Finally based on detailed analytic and CFD analysis the best operating condition were proposed.

  7. The University of Texas Cold Neutron Source

    NASA Astrophysics Data System (ADS)

    Ünlü, Kenan; Ríos-Martínez, Carlos; Wehring, Bernard W.

    1994-12-01

    A cold neutron source has been designed, constructed, and tested by the Nuclear Engineering Teaching Laboratory (NETL) at The University of Texas at Austin. The Texas Cold Neutron Source (TCNS) is located in one of the beam ports of the NETL 1-MW TRIGA Mark II research reactor. The main components of the TCNS are a cooled moderator, a heat pipe, a cryogenic refrigerator, and a neutron guide. 80 ml of mesitylene moderator are maintained at about 30 K in a chamber within the reactor graphite reflector by the heat pipe and cryogenic refrigerator. The heat pipe is a 3-m long aluminum tube that contains neon as the working fluid. The cold neutrons obtained from the moderator are transported by a curved 6-m long neutron guide. This neutron guide has a radius of curvature of 300 m, a 50 × 15 mm cross-section, 58Ni coating, and is separated into three channels. The TCNS will provide a low-background subthermal neutron beam for neutron capture and scattering research. After the installation of the external portion of the neutron guide, a neutron focusing system and a Prompt Gamma Activation Analysis facility will be set up at the TCNS.

  8. Design Analyses and Shielding of HFIR Cold Neutron Scattering Instruments

    SciTech Connect

    Gallmeier, F.X.; Selby, D.L.; Winn, B.; Stoica, D.; Jones, A.B.; Crow, L.

    2011-07-01

    Research reactor geometries and special characteristics present unique dosimetry analysis and measurement issues. The introduction of a cold neutron moderator and the production of cold neutron beams at the Oak Ridge National Laboratory High Flux Isotope Reactor have created the need for modified methods and devices for analyzing and measuring low energy neutron fields (0.01 to 100 meV). These methods include modifications to an MCNPX version to provide modeling of neutron mirror reflection capability. This code has been used to analyze the HFIR cold neutron beams and to design new instrument equipment that will use the beams. Calculations have been compared with time-of-flight measurements performed at the start of the neutron guides and at the end of one of the guides. The results indicate that we have a good tool for analyzing the transport of these low energy beams through neutron mirror and guide systems for distance up to 60 meters from the reactor. (authors)

  9. Neutron interferometry with cold stage

    NASA Astrophysics Data System (ADS)

    Mineeva, Taisiya; Arif, M.; Huber, M. G.; Shahi, C. B.; Clark, C. W.; Cory, D. G.; Nsofini, J.; Sarenac, D.; Pushin, D. A.

    Neutron interferometry (NI) is amongst the most precise methods for characterizing neutron interactions by measuring the relative difference between two neutron paths, one of which contains a sample-of-interest. Because neutrons carry magnetic moment and are deeply penetrating, they are excellent probes to investigate properties of magnetic materials. The advantage of NI is its unique sensitivity which allows to directly measure magnetic and structural transitions in materials. Up to now NI has been sparingly used in material research due to its sensitivity to environmental noise. However, recent successes in implementing Quantum Error Correction principles lead to an improved NI design making it robust against mechanical vibrations. Following these advances, a new user facility at the National Institute for Standards and Technology was built to study condensed matter applications, biology and quantum physics. Incorporating cold sample stage inside NI is the first of its kind experiment which can be carried out on large range of temperatures down to 4K. Upon successful realization, it will open new frontiers to characterize magnetic domains, phase transitions and spin properties in a variety of materials such as, for example, iron-based superconductors and spintronic materials. Supported in part by CERC, CIFAR, NSERC and CREATE.

  10. A neutron spectrometer using nested moderators.

    PubMed

    Dubeau, J; Hakmana Witharana, S S; Atanackovic, J; Yonkeu, A; Archambault, J P

    2012-06-01

    The design, simulation results and measurements of a new neutron energy spectrometer are presented. The device, which may be called NNS, for Nested Neutron Spectrometer, works under the same principles as a Bonner Sphere Spectrometer (BSS) System, i.e. whereby a thermal neutron detector is surrounded by a polyethylene moderator. However, the moderator is cylindrical in shape. The different thicknesses of moderator are created by inserting one cylinder into another, much like nested Russian dolls. This design results in a much lighter instrument that is also easier to use in the field. Simulations and measurements show that, despite its shape, the device can be made to offer a near angular isotropic response to neutrons and that unfolded neutron spectra are in agreement with those obtained with a more traditional BSS.

  11. International workshop on cold neutron sources

    SciTech Connect

    Russell, G.J.; West, C.D. )

    1991-08-01

    The first meeting devoted to cold neutron sources was held at the Los Alamos National Laboratory on March 5--8, 1990. Cosponsored by Los Alamos and Oak Ridge National Laboratories, the meeting was organized as an International Workshop on Cold Neutron Sources and brought together experts in the field of cold-neutron-source design for reactors and spallation sources. Eighty-four people from seven countries attended. Because the meeting was the first of its kind in over forty years, much time was spent acquainting participants with past and planned activities at reactor and spallation facilities worldwide. As a result, the meeting had more of a conference flavor than one of a workshop. The general topics covered at the workshop included: Criteria for cold source design; neutronic predictions and performance; energy deposition and removal; engineering design, fabrication, and operation; material properties; radiation damage; instrumentation; safety; existing cold sources; and future cold sources.

  12. Cold moderator test facilities working group

    SciTech Connect

    Bauer, Guenter S.; Lucas, A. T.

    1997-09-01

    The working group meeting was chaired by Bauer and Lucas.Testing is a vital part of any cold source development project. This applies to specific physics concept verification, benchmarking in conjunction with computer modeling and engineering testing to confirm the functional viability of a proposed system. Irradiation testing of materials will always be needed to continuously extend a comprehensive and reliable information database. An ever increasing worldwide effort to enhance the performance of reactor and accelerator based neutron sources, coupled with the complexity and rising cost of building new generation facilities, gives a new dimension to cold source development and testing programs. A stronger focus is now being placed on the fine-tuning of cold source design to maximize its effectiveness in fully exploiting the facility. In this context, pulsed spallation neutron sources pose an extra challenge due to requirements regarding pulse width and shape which result from a large variety of different instrument concepts. The working group reviewed these requirements in terms of their consequences on the needs for testing equipment and compiled a list of existing and proposed facilities suitable to carry out the necessary development work.

  13. Neutron measurements in search of cold fusion

    SciTech Connect

    Anderson, R.E.; Goulding, C.A.; Johnson, M.W.; Butterfield, K.B.; Gottesfeld, S.; Baker, D.A.; Springer, T.E.; Garzon, F.H.; Bolton, R.D.; Leonard, E.M.; Chancellor, T.

    1990-01-01

    We have conducted a research for neutron emission from cold fusion systems of the electrochemical type and, to a lesser extent, the high-pressure gas cell type. Using a high-efficiency well counter and an NE 213 scintillator, the experiments were conducted on the earth's surface and in a shielded cave approximately 50 ft underground. After approximately 6500 h of counting time, we have obtained no evidence for cold fusion processes leading to neutron production. However, we have observed all three types of neutron data that have been presented as evidence for cold fusion: large positive fluctuations in the neutron counting rate, weak peaks near 2.5 MeV in the neutron energy spectrum, and bursts of up to 145 neutrons in 500-{mu}s intervals. The data were obtained under circumstances that clearly show our results to be data encountered as a part of naturally occurring neutron background, which is due primarily to cosmic rays. Thus, observing these types of data does not, of itself, provide evidence for the existence of cold fusion processes. Artifacts in the data that were due to counter misbehavior were also to lead to long-term neutron bursts'' whose time duration varied from several hours to several days. We conclude that any experiments which attempt to observe neutron emission must include strong steps to ensure that the experiments deal adequately with both cosmic-ray processes and counter misbehavior. 13 refs., 14 figs.

  14. Improved cold-neutron prompt gamma spectrometer

    SciTech Connect

    Lindstrom, R.M.; Paul, R.L.; Heald, A.E.; Langland, J.K.

    1996-12-31

    The cold-neutron prompt-gamma activation analysis (PGAA) spectrometer at the National Institute of Standard and Technology (NIST) has been rebuilt to take advantage of the newly installed LH{sub 2} cold neutron source at the NIST reactor. The new source, a 32-cm-o.d., 2-cm-thick spherical shell of liquid hydrogen, produces a higher neutron density at longer wave-length than did the D{sub 2}O ice source that has been in use since 1987. At the PGAA spectrometer, located 41 m from the cold source on neutron guide NG7, the effective neutron fluence rate (using s, = 98.6 b for gold) was measured to be 8 x 10{sup 8} cm{sup -2}{center_dot}s{sup -1}, a factor of 3 higher at the same reactor power (20 MW) than before.

  15. HEAVY WATER MODERATED NEUTRONIC REACTOR

    DOEpatents

    Szilard, L.

    1958-04-29

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

  16. LIGHT WATER MODERATED NEUTRONIC REACTOR

    DOEpatents

    Christy, R.F.; Weinberg, A.M.

    1957-09-17

    A uranium fuel reactor designed to utilize light water as a moderator is described. The reactor core is in a tank at the bottom of a substantially cylindrical cross-section pit, the core being supported by an apertured grid member and comprised of hexagonal tubes each containing a pluralily of fuel rods held in a geometrical arrangement between end caps of the tubes. The end caps are apertured to permit passage of the coolant water through the tubes and the fuel elements are aluminum clad to prevent corrosion. The tubes are hexagonally arranged in the center of the tank providing an amulus between the core and tank wall which is filled with water to serve as a reflector. In use, the entire pit and tank are filled with water in which is circulated during operation by coming in at the bottom of the tank, passing upwardly through the grid member and fuel tubes and carried off near the top of the pit, thereby picking up the heat generated by the fuel elements during the fission thereof. With this particular design the light water coolant can also be used as the moderator when the uranium is enriched by fissionable isotope to an abundance of U/sup 235/ between 0.78% and 2%.

  17. Cold source moderator vessel development for the High Flux Isotope Reactor: Thermal-hydraulic studies

    SciTech Connect

    Williams, P.T.; Lucas, A.T.; Wendel, M.W.

    1998-07-01

    A project is underway at Oak Ridge National Laboratory (ORNL) to design, test, and install a cold neutron source facility in the High Flux Isotope Reactor (HFIR). This new cold source employs supercritical hydrogen at cryogenic temperatures both as the medium for neutron moderation and as the working fluid for removal of internally-generated nuclear heating. The competing design goals of minimizing moderator vessel mass and providing adequate structural integrity for the vessel motivated the requirement of detailed multidimensional thermal-hydraulic analyses of the moderator vessel as a critical design subtask. This paper provides a summary review of the HFIR cold source moderator vessel design and a description of the thermal-hydraulic studies that were carried out to support the vessel development.

  18. Spectroscopy with cold and ultra-cold neutrons

    NASA Astrophysics Data System (ADS)

    Abele, Hartmut; Jenke, Tobias; Konrad, Gertrud

    2015-05-01

    We present two new types of spectroscopy methods for cold and ultra-cold neutrons. The first method, which uses the R×B drift effect to disperse charged particles in a uniformly curved magnetic field, allows to study neutron β-decay. We aim for a precision on the 10-4 level. The second method that we refer to as gravity resonance spectroscopy (GRS) allows to test Newton's gravity law at short distances. At the level of precision we are able to provide constraints on any possible gravity-like interaction. In particular, limits on dark energy chameleon fields are improved by several orders of magnitude.

  19. Outer crust of nonaccreting cold neutron stars

    NASA Astrophysics Data System (ADS)

    Rüster, Stefan B.; Hempel, Matthias; Schaffner-Bielich, Jürgen

    2006-03-01

    The properties of the outer crust of nonaccreting cold neutron stars are studied by using modern nuclear data and theoretical mass tables, updating in particular the classic work of Baym, Pethick, and Sutherland. Experimental data from the atomic mass table from Audi, Wapstra, and Thibault of 2003 are used and a thorough comparison of many modern theoretical nuclear models, both relativistic and nonrelativistic, is performed for the first time. In addition, the influences of pairing and deformation are investigated. State-of-the-art theoretical nuclear mass tables are compared to check their differences concerning the neutron drip line, magic neutron numbers, the equation of state, and the sequence of neutron-rich nuclei up to the drip line in the outer crust of nonaccreting cold neutron stars.

  20. Outer crust of nonaccreting cold neutron stars

    SciTech Connect

    Ruester, Stefan B.; Hempel, Matthias; Schaffner-Bielich, Juergen

    2006-03-15

    The properties of the outer crust of nonaccreting cold neutron stars are studied by using modern nuclear data and theoretical mass tables, updating in particular the classic work of Baym, Pethick, and Sutherland. Experimental data from the atomic mass table from Audi, Wapstra, and Thibault of 2003 are used and a thorough comparison of many modern theoretical nuclear models, both relativistic and nonrelativistic, is performed for the first time. In addition, the influences of pairing and deformation are investigated. State-of-the-art theoretical nuclear mass tables are compared to check their differences concerning the neutron drip line, magic neutron numbers, the equation of state, and the sequence of neutron-rich nuclei up to the drip line in the outer crust of nonaccreting cold neutron stars.

  1. Status and perspective of development of cold moderators at the IBR-2 reactor

    NASA Astrophysics Data System (ADS)

    Kulikov, S.; Shabalin, E.

    2012-03-01

    The modernized IBR-2M reactor will start its operation with three water grooved moderators in 2011. Afterwards, they will be exchanged by a new complex of moderators. The complex consists of three so-called kombi-moderators, each of them containing a pre-moderator, a cold moderator, grooved ambient water moderators and post-moderators. They are mounted onto three moveable trolleys that serve to deliver and install moderators near the reactor core. The project is divided in three stages. In 2012 the first stage of development of complex of moderators will be finished. The water grooved moderator will be replaced with the new kombi-moderator for beams #7, 8, 10, 11. Main parameters of moderators for this direction will be studied then. The next stages will be done for beams #2-3 and for beams #1, 9, 4-6, consequently. Cold moderator chambers at the modernized IBR-2 reactor are filled with thousands of beads (~3.5 - 4 mm in diameter) of moderating material. The cold helium gas flow delivers beads from the charging device to the moderator during the fulfillment process and cools down them during the reactor cycle. The mixture of aromatic hydrocarbons (mesithylen and m-xylen) has been chosen as moderating material. The explanation of the choice of material for novel cold neutron moderators, configuration of moderator complex for the modernized IBR-2 reactor and the main results of optimization of moderator complex for the third stage of moderator development are discussed in the article.

  2. The Los ALamos Neutron Science Center Hydrogen Moderator System

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

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

  3. A Long-Pulse Spallation Source at Los Alamos: Facility description and preliminary neutronic performance for cold neutrons

    SciTech Connect

    Russell, G.J.; Weinacht, D.J.; Pitcher, E.J.; Ferguson, P.D.

    1998-03-01

    The Los Alamos National Laboratory has discussed installing a new 1-MW spallation neutron target station in an existing building at the end of its 800-MeV proton linear accelerator. Because the accelerator provides pulses of protons each about 1 msec in duration, the new source would be a Long Pulse Spallation Source (LPSS). The facility would employ vertical extraction of moderators and reflectors, and horizontal extraction of the spallation target. An LPSS uses coupled moderators rather than decoupled ones. There are potential gains of about a factor of 6 to 7 in the time-averaged neutron brightness for cold-neutron production from a coupled liquid H{sub 2} moderator compared to a decoupled one. However, these gains come at the expense of putting ``tails`` on the neutron pulses. The particulars of the neutron pulses from a moderator (e.g., energy-dependent rise times, peak intensities, pulse widths, and decay constant(s) of the tails) are crucial parameters for designing instruments and estimating their performance at an LPSS. Tungsten is the reference target material. Inconel 718 is the reference target canister and proton beam window material, with Al-6061 being the choice for the liquid H{sub 2} moderator canister and vacuum container. A 1-MW LPSS would have world-class neutronic performance. The authors describe the proposed Los Alamos LPSS facility, and show that, for cold neutrons, the calculated time-averaged neutronic performance of a liquid H{sub 2} moderator at the 1-MW LPSS is equivalent to about 1/4th the calculated neutronic performance of the best liquid D{sub 2} moderator at the Institute Laue-Langevin reactor. They show that the time-averaged moderator neutronic brightness increases as the size of the moderator gets smaller.

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

    NASA Astrophysics Data System (ADS)

    Zimmer, Oliver

    2016-03-01

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

  5. Final report on Seed Money Project 3210-0346: Feasibility study for californium cold neutron source

    SciTech Connect

    Alsmiller, R.G.; Henderson, D.L.; Montgomery, B.H.

    1988-10-01

    A study has been completed of the feasibility and cost of building a cold neutron source that is not dependent on a reactor or accelerator. The neutron source is provided by up to ten /sup 252/Cf capsules, each containing 50 mg of the isotope produced in the High-Flux Isotope Reactor. The neutrons are moderated by heavy water and liquid deuterium to attain, in practice, a peak cold neutron flux of 1.4 /times/ 10/sup 13/ neutrons/(m/sup 2//center dot/s). The new facility would be located in the TURF Californium Facility. The estimated cost of the Californium Cold Neutron Source Facility is $6.5 million. 6 figs., 1 tab.

  6. Materials Selection for the HFIR Cold Neutron Source

    SciTech Connect

    Farrell, K.

    2001-08-24

    In year 2002 the High Flux Isotope Reactor (HFIR) will be fitted with a source of cold neutrons to upgrade and expand its existing neutron scattering facilities. The in-reactor components of the new source consist of a moderator vessel containing supercritical hydrogen gas moderator at a temperature of 20K and pressure of 15 bar, and a surrounding vacuum vessel. They will be installed in an enlarged beam tube located at the site of the present horizontal beam tube, HB-4; which terminates within the reactor's beryllium reflector. These components must withstand exceptional service conditions. This report describes the reasons and factors underlying the choice of 6061-T6 aluminum alloy for construction of the in-reactor components. The overwhelming considerations are the need to minimize generation of nuclear heat and to remove that heat through the flowing moderator, and to achieve a minimum service life of about 8 years coincident with the replacement schedule for the beryllium reflector. 6061-T6 aluminum alloy offers the best combination of low nuclear heating, high thermal conductivity, good fabricability, compatibility with hydrogen, superior cryogenic properties, and a well-established history of satisfactory performance in nuclear environments. These features are documented herein. An assessment is given of the expected performance of each component of the cold source.

  7. Solid methane cold moderator for the IBR-2 reactor

    SciTech Connect

    Beliakov, A. A.; Tretiakov, I. T.; Shabalin, E. P.; Golikov, V. V.; Luschivkov, V I.

    1997-09-01

    The paper describes the research and design work carried out since 1986 at the Frank Laboratory of Neutron Physics of the Joint Institute for Nuclear Research in Dubna to create a cryogenic moderator for the IBR-22 reactor using solid methane as a moderating substance.

  8. Thermal-hydraulic studies of the Advanced Neutron Source cold source

    SciTech Connect

    Williams, P.T.; Lucas, A.T.

    1995-08-01

    The Advanced Neutron Source (ANS), in its conceptual design phase at Oak Ridge National Laboratory, was to be a user-oriented neutron research facility producing the most intense steady-state flux of thermal and cold neutrons in the world. Among its many scientific applications, the production of cold neutrons was a significant research mission for the ANS. The cold neutrons come from two independent cold sources positioned near the reactor core. Contained by an aluminum alloy vessel, each cold source is a 410-mm-diam sphere of liquid deuterium that functions both as a neutron moderator and a cryogenic coolant. With nuclear heating of the containment vessel and internal baffling, steady-state operation requires close control of the liquid deuterium flow near the vessel`s inner surface. Preliminary thermal-hydraulic analyses supporting the cold source design were performed with heat conduction simulations of the vessel walls and multidimensional computational fluid dynamics simulations of the liquid deuterium flow and heat transfer. This report presents the starting phase of a challenging program and describes the cold source conceptual design, the thermal-hydraulic feasibility studies of the containment vessel, and the future computational and experimental studies that were planned to verify the final design.

  9. Self-regulating characteristics of a cold neutron source with a closed-thermosiphon

    NASA Astrophysics Data System (ADS)

    Kawai, T.; Utsuro, M.; Maeda, Y.; Ebisawa, T.; Akiyoshi, T.; Yamaoka, H.; Okamoto, S.

    1989-04-01

    This report describes self-regulating properties of the Kyoto University Reactor (KUR) Cold Neutron Source (CNS), which is cooled by a closed-thermosiphon loop of hydrogen, as are most of the CNS constructed recently. The circular moderator transfer tube is in a plane inclined about 14° to the horizontal plane. The hydrogen-helium cryogenic system of the CNS shows a self-regulating characteristic under thermal disturbances, if they are smaller than about 30% of the practical allowable heat load, 300 W at 25 K in our case. This self-regulating characteristic has been confirmed from Bode's diagram of the hydrogen pressure response in the reservoir tank to the heat load modulation. Due to this property, the liquid level in the moderator cell is kept almost constant during long term operation of the reactor. Measurements of the vertical distribution of the cold neutron flux from the moderator cell showed that a sufficient amount of liquid was stored in the cell and the ratio of the fraction of cold neutrons in the cold moderator to that in the ambient moderator was measured to be about 20 where the wavelengths are longer than 6 Å using liquid hydrogen as a moderator.

  10. Enhancing Neutron Beam Production with a Convoluted Moderator

    SciTech Connect

    Iverson, Erik B; Baxter, David V; Muhrer, Guenter; Ansell, Stuart; Gallmeier, Franz X; Dalgliesh, Robert; Lu, Wei; Kaiser, Helmut

    2014-10-01

    We describe a new concept for a neutron moderating assembly resulting in the more efficient production of slow neutron beams. The Convoluted Moderator, a heterogeneous stack of interleaved moderating material and nearly transparent single-crystal spacers, is a directionally-enhanced neutron beam source, improving beam effectiveness over an angular range comparable to the range accepted by neutron beam lines and guides. We have demonstrated gains of 50% in slow neutron intensity for a given fast neutron production rate while simultaneously reducing the wavelength-dependent emission time dispersion by 25%, both coming from a geometric effect in which the neutron beam lines view a large surface area of moderating material in a relatively small volume. Additionally, we have confirmed a Bragg-enhancement effect arising from coherent scattering within the single-crystal spacers. We have not observed hypothesized refractive effects leading to additional gains at long wavelength. In addition to confirmation of the validity of the Convoluted Moderator concept, our measurements provide a series of benchmark experiments suitable for developing simulation and analysis techniques for practical optimization and eventual implementation at slow neutron source facilities.

  11. The Design and Construction of a Cold Neutron Source for Use in the Cornell University Triga Reactor

    NASA Astrophysics Data System (ADS)

    Young, Lydia Jane

    A cold neutron source has been designed and constructed for insertion into the 6"-radial beam port of the Cornell University TRIGA reactor for use with a neutron guide tube system. The main differences between this cold source and other existing sources are the use of heat conduction as the method of cooling and the use of mesitylene (1,3,5 -trimethylbenzene; melting point, 228(DEGREES)K; boiling point, 437(DEGREES)K) as the moderating material. This thesis describes the design and construction details of the cold neutron source, discusses its safety aspects, and presents its cryogenic performance curves and also the results of a test of its neutron moderating ability. A closed-cycle helium gas refrigerator, located outside the reactor shielding, cools the 500 cm('3) moderator chamber and its surrounding heat shield by heat conduction through two meters of copper and rod tubing. Moderator temperatures of 23 (+OR-) 3(DEGREES)K have been achieved. Mesitylene, a hydrocarbon, is an effective cold moderator because even at low temperatures the weakly hindered rotational motions of its methyl groups enable the absorption of small amounts of energy ((LESSTHEQ) 0.005 eV) from neutrons. The use of mesitylene simplifies the cold source design because it is a liquid at room temperature and thus, the usual design safeguards required for sources using gaseous moderators are not necessary. Moreover, the flammability of mesitylene is much smaller than that of hydrogen and methane, which are the commonly used cold moderators. A method of transferring and handling the mesitylene, a carcinogen, was devised to ensure minimal contact with this substance. To test the neutron moderating ability of the cold neutron source, an out-of-reactor neutron transmission experiment was performed with the moderator chamber first at room temperature and then at about 23(DEGREES)K. The results indicate that the neutron energy spectrum is strongly shifted to lower energies when the chamber is cold

  12. Optimizing moderator dimensions for neutron scattering at the spallation neutron source.

    PubMed

    Zhao, J K; Robertson, J L; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernard W

    2013-12-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source (SNS). In a recent study of the planned second target station at the SNS facility, we have found that the dimensions of a moderator play a significant role in determining its surface brightness. A smaller moderator may be significantly brighter over a smaller viewing area. One of the immediate implications of this finding is that for modern neutron scattering instrument designs, moderator dimensions and brightness have to be incorporated as an integrated optimization parameter. Here, we establish a strategy of matching neutron scattering instruments with moderators using analytical and Monte Carlo techniques. In order to simplify our treatment, we group the instruments into two broad categories: those with natural collimation and those that use neutron guide systems. For instruments using natural collimation, the optimal moderator selection depends on the size of the moderator, the sample, and the moderator brightness. The desired beam divergence only plays a role in determining the distance between sample and moderator. For instruments using neutron optical systems, the smallest moderator available that is larger than the entrance dimension of the closest optical element will perform the best (assuming, as is the case here that smaller moderators are brighter).

  13. Study of neutron focusing at the Texas Cold Neutron Source. Final report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1996-12-19

    The goals of this three-year study were: (1) design a neutron focusing system for use with the Texas Cold Neutron Source (TCNS) to produce an intense beam of cold neutrons appropriate for prompt gamma activation analysis (PGAA); (2) orchestrate the construction of the focusing system, integrate it into the TCNS neutron guide complex, and measure its performance; and (3) design, setup, and test a cold-neutron PGAA system which utilizes the guided focused cold neutron beam. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which the authors wrote to trace neutrons through the curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, the authors obtained gains of 3 to 5 for 4 different converging guide geometries. During the second year of the DOE grant, the subject of this final report, Ovonic Synthetic Materials Company was contracted to build a converging neutron guide focusing system to the specifications. Considerable time and effort were spent working with Ovonics on selecting the materials for the converging neutron guide system. The major portion of the research on the design of a cold-neutron PGAA system was also completed during the second year. At the beginning of the third year of the grant, a converging neutron guide focusing system had been ordered, and a cold-neutron PGAA system had been designed. Since DOE did not fund the third year, there was no money to purchase the required equipment for the cold-neutron PGAA system and no money to perform tests of either the converging neutron guide or the cold-neutron PGAA system. The research already accomplished would have little value without testing the systems which had been designed. Thus the project was continued at a pace that could be sustained with internal funding.

  14. Improvement of the cold neutron beam line (CN-3) in KUR for neutron optical device development

    NASA Astrophysics Data System (ADS)

    Kawabata, Yuji; Hino, Masahiro; Tasaki, Seiji; Ebisawa, Toru; Maruyama, Ryuji; Horie, Takashi

    2002-01-01

    The cold neutron beam line CN-3 in Kyoto University Reactor (KUR) is being renewed for dedicating to the development of neutron optical devices. CN-3 has a supermirror guide tube with the cross-section of 20 mm (width)× 90 mm (height), and the wide-band neutron spectrum is available. New beam lines are prepared for both time-of-flight (TOF) and monochromatic experiments including a neutron reflectivity measurement. It has a polarized neutron option with a very low magnetic field to cope with polarized neutron devices. In particular, the TOF mode will be used for developing devices, which are suitable for pulsed neutron sources. Cold neutron radiography is also available within a space of 1 m×0.8 m. A neutron imaging plate system is prepared as the neutron imaging detection.

  15. Development of cold neutron depth profiling system at HANARO

    NASA Astrophysics Data System (ADS)

    Park, B. G.; Sun, G. M.; Choi, H. D.

    2014-07-01

    A neutron depth profiling (NDP) system has been designed and developed at HANARO, a 30 MW research reactor at the Korea Atomic Energy Research Institute (KAERI). The KAERI-NDP system utilizes cold neutrons that are transported along the CG1 neutron guide from the cold neutron source and it consists of a neutron beam collimator, a target chamber, a beam stopper, and charged particle detectors along with NIM-standard modules for charged particle pulse-height analysis. A 60 cm in diameter stainless steel target chamber was designed to control the positions of the sample and detector. The energy distribution of the cold neutron beam at the end of the neutron guide was calculated by using the Monte Carlo simulation code McStas, and a neutron flux of 1.8×108 n/cm2 s was determined by using the gold foil activation method at the sample position. The performance of the charged particle detection of the KAERI-NDP system was tested by using Standard Reference Materials. The energy loss spectra of alpha particles and Li ions emitted from 10B, which was irradiated by cold neutrons, were measured. The measured peak concentration and the areal density of 10B in the Standard Reference Material are consistent with the reference values within 1% and 3.4%, respectively.

  16. Slower, colder, longer : prospects for a very cold neutron source.

    SciTech Connect

    Micklich, B. J.; Carpenter, J. M.; Intense Pulsed Neutron Source

    2007-01-01

    The motivation for our study is to establish the prospects for a neutron source providing intense pulsed beams with spectra as cold as is realistic. The scientific motivation is to serve applications in nanoscience, biology and technology.

  17. Expansion vessel for supercritical hydrogen in a spallation neutron source moderator circuit

    NASA Astrophysics Data System (ADS)

    Klaus, M.; Eisenhut, S.; Quack, H.; Haberstroh, C.; Bessler, Y.

    2015-12-01

    High-energy neutrons are being decelerated by passing through supercritical parahydrogen circulated by pumps in a closed loop. Fluctuations in neutron heat load cause changes of the circuits’ local and average temperature and hence significant pressure variations caused by the almost incompressible behavior of hydrogen. Solutions by adding a variable volume in form of a helium gas-backed metal bellow to mitigate pressure deviations are already in use. This paper presents an alternative approach by introducing a vertical storage vessel for supercritical hydrogen in a side branch of the moderator loop, with cold incompressible high density hydrogen at the bottom and warmer compressible lower density hydrogen at the top.

  18. Global transcriptional profiling of a cold-tolerant rice variety under moderate cold stress reveals different cold stress response mechanisms.

    PubMed

    Zhao, Junliang; Zhang, Shaohong; Yang, Tifeng; Zeng, Zichong; Huang, Zhanghui; Liu, Qing; Wang, Xiaofei; Leach, Jan; Leung, Hei; Liu, Bin

    2015-07-01

    Gene expression profiling under severe cold stress (4°C) has been conducted in plants including rice. However, rice seedlings are frequently exposed to milder cold stresses under natural environments. To understand the responses of rice to milder cold stress, a moderately low temperature (8°C) was used for cold treatment prior to genome-wide profiling of gene expression in a cold-tolerant japonica variety, Lijiangxintuanheigu (LTH). A total of 5557 differentially expressed genes (DEGs) were found at four time points during moderate cold stress. Both the DEGs and differentially expressed transcription factor genes were clustered into two groups based on their expression, suggesting a two-phase response to cold stress and a determinative role of transcription factors in the regulation of stress response. The induction of OsDREB2A under cold stress is reported for the first time in this study. Among the anti-oxidant enzyme genes, glutathione peroxidase (GPX) and glutathione S-transferase (GST) were upregulated, suggesting that the glutathione system may serve as the main reactive oxygen species (ROS) scavenger in LTH. Changes in expression of genes in signal transduction pathways for auxin, abscisic acid (ABA) and salicylic acid (SA) imply their involvement in cold stress responses. The induction of ABA response genes and detection of enriched cis-elements in DEGs suggest that ABA signaling pathway plays a dominant role in the cold stress response. Our results suggest that rice responses to cold stress vary with the specific temperature imposed and the rice genotype.

  19. Materials for cold neutron sources: Cryogenic and irradiation effects

    SciTech Connect

    Alexander, D.J.

    1990-01-01

    Materials for the construction of cold neutron sources must satisfy a range of demands. The cryogenic temperature and irradiation create a severe environment. Candidate materials are identified and existing cold sources are briefly surveyed to determine which materials may be used. Aluminum- and magnesium-based alloys are the preferred materials. Existing data for the effects of cryogenic temperature and near-ambient irradiation on the mechanical properties of these alloys are briefly reviewed, and the very limited information on the effects of cryogenic irradiation are outlined. Generating mechanical property data under cold source operating conditions is a daunting prospect. It is clear that the cold source material will be degraded by neutron irradiation, and so the cold source must be designed as a brittle vessel. The continued effective operation of many different cold sources at a number of reactors makes it clear that this can be accomplished. 46 refs., 8 figs., 2 tab.

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

    NASA Astrophysics Data System (ADS)

    Gozani, Tsahi; King, Michael J.

    2016-01-01

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

  1. The NIST NBSR and Cold Neutron Research Facility

    SciTech Connect

    Rush, J.J.

    1994-12-31

    The 20 MW Neutron Beam Split-Core Reactor (NBSR) has nine radial thermal beam tubes, and a large, highly accessible (35cm) cold source serving an extensive network of eight guide tubes. In operation or under construction are twenty-five neutron beam instruments (20 for neutron scattering) and about a dozen other facilities for neutron trace analysis, dosimetry and irradiation. The 6 x 15cm cold neutron guides are coated with {sup 58}Ni, and the last three being installed this fall are coated top and bottom with supermirrors for further increases in intensity. The new semi-spherical liquid hydrogen source will be described, along with the eight scattering instruments (reflectometry, SANS and high-resolution spectroscopy) which have, or will have, an extensive use in biological research. These instruments will likely provide the best overall capability in the U.S. for the next decade for a number of applications in biomolecular structure and dynamics.

  2. High Flux Isotope Reactor cold neutron source reference design concept

    SciTech Connect

    Selby, D.L.; Lucas, A.T.; Hyman, C.R.

    1998-05-01

    In February 1995, Oak Ridge National Laboratory`s (ORNL`s) deputy director formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. In May 1995, a team was formed to examine the feasibility of retrofitting a liquid hydrogen (LH{sub 2}) cold source facility into an existing HFIR beam tube. The results of this feasibility study indicated that the most practical location for such a cold source was the HB-4 beam tube. This location provides a potential flux environment higher than the Institut Laue-Langevin (ILL) vertical cold source and maximizes the space available for a future cold neutron guide hall expansion. It was determined that this cold neutron beam would be comparable, in cold neutron brightness, to the best facilities in the world, and a decision was made to complete a preconceptual design study with the intention of proceeding with an activity to install a working LH{sub 2} cold source in the HFIR HB-4 beam tube. During the development of the reference design the liquid hydrogen concept was changed to a supercritical hydrogen system for a number of reasons. This report documents the reference supercritical hydrogen design and its performance. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and testing, (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the conceptual design phase and establishes the baseline reference concept.

  3. Biomembranes research using thermal and cold neutrons.

    PubMed

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

    2015-11-01

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

  4. Biomembranes research using thermal and cold neutrons.

    PubMed

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

    2015-11-01

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

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

    DOEpatents

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

    1981-01-01

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

  6. Variations in mental performance under moderate cold stress

    NASA Astrophysics Data System (ADS)

    Sharma, V. M.; Panwar, M. R.

    1987-03-01

    Effects of moderate cold stress on reasoning ability, associative learning and critical flicker frequncy of Indian subjects were studied by exposing them to 25‡C,. 20‡C, 15‡C and 10‡C for three hours. A second set of experiments was also conducted to confirm the conclusions of the first by using the same temperatures and duration of exposure. However, not only the sample used in the second case was larger and different but also the mental functions tested were numerical ability, running memory and mental alertness. It has been concluded that there is a significant impairment of simple cognitive functions at 15‡C which is 10‡C lower than their most comfortable temperature of 25‡C.

  7. Introducing single-crystal scattering and optical potentials into MCNPX: Predicting neutron emission from a convoluted moderator

    DOE PAGES

    Gallmeier, F. X.; Iverson, E. B.; Lu, W.; Baxter, D. V.; Muhrer, G.; Ansell, S.

    2016-01-08

    Neutron transport simulation codes are an indispensable tool used for the design and construction of modern neutron scattering facilities and instrumentation. It has become increasingly clear that some neutron instrumentation has started to exploit physics that is not well-modelled by the existing codes. Particularly, the transport of neutrons through single crystals and across interfaces in MCNP(X), Geant4 and other codes ignores scattering from oriented crystals and refractive effects, and yet these are essential ingredients for the performance of monochromators and ultra-cold neutron transport respectively (to mention but two examples). In light of these developments, we have extended the MCNPX codemore » to include a single-crystal neutron scattering model and neutron reflection/refraction physics. Furthermore, we have also generated silicon scattering kernels for single crystals of definable orientation with respect to an incoming neutron beam. As a first test of these new tools, we have chosen to model the recently developed convoluted moderator concept, in which a moderating material is interleaved with layers of perfect crystals to provide an exit path for neutrons moderated to energies below the crystal s Bragg cut off at locations deep within the moderator. Studies of simple cylindrical convoluted moderator systems of 100 mm diameter and composed of polyethylene and single crystal silicon were performed with the upgraded MCNPX code and reproduced the magnitude of effects seen in experiments compared to homogeneous moderator systems. Applying different material properties for refraction and reflection, and by replacing the silicon in the models with voids, we show that the emission enhancements seen in recent experiments are primarily caused by the transparency of the silicon/void layers. Finally the convoluted moderator experiments described by Iverson et al. were simulated and we find satisfactory agreement between the measurement and the results of

  8. Introducing single-crystal scattering and optical potentials into MCNPX: Predicting Neutron Emission from a Convoluted Moderator

    SciTech Connect

    Gallmeier, Franz X; Iverson, Erik B; Lu, Wei; Baxter, David V; Muhrer, Guenter; Ansell, Stuart

    2016-01-01

    Neutron transport simulation codes are an indispensable tool used for the design and construction of modern neutron scattering facilities and instrumentation. Recently, it has become increasingly clear that some neutron instrumentation has started to exploit physics that is not well-modelled by the existing codes. In particular, the transport of neutrons through single crystals and across interfaces in MCNP(X), Geant4 and other codes ignores scattering from oriented crystals and refractive effects, and yet these are essential ingredients for the performance of monochromators and ultra-cold neutron transport respectively (to mention but two examples). In light of these developments, we have extended the MCNPX code to include a single-crystal neutron scattering model and neutron reflection/refraction physics. We have also generated silicon scattering kernels for single crystals of definable orientation with respect to an incoming neutron beam. As a first test of these new tools, we have chosen to model the recently developed convoluted moderator concept, in which a moderating material is interleaved with layers of perfect crystals to provide an exit path for neutrons moderated to energies below the crystal s Bragg cut off at locations deep within the moderator. Studies of simple cylindrical convoluted moderator systems of 100 mm diameter and composed of polyethylene and single crystal silicon were performed with the upgraded MCNPX code and reproduced the magnitude of effects seen in experiments compared to homogeneous moderator systems. Applying different material properties for refraction and reflection, and by replacing the silicon in the models with voids, we show that the emission enhancements seen in recent experiments are primarily caused by the transparency of the silicon/void layers. Finally the convoluted moderator experiments described by Iverson et al. were simulated and we find satisfactory agreement between the measurement and the results of simulations

  9. Biomembranes research using thermal and cold neutrons

    DOE PAGES

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

    2015-08-01

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

  10. Biomembranes research using thermal and cold neutrons

    SciTech Connect

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

    2015-08-01

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

  11. Measurement of the Neutron's Beta Decay Asymmetry using Polarized Ultra-cold Neutrons

    NASA Astrophysics Data System (ADS)

    Vogelaar, R. B.; Makela, M.; Pitt, M.; Carr, R.; Filippone, B.; Ito, T. M.; Martin, J. W.; McKeown, R.; Tipton, B.; Yuan, J.; Geltenbort, P.; Soyama, K.; Bowles, T.; Fowler, M.; Hill, R.; Hime, A.; Hogan, G.; Kirch, K.; Lamoreaux, S.; Morris, C.; Pichlmaeir, A.; Saunders, A.; Seestrom, S.; Walstrom, P.; Wilhelmy, J.; Alduschenkov, A.; Kharitonov, A.; Lassakov, M.; Rudnev, Yu.; Serebrov, A.; Vasilev, A.; Hoedel, S.; Liu, C.-Y.; Smith, D.; Young, A. R.; Kitagaki, T.; Asahi, K.; Hino, M.; Kawai, T.; Utsuro, M.; Garcia, A.; Miyachi, T.

    2001-04-01

    A measurement of the beta decay asymmetry in polarized neutron decay, when combined with the neutron lifetime, provides a determination of the fundamental vector and axial vector weak coupling constants, GV and G_A. The value of GV can be compared to that obtained from other observables to check the consistency of the electroweak Standard Model and to search for physics beyond it. We describe a new neutron beta decay asymmetry experiment being prepared at LANSCE. The experiment will use ultra-cold neutrons (UCN) from a recently developed spallation driven solid deuterium UCN source. UCNs can be produced with 100polarization, and they can be efficiently transported over long distances, thus insuring a low background environment. These properties provide some important advantages over previous neutron beta decay asymmetry experiments performed using cold neutron beams from reactors. We will report on the details of the experimental setup and the expected precision.

  12. Introducing single-crystal scattering and optical potentials into MCNPX: Predicting neutron emission from a convoluted moderator

    NASA Astrophysics Data System (ADS)

    Gallmeier, F. X.; Iverson, E. B.; Lu, W.; Baxter, D. V.; Muhrer, G.; Ansell, S.

    2016-04-01

    Neutron transport simulation codes are indispensable tools for the design and construction of modern neutron scattering facilities and instrumentation. Recently, it has become increasingly clear that some neutron instrumentation has started to exploit physics that is not well-modeled by the existing codes. In particular, the transport of neutrons through single crystals and across interfaces in MCNP(X), Geant4, and other codes ignores scattering from oriented crystals and refractive effects, and yet these are essential phenomena for the performance of monochromators and ultra-cold neutron transport respectively (to mention but two examples). In light of these developments, we have extended the MCNPX code to include a single-crystal neutron scattering model and neutron reflection/refraction physics. We have also generated silicon scattering kernels for single crystals of definable orientation. As a first test of these new tools, we have chosen to model the recently developed convoluted moderator concept, in which a moderating material is interleaved with layers of perfect crystals to provide an exit path for neutrons moderated to energies below the crystal's Bragg cut-off from locations deep within the moderator. Studies of simple cylindrical convoluted moderator systems of 100 mm diameter and composed of polyethylene and single crystal silicon were performed with the upgraded MCNPX code and reproduced the magnitude of effects seen in experiments compared to homogeneous moderator systems. Applying different material properties for refraction and reflection, and by replacing the silicon in the models with voids, we show that the emission enhancements seen in recent experiments are primarily caused by the transparency of the silicon and void layers. Finally we simulated the convoluted moderator experiments described by Iverson et al. and found satisfactory agreement between the measurements and the simulations performed with the tools we have developed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  14. Cryostat system for investigation on new neutron moderator materials at reactor TRIGA PUSPATI

    NASA Astrophysics Data System (ADS)

    Dris, Zakaria bin; Mohamed, Abdul Aziz bin; Hamid, Nasri A.; Azman, Azraf; Ahmad, Megat Harun Al Rashid Megat; Jamro, Rafhayudi; Yazid, Hafizal

    2016-01-01

    A simple continuous flow (SCF) cryostat was designed to investigate the neutron moderation of alumina in high temperature co-ceramic (HTCC) and polymeric materials such as Teflon under TRIGA neutron environment using a reflected neutron beam from a monochromator. Cooling of the cryostat will be carried out using liquid nitrogen. The cryostat will be built with an aluminum holder for moderator within stainless steel cylinder pipe. A copper thermocouple will be used as the temperature sensor to monitor the moderator temperature inside the cryostat holder. Initial measurements of neutron spectrum after neutron passing through the moderating materials have been carried out using a neutron spectrometer.

  15. The new Cold Neutron Chopper Spectrometer at the Spallation Neutron Source -- Design and Performance

    SciTech Connect

    Ehlers, Georg; Podlesnyak, Andrey A.; Niedziela, Jennifer L.; Iverson, Erik B.; Sokol, Paul E.

    2011-01-01

    The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

  16. The new cold neutron chopper spectrometer at the Spallation Neutron Source: Design and performance

    SciTech Connect

    Ehlers, G.; Podlesnyak, A. A.; Niedziela, J. L.; Iverson, E. B.; Sokol, P. E.

    2011-08-15

    The design and performance of the new cold neutron chopper spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge are described. CNCS is a direct-geometry inelastic time-of-flight spectrometer, designed essentially to cover the same energy and momentum transfer ranges as IN5 at ILL, LET at ISIS, DCS at NIST, TOFTOF at FRM-II, AMATERAS at J-PARC, PHAROS at LANSCE, and NEAT at HZB, at similar energy resolution. Measured values of key figures such as neutron flux at sample position and energy resolution are compared between measurements and ray tracing Monte Carlo simulations, and good agreement (better than 20% of absolute numbers) has been achieved. The instrument performs very well in the cold and thermal neutron energy ranges, and promises to become a workhorse for the neutron scattering community for quasielastic and inelastic scattering experiments.

  17. First operation experience with the cryogenic moderator at the SINQ Spallation Neutron Source

    SciTech Connect

    Spitzer, Harald; Bauer, Guenter S.; Hofmann, Thomas

    1997-09-01

    SINQ first reached its full power of 0.9 mA of proton beam at 570 MeV on Dec. 4, 1996. Since then the whole system, including the cold moderator has been running reliably and predictably. The present paper reports on data measured during cool down, stationary operation and warm up of the system. Thermal data measured show that the cryogenic properties of the system are better than the anticipated values. The cold neutron intensity at the guide system is as expected, but the spectrum seems to be shifted to somewhat longer wavelengths than predicted by Monte Carlo calculations, indicating a more complicated spectral distribution than what can be described by a single or even a sum of two Maxwellian distributions. (auth)

  18. The neutron moderated detector and groundbased cosmic ray modulation studies

    NASA Technical Reports Server (NTRS)

    Stoker, P. H.; Raubenheimer, B. C.

    1985-01-01

    Reports appear on modulation studies with the neutron monitor without lead. Some of these studies cast doubt on the reliability of this detector. The stability of the neutron moderated detector (NMD) at Sanae, Antarctic is discussed. The barometric coeficient of the 4NMD for epoch 1976 appears not to differ statistically from the 0.73%/mb of the 3NM64. The monthly averaged hourly counting rate of our 4NMD and 3NM64 correlates very well (correlation coefficient: 98%) over the years from 1974-1984, with the 4NMD showing a 8% larger long term modulation effect than the 3NM64, indicating a difference in sensitivities of the two detectors. From this difference in sensitivities spectra of ground level solar proton events and modulation functions of Forbush decreases are deduced.

  19. An ultra-cold neutron source at the MLNSC

    SciTech Connect

    Bowles, T.J.; Brun, T.; Hill, R.; Morris, C.; Seestrom, S.J.; Crow, L.; Serebrov, A.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have carried out the research and development of an Ultra-Cold Neutron (UCN) source at the Manuel Lujan Neutron Scattering Center (MLNSC). A first generation source was constructed to test the feasibility of a rotor source. The source performed well with an UCN production rate reasonably consistent with that expected. This source can now provide the basis for further development work directed at using UCN in fundamental physics research as well as possible applications in materials science.

  20. Simulation of Cold Neutron Experiments using GEANT4

    NASA Astrophysics Data System (ADS)

    Frlez, Emil; Hall, Joshua; Root, Melinda; Baessler, Stefan; Pocanic, Dinko

    2013-10-01

    We review the available GEANT4 physics processes for the cold neutrons in the energy range 1-100 meV. We consider the cases of the neutron beam interacting with (i) para- and ortho- polarized liquid hydrogen, (ii) Aluminum, and (iii) carbon tetrachloride (CCl4) targets. Scattering, thermal and absorption cross sections used by GEANT4 and MCNP6 libraries are compared with the National Nuclear Data Center (NNDC) compilation. NPDGamma detector simulation is presented as an example of the implementation of the resulting GEANT4 code. This work is supported by NSF grant PHY-0970013.

  1. Deuterated polyethylene coatings for ultra-cold neutron applications

    SciTech Connect

    Brenner, Th.; Geltenbort, P.; Fierlinger, P.; Gutsmiedl, E.; Hollering, A.; Petzoldt, G.; Ruhstorfer, D.; Stuiber, St.; Taubenheim, B.; Windmayer, D.; Lauer, T.; Schroffenegger, J.; Zechlau, T.; Seemann, K. M.; Soltwedel, O.

    2015-09-21

    We report on the fabrication and use of deuterated polyethylene as a coating material for ultra-cold neutron (UCN) storage and transport. The Fermi potential has been determined to be 214 neV, and the wall loss coefficient η is 1.3 × 10{sup 4} per wall collision. The coating technique allows for a wide range of applications in this field of physics. In particular, flexible and quasi-massless UCN guides with slit-less shutters and seamless UCN storage volumes become possible. These properties enable the use in next-generation measurements of the electric dipole moment of the neutron.

  2. Plans for an Ultra Cold Neutron source at Los Alamos

    SciTech Connect

    Seestrom, S.J.; Bowles, T.J.; Hill, R.; Greene, G.L.

    1996-10-01

    Ultra Cold Neutrons (UCN) can be produced at spallation sources using a variety of techniques. To date the technique used has been to Bragg scatter and Doppler shift cold neutrons into UCN from a moving crystal. This is particularly applicable to short-pulse spallation sources. We are presently constructing a UCN source at LANSCE using this method. In addition, large gains in UCN density should be possible using cryogenic UCN sources. Research is under way at Gatchina to demonstrate technical feasibility of a frozen deuterium source. If successful, a source of this type could be implemented at future spallation source, such as the long pulse source being planned at Los Alamos, with a UCN density that may be two orders of magnitude higher than that presently available at reactors.

  3. Development of an ultra cold neutron source at MLNSC

    SciTech Connect

    Seestrom, S.J.; Bowles, T.J.; Hill, R.; Greene, G.L.; Morris, C.L.

    1996-09-01

    Ultra Cold Neutrons (UCN) can be produced at spallation sources using a variety of techniques. To date the technique used has been to Bragg scatter and Doppler shift cold neutrons into UCN from a moving crystal. This is particularly applicable to short-pulse spallation sources. We are presently constructing a UCN source at LANSCE using this method. In addition, large gains in UCN density should be possible using cryogenic UCN sources. Research is under way at Gatchina to demonstrate technical feasibility of a frozen deuterium source. If successful, a source of this type could be implemented at future spallation sources, such as the long pulse source being planned at Los Alamos, with a UCN density that may be two orders of magnitude higher than that presently available at reactors.

  4. "Influence Method" applied to measure a moderated neutron flux

    NASA Astrophysics Data System (ADS)

    Rios, I. J.; Mayer, R. E.

    2016-01-01

    The "Influence Method" is conceived for the absolute determination of a nuclear particle flux in the absence of known detector efficiency. This method exploits the influence of the presence of one detector, in the count rate of another detector when they are placed one behind the other and define statistical estimators for the absolute number of incident particles and for the efficiency. The method and its detailed mathematical description were recently published (Rios and Mayer, 2015 [1]). In this article we apply it to the measurement of the moderated neutron flux produced by an 241AmBe neutron source surrounded by a light water sphere, employing a pair of 3He detectors. For this purpose, the method is extended for its application where particles arriving at the detector obey a Poisson distribution and also, for the case when efficiency is not constant over the energy spectrum of interest. Experimental distributions and derived parameters are compared with theoretical predictions of the method and implications concerning the potential application to the absolute calibration of neutron sources are considered.

  5. Study of neutron focusing at the Texas Cold Neutron Source. Final report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1995-03-06

    Funds were received for the first year of a three year DOE Nuclear Engineering Research Grant, ``Study of Neutron Focusing at the Texas Cold Neutron Source`` (FGO2-92ER75711). The purpose of this three year study was to develop a neutron focusing system to be used with the Texas Cold Neutron Source (TCNS) to produce an intense beam of neutrons. A prompt gamma activation analysis (PGAA) facility was also to be designed, setup, and tested under the three year project. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which we wrote to trace neutrons through the curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, we obtained gains of 3 to 5 for the neutron flux averaged over an area of 1 {times} 1 cm.

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

    NASA Technical Reports Server (NTRS)

    Stoker, P. H.

    1985-01-01

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

  7. Preliminary ANS (Advanced Neutron Source) reactor cold source gain factor calculations for liquid deuterium and liquid nitrogen-15

    SciTech Connect

    Henderson, D.L.

    1988-11-01

    Individual energy group gain factors are computed for liquid nitrogen-15 and liquid deuterium cold source moderators using simple one-dimensional slab and spherical geometry calculational models. The energy spectrum of the neutron source is assumed to be that of a thermalized Maxwellian flux at 20/degree/C. The slab geometry calculations indicate that the optimum thickness for neutron transmission through a slab given an isotropic incident flux is for wavelengths above .6 nm, approximately .20 m for liquid deuterium and between .28 and .32 m for liquid nitrogen-15. The gain factors at .8 nm corresponding to these thicknesses are 15.5 for liquid deuterium and 3.50 for liquid nitrogen-15. The spherical geometry analysis showed that the cold neutron current below 10 MeV of 1.36 n/m/sup 2/-s for the neutron component entering the cavity of a .16 m thick liquid deuterium spherical shell exceeds the neutron leakage current of 1.08 n/cm/sup 2/-s from a .38 m diameter liquid deuterium solid sphere. However, the cold neutron factors for the neutron entering the void region are considerably lower than for the solid sphere case. 15 refs., 24 figs., 7 tabs.

  8. On the measurement the neutron lifetime using ultra-cold neutrons in a vacuum quadrupole trap

    SciTech Connect

    Bowman, J. D.; Penttila, S. I.

    2004-01-01

    We present a conceptual design for an experiment to measure the neutron lifetime ({approx}882 s) with an accuracy of 10{sup -4}. The lifetime will be measured by observing the decay rate of a sample of UCNs confined in vacuum in a magnetic trap. The UCN collaboration at LANL has developed a prototype ultra-cold neutron UCN source that is expected to produce a bottled UCN density of more than 100 UCN/cm{sup 3}. The availability of such an intense source makes it possible to approach the measurement of the neutron lifetime in a new way. We argue below that it is possible to measure the neutron lifetime to 10{sup -4} in a vacuum magnetic trap. The measurement involves no new technology beyond the expected UCN density. If even higher densities are available, the experiment can be made better and/or less expensive. We present the design and methodology for the measurement. The slow loss of neutrons that have stable orbits, but are not energetically trapped would produce a systematic error in the measurement. We discuss a new approach, chaotic cleaning, to the elimination of quasi-neutrons from the trap by breaking the rotational symmetry of the quadrupole trap. The neutron orbits take on a chaotic character and mode mixing causes the neutrons on the quasi-bound orbits to leave the trap.

  9. 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

  10. Exact ultra cold neutrons' energy spectrum in gravitational quantum mechanics

    NASA Astrophysics Data System (ADS)

    Pedram, Pouria

    2013-10-01

    We find exact energy eigenvalues and eigenfunctions of the quantum bouncer in the presence of the minimal length uncertainty and the maximal momentum. This form of Generalized (Gravitational) Uncertainty Principle (GUP) agrees with various theories of quantum gravity and predicts a minimal length uncertainty proportional to and a maximal momentum proportional to , where β is the deformation parameter. We also find the semiclassical energy spectrum and discuss the effects of this GUP on the transition rate of the ultra cold neutrons in gravitational spectrometers. Then, based on Nesvizhevsky's famous experiment, we obtain an upper bound on the dimensionless GUP parameter.

  11. Numerical simulation of self-regulating characteristics of a cold neutron source with a closed-thermosiphon

    NASA Astrophysics Data System (ADS)

    Kawai, Takeshi; Utsuro, Masahiko; Okamoto, Sunao

    1989-12-01

    A cold neutron source (CNS) having a closed-thermosiphon cooling loop shows a self-regulating characteristic regarding the heat load fluctuations if the moderator transfer tube fulfills certain conditions. A dynamic equation for the closed-thermosiphon type CNS having such a property has been presented on the basis of the non-equilibrium thermodynamics. Kyoto University Reactor (KUR) CNS was investigated by numerical simulation of this equation. The numerical predictions are in agreement with an experimental Bode diagram.

  12. Surface physics with cold and thermal neutron reflectometry

    NASA Astrophysics Data System (ADS)

    Steyerl, A.

    1991-11-01

    Three aspects of the research project were stressed during the present first year: (1) Setup of the reflectometer facility at the research reactor of the Rhode Island Nuclear Science Center. The installation provides a narrow 'pencil beam' analyzed by time of flight using a chopper system. Following beam characterization and a test measurement of the total cross section of copper single crystal first reflectivity measurements are currently performed using a supermirror. (2) Design study for the ultracold neutron imaging system, with involvement of the relevant industry. Bids are available for several components indicating that it will be very difficult to build the entire system unless further funds become available. (3) Analysis of features of neutron reflection from surfaces with special emphasis on the effect of surface roughness both on the specular beam and the diffusely reflected and refracted intensity. Previous theoretical studies were supplemented by further numerical calculations of diffuse scattering distributions using different models. Application of ultracold and cold neutron reflectometry to the study of liquid-vapor phase transition were discussed. The theoretical work also includes the development of tentative ideas for novel fundamental physics experiments.

  13. A feasibility design study on a neutron spectrometer for BNCT with liquid moderator.

    PubMed

    Tamaki, S; Sato, F; Murata, I

    2015-12-01

    Neutrons generated by accelerators have various energy spectra. However, only limited methods are available to measure the whole neutron energy spectrum, especially when including the epithermal region that is normally used in BNCT. In the present study, we carried out the design study on a new neutron spectrometer that can measure such a neutron spectrum more accurately, precisely and with higher energy resolution, using an unfolding technique and a liquid moderator.

  14. Interaction of very cold neutrons with a polystyrene-polybutadiene-polystyrene block copolymer

    SciTech Connect

    Antonov, A.V.; Gerasimov, V.I.; Isakov, A.I.; Kuznetsov, S.P.; Meshkov, I.V.; Perekrestenko, A.D.; Tarasov, S.G.

    1985-03-10

    The total interaction cross sections have been studied as a function of the wavelength of very cold neutrons (summation/sub t/(lambda)) in a very-cold-neutron spectrometer (A. V. Antonov et al., Kratk. Soobshch. Fiz. 10, 10 (1977)) with a polystyrene-polybutadiene-polystyrene block copolymer at room temperature and at 99 K.

  15. Study of neutron focusing at the Texas Cold Neutron Source: Progress report

    SciTech Connect

    Wehring, B.W.; Uenlue, K.

    1993-01-28

    The purpose of this three year study is to develop a neutron focusing system to be used with the Texas Cold Neutron Source (TCNS) to produce an intense beam of neutrons. A prompt gamma activation analysis (PGAA) facility will also be designed, setup, and tested under this DOE grant. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which the authors wrote to trace neutrons through the existing curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, they obtained gains of 4 to 5 for the neutron flux averaged over an area of 1 x 1 cm. Two graduate students were supported by the first year of the DOE grant. Both have passed the Nuclear Engineering qualifying examination and have been admitted to candidacy for the doctoral degree at The University of Texas at Austin. Their programs of study and dissertation projects have been approved by the appropriate committees.

  16. Neutron production and time resolution of a new class moderator for pulsed neutron diffraction. Measurements and transport calculations

    NASA Astrophysics Data System (ADS)

    Mayer, R. E.; Florido, P. C.; Granada, J. R.; Dawidowski, J.; Gillette, V. H.

    1992-06-01

    Measurements of neutron pulse time-width and intensity have been carried out on grids of small moderators placed side by side and decoupled by cadium strips; a moderator concept introduced by the authors through previous publications. Transport calculations are based on the standard reactor code DOT 3.5 with the ENDF-B IV nuclear data library.

  17. Optimizing moderation of He-3 neutron detectors for shielded fission sources

    DOE PAGES

    Rees, Lawrence B.; Czirr, J. Bart

    2012-07-10

    Abstract: The response of 3-He neutron detectors is highly dependent on the amount of moderator incorporated into the detector system. If there is too little moderation, neutrons will not react with the 3-He. If there is too much moderation, neutrons will not reach the 3-He. In applications for portal or border monitors where 3He detectors are used to interdict illicit Importation of plutonium, the fission source is always shielded to some extent. Since the energy distribution of neutrons emitted from the source depends on the amount and type of shielding present, the optimum placement of moderating material around 3-He tubesmore » is a function of shielding. In this paper, we use Monte Carlo techniques to model the response of 3-He tubes placed in polyethylene boxes for moderation. To model the shielded fission neutron source, we use a 252-Cf source placed in the center of spheres of water of varying radius. Detector efficiency as a function of box geometry and shielding are explored. We find that increasing the amount of moderator behind and to the sides of the detector generally improves the detector response, but that benefits are limited if the thickness of the polyethylene moderator is greater than about 5-7 cm. The thickness of the moderator in front of the 3He tubes, however, is very important. For bare sources, about 5-6 cm of moderator is optimum, but as the shielding increases, the optimum thickness of this moderator decreases to 0-1 cm. A two-tube box with a moderator thickness of 5 cm in front of the first tube and a thickness of 1 cm in front of the second tube is proposed to improve the detector's sensitivity to lower-energy neutrons.« less

  18. From the similarities between neutrons and radon to advanced radon-detection and improved cold fusion neutron-measurements

    NASA Astrophysics Data System (ADS)

    Tommasino, L.; Espinosa, G.

    2014-07-01

    Neutrons and radon are both ubiquitous in the earth's crust. The neutrons of terrestrial origin are strongly related to radon since they originate mainly from the interactions between the alpha particles from the decays of radioactive-gas (namely Radon and Thoron) and the light nuclei. Since the early studies in the field of neutrons, the radon gas was used to produce neutrons by (α, n) reactions in beryllium. Another important similarity between radon and neutrons is that they can be detected only through the radiations produced respectively by decays or by nuclear reactions. These charged particles from the two distinct nuclear processes are often the same (namely alpha-particles). A typical neutron detector is based on a radiator facing a alpha-particle detector, such as in the case of a neutron film badge. Based on the similarity between neutrons and radon, a film badge for radon has been recently proposed. The radon film badge, in addition to be similar, may be even identical to the neutron film badge. For these reasons, neutron measurements can be easily affected by the presence of unpredictable large radon concentration. In several cold fusion experiments, the CR-39 plastic films (typically used in radon and neutron film-badges), have been the detectors of choice for measuring neutrons. In this paper, attempts will be made to prove that most of these neutron-measurements might have been affected by the presence of large radon concentrations.

  19. Cold neutron prompt gamma-ray activation analysis at NIST - an overview

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.

    1994-12-31

    An instrument for cold neutron capture prompt gamma-ray activation analysis (CNPGAA), located in the cold neutron research facility (CNRF) at the National Institute of Standards and Technology (NIST) has proven useful for the analysis of hydrogen and other elements in a wide variety of materials. The intent of this paper is to provide an overview of the instrument, focusing on recent improvements and the impact of these improvement on measurements.

  20. Effect of the Temperature of the Moderator on the Velocity Distribution of Neutrons with Numerical Calculations for H as Moderator

    DOE R&D Accomplishments Database

    Wigner, E. P.; Wilkins, J. E. Jr.

    1944-09-14

    In this paper we set up an integral equation governing the energy distribution of neutrons that are being slowed down uniformly throughout the entire space by a uniformly distributed moderator whose atoms are in motion with a Maxwellian distribution of velocities. The effects of chemical binding and crystal reflection are ignored. When the moderator is hydrogen, the integral equation is reduced to a differential equation and solved by numerical methods. In this manner we obtain a refinement of the dv/v{sup 2} law. (auth)

  1. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station.

    PubMed

    Gallmeier, F X; Lu, W; Riemer, B W; Zhao, J K; Herwig, K W; Robertson, J L

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm(2) to 20 × 20 mm(2). This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator. PMID:27370444

  2. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station.

    PubMed

    Gallmeier, F X; Lu, W; Riemer, B W; Zhao, J K; Herwig, K W; Robertson, J L

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm(2) to 20 × 20 mm(2). This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  3. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    NASA Astrophysics Data System (ADS)

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

    2016-06-01

    Candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) have been identified using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared to the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. This increase in brightness has the potential to translate to an increase of beam intensity at the instruments' sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. A first effort was undertaken to group decoupled moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.

  4. Conceptual moderator studies for the Spallation Neutron Source short-pulse second target station

    DOE PAGES

    Gallmeier, F. X.; Lu, W.; Riemer, B. W.; Zhao, J. K.; Herwig, K. W.; Robertson, J. L.

    2016-06-14

    We identified candidate moderator configurations for a short-pulse second target station (STS) at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) using a global optimizer framework built around the MCNPX particle transport code. Neutron brightness metrics were selected as the figure-of-merit. We assumed that STS would use one out of six proton pulses produced by an SNS accelerator upgraded to operate at 1.3 GeV proton energy, 2.8 MW power and 60 Hz repetition rate. The simulations indicate that the peak brightness can be increased by a factor of 5 and 2.5 on a per proton pulse basis compared tomore » the SNS first target station for both coupled and decoupled para-hydrogen moderators, respectively. Additional increases by factors of 3 and 2 were demonstrated for coupled and decoupled moderators, respectively, by reducing the area of neutron emission from 100 × 100 mm2 to 20 × 20 mm2. Furthermore, this increase in brightness has the potential to translate to an increase of beam intensity at the instruments’ sample positions even though the total neutron emission of the smaller moderator is less than that of the larger. This is especially true for instruments with small samples (beam dimensions). The increased fluxes in the STS moderators come at accelerated poison and de-coupler burnout and higher radiation-induced material damage rates per unit power, which overall translate into lower moderator lifetimes. Our first effort decoupled group moderators into a cluster collectively positioning them at the peak neutron production zone in the target and having a three-port neutron emission scheme that complements that of a cylindrical coupled moderator.« less

  5. The use of chopper spectrometers for cold-to-epithermal neutron scattering at IPNS

    SciTech Connect

    Loong, C.K.; Donley, L.I.; Ostrowski, G.E.; Kleb, R.; Hammonds, J.P.; Soderholm, L.; Takahashi, S.

    1993-09-01

    A multi-detector chopper spectrometer enables measurements of the scattering function S(Q,E) to be made over a wide range of momentum and energy transfer (Q,E). The application of pulsed-source chopper spectrometers for inelastic measurements at thermal and epithermal energies (50 meV < E < 1000 meV) is well known. Recently at IPNS, we have extended the energy-transfer region down to about 0.5 meV with a resolution of the order of 150 {mu}eV. It is made possible by utilizing the cold-neutron incident spectrum of the 100 K methane moderator in conjunction with a dual beryllium-body rotor system. Neutron incident energies can be changed efficiently over the 4 to 1000 meV region while maintaining an undisturbed sample environment. We describe the operation of the IPNS chopper spectrometers (HRMECS and LRMECS), the instrumental resolution and the background-suppression performance. The capability of measuring inelastic features from 0.5 to 100 meV with an energy resolution of {Delta}E/E{sub 0} = 2.5% is demonstrated by experimental results of crystal-field excitation spectra of a high-Tc superconductor ErBa{sub 2}Cu{sub 3}O{sub 7}. Preliminary data of quasielastic scattering from a room-temperature molten salt AlCl{sub 3}-EMIC are presented.

  6. Precision Measurement of Parity Violation in Polarized Cold Neutron Capture on the Proton: the NPDGamma Experiment

    SciTech Connect

    Bernhard Lauss; J.D. Bowman; R. Carlini; T.E. Chupp; W. Chen; S. Corvig; M. Dabaghyan; D. Desai; S.J. Freeman; T.R. Gentile; M.T. Gericke; R.C. Gillis; G.L. Greene; F.W. Hersman; T. Ino; T. Ito; G.L. Jones; M. Kandes; M. Leuschner; B. Lozowski; R. Mahurin; M. Mason; Y. Masuda; J. Mei; G.S. Mitchell; S. Muto; H. Nann; S.A. Page; S.I. Penttila; W.D. Ramsay; S. Santra; P.-N. Seo; E.I. Sharapov; T.B. Smith; W.M. Snow; W.S. Wilburn; V. Yuan; H. Zhu

    2005-10-24

    The NPD{gamma} experiment at the Los Alamos Neutron Science Center (LANSCE) is dedicated to measure with high precision the parity violating asymmetry in the {gamma} emission after capture of spin polarized cold neutrons in para-hydrogen. The measurement will determine unambiguously the weak pion-nucleon-nucleon ({pi} NN) coupling constant (line integral){sub {pi}}{sup l}.

  7. Thermal-Hydraulic Mockup Tests with Two-Phase Thermosyphon for Cold Neutron Source

    SciTech Connect

    Lee, C.H.; Chan, Y.K.; Lee, D.J.; Chang, C.J.; Hong, W.T.

    2002-07-01

    The improvement and utilization promotion project of the Taiwan Research Reactor (TRR-II) is carrying out at the Institute of Nuclear Energy Research (INER). The Cold Neutron Source (CNS) with a two-phase thermosyphon will be installed in the heavy water reactor of TRR-II. The hydrogen cold loop of TRR-II CNS consists of a cylindrical moderator cell, a single transfer tube, and a condenser. The thermal-hydraulic characteristics of a two-phase thermosyphon are investigated against the variations of mass inventory, tube geometry and heat loads. The thermal-hydraulic experiments have been performed using a full-scale mockup loop and a Freon-11 as a working fluid. The scaling approach is that the mass-fluxes of the liquid and the vapor in the Wallis correlation are identical between hydrogen and Freon-11. So, the same density ratio and a scaling heat load are applied to the loop. The flooding limitations as a function of initial Freon-11 inventory, transfer tube diameter, transfer tube geometry, and heat loads are presented. (authors)

  8. Characteristics of the simulated workplace neutron fields using a 252Cf source surrounded with cylindrical moderators.

    PubMed

    Tsujimura, N; Yoshida, T

    2004-01-01

    The authors established the simulated workplace neutron fields using a 252Cf source surrounded with cylindrical moderators at the Japan Nuclear Cycle Development Institute (JNC), Tokai Works. The moderators are annular cylinders made of polymethyl methacrylate and steel. The neutron energy spectrum at the reference calibration point was evaluated from the calculations by MCNP-4B and the measurements by the Bonner multisphere spectrometer and the hydrogen-filled proportional counters. The calculated neutron spectra were in good agreements with the measured ones. These fields can provide the realistic neutron spectra similar to those encountered around the glove-boxes of the fabrication process of MOX (PuO2-UO2 mixed oxide) fuel.

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

    SciTech Connect

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

    2000-07-01

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

  10. Coded moderator approach for fast neutron source detection and localization at standoff

    NASA Astrophysics Data System (ADS)

    Littell, Jennifer; Lukosi, Eric; Hayward, Jason; Milburn, Robert; Rowan, Allen

    2015-06-01

    Considering the need for directional sensing at standoff for some security applications and scenarios where a neutron source may be shielded by high Z material that nearly eliminates the source gamma flux, this work focuses on investigating the feasibility of using thermal neutron sensitive boron straw detectors for fast neutron source detection and localization. We utilized MCNPX simulations to demonstrate that, through surrounding the boron straw detectors by a HDPE coded moderator, a source-detector orientation-specific response enables potential 1D source localization in a high neutron detection efficiency design. An initial test algorithm has been developed in order to confirm the viability of this detector system's localization capabilities which resulted in identification of a 1 MeV neutron source with a strength equivalent to 8 kg WGPu at 50 m standoff within ±11°.

  11. A Monte Carlo simulation of monoenergetic neutrons traversing rectangular and spherical polyethylene moderators.

    PubMed

    Monk, S D; Selwood, M

    2011-03-01

    A Monte Carlo-based simulation of the transport of a series of monoenergetic neutron sources through first a rectangular block of 0.93 g cm(-3) density polyethylene and secondly through a sphere made of the same substance is presented here. In both instances, the neutron fields are monitored at closely spread intervals through the moderator mass, producing a lot of data in the process. To reduce the amount of data presented, a figure of merit is created by estimating the cross section for each discrete neutron energy and by applying this to the number of neutrons present of each energy giving an arbitrary response figure. This work was undertaken in order to aid the design and development of a novel neutron spectrometer.

  12. Hypertension Does Not Alter the Increase in Cardiac Baroreflex Sensitivity Caused by Moderate Cold Exposure

    PubMed Central

    Hintsala, Heidi E.; Kiviniemi, Antti M.; Tulppo, Mikko P.; Helakari, Heta; Rintamäki, Hannu; Mäntysaari, Matti; Herzig, Karl-Heinz; Keinänen-Kiukaanniemi, Sirkka; Jaakkola, Jouni J. K.; Ikäheimo, Tiina M.

    2016-01-01

    Exposure to cold increases blood pressure and may contribute to higher wintertime cardiovascular morbidity and mortality in hypertensive people, but the mechanisms are not well-established. While hypertension does not alter responses of vagally-mediated heart rate variability to cold, it is not known how hypertension modifies baroreflex sensitivity (BRS) and blood pressure variability during cold exposure. Our study assessed this among untreated hypertensive men during short-term exposure comparable to habitual winter time circumstances in subarctic areas. We conducted a population-based recruitment of 24 untreated hypertensive and 17 men without hypertension (age 55–65 years) who underwent a whole-body cold exposure (−10°C, wind 3 m/s, winter clothes, 15 min, standing). Electrocardiogram and continuous blood pressure were measured to compute spectral powers of systolic blood pressure and heart rate variability at low (0.04–0.15 Hz) and high frequency (0.15–0.4 Hz) and spontaneous BRS at low frequency (LF). Comparable increases in BRS were detected in hypertensive men, from 2.6 (2.0, 4.2) to 3.8 (2.5, 5.1) ms/mmHg [median (interquartile range)], and in control group, from 4.3 (2.7, 5.0) to 4.4 (3.1, 7.1) ms/mmHg. Instead, larger increase (p < 0.05) in LF blood pressure variability was observed in control group; response as median (interquartile range): 8 (2, 14) mmHg2, compared with hypertensive group [0 (−13, 20) mmHg2]. Untreated hypertension does not disturb cardiovascular protective mechanisms during moderate cold exposure commonly occurring in everyday life. Blunted response of the estimate of peripheral sympathetic modulation may indicate higher tonic sympathetic activity and decreased sympathetic responsiveness to cold in hypertension. PMID:27313543

  13. Hypertension Does Not Alter the Increase in Cardiac Baroreflex Sensitivity Caused by Moderate Cold Exposure.

    PubMed

    Hintsala, Heidi E; Kiviniemi, Antti M; Tulppo, Mikko P; Helakari, Heta; Rintamäki, Hannu; Mäntysaari, Matti; Herzig, Karl-Heinz; Keinänen-Kiukaanniemi, Sirkka; Jaakkola, Jouni J K; Ikäheimo, Tiina M

    2016-01-01

    Exposure to cold increases blood pressure and may contribute to higher wintertime cardiovascular morbidity and mortality in hypertensive people, but the mechanisms are not well-established. While hypertension does not alter responses of vagally-mediated heart rate variability to cold, it is not known how hypertension modifies baroreflex sensitivity (BRS) and blood pressure variability during cold exposure. Our study assessed this among untreated hypertensive men during short-term exposure comparable to habitual winter time circumstances in subarctic areas. We conducted a population-based recruitment of 24 untreated hypertensive and 17 men without hypertension (age 55-65 years) who underwent a whole-body cold exposure (-10°C, wind 3 m/s, winter clothes, 15 min, standing). Electrocardiogram and continuous blood pressure were measured to compute spectral powers of systolic blood pressure and heart rate variability at low (0.04-0.15 Hz) and high frequency (0.15-0.4 Hz) and spontaneous BRS at low frequency (LF). Comparable increases in BRS were detected in hypertensive men, from 2.6 (2.0, 4.2) to 3.8 (2.5, 5.1) ms/mmHg [median (interquartile range)], and in control group, from 4.3 (2.7, 5.0) to 4.4 (3.1, 7.1) ms/mmHg. Instead, larger increase (p < 0.05) in LF blood pressure variability was observed in control group; response as median (interquartile range): 8 (2, 14) mmHg(2), compared with hypertensive group [0 (-13, 20) mmHg(2)]. Untreated hypertension does not disturb cardiovascular protective mechanisms during moderate cold exposure commonly occurring in everyday life. Blunted response of the estimate of peripheral sympathetic modulation may indicate higher tonic sympathetic activity and decreased sympathetic responsiveness to cold in hypertension. PMID:27313543

  14. Design of the cold neutron triple-axis spectrometer at the China Advanced Research Reactor

    NASA Astrophysics Data System (ADS)

    Cheng, P.; Zhang, Hongxia; Bao, W.; Schneidewind, A.; Link, P.; Grünwald, A. T. D.; Georgii, R.; Hao, L. J.; Liu, Y. T.

    2016-06-01

    The design of the first cold neutron triple-axis spectrometer at the China Advanced Research Reactor is presented. Based on the Monte Carlo simulations using neutron ray-tracing program McStas, the parameters of major neutron optics in this instrument are optimized. The neutron flux at sample position is estimated to be 5.6 ×107 n/cm2/s at neutron incident energy Ei=5 meV when the reactor operates normally at the designed 60 MW power. The performances of several neutron supermirror polarizing devices are compared and their critical parameters are optimized for this spectrometer. The polarization analysis will be realized with a flexible switch from the unpolarized experimental mode.

  15. Performance of beam bender for very cold neutrons

    NASA Astrophysics Data System (ADS)

    Kawabata, Yuji; Utsuro, Masahiko; Ebisawa, Tohru

    1992-11-01

    A VCN bender has been installed behind the VCN guide tube in the UCN-VCN facility of KUR. The design and the performance of the VCN bender is described in this paper. The neutron spectra at the end of the VCN bender has been measured by the reflection method using a multilayer monochromator. Neutron radiography films were used to know the neutron flux distribution. The VCN gain factor of the CNS is also derived from the spectrum measurements at the end of the VCN guide tube and the VCN bender.

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

    PubMed

    Rivard, Mark J; Zamenhof, Robert G

    2004-11-01

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

  17. Excitations of one-valence-proton, one-valence-neutron nucleus {sup 210}Bi from cold-neutron capture

    SciTech Connect

    Cieplicka-Oryńczak, N.; Fornal, B.; Szpak, B.; Leoni, S.; Bottoni, S.; Bazzacco, D.; Blanc, A.; Jentschel, M.; Köster, U.; Mutti, P.; Soldner, T.; Bocchi, G.; France, G. de; Simpson, G.; Urban, W.

    2015-10-15

    The low-spin structure of one-proton, one-neutron {sup 210}Bi nucleus was investigated in cold-neutron capture reaction on {sup 209}Bi. The γ-coincidence measurements were performed with use of EXILL array consisted of 16 HPGe detectors. The experimental results were compared to shell-model calculations involving valence particles excitations. The {sup 210}Bi nucleus offers the potential to test the effective proton-neutron interactions because most of the states should arise from the proton-neutron excitations. Additionally, it was discovered that a few states should come from the couplings of valence particles to the 3{sup −} octupole vibration in {sup 208}Pb which provides also the possibility of testing the calculations involving the core excitations.

  18. Instrument resolution of the vertical-type cold-neutron reflectometer at HANARO

    NASA Astrophysics Data System (ADS)

    Lee, Jeong Soo

    2016-05-01

    The characteristics of the instrument resolution of the vertical-type cold-neutron reflectometer installed at HANARO, a research reactor in Korea, are estimated. In order to ascertain differences in the instrument resolution according to two scan modes, i.e., the fixed-slit and the variable-slit scan modes, for the measurement of the neutron reflectivity profile, we estimated the beam status of the instrument. Moreover, because the footprint effect and the limitation of the neutron beam window arise during measurements of the neutron reflectivity profiles and affect the instrument resolution, the causes of their occurrence were determined and a correction method was devised. The neutron reflectivity profiles of a SiO2 standard thin-film sample were measured in a Q range up to 0.2 Å-1 by using the two scan modes, and the sample structure was analyzed with the weighted least-squares fitting program Parratt32. During the process of the least-squares fitting of the neutron reflectivity profiles for the structural analysis, the method used to correct for the footprint effect and the limitation of neutron beam window was found to be reasonable. Also, the modified instrument resolutions in the two scan modes for the vertical-type cold-neutron reflectometer were found to be suitable.

  19. Endocrine-metabolic responses to military field operations: Effects of cold and moderate altitude exposure

    SciTech Connect

    Floyd, E.; Hackney, A.C.; Hodgdon, J.A.; Coyne, J.T.; Kelleher, D.L. Univ. of North Carolina, Chapel Hill )

    1991-03-11

    Select endocrine-metabolic responses of US Marines to 4.5 day field operations (FOPS) in different environments were examined. Blood and urine samples were collected in the field immediately before and after FOPS at: (1) sea level, neutral temperatures (Ts) (SLN; n = 14), (2) sea level, cold Ts (SLC; n = 16), (3) 2,500 M altitude, neutral Ts (ALN; n = 16), and (4) 2,500 M altitude, cold Ts (ALC; n = 45). Measures examined were testosterone (T), cortisol (C), glucose (Glu), triglycerides (Tg), and urinary ketones (Uket). T decreased pre-post the FOPS in the cold conditions ({bar X}; 6.7 to 5.5 hg/ml; n = 61) but did not change in neutral conditions. C increased pre-post FOPS at SLC (12.1 to 19.8 ug/dl, p < 0.01), ALN (9.3 to 13.9 ug/dl, p < 0.01), and ALC (16.7 to 19.0 ug/dl, p = 0.08). Normoglycemia was maintained under each condition. Tg decreased (p < 0.01) at SLC, ALN, and ALC ({bar X}{triangle}: {minus}59.1, {minus}102.2, {minus}93.3 mg/dl, respectively), but increased at SLN (+74.0 mg/dl). Uket increased post FOPS only at ALN and ALC ({bar X}{triangle}: 3.4 mg/dl and +11.3 mg/dl). The Uket increases were correlated to Tg decreases. Results suggest FOPS induces a slight endocrine stress response, which is augmented with moderate altitude or cold exposure. Furthermore FOPS at altitude, especially in the cold, seems to shift the body towards fat metabolism.

  20. SIKA—the multiplexing cold-neutron triple-axis spectrometer at ANSTO

    NASA Astrophysics Data System (ADS)

    Wu, C.-M.; Deng, G.; Gardner, J. S.; Vorderwisch, P.; Li, W.-H.; Yano, S.; Peng, J.-C.; Imamovic, E.

    2016-10-01

    SIKA is a new cold-neutron triple-axis spectrometer receiving neutrons from the cold source CG4 of the 20MW Open Pool Australian Light-water reactor. As a state-of-the-art triple-axis spectrometer, SIKA is equipped with a large double-focusing pyrolytic graphite monochromator, a multiblade pyrolytic graphite analyser and a multi-detector system. In this paper, we present the design, functions, and capabilities of SIKA, and discuss commissioning experimental results from powder and single-crystal samples to demonstrate its performance.

  1. Efficiency of Moderated Neutron Lithium Glass Detectors Using Monte Carlo Techniques

    NASA Astrophysics Data System (ADS)

    James, Brian

    2011-10-01

    Due to national security concerns over the smuggling of special nuclear materials and the small supply of He-3 for use in neutron detectors, there is a great need for a new kind of neutron detector. Using Monte Carlo techniques I have been studying the use of lithium glass in varying configurations for neutron detectors. My research has included the effects of using a detector with two thin sheets of lithium at varying distances apart. I have also researched the effects of varying amounts of shielding a californium source with varying amounts of water. This is important since shielding would likely be used to make nuclear material more difficult to detect. The addition of one sheet of lithium-6 glass on the front surface of the detector significantly improves the efficiency for the detection of neutrons from a moderated fission source.

  2. Determination of hydrogen in titanium alloys by cold neutron prompt gamma activation analysis

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.; Greenberg, R.R.; Privett, H.M. III; Richards, W.J.

    1996-11-01

    Cold neutron prompt gamma-ray activation analysis (CNPGAA) has proven useful for the analysis of hydrogen in titanium alloys. The analysis is nondestructive, measures the entire sample, and the results are independent of the chemical form of hydrogen present. The authors have used the technique to measure H mass fractions as low as 50 mg/kg in titanium-alloy jet-engine compressor blades and to measure hydrogen in standards for neutron tomography.

  3. Liquid deuterium cold source in graphite thermal column

    NASA Astrophysics Data System (ADS)

    Utsuro, M.; Kawai, T.; Maeda, Y.; Yamaoka, H.; Akiyoshi, T.; Okamoto, S.

    1989-01-01

    A liquid deuterium cold source with a non-spherical moderator chamber of about 4 litres was installed into the graphite thermal column of 5 MW Kyoto University Reactor (KUR). Three cold neutron holes and one very cold neutron hole are provided in the graphite for beam extractions. The operation tests with hydrogen liquefied in the condenser showed satisfactory performances and high gain factors of cold and very cold neutrons of more than 20 and 10, respectively. Neutron measurements with the deuterium moderator are now in progress.

  4. Evaluation of the characteristics of the neutron reference field using D2O-moderated 252Cf source.

    PubMed

    Kowatari, M; Fujii, K; Takahashi, M; Yoshizawa, M; Shimizu, S; Kawasaki, K; Yamaguchi, Y

    2007-01-01

    The ambient/personal dose equivalent per fluence for D(2)O moderated (252)Cf neutron source was determined by measurement. An appropriate subtraction of the scattered neutrons is required for the accurate measurement of direct neutrons. A cubic shadow object was used for the subtraction of the scattered neutrons from the surroundings. The scattered neutrons to be subtracted vary with the position of the shadow object due to the large volume of the source. Using the Monte Carlo code MCNP-4C, the optimum positions of the shadow object were surveyed for subtracting the scattered neutrons. The energy spectra of direct neutrons were measured in the optimum position. The dosimetric parameters for the D(2)O moderated (252)Cf neutron source were reasonable, taking into account the uncertainties of the parameters.

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

    SciTech Connect

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

    2002-11-01

    The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.

  6. PGAA, PGAI and NT with cold neutrons: test measurement on a meteorite sample.

    PubMed

    Canella, Lea; Kudejová, Petra; Schulze, Ralf; Türler, Andreas; Jolie, Jan

    2009-12-01

    First comprehensive analysis with PGAA, Prompt Gamma-ray Activation Imaging (PGAI) and neutron tomography (NT) techniques at the research reactor FRM II was tested on a piece of the Allende meteorite. With the PGAA method the bulk elemental composition of the heterogeneous meteorite was determined. Due to the small dimension of the sample, only the 2D elemental distribution of the object was derived with position sensitive PGAI analysis. As an example 2D maps for Si, Fe and Mg are presented. Neutron tomography of the meteorite was carried out with the same cold neutron beam.

  7. Demonstration of achromatic cold-neutron microscope utilizing axisymmetric focusing mirrors

    SciTech Connect

    Liu, D.; Khaykovich, B.; Hussey, D.; Jacobson, D.; Arif, M.; Gubarev, M. V.; Ramsey, B. D.; Moncton, D. E.

    2013-05-06

    An achromatic cold-neutron microscope with magnification 4 is demonstrated. The image-forming optics is composed of nested coaxial mirrors of full figures of revolution, so-called Wolter optics. The spatial resolution, field of view, and depth of focus are measured and found consistent with ray-tracing simulations. Methods of increasing the resolution and magnification are discussed, as well as the scientific case for the neutron microscope. In contrast to traditional pinhole-camera neutron imaging, the resolution of the microscope is determined by the mirrors rather than by the collimation of the beam, leading to possible dramatic improvements in the signal rate and resolution.

  8. A New Cold Neutron Imaging Instrument at NIST

    NASA Astrophysics Data System (ADS)

    Hussey, D. S.; Brocker, C.; Cook, J. C.; Jacobson, D. L.; Gentile, T. R.; Chen, W. C.; Baltic, E.; Baxter, D. V.; Doskow, J.; Arif, M.

    The NIST neutron imaging program will build a new imaging instrument in the NCNR guide hall at the end of the neutron guide NG-6, beginning operation in summer of 2015. The NG-6 guide has a spectrum that is strongly peaked at a neutron wavelength of 0.5 nm, with a fluence rate of 2 × 109 cm-2 s-1 before a bismuth filter that is cooled by liquid nitrogen. The instrument will be developed in a phased manner and with an emphasis on maintaining a flexible space to conduct experiments and test new instrument concepts. In the initial phase of the instrument, the available space will permit a flight path of about 9 m, and will provide a platform for standard neutron radiography and tomography, wavelength selective imaging with a double crystal monochromator, and phase imaging based on a Talbot-Lau interferometer. The novel feature of the instrument will be the incorporation of Wolter optics to create a neutron microscope. Initially, prototype optics will be used in the microscope configuration to assess optic characteristics and image acquisition techniques. In the final form, the microscope will enable users to acquire images with ˜10 μm resolution 10-100x faster than current practice, and with a 10x magnifying optic to acquire images with ˜1 μm spatial resolution with image acquisition time similar to that for current images with ˜10 μm resolution.

  9. Benchmark test of neutron transport calculations: indium, nickel, gold, europium, and cobalt activation with and without energy moderated fission neutrons by iron simulating the Hiroshima atomic bomb casing.

    PubMed

    Iwatani, K; Hoshi, M; Shizuma, K; Hiraoka, M; Hayakawa, N; Oka, T; Hasai, H

    1994-10-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated 252Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate 152Eu and 60Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated 252Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen. PMID:8083048

  10. Benchmark test of neutron transport calculations: Indium, nickel, gold, europium, and cobalt activation with and without energy moderated fission neutrons by iron simulating the Hiroshima atomic bomb casing

    SciTech Connect

    Iwatani, Kazuo; Shizuma, Kiyoshi; Hasai, Hiromi; Hoshi, Masaharu; Hiraoka, Masayuki; Hayakawa, Norihiko; Oka, Takamitsu

    1994-10-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated {sup 252}Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate {sup 152}Eu and {sup 60}Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated {sup 252}Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen. 18 refs., 10 figs., 4 tabs.

  11. Benchmark test of neutron transport calculations: indium, nickel, gold, europium, and cobalt activation with and without energy moderated fission neutrons by iron simulating the Hiroshima atomic bomb casing.

    PubMed

    Iwatani, K; Hoshi, M; Shizuma, K; Hiraoka, M; Hayakawa, N; Oka, T; Hasai, H

    1994-10-01

    A benchmark test of the Monte Carlo neutron and photon transport code system (MCNP) was performed using a bare- and energy-moderated 252Cf fission neutron source which was obtained by transmission through 10-cm-thick iron. An iron plate was used to simulate the effect of the Hiroshima atomic bomb casing. This test includes the activation of indium and nickel for fast neutrons and gold, europium, and cobalt for thermal and epithermal neutrons, which were inserted in the moderators. The latter two activations are also to validate 152Eu and 60Co activity data obtained from the atomic bomb-exposed specimens collected at Hiroshima and Nagasaki, Japan. The neutron moderators used were Lucite and Nylon 6 and the total thickness of each moderator was 60 cm or 65 cm. Measured activity data (reaction yield) of the neutron-irradiated detectors in these moderators decreased to about 1/1,000th or 1/10,000th, which corresponds to about 1,500 m ground distance from the hypocenter in Hiroshima. For all of the indium, nickel, and gold activity data, the measured and calculated values agreed within 25%, and the corresponding values for europium and cobalt were within 40%. From this study, the MCNP code was found to be accurate enough for the bare- and energy-moderated 252Cf neutron activation calculations of these elements using moderators containing hydrogen, carbon, nitrogen, and oxygen.

  12. Entrainment parameters in a cold superfluid neutron star core

    SciTech Connect

    Chamel, Nicolas; Haensel, Pawel

    2006-04-15

    Hydrodynamic simulations of neutron star cores that are based on a two-fluid description in terms of a neutron-proton superfluid mixture require the knowledge of the Andreev-Bashkin entrainment matrix which relates the momentum of one constituent to the currents of both constituents. This matrix is derived for arbitrary nuclear asymmetry at zero temperature and in the limits of small relative currents in the framework of the energy density functional theory. The Skyrme energy density functional is considered as a particular case. General analytic formulas for the entrainment parameters and various corresponding effective masses are obtained. These formulas are applied to the liquid core of a neutron star composed of homogeneous plasma of nucleons, electrons, and possibly muons in {beta} equilibrium.

  13. New precision measurements of free neutron beta decay with cold neutrons

    DOE PAGES

    Baeßler, Stefan; Bowman, James David; Penttilä, Seppo I.; Počanić, Dinko

    2014-10-14

    Precision measurements in free neutron beta decay serve to determine the coupling constants of beta decay, and offer several stringent tests of the standard model. This study describes the free neutron beta decay program planned for the Fundamental Physics Beamline at the Spallation Neutron Source at Oak Ridge National Laboratory, and finally puts it into the context of other recent and planned measurements of neutron beta decay observables.

  14. Investigation on the reflector/moderator geometry and its effect on the neutron beam design in BNCT.

    PubMed

    Kasesaz, Y; Rahmani, F; Khalafi, H

    2015-12-01

    In order to provide an appropriate neutron beam for Boron Neutron Capture Therapy (BNCT), a special Beam Shaping Assembly (BSA) must be designed based on the neutron source specifications. A typical BSA includes moderator, reflector, collimator, thermal neutron filter, and gamma filter. In common BSA, the reflector is considered as a layer which covers the sides of the moderator materials. In this paper, new reflector/moderator geometries including multi-layer and hexagonal lattice have been suggested and the effect of them has been investigated by MCNP4C Monte Carlo code. It was found that the proposed configurations have a significant effect to improve the thermal to epithermal neutron flux ratio which is an important neutron beam parameter.

  15. The cold neutron chopper spectrometer at the Spallation Neutron Source—A review of the first 8 years of operation

    DOE PAGES

    Ehlers, G.; Podlesnyak, A. A.; Kolesnikov, A. I.

    2016-09-13

    The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. In addition, experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8more » T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.« less

  16. The cold neutron chopper spectrometer at the Spallation Neutron Source—A review of the first 8 years of operation

    NASA Astrophysics Data System (ADS)

    Ehlers, G.; Podlesnyak, A. A.; Kolesnikov, A. I.

    2016-09-01

    The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T ≲ 0.05 K, p ≳ 2 GPa, and B = 8 T can be achieved individually or in combination. In particular, CNCS is in a position to advance the state of the art with inelastic neutron scattering under pressure, and some of the recent accomplishments in this area will be presented in more detail.

  17. Development of a moderator system for the High Brilliance Neutron Source project

    NASA Astrophysics Data System (ADS)

    Dabruck, J. P.; Cronert, T.; Rücker, U.; Bessler, Y.; Klaus, M.; Lange, C.; Butzek, M.; Hansen, W.; Nabbi, R.; Brückel, T.

    2016-11-01

    The project for an accelerator based high brilliance neutron source HBS driven by Forschungszentrum Jülich forsees the use of the nuclear Be(p,n) or Be(d,n) reaction with accelerated particles in the lower MeV energy range. The lower neutron production compared to spallation has to be compensated by improving the neutron extraction process and optimizing the brilliance. Design and optimiziation of the moderator system are conducted with MCNP and will be validated with measurements at the AKR-2 training reactor by means of a prototype assembly where, e.g., the effect of different liquid H2 ortho/para ratios will be investigated and controlled in realtime via online heat capacity measurements.

  18. Surface physics with cold and thermal neutron reflectometry. Progress report, April 1, 1991--September 30, 1993

    SciTech Connect

    Steyerl, A.

    1993-09-01

    Within the past two and one half years of the project ``Surface Physics With Cold and Thermal Neutron Reflectometry`` a new thermal neutron reflectometer was constructed at the Rhode Island Nuclear Science Center (RINSC). It was used to study various liquid and solid surfaces. Furthermore, neutron reflection experiments were be un at different laboratories in collaboration with Dr. G.P. Fetcher (at Argonne National Laboratory), Dr. T. Russell (IBM Almaden) and Drs. S.K. Satija and A. Karim (at the National Institute for Standards and Technology). The available resources allowed partial construction of an imaging system for ultracold neutrons. It is expected to provide an extremely high resolution in momentum and energy transfer in surface studies using neutron reflectometry. Much of the work reported here was motivated by the possibility of later implementation at the planned Advanced Neutron Source at Oak Ridge. In a separate project the first concrete plans for an intense source of ultracold neutrons for the Advanced Neutron Source were developed.

  19. Determination of (n,γ) Cross Sections of 241Am by Cold Neutron Activation

    NASA Astrophysics Data System (ADS)

    Genreith, C.; Rossbach, M.; Révay, Zs.; Kudejova, P.

    2014-05-01

    Accurate cross section data of actinides are crucial for criticality calculations of GEN IV reactors and transmutation but also for analytical purposes such as nuclear waste characterization, decommissioning of nuclear installations and safeguard applications. Tabulated data are inconsistent and sometimes associated with large uncertainties. Neutron activation with external cold neutron beams from high flux reactors offers a chance for determination of accurate capture cross sections scalable to the whole 1/√{E}-region even for isotopes with low-lying resonances like 241Am. Preparation of 241Am samples for irradiation at the PGAA station of the FRM II in Garching has been optimized together with PTB in Braunschweig. Two samples were irradiated together with gold flux monitors to extract the thermal neutron capture cross section after appropriate corrections for attenuation of neutrons and photons in the sample. For one sample, the thermal ground state neutron capture cross section was measured as 663.0 ± 28.8 b. The thermal neutron capture cross section was calculated to 725.4 ± 34.4 b. For the other sample, a ground state neutron capture cross section of 649.9 ± 28.2 b was measured and a thermal neutron capture cross section of 711.1 ± 33.9 b was derived.

  20. The upgraded cold neutron triple-axis spectrometer FLEXX - enhanced capabilities by new instrumental options

    NASA Astrophysics Data System (ADS)

    Habicht, Klaus; Lucía Quintero-Castro, Diana; Toft-Petersen, Rasmus; Kure, Mathias; Mäde, Lucas; Groitl, Felix; Le, Manh Duc

    2015-01-01

    The upgrade of the cold neutron triple axis spectrometer FLEXX, a work-horse instrument for inelastic neutron scattering matching the sample environment capabilities at Helmholtz-Zentrum Berlin, has been successfully accomplished. Experiments confirmed an order of magnitude gain in flux now allowing for intensity demanding options to be fully exploited at FLEXX. In this article, we describe the layout and design of two newly available FLEXX instrument options in detail. The new Heusler analyzer gives an increase of the detected polarized neutron flux due to its superior focusing properties, significantly improving the feasibility of future polarized and neutron resonance spin echo experiments. The MultiFLEXX option provides simultaneous access to large regions in wavevector and energy space for inelastic excitations thus adding mapping capabilities to the spectrometer.

  1. On the reliability of neutron diffraction for residual stress measurement in cold-drawn steels

    NASA Astrophysics Data System (ADS)

    Ruiz-Hervias, J.; Mompean, F.; Hofmann, M.; Atienza, J. M.

    2011-10-01

    Residual strains were measured in the ferrite phase of pearlitic steel rods along the radial, axial and hoop directions. Two samples with different initial diameters were subjected to one drawing pass (using same drawing parameters) with 20% section reduction and measured in two different neutron diffraction instruments. The results show that the residual strain state is very similar in both cases, regardless of the diameter of the initial rod. This means that the final residual strain-stress state is unique and it is related to the cold-drawing process parameters. In addition, the results show the reliability of strain scanning with different neutron instruments and experimental conditions.

  2. Optimum design of a moderator system based on dose calculation for an accelerator driven Boron Neutron Capture Therapy.

    PubMed

    Inoue, R; Hiraga, F; Kiyanagi, Y

    2014-06-01

    An accelerator based BNCT has been desired because of its therapeutic convenience. However, optimal design of a neutron moderator system is still one of the issues. Therefore, detailed studies on materials consisting of the moderator system are necessary to obtain the optimal condition. In this study, the epithermal neutron flux and the RBE dose have been calculated as the indicators to look for optimal materials for the filter and the moderator. As a result, it was found that a combination of MgF2 moderator with Fe filter gave best performance, and the moderator system gave a dose ratio greater than 3 and an epithermal neutron flux over 1.0×10(9)cm(-2)s(-1).

  3. The time-of-flight spectrometer with cold neutrons at the FRM-II

    NASA Astrophysics Data System (ADS)

    Zirkel, A.; Roth, S.; Schneider, W.; Neuhaus, J.; Petry, W.

    2000-03-01

    We are presenting a design study of the new cold-time-of-flight spectrometer to be built at the FRM-II. Monte Carlo techniques were used to optimize the flux at the sample position and to calculate the elastic energy resolution. A doubly focusing neutron guide is used to enhance the intensity on the sample. Magnetic bearings and carbon fiber composite disks will give access to very high chopper speeds, thereby considerably increasing the overall performance of the instrument.

  4. Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

    PubMed

    Shan, Qing; Chu, Shengnan; Jia, Wenbao

    2015-11-01

    Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer. PMID:26325583

  5. Monte Carlo simulation of moderator and reflector in coal analyzer based on a D-T neutron generator.

    PubMed

    Shan, Qing; Chu, Shengnan; Jia, Wenbao

    2015-11-01

    Coal is one of the most popular fuels in the world. The use of coal not only produces carbon dioxide, but also contributes to the environmental pollution by heavy metals. In prompt gamma-ray neutron activation analysis (PGNAA)-based coal analyzer, the characteristic gamma rays of C and O are mainly induced by fast neutrons, whereas thermal neutrons can be used to induce the characteristic gamma rays of H, Si, and heavy metals. Therefore, appropriate thermal and fast neutrons are beneficial in improving the measurement accuracy of heavy metals, and ensure that the measurement accuracy of main elements meets the requirements of the industry. Once the required yield of the deuterium-tritium (d-T) neutron generator is determined, appropriate thermal and fast neutrons can be obtained by optimizing the neutron source term. In this article, the Monte Carlo N-Particle (MCNP) Transport Code and Evaluated Nuclear Data File (ENDF) database are used to optimize the neutron source term in PGNAA-based coal analyzer, including the material and shape of the moderator and neutron reflector. The optimized targets include two points: (1) the ratio of the thermal to fast neutron is 1:1 and (2) the total neutron flux from the optimized neutron source in the sample increases at least 100% when compared with the initial one. The simulation results show that, the total neutron flux in the sample increases 102%, 102%, 85%, 72%, and 62% with Pb, Bi, Nb, W, and Be reflectors, respectively. Maximum optimization of the targets is achieved when the moderator is a 3-cm-thick lead layer coupled with a 3-cm-thick high-density polyethylene (HDPE) layer, and the neutron reflector is a 27-cm-thick hemispherical lead layer.

  6. Possibility of magnetic pumping of very cold neutrons in a guide-tube torus

    NASA Astrophysics Data System (ADS)

    Utsuro, Masahiko; Kawabata, Yuji

    1992-11-01

    Very cold neutrons (VCN) with the velocity below about 40 m/s can be confined in a guide tube torus with the tube diameter of about 5 cm and curved with a radius of about 4 meters. Thus, arranging a number of magnetic devices along the torus which force adiabatic spin flips of VCN in the strong magnetic field, a magnetic pumping of VCN into a defined energy band can be attained and a high density of ultracold neutrons will be produced with feeding VCN continuously from a connected guide tube. An analytical work on the proposed system with the realistic design parameters under actual VCN feeding intensity from the KUR VCN facility will be reported. The preparation of an experimental device is also under progress according to the present analysis in order to test the working principle of the proposed magnetic pumping of VCN to ultracold neutrons.

  7. Effects of color temperature of fluorescent lamps on body temperature regulation in a moderately cold environment.

    PubMed

    Yasukouchi, A; Yasukouchi, Y; Ishibashi, K

    2000-05-01

    A study on the effects of different color temperatures of fluorescent lamps on skin and rectal temperatures in a moderately cold environment involving (i) changes in skin temperature of 7 male subjects exposed to an ambient temperature ranging from 28 degrees C to 18 degrees C (experiment I) and (ii) changes in skin and rectal temperatures and metabolic heat production of 11 male subjects exposed to ambient temperature of 15 degrees C for 90 min (Experiment II) was conducted. In Experiment I, the reduction of mean skin temperature from the control value was significantly greater under 3000 K than under 5000 K or 7500 K lighting. In Experiment II, the reductions in mean skin temperature and rectal temperature were respectively greater and smaller under 3000 K than those under 5000 K or 7500 K lighting. However, metabolic heat production was not affected by color temperature conditions. The relationships between morphological and physiological parameters revealed that no significant relation of rectal temperature to body surface area per unit body weight was found only under 3000 K. Furthermore, while the mean skin temperature was independent on the mean skinfold thickness under 3000 K, a significant negative correlation between the rectal and mean skin temperatures was observed. Therefore, body heat loss might be suppressed effectively by increasing the vasoconstrictor tone under a color temperature of 3000 K, and the body shell was dependent only on morphological factors under 5000 K and 7500 K lighting.

  8. Washing Up with Hot and Cold Running Neutrons: Tests of Fundamental Physical Laws

    SciTech Connect

    Lamoreaux, Steve K.

    2005-05-24

    The properties of the Neutron and its interactions with matter have been long applied to tests of fundamental physical principles. An example of such an application is a test of the stability of the fundamental constants of physics based on possible changes in low energy absorption resonances and the isotopic composition of a prehistoric natural reactor that operated two billion years ago in equatorial Africa. A recent re-analysis of this event indicates that some fundamental constants have changed. The focus of the presentation will be on the uses of cold and ultracold neutrons (UCNs), and in particular, the experimental search for the neutron electric dipole moment (EDM) which would be evidence for time reversal asymmetry in the microscopic interactions within the neutron. Ultracold neutrons are neutrons with kinetic energy sufficiently low that they can be reflected from material surfaces for all angles of incidence, allowing UCNs to be stored in material bottles for times approaching the beta decay lifetime of the neutron. Vagaries associated with the production, transport, and storage of UCNs will be described, and an overview progress on development of a new neutron EDM experiment to be operated at LANSCE will be presented. This new experiment has potential to improve the measurement sensitivity by a factor of 100. Although an EDM has not be observed for any elementary particle, experimental limits have been crucial for testing extensions to the so-called Standard Model of Electroweak Interactions. Our anticipated sensitivity will be sufficient to address questions regarding the observed matter-antimatter asymmetry in the Universe.

  9. Washing Up with Hot and Cold Running Neutrons: Tests of Fundamental Physical Laws

    NASA Astrophysics Data System (ADS)

    Lamoreaux, Steve K.

    2005-05-01

    The properties of the Neutron and its interactions with matter have been long applied to tests of fundamental physical principles. An example of such an application is a test of the stability of the fundamental constants of physics based on possible changes in low energy absorption resonances and the isotopic composition of a prehistoric natural reactor that operated two billion years ago in equatorial Africa. A recent re-analysis of this event indicates that some fundamental constants have changed. The focus of the presentation will be on the uses of cold and ultracold neutrons (UCNs), and in particular, the experimental search for the neutron electric dipole moment (EDM) which would be evidence for time reversal asymmetry in the microscopic interactions within the neutron. Ultracold neutrons are neutrons with kinetic energy sufficiently low that they can be reflected from material surfaces for all angles of incidence, allowing UCNs to be stored in material bottles for times approaching the beta decay lifetime of the neutron. Vagaries associated with the production, transport, and storage of UCNs will be described, and an overview progress on development of a new neutron EDM experiment to be operated at LANSCE will be presented. This new experiment has potential to improve the measurement sensitivity by a factor of 100. Although an EDM has not be observed for any elementary particle, experimental limits have been crucial for testing extensions to the so-called Standard Model of Electroweak Interactions. Our anticipated sensitivity will be sufficient to address questions regarding the observed matter-antimatter asymmetry in the Universe.

  10. Design of Ultra Small Angle Neutron Scattering (KIST-USANS) at HANARO Cold Neutron Guide, CG4B

    NASA Astrophysics Data System (ADS)

    Kim, Man-Ho

    2013-03-01

    The ultra small angle neutron scattering instrument can measure the lower limit of scattering vector to near Q ~ 2.0x10-5 Å-1 while the upper limit can reach to an intermediate scattering vector Q ~ 10-2 Å-1 of a typical small angle neutron scattering (SANS) depending on the contrast of sample. USANS is useful when measuring objects that are micron to submicron in size while SANS is useful when measuring objects that are micron to nano in size. When both USANS and SANS were used together, we could measure sizes from micron to nano scale, which is useful when studying the hierarchical structures in the wide scale of Q and total cross-section, d Σ/d Ω(Q). Recently, KIST has developed the USANS (so called KIST-USANS) at HANARO cold neutron guide hall of KAERI. We will present the instrument design, performance, future plan, and some examples of measurements that cover approximately 11 orders of magnitude in the d Σ/d Ω(Q) and 4 orders in the Q. This work was partially supported by the KIST (2v02632) and the National Research Foundation of Korea(NRF) grant funded by the Korea government(MEST) (No. 2012M2B2A4030220)

  11. Performance of the Los Alamos National Laboratory spallation-driven solid-deuterium ultra-cold neutron source

    SciTech Connect

    Saunders, A.; Makela, M.; Bagdasarova, Y.; Boissevain, J.; Bowles, T. J.; Currie, S. A.; Hill, R. E.; Hogan, G.; Morris, C. L.; Mortensen, R. N.; Ramsey, J.; Seestrom, S. J.; Sondheim, W. E.; Teasdale, W.; Wang, Z.; Back, H. O.; Broussard, L. J.; Hoagland, J.; Holley, A. T.; Pattie, R. W. Jr.; and others

    2013-01-15

    In this paper, we describe the performance of the Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements of the cold neutron flux, the very low energy neutron production rate, and the UCN rates and density at the exit from the biological shield are presented and compared to Monte Carlo predictions. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with our custom UCN Monte Carlo code. The source is shown to perform as modeled. The maximum delivered UCN density at the exit from the biological shield is 52(9) UCN/cc with a solid deuterium volume of {approx}1500 cm{sup 3}.

  12. Mass, radius and composition of the outer crust of nonaccreting cold neutron stars

    NASA Astrophysics Data System (ADS)

    Hempel, Matthias; Schaffner-Bielich, Jürgen

    2008-01-01

    The properties and composition of the outer crust of nonaccreting cold neutron stars are studied by applying the model of Baym, Pethick and Sutherland, which was extended by including higher order corrections of the atomic binding, screening, exchange and zero-point energy. The most recent experimental nuclear data from the atomic mass table of Audi, Wapstra and Thibault from 2003 are used. Extrapolation to the drip line is utilized by various state-of-the-art theoretical nuclear models (finite range droplet, relativistic nuclear field and non-relativistic Skyrme Hartree Fock parameterizations). The different nuclear models are compared with respect to the mass and radius of the outer crust for different neutron star configurations and the nuclear compositions of the outer crust.

  13. Angular distribution of products of ternary nuclear fission induced by cold polarized neutrons

    SciTech Connect

    Bunakov, V. E. Kadmensky, S. G. Kadmensky, S. S.

    2008-11-15

    Within quantum fission theory, angular distributions of products originating from the ternary fission of nuclei that is induced by polarized cold and thermal neutrons are investigated on the basis of a non-evaporative mechanism of third-particle emission and a consistent description of fission-channel coupling. It is shown that the inclusion of Coriolis interaction both in the region of the discrete and in the region of the continuous spectrum of states of the system undergoing fission leads to T-odd correlations in the aforementioned angular distributions. The properties of the TRI and ROT effects discovered recently, which are due to the interference between the fission amplitudes of neutron resonances, are explored. The results obtained here are compared with their counterparts from classic calculations based on the trajectory method.

  14. Development of a cold-neutron imaging detector based on thick gaseous electron multiplier.

    PubMed

    Cortesi, M; Zboray, R; Kaestner, A; Prasser, H-M

    2013-02-01

    We present the results of our recent studies on a cold-neutron imaging detector prototype based on THick Gaseous Electron Multiplier (THGEM). The detector consists of a thin Boron layer, for neutron-to-charged particle conversion, coupled to two THGEM electrodes in cascade for charge amplification and a position-sensitive charge-readout anode. The detector operates in Ne∕(5%)CF4, at atmospheric pressure, in a stable condition at a gain of around 10(4). Due to the geometrical structure of the detector elements (THGEM geometry and charge read-out anode), the image of detector active area shows a large inhomogeneity, corrected using a dedicated flat-filed correction algorithm. The prototype provides a detection efficiency of 5% and an effective spatial resolution of the order of 1.3 mm.

  15. Performance of the solid deuterium ultra-cold neutron source at the pulsed reactor TRIGA Mainz

    NASA Astrophysics Data System (ADS)

    Karch, J.; Sobolev, Yu.; Beck, M.; Eberhardt, K.; Hampel, G.; Heil, W.; Kieser, R.; Reich, T.; Trautmann, N.; Ziegner, M.

    2014-04-01

    The performance of the solid deuterium ultra-cold neutron (UCN) source at the pulsed reactor TRIGA Mainz with a maximum peak energy of 10MJ is described. The solid deuterium converter with a volume of cm3 (8mol), which is exposed to a thermal neutron fluence of n/cm2, delivers up to 240000 UCN ( m/s) per pulse outside the biological shield at the experimental area. UCN densities of 10 cm3 are obtained in stainless-steel bottles of 10 L. The measured UCN yields compare well with the predictions from a Monte Carlo simulation developed to model the source and to optimize its performance for the upcoming upgrade of the TRIGA Mainz into a user facility for UCN physics.

  16. Development of a cold-neutron imaging detector based on thick gaseous electron multiplier

    SciTech Connect

    Cortesi, M.; Zboray, R.; Kaestner, A.; Prasser, H.-M.

    2013-02-15

    We present the results of our recent studies on a cold-neutron imaging detector prototype based on THick Gaseous Electron Multiplier (THGEM). The detector consists of a thin Boron layer, for neutron-to-charged particle conversion, coupled to two THGEM electrodes in cascade for charge amplification and a position-sensitive charge-readout anode. The detector operates in Ne/(5%)CF{sub 4}, at atmospheric pressure, in a stable condition at a gain of around 10{sup 4}. Due to the geometrical structure of the detector elements (THGEM geometry and charge read-out anode), the image of detector active area shows a large inhomogeneity, corrected using a dedicated flat-filed correction algorithm. The prototype provides a detection efficiency of 5% and an effective spatial resolution of the order of 1.3 mm.

  17. Approaching complete low-spin spectroscopy of 210Bi with a cold-neutron capture reaction

    NASA Astrophysics Data System (ADS)

    Cieplicka-Oryńczak, N.; Fornal, B.; Leoni, S.; Bazzacco, D.; Blanc, A.; Bocchi, G.; Bottoni, S.; de France, G.; Jentschel, M.; Köster, U.; Mutti, P.; Simpson, G.; Soldner, T.; Szpak, B.; Ur, C.; Urban, W.

    2016-05-01

    The low-spin structure of the 210Bi nucleus was investigated in the neutron capture experiment 209Bi(n ,γ )210Bi performed at ILL Grenoble at the PF1B cold-neutron facility. By using the EXILL multidetector array, consisting of 46 high-purity germanium crystals, and γ γ -coincidence technique, 64 primary γ rays were observed (40 new) and a total number of 70 discrete states (33 new) were located below the neutron binding energy in 210Bi. The analysis of the angular correlations of γ rays provided information about transitions multipolarities, which made it possible to confirm most of the previously known spin-parity assignments and helped establish new ones. The obtained experimental results were compared to shell-model calculations involving one-valence-proton, one-valence-neutron excitations outside the 208Pb core. It has been found that while up to the energy of ˜2 MeV each state observed in 210Bi has its calculated counterpart; at higher excitation energies some levels cannot be described by the valence particle couplings. These states may arise from couplings of valence particles to the 3- octupole phonon of the doubly magic 208Pb core and may serve as a testing ground for models which describe single particle-phonon excitations.

  18. Prompt gamma-ray analysis using cold and thermal guided neutron beams at JAERI.

    PubMed

    Yonezawa, C

    1999-01-01

    A highly sensitive neutron-induced prompt gamma-ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M, has been constructed. The system was designed to achieve the lowest gamma-ray background by using lithium fluoride tiles as neutron shielding, by placing the samples in a He atmosphere and by using a Ge-bismuth germanate detector system for Compton suppression. The gamma-ray spectrometer can acquire three modes of spectra simultaneously: single, Compton suppression, and pair modes. Because of the low-energy guided neutron beams and the low-background system, analytical sensitivities and detection limits better than those in usual PGA systems have been achieved. Boron and multielemental determination by a comparative standardization have been investigated, and accuracy, precision, and detection limits for the elements in various materials were evaluated. The system has been applied to the determination of B and multielements in samples of various fields such as medical, environmental, and geological sciences.

  19. Cold Uniform Matter and Neutron Stars in the Quark-Meson-Coupling Model

    SciTech Connect

    J.R. Stone; P.A.M. Guichon; H.H. Matevosyan; A.W. Thomas

    2007-08-01

    A new density dependent effective baryon-baryon interaction has been recently derived from the quark-meson-coupling (QMC) model, offering impressive results in application to finite nuclei and dense baryon matter. This self-consistent, relativistic quark-level approach is used to construct the Equation of State (EoS) and to calculate key properties of high density matter and cold, slowly rotating neutron stars. The results include predictions for the maximum mass of neutron star models, together with the corresponding radius and central density, as well the properties of neutron stars with mass of order 1.4 M{sub {circle_dot}}. The cooling mechanism allowed by the QMC EoS is explored and the parameters relevant to slow rotation, namely the moment of inertia and the period of rotation investigated. The results of the calculation, which are found to be in good agreement with available observational data, are compared with the predictions of more traditional EoS, based on the A18+{delta}v+UIX* and modified Reid soft core potentials, the Skyrme SkM* interaction and two relativistic mean field (RMF) models for a hybrid stars including quark matter. The QMC EoS provides cold neutron star models with maximum mass 1.9-2.1 M{sub {circle_dot}}, with central density less than 6 times nuclear saturation density (n{sub 0} = 0.16 fm{sup -3}) and offers a consistent description of the stellar mass up to this density limit. In contrast with other models, QMC predicts no hyperon contribution at densities lower than 3n{sub 0}, for matter in {beta}-equilibrium. At higher densities, {Xi}{sup -,0} and {Lambda} hyperons are present. The absence of lighter {Sigma}{sup {+-},0} hyperons is understood as a consequence of antisymmetrization, together with the implementation of the color hyperfine interaction in the response of the quark bag to the nuclear scalar field.

  20. 232Th, 233Pa, and 234U capture cross-section measurements in moderated neutron flux

    NASA Astrophysics Data System (ADS)

    Bringer, O.; Isnard, H.; AlMahamid, I.; Chartier, F.; Letourneau, A.

    2008-07-01

    The Th-U cycle was studied through the evolution of a 100 μg 232Th sample irradiated in a moderated neutron flux of 8.010 14 n/cm 2/s, intensity close to that of a thermal molten salt reactor. After 43 days of irradiation and 6 months of cooling, a precise mass spectrometric analysis, using both TIMS and MC-ICP-MS techniques, was performed, according to a rigorous methodology. The measured thorium and uranium isotopic ratios in the final irradiated sample were then compared with integral simulations based on evaluated data; an overall good agreement was seen. Four important thermal neutron-capture cross-sections were also extracted from the measurements, 232Th (7.34±0.21 b), 233Pa (38.34±1.78 b), 234U (106.12±3.34 b), and 235U (98.15±11.24 b). Our 232Th and 235U results confirmed existing values whereas the cross-sections of 233Pa and 234U (both key parameters) have been redefined.

  1. s-IgA response in females following a single bout of moderate intensity exercise in cold and thermoneutral environments.

    PubMed

    Mylona, E; Fahlman, M M; Morgan, A L; Boardley, D; Tsivitse, S K

    2002-08-01

    Previous research has linked exercise under unfavourable environmental conditions to decreased concentration and/or secretion rate of secretory immunoglobulin A (s-IgA). The purpose of this study was to investigate the influence of moderate exercise in a thermoneutral (TN) and a cold (COLD) environment on the concentration of s-IgA and the secretion rate of s-IgA in moderately active females. Sixteen females (23.4 +/- 6.8 yrs, 61.1 +/- 5.9 kg, 1.64 +/- 0.07 m) served as subjects for this study. On separate occasions, one week apart, all subjects ran or walked for 30 minutes at 71 % of individual heart rate reserve on an outdoor (1 degrees C) or an indoor track (24 degrees C). Unstimulated saliva samples were collected for 4-min immediately pre (PR), post (POST), and 30-min post (30POST) exercise. Profile of Mood State (POMS) questionnaires were completed pre and post exercise intervention and Global Mood State (GMS) was calculated. The absolute concentration of s-IgA, and total non-specific protein were measured and the secretion rate of s-IgA and s-IgA:Protein were calculated. Analysis of Variance (ANOVA) revealed that flow rate increased in COLD and decreased in TN such that it was significantly lower (POST) and (30POST) in the TN environment when compared to COLD. There was a significant increase in the secretion rate of s-IgA at 30POST for the COLD trial and a significant decrease at 30POST for the TN trial. No significant differences were found for the concentration of s-IgA, the s-IgA:Protein:ratio, or GMS. Stepwise regression revealed that with all predictors in the model, only the concentration of s-IgA accounted for a significant proportion of the variance in cold temperature, while in the TN environment, both the concentration of s-IgA and the flow rate accounted for significant proportions of the variance. These findings suggest that moderate exercise in cold temperatures does not decrease secretion rate of s-IgA, while exercise in TN temperatures does.

  2. Modeling and design of a new core-moderator assembly and neutron beam ports for the Penn State Breazeale Nuclear Reactor (PSBR)

    NASA Astrophysics Data System (ADS)

    Ucar, Dundar

    modeling, the amount of heat generated by the fuel is assumed to be transferred totally into the coolant. Therefore, the surface heat flux is applied to the fuel cladding outer surface by considering the depleted fuel composition of each individual fuel rod under a reference core loading condition defined as; 53H at 1MW full power. In order to model the entire PSBR reactor, fine mesh discretization was achieved with 22 millions structured and unstructured computational meshes. The conductive heat transfer inside the fuel rods was ignored in order to decrease the computational mesh requirement. Since the PSBR core operates in the subcooled nucleate boiling region, the CFD simulation of new PSBR design was completed utilizing an Eulerian-Eulerian multiphase flow formulation and RPI wall boiling model. The simulation results showed that the new moderator tank geometry results in secondary flow entering into the core due to decrease in the cross-flow area. Notably, the radial flow improves the local heat transfer conditions by providing radial-mixing in the core. Bubble nucleation occurs on the heated fuel rods but bubbles are collapsing in the subcooled fluid. Furthermore, the bulk fluid properties are not affected by the bubble formation. Yet, subcooled boiling enhances the heat transfer on the fuel rods. Five neutron beam ports are designed for the new reactor. The geometrical configuration, filter and collimator system designs of each neutron beam ports are selected based on the requirements of the experimental facilities. A cold neutron beam port which utilizes cold neutrons from three curved guide tubes is considered. Therefore, there will be seven neutron beams available in the new facility. The neutronic analyses of the new beam port designs were achieved by using MCNP5 code and Burned Coupled Simulation Tool for the PSBR. The MCNP simulation results showed that thermal neutron flux was increased by a factor of minimum 1.23 times and maximum 2.68 times in the new beam

  3. Moderator design studies for a new neutron reference source based on the D-T fusion reaction

    NASA Astrophysics Data System (ADS)

    Mozhayev, Andrey V.; Piper, Roman K.; Rathbone, Bruce A.; McDonald, Joseph C.

    2016-06-01

    The radioactive isotope Californium-252 (252Cf) is relied upon internationally as a neutron calibration source for ionizing radiation dosimetry because of its high specific activity. The source may be placed within a heavy-water (D2O) moderating sphere to produce a softened spectrum representative of neutron fields common to commercial nuclear power plant environments, among others. Due to termination of the U.S. Department of Energy loan/lease program in 2012, the expense of obtaining 252Cf sources has undergone a significant increase, rendering high output sources largely unattainable. On the other hand, the use of neutron generators in research and industry applications has increased dramatically in recent years. Neutron generators based on deuteriumtritium (D-T) fusion reaction provide high neutron fluence rates and, therefore, could possibly be used as a replacement for 252Cf. To be viable, the 14 MeV D-T output spectrum must be significantly moderated to approximate common workplace environments. This paper presents the results of an effort to select appropriate moderating materials and design a configuration to reshape the primary neutron field toward a spectrum approaching that from a nuclear power plant workplace. A series of Monte-Carlo (MCNP) simulations of single layer high- and low-Z materials are used to identify initial candidate moderators. Candidates are refined through a similar series of simulations involving combinations of 2-5 different materials. The simulated energy distribution using these candidate moderators are rated in comparison to a target spectrum. Other properties, such as fluence preservation and/or enhancement, prompt gamma production and other characteristics are also considered.

  4. Determination of hydrogen in metals, semiconductors, and other materials by cold neutron prompt gamma-ray activation analysis

    SciTech Connect

    Paul, R.L.; Lindstrom, R.M.

    1998-12-31

    Cold neutron prompt gamma-ray activation analysis has proven useful for nondestructive measurement of trace hydrogen. The sample is irradiated in a beam of neutrons; the presence of hydrogen is confirmed by the emission of a 2223 keV gamma-ray. Detection limits for hydrogen are 3 mg/kg in quartz and 8 mg/kg in titanium. The authors have used the technique to measure hydrogen in titanium alloys, germanium, quartz, fullerenes and their derivatives, and other materials.

  5. Isolation of two strong poly (U) binding proteins from moderate halophile Halomonas eurihalina and their identification as cold shock proteins.

    PubMed

    Garapati, Usha Kumari; Suryanarayana, Tangirala

    2012-01-01

    Cold shock proteins (Csp) are known to be expressed in response to sudden decrease in temperature. They are thought to be involved in a number of cellular processes viz., RNA chaperone activity, translation, transcription, nucleoid condensation. During our studies on ribosomal protein S1 in moderate halophile Halomonas eurihalina, we observed the presence of two strong poly (U) binding proteins in abundance in cell extracts from cells grown under normal growth conditions. The proteins can be isolated in a single step using Poly (U) cellulose chromatography. The proteins were identified as major cold shock proteins belonging to Csp A family by MALDI-TOF and bioinformatic analysis. Csp 12 kDa was found in both exponential and stationary phases whereas Csp 8 kDa is found only in exponential phase.

  6. Radiogenic lead with dominant content of {sup 208}Pb: New coolant and neutron moderator for innovative nuclear reactors

    SciTech Connect

    Shmelev, A. N.; Kulikov, G. G.; Kryuchkov, E. F.; Apse, V. A.; Kulikov, E. G.

    2012-07-01

    The advantages of radiogenic lead with dominant content of {sup 208}Pb as a reactor coolant with respect to natural lead are caused by unique nuclear properties of {sup 208}Pb which is a double-magic nucleus with closed proton and neutron shells. This results in significantly lower micro cross section and resonance integral of radiative neutron capture by {sup 208}Pb than those for numerous light neutron moderators. The extremely weak ability of {sup 208}Pb to absorb neutrons results in the following effects. Firstly, neutron moderating factor (ratio of scattering to capture cross sections) is larger than that for graphite and light water. Secondly, age and diffusion length of thermal neutrons are larger than those for graphite, light and heavy water. Thirdly, neutron lifetime in {sup 208}Pb is comparable with that for graphite, beryllium and heavy water what could be important for safe reactor operation. The paper presents some results obtained in neutronics and thermal-hydraulics evaluations of the benefits from the use of radiogenic lead with dominant content of {sup 208}Pb instead of natural lead as a coolant of fast breeder reactors. The paper demonstrates that substitution of radiogenic lead for natural lead can offer the following benefits for operation of fast breeder reactors. Firstly, improvement of the reactor safety thanks to the better values of coolant temperature reactivity coefficient and, secondly, improvement of some thermal-hydraulic reactor parameters. Radiogenic lead can be extracted from thorium sludge without isotope separation as {sup 208}Pb is a final isotope in the decay chain of {sup 232}Th. (authors)

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

  8. Rainbow trout resistance to bacterial cold-water disease is moderately heritable and is not adversely correlated with growth.

    PubMed

    Silverstein, J T; Vallejo, R L; Palti, Y; Leeds, T D; Rexroad, C E; Welch, T J; Wiens, G D; Ducrocq, V

    2009-03-01

    The objectives of this study were to estimate the heritabilities for and genetic correlations among resistance to bacterial cold-water disease and growth traits in a population of rainbow trout (Oncorhynchus mykiss). Bacterial cold-water disease, a chronic disease of rainbow trout, is caused by Flavobacterium psychrophilum. This bacterium also causes acute losses in young fish, known as rainbow trout fry syndrome. Selective breeding for increased disease resistance is a promising strategy that has not been widely used in aquaculture. At the same time, improving growth performance is critical for efficient production. At the National Center for Cool and Cold Water Aquaculture, reducing the negative impact of diseases on rainbow trout culture and improving growth performance are primary objectives. In 2005, when fish averaged 2.4 g, 71 full-sib families were challenged with F. psychrophilum and evaluated for 21 d. Overall survival was 29.3% and family rates of survival varied from 1.5 to 72.5%. Heritability of postchallenge survival, an indicator of disease resistance, was estimated to be 0.35 +/- 0.09. Body weights at 9 and 12 mo posthatch and growth rate from 9 to 12 mo were evaluated on siblings of the fish in the disease challenge study. Growth traits were moderately heritable, from 0.32 for growth rate to 0.61 for 12-mo BW. Genetic and phenotypic correlations between growth traits and resistance to bacterial cold-water disease were not different from zero. These results suggest that genetic improvement can be made simultaneously for growth and bacterial cold-water disease resistance in rainbow trout by using selective breeding.

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

    PubMed

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

    2015-05-01

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

  10. Heightened cold pain and pressure pain sensitivity in young female adults with moderate-to-severe menstrual pain.

    PubMed

    Slater, Helen; Paananen, Markus; Smith, Anne J; OʼSullivan, Peter; Briggs, Andrew M; Hickey, Martha; Mountain, Jenny; Karppinen, Jaro; Beales, Darren

    2015-12-01

    This study investigated the association between menstrual pain severity and psychophysical measures of cold and pressure pain sensitivity. A cross-sectional design was used with young women (n = 432) from the Western Australian Pregnancy Cohort (Raine) Study. Menstrual pain severity and oral contraception use was obtained from questionnaires at 20 and 22-year follow-ups. A visual analog scale (VAS; range from 0 [none] to 10 [unbearable]) was used to measure menstrual pain severity at both 20 and 22 years over the 3-year period, with 3 groups created: (1) no pain or mild pain (VAS 0-3), (2) at least moderate pain at a minimum of 1 of the 2 time points (hereafter named "mixed)", and (3) severe pain (VAS 8-10). Cold pain sensitivity (dorsal wrist) and pressure pain sensitivity (lumbar spine, upper trapezius, dorsal wrist, and tibialis anterior) were assessed using standardised quantitative sensory testing protocols. Confounding variables included number of musculoskeletal pain sites, oral contraceptive use, smoking, physical activity, body mass index, psychological distress, and sleep. Severe menstrual pain and mixed menstrual pain were positively associated with heightened cold pain sensitivity (distant from menstrual pain referral site) and pressure pain sensitivity (local to menstrual pain referral site). These associations remained significant after adjusting for potential confounding variables including multisite musculoskeletal pain. Our findings suggest peripheral and central neurophysiological mechanisms contributing to heightened pain sensitivity in young women with moderate and severe menstrual pain. These data highlight the need for innovative management approaches to attenuate the negative impact of severe menstrual pain in young women. PMID:26262827

  11. LENS: A New Pulsed Neutron Source for Research and Education

    PubMed Central

    Leuschner, M.; Baxter, D. V.; Cameron, J. M.; Derenchuk, V.; Lavelle, C.; Lone, A.; Nann, H.; Rinckel, T.; Snow, W. M.

    2005-01-01

    A new pulsed neutron source is under construction at the Indiana University Cyclotron Facility (IUCF). Neutrons are produced via (p,n) reactions by a low-energy proton beam incident on a thin beryllium target. The source is tightly coupled to a cold methane moderator held at a temperature of 20 K or below. The resulting time-averaged cold neutron flux is expected to be comparable to that of the Intense Pulsed Neutron Source (IPNS) facility at Argonne National Laboratory. The initial experimental suite will include instrumentation for small angle neutron scattering (SANS), moderator studies, radiography, and zero-field spin-echo SANS. PMID:27308113

  12. Semipilot plant pulse energized cold-precharger electrostatic precipitator tests for collection of moderately high resistivity flyash particles

    SciTech Connect

    Jayaram, S.; Castle, G.S.P.; Chang, J.S.; Berezin, A.A.; Looy, P.C.; Mangal, R.; Mozes, M.S.

    1996-07-01

    The performance of an electrostatic precipitator (ESP) to collect moderately high resistivity flyash has been tested under pulse/precharger energization using the semipilot scale integrated electrostatics combustion flue gas (IECFG) cleaning system at Ontario Hydro`s 640 MJ/h Combustion Research Facility Center. The pulse energization enhanced the performance of the existing dc energized wire-plate electrostatic precipitator in collecting moderately high resistivity ({rho} {approximately} 10{sup 10} {Omega}{center_dot}cm) flyash. A 26% improvement in particle collection efficiency and 30% energy saving were obtained with pulse energization, with moderately high resistivity flyash generated by burning high-sulfur (3.7%) Nova Scotia coal with limestone conditioning. The cold precharger specially designed to suit the three-stage wire-plate ESP gas also been tested for its ability to improve the performance of ESP in reducing the back corona. With an additional 30% of energy supplied to the precharger it was possible to obtain up to 40% enhancement in collection efficiency. In general an enhancement factor of 1.8--2.8 was obtained with dust loading {approximately}2 g/m{sup 3}.

  13. Production of tritium, neutrons, and heat based on the transmission resonance model (TRM) for cold fusion

    NASA Astrophysics Data System (ADS)

    Bush, Robert T.

    1991-05-01

    The TRM has recently been successful in fitting calorimetric data having interesting nonlinear structure. The model appears to provide a natural description for electrolytic cold fusion in terms of ``fractals''. Extended to the time dimension, the model can apparently account for the phenomenon of heat ``bursts''. The TRM combines a transmission condition involving quantized energies and an engergy shift of a Maxwell-Boltzmann energy distribution of deuterons at the cathodic surface that appears related to the concentration overpotential (hydrogen overvoltage). The model suggest three possible regimes vis-a-vis tritium production in terms of this energy shift, and indicates why measurable tritium production in the electrolytic case will tend to be the exception rather than the rule in absence of a recipe: Below a shift of approximately 2.8 meV there is production of both tritium and measureable excess heat, with the possibility of accounting for the Bockris curve indicating about a 1% correlation between excess heat and tritium. However, over the large range from about 2.8 meV to 340 meV energy shift there is a regime of observable excess heat production but little, and probably no measurable, tritium production. The third regime is more hypothetical: It begins at an energy shift of about 1 keV and extends to the boundaries of ``hot'' fusion at about 10 keV. A new type of nucelar reaction, trint (for transmission resonance-induced neutron transfer), is suggested by the model leading to triton and neutron production. A charge distribution ``polarization conjecture'' is the basis for theoretical derivation for the low-energy limit for an energy-dependent branching ratio for D-on-D. When the values of the parameters are inserted, this expression yields an estimate for the ratio of neutron-to-triton production of about 1.64×10-9. The possibility of some three-body reactions is also suggested. A comparison of the TRM's transmission energy levels for palladium deuteride

  14. Influence of projectile neutron number on cross section in cold fusion reactions

    SciTech Connect

    Dragojevic, Irena; Dragojevic, I.; Gregorich, K.E.; Dullmann, Ch.E.; Folden III, C.M.; Garcia, M.A.; Gates, J.M.; Nelson, S.L.; Sudowe, R.; Nitsche, H.

    2007-09-01

    Elements 107-112 [1,2] have been discovered in reactions between {sup 208}Pb or {sup 209}Bi targets and projectiles ranging from {sup 54}Cr through {sup 70}Zn. In such reactions, the compound nucleus can be formed at excitation energies as low as {approx}12 MeV, thus this type of reaction has been referred to as 'cold fusion'. The study of cold fusion reactions is an indispensable approach to gaining a better understanding of heavy element formation and decay. A theoretical model that successfully predicts not only the magnitudes of cold fusion cross sections, but also the shapes of excitation functions and the cross section ratios between various reaction pairs was recently developed by Swiatecki, Siwek-Wilczynska, and Wilczynski [3,4]. This theoretical model, also referred to as Fusion by Diffusion, has been the guide in all of our cold fusion studies. One particularly interesting aspect of this model is the large predicted difference in cross sections between projectiles differing by two neutrons. The projectile pair where this difference is predicted to be largest is {sup 48}Ti and {sup 50}Ti. To test and extend this model, {sup 208}Pb({sup 48}Ti,n){sup 255}Rf and {sup 208}Pb({sup 50}Ti,n){sup 257}Rf excitation functions were recently measured at the Lawrence Berkeley National Laboratory's (LBNL) 88-Inch Cyclotron utilizing the Berkeley Gas-filled Separator (BGS). The {sup 50}Ti reaction was carried out with thin lead targets ({approx}100 {micro}g/cm{sup 2}), and the {sup 48}Ti reaction with both thin and thick targets ({approx}470 {micro}g/cm{sup 2}). In addition to this reaction pair, reactions with projectile pairs {sup 52}Cr and {sup 54}Cr [5], {sup 56}Fe and {sup 58}Fe [6], and {sup 62}Ni [7] and {sup 64}Ni [8] will be discussed and compared to the Fusion by Diffusion predictions. The model predictions show a very good agreement with the data.

  15. On the possibility to image thermal and cold neutron with sub-15 μm spatial resolution

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Vallerga, J. V.; McPhate, J. B.; Siegmund, O. H. W.; Feller, W. B.; Crow, L.; Cooper, R. G.

    2008-07-01

    Due to the absence of efficient neutron focusing optics the spatial resolution needed for neutron imaging requires either a high-resolution detector, as in the case of direct projection radiography, or else a bright point source as in the case of magnification imaging geometry. The very limited neutron flux in the latter makes it unacceptably slow and thus puts more emphasis on improving the detector resolution. In this paper, we present the first experimental evidence of imaging both thermal and cold neutrons with a spatial accuracy better than 15 μm FWHM. This resolution is possible due to some unique features of neutron sensitive microchannel plates (MCPs). The position of the neutron capture event can be determined with high accuracy because the event is contained within a single or two channels of the MCP. The products of neuron capture have ranges of only a few microns in the MCP glass. The channel has a typical diameter of 6-10 μm and the inter-channel wall thickness averages 2-3 μm. Once the neutron capture initiates an electron avalanche in the MCP, the event position encoding is identical with photon/charged particle detection, for which the MCP technology has been widely used for several decades. Images demonstrating single channel resolution were taken using cold neutrons incident on a Gd pinhole mask and one with 20-50 μm B 4C particles. The proof-of-principle images were obtained at a low count rate limited by the present version of the readout electronics. Development of a new fast readout schemes is an active area of research and the rate capability of this detector should benefit from these efforts.

  16. Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

    PubMed

    Hashimoto, Y; Hiraga, F; Kiyanagi, Y

    2015-12-01

    We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation. PMID:26272165

  17. Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

    PubMed

    Hashimoto, Y; Hiraga, F; Kiyanagi, Y

    2015-12-01

    We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation.

  18. Reprint of The improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator.

    PubMed

    Ueda, H; Tanaka, H; Sakurai, Y

    2015-12-01

    Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated. PMID:26508275

  19. The improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator.

    PubMed

    Ueda, H; Tanaka, H; Sakurai, Y

    2015-10-01

    Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated.

  20. Reprint of The improvement of the energy resolution in epi-thermal neutron region of Bonner sphere using boric acid water solution moderator.

    PubMed

    Ueda, H; Tanaka, H; Sakurai, Y

    2015-12-01

    Bonner sphere is useful to evaluate the neutron spectrum in detail. We are improving the energy resolution in epi-thermal neutron region of Bonner sphere, using boric acid water solution as a moderator. Its response function peak is narrower than that for polyethylene moderator and the improvement of the resolution is expected. The resolutions between polyethylene moderator and boric acid water solution moderator were compared by simulation calculation. Also the influence in the uncertainty of Bonner sphere configuration to spectrum estimation was simulated.

  1. Response components of LiF:Mg,Ti around a moderated Am-Be neutron source.

    PubMed

    Méndez, R; Iñiguez, M P; Barquero, R; Mañanes, A; Gallego, E; Lorente, A; Voytchev, M

    2002-01-01

    The responses of TLD-1010, TLD-700 and TLD-600 thermoluminescence dosemeters to the radiation field inside a water tank enclosing an isotopic 241Am-Be neutron source are analysed. Separate contributions coming from thermal neutrons, neutrons with energies above thermal and gamma rays to the total response of the three types of TLD are obtained. This is accomplished by assuming that the gamma responses for materials with different 6Li enrichments are identical and that the neutron response of TLD-700 is negligible compared to TLD-100 and TLD-600. The last assumption is tested by Monte Carlo simulations of the neutron energy spectrum at the points where the TLDs are irradiated.

  2. SU-E-T-108: Development of a Novel Clinical Neutron Dose Monitor for Proton Therapy Based On Twin TLD500 Chips in a Small PE Moderator

    SciTech Connect

    Hentschel, R; Mukherjee, B

    2014-06-01

    Purpose: In proton therapy, it could be desirable to measure out-of-field fast neutron doses at critical locations near and outside the patient body. Methods: The working principle of a novel clinical neutron dose monitor is verified by MCNPX simulation. The device is based on a small PE moderator of just 5.5cm side length for easy handling covered with a thermal neutron suppression layer. In the simulation, a polystyrene phantom is bombarded with a standard proton beam. The secondary thermal neutron flux produced inside the moderator by the impinging fast neutrons from the treatment volume is estimated by pairs of α-Al2O3:C (TLD500) chips which are evaluated offline after the treatment either by TL or OSL methods. The first chip is wrapped with 0.5mm natural Gadolinium foil converting the thermal neutrons to gammas via (n,γ) reaction. The second chip is wrapped with a dummy material. The chip centers have a distance of 2cm from each other. Results: The simulation shows that the difference of gamma doses in the TLD500 chips is correlated to the mean fast neutron dose delivered to the moderator material. Different outer shielding materials have been studied. 0.5mm Cadmium shielding is preferred for cost reasons and convenience. Replacement of PE moderator material by other materials like lead or iron at any place is unfavorable. The spatial orientation of the moderator cube is uncritical. Using variance reduction techniques like splitting/Russian roulette, the TLD500 gamma dose simulation give positive differences up to distances of 0.5m from the treatment volume. Conclusion: Applicability and basic layout of a novel clinical neutron dose monitor are demonstrated. The monitor measures PE neutron doses at locations outside the patient body up to distances of 0.5m from the treatment volume. Tissue neutron doses may be calculated using neutron kerma factors.

  3. Scattering of very cold neutrons from the supramolecular structure of ethylene copolymers with substituted norbornene, 5-ethylidene-2-norbornene

    SciTech Connect

    Kuznetsov, S. P. Lapushkin, Yu. A.; Mitrofanov, A. V.; Shestov, S. V.; Udovenko, A. I.; Shelagin, A. V.; Meshkova, I. N.; Grinev, V. G.; Kiseleva, E. V.; Raspopov, L. N.; Shchegolikhin, A. N.; Novokshonova, L. A.

    2007-05-15

    The transformation of the nanostructure of ethylene copolymers with 5-ethylidene-2-nonbornene due to variations in the concentration of 5-ethylidene-2-nonbornene is studied using scattering of very cold neutrons. The cyclic monomer is introduced into the polyethylene chain in order to modify the supramolecular structure of polyethylene and to change its macroscopic properties. It is shown that, as the content of 5-ethylidene-2-nonbornene in the copolymer increases, the amorphous-crystalline structure of polyethylene is destroyed (the crystallinity and average crystallite size decrease). Neither scattering of very cold neutrons nor X-ray diffraction are observed in samples of ethylene copolymers in which the content of 5-ethylidene-2-nonbornene exceeds 35 mol %. The transmission of light in copolymers of ethylene with 5-ethylidene-2-nonbornene is measured at different wavelengths. It is found that an increase in the content of 5-ethylidene-2-nonbornene in the copolymer leads to an increase in the transparency of the material.

  4. Neutron and gamma detector using an ionization chamber with an integrated body and moderator

    DOEpatents

    Ianakiev, Kiril D.; Swinhoe, Martyn T.; Lestone, John Paul

    2006-07-18

    A detector for detecting neutrons and gamma radiation includes a cathode that defines an interior surface and an interior volume. A conductive neutron-capturing layer is disposed on the interior surface of the cathode and a plastic housing surrounds the cathode. A plastic lid is attached to the housing and encloses the interior volume of the cathode forming an ionization chamber, into the center of which an anode extends from the plastic lid. A working gas is disposed within the ionization chamber and a high biasing voltage is connected to the cathode. Processing electronics are coupled to the anode and process current pulses which are converted into Gaussian pulses, which are either counted as neutrons or integrated as gammas, in response to whether pulse amplitude crosses a neutron threshold. The detector according to the invention may be readily fabricated into single or multilayer detector arrays.

  5. Calculation of the absolute detection efficiency of a moderated /sup 235/U neutron detector on the Tokamak Fusion Test Reactor

    SciTech Connect

    Ku, L.P.; Hendel, H.W.; Liew, S.L.

    1989-02-01

    Neutron transport simulations have been carried out to calculate the absolute detection efficiency of a moderated /sup 235/U neutron detector which is used on the TFTR as a part of the primary fission detector diagnostic system for measuring fusion power yields. Transport simulations provide a means by which the effects of variations in various shielding and geometrical parameters can be explored. These effects are difficult to study in calibration experiments. The calculational model, benchmarked against measurements, can be used to complement future detector calibrations, when the high level of radioactivity resulting from machine operation may severely restrict access to the tokamak. We present a coupled forward-adjoint algorithm, employing both the deterministic and Monte Carlo sampling methods, to model the neutron transport in the complex tokamak and detector geometries. Sensitivities of the detector response to the major and minor radii, and angular anisotropy of the neutron emission are discussed. A semi-empirical model based on matching the calculational results with a small set of experiments produces good agreement (+-15%) for a wide range of source energies and geometries. 20 refs., 6 figs., 4 tabs.

  6. Neutron moderation in the Oklo natural reactor and the time variation of α

    NASA Astrophysics Data System (ADS)

    Lamoreaux, S. K.; Torgerson, J. R.

    2004-06-01

    In previous analyses of the Oklo (Gabon) natural reactor to test for a possible time variation of the fine-structure constant α, a Maxwell-Boltzmann low energy neutron spectrum was assumed. We present here an analysis where a more realistic spectrum is employed and show that the most recent isotopic analysis of samples implies a decrease in α, over the last 2×109 years since the reactor was operating, of (αpast-αnow)/α⩾4.5×10-8 (6σ confidence). Issues regarding the interpretation of the shifts of the low energy neutron absorption resonances are discussed.

  7. 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.

  8. The temperature dependence of ultra-cold neutron wall losses in material bottles coated with deuterated polystryene

    SciTech Connect

    Cooper, Martiin D; Bagdasarova, Yelena; Clayton, Steven M; Currie, Scott A; Griffith, William C; Ito, Takeyasu; Makela, Mark F; Morris, Cheistopher; Rahaman, Mohamad S; Ramsey, John C; Saunders, Alexander; Rios, Raymond

    2011-01-18

    Ultra-cold neutrons (UCN) from the LANSCE super-thermal deuterium source were used to fill an acrylic bottle coated with deuterated polystyrene. The bottle was constructed to minimize losses through the filling valve. The storage time was extracted from a series of measurements where the number of neutrons was counted after they were held in the bottle for durations varying from 60-1200 s. The data were collected at temperatures of 18, 40, 65, 105, and 295 K. The data has been analyzed in terms of the ratio of the imaginary to real part of the wall potential. The analysis considers the velocity dependence of the probability per bounce of wall loss. The implication of these measurements for the SNS electric dipole moment search will be presented.

  9. Neutron Flux Characterization of the Cold Beam PGAA-NIPS Facility at the Budapest Research Reactor

    NASA Astrophysics Data System (ADS)

    Belgya, T.; Kis, Z.; Szentmiklósi, L.

    2014-05-01

    Reliable flux characterization is essential for facilities using neutron beams. Hence, the NIPS station at the Budapest Research Reactor has recently been equipped with neutron-tomographic equipment. The beam can also be characterized by means of a large surface wire chamber and application of the time-of-flight method. The energy distribution was measured at three horizontal positions with the surface wire chamber in pinhole geometry, while the spatial inhomogeneity was determined by means of our new neutron-tomographic equipment.

  10. Radiometric Investigation of Water Vapour Movement in Wood-based Composites by Means of Cold and Thermal Neutrons

    NASA Astrophysics Data System (ADS)

    Solbrig, K.; Frühwald, K.; Ressel, J. B.; Mannes, D.; Schillinger, B.; Schulz, M.

    Wood-based composites are industrially produced panels made of resin-blended wood furnish material consolidated by hot pressing. Precise knowledge of the physical interrelations, such as heat and mass transfer induced densification and curing, are inevitable to control process performance and final product properties. Neutron radiography is able to distinguish between moisture and wood matter movement and thus to provide quantitative information considering the hot pressing process where only models exist. To this end, preliminary experiments were carried out utilising both cold and thermal neutrons to visualise and to quantify the water vapour movement within wood-based composites heated under sealing within a simplified mimicry of the hot pressing process conditions. Neutron radiography of this rather fast process was found to be feasible in general. The evaluation of the time-resolved image data maps the relative water content distribution within the sample during 9 min process time. A presumed wavefront-like vapour movement was confirmed. Hence, the results enhance the understanding of heat and mass transfer inside consolidated resin-blended wood furnish. These preliminary experiments prove neutron radiography as viable method for further comprehensive in-situ investigations of the hot pressing process of wood-based composites.

  11. Fast neutron spectrometry and dosimetry using a spherical moderator with position-sensitive detectors.

    PubMed

    Li, Taosheng; Yang, Lianzhen; Ma, Jizeng; Fang, Dong

    2007-01-01

    A neutron spectrometry and dosimetry measurement system has been developed based on a different design of the divided regions for a sphere, with three position-sensitive counters. The characteristics of the measurement system have been investigated in the reference radiation fields of Am-Be and (252)Cf sources. When realistic input spectra are used for the unfolding, the overall deviations of the calculated results for four dosimetric quantities are less than +/-10%. The results of other input spectra are also discussed in this report.

  12. Effects of moderate strength cold air exposure on blood pressure and biochemical indicators among cardiovascular and cerebrovascular patients.

    PubMed

    Zhang, Xiakun; Zhang, Shuyu; Wang, Chunling; Wang, Baojian; Guo, Pinwen

    2014-02-27

    The effects of cold air on cardiovascular and cerebrovascular diseases were investigated in an experimental study examining blood pressure and biochemical indicators. Zhangye, a city in Gansu Province, China, was selected as the experimental site. Health screening and blood tests were conducted, and finally, 30 cardiovascular disease patients and 40 healthy subjects were recruited. The experiment was performed during a cold event during 27-28 April 2013. Blood pressure, catecholamine, angiotensin II (ANG-II), cardiac troponin I (cTnI), muscle myoglobin (Mb) and endothefin-1 (ET-1) levels of the subjects were evaluated 1 day before, during the 2nd day of the cold exposure and 1 day after the cold air exposure. Our results suggest that cold air exposure increases blood pressure in cardiovascular disease patients and healthy subjects via the sympathetic nervous system (SNS) that is activated first and which augments ANG-II levels accelerating the release of the norepinephrine and stimulates the renin-angiotensin system (RAS). The combined effect of these factors leads to a rise in blood pressure. In addition, cold air exposure can cause significant metabolism and secretion of Mb, cTnI and ET-1 in subjects; taking the patient group as an example, ET-1 was 202.7 ng/L during the cold air exposure, increased 58 ng/L compared with before the cold air exposure, Mb and cTnI levels remained relatively high (2,219.5 ng/L and 613.2 ng/L, increased 642.1 ng/L and 306.5 ng/L compared with before the cold air exposure, respectively) 1-day after the cold exposure. This showed that cold air can cause damage to patients' heart cells, and the damage cannot be rapidly repaired. Some of the responses related to the biochemical markers indicated that cold exposure increased cardiovascular strain and possible myocardial injury.

  13. Thermal and Cold Neutron Computed Tomography at the Los Alamos Neutron Scattering Center Using an Amorphous Silicon Detector Array

    SciTech Connect

    Claytor, T.N.; Schwab, M.J.; Farnum, E.H.; McDonald, T.E.; Summa, D.A.; Sheats, M.J.; Stupin, D.M.; Sievers, W.L.

    1998-07-19

    The use of the EG and G-Heimann RTM 128 or dpiX FS20 amorphous silicon (a-Si) detector array for thermal neutron radiography/computed tomography has proven to be a quick and efficient means of producing high quality digital radiographic images. The resolution, although not as good as film, is about 750 pm with the RTM and 127 pm with the dpiX array with a dynamic range in excess of 2,800. In many respects using an amorphous silicon detector is an improvement over other techniques such as imaging with a CCD camera, using a storage phosphor plate or film radiography. Unlike a CCD camera, which is highly susceptible to radiation damage, a-Si detectors can be placed in the beam directly behind the object under examination and do not require any special optics or turning mirrors. The amorphous silicon detector also allows enough data to be acquired to construct a digital image in just a few seconds (minimum gate time 40 ms) whereas film or storage plate exposures can take many minutes and then need to be digitized with a scanner. The flat panel can therefore acquire a complete 3D computed tomography data set in just a few tens of minutes. While a-Si detectors have been proposed for use in imaging neutron beams, this is the first reported implementation of such a detector for neutron imaging.

  14. Proposed experiment to measure the neutron spin-electron angular correlation in polarized neutron beta decay with ultra-cold neutrons

    SciTech Connect

    Seestrom, S.J.; UCN A Collaboration

    1998-12-01

    One area in which the Standard Model can be probed is neutron beta decay. In particular, measurements of angular correlations in neutron beta decay can place constraints on the existence of right-handed currents, the presence of scalar and tensor terms in the weak interaction, and for evidence of Time Reversal Violation, which is expected from the observed violation of CP invariance in kaon decay. A measurement of A, the correlation between the neutron spin and the direction of emission of the electron in neutron decay, can be combined with the neutron lifetime to determine the fundamental vector and axial vector weak coupling constants G{sub A} and G{sub V}. The authors have presented the essential elements of their plans to carry out an A correlation measurement using the UCN source they have constructed at the Manuel Lujan Neutron Scattering Center (MLNSC). Their goal is an initial measurement with an accuracy of about 0.2% of A (which has a value of about {minus}0.114). The count rate expected in the experiment will allow a determination at this statistical accuracy level in a running time of about four months.

  15. Evaluation of the dark signal performance of different SiPM-technologies under irradiation with cold neutrons

    NASA Astrophysics Data System (ADS)

    Durini, Daniel; Degenhardt, Carsten; Rongen, Heinz; Feoktystov, Artem; Schlösser, Mario; Palomino-Razo, Alejandro; Frielinghaus, Henrich; van Waasen, Stefan

    2016-11-01

    In this paper we report the results of the assessment of changes in the dark signal delivered by three silicon photomultiplier (SiPM) detector arrays, fabricated by three different manufacturers, when irradiated with cold neutrons (wavelength λn=5 Å or neutron energy of En=3.27 meV) up to a neutron dose of 6×1012 n/cm2. The dark signals as well as the breakdown voltages (Vbr) of the SiPM detectors were monitored during the irradiation. The system was characterized at room temperature. The analog SiPM detectors, with and without a 1 mm thick Cerium doped 6Li-glass scintillator material located in front of them, were operated using a bias voltage recommended by the respective manufacturer for a proper detector performance. Iout-Vbias measurements, used to determine the breakdown voltage of the devices, were repeated every 30 s during the first hour and every 300 s during the rest of the irradiation time. The digital SiPM detectors were held at the advised bias voltage between the respective breakdown voltage and dark count mappings repeated every 4 min. The measurements were performed on the KWS-1 instrument of the Heinz Maier-Leibnitz Zentrum (MLZ) in Garching, Germany. The two analog and one digital SiPM detector modules under investigation were respectively fabricated by SensL (Ireland), Hamamatsu Photonics (Japan), and Philips Digital Photon Counting (Germany).

  16. T invariance and T-odd asymmetries for the cold-polarized-neutron-induced fission of nonoriented nuclei

    SciTech Connect

    Kadmensky, S. G.; Bunakov, V. E.; Titova, L. V.

    2014-12-15

    It is shown that the coefficients D{sup exp} for all T-odd asymmetries observed experimentally in the cross sections for the reactions of cold-polarized-neutron-induced fission of nonoriented target nuclei (which involves the emission of prescission and evaporated particles) comply in shape and scale with the coefficients D{sup theor} calculated for the analogous asymmetries on the basis of quantum-mechanical nuclear-fission theory for T-invariant Hamiltonians of fissile systems. It is also shown that the asymmetries in question arise upon taking into account the effect of (i) the interference between the fission amplitudes of s- and p-wave resonances of a polarized fissile compound nucleus formed in the aforementioned reactions; (ii) the collective rotation of the compound nucleus in question (this rotation entails a change in the angular distributions of fission fragments and third particles); and (iii) the wriggling vibrations of this compound nucleus in the vicinity of its scission point, which lead to the appearance of high aligned spins of fission fragments, with the result that the emission of neutrons and photons evaporated from these fragments becomes anisotropic. The possible contribution of T-noninvariant interactions to the formation of the T-odd asymmetries under analysis is estimated by using the results obtained in experimentally testing the detailed-balance principle, (P-A) theorem, and T invariance of cross sections for elastic proton-proton and proton-neutron scattering.

  17. Cold neutron tomography of annular coolant flow in a double subchannel model of a boiling water reactor

    NASA Astrophysics Data System (ADS)

    Kickhofel, J. L.; Zboray, R.; Damsohn, M.; Kaestner, A.; Lehmann, E. H.; Prasser, H.-M.

    2011-09-01

    Dryout of the liquid coolant film on fuel pins at the top of boiling water reactor (BWR) cores constitutes the type of heat transfer crisis relevant for the conditions of high void fractions. It is a limiting factor in the thermal power, and therefore the economy, of BWRs. Ongoing research on multiphase annular flow, specifically the liquid film thickness, is fundamental not only to nuclear reactor safety and operation but also to that of evaporators, condensers, and pipelines in a general industrial context. We have performed cold neutron tomography of adiabatic air water annular flow in a scaled up model of the subchannel geometry found in BWR fuel assemblies today. All imaging has been performed at the ICON beamline at the neutron spallation source SINQ at the Paul Scherrer Institut in Switzerland. Neutron tomography is shown to excel in investigating the interactions of air water two phase flows with spacer vanes of different geometry. The high resolution, high contrast measurements provide spatial distributions of the coolant on top of the surfaces of the spacer, including the vanes, and in the subchannel downstream of the spacers.

  18. Computer program /P1-GAS/ calculates the P-0 and P-1 transfer matrices for neutron moderation in a monatomic gas

    NASA Technical Reports Server (NTRS)

    Collier, G.; Gibson, G.

    1968-01-01

    FORTRAN 4 program /P1-GAS/ calculates the P-O and P-1 transfer matrices for neutron moderation in a monatomic gas. The equations used are based on the conditions that there is isotropic scattering in the center-of-mass coordinate system, the scattering cross section is constant, and the target nuclear velocities satisfy a Maxwellian distribution.

  19. Measurement of Parity-Violating y-ray Asymmetry in the Capture of Polarized Cold Neutrons on Protons

    SciTech Connect

    Gericke, M. T.; Bowman, James D; Greene, Geoffrey L; Penttila, Seppo; NPD, Gamma

    2011-01-01

    The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry A{sub {gamma}} with respect to the neutron spin direction of {gamma} rays emitted in the reaction n + p {yields} d + {gamma} using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction between nucleons to be induced by the weak interaction between quarks. A{sub {gamma}} in n + p {yields} d + {gamma} is dominated by a {Delta}I = 1, {sup 3}S{sub 1-}{sup 3}P{sub 1} parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE), with the result A{sub {gamma}} = [-1.2 {+-} 2.1 (stat.) {+-} 0.2 (sys.)] x 10{sup -7}. We also report the first measurement of an upper limit for the parity-allowed left-right asymmetry in this reaction, with the result A{sub {gamma}LR} = [-1.8 {+-} 1.9 (stat.) {+-} 0.2 (sys.)] x 10{sup -7}. In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and LANSCE results. The asymmetry has an estimated size of 5 x 10{sup -8} and the aim of the NPDGamma collaboration is to measure it to 1 x 10{sup -8}. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.

  20. Improving Natural Uranium Utilization By Using Thorium in Low Moderation PWRs - A Preliminary Neutronic Scoping Study

    SciTech Connect

    Gilles Youinou; Ignacio Somoza

    2010-10-01

    The Th-U fuel cycle is not quite self-sustainable when used in water-cooled reactors and with fuel burnups higher than a few thousand of MWd/t characteristic of CANDU reactors operating with a continuous refueling. For the other industrially mature water-cooled reactors (i.e. PWRs and BWRs) it is economically necessary that the fuel has enough reactivity to reach fuel burnups of the order of a few tens of thousand of MWd/t. In this particular case, an additional input of fissile material is necessary to complement the bred fissile U-233. This additional fissile material could be included in the form of Highly Enriched Uranium (HEU) at the fabrication of the Th-U fuel. The objective of this preliminary neutronic scoping study is to determine (1) how much HEU and, consequently, how much natural uranium is necessary in such Th-U fuel cycle with U recycling and (2) how much TRansUranics (TRU=Pu, Np, Am and Cm) are produced. These numbers are then compared with those of a standard UO2 PWR. The thorium reactors considered have a homogeneous hexagonal lattice made up of the same (Th-U)O2 pins. Furthermore, at this point, we are not considering the use of blankets inside or outside the core. The lattice pitch has been varied to estimate the effect of the water-to-fuel volume ratio, and light water as well as heavy water have been considered. For most cases, an average burnup at discharge of 45,000 MWd/t has been considered.

  1. Determining the 6Li doped side of a glass scintillator for ultra cold neutrons

    NASA Astrophysics Data System (ADS)

    Jamieson, Blair; Rebenitsch, Lori Ann

    2015-08-01

    Ultracold neutron (UCN) detectors using two visually very similar, to the microscopic level, pieces of optically contacted cerium doped lithium glasses have been proposed for high rate UCN experiments. The chief difference between the two glass scintillators is that one side is 6Li depleted and the other side 6Li doped. This note outlines a method to determine which side of the glass stack is doped with 6Li using AmBe and 252Cf neutron sources, and a Si surface barrier detector. The method sees an excess of events around the α and triton energies of neutron capture on 6Li when the enriched side is facing the Si surface barrier detector.

  2. Experimental characterization of a prototype secondary spectrometer for vertically scattering multiple energy analysis at cold-neutron triple axis spectrometers

    NASA Astrophysics Data System (ADS)

    Toft-Petersen, Rasmus; Groitl, Felix; Kure, Mathias; Lim, Joshua; Čermák, Petr; Alimov, Svyatoslav; Wilpert, Thomas; Le, Manh Duc; Quintero-Castro, Diana; Niedermayer, Christof; Schneidewind, Astrid; Habicht, Klaus

    2016-09-01

    A thorough experimental characterization of a multiplexing backend with multiple energy analysis on a cold-neutron triple axis spectrometer (cTAS) is presented. The prototype employs two angular segments (2 θ -segments) each containing five vertically scattering analyzers (energy channels), which simultaneously probe an energy transfer range of 2 meV at the corresponding two scattering angles. The feasibility and strength of such a vertically scattering multiple energy analysis setup is clearly demonstrated. It is shown, that the energy resolution near the elastic line is comparable to the energy resolution of a standard cTAS. The dispersion relation of the antiferromagnetic excitations in MnF2 has been mapped out by performing constant energy transfer maps. These results show that the tested setup is virtually spurion free. In addition, focusing effects due to (mis)matching of the instrumental resolution ellipsoid to the excitation branch are clearly evident.

  3. Intracavitary moderator balloon combined with 252Cf brachytherapy and boron neutron capture therapy, improving dosimetry in brain tumour and infiltrations

    PubMed Central

    Brandão, S F

    2015-01-01

    Objective: This article proposes a combination of californium-252 (252Cf) brachytherapy, boron neutron capture therapy (BNCT) and an intracavitary moderator balloon catheter applied to brain tumour and infiltrations. Methods: Dosimetric evaluations were performed on three protocol set-ups: 252Cf brachytherapy combined with BNCT (Cf-BNCT); Cf-BNCT with a balloon catheter filled with light water (LWB) and the same set-up with heavy water (HWB). Results: Cf-BNCT-HWB has presented dosimetric advantages to Cf-BNCT-LWB and Cf-BNCT in infiltrations at 2.0–5.0 cm from the balloon surface. However, Cf-BNCT-LWB has shown superior dosimetry up to 2.0 cm from the balloon surface. Conclusion: Cf-BNCT-HWB and Cf-BNCT-LWB protocols provide a selective dose distribution for brain tumour and infiltrations, mainly further from the 252Cf source, sparing the normal brain tissue. Advances in knowledge: Malignant brain tumours grow rapidly and often spread to adjacent brain tissues, leading to death. Improvements in brain radiation protocols have been continuously achieved; however, brain tumour recurrence is observed in most cases. Cf-BNCT-LWB and Cf-BNCT-HWB represent new modalities for selectively combating brain tumour infiltrations and metastasis. PMID:25927876

  4. Analyses of the reflector tank, cold source, and beam tube cooling for ANS reactor. [Advanced Neutron Source (ANS)

    SciTech Connect

    Marland, S. )

    1992-07-01

    This report describes my work as an intern with Martin Marietta Energy Systems, Inc., in the summer of 1991. I was assigned to the Reactor Technology Engineering Department, working on the Advanced Neutron Source (ANS). My first project was to select and analyze sealing systems for the top of the diverter/reflector tank. This involved investigating various metal seals and calculating the forces necessary to maintain an adequate seal. The force calculations led to an analysis of several bolt patterns and lockring concepts that could be used to maintain a seal on the vessel. Another project involved some pressure vessel stress calculations and the calculation of the center of gravity for the cold source assembly. I also completed some sketches of possible cooling channel patterns for the inner vessel of the cold source. In addition, I worked on some thermal design analyses for the reflector tank and beam tubes, including heat transfer calculations and assisting in Patran and Pthermal analyses. To supplement the ANS work, I worked on other projects. I completed some stress/deflection analyses on several different beams. These analyses were done with the aid of CAASE, a beam-analysis software package. An additional project involved bending analysis on a carbon removal system. This study was done to find the deflection of a complex-shaped beam when loaded with a full waste can.

  5. Semiclassical description of TRI asymmetry in ternary fission induced by cold polarized neutrons

    SciTech Connect

    Bunakov, V. E.; Kadmensky, S. G.

    2011-11-15

    The possibility of semiclassically describing T-even TRI-type asymmetry in ternary fission induced by polarized neutrons is considered on the basis of employing Coriolis interaction that takes into account the coupling of a light charged particle to the collective rotation of a polarized fissile nucleus. It is shown that allowance for this interaction makes it possible to explain qualitatively the magnitudes of two asymmetry effects observed in light-charge-particle emission both within the semiclassical and within the quantum-mechanical approach. The difference in the relative magnitudes and signs of the effects between different target nuclei is associated with the interference contributions to the cross section from neighboring neutron resonances and therefore cannot be explained within the semiclassical approach.

  6. Analyses of thin films and surfaces by cold neutron depth profiling

    NASA Astrophysics Data System (ADS)

    Lamaze, G. P.; Chen-Mayer, H. H.; Soni, K. K.

    2004-11-01

    Neutron depth profiling (NDP) has been employed to examine manufacturing processes and starting materials for several high-technology applications. NDP combines nuclear and atomic physics processes to determine the concentration profile of several light elements in the near surface region (∼1-8 μm) of smooth surfaces. The method is both quantitative and non-destructive. Analyses are performed at the Center for Neutron Research at NIST on samples prepared at Corning Incorporated. Two types of samples have been analyzed: (1) Boron profiles are measured in glasses to determine B loss due to its volatilization during manufacturing. Surface depletion of B is a key characteristic of borosilicate materials for both chemical vapor deposition and conventional melting processes. (2) For lithium niobate, a quantitative measure of Li concentration can differentiate congruent and stoichiometric compositions and any surface depletion in commercial wafers.

  7. Dose distributions in a human head phantom for neutron capture therapy using moderated neutrons from the 2.5 MeV proton-7Li reaction or from fission of 235U

    NASA Astrophysics Data System (ADS)

    Tanaka, Kenichi; Kobayashi, Tooru; Sakurai, Yoshinori; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

    2001-10-01

    The feasibility of neutron capture therapy (NCT) using an accelerator-based neutron source of the 7Li(p,n) reaction produced by 2.5 MeV protons was investigated by comparing the neutron beam tailored by both the Hiroshima University radiological research accelerator (HIRRAC) and the heavy water neutron irradiation facility in the Kyoto University reactor (KUR-HWNIF) from the viewpoint of the contamination dose ratios of the fast neutrons and the gamma rays. These contamination ratios to the boron dose were estimated in a water phantom of 20 cm diameter and 20 cm length to simulate a human head, with experiments by the same techniques for NCT in KUR-HWNIF and/or the simulation calculations by the Monte Carlo N-particle transport code system version 4B (MCNP-4B). It was found that the 7Li(p,n) neutrons produced by 2.5 MeV protons combined with 20, 25 or 30 cm thick D2O moderators of 20 cm diameter could make irradiation fields for NCT with depth-dose characteristics similar to those from the epithermal neutron beam at the KUR-HWNIF.

  8. Large area neutron detector based on Li6 ionization chamber with integrated body-moderator of high density polyethylene

    SciTech Connect

    Ianakiev, Kiril D.; Swinhoe, Martyn T.; Chung, Kiwhan; Makela, Mark F.

    2009-06-30

    A detector was developed and funded by DHS to be a lower cost alternative to 3He detectors. A 6Li foil-lined ionization chamber was prepared with fill gas at one atmosphere and pulse mode operation. The high-density polyethylene (HOPE) body serves also as a neutron moderator. All electrodes, including high voltage bias supply, are hermetically sealed within the plastic slabs.

  9. SNS second target station moderator performance update

    SciTech Connect

    Gallmeier, Franz X.

    2010-03-08

    In its first years of operations of its first target station, the Spallation Neutron Source (SNS) is working towards a facility upgrade by a megawatt-class second target station operated at 20 Hz repetition rate, which is intended to complement the existing ORNL neutron sources, the first SNS target station and the HFIR reactor, with high-intensity cold neutron beams.The first round of optimization calculations converged on larger-volume cylindrical para-hydrogen moderators placed in wing configuration on top and bottom of a flat mercury target, pre-moderated by layers of ambient water and surrounded by beryllium reflector. The metric of these optimization calculations was time-averaged and energy-integrated neutron brightness below 5 meV with the requirement to be able to serve 20 ports with neutrons. A summary of these calculations will be given including lessons learned from the variety of simulated configurations and detailed neutron performance characteristics like spectral intensities, emission time distributions, local variations of moderator brightness at the viewed areas, and sensitivity of the optimization metric to optimized parameters for the most promising configuration.

  10. 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.

  11. Low-level gamma and neutron monitoring based on use of proportional counter filled with 3He in polythene moderator: study of the responses to gamma and neutrons.

    PubMed

    Pszona, S; Bantsar, A; Tulik, P; Wincel, K; Zaręba, B

    2014-10-01

    It has been shown that a proportional counter filled with (3)He placed centrally inside a polythene sphere opens a new possibility for measuring gamma photons and neutrons in the separate pulse-height windows. The responses to gamma and neutrons (in terms of ambient dose equivalent) of the detector assembly consisting of 203-mm polythene sphere with centrally positioned 40-mm diameter (3)He proportional counter have been studied. The response to secondary gammas from capture process in hydrogen has also been studied. The rather preliminary studies indicate that the proposed measuring system has very promising features as an ambient dose equivalent device for mixed gamma-neutron fields.

  12. Residual stress profiling in the ferrite and cementite phases of cold-drawn steel rods by synchrotron X-ray and neutron diffraction

    SciTech Connect

    Martinez-Perez, M.L.; Mompean, F.J.; Ruiz-Hervias, J.; Atienza, J.M.; Elices, M.; Peng Rulin; Buslaps, T.

    2004-10-18

    Residual stress profiles have been measured in the ferrite and cementite phases of a cold-drawn eutectoid steel rod by neutron and synchrotron X-ray diffraction in three orientations (axial, radial and hoop). Neutron diffraction was employed to measure the ferrite stresses, whereas synchrotron radiation was used for ferrite and cementite stresses. Experimental results in the ferrite phase showed excellent agreement between both experimental techniques when gauge volume effects were accounted for. Axial cementite stresses were always tensile, with a maximum value close to 1700 MPa at the rod surface. Radial and hoop cementite stresses were compressive along the diameter of the rod, with a minimum of -1900 MPa at the rod center. A 3D-finite element simulation of the macro residual stresses resulting from cold-drawing showed remarkable agreement with those determined from the experimental measurements in the ferrite and cementite phases.

  13. Equation of state constraints for the cold dense matter inside neutron stars using the cooling tail method

    NASA Astrophysics Data System (ADS)

    Nättilä, J.; Steiner, A. W.; Kajava, J. J. E.; Suleimanov, V. F.; Poutanen, J.

    2016-06-01

    The cooling phase of thermonuclear (type-I) X-ray bursts can be used to constrain neutron star (NS) compactness by comparing the observed cooling tracks of bursts to accurate theoretical atmosphere model calculations. By applying the so-called cooling tail method, where the information from the whole cooling track is used, we constrain the mass, radius, and distance for three different NSs in low-mass X-ray binaries 4U 1702-429, 4U 1724-307, and SAX J1810.8-260. Care is taken to use only the hard state bursts where it is thought that the NS surface alone is emitting. We then use a Markov chain Monte Carlo algorithm within a Bayesian framework to obtain a parameterized equation of state (EoS) of cold dense matter from our initial mass and radius constraints. This allows us to set limits on various nuclear parameters and to constrain an empirical pressure-density relationship for the dense matter. Our predicted EoS results in NS a radius between 10.5-12.8 km (95% confidence limits) for a mass of 1.4 M⊙, depending slightly on the assumed composition. Because of systematic errors and uncertainty in the composition, these results should be interpreted as lower limits for the radius.

  14. The effects of minimal length and maximal momentum on the transition rate of ultra cold neutrons in gravitational field

    NASA Astrophysics Data System (ADS)

    Pedram, Pouria; Nozari, Kourosh; Taheri, S. H.

    2011-03-01

    The existence of a minimum observable length and/or a maximum observable momentum is in agreement with various candidates of quantum gravity such as string theory, loop quantum gravity, doubly special relativity and black hole physics. In this scenario, the Heisenberg uncertainty principle is changed to the so-called Generalized (Gravitational) Uncertainty Principle (GUP) which results in modification of all Hamiltonians in quantum mechanics. In this paper, following a recently proposed GUP which is consistent with quantum gravity theories, we study the quantum mechanical systems in the presence of both a minimum length and a maximum momentum. The generalized Hamiltonian contains two additional terms which are proportional to αp 3 and α 2 p 4 where α ˜ 1 /M Pl c is the GUP parameter. For the case of a quantum bouncer, we solve the generalized Schrödinger equation in the momentum space and find the modified energy eigenvalues and eigenfunctions up to the second-order in GUP parameter. The effects of the GUP on the transition rate of ultra cold neutrons in gravitational spectrometers are discussed finally.

  15. 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.

  16. Cumulative fission yields of short-lived isotopes under natural-abundance-boron-carbide-moderated neutron spectrum

    SciTech Connect

    Finn, Erin C.; Metz, Lori A.; Greenwood, Lawrence R.; Pierson, Bruce; Wittman, Richard S.; Friese, Judah I.; Kephart, Rosara F.

    2015-04-09

    The availability of gamma spectroscopy data on samples containing mixed fission products at short times after irradiation is limited. Due to this limitation, data interpretation methods for gamma spectra of mixed fission product samples, where the individual fission products have not been chemically isolated from interferences, are not well-developed. The limitation is particularly pronounced for fast pooled neutron spectra because of the lack of available fast reactors in the United States. Samples containing the actinide isotopes 233, 235, 238U, 237Np, and 239Pu individually were subjected to a 2$ pulse in the Washington State University 1 MW TRIGA reactor. To achieve a fission-energy neutron spectrum, the spectrum was tailored using a natural abundance boron carbide capsule to absorb neutrons in the thermal and epithermal region of the spectrum. Our tailored neutron spectrum is unique to the WSU reactor facility, consisting of a soft fission spectrum that contains some measurable flux in the resonance region. This results in a neutron spectrum at greater than 0.1 keV with an average energy of 70 keV, similar to fast reactor spectra and approaching that of 235U fission. Unique fission product gamma spectra were collected from 4 minutes to 1 week after fission using single-crystal high purity germanium detectors. Cumulative fission product yields measured in the current work generally agree with published fast pooled fission product yield values from ENDF/B-VII, though a bias was noted for 239Pu. The present work contributes to the compilation of energy-resolved fission product yield nuclear data for nuclear forensic purposes.

  17. Reactions and moderators for an accelerator-based epithermal neutron capture therapy source for cancer treatment. Final report, October 1900--September 1994

    SciTech Connect

    Kunze, J.F.; Brugger, R.M.

    1995-03-01

    The use of boron neutron capture therapy (BNCT) has been considered for nearly 30 years, and been practiced in Japan since the late 1970`s. Early experiments in the USA were generally nonpromising. However, new boron-containing ligand compounds were developed, which would seek out brain tumors. Concentration levels of the order of 30 micrograms of boron per gram of tissue become possible, and interest in the BNCT technique was revived in the USA beginning about 1985, with research reactors as the obvious source of the neutrons for the treatment. However, the limited number of research reactors in the USA (and the world) would mean that this treatment modality would be quite limited. The goals of this work was: (1) Examine as many as possible reactions of charged particles on various targets of an accelerator, and determine those that would give high neutron yields of a convenient energy. (2) Determine, through calculations (using Monte Carlo stochastic computer codes), the best design for a moderator/reflector assembly which would give high thermal flux at a nominal 5 cm depth in the head of a patient, with minimal radiation dose from gamma rays and fast neutrons. (3) Perform a benchmark experiment using a positive ion accelerator. The Li-7(p,n) reaction was chosen for the benchmark, since it was readily available for most accelerators, and was one of the two highest yielding reactions from Task No. 1. Since the University of Missouri has no accelerator, possible accelerators at other universities were investigated, as to availability and cost. A unit having capability in the 2.5 MeV range was desired.

  18. Characterization of moderator assembly dimension for accelerator boron neutron capture therapy of brain tumors using 7Li(p, n) neutrons at proton energy of 2.5 MeV.

    PubMed

    Tanaka, Kenichi; Kobayashi, Tooru; Bengua, Gerard; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

    2006-06-01

    The characteristics of moderator assembly dimension are investigated for the usage of 7Li(p,n) neutrons by 2.5 MeV protons in boron newtron capture therapy (BNCT) of brain tumors in the present study. The indexes checked are treatable protocol depth (TPD), which is the greatest depth of the region satisfying the dose requirements in BNCT protocol, proton current necessary to complete BNCT by 1 h irradiation, and the heat flux deposited in the Li target which should be removed. Assumed materials are D2O for moderator, and mixture of polyethylene and LiF with 50 wt % for collimator. Dose distributions have been computed with MCNP 4B and 4C codes. Consequently, realized TPD does not show a monotonical tendency for the Li target diameter. However, the necessary proton current and heat flux in the Li target decreases as the Li target diameter increases, while this trend reverses at around 10 cm of the Li target diameter for the necessary proton current in the condition of this study. As to the moderator diameter, TPD does not exhibit an apparent dependence. On the other hand, necessary proton current and heat flux decrease as the moderator diameter increases, and this tendency saturates at around 60 cm of the moderator diameter in this study. As to the collimator, increase in inner diameter is suitable from the viewpoint of increasing TPD and decreasing necessary proton current and heat flux, while these indexes do not show apparent difference for collimator inner diameters over 14 cm for the parameters treated here. The practical viewpoint in selecting the parameters of moderator assembly dimension is to increase TPD, within the technically possible condition of accelerated proton current and heat removal from the Li target. In this process, the values for which the resultant characteristics mentioned above saturate or reverse would be important factors. PMID:16872076

  19. Characterization of moderator assembly dimension for accelerator boron neutron capture therapy of brain tumors using {sup 7}Li(p,n) neutrons at proton energy of 2.5 MeV

    SciTech Connect

    Tanaka, Kenichi; Kobayashi, Tooru; Bengua, Gerard; Nakagawa, Yoshinobu; Endo, Satoru; Hoshi, Masaharu

    2006-06-15

    The characteristics of moderator assembly dimension are investigated for the usage of {sup 7}Li(p,n) neutrons by 2.5 MeV protons in boron newtron capture therapy (BNCT) of brain tumors in the present study. The indexes checked are treatable protocol depth (TPD), which is the greatest depth of the region satisfying the dose requirements in BNCT protocol, proton current necessary to complete BNCT by 1 h irradiation, and the heat flux deposited in the Li target which should be removed. Assumed materials are D{sub 2}O for moderator, and mixture of polyethylene and LiF with 50 wt % for collimator. Dose distributions have been computed with MCNP 4B and 4C codes. Consequently, realized TPD does not show a monotonical tendency for the Li target diameter. However, the necessary proton current and heat flux in the Li target decreases as the Li target diameter increases, while this trend reverses at around 10 cm of the Li target diameter for the necessary proton current in the condition of this study. As to the moderator diameter, TPD does not exhibit an apparent dependence. On the other hand, necessary proton current and heat flux decrease as the moderator diameter increases, and this tendency saturates at around 60 cm of the moderator diameter in this study. As to the collimator, increase in inner diameter is suitable from the viewpoint of increasing TPD and decreasing necessary proton current and heat flux, while these indexes do not show apparent difference for collimator inner diameters over 14 cm for the parameters treated here. The practical viewpoint in selecting the parameters of moderator assembly dimension is to increase TPD, within the technically possible condition of accelerated proton current and heat removal from the Li target. In this process, the values for which the resultant characteristics mentioned above saturate or reverse would be important factors.

  20. Cryogenic hydrogen circulation system of neutron source

    SciTech Connect

    Qiu, Y. N.; Hu, Z. J.; Wu, J. H.; Li, Q.; Zhang, Y.; Zhang, P.; Wang, G. P.

    2014-01-29

    Cold neutron sources of reactors and spallation neutron sources are classic high flux neutron sources in operation all over the world. Cryogenic fluids such as supercritical or supercooled hydrogen are commonly selected as a moderator to absorb the nuclear heating from proton beams. By comparing supercritical hydrogen circulation systems and supercooled hydrogen circulation systems, the merits and drawbacks in both systems are summarized. When supercritical hydrogen circulates as the moderator, severe pressure fluctuations caused by temperature changes will occur. The pressure control system used to balance the system pressure, which consists of a heater as an active controller for thermal compensation and an accumulator as a passive volume controller, is preliminarily studied. The results may provide guidelines for design and operation of other cryogenic hydrogen system for neutron sources under construction.

  1. 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)

  2. Experimental verification of equilibrium para-hydrogen levels in hydrogen moderators irradiated by spallation neutrons at J-PARC

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Tatsumoto, H.; Aso, T.; Ohtsu, K.; Takada, H.; Futakawa, M.; Ikeda, Y.

    2016-02-01

    By sampling gaseous hydrogen from a circulating liquid hydrogen loop for Laser Raman spectroscopy, we measured the para-/ortho-hydrogen fractions in liquid hydrogen under neutron irradiation for the first time to identify whether irradiated hydrogen has an elevated ortho-hydrogen fraction. This measurement indicates that para-hydrogen equilibrium persists at 300 kW proton power in the presence of an iron(III) oxide hydroxide [Fe(OH)3] catalyst. The measurements will be repeated as the power at the Japan Proton Accelerator Research Complex (J-PARC) increases to the MW level.

  3. 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.

  4. Neutron detector

    SciTech Connect

    Stephan, Andrew C; Jardret, Vincent D

    2009-04-07

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

  5. 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.

  6. Status Report on the Spallation Neutron Source

    SciTech Connect

    Gabriel, T.A.

    1998-10-12

    The purpose of the Spallation Neutron Source Project (SNS) is to generate low-energy neutrons (ambient [{approximately}200 meV] and cold [{approximately}50 meV]) which can be used by up to 18 neutron beam lines to study the structure and functionality of materials. The neutrons are generated by the spallation process initiated by the interactions of 1-GeV protons with a Hg target. These neutrons are reflected by a Pb reflector and are moderated by 2 water (ambient) and 2 super critical hydrogen (cryogenic) moderators. The pulse structure for the 1 MW proton beam is 60 Hertz and < 0.7 {micro}s/pulse. The facility must be upgradable to higher power levels (2- and 4- MW) with minimal operational interruptions. Although not included in the current funding or baseline, a second target station and associated support structure which will be designed to utilize cold neutrons is also considered to be an upgrade that must be incorporated with minimal impact on operations.

  7. An ultracold neutron source at the NC State University PULSTAR reactor

    NASA Astrophysics Data System (ADS)

    Korobkina, E.; Wehring, B. W.; Hawari, A. I.; Young, A. R.; Huffman, P. R.; Golub, R.; Xu, Y.; Palmquist, G.

    2007-08-01

    Research and development is being completed for an ultracold neutron (UCN) source to be installed at the PULSTAR reactor on the campus of North Carolina State University (NCSU). The objective is to establish a university-based UCN facility with sufficient UCN intensity to allow world-class fundamental and applied research with UCN. To maximize the UCN yield, a solid ortho-D 2 converter will be implemented coupled to two moderators, D 2O at room temperature, to thermalize reactor neutrons, and solid CH 4, to moderate the thermal neutrons to cold-neutron energies. The source assembly will be located in a tank of D 2O in the space previously occupied by the thermal column of the PULSTAR reactor. Neutrons leaving a bare face of the reactor core enter the D 2O tank through a 45×45 cm cross-sectional area void between the reactor core and the D 2O tank. Liquid He will cool the disk-shaped UCN converter to below 5 K. Independently, He gas will cool the cup-shaped CH 4 cold-neutron moderator to an optimum temperature between 20 and 40 K. The UCN will be transported from the converter to experiments by a guide with an inside diameter of 16 cm. Research areas being considered for the PULSTAR UCN source include time-reversal violation in neutron beta decay, neutron lifetime determination, support measurements for a neutron electric-dipole-moment search, and nanoscience applications.

  8. Thermal neutron cross-section libraries for aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Cantargi, F.; Granada, J. R.

    2010-08-01

    Solid phases of aromatic hydrocarbons, such as benzene, toluene, mesitylene and a 3:2 mixture by volume of mesitylene and toluene, were studied as potential moderator materials for a cold neutron source. Existing information on the (lattice) translational and rotational modes of the different molecular species was used to produce generalized frequency spectra; the latter included the internal vibrational modes which in turn involved the analysis of the weights of the different modes. Cross-section libraries were generated in ENDF and ACE formats for hydrogen bounded in those materials at several temperatures, and were used in Monte Carlo calculations to analyze their neutron production compared with standard cryogenic materials like liquid hydrogen and solid methane, the best moderators in terms of cold neutron production. In particular, cross-section libraries were generated at 20 K, which is a typical operating temperature for the majority of the existing cold neutron sources. It was found that those aromatic hydrocarbons produce neutron spectra which are slightly warmer than that of solid methane while presenting a high resistance to radiation, conforming in this way a new and advantageous alternative to traditional moderator materials.

  9. Neutron optics optimization for the SNS EQ-SANS diffractometer

    NASA Astrophysics Data System (ADS)

    Zhao, Jinkui

    2012-03-01

    The extended Q-range small angle neutron scattering (EQ-SANS) diffractometer at the Spallation Neutron Source has recently been completed. Initial commissioning has shown that it has achieved its high intensity, low background, and wide dynamic range design goals. One of the key components that enable these performances is its neutron optics, which are extensively optimized using analytical and Monte Carlo methods. The EQ-SANS optics consist of a curved multichannel beam bender and sections of straight neutron guides on both ends of the bender. The bender and the guide are made of float glass coated with supermirror multilayers. The function of the optics is to ensure low instrument background by avoiding the direct line of sight of the neutron moderator at downstream locations, while transporting thermal and cold neutrons to the sample with maximum efficiency. In this work, the optimization of the EQ-SANS optics is presented.

  10. Measurement of the parity-violating triton emission asymmetry in the reaction {sup 6}Li(n,{alpha}){sup 3}H with polarized cold neutrons

    SciTech Connect

    Vesna, V. A.; Shulgina, E. V.; Gledenov, Yu. M.; Sedyshev, P. V.; Nesvizhevsky, V. V.; Petoukhov, A. K.; Soldner, T.; Zimmer, O.

    2008-03-15

    We describe measurements of the parity-violating (P-odd) triton emission asymmetry coefficient a{sub P-odd} in the {sup 6}Li(n,{alpha}){sup 3}H reaction with polarized cold neutrons. Experiments were carried out at the Petersburg Nuclear Physics Institute (Gatchina, Russia) and at the Institut Laue-Langevin (Grenoble, France). We employed an ionisation chamber in a configuration allowing us to suppress the left-right asymmetry well below 10{sup -8}. An additional test for a false asymmetry due to eventual target impurities (''zero test'') resulted in a{sub 0-test}=(0.0{+-}0.5)x10{sup -8}. As final result of this series of experiments we obtained a{sub P-odd}=(-8.8{+-}2.1)x10{sup -8}.

  11. 1987 Neutron and gamma personnel dosimeter intercomparison study using a D/sub 2/O-moderated /sup 252/Cf source

    SciTech Connect

    Swaja, R.E.; West, L.E.; Sims, C.S.; Welty, T.J.

    1989-05-01

    The thirteenth Personnel Dosimetry Intercomparison Study (i.e., PDIS 13) was conducted during April 1987 as a joint effort by Oak Ridge National Laboratory's (ORNL) Dosimetry Applications Research Group and the Southwest Radiation Calibration Center at the University of Arkansas. A total of 48 organizations (34 from the US and 14 from abroad) participated in PDIS 13. Participants submitted a total of 1,113 neutron and gamma dosimeters for this mixed field study. The dosimeters were transferred by mail and were handled by experimental personnel at ORNL and the University of Arkansas. The type of neutron dosimeter and the percentage of participants submitting that type are as follows: TLD-albedo (49%), direct interaction TLD (31%), CR-39 (17%), film (3%). The type of gamma dosimeter and the percentage of participants submitting that type are as follows: Li/sub 2/B/sub 4/O/sub 7/, alone or in combination with CaSO/sub 4/, (69%), /sup 7/LiF (28%), natural LiF (3%). Radiation exposures in PDIS 13 were limited to 0.5 and 1.5 mSv from /sup 252/Cf moderated by 15-cm of D/sub 2/O. Traditional exposures using the Health Physics Research Reactor (HPRR) were not possible due to the fact that all reactors at ORNL, including the HPRR, were shutdown by order of the Department of Energy at the time the intercomparison was performed. Planned exposures using a /sup 238/PuBe source were negated by a faulty timing mechanism. Based on accuracy and precision, direct interaction TLD dosimeters exhibited the best performance in PDIS 13 neutron measurements. They were followed, in order of best performance, by CR-39, TLD albedo, and film. The Li/sub 2/B/sub 4/O/sub 7/ type TLD dosimeters exhibited the best performance in PDIS 13 gamma measurements. They were followed by natural LiF, /sup 7/LiF, and film. 12 refs., 1 fig., 5 tabs.

  12. 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.

  13. Development of the quantum theory of T-odd asymmetries for prescission and evaporated third particles in ternary nuclear fission induced by cold polarized neutrons

    SciTech Connect

    Kadmensky, S. G.; Bunakov, V. E.; Titova, L. V.; Kadmensky, S. S.

    2011-10-15

    A comparative analysis of the results obtained by experimentally and theoretically studying T-odd asymmetries for various third particles in the true and delayed ternary nuclear fission induced by cold polarized neutrons was performed. It was confirmed that the appearance of these asymmetries was associated with the effect of rotation of a polarized system undergoing fission on the angular distributions of prescission and evaporated third particles with respect to the direction along which the emerging fission fragments flew apart, this effect being determined by the Coriolis interaction of the rotational and the internalmotion of the fissioning system. A quantum-mechanical description of particle motion in a rotating coordinate system was generalized to the case where gamma-ray emission was present. It was shown that the separation of the motions of an axially symmetric fissile system into a rotational and an internal motion was valid in the external region as well, where ternary-fission products had already been formed, if it was considered that the motion of fission fragments was tightly connected with the system symmetry axis, which rotated in the laboratory frame. It was found that the dependence of the fissile-system moment of inertia appearing in the Coriolis interaction Hamiltonian on the distance between the fission fragments flying apart generated an additional phase in the amplitude of the radial distribution of fission fragments. It was shown that this phase might change sizably the contribution of the interference between fission amplitudes of neutron resonances excited in a fissile compound nucleus to the absolute values of T -odd asymmetries, especially for third particles such as neutrons and photons, which interacted only slightly with fission fragments.

  14. Cryogenic moderator simulations : confronting reality.

    SciTech Connect

    Iverson, E. B.

    1999-01-06

    The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a spallation neutron source dedicated to materials research. Its three cryogenic methane moderators provide twelve neutron beams to fourteen instruments and test facilities. This report concerns ongoing activities for benchmarking our Monte Carlo model of the IPNS neutron generation system. This paper concentrates on the techniques (both experimental and calculational) used in such benchmarking activities.

  15. QuBounce: the dynamics of ultra-cold neutrons falling in the gravity potential of the Earth

    NASA Astrophysics Data System (ADS)

    Abele, H.; Jenke, T.; Stadler, D.; Geltenbort, P.

    2009-08-01

    The dynamics of a quantum mechanical wave packet bouncing off a hard surface in the gravitational field of the earth combines quantum theory with aspects of Newtonian mechanics at short distances. We realize such a quantum bouncing ball with ultracold neutrons. By quantum interference, this experiment is sensitive to gravity-like forces at a length scale below 10 μm and can test speculations on large extra dimensions of submillimeter size of space-time or the origin of the cosmological constant in the universe.

  16. NEUTRONIC REACTOR

    DOEpatents

    Fermi, E.; Szilard, L.

    1957-09-24

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

  17. High intensity, pulsed thermal neutron source

    DOEpatents

    Carpenter, J.M.

    1973-12-11

    This invention relates to a high intensity, pulsed thermal neutron source comprising a neutron-producing source which emits pulses of fast neutrons, a moderator block adjacent to the last neutron source, a reflector block which encases the fast neutron source and the moderator block and has a thermal neutron exit port extending therethrough from the moderator block, and a neutron energy- dependent decoupling reflector liner covering the interior surfaces of the thermal neutron exit port and surrounding all surfaces of the moderator block except the surface viewed by the thermal neutron exit port. (Official Gazette)

  18. 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.

  19. Advanced Neutron Sources: Plant Design Requirements

    SciTech Connect

    Not Available

    1990-07-01

    The Advanced Neutron Source (ANS) is a new, world class facility for research using hot, thermal, cold, and ultra-cold neutrons. At the heart of the facility is a 350-MW{sub th}, heavy water cooled and moderated reactor. The reactor is housed in a central reactor building, with supporting equipment located in an adjoining reactor support building. An array of cold neutron guides fans out into a large guide hall, housing about 30 neutron research stations. Office, laboratory, and shop facilities are included to provide a complete users facility. The ANS is scheduled to begin operation at the Oak Ridge National Laboratory at the end of the decade. This Plant Design Requirements document defines the plant-level requirements for the design, construction, and operation of the ANS. This document also defines and provides input to the individual System Design Description (SDD) documents. Together, this Plant Design Requirements document and the set of SDD documents will define and control the baseline configuration of the ANS.

  20. Advanced Neutron Source: Plant Design Requirements

    SciTech Connect

    Not Available

    1990-07-01

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

  1. Design of a target and moderator at the Los Alamos Spallation Radiation Effects Facility (LASREF) as a neutron source for fusion reactor materials development

    SciTech Connect

    Ferguson, P.D.; Mueller, G.E.; Sommer, W.F.; Farnum, E.H.

    1993-10-01

    The LASREF facility is located in the beam stop area at LAMPF. The neutron spectrum is fission-like with the addition of a 3% to 5% component with E > 20 MeV. The present study evaluates the limits on geometry and material selection that will maximize the neutron flux. MCNP and LAHET were used to predict the neutron flux and energy spectrum for a variety of geometries. The problem considers 760 MeV protons incident on tungsten. The resulting neutrons are multiplied in uranium through (n,xn) reactions. Calculations show that a neutron flux greater than 10{sup 19} n/m{sup 2}/s is achievable. The helium to dpa ratio and the transmutation product generation are calculated. These results are compared to expectations for the proposed DEMO fusion reactor and to FFTF.

  2. Demonstration of a single-crystal reflector-filter for enhancing slow neutron beams

    NASA Astrophysics Data System (ADS)

    Muhrer, G.; Schönfeldt, T.; Iverson, E. B.; Mocko, M.; Baxter, D. V.; Hügle, Th.; Gallmeier, F. X.; Klinkby, E. B.

    2016-09-01

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystal reflector-filter at a reflected neutron source and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. This finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.

  3. Hydrogen moderator performance calculations

    SciTech Connect

    Picton, D. J.; Beynon, T. D.; Broome, T. A.

    1997-09-01

    A comparison was made between MCNP calculations and experimental measurements of the neutron spectrum from the liquid hydrogen moderator on ISIS. The calculations were performed for varying ortho/para concentrations, and demonstrated a best fit for 100% para-hydrogen. The agreement between the measured and calculated results was good below 2Å (i.e. for energies above 20 meV) but significant deviations were seen for longer wavelengths. A second study used the MCNP code for a detailed comparison of the time distributions and neutron spectra from poisoned liquid hydrogen and liquid methane moderators. The results indicate that the replacement of a liquid methane moderator with liquid hydrogen, in order to eliminate radiation damage effects, is an option which can be seriously considered. (auth)

  4. Demonstration of a Single-Crystal Reflector-Filter for Enhancing Slow Neutron Beams

    DOE PAGES

    Muhrer, Guenter; Schönfeldt, Troels; Iverson, Erik B.; Mocko, Michal; Baxter, David V.; Hügle, Thomas; Gallmeier, Franz X.; Klinkby, Esben

    2016-06-14

    The cold polycrystalline beryllium reflector-filter concept has been used to enhance the cold neutron emission of cryogenic hydrogen moderators, while suppressing the intermediate wavelength and fast neutron emission at the same time. While suppressing the fast neutron emission is often desired, the suppression of intermediate wavelength neutrons is often unwelcome. It has been hypothesized that replacing the polycrystalline reflector-filter concept with a single-crystal reflector-filter concept would overcome the suppression of intermediate wavelength neutrons and thereby extend the usability of the reflector-filter concept to shorter but still important wavelengths. In this paper we present the first experimental data on a single-crystalmore » reflector-filter and compare experimental results with hypothesized performance. We find that a single-crystal reflector-filter retains the long-wavelength benefit of the polycrystalline reflector-filter, without suffering the same loss of important intermediate wavelength neutrons. Ultimately, this finding extends the applicability of the reflector-filter concept to intermediate wavelengths, and furthermore indicates that the reflector-filter benefits arise from its interaction with fast (background) neutrons, not with intermediate wavelength neutrons of potential interest in many types of neutron scattering.« less

  5. Union of Compact Accelerator-Driven Neutron Sources (UCANS) I & II Neutron applications laboratory for ESS-Bilbao

    NASA Astrophysics Data System (ADS)

    Terrón, S.; Magán, M.; Sordo, F.; Ghiglino, A.; Mart«ınez, F.; Bermejo, F. J.; Perlado, J. M.

    The ESS-Bilbao Accelerator Center site at Lejoa UPV/EHU campus will be provided with a proton accelerator up to 300-400 MeV. In the first construction phase, a beam extraction will be set at the end of the DTL, which will produce a 50 MeV proton beam with an average current of 2.25 mA and 1.5 ms pulses at a frequency of 20 Hz. These beam characteristics allow to configure a low intensity neutron source based on Be (p, n) reactions, which enables experimentation with cold neutrons similar to that of LENS. The total beam power will be 112 kW, so the configuration of the neutron production target will be based on a rotating disk of beryllium slabs facing the beam on one side and a cryogenic methane moderator on the other, with the target-moderator system surrounded by a beryllium reflector. In this paper, first estimates will be presented for thermomechanical conditions of the target cooling scheme, neutron source intensities, and cold neutron pulses.

  6. UCN sources at external beams of thermal neutrons. An example of PIK reactor

    NASA Astrophysics Data System (ADS)

    Lychagin, E. V.; Mityukhlyaev, V. A.; Muzychka, A. Yu.; Nekhaev, G. V.; Nesvizhevsky, V. V.; Onegin, M. S.; Sharapov, E. I.; Strelkov, A. V.

    2016-07-01

    We consider ultracold neutron (UCN) sources based on a new method of UCN production in superfluid helium (4He). The PIK reactor is chosen as a perspective example of application of this idea, which consists of installing 4He UCN source in the beam of thermal or cold neutrons and surrounding the source with moderator-reflector, which plays the role of cold neutron (CN) source feeding the UCN source. CN flux in the source can be several times larger than the incident flux, due to multiple neutron reflections from the moderator-reflector. We show that such a source at the PIK reactor would provide an order of magnitude larger density and production rate than an analogous source at the ILL reactor. We estimate parameters of 4He source with solid methane (CH4) or/and liquid deuterium (D2) moderator-reflector. We show that such a source with CH4 moderator-reflector at the PIK reactor would provide the UCN density of ~1·105 cm-3, and the UCN production rate of ~2·107 s-1. These values are respectively 1000 and 20 times larger than those for the most intense UCN user source. The UCN density in a source with D2 moderator-reflector would reach the value of ~2·105 cm-3, and the UCN production rate would be equal ~8·107 s-1. Installation of such a source in a beam of CNs would slightly increase the density and production rate.

  7. 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)

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Probing Cold Dense Nuclear Matter

    NASA Astrophysics Data System (ADS)

    Subedi, R.; Shneor, R.; Monaghan, P.; Anderson, B. D.; Aniol, K.; Annand, J.; Arrington, J.; Benaoum, H.; Benmokhtar, F.; Boeglin, W.; Chen, J.-P.; Choi, Seonho; Cisbani, E.; Craver, B.; Frullani, S.; Garibaldi, F.; Gilad, S.; Gilman, R.; Glamazdin, O.; Hansen, J.-O.; Higinbotham, D. W.; Holmstrom, T.; Ibrahim, H.; Igarashi, R.; de Jager, C. W.; Jans, E.; Jiang, X.; Kaufman, L. J.; Kelleher, A.; Kolarkar, A.; Kumbartzki, G.; LeRose, J. J.; Lindgren, R.; Liyanage, N.; Margaziotis, D. J.; Markowitz, P.; Marrone, S.; Mazouz, M.; Meekins, D.; Michaels, R.; Moffit, B.; Perdrisat, C. F.; Piasetzky, E.; Potokar, M.; Punjabi, V.; Qiang, Y.; Reinhold, J.; Ron, G.; Rosner, G.; Saha, A.; Sawatzky, B.; Shahinyan, A.; Širca, S.; Slifer, K.; Solvignon, P.; Sulkosky, V.; Urciuoli, G. M.; Voutier, E.; Watson, J. W.; Weinstein, L. B.; Wojtsekhowski, B.; Wood, S.; Zheng, X.-C.; Zhu, L.

    2008-06-01

    The protons and neutrons in a nucleus can form strongly correlated nucleon pairs. Scattering experiments, in which a proton is knocked out of the nucleus with high-momentum transfer and high missing momentum, show that in carbon-12 the neutron-proton pairs are nearly 20 times as prevalent as proton-proton pairs and, by inference, neutron-neutron pairs. This difference between the types of pairs is due to the nature of the strong force and has implications for understanding cold dense nuclear systems such as neutron stars.

  13. Cold Sores

    MedlinePlus

    ... delivered directly to your desktop! more... What Are Cold Sores? Article Chapters What Are Cold Sores? Cold ... January 2012 Previous Next Related Articles: Canker and Cold Sores Aloe Vera May Help Relieve Mouth Sores ...

  14. Opportunities in Inelastic Neutron Scattering at Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Granroth, Garrett E.

    2007-11-01

    The Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) are the two world class neutron scattering user facilities located at Oak Ridge National Laboratory. Inelastic scattering instruments designed to optimally utilize their source are either in, or will soon enter, the user program. The HFIR has three thermal and plans for two cold, neutron triple axis spectrometers in the user program. These instruments examine localized regions of Q and φ space with tunable resolution. The spectrometers at the SNS cover broad ranges of Q and φ space. The BASIS instrument, in the user program, uses near backscattering analyzer crystals to provide 3μeV φ resolution. The ARCS thermal to epithermal neutron spectrometer is in commissioning and the Cold Neutron Chopper Spectrometer will enter commissioning soon. These instruments provide moderate, tunable resolution, and detector coverage out to 140^o. The SEQUOIA spectrometer, complete in 2008, is the fine resolution complement of ARCS. The finest resolution is provided by the Spin-Echo spectrometer; complete in 2009. The HYSPEC spectrometer, available in 2011, will provide polarized capabilities and optimized flux for neutrons of thermal energies. Finally, the Vision chemical spectrometer will use crystal analyzers to access φ in the epithermal range. These instruments, along with representative science to be performed on each, will be presented.

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

    SciTech Connect

    Mocko, Michal; Muhrer, Guenter; Daemen, Luke L; Kelsey, Charles T; Duran, Michael A; Tovesson, Fredrik K

    2010-01-01

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

  16. High-energy and thermal-neutron imaging and modeling with an amorphous silicon flat-panel detector.

    PubMed

    Claytor, Thomas N; Taddeucci, Terry N; Hills, Charles R; Summa, Deborah A; Davis, Anthony W; McDonald, Thomas E; Schwab, Mark J

    2004-10-01

    The Los Alamos Neutron Science Center (LANSCE) operates two spallation neutron sources dedicated to research in materials science, condensed-matter physics, and fundamental and applied nuclear physics. Prior to 1995, all thermal neutron radiography at Los Alamos was done on a beam port attached to the Omega West reactor, a small 8MW research reactor used primarily for radioisotope production and prompt and delayed neutron activation analysis. After the closure of this facility, two largely independent radiography development efforts were begun at LANSCE using moderated cold and thermal neutrons from the Target-1 source and high-energy neutrons from the Target-4 source. Investigations with cold and thermal neutrons employed a neutron converter and film, a scintillation screen and CCD camera system, and a new high-resolution amorphous silicon (a-Si) flat-panel detector system. Recent work with high-energy neutrons (En > 1 MeV) has involved storage-phosphor image plates. Some comparison high-energy images were obtained with both image plates and the a-Si panel and showed equivalent image quality for approximately equal exposure times. PMID:15246402

  17. Advanced Neutron Source: Plant Design Requirements. Revision 4

    SciTech Connect

    Not Available

    1990-07-01

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

  18. Experimental Simulation of Boiling Phenomena with a Cylindrical Annulus Moderator Cell

    SciTech Connect

    Lee, C.H.; Lee, D.J.; Chan, Y.K.; Chang, C.J.

    2002-07-01

    The improvement and utilization promotion project of the Taiwan Research Reactor (TRR-II) has been carried out at the Institute of Nuclear Energy Research (INER). The Cold Neutron Source (CNS) with a two-phase thermosyphon will be installed in the heavy water reactor. The hydrogen cold loop consists of a cylindrical moderator cell, a single transfer tube, and a condenser. A cylindrical annulus moderator cell consists of the outer shell and the inner shell of which bottom part is open. A series of mockup tests were performed by using the full-scale mock-up test facility and Freon-11 as a working fluid. The test results show that the inner shell contains only vapor and the outer shell contains boiling liquid for simulating the TRR-II CNS in the full power operations. The liquid level in the outer shell is stable without producing a sudden bubbling against the increase of 30% power. (authors)

  19. 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.

  20. Cold Stress

    MedlinePlus

    ... be at risk of cold stress. Extreme cold weather is a dangerous situation that can bring on ... the country. In regions relatively unaccustomed to winter weather, near freezing temperatures are considered factors for cold ...

  1. Common Cold

    MedlinePlus

    ... nose, coughing - everyone knows the symptoms of the common cold. It is probably the most common illness. In ... avoid colds. There is no cure for the common cold. For relief, try Getting plenty of rest Drinking ...

  2. 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)

  3. Precise determination of the deuteron spin structure at low to moderate Q2 with CLAS and extraction of the neutron contribution

    NASA Astrophysics Data System (ADS)

    Guler, N.; Fersch, R. G.; Kuhn, S. E.; Bosted, P.; Griffioen, K. A.; Keith, C.; Minehart, R.; Prok, Y.; Adhikari, K. P.; Adikaram, D.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crabb, D.; Crede, V.; D'Angelo, A.; Dashyan, N.; Deur, A.; Djalali, C.; Dodge, G. E.; Dupre, R.; Alaoui, A. El; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Garillon, B.; Garçon, M.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gothe, R. W.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Harrison, N.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Joosten, S.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Kubarovsky, V.; Kuleshov, S. V.; Livingston, K.; Lu, H. Y.; Mayer, M.; MacGregor, I. J. D.; McKinnon, B.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Net, L. A.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Simonyan, A.; Skorodumina, Iu.; Sokhan, D.; Sparveris, N.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Tian, Ye; Tkachenko, S.; Ungaro, M.; Voutier, E.; Walford, N. K.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.; CLAS Collaboration

    2015-11-01

    We present the final results for the deuteron spin structure functions obtained from the full data set collected in 2000-2001 with Jefferson Lab's continuous electron beam accelerator facility (CEBAF) using the CEBAF large acceptance spectrometer (CLAS). Polarized electrons with energies of 1.6, 2.5, 4.2, and 5.8 GeV were scattered from deuteron (15ND3 ) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double-spin asymmetry, the virtual photon absorption asymmetry A1d and the polarized structure function g1d were extracted over a wide kinematic range (0.05 GeV2neutron, which are so far unknown in the resonance region, W <2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations, as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x , a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the operator product expansion.

  4. Precise determination of the deuteron spin structure at low to moderate Q2 with CLAS and extraction of the neutron contribution

    DOE PAGES

    Guler, N.; Fersch, R. G.; Kuhn, S. E.; Bosted, P.; Griffioen, K. A.; Keith, C.; Minehart, R.; Prok, Y.; Adhikari, K. P.; Adikaram, D.; et al

    2015-11-02

    In this study, we present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron (15ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry Ad1 and the polarized structure function gd1 were extracted over a wide kinematic range (0.05 GeV2 < Q2 < 5 GeV2 and 0.9 GeV < W < 3 GeV). We use an unfolding procedure andmore » a parametrization of the corresponding proton results to extract from these data the polarized structure functions An1 and g1n of the (bound) neutron, which are so far unknown in the resonance region, W < 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.« less

  5. Upgrades to the ultracold neutron source at the Los Alamos Neutron Science Center

    NASA Astrophysics Data System (ADS)

    Pattie, Robert; LANL-nEDM Collaboration

    2015-10-01

    The spallation-driven solid deutrium-based ultracold neutron (UCN) source at the 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 increase the UCN output is underway. The ultimate goal is to provide a density of 100 UCN/cc or greater in the nEDM storage cell. This upgrade includes redesign of the cold neutron moderator and UCN converter geometries, improved coupling and 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 results of the MCNP and UCN transport simulations that led to the new design, which will be installed spring 2016, and UCN guide tests performed at LANSCE and the Institut Laue-Langevin to study the UCN transport properties of a new nickel-based guide coating.

  6. Impact of the High Flux Isotope Reactor HEU to LEU Fuel Conversion on Cold Source Nuclear Heat Generation Rates

    SciTech Connect

    Chandler, David

    2014-03-01

    Under the sponsorship of the US Department of Energy National Nuclear Security Administration, staff members at the Oak Ridge National Laboratory have been conducting studies to determine whether the High Flux Isotope Reactor (HFIR) can be converted from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel. As part of these ongoing studies, an assessment of the impact that the HEU to LEU fuel conversion has on the nuclear heat generation rates in regions of the HFIR cold source system and its moderator vessel was performed and is documented in this report. Silicon production rates in the cold source aluminum regions and few-group neutron fluxes in the cold source moderator were also estimated. Neutronics calculations were performed with the Monte Carlo N-Particle code to determine the nuclear heat generation rates in regions of the HFIR cold source and its vessel for the HEU core operating at a full reactor power (FP) of 85 MW(t) and the reference LEU core operating at an FP of 100 MW(t). Calculations were performed with beginning-of-cycle (BOC) and end-of-cycle (EOC) conditions to bound typical irradiation conditions. Average specific BOC heat generation rates of 12.76 and 12.92 W/g, respectively, were calculated for the hemispherical region of the cold source liquid hydrogen (LH2) for the HEU and LEU cores, and EOC heat generation rates of 13.25 and 12.86 W/g, respectively, were calculated for the HEU and LEU cores. Thus, the greatest heat generation rates were calculated for the EOC HEU core, and it is concluded that the conversion from HEU to LEU fuel and the resulting increase of FP from 85 MW to 100 MW will not impact the ability of the heat removal equipment to remove the heat deposited in the cold source system. Silicon production rates in the cold source aluminum regions are estimated to be about 12.0% greater at BOC and 2.7% greater at EOC for the LEU core in comparison to the HEU core. Silicon is aluminum s major transmutation product and

  7. The advanced neutron source reactor: An overview

    SciTech Connect

    West, C.D.

    1990-01-01

    The Advanced Neutron Source (ANS) will be a new user facility for all kinds of neutron research, including neutron scattering, materials testing, materials analysis, isotope production and nuclear physics experiments. The centerpiece of the facility is to be the world's highest flux beam reactor. There will be beams of hot, cold and thermal neutrons for more than 40 simultaneous scattering and nuclear physics experiments. In addition, there will be irradiation positions and rabbit tubes for in-pile experiments, testing and isotopes production (including transuranium isotopes). To reduce technical risks and to minimize safety issues, the reactor design is based on technology already employed in existing research reactors. The fuel elements are annular assemblies of aluminum clad involute fuel plates, similar to the design of the High Flux Isotope Reactor (HFIR) at Oak Ridge and the Institut Laue-Langevin (ILL) Reactor in Grenoble. As is common with many other research reactors, the core is cooled, moderated and reflected by heavy water. The preferred fuel is U{sub 3}Si{sub 2} - a high-density fuel form developed by Argonne National Laboratory and Babcock and Wilcox that has been extensively tested in reactors in the United States, Europe and Japan. 7 figs., 2 tabs.

  8. Corrigendum to "Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor" [Nuclear Instruments and Methods in Physics Research A 729 (2013) 220-226

    NASA Astrophysics Data System (ADS)

    Le, M. D.; Quintero-Castro, D. L.; Toft-Petersen, R.; Groitl, F.; Skoulatos, M.; Rule, K. C.; Habicht, K.

    2014-12-01

    It has been recently brought to our attention that there are two errors in Fig. 2 of the article, "Gains from the upgrade of the cold neutron triple-axis spectrometer FLEXX at the BER-II reactor", published in volume 729, pages 220-226 of this journal in 2013. Firstly, the right hand vertical axis labels should read "Integrated Flux (107 n cm-2 s-1)" rather than "Integrated Flux (108 n cm-2s-1)". Secondly, the implicit comparison between the integrated peak area of a monochromator rocking scan and the neutron flux measured by gold foil activation in the figure is invalid. Rather, the peak height should be used as shown in corrected Fig. 1. These corrections, however, do not invalidate the conclusions of the paper, which is that up to an order of magnitude gain in count rate has been achieved from the upgrade of the primary spectrometer of the FLEXX instrument in Berlin. The authors would like to apologize for any inconvenience caused.

  9. Modern Techniques for Inelastic Thermal Neutron Scattering Analysis

    NASA Astrophysics Data System (ADS)

    Hawari, A. I.

    2014-04-01

    A predictive approach based on ab initio quantum mechanics and/or classical molecular dynamics simulations has been formulated to calculate the scattering law, S(κ⇀,ω), and the thermal neutron scattering cross sections of materials. In principle, these atomistic methods make it possible to generate the inelastic thermal neutron scattering cross sections of any material and to accurately reflect the physical conditions of the medium (i.e, temperature, pressure, etc.). In addition, the generated cross sections are free from assumptions such as the incoherent approximation of scattering theory and, in the case of solids, crystalline perfection. As a result, new and improved thermal neutron scattering data libraries have been generated for a variety of materials. Among these are materials used for reactor moderators and reflectors such as reactor-grade graphite and beryllium (including the coherent inelastic scattering component), silicon carbide, cold neutron media such as solid methane, and neutron beam filters such as sapphire and bismuth. Consequently, it is anticipated that the above approach will play a major role in providing the nuclear science and engineering community with its needs of thermal neutron scattering data especially when considering new materials where experimental information may be scarce or nonexistent.

  10. Electrochemical cold fusion trials at IPP garching

    NASA Astrophysics Data System (ADS)

    Bosch, H. S.; Wurden, G. A.; Gernhardt, J.; Karger, F.; Perchermeier, J.

    1990-06-01

    Following the report of Fleischmann and Pons,(1) we (The Bavarian Bubble Bottle Team) have attempted to reproduce their claims of cold nuclear fusion, and failed. We note that our measurements would not be able to detect neutrons at the level of Jones et al.(2) Three electrolytic cell experiments were conducted using palladium cathodes and Platinum anodes, in a 0.1-Molar solution of LiD in heavy water, without any signs of neutrons, tritium, or gammas above backgrounds, and within ±0.3 watt accuracy calorimetry, no excess heating. Excess heating at the levels of F&P would have been easily detected, if present. Intrinsic tritium, differing from each D2O bottle tested, was however observed. The longest duration experiment ran for 21 days, and was an attempt to duplicate the large “melting incident” of F&P. This was terminated on April 28, 1989, by throwing the vacuum-cast 22 gram, deuterium-loaded palladium cathode directly into liquid nitrogen, immediately next to a bare BF3 counter (backed by 25 cm of moderator), in order to attempt one of the Italian ENEA neutron production variants. No neutrons above backgrounds were seen, while counting for 1 hour, and also none while the piece warmed to room temperature over the next hour. Post-mortem analysis of the darkened, hardened Pd piece showed large crystal grains (up to 2 mm × 2 mm), and continuing evolution of gas bubbles at the grain boundaries even days after the experiment was ended. eight weeks after loading, the catalytically-active palladium piece continued to create heavy water (with exposure to oxygen in the air).

  11. Neutronic reactor thermal shield

    DOEpatents

    Wende, Charles W. J.

    1976-06-15

    1. The method of operating a water-cooled neutronic reactor having a graphite moderator which comprises flowing a gaseous mixture of carbon dioxide and helium, in which the helium comprises 40-60 volume percent of the mixture, in contact with the graphite moderator.

  12. Coulomb and even-odd effects in cold and super-asymmetric fragmentation for thermal neutron induced fission of 235U

    NASA Astrophysics Data System (ADS)

    Montoya, M.

    2016-07-01

    Even-odd effects of the maximal total kinetic energy (Kmax) as a function of charge (Z) and mass (A) of fragments from thermal neutron induced fission of actinides are questioned by other authors. In this work, visiting old results on thermal neutron induced fission of 235U, those even-odd effects are reconfirmed. The cases seeming to contradict even-odd effects are interpreted with the Coulomb effect hypothesis. According to Coulomb effect hypothesis, Kmax is equal to the Coulomb interaction energy of the most compact scission configuration. As a consequence, between two isobaric charge splits with similar Q-values, the more asymmetrical one will get the more compact scission configuration and then it will reach the higher Kmax-value. In some cases, the more asymmetrical charge split corresponds, by coincidence, to an odd charge split; consequently its higher Kmax-value may be misinterpreted as anti-even-odd effect. Another experimental result reported in the literature is the increasing of even-odd effects on charge distribution on the more asymmetrical fragmentations region. In this region, the difference between Kmax and Q-values increases with asymmetry, which means that the corresponding scission configuration needs higher total deformation energy to occur. Higher deformation energy of the fragments implies lower free energy to break nucleon pairs. Consequently, in the asymmetric fragmentation region, the even-odd effects of the distribution of proton number and neutron number must increase with asymmetry.

  13. Graphite moderated (252)Cf source.

    PubMed

    Sajo-Bohus, Laszlo; Barros, Haydn; Greaves, Eduardo D; Vega-Carrillo, Hector Rene

    2015-06-01

    The Thorium molten-salt reactor is an attractive and affordable nuclear power option for developing countries with insufficient infrastructure and limited technological capability. In the aim of personnel training and experience gathering at the Universidad Simon Bolivar there is in progress a project of developing a subcritical thorium liquid-fuel reactor. The neutron source to run this subcritical reactor is a (252)Cf source and the reactor will use high-purity graphite as moderator. Using the MCNP5 code the neutron spectra of the (252)Cf in the center of the graphite moderator has been estimated along the channel where the liquid thorium salt will be inserted; also the ambient dose equivalent due to the source has been determined around the moderator.

  14. Common cold

    MedlinePlus

    ... been tried for colds, such as vitamin C, zinc supplements, and echinacea. Talk to your health care ... nih.gov/pubmed/22962927 . Singh M, Das RR. Zinc for the common cold. Cochrane Database of Systematic ...

  15. Common Cold

    MedlinePlus

    ... News & Events Volunteer NIAID > Health & Research Topics > Common Cold Skip Website Tools Website Tools Print this page ... Help people who are suffering from the common cold by volunteering for NIAID clinical studies on ClinicalTrials. ...

  16. NEUTRONIC REACTOR SYSTEM

    DOEpatents

    Goett, J.J.

    1961-01-24

    A system is described which includes a neutronic reactor containing a dispersion of fissionable material in a liquid moderator as fuel and a conveyor to which a portion of the dispersion may be passed and wherein the self heat of the slurry evaporates the moderator. Means are provided for condensing the liquid moderator and returning it to the reactor and for conveying the dried fissionable material away from the reactor.

  17. Slow neutron leakage spectra from spallation neutron sources

    SciTech Connect

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

    1980-02-01

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

  18. Neutronics Benchmarks for the Utilization of Mixed-Oxide Fuel: Joint U.S./ Russian Progress Report for Fiscal Year 1997, Volume 4, Part 8 - Neutron Poison Plates in Assemblies Containing Homogeneous Mixtures of Polystyrene-Moderated Plutonium and Uranium Oxides

    SciTech Connect

    Yavuz, M.

    1999-05-01

    In the 1970s at the Battelle Pacific Northwest Laboratory (PNL), a series of critical experiments using a remotely operated Split-Table Machine was performed with homogeneous mixtures of (Pu-U)O{sub 2}-polystyrene fuels in the form of square compacts having different heights. The experiments determined the critical geometric configurations of MOX fuel assemblies with and without neutron poison plates. With respect to PuO{sub 2} content and moderation [H/(Pu+U)atomic] ratio (MR), two different homogeneous (Pu-U) O{sub 2}-polystyrene mixtures were considered: Mixture (1) 14.62 wt% PuO{sub 2} with 30.6 MR, and Mixture (2) 30.3 wt% PuO{sub 2} with 2.8 MR. In all mixtures, the uranium was depleted to about O.151 wt% U{sup 235}. Assemblies contained copper, copper-cadmium or aluminum neutron poison plates having thicknesses up to {approximately}2.5 cm. This evaluation contains 22 experiments for Mixture 1, and 10 for Mixture 2 compacts. For Mixture 1, there are 10 configurations with copper plates, 6 with aluminum, and 5 with copper-cadmium. One experiment contained no poison plate. For Mixture 2 compacts, there are 3 configurations with copper, 3 with aluminum, and 3 with copper-cadmium poison plates. One experiment contained no poison plate.

  19. Benchmarking simulation methods for methane moderators

    SciTech Connect

    Iverson, Erik B.; Carpenter, J. M.

    1997-01-01

    The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a spallation neutron source dedicated to materials research. Its three cryogenic methane moderators provide twelve neutron beams to fourteen instruments and test facilities. IPNS has begun a program to enhance the effectiveness of its target, reflector, and moderator system. This program will involve the examination of many different potential system modifications and their various interactions. The first component of such a task is the assessment of the current performance of the target, reflector, and moderator system, and the verification of the computational model used to evaluate the system. To that end, we have developed a Monte Carlo model of the IPNS neutron generation system as currently configured, and are in the process of validating that model with corresponding measurements. This paper describes the Monte Carlo model and analysis, as well as some of the experimental comparisons we use to validate our model. (auth)

  20. 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.

  1. ORNL contributions to the Advanced Neutron Source (ANS) Project for October 1986-March 1987

    SciTech Connect

    Selby, D.L.; Harrington, R.M.; Peretz, F.J.

    1987-11-01

    The Advanced Neutron Source (ANS) Facility - formerly called the Center for Neutron Research - will provide the world's best facilities for the study of neutron scattering. The ANS high power density reactor will be fueled with uranium silicide and cooled, moderated, and reflected by D/sub 2/O. Peak neutron fluxes in the reflector are expected to be 5 to 10 x 10/sup 19/ neutrons per square meter with a power level between 270 MW and 300 MW. This report describes the status of technical work at ORNL on the ANS Project during the first half of FY 1987. The scope of this report includes Research and Development Tasks; Safety Tasks; Conceptual Design Tasks; and Project Support. The last two areas were only initiated as separate activities during this reporting period. Technical highlights include a better understanding of the relationship among neutron flux, core power, and core volume; preconceptual design work on a cold source for use in a very high gamma and neutron flux environment; identification of the major applicable safety rules and guidelines; and establishment of initial functional objectives for the containment structure.

  2. Dose-equivalent neutron dosimeter

    DOEpatents

    Griffith, R.V.; Hankins, D.E.; Tomasino, L.; Gomaa, M.A.M.

    1981-01-07

    A neutron dosimeter is disclosed which provides a single measurement 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 contaning 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.

  3. Cold injuries.

    PubMed

    Kruse, R J

    1995-01-01

    There are two categories of cold injury. The first is hypothermia, which is a systemic injury to cold, and the second is frostbite, which is a local injury. Throughout history, entire armies, from George Washington to the Germans on the Russian Front in World War II, have fallen prey to prolonged cold exposure. Cold injury is common and can occur in all seasons if ambient temperature is lower than the core body temperature. In the 1985 Boston Marathon, even though it was 76 degrees and sunny, there were 75 runners treated for hypothermia. In general, humans adapt poorly to cold exposure. Children are at particular risk because of their relatively greater surface area/body mass ratio, causing them to cool even more rapidly than adults. Because of this, the human's best defense against cold injury is to limit his/her exposure to cold and to dress appropriately. If cold injury has occurred and is mild, often simple passive rewarming such as dry blankets and a warm room are sufficient treatment.

  4. European Neutrons form Parasitic Research to Global Strategy: Realizing Plans for a Transnational European Spallation Source in the Wake of the Cold War

    NASA Astrophysics Data System (ADS)

    Kaiserfeld, Thomas

    2016-03-01

    Studies of Big Science have early on focused on instrumentation and scientific co-operation in large organizations, later on to take into account symbolic values and specific research styles while more recently also involving the relevance of commercial interests and economic development as well as the assimilation of research traditions. In accordance with these transformed practices, this presentation will analyze how an organization with the purpose of realizing a Big-Science facility, The European Spallation Source, has successfully managed to present the project as relevant to different national and international policy-makers, to the community of European neutron researchers as well as to different industrial interests. All this has been achieved in a research-policy environment, which has been the subject to drastic transformations, from calls to engage researchers from the former eastern bloc in the early 1990s via competition with American and Asian researchers at the turn of the century 2000 to intensified demands on business applications. During this process, there has also been fierce competition between different potential sites in the U.K., Germany, Spain, Hungary and Sweden, not once, but twice. The project has in addition been plagued by withdrawals of key actors as well as challenging problems in the field of spallation-source construction. Nevertheless, the European Spallation Source has survived from the early 1990s until today, now initiating the construction process at Lund in southern Sweden. In this presentation, the different measures taken and arguments raised by the European Spallation Source project in order to realize the facility will be analysed. Especially the different designs of the European Spallation Source will be analysed as responses to external demands and threats.

  5. NEUTRONIC REACTOR CONTROL ELEMENT

    DOEpatents

    Newson, H.W.

    1960-09-13

    A novel composite neutronic reactor control element is offered. The element comprises a multiplicity of sections arranged in end-to-end relationship, each of the sections having a markedly different neutron-reactive characteristic. For example, a three-section control element could contain absorber, moderator, and fuel sections. By moving such an element longitudinally through a reactor core, reactivity is decreased by the absorber, increased slightly by the moderator, or increased substantially by the fuel. Thus, control over a wide reactivity range is provided.

  6. 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)

  7. 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.

  8. 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.

  9. Neutron-chamber detectors and applications

    SciTech Connect

    Fehlau, P.E.; Atwater, H.F.; Coop, K.L.

    1990-01-01

    Detector applications in Nuclear Safeguards and Waste Management have included measuring neutrons from fission and (alpha,n) reactions with well-moderated neutron proportional counters, often embedded in a slab of polyethylene. Other less-moderated geometries are useful for detecting both bare and moderated fission-source neutrons with good efficiency. The neutron chamber is an undermoderated detector design comprising a large, hollow, polyethylene-walled chamber containing one or more proportional counters. Neutron-chamber detectors are relatively inexpensive; can have large apertures, usually through a thin chamber wall; and offer very good detection efficiency per dollar. Neutron-chamber detectors have also been used for monitoring vehicles and for assaying large crates of transuranic waste. Our Monte Carlo calculations for a new application (monitoring low-density waste for concealed plutonium) illustrate the advantages of the hollow-chamber design for detecting moderated fission sources. 9 refs., 6 figs., 2 tabs.

  10. Cold intolerance

    MedlinePlus

    Some causes of cold intolerance are: Anemia Anorexia nervosa Blood vessel problems, such as Raynaud phenomenon Chronic severe illness General poor health Underactive thyroid ( hypothyroidism ) Problem with the hypothalamus (a part ...

  11. Visualization of water usage and photosynthetic activity of street trees exposed to 2 ppm of SO 2—A combined evaluation by cold neutron and chlorophyll fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Matsushima, U.; Kardjilov, N.; Hilger, A.; Manke, I.; Shono, H.; Herppich, W. B.

    2009-06-01

    Photosynthetic efficacy and auto-exhaust-fume resistance of street trees were evaluated by cold neutron radiography (CNR) with D 2O tracer and chlorophyll fluorescence (CF) imaging. With these techniques, information on the responses of water usage and photosynthetic activity of plants exposed to simulate toxic auto-exhaust fumes (2 ppm SO 2 in air) were obtained. Branches of hibiscus trees were detached, placed into a tub with aerated water and used for the experiments after rooting. A CF image was taken before SO 2 was applied for 1 h. During the experiment, CNR and CF imaging were conduced. H 2O and D 2O in the plant container were exchanged every 30 min to observe water uptake. D 2O tracer clearly showed water uptake into the hibiscus stem during each treatment. When the atmosphere was changed from simulated auto-exhaust fumes to normal air again, the amount of D 2O and, hence, water uptake increased. CF imaging was well suited to evaluate the effects of SO 2 as simulated toxic auto-exhaust fumes on plants. The maximum photochemical efficiency ( Fv/ Fm), a sensitive indicator of the efficacy and the integrity of plants' photosynthesis, immediately dropped by 30% after supplying the simulated auto-exhaust fumes. This indicates that toxic auto-exhaust fumes negatively affected the photosynthetic activity of hibiscus leaves. Simultaneous CNR and CF imaging successfully visualized variations of photosynthetic activity and water uptake in the sample. Thus, this combination method was effective to non-destructive analyze the physiological status of plants.

  12. 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.

  13. Neutron capture therapies

    DOEpatents

    Yanch, Jacquelyn C.; Shefer, Ruth E.; Klinkowstein, Robert E.

    1999-01-01

    In one embodiment there is provided an application of the .sup.10 B(n,.alpha.).sup.7 Li nuclear reaction or other neutron capture reactions for the treatment of rheumatoid arthritis. This application, called Boron Neutron Capture Synovectomy (BNCS), requires substantially altered demands on neutron beam design than for instance treatment of deep seated tumors. Considerations for neutron beam design for the treatment of arthritic joints via BNCS are provided for, and comparisons with the design requirements for Boron Neutron Capture Therapy (BNCT) of tumors are made. In addition, exemplary moderator/reflector assemblies are provided which produce intense, high-quality neutron beams based on (p,n) accelerator-based reactions. In another embodiment there is provided the use of deuteron-based charged particle reactions to be used as sources for epithermal or thermal neutron beams for neutron capture therapies. Many d,n reactions (e.g. using deuterium, tritium or beryllium targets) are very prolific at relatively low deuteron energies.

  14. Consideration of a ultracold neutron source in two-dimensional cylindrical geometry by taking simulated boundaries

    NASA Astrophysics Data System (ADS)

    Gheisari, R.; Firoozabadi, M. M.; Mohammadi, H.

    2014-01-01

    A new idea to calculate ultracold neutron (UCN) production by using Monte Carlo simulation method to calculate the cold neutron (CN) flux and an analytical approach to calculate the UCN production from the simulated CN flux was given. A super-thermal source (UCN source) was modeled based on an arrangement of D2O and solid D2 (sD2). The D2O was investigated as the neutron moderator, and sD2 as the converter. In order to determine the required parameters, a two-dimensional (2D) neutron balance equation written in Matlab was combined with the MCNPX simulation code. The 2D neutron-transport equation in cylindrical (ρ - z) geometry was considered for 330 neutron energy groups in the sD2. The 2D balance equation for UCN and CN was solved using simulated CN flux as boundary value. The UCN source dimensions were calculated for the development of the next UCN source. In the optimal condition, the UCN flux and the UCN production rate (averaged over the sD2 volume) equal to 6.79 × 106 cm-2s-1 and 2.20 ×105 cm-3s-1, respectively.

  15. Consideration of a ultracold neutron source in two-dimensional cylindrical geometry by taking simulated boundaries

    SciTech Connect

    Gheisari, R.; Firoozabadi, M. M.; Mohammadi, H.

    2014-01-15

    A new idea to calculate ultracold neutron (UCN) production by using Monte Carlo simulation method to calculate the cold neutron (CN) flux and an analytical approach to calculate the UCN production from the simulated CN flux was given. A super-thermal source (UCN source) was modeled based on an arrangement of D{sub 2}O and solid D{sub 2} (sD{sub 2}). The D{sub 2}O was investigated as the neutron moderator, and sD{sub 2} as the converter. In order to determine the required parameters, a two-dimensional (2D) neutron balance equation written in Matlab was combined with the MCNPX simulation code. The 2D neutron-transport equation in cylindrical (ρ − z) geometry was considered for 330 neutron energy groups in the sD{sub 2}. The 2D balance equation for UCN and CN was solved using simulated CN flux as boundary value. The UCN source dimensions were calculated for the development of the next UCN source. In the optimal condition, the UCN flux and the UCN production rate (averaged over the sD{sub 2} volume) equal to 6.79 × 10{sup 6} cm{sup −2}s{sup −1} and 2.20 ×10{sup 5} cm{sup −3}s{sup −1}, respectively.

  16. MODFLOW 2. 0: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F. . Dept. of Nuclear Engineering); Paik, I.K. )

    1991-07-01

    Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event of safety rod failure. The MODFLOW code discussed here provides transient moderator flow pattern information with stratification effects, and tracks the location of ink plumes in the reactor. The code, written in Fortran, is compiled for Macintosh II computers, and includes subroutines for interactive control and graphical output. Removing the graphics capabilities, the code can also be compiled on other computers. With graphics, in addition to the capability to perform safety related computations, MODFLOW also provides an easy tool for becoming familiar with flow distributions in SRS reactors.

  17. 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.

  18. Center for Neutron Research Project. Status report

    SciTech Connect

    West, C.D.; Primm, R.T. III; Copeland, G.L.; Difilippo, F.C.; Griess, J.C.; Gambill, W.R.; Moon, R.M.; Siman-Tov, I.I.

    1986-09-01

    The Center for Neutron Research (CNR) will provide the world's best facilities for the study of neutron scattering. The CNR will contain a very high flux reactor that will achieve an extremely high power density (between 4 and 8 MW/L). The reactor is to be fueled with uranium silicide and cooled, moderated, and reflected by D/sub 2/O. Initial reactor physics calculations indicate that a power level of 270 MW with a reactor core volume of 35 L will achieve a peak thermal flux in the reflector of 10/sup 20/ neutrons x m/sup -2/ x s/sup -1/. The reactor fuel will be contained in thin (1.3-mm) plates, similar to those employed in the very successful High-Flux Isotope Reactor, and will be graded in the axial and radial directions. Coolant velocity is to be 27 m/s, and core inlet pressure is to be 5.6 MPa. Maximum fuel centerline temperature will be approx.350/sup 0/C. Initial thermal-hydraulic studies indicate that some method of preventing the formation of aluminum oxide on the fuel clad is required if the highest performance is to be achieved. Tests to confirm these calculations are planned. One of the experimental facilities is to be a cold (10-MeV) neutron source. Calculations to determine the size of the source have been initiated, but additional cross-section data are needed. An abbreviated version of a tentative program plan for fiscal year 1987 and beyond is described. Total program expenditures are expected to be $40 million over 5 years.

  19. Neutronic reactor construction

    DOEpatents

    Huston, Norman E.

    1976-07-06

    1. A neutronic reactor comprising a moderator including horizontal layers formed of horizontal rows of graphite blocks, alternate layers of blocks having the rows extending in one direction, the remaining alternate layers having the rows extending transversely to the said one direction, alternate rows of blocks in one set of alternate layers having longitudinal ducts, the moderator further including slotted graphite tubes positioned in the ducts, the reactor further comprising an aluminum coolant tube positioned within the slotted tube in spaced relation thereto, bodies of thermal-neutron-fissionable material, and jackets enclosing the bodies and being formed of a corrosion-resistant material having a low neutron-capture cross section, the bodies and jackets being positioned within the coolant tube so that the jackets are spaced from the coolant tube.

  20. Accelerator based epithermal neutron source for neutron capture therapy

    SciTech Connect

    Brugger, R.; Kunze, J.

    1991-05-01

    Several investigators have suggested that a charged particle accelerator with light element reactions might be able to produce enough epithermal neutrons to be useful in Neutron Capture Therapy. The reaction choice so far has been the Li(p,n) reaction with protons up to 2.5 MeV. A moderator around the target would reduce the faster neutrons down to the epithermal energy region. The goals of the present research are: identify better reactions; improve the moderators; and find better combinations of 1 and 2. The target is to achieve, at the patient location, an epithermal neutron current of greater than 10{sup 9}n/cm{sup 2}sec, with a dose to tissue from the neutrons alone of less than 10{sup {minus}10} rads/n and a dose from the gamma rays in the beam of less than 10{sup {minus}10} rads/n.

  1. Neutron Fluence Monitoring by Foil Activation at the NBSR

    SciTech Connect

    Richard M. Lindstrom

    2000-11-12

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

  2. Cold injuries.

    PubMed

    Long, William B; Edlich, Richard F; Winters, Kathryne L; Britt, L D

    2005-01-01

    Exposure to cold can produce a variety of injuries that occur as a result of man's inability to adapt to cold. These injuries can be divided into localized injury to a body part, systemic hypothermia, or a combination of both. Body temperature may fall as a result of heat loss by radiation, evaporation, conduction, and convection. Hypothermia or systemic cold injury occurs when the core body temperature has decreased to 35 degrees C (95 degrees F) or less. The causes of hypothermia are either primary or secondary. Primary, or accidental, hypothermia occurs in healthy individuals inadequately clothed and exposed to severe cooling. In secondary hypothermia, another illness predisposes the individual to accidental hypothermia. Hypothermia affects multiple organs with symptoms of hypothermia that vary according to the severity of cold injury. The diagnosis of hypothermia is easy if the patient is a mountaineer who is stranded in cold weather. However, it may be more difficult in an elderly patient who has been exposed to a cold environment. In either case, the rectal temperature should be checked with a low-reading thermometer. The general principals of prehospital management are to (1) prevent further heat loss, (2) rewarm the body core temperature in advance of the shell, and (3) avoid precipitating ventricular fibrillation. There are two general techniques of rewarming--passive and active. The mechanisms of peripheral cold injury can be divided into phenomena that affect cells and extracellular fluids (direct effects) and those that disrupt the function of the organized tissue and the integrity of the circulation (indirect effects). Generally, no serious damage is seen until tissue freezing occurs. The mildest form of peripheral cold injury is frostnip. Chilblains represent a more severe form of cold injury than frostnip and occur after exposure to nonfreezing temperatures and damp conditions. Immersion (trench) foot, a disease of the sympathetic nerves and blood

  3. Cold injuries.

    PubMed

    Long, William B; Edlich, Richard F; Winters, Kathryne L; Britt, L D

    2005-01-01

    Exposure to cold can produce a variety of injuries that occur as a result of man's inability to adapt to cold. These injuries can be divided into localized injury to a body part, systemic hypothermia, or a combination of both. Body temperature may fall as a result of heat loss by radiation, evaporation, conduction, and convection. Hypothermia or systemic cold injury occurs when the core body temperature has decreased to 35 degrees C (95 degrees F) or less. The causes of hypothermia are either primary or secondary. Primary, or accidental, hypothermia occurs in healthy individuals inadequately clothed and exposed to severe cooling. In secondary hypothermia, another illness predisposes the individual to accidental hypothermia. Hypothermia affects multiple organs with symptoms of hypothermia that vary according to the severity of cold injury. The diagnosis of hypothermia is easy if the patient is a mountaineer who is stranded in cold weather. However, it may be more difficult in an elderly patient who has been exposed to a cold environment. In either case, the rectal temperature should be checked with a low-reading thermometer. The general principals of prehospital management are to (1) prevent further heat loss, (2) rewarm the body core temperature in advance of the shell, and (3) avoid precipitating ventricular fibrillation. There are two general techniques of rewarming--passive and active. The mechanisms of peripheral cold injury can be divided into phenomena that affect cells and extracellular fluids (direct effects) and those that disrupt the function of the organized tissue and the integrity of the circulation (indirect effects). Generally, no serious damage is seen until tissue freezing occurs. The mildest form of peripheral cold injury is frostnip. Chilblains represent a more severe form of cold injury than frostnip and occur after exposure to nonfreezing temperatures and damp conditions. Immersion (trench) foot, a disease of the sympathetic nerves and blood

  4. Reaction-in-flight neutrons as a test of stopping power in degenerate plasmas

    SciTech Connect

    Hayes, A. C.; Jungman, Gerard; Schulz, A. E.; Boswell, M.; Fowler, M. M.; Grim, G.; Klein, A.; Rundberg, R. S.; Wilhelmy, J. B.; Wilson, D.; Cerjan, C.; Schneider, D.; Sepke, S. M.; Tonchev, A.; Yeamans, C.

    2015-08-06

    We present the first measurements of reaction-in-flight (RIF) neutrons in an inertial confinement fusion system. The experiments were carried out at the National Ignition Facility, using both Low Foot and High Foot drives and cryogenic plastic capsules. In both cases, the high-energy RIF (En > 15 MeV) component of the neutron spectrum was found to be about 10–4 of the total. The majority of the RIF neutrons were produced in the dense cold fuel surrounding the burning hotspot of the capsule, and the data are consistent with a compressed cold fuel that is moderately to strongly coupled (Γ~ 0.6) and electron degenerate (θFermie~ 4). The production of RIF neutrons is controlled by the stopping power in the plasma. Thus, the current RIF measurements provide a unique test of stopping power models in an experimentally unexplored plasma regime. In conclusion, we find that the measured RIF data strongly constrain stopping models in warm dense plasma conditions, and some models are ruled out by our analysis of these experiments.

  5. Reaction-in-flight neutrons as a test of stopping power in degenerate plasmas

    NASA Astrophysics Data System (ADS)

    Hayes, A. C.; Jungman, Gerard; Schulz, A. E.; Boswell, M.; Fowler, M. M.; Grim, G.; Klein, A.; Rundberg, R. S.; Wilhelmy, J. B.; Wilson, D.; Cerjan, C.; Schneider, D.; Sepke, S. M.; Tonchev, A.; Yeamans, C.

    2015-08-01

    We present the first measurements of reaction-in-flight (RIF) neutrons in an inertial confinement fusion system. The experiments were carried out at the National Ignition Facility, using both Low Foot and High Foot drives and cryogenic plastic capsules. In both cases, the high-energy RIF ( En> 15 MeV) component of the neutron spectrum was found to be about 10-4 of the total. The majority of the RIF neutrons were produced in the dense cold fuel surrounding the burning hotspot of the capsule, and the data are consistent with a compressed cold fuel that is moderately to strongly coupled (Γ˜ 0.6) and electron degenerate (θFermi/θe˜ 4). The production of RIF neutrons is controlled by the stopping power in the plasma. Thus, the current RIF measurements provide a unique test of stopping power models in an experimentally unexplored plasma regime. We find that the measured RIF data strongly constrain stopping models in warm dense plasma conditions, and some models are ruled out by our analysis of these experiments.

  6. Reaction-in-flight neutrons as a test of stopping power in degenerate plasmas

    DOE PAGES

    Hayes, A. C.; Jungman, Gerard; Schulz, A. E.; Boswell, M.; Fowler, M. M.; Grim, G.; Klein, A.; Rundberg, R. S.; Wilhelmy, J. B.; Wilson, D.; et al

    2015-08-06

    We present the first measurements of reaction-in-flight (RIF) neutrons in an inertial confinement fusion system. The experiments were carried out at the National Ignition Facility, using both Low Foot and High Foot drives and cryogenic plastic capsules. In both cases, the high-energy RIF (En > 15 MeV) component of the neutron spectrum was found to be about 10–4 of the total. The majority of the RIF neutrons were produced in the dense cold fuel surrounding the burning hotspot of the capsule, and the data are consistent with a compressed cold fuel that is moderately to strongly coupled (Γ~ 0.6) andmore » electron degenerate (θFermi/θe~ 4). The production of RIF neutrons is controlled by the stopping power in the plasma. Thus, the current RIF measurements provide a unique test of stopping power models in an experimentally unexplored plasma regime. In conclusion, we find that the measured RIF data strongly constrain stopping models in warm dense plasma conditions, and some models are ruled out by our analysis of these experiments.« less

  7. Characterization of a neutron-beta counting system with beta-delayed neutron emitters

    NASA Astrophysics Data System (ADS)

    Agramunt, J.; Tain, J. L.; Gómez-Hornillos, M. B.; Garcia, A. R.; Albiol, F.; Algora, A.; Caballero-Folch, R.; Calviño, F.; Cano-Ott, D.; Cortés, G.; Domingo-Pardo, C.; Eronen, T.; Gelletly, W.; Gorelov, D.; Gorlychev, V.; Hakala, H.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Kolhinen, V.; Kucuk, L.; Martinez, T.; Mason, P. J. R.; Moore, I.; Penttilä, H.; Podolyák, Zs.; Pretel, C.; Reponen, M.; Riego, A.; Rissanen, J.; Rubio, B.; Saastamoinen, A.; Tarifeño-Saldivia, A.; Valencia, E.

    2016-01-01

    A new detection system for the measurement of beta-delayed neutron emission probabilities has been characterized using fission products with well known β-delayed neutron emission properties. The setup consists of BELEN-20, a 4π neutron counter with twenty 3He proportional tubes arranged inside a large polyethylene neutron moderator, a thin Si detector for β counting and a self-triggering digital data acquisition system. The use of delayed-neutron precursors with different neutron emission windows allowed the study of the effect of energy dependency on neutron, β and β-neutron rates. The observed effect is well reproduced by Monte Carlo simulations. The impact of this dependency on the accuracy of neutron emission probabilities is discussed. A new accurate value of the neutron emission probability for the important delayed-neutron precursor 137I was obtained, Pn = 7.76(14)%.

  8. China Advanced Research Reactor (CARR): A new reactor to be built in China for neutron scattering studies

    NASA Astrophysics Data System (ADS)

    Ye, Chuntang

    This paper outlines the main features of the CARR, a 60 MW tank-in-pool inverse neutron trap-type research reactor, which will soon be built at China Institute of Atomic Energy in Beijing to meet the increasing demands of neutron scattering research as well as isotope production in China. According to the design, slightly pressurized light water will be used both as the moderator and the primary cooling water. The undermoderated core will be surrounded by heavy water reflector, where the maximum unperturbed thermal neutron flux would be expected to be 8 × 10 14n/s cm 2 at 60 MW. Nine tangent horizontal beam tubes and some vertical tubes will be installed in the reflector. A cold source, a hot source and a 30 × 50 m 2 guide tube hall will be equipped. The CARR is due to come critical in the year of 2004.

  9. COLD TRAP

    DOEpatents

    Milleron, N.

    1963-03-12

    An improved linear-flow cold trap is designed for highvacuum applications such as mitigating back migration of diffusion pump oil moiecules. A central pot of liquid nitrogen is nested within and supported by a surrounding, vertical, helical coil of metai sheet, all enveloped by a larger, upright, cylindrical, vacuum vessel. The vertical interstices between successive turns of the coil afford lineal, axial, high-vacuum passages between open mouths at top and bottom of said vessel, while the coil, being cold by virtue of thermal contact of its innermost turn with the nitrogen pot, affords expansive proximate condensation surfaces. (AEC)

  10. Radial Flux Distribution of Low-Energy Neutrons.

    ERIC Educational Resources Information Center

    Higinbotham, J.

    1979-01-01

    Describes an experiment designed to illustrate the basic principle involved in the process of moderation of fast neutrons by water, and the monitoring of the low-energy neutron flux using indium as a probe. (GA)

  11. Lansce liquid hydrogen moderator system hardware-characteristic-operation

    SciTech Connect

    Robinson, H.; Russell, G.J.; Tucker, E.; Whitaker, R.; Williamson, K.; Edeskuty, F.

    1985-01-01

    In this paper, we report the current status of the hardware development and testing program for a liquid hydrogen moderator system currently being fabricated for installation into the Los Alamos Neutron Scattering Center (LANSCE) upgraded target system.

  12. Project COLD.

    ERIC Educational Resources Information Center

    Kazanjian, Wendy C.

    1982-01-01

    Describes Project COLD (Climate, Ocean, Land, Discovery) a scientific study of the Polar Regions, a collection of 35 modules used within the framework of existing subjects: oceanography, biology, geology, meterology, geography, social science. Includes a partial list of topics and one activity (geodesic dome) from a module. (Author/SK)

  13. JACKETED FUEL ELEMENTS FOR GRAPHITE MODERATED REACTORS

    DOEpatents

    Szilard, L.; Wigner, E.P.; Creutz, E.C.

    1959-05-12

    Fuel elements for a heterogeneous, fluid cooled, graphite moderated reactor are described. The fuel elements are comprised of a body of natural uranium hermetically sealed in a jacket of corrosion resistant material. The jacket, which may be aluminum or some other material which is non-fissionable and of a type having a low neutron capture cross-section, acts as a barrier between the fissioning isotope and the coolant or moderator or both. The jacket minimizes the tendency of the moderator and coolant to become radioactive and/or contaminated by fission fragments from the fissioning isotope.

  14. Neutron tube design study for boron neutron capture therapy application

    SciTech Connect

    Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1999-05-06

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

  15. Why Being Cold Might Foster a Cold

    MedlinePlus

    ... medlineplus.gov/news/fullstory_159805.html Why Being Cold Might Foster a Cold Healthy body temperature boosts ability of immune system ... proving Mom right: Your odds of avoiding a cold get better if you bundle up and stay ...

  16. 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.

  17. QPO Constraints on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Miller, M. Coleman

    2005-01-01

    The kilohertz frequencies of QPOs from accreting neutron star systems imply that they are generated in regions of strong gravity, close to the star. This suggests that observations of the QPOs can be used to constrain the properties of neutron stars themselves, and in particular to inform us about the properties of cold matter beyond nuclear densities. Here we discuss some relatively model-insensitive constraints that emerge from the kilohertz QPOs, as well as recent developments that may hint at phenomena related to unstable circular orbits outside neutron stars.

  18. Hot, Cold, and Really Cold.

    ERIC Educational Resources Information Center

    Leyden, Michael

    1997-01-01

    Describes a physics experiment investigating temperature prediction and the relationship between the physical properties of heat units, melting, dissolving, states of matter, and energy loss. Details the experimental setup, which requires hot and cold water, a thermometer, and ice. Notes that the experiment employs a deliberate counter-intuitive…

  19. Thermal neutron analysis (TNA) explosive detection based on electronic neutron generators

    SciTech Connect

    Lee, W.; Mahood, D.B.; Ryge, P.

    1994-12-31

    Thermal neutron analysis explosive detection systems have been developed and demonstrated for inspection of checked airline baggage and for detection of buried land mines. Thermal neutrons from a moderated neutron source impinge on the inspected object and the resulting capture gamma ray signatures provide detection information. Isotopic neutron sources, e.g. {sup 252}Cf, are compact, economical and reliable, but they are subject to the licensing requirements, safety concerns and public perception problems associated with radioactive material. These are mitigated by use of an electronic neutron generator - an ion accelerator with a target producing neutrons by a nuclear reaction such as D(d,n){sup 3}He or {sup 9}Be(d,n){sup 10}B. With suitable moderator designs based on neutron transport codes, operational explosive detection systems can be build and would provide effective alternatives to radioactive neutron sources. Calculations as well as laboratory and field experience with three generator types will be presented.

  20. Physiological characteristics of cold acclimatization in man

    NASA Astrophysics Data System (ADS)

    Mathew, Lazar; Purkayastha, S. S.; Jayashankar, A.; Nayar, H. S.

    1981-09-01

    Studies were conducted on 15 healthy young soldiers to evaluate the effect of a cold acclimatization schedule on the thermoregulatory and metabolic activity on exposure to acute cold stress. These men were exposed to cold (10‡C) for 4 h daily wearing only shorts for 21 days, in a cold chamber. They were subjected to a standard cold test at 10 ± 1‡C the day 1, 6, 11 and 21. The subjects were made to relax in a thermoneutral room (26 28‡C) for 1 h and their heart rate, blood pressure, oxygen consumption, oral temperature, mean skin temperature, mean body temperature, peripheral temperatures, and shivering activity were recorded. Then they were exposed to 10‡C and measurements were repeated at 30 min intervals, for 2 h. The cold induced vasodilatation (CIVD), cold pressor response and thermoregulatory efficiency tests were measured initially and at the end of acclimatization schedule. The data show that the procedure resulted in elevated resting metabolism, less fall in body temperature during acute cold stress, reduction in shivering, improvement in CIVD and thermoregulatory efficiency and less rise in BP and HR during cold pressor response. The data suggest the possibility of cold acclimatization in man by repeated exposure to moderately severe cold stress.

  1. Study of 232Th(n, γ) and 232Th(n,f) reaction rates in a graphite moderated spallation neutron field produced by 1.6 GeV deuterons on lead target

    NASA Astrophysics Data System (ADS)

    Asquith, N. L.; Hashemi-Nezhad, S. R.; Westmeier, W.; Zhuk, I.; Tyutyunnikov, S.; Adam, J.

    2015-02-01

    The Gamma-3 assembly of the Joint Institute for Nuclear Research (JINR), Dubna, Russia is designed to emulate the neutron spectrum of a thermal Accelerator Driven System (ADS). It consists of a lead spallation target surrounded by reactor grade graphite. The target was irradiated with 1.6 GeV deuterons from the Nuclotron accelerator and the neutron capture and fission rate of 232Th in several locations within the assembly were experimentally measured. 232Th is a proposed fuel for envisaged Accelerator Driven Systems and these two reactions are fundamental to the performance and feasibility of 232Th in an ADS. The irradiation of the Gamma-3 assembly was also simulated using MCNPX 2.7 with the INCL4 intra-nuclear cascade and ABLA fission/evaporation models. Good agreement between the experimentally measured and calculated reaction rates was found. This serves as a good validation for the computational models and cross section data used to simulate neutron production and transport of spallation neutrons within a thermal ADS.

  2. Chilling Out with Colds

    MedlinePlus

    ... most common cold virus, but more than 200 viruses can cause colds. Because there are so many, ... to help you feel better. Take that, cold viruses! continue How Kids Catch Colds Mucus (say: MYOO- ...

  3. Coping with Cold Sores

    MedlinePlus

    ... Here's Help White House Lunch Recipes Coping With Cold Sores KidsHealth > For Kids > Coping With Cold Sores ... sore." What's that? Adam wondered. What Is a Cold Sore? Cold sores are small blisters that is ...

  4. FAST NEUTRONIC REACTOR

    DOEpatents

    Snell, A.H.

    1957-12-01

    This patent relates to a reactor and process for carrying out a controlled fast neutron chain reaction. A cubical reactive mass, weighing at least 920 metric tons, of uranium metal containing predominantly U/sup 238/ and having a U/sup 235/ content of at least 7.63% is assembled and the maximum neutron reproduction ratio is limited to not substantially over 1.01 by insertion and removal of a varying amount of boron, the reactive mass being substantially freed of moderator.

  5. Ultracold neutron source at the PULSTAR reactor: Engineering design and cryogenic testing

    NASA Astrophysics Data System (ADS)

    Korobkina, E.; Medlin, G.; Wehring, B.; Hawari, A. I.; Huffman, P. R.; Young, A. R.; Beaumont, B.; Palmquist, G.

    2014-12-01

    Construction is completed and commissioning is in progress for an ultracold neutron (UCN) source at the PULSTAR reactor on the campus of North Carolina State University. The source utilizes two stages of neutron moderation, one in heavy water at room temperature and the other in solid methane at ~ 40 K, followed by a converter stage, solid deuterium at 5 K, that allows a single down scattering of cold neutrons to provide UCN. The UCN source rolls into the thermal column enclosure of the PULSTAR reactor, where neutrons will be delivered from a bare face of the reactor core by streaming through a graphite-lined assembly. The source infrastructure, i.e., graphite-lined assembly, heavy-water system, gas handling system, and helium liquefier cooling system, has been tested and all systems operate as predicted. The research program being considered for the PULSTAR UCN source includes the physics of UCN production, fundamental particle physics, and material surface studies of nanolayers containing hydrogen. In the present paper we report details of the engineering and cryogenic design of the facility as well as results of critical commissioning tests without neutrons.

  6. Review of the Lujan neutron scattering center: basic energy sciences prereport February 2009

    SciTech Connect

    Hurd, Alan J; Rhyne, James J; Lewis, Paul S

    2009-01-01

    The Lujan Neutron Scattering Center (Lujan Center) at LANSCE is a designated National User Facility for neutron scattering and nuclear physics studies with pulsed beams of moderated neutrons (cold, thermal, and epithermal). As one of five experimental areas at the Los Alamos Neutron Science Center (LANSCE), the Lujan Center hosts engineers, scientists, and students from around the world. The Lujan Center consists of Experimental Room (ER) 1 (ERl) built by the Laboratory in 1977, ER2 built by the Office of Basic Energy Sciences (BES) in 1989, and the Office Building (622) also built by BES in 1989, along with a chem-bio lab, a shop, and other out-buildings. According to a 1996 Memorandum of Agreement (MOA) between the Defense Programs (DP) Office of the National Nuclear Security Agency (NNSA) and the Office of Science (SC, then the Office of Energy Research), the Lujan Center flight paths were transferred from DP to SC, including those in ERI. That MOA was updated in 2001. Under the MOA, NNSA-DP delivers neutron beam to the windows of the target crypt, outside of which BES becomes the 'landlord.' The leveraging nature of the Lujan Center on the LANSCE accelerator is a substantial annual leverage to the $11 M BES operating fund worth approximately $56 M operating cost of the linear accelerator (LINAC)-in beam delivery.

  7. First production of ultracold neutrons with a solid deuterium source at the pulsed reactor TRIGA Mainz⋆

    NASA Astrophysics Data System (ADS)

    Frei, A.; Sobolev, Yu.; Altarev, I.; Eberhardt, K.; Gschrey, A.; Gutsmiedl, E.; Hackl, R.; Hampel, G.; Hartmann, F. J.; Heil, W.; Kratz, J. V.; Lauer, Th.; Liźon Aguilar, A.; Müller, A. R.; Paul, S.; Pokotilovski, Yu.; Schmid, W.; Tassini, L.; Tortorella, D.; Trautmann, N.; Trinks, U.; Wiehl, N.

    2007-11-01

    The production rates of ultracold neutrons (UCN) with a solid deuterium converter have been measured at the pulsed reactor TRIGA Mainz. Exposed to a thermal neutron fluence of ensuremath ˜ 1\\cdot 10^{13} n·cm^-2·pulse^-1, the number of detected very cold and ultracold neutrons ranges up to 200 000 at 7mol of solid deuterium (sD2) in combination with a pre-moderator (mesitylene). About 50% of the measured neutrons can be assigned to UCN with energies E of ensuremath V_F(sD_2)≤ E ≤ V_F(guide) where V F( sD 2) = 105 neV and V F( guide) = 190 neV are the Fermi potentials of the sD2 converter and our stainless steel neutron guides, respectively. Thermal cycling of solid deuterium, which was frozen out from the gas phase, considerably improved the UCN yield, in particular at higher amounts of sD2.

  8. Nickel Mirror And Supermirror Neutron Guide Tubes At The Kyoto University Research Reactor

    NASA Astrophysics Data System (ADS)

    Ebisawa, Toru; Akiyoshi, Tsunekazu; Tasaki, Seiji; Kawai, Takeshi; Achiwa, Norio; Utsuro, Masahiko; Okamoto, Sunao

    1989-01-01

    We installed the first nickel mirror neutron guide tube with a characteristic wavelength of 2.85 Å at Kyoto University research reactor(KUR, 5MW, cooled and moderated by light water) in 1973 and a supermirror guide tube with a characteristic wavelength of 1.17 Å in 1984, in order to get more intense thermal neutron beam. Four guide tubes are under construction at a cold neutron source installed in 1986. Two of them are supermirror type with a characteristic wavelength of 3 Å and the others are supermirror and Ni-mirror type with characteristic wavelengths of 6 Å and 23 Å, respectively. Supermirrors are made by automatically controlled vacuum deposition of nickel and titanium metal with electron gun. Their averaging reflectivity for the first supermirror guide tube are the following: The apparent critical wavelength, λ/θ, of reflection is 240 Å in term of wavelength(λ/θ) corresponding to the component of wave number perpendicular to the mirror surface. The reflectivity is 0.65 at the apparent critical wavelength and becomes higher with increasing neutron wavelength up to nearly unity for wavelength longer than 500 Å. Supermirror guide tubes are featured by more available neutrons with larger divergent angles and shorter length of the guide tubes. These features would bring us significant advantages depending on experimental requirements.

  9. High-power liquid-lithium target prototype for accelerator-based boron neutron capture therapy.

    PubMed

    Halfon, S; Paul, M; Arenshtam, A; Berkovits, D; Bisyakoev, M; Eliyahu, I; Feinberg, G; Hazenshprung, N; Kijel, D; Nagler, A; Silverman, I

    2011-12-01

    A prototype of a compact Liquid-Lithium Target (LiLiT), which will possibly constitute an accelerator-based intense neutron source for Boron Neutron Capture Therapy (BNCT) in hospitals, was built. The LiLiT setup is presently being commissioned at Soreq Nuclear Research Center (SNRC). The liquid-lithium target will produce neutrons through the (7)Li(p,n)(7)Be reaction and it will overcome the major problem of removing the thermal power generated using a high-intensity proton beam (>10 kW), necessary for sufficient neutron flux. In off-line circulation tests, the liquid-lithium loop generated a stable lithium jet at high velocity, on a concave supporting wall; the concept will first be tested using a high-power electron beam impinging on the lithium jet. High intensity proton beam irradiation (1.91-2.5 MeV, 2-4 mA) will take place at Soreq Applied Research Accelerator Facility (SARAF) superconducting linear accelerator currently in construction at SNRC. Radiological risks due to the (7)Be produced in the reaction were studied and will be handled through a proper design, including a cold trap and appropriate shielding. A moderator/reflector assembly is planned according to a Monte Carlo simulation, to create a neutron spectrum and intensity maximally effective to the treatment and to reduce prompt gamma radiation dose risks.

  10. COLD TRAPS

    DOEpatents

    Thompson, W.I.

    1958-09-30

    A cold trap is presented for removing a condensable component from a gas mixture by cooling. It consists of a shell, the exterior surface of which is chilled by a refrigerant, and conductive fins welded inside the shell to condense the gas, and distribute the condensate evenly throughout the length of the trap, so that the trap may function until it becomes completely filled with the condensed solid. The contents may then be removed as either a gas or as a liquid by heating the trap. This device has particuinr use as a means for removing uranium hexafluoride from the gaseous diffusion separation process during equipment breakdown and repair periods.

  11. Neutron whispering gallery

    NASA Astrophysics Data System (ADS)

    Nesvizhevsky, Valery V.; Voronin, Alexei Yu.; Cubitt, Robert; Protasov, Konstantin V.

    2010-02-01

    The `whispering gallery' effect has been known since ancient times for sound waves in air, later in water and more recently for a broad range of electromagnetic waves: radio, optics, Roentgen and so on. It consists of wave localization near a curved reflecting surface and is expected for waves of various natures, for instance, for atoms and neutrons. For matter waves, it would include a new feature: a massive particle would be settled in quantum states, with parameters depending on its mass. Here, we present for the first time the quantum whispering-gallery effect for cold neutrons. This phenomenon provides an example of an exactly solvable problem analogous to the `quantum bouncer'; it is complementary to the recently discovered gravitationally bound quantum states of neutrons . These two phenomena provide a direct demonstration of the weak equivalence principle for a massive particle in a pure quantum state. Deeply bound whispering-gallery states are long-living and weakly sensitive to surface potential; highly excited states are short-living and very sensitive to the wall potential shape. Therefore, they are a promising tool for studying fundamental neutron-matter interactions, quantum neutron optics and surface physics effects.

  12. COMPOSITE NEUTRONIC REACTOR

    DOEpatents

    Menke, J.R.

    1963-06-11

    This patent relates to a reactor having a core which comprises an inner active region and an outer active region, each region separately having a k effective less than one and a k infinity greater than one. The inner and outer regions in combination have a k effective at least equal to one and each region contributes substantially to the k effective of the reactor core. The inner region has a low moderator to fuel ratio such that the majority of fissions occurring therein are induced by neutrons having energies greater than thermal. The outer region has a high moderator to fuel ratio such that the majority of fissions occurring therein are induced by thermal neutrons. (AEC)

  13. Neutron coincidence detectors employing heterogeneous materials

    DOEpatents

    Czirr, J. Bartley; Jensen, Gary L.

    1993-07-27

    A neutron detector relies upon optical separation of different scintillators to measure the total energy and/or number of neutrons from a neutron source. In pulse mode embodiments of the invention, neutrons are detected in a first detector which surrounds the neutron source and in a second detector surrounding the first detector. An electronic circuit insures that only events are measured which correspond to neutrons first detected in the first detector followed by subsequent detection in the second detector. In spectrometer embodiments of the invention, neutrons are thermalized in the second detector which is formed by a scintillator-moderator and neutron energy is measured from the summed signals from the first and second detectors.

  14. Neutron production enhancements for the Intense Pulsed Neutron Source.

    SciTech Connect

    Iverson, E. B.

    1999-01-04

    The Intense Pulsed Neutron Source (IPNS) was the first high energy spallation neutron source in the US dedicated to materials research. It has operated for sixteen years, and in that time has had a very prolific record concerning the development of new target and moderator systems for pulsed spallation sources. IPNS supports a very productive user program on its thirteen instruments, which are oversubscribed by more than two times, meanwhile having an excellent overall reliability of 95%. Although the proton beam power is relatively low at 7 kW, the target and moderator systems are very efficient. The typical beam power which gives an equivalent flux for long-wavelength neutrons is about 60 kW, due to the use of a uranium target and liquid and solid methane moderators, precluded at some sources due to a higher accelerator power. The development of new target and moderator systems is by no means stagnant at IPNS. They are presently considering numerous enhancements to the target and moderators that offer prospects for increasing the useful neutron production by substantial factors. Many of these enhancements could be combined, although their combined benefit has not yet been well established. Meanwhile, IPNS is embarking on a coherent program of study concerning these improvements and their possible combination and implementation. Moreover, any improvements accomplished at IPNS would immediately increase the performance of IPNS instruments.

  15. THERMAL NEUTRONIC REACTOR

    DOEpatents

    Spinrad, B.I.

    1960-01-12

    A novel thermal reactor was designed in which a first reflector formed from a high atomic weight, nonmoderating material is disposed immediately adjacent to the reactor core. A second reflector composed of a moderating material is disposed outwardly of the first reflector. The advantage of this novel reflector arrangement is that the first reflector provides a high slow neutron flux in the second reflector, where irradiation experiments may be conducted with a small effect on reactor reactivity.

  16. A neutron guide installation status and its first performance test result at KAERI

    NASA Astrophysics Data System (ADS)

    Cho, S. J.; Cho, Y. G.; Lee, C. H.; Lee, K. H.; Kim, K. P.

    2011-04-01

    A neutron guide system that includes neutron guides, a main shutter, and a vacuum system was successfully installed at the HANARO research reactor of the Korea Atomic Energy Research Institute (KAERI) last year, and is now operating with 5 cold neutron instruments. The neutron flux and spectrum were measured by using gold wire and a disc chopper. The total measured neutron fluxes for various position are about 10-25% lower than the calculated fluxes, which is probably caused by neutron guide misalignment, larger gap between neutron guides, low reflectivity, imperfect cold neutron source data, and so on. But the measured neutron fluxes of the neutron guides are very high. The status of the neutron guide installation and its first performance test result is described in this paper.

  17. 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.

  18. From X-Ray Telescopes to Neutron Focusing

    NASA Technical Reports Server (NTRS)

    Gubarev, M. V.; Khaykovich, B.; Ramsey, B.; Moncton, D. E.

    2011-01-01

    In the case of neutrons the refractive index is slightly less than unity for most elements and their isotopes. Consequently, thermal and cold neutrons can be reflected from smooth surfaces at grazing-incidence angles. Hence, the optical technologies developed for x-ray astronomy can be applied for neutron focusing. The focusing capabilities of grazing incidence neutron imaging optics have been successfully demonstrated using nickel mirrors. The mirrors were fabricated using an electroformed nickel replication process at Marshall Space Flight Center. Results of the neutron optics experiments will be presented. Challenges of the neutron imaging optics as well as possible applications of the optics will be discussed.

  19. 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.

  20. 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.

  1. Design progress of cryogenic hydrogen system for China Spallation Neutron Source

    NASA Astrophysics Data System (ADS)

    Wang, G. P.; Zhang, Y.; Xiao, J.; He, C. C.; Ding, M. Y.; Wang, Y. Q.; Li, N.; He, K.

    2014-01-01

    China Spallation Neutron Source (CSNS) is a large proton accelerator research facility with 100 kW beam power. Construction started in October 2011 and is expected to last 6.5 years. The cryogenic hydrogen circulation is cooled by a helium refrigerator with cooling capacity of 2200 W at 20 K and provides supercritical hydrogen to neutron moderating system. Important progresses of CSNS cryogenic system were concluded as follows. Firstly, process design of cryogenic system has been completed including helium refrigerator, hydrogen loop, gas distribution, and safety interlock. Secondly, an accumulator prototype was designed to mitigate pressure fluctuation caused by dynamic heat load from neutron moderation. Performance test of the accumulator has been carried out at room and liquid nitrogen temperature. Results show the accumulator with welding bellows regulates hydrogen pressure well. Parameters of key equipment have been identified. The contract for the helium refrigerator has been signed. Mechanical design of the hydrogen cold box has been completed, and the hydrogen pump, ortho-para hydrogen convertor, helium-hydrogen heat exchanger, hydrogen heater, and cryogenic valves are in procurement. Finally, Hydrogen safety interlock has been finished as well, including the logic of gas distribution, vacuum, hydrogen leakage and ventilation. Generally, design and construction of CSNS cryogenic system is conducted as expected.

  2. Design progress of cryogenic hydrogen system for China Spallation Neutron Source

    SciTech Connect

    Wang, G. P.; Zhang, Y.; Xiao, J.; He, C. C.; Ding, M. Y.; Wang, Y. Q.; Li, N.; He, K.

    2014-01-29

    China Spallation Neutron Source (CSNS) is a large proton accelerator research facility with 100 kW beam power. Construction started in October 2011 and is expected to last 6.5 years. The cryogenic hydrogen circulation is cooled by a helium refrigerator with cooling capacity of 2200 W at 20 K and provides supercritical hydrogen to neutron moderating system. Important progresses of CSNS cryogenic system were concluded as follows. Firstly, process design of cryogenic system has been completed including helium refrigerator, hydrogen loop, gas distribution, and safety interlock. Secondly, an accumulator prototype was designed to mitigate pressure fluctuation caused by dynamic heat load from neutron moderation. Performance test of the accumulator has been carried out at room and liquid nitrogen temperature. Results show the accumulator with welding bellows regulates hydrogen pressure well. Parameters of key equipment have been identified. The contract for the helium refrigerator has been signed. Mechanical design of the hydrogen cold box has been completed, and the hydrogen pump, ortho-para hydrogen convertor, helium-hydrogen heat exchanger, hydrogen heater, and cryogenic valves are in procurement. Finally, Hydrogen safety interlock has been finished as well, including the logic of gas distribution, vacuum, hydrogen leakage and ventilation. Generally, design and construction of CSNS cryogenic system is conducted as expected.

  3. Wolter Optics for Neutron Focusing

    NASA Technical Reports Server (NTRS)

    Mildner, D. F. R.; Gubarev, M. V.

    2010-01-01

    Focusing optics based on Wolter optical geometries developed for x-ray grazing incidence beams can be designed for neutron beams. Wolter optics are formed by grazing incidence reflections from two concentric conic sections (for example, a paraboloid and a hyperboloid). This has transformed observational X-ray astronomy by increasing the sensitivity by many orders of magnitude for research in astrophysics and cosmology. To increase the collection area, many reflecting mirrors of different diameters are nested with a common focal plane. These mirrors are fabricated using nickel-electroformed replication techniques. We apply these ideas to neutron focusing using nickel mirrors. We show an initial test of a conical mirror using a beam of cold neutrons. key words: electroformed nickel replication, focusing optics, grazing angle incidence, mirror reflection, neutron focusing, Wolter optics

  4. Cough & Cold Medicine Abuse

    MedlinePlus

    ... I Help a Friend Who Cuts? Cough & Cold Medicine Abuse KidsHealth > For Teens > Cough & Cold Medicine Abuse ... DXM Why Do People Use Cough and Cold Medicines to Get High? There's an ingredient in many ...

  5. Cold symptoms (image)

    MedlinePlus

    Colds are caused by a virus and can occur year-round. The common cold generally involves a runny nose, nasal congestion, and ... symptoms include sore throat, cough, and headache. A cold usually lasts about 7 days, with perhaps a ...

  6. Vitamin C and colds

    MedlinePlus

    Colds and vitamin C ... is that vitamin C can cure the common cold . However, research about this claim is conflicting. Although ... vitamin C may help reduce how long a cold lasts. They do not protect against getting a ...

  7. Optical neutron polarizers

    SciTech Connect

    Hayter, J.B.

    1990-01-01

    A neutron wave will be refracted by an appropriately varying potential. Optical neutron polarizers use spatially varying, spin- dependent potentials to refract neutrons of opposite spin states into different directions, so that an unpolarized beam will be split into two beams of complementary polarization by such a device. This paper will concentrate on two methods of producing spin-dependent potentials which are particularly well-suited to polarizing cold neutron beams, namely thin-film structures and field-gradient techniques. Thin-film optical devices, such as supermirror multilayer structures, are usually designed to deviate only one spin-state, so that they offer the possibility of making insertion (transmission) polarizers. Very good supermirrors may now be designed and fabricated, but it is not always straightforward to design mirror-based devices which are useful in real (divergent beam) applications, and some practical configurations will be discussed. Field-gradient devices, which are usually based on multipolar magnets, have tended to be too expensive for general use, but this may change with new developments in superconductivity. Dipolar and hexapolar configurations will be considered, with emphasis on the focusing characteristics of the latter. 21 refs., 7 figs.

  8. Measurement of neutron diffraction with compact neutron source RANS

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  9. Precise determination of the deuteron spin structure at low to moderate Q2 with CLAS and extraction of the neutron contribution

    SciTech Connect

    Guler, N.; Fersch, R. G.; Kuhn, S. E.; Bosted, P.; Griffioen, K. A.; Keith, C.; Minehart, R.; Prok, Y.; Adhikari, K. P.; Adikaram, D.; Amaryan, M. J.; Anderson, M. D.; Anefalos Pereira, S.; Avakian, H.; Ball, J.; Battaglieri, M.; Batourine, V.; Bedlinskiy, I.; Biselli, A.; Briscoe, W. J.; Brooks, W. K.; Bültmann, S.; Burkert, V. D.; Carman, D. S.; Celentano, A.; Chandavar, S.; Charles, G.; Colaneri, L.; Cole, P. L.; Contalbrigo, M.; Crabb, D.; Crede, V.; D'Angelo, A.; Dashyan, N.; Deur, A.; Djalali, C.; Dodge, G. E.; Dupre, R.; Alaoui, A. El; El Fassi, L.; Elouadrhiri, L.; Eugenio, P.; Fedotov, G.; Fegan, S.; Filippi, A.; Fleming, J. A.; Forest, T. A.; Garillon, B.; Garçon, M.; Gevorgyan, N.; Gilfoyle, G. P.; Giovanetti, K. L.; Girod, F. X.; Goetz, J. T.; Golovatch, E.; Gothe, R. W.; Guidal, M.; Guo, L.; Hafidi, K.; Hakobyan, H.; Harrison, N.; Hattawy, M.; Hicks, K.; Ho, D.; Holtrop, M.; Hughes, S. M.; Hyde, C. E.; Ireland, D. G.; Ishkhanov, B. S.; Isupov, E. L.; Jo, H. S.; Joo, K.; Joosten, S.; Keller, D.; Khandaker, M.; Kim, A.; Kim, W.; Klein, A.; Klein, F. J.; Kubarovsky, V.; Kuleshov, S. V.; Livingston, K.; Lu, H. Y.; Mayer, M.; MacGregor, I. J. D.; McKinnon, B.; Mirazita, M.; Mokeev, V.; Montgomery, R. A.; Movsisyan, A.; Munoz Camacho, C.; Nadel-Turonski, P.; Net, L. A.; Niculescu, I.; Osipenko, M.; Ostrovidov, A. I.; Park, K.; Pasyuk, E.; Pisano, S.; Pogorelko, O.; Price, J. W.; Procureur, S.; Ripani, M.; Rizzo, A.; Rosner, G.; Rossi, P.; Roy, P.; Sabatié, F.; Salgado, C.; Schott, D.; Schumacher, R. A.; Seder, E.; Simonyan, A.; Skorodumina, Iu.; Sokhan, D.; Sparveris, N.; Strakovsky, I. I.; Strauch, S.; Sytnik, V.; Tian, Ye; Tkachenko, S.; Ungaro, M.; Voutier, E.; Walford, N. K.; Wei, X.; Weinstein, L. B.; Wood, M. H.; Zachariou, N.; Zana, L.; Zhang, J.; Zhao, Z. W.; Zonta, I.

    2015-11-02

    In this study, we present the final results for the deuteron spin structure functions obtained from the full data set collected with Jefferson Lab's CLAS in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.8 GeV were scattered from deuteron (15ND3) targets, dynamically polarized along the beam direction, and detected with CLAS. From the measured double spin asymmetry, the virtual photon absorption asymmetry Ad1 and the polarized structure function gd1 were extracted over a wide kinematic range (0.05 GeV2 < Q2 < 5 GeV2 and 0.9 GeV < W < 3 GeV). We use an unfolding procedure and a parametrization of the corresponding proton results to extract from these data the polarized structure functions An1 and g1n of the (bound) neutron, which are so far unknown in the resonance region, W < 2 GeV. We compare our final results, including several moments of the deuteron and neutron spin structure functions, with various theoretical models and expectations as well as parametrizations of the world data. The unprecedented precision and dense kinematic coverage of these data can aid in future extractions of polarized parton distributions, tests of perturbative QCD predictions for the quark polarization at large x, a better understanding of quark-hadron duality, and more precise values for higher-twist matrix elements in the framework of the Operator Product Expansion.

  10. Characterization of pulsed (plasma focus) neutron source with image plate and application to neutron radiography

    SciTech Connect

    Andola, Sanjay; Niranjan, Ram; Rout, R. K.; Kaushik, T. C.; Gupta, S. C.; Shaikh, A. M.

    2013-02-05

    Plasma focus device of Mather type developed in house has been used first time for neutron radiography of different objects. The device gives (1.2{+-}0.3) Multiplication-Sign 10{sup 9} neutrons per pulse produced by D-D fusion reaction with a pulse width of 50{+-}5 ns. The method involves exposing sample to be radiographed to thermalized D-D neutrons and recording the image on Fuji-film BAS-ND image plates. The thermal neutron component of the moderated beam was estimated using two image plates: a conventional IP for X-rays and gamma rays, and an IP doped with Gd for detecting neutrons.

  11. Self-regulating neutron coincidence counter

    DOEpatents

    Baron, N.

    1980-06-16

    A device for accurately measuring the mass of /sup 240/Pu and /sup 239/Pu in a sample having arbitrary moderation and mixed with various contaminants. The device utilizes a thermal neutron well counter which has two concentric rings of neutron detectors separated by a moderating material surrounding the well. Neutron spectroscopic information derived by the two rings of detectors is used to measure the quantity of /sup 239/Pu and /sup 240/Pu in device which corrects for background radiation, deadtime losses of the detector and electronics and various other constants of the system.

  12. The Art of Neutron Spin Flipping

    NASA Astrophysics Data System (ADS)

    Lieffers, Justin; Holley, Adam; Snow, W. M.

    2014-09-01

    Low energy precision measurements complement high energy collider results in the search for physics beyond the Standard Model. Neutron spin rotation is a sensitive technique to search for possible exotic velocity and spin-dependent interactions involving the neutron from the exchange of light (~ meV) spin 1 bosons. We plan to conduct such searches using beams of cold neutrons at the Los Alamos Neutron Science Center (LANSCE) and the National Institute of Standards and Technology (NIST). To change the spin state of the neutrons in the apparatus we have developed an Adiabatic Fast Passage (AFP) neutron spin flipper. I will present the mechanical design, static and RF magnetic field modeling and measurements, and spin flip efficiency optimization of the constructed device. I would like to acknowledge the NSF REU program (NSF-REU grant PHY-1156540) and the Indiana University nuclear physics group (NSF grant PHY-1306942) for this opportunity.

  13. Cold energy

    SciTech Connect

    Wallace, John P.

    2015-12-04

    Deviations in Q for resonant superconducting radio frequency niobium accelerator cavities are generally correlated with resistivity loss mechanisms. Field dependent Qs are not well modeled by these classical loss mechanisms, but rather can represent a form of precision cavity surface thermometry. When the field dependent Q variation shows improvement with increasing B field level the classical treatment of this problem is inadequate. To justify this behavior hydrogen as a ubiquitous impurity in niobium, which creates measurable property changes, even at very low concentrations is typically considered the cause of such anomalous behavior. This maybe the case in some instances, but more importantly any system operating with a highly coherent field with a significant time dependent magnetic component at near 2° K will have the ability to organize the remaining free spins within the London penetration depth to form a coupled energy reservoir in the form of low mass spin waves. The niobium resonant cavities are composed of a single isotope with a large nuclear spin. When the other loss mechanisms are stripped away this may be the gain medium activated by the low level residual magnetic fields. It was found that one resonant cavity heat treatment produced optimum surface properties and then functioned as a MASER extracting energy from the 2° K thermal bath while cooling the cavity walls. The cavity operating in this mode is a simulator of what can take place in the wider but not colder universe using the cosmic microwave background (CMB) as a thermal source. The low mass, long lifetimes, and the scale of the magnetic spin waves on the weakly magnetized interstellar medium allows energy to be stored that is many orders of magnitude colder than the cosmic microwave background. A linear accelerator cavity becomes a tool to explore the properties of the long wave length magnetic spin waves that populate this cold low energy regime.

  14. Cold energy

    NASA Astrophysics Data System (ADS)

    Wallace, John P.

    2015-12-01

    Deviations in Q for resonant superconducting radio frequency niobium accelerator cavities are generally correlated with resistivity loss mechanisms. Field dependent Qs are not well modeled by these classical loss mechanisms, but rather can represent a form of precision cavity surface thermometry. When the field dependent Q variation shows improvement with increasing B field level the classical treatment of this problem is inadequate. To justify this behavior hydrogen as a ubiquitous impurity in niobium, which creates measurable property changes, even at very low concentrations is typically considered the cause of such anomalous behavior. This maybe the case in some instances, but more importantly any system operating with a highly coherent field with a significant time dependent magnetic component at near 2° K will have the ability to organize the remaining free spins within the London penetration depth to form a coupled energy reservoir in the form of low mass spin waves. The niobium resonant cavities are composed of a single isotope with a large nuclear spin. When the other loss mechanisms are stripped away this may be the gain medium activated by the low level residual magnetic fields. It was found that one resonant cavity heat treatment produced optimum surface properties and then functioned as a MASER extracting energy from the 2° K thermal bath while cooling the cavity walls. The cavity operating in this mode is a simulator of what can take place in the wider but not colder universe using the cosmic microwave background (CMB) as a thermal source. The low mass, long lifetimes, and the scale of the magnetic spin waves on the weakly magnetized interstellar medium allows energy to be stored that is many orders of magnitude colder than the cosmic microwave background. A linear accelerator cavity becomes a tool to explore the properties of the long wave length magnetic spin waves that populate this cold low energy regime.

  15. Cold fusion studies

    NASA Astrophysics Data System (ADS)

    Hembree, D. M.; Burchfield, L. A.; Fuller, E. L., Jr.; Perey, F. G.; Mamantov, G.

    1990-06-01

    A series of experiments designed to detect the by-products expected from deuterium fusion occurring in the palladium and titanium cathodes of heavy water, D2O, electrolysis cells is reported. The primary purpose of this account is to outline the integrated experimental design developed to test the cold fusion hypothesis and to report preliminary results that support continuing the investigation. Apparent positive indicators of deuterium fusion were observed, but could not be repeated or proved to originate from the electrochemical cells. In one instance, two large increases in the neutron count rate, the largest of which exceeded the background by 27 standard deviations, were observed. In a separate experiment, one of the calorimetry cells appeared to be producing approximately 18 percent more power that the input value, but thermistor failure prevented an accurate recording of the event as a function of time. In general, the tritium levels in most cells followed the slow enrichment expected from the electrolysis of D2O containing a small amount of tritium. However, after 576 hours of electrolysis, one cell developed a tritium concentration approximately seven times greater than expected level.

  16. NEUTRONIC REACTOR CORE

    DOEpatents

    Thomson, W.B.; Corbin, A. Jr.

    1961-07-18

    An improved core for a gas-cooled power reactor which admits gas coolant at high temperatures while affording strong integral supporting structure and efficient moderation of neutrons is described. The multiplicities of fuel elements constituting the critical amassment of fissionable material are supported and confined by a matrix of metallic structure which is interspersed therebetween. Thermal insulation is interposed between substantially all of the metallic matrix and the fuel elements; the insulation then defines the principal conduit system for conducting the coolant gas in heat-transfer relationship with the fuel elements. The metallic matrix itseif comprises a system of ducts through which an externally-cooled hydrogeneous liquid, such as water, is circulated to serve as the principal neutron moderant for the core and conjointly as the principal coolant for the insulated metallic structure. In this way, use of substantially neutron transparent metals, such as aluminum, becomes possible for the supporting structure, despite the high temperatures of the proximate gas. The Aircraft Nuclear Propulsion program's "R-1" reactor design is a preferred embodiment.

  17. 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.

  18. The Detector for Advanced Neutron Capture Experiments at LANSCE

    SciTech Connect

    Ullmann, J.L.; Reifarth, R.; Haight, R.C.; Hunt, L.; O'Donnell, J.M.; Rundberg, R.S.; Bredeweg, T.A.; Wilhelmy, J.B.; Fowler, M.M.; Vieira, D.J.; Wouters, J.M.; Strottman, D.D.; Kaeppeler, F.; Heil, M.; Chamberlin, E.P.

    2003-08-26

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 159-element 4{pi} barium fluoride array designed to study neutron capture on small quantities, 1 mg or less, of radioactive nuclides. It is being built on a 20 m neutron flight path which views the 'upper tier' water moderator at the Manuel J. Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center. The detector design is based on Monte Carlo calculations which have suggested ways to minimize backgrounds due to neutron scattering events. A data acquisition system based on fast transient digitizers is being implemented.

  19. Detector for advanced neutron capture experiments at LANSCE

    SciTech Connect

    Ullmann, J. L.; Reifarth, R.; Haight, Robert C.; Hunt, L. F.; O'Donnell, J. M.; Bredeweg, T. A.; Wilhelmy, J. B.; Fowler, Malcolm M.; Vieira, D. J.; Wouters, J. M.; Strottman, D.; Kaeppeler, F.; Heil, M.; Chamberlin, E. P.

    2002-01-01

    The Detector for Advanced Neutron Capture Experiments (DANCE) is a 159-element 4x barium fluoride array designed to study neutron capture on small quantities, 1 mg or less, of radioactive nuclides. It is being built on a 20 m neutron flight path which views the 'upper tier' water moderator at the Manuel J. Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center. The detector design is based on Monte Carlo calculations which have suggested ways to minimize backgrounds due to neutron scattering events. A data acquisition system based on fast transient digitizers is bcing implemented

  20. A SINGLE-EXPOSURE, MULTIDETECTOR NEUTRON SPECTROMETER FOR WORKPLACE MONITORING.

    PubMed

    Bedogni, R; Bortot, D; Buonomo, B; Esposito, A; Gómez-Ros, J M; Introini, M V; Mazzitelli, G; Moraleda, M; Pola, A; Romero, A M

    2016-09-01

    This communication describes a recently developed single-exposure neutron spectrometer, based on multiple active thermal neutron detectors located within a moderating sphere, which have been developed jointly by CIEMAT (Spain), INFN (Italy) and Politecnico di Milano (Italy) in the framework of Italian and Spanish collaboration projects. The fabricated prototypes permit to achieve spectrometric resolution with nearly isotropic response for neutron with energies from thermal to 100-200 MeV, thus being able to characterise the complete neutron spectrum in only one exposure by unfolding the measured responses of the detectors. This makes it especially advantageous for characterising neutron fields and workplace monitoring purposes in neutron-producing facilities.

  1. ORNL Neutron Sciences Annual Report for 2007

    SciTech Connect

    Anderson, Ian S; Horak, Charlie M; Counce, Deborah Melinda; Ekkebus, Allen E

    2008-07-01

    This is the first annual report of the Oak Ridge National Laboratory Neutron Sciences Directorate for calendar year 2007. It describes the neutron science facilities, current developments, and future plans; highlights of the year's activities and scientific research; and information on the user program. It also contains information about education and outreach activities and about the organization and staff. The Neutron Sciences Directorate is responsible for operation of the High Flux Isotope Reactor and the Spallation Neutron Source. The main highlights of 2007 were highly successful operation and instrument commissioning at both facilities. At HFIR, the year began with the reactor in shutdown mode and work on the new cold source progressing as planned. The restart on May 16, with the cold source operating, was a significant achievement. Furthermore, measurements of the cold source showed that the performance exceeded expectations, making it one of the world's most brilliant sources of cold neutrons. HFIR finished the year having completed five run cycles and 5,880 MWd of operation. At SNS, the year began with 20 kW of beam power on target; and thanks to a highly motivated staff, we reached a record-breaking power level of 183 kW by the end of the year. Integrated beam power delivered to the target was 160 MWh. Although this is a substantial accomplishment, the next year will bring the challenge of increasing the integrated beam power delivered to 887 MWh as we chart our path toward 5,350 MWh by 2011.

  2. Advanced Neutron Source (ANS) Project progress report

    SciTech Connect

    McBee, M.R.; Chance, C.M. ); Selby, D.L.; Harrington, R.M.; Peretz, F.J. )

    1990-04-01

    This report discusses the following topics on the advanced neutron source: quality assurance (QA) program; reactor core development; fuel element specification; corrosion loop tests and analyses; thermal-hydraulic loop tests; reactor control concepts; critical and subcritical experiments; material data, structural tests, and analysis; cold source development; beam tube, guide, and instrument development; hot source development; neutron transport and shielding; I C research and development; facility concepts; design; and safety.

  3. REACTOR MODERATOR STRUCTURE

    DOEpatents

    Greenstreet, B.L.

    1963-12-31

    A system for maintaining the alignment of moderator block structures in reactors is presented. Integral restraining grids are placed between each layer of blocks in the moderator structure, at the top of the uppermost layer, and at the bottom of the lowermost layer. Slots are provided in the top and bottom surfaces of the moderator blocks so as to provide a keying action with the grids. The grids are maintained in alignment by vertical guiding members disposed about their peripheries. (AEC)

  4. The DAMPE Neutron Detector

    NASA Astrophysics Data System (ADS)

    Yan, Zhang; Tao, Ma; Yongyi, Huang

    2016-07-01

    The first Chinese space observatory DAMPE (DArk Matter Particle Explorer) was successfully launched on Dec. 17th, 2015. One major scientific object of DAMPE is to measure electrons between 5GeV to 10TeV with excellent energy resolution (1.5% at 800GeV) to search for possible dark matter signatures. The detector consists of four subsystems: a plastic scintillator detector (PSD), a silicon-tungsten tracker (STK), a BGO calorimeter (BGO), and a neutron detector (NUD). The NUD on board DAMPE is designed to detect moderated neutrons via the boron capture of thermal neutrons in boron-doped plastics. Given the fact that hadron showers initiated in the BGO calorimeter by incident nuclei tend to be followed by significantly more neutron activities comparing to electromagnetic cascades triggered by electrons, the NUD provides an additional order of magnitude hadron rejection capability to improve the overall e/p discrimination of DAMPE up to 10 ^{5}. Preliminary analysis of the in-orbit data is given, together with comparisons to the results obtained by a detailed GEANT4 simulation of the NUD instrument.

  5. 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.

  6. From x-ray telescopes to neutron focusing

    NASA Astrophysics Data System (ADS)

    Gubarev, Mikhail V.; Khaykovich, Boris; Ramsey, Brian; Moncton, David; Zavlin, Vyacheslav E.; Kilaru, Kiranmayee; Romaine, Suzanne; Rosati, Richard E.; Bruni, Ricardo; Robertson, Lee; Crow, Lowell; Ambaye, Haile; Lauter, Valeria

    2011-09-01

    In the case of neutrons the refractive index is slightly less than unity for most elements and their isotopes [1]. Consequently, thermal and cold neutrons can be reflected from smooth surfaces at grazing-incidence angles. Hence, the optical technologies developed for x-ray astronomy can be applied for neutron focusing. The focusing capabilities of grazing incidence neutron imaging optics have been successfully demonstrated using nickel mirrors. The mirrors were fabricated using an electroformed nickel replication process at Marshall Space Flight Center. Results of the neutron optics experiments and current status of the multilayer coating replication technique development are presented.

  7. Neutron multiplicity ,easurements With 3He alternative: Straw neutron detectors

    DOE PAGES

    Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.; Detweiler, Ryan; Maurer, Richard J.; Mitchell, Stephen E.; Guss, Paul P.; Lacy, Jeffrey L.; Sun, Liang; Athanasiades, Athanasios

    2015-01-27

    neutron multiplicity information from spontaneous fission sources using a single panel consisting of 60 straws equally distributed over three rows in high-density polyethylene moderator. In the following year, we developed the field-programmable gate array and associated DAQ software. Finally, this SDRD effort successfully produced a prototype NMC with ~33% detection efficiency compared to a commercial fission meter.« less

  8. The performance of neutron scattering spectrometers at a long-pulse spallation source

    SciTech Connect

    Pynn, R.

    1997-06-01

    In this document the author considers the performance of a long pulse spallation source for those neutron scattering experiments that are usually performed with a monochromatic beam at a continuous wave (CW) source such as a nuclear reactor. The first conclusion drawn is that comparison of the performance of neutron scattering spectrometers at CW and pulsed sources is simpler for long-pulsed sources than it is for the short-pulse variety. Even though detailed instrument design and assessment will require Monte Carlo simulations (which have already been performed at Los Alamos for SANS and reflectometry), simple arguments are sufficient to assess the approximate performance of spectrometers at an LPSS and to support the contention that a 1 MW long-pulse source can provide attractive performance, especially for instrumentation designed for soft-condensed-matter science. Because coupled moderators can be exploited at such a source, its time average cold flux is equivalent to that of a research reactor with a power of about 15 MW, so only a factor of 4 gain from source pulsing is necessary to obtain performance that is comparable with the ILL. In favorable cases, the gain from pulsing can be even more than this, approaching the limit set by the peak flux, giving about 4 times the performance of the ILL. Because of its low duty factor, an LPSS provides the greatest performance gains for relatively low resolution experiments with cold neutrons. It should thus be considered complementary to short pulse sources which are most effective for high resolution experiments using thermal or epithermal neutrons.

  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. NIST Calibration of a Neutron Spectrometer ROSPEC.

    PubMed

    Heimbach, Craig

    2006-01-01

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

  11. NIST Calibration of a Neutron Spectrometer ROSPEC

    PubMed Central

    Heimbach, Craig

    2006-01-01

    A neutron spectrometer was acquired for use in the measurement of National Institute of Standards and Technology neutron fields. The spectrometer included options for the measurement of low and high energy neutrons, for a total measurement range from 0.01 eV up to 17 MeV. The spectrometer was evaluated in calibration fields and was used to determine the neutron spectrum of an Americium-Beryllium neutron source. The calibration fields used included bare and moderated 252Cf, monoenergetic neutron fields of 2.5 MeV and 14 MeV, and a thermal-neutron beam. Using the calibration values determined in this exercise, the spectrometer gives a good approximation of the neutron spectrum, and excellent values for neutron fluence, for all NIST calibration fields. The spectrometer also measured an Americium-Beryllium neutron field in a NIST exposure facility and determined the field quite well. The spectrometer measured scattering effects in neutron spectra which previously could be determined only by calculation or integral measurements. PMID:27274944

  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. Operational status of the Los Alamos neutron science center (LANSCE)

    SciTech Connect

    Jones, Kevin W; Erickson, John L; Schoenberg, Kurt F

    2010-01-01

    The Los Alamos Neutron Science Center (LANSCE) accelerator and beam delivery complex generates the proton beams that serve three neutron production sources; the thermal and cold source for the Manuel Lujan Jr. Neutron Scattering Center, the Weapons Neutron Research (WNR) high-energy neutron source, and a pulsed Ultra-Cold Neutron Source. These three sources are the foundation of strong and productive multi-disciplinary research programs that serve a diverse and robust user community. The facility also provides multiplexed beams for the production of medical radioisotopes and proton radiography of dynamic events. The recent operating history of these sources will be reviewed and plans for performance improvement will be discussed, together with the underlying drivers for the proposed LANSCE Refurbishment project. The details of this latter project are presented in a separate contribution.

  14. Code requirements document: MODFLOW 2. 1: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F. . Dept. of Nuclear Engineering); Paik, I.K. )

    1992-03-01

    Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation of the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event of safety rod failure. The MODFLOW code discussed here provides transient moderator flow pattern information with stratification effects, and tracks the location of ink plumes in the reactor. The code, written in Fortran, is compiled for Macintosh II computers, and includes subroutines for interactive control and graphical output. Removing the graphics capabilities, the code can also be compiled on other computers. With graphics, in addition to the capability to perform safety related computations, MODFLOW also provides an easy tool for becoming familiar with flow distributions in SRS reactors.

  15. MODFLOW 2.0: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F.; Paik, I.K.

    1991-07-01

    Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event of safety rod failure. The MODFLOW code discussed here provides transient moderator flow pattern information with stratification effects, and tracks the location of ink plumes in the reactor. The code, written in Fortran, is compiled for Macintosh II computers, and includes subroutines for interactive control and graphical output. Removing the graphics capabilities, the code can also be compiled on other computers. With graphics, in addition to the capability to perform safety related computations, MODFLOW also provides an easy tool for becoming familiar with flow distributions in SRS reactors.

  16. Code requirements document: MODFLOW 2.1: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F.; Paik, I.K.

    1992-03-01

    Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation of the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event of safety rod failure. The MODFLOW code discussed here provides transient moderator flow pattern information with stratification effects, and tracks the location of ink plumes in the reactor. The code, written in Fortran, is compiled for Macintosh II computers, and includes subroutines for interactive control and graphical output. Removing the graphics capabilities, the code can also be compiled on other computers. With graphics, in addition to the capability to perform safety related computations, MODFLOW also provides an easy tool for becoming familiar with flow distributions in SRS reactors.

  17. Prediction analysis of dose equivalent responses of neutron dosemeters used at a MOX fuel facility.

    PubMed

    Tsujimura, N; Yoshida, T; Takada, C

    2011-07-01

    To predict how accurately neutron dosemeters can measure the neutron dose equivalent (rate) in MOX fuel fabrication facility work environments, the dose equivalent responses of neutron dosemeters were calculated by the spectral folding method. The dosemeters selected included two types of personal dosemeter, namely a thermoluminescent albedo neutron dosemeter and an electronic neutron dosemeter, three moderator-based neutron survey meters, and one special instrument called an H(p)(10) monitor. The calculations revealed the energy dependences of the responses expected within the entire range of neutron spectral variations observed in neutron fields at workplaces. PMID:21498409

  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. Spectrum tailoring of the neutron energy spectrum in the context of delayed neutron detection

    SciTech Connect

    Koehler, William E; Tobin, Steve J; Sandoval, Nathan P; Fensin, Mike L

    2010-01-01

    For the purpose of measuring plutonium mass in spent fuel, a delayed neutron instrument is of particular interest since, if properly designed, the delayed neutron signal from {sup 235}U is significantly stronger than the signature from {sup 239}Pu or {sup 241}Pu. A key factor in properly designing a delayed neutron instrument is to minimize the fission of {sup 238}U. This minimization is achieved by keeping the interrogating neutron spectrum below {approx} 1 MeV. In the context of spent fuel measurements it is desirable to use a 14 MeV (deuterium and tritium) neutron generator for economic reasons. Spectrum tailoring is the term used to describe the inclusion of material between the 14 MeV neutrons and the interrogated object that lower the neutron energy through nuclear reactions and moderation. This report quantifies the utility of different material combination for spectrum tailoring.

  20. Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

    NASA Astrophysics Data System (ADS)

    Ikeda, Yoshimasa; Taketani, Atsushi; Takamura, Masato; Sunaga, Hideyuki; Kumagai, Masayoshi; Oba, Yojiro; Otake, Yoshie; Suzuki, Hiroshi

    2016-10-01

    A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by a large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 min. The minimum resolution of the 110 reflection for RANS is approximately 2.5% at 8 μs of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 μs, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time by decreasing a thickness of the moderator or by applying the decoupler system or application of the angular dispersive neutron diffraction technique are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenitic phase in the dual phase mock specimen was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS has been proved to be capable for neutron engineering diffraction aiming for the easy access

  1. High Intensity, Pulsed, D-D Neutron Generator

    SciTech Connect

    Williams, D. L.; Vainionpaa, J. H.; Jones, G.; Piestrup, M. A.; Gary, C. K.; Harris, J. L.; Fuller, M. J.; Cremer, J. T.; Ludewigt, Bernhard A.; Kwan, J. W.; Reijonen, J.; Leung, K.-N.; Gough, R. A.

    2008-08-01

    Single ion-beam RF-plasma neutron generators are presented as a laboratory source of intense neutrons. The continuous and pulsed operations of such a neutron generator using the deuterium-deuterium fusion reaction are reported. The neutron beam can be pulsed by switching the RF plasma and/or a gate electrode. These generators are actively vacuum pumped so that a continuous supply of deuterium gas is present for the production of ions and neutrons. This contributes to the generator's long life. These single-beam generators are capable of producing up to 1E10 n/s. Previously, Adelphi and LBNL have demonstrated these generators' applications in fast neutron radiography, Prompt Gamma Neutron Activation Analysis (PGNAA) and Neutron Activation Analysis (NAA). Together with an inexpensive compact moderator, these high-output neutron generators extend useful applications to home laboratory operations.

  2. On the effect of an error in a standard D2O-moderated 252Cf energy spectrum.

    PubMed

    Cummings, F M

    2009-12-01

    There appears to be an error in the neutron fluence for neutrons with energies between 9 and 10 MeV for the tabulated D2O-moderated Cf source in ISO 8529-1. If the referenced spectrum is used as tabulated, the error contributes a total error to neutron dose values from this source of approximately 3%.

  3. On the Effect of an Error in a Standard D2O-Moderated 252Cf Energy Spectrum

    SciTech Connect

    Frederick Cummings

    2009-12-01

    There appears to be an error in the neutron fluence for neutrons with energies between 9 and 10 MeV for the tabulated D2O-moderated 252Cf source in ISO 8529-1. The error contributes a total error to neutron dose values from this source of approximately 3%.

  4. NEUTRONIC REACTOR CONSTRUCTION

    DOEpatents

    Vernon, H.C.; Goett, J.J.

    1958-09-01

    A cover device is described for the fuel element receiving tube of a neutronic reactor of the heterogeneous, water cooled type wherein said tubes are arranged in a moderator with their longitudinal axes vertical. The cover is provided with means to support a rod-type fuel element from the bottom thereof and means to lock the cover in place, the latter being adapted for remote operation. This cover device is easily removable and seals the opening in the upper end of the fuel tube against leakage of coolant.

  5. Biological imaging with a neutron microscope

    SciTech Connect

    Cremer, J.T.; Piestrup, M.A.; Gary, C.K.; Pantell, R.H.; Glinka, C.J.

    2004-07-19

    A simple microscope employing a compound refractive lens (CRL) composed of 100 biconcave lenses was used to image a biological sample with a 9.4x magnification using 10 A ring cold neutrons. The microscope's resolution, 0.5 mm, was primarily determined by the neutron detector 5.0 mm pixel size. Unlike previous work the CRL's field of view was large (44 mm) and increased as the distance between the exit of neutron-waveguide and the specimen decreased. Short source-to-specimen distances allowed the 1.2-cm-diam CRL to view a biological sample with this field of view.

  6. A New Method of Neutron Detecton for UCN Lifetime Measrements

    SciTech Connect

    Morris, C. L.; Salvat, D. J.; Adamek, E. R.; Bowman, D.; Clayton, S.; Cude, C.; Fox, W.; Hogan, G.; Hickerson, K.; Holley, A. T.; Liu, C.-Y.; Makela, M.; Manus, G.; Penttila, S.; Ramsey, J.; Saunders, A.; Sawtelle, S.; Seestrom, S. J.; Solberg, K.; Vanderwerp, J.; VornDick, B.; Walstrom, P.; Wang, Z.; Young, A. R.

    2014-01-01

    A number of inconsistant neutron lifetime measurements have been reported. The disagreement among the various measurements made with material neutron traps with ultra-cold neutrons (UCN) suggests unaccounted for systematic errors in these measurements. One potential source of error is due to the long emptying times which may be time dependent due to the UCN phase space evolution in the trap. We present a way to reduce this effect.

  7. Thermal neutron calibration channel at LNMRI/IRD.

    PubMed

    Astuto, A; Salgado, A P; Leite, S P; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

    2014-10-01

    The Brazilian Metrology Laboratory of Ionizing Radiations (LNMRI) standard thermal neutron flux facility was designed to provide uniform neutron fluence for calibration of small neutron detectors and individual dosemeters. This fluence is obtained by neutron moderation from four (241)Am-Be sources, each with 596 GBq, in a facility built with blocks of graphite/paraffin compound and high-purity carbon graphite. This study was carried out in two steps. In the first step, simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The quality of the resulting neutron fluence in terms of spectrum, cadmium ratio and gamma-neutron ratio was evaluated. In the second step, the system was assembled based on the results obtained on the simulations, and new measurements are being made. These measurements will validate the system, and other intercomparisons will ensure traceability to the International System of Units.

  8. Thermal neutron calibration channel at LNMRI/IRD.

    PubMed

    Astuto, A; Salgado, A P; Leite, S P; Patrão, K C S; Fonseca, E S; Pereira, W W; Lopes, R T

    2014-10-01

    The Brazilian Metrology Laboratory of Ionizing Radiations (LNMRI) standard thermal neutron flux facility was designed to provide uniform neutron fluence for calibration of small neutron detectors and individual dosemeters. This fluence is obtained by neutron moderation from four (241)Am-Be sources, each with 596 GBq, in a facility built with blocks of graphite/paraffin compound and high-purity carbon graphite. This study was carried out in two steps. In the first step, simulations using the MCNPX code on different geometric arrangements of moderator materials and neutron sources were performed. The quality of the resulting neutron fluence in terms of spectrum, cadmium ratio and gamma-neutron ratio was evaluated. In the second step, the system was assembled based on the results obtained on the simulations, and new measurements are being made. These measurements will validate the system, and other intercomparisons will ensure traceability to the International System of Units. PMID:24625545

  9. CR-39 detector based thermal neutron flux measurements, in the photo neutron project

    NASA Astrophysics Data System (ADS)

    Mameli, A.; Greco, F.; Fidanzio, A.; Fusco, V.; Cilla, S.; D'Onofrio, G.; Grimaldi, L.; Augelli, B. G.; Giannini, G.; Bevilacqua, R.; Totaro, P.; Tommasino, L.; Azario, L.; Piermattei, A.

    2008-08-01

    PhoNeS (photo neutron source) is a project aimed at the production and moderation of neutrons by exploiting high energy linear accelerators, currently used in radiotherapy. A feasibility study has been carried out with the scope in mind to use the high energy photon beams from these accelerators for the production of neutrons suitable for boron neutron capture therapy (BNCT). Within these investigations, it was necessary to carry out preliminary measurements of the thermal neutron component of neutron spectra, produced by the photo-conversion of X-ray radiotherapy beams supplied by three LinAcs: 15 MV, 18 MV and 23 MV. To this end, a simple passive thermal neutron detector has been used which consists of a CR-39 track detector facing a new type of boron-loaded radiator. Once calibrated, this passive detector has been used for the measurement of both the thermal neutron component and the cadmium ratio of different neutron spectra. In addition, bubble detectors with a response highly sensitive to thermal neutrons have also been used. Both thermal neutron detectors are simple to use, very compact and totally insensitive to low-ionizing radiation such as electrons and X-rays. The resultant thermal neutron flux was above 10 6 n/cm 2s and the cadmium ratio was no greater than 15 for the first attempt of photo-conversion of X-ray radiotherapy beams.

  10. 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

  11. Cold Stress and the Cold Pressor Test

    ERIC Educational Resources Information Center

    Silverthorn, Dee U.; Michael, Joel

    2013-01-01

    Temperature and other environmental stressors are known to affect blood pressure and heart rate. In this activity, students perform the cold pressor test, demonstrating increased blood pressure during a 1- to 2-min immersion of one hand in ice water. The cold pressor test is used clinically to evaluate autonomic and left ventricular function. This…

  12. Advancing Materials Science using Neutrons at Oak Ridge National Laboratory

    SciTech Connect

    Carpenter, John

    2014-04-24

    Jack Carpenter, pioneer of accelerator-based pulsed spallation neutron sources, talks about neutron science at Oak Ridge National Laboratory (ORNL) and a need for a second target station at the Spallation Neutron Source (SNS). ORNL is the Department of Energy's largest multiprogram science and energy laboratory, and is home to two scientific user facilities serving the neutron science research community: the High Flux Isotope Reactor (HFIR) and SNS. HFIR and SNS provide researchers with unmatched capabilities for understanding the structure and properties of materials, macromolecular and biological systems, and the fundamental physics of the neutron. Neutrons provide a window through which to view materials at a microscopic level that allow researchers to develop better materials and better products. Neutrons enable us to understand materials we use in everyday life. Carpenter explains the need for another station to produce long wavelength neutrons, or cold neutrons, to answer questions that are addressed only with cold neutrons. The second target station is optimized for that purpose. Modern technology depends more and more upon intimate atomic knowledge of materials, and neutrons are an ideal probe.

  13. Advancing Materials Science using Neutrons at Oak Ridge National Laboratory

    ScienceCinema

    Carpenter, John

    2016-07-12

    Jack Carpenter, pioneer of accelerator-based pulsed spallation neutron sources, talks about neutron science at Oak Ridge National Laboratory (ORNL) and a need for a second target station at the Spallation Neutron Source (SNS). ORNL is the Department of Energy's largest multiprogram science and energy laboratory, and is home to two scientific user facilities serving the neutron science research community: the High Flux Isotope Reactor (HFIR) and SNS. HFIR and SNS provide researchers with unmatched capabilities for understanding the structure and properties of materials, macromolecular and biological systems, and the fundamental physics of the neutron. Neutrons provide a window through which to view materials at a microscopic level that allow researchers to develop better materials and better products. Neutrons enable us to understand materials we use in everyday life. Carpenter explains the need for another station to produce long wavelength neutrons, or cold neutrons, to answer questions that are addressed only with cold neutrons. The second target station is optimized for that purpose. Modern technology depends more and more upon intimate atomic knowledge of materials, and neutrons are an ideal probe.

  14. 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.

  15. Plastic fiber scintillator response to fast neutrons

    SciTech Connect

    Danly, C. R.; Sjue, S.; Wilde, C. H.; Merrill, F. E.; Haight, R. C.

    2014-11-15

    The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

  16. Cold and Cough Medicines

    MedlinePlus

    ... What can you do for your cold or cough symptoms? Besides drinking lots of fluids and getting ... medicines. There are lots of different cold and cough medicines, and they do different things. Nasal decongestants - ...

  17. Cold knife cone biopsy

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/003910.htm Cold knife cone biopsy To use the sharing features on this page, please enable JavaScript. A cold knife cone biopsy (conization) is surgery to remove ...

  18. Cold Sores (Orofacial Herpes)

    MedlinePlus

    ... rash and rashes clinical tools newsletter | contact Share | Cold Sores (Orofacial Herpes) Information for adults A A ... face, known as orofacial herpes simplex, herpes labialis, cold sores, or fever blisters, is a common, recurrent ...

  19. Accelerator based epithermal neutron source for neutron capture therapy. Annual report, [October 1990--April 1991

    SciTech Connect

    Brugger, R.; Kunze, J.

    1991-05-01

    Several investigators have suggested that a charged particle accelerator with light element reactions might be able to produce enough epithermal neutrons to be useful in Neutron Capture Therapy. The reaction choice so far has been the Li(p,n) reaction with protons up to 2.5 MeV. A moderator around the target would reduce the faster neutrons down to the epithermal energy region. The goals of the present research are: identify better reactions; improve the moderators; and find better combinations of 1 and 2. The target is to achieve, at the patient location, an epithermal neutron current of greater than 10{sup 9}n/cm{sup 2}sec, with a dose to tissue from the neutrons alone of less than 10{sup {minus}10} rads/n and a dose from the gamma rays in the beam of less than 10{sup {minus}10} rads/n.

  20. The neutron imaging diagnostic at NIF (invited).

    PubMed

    Merrill, F E; Bower, D; Buckles, R; Clark, D D; Danly, C R; Drury, O B; Dzenitis, J M; Fatherley, V E; Fittinghoff, D N; Gallegos, R; Grim, G P; Guler, N; Loomis, E N; Lutz, S; Malone, R M; Martinson, D D; Mares, D; Morley, D J; Morgan, G L; Oertel, J A; Tregillis, I L; Volegov, P L; Weiss, P B; Wilde, C H; Wilson, D C

    2012-10-01

    A neutron imaging diagnostic has recently been commissioned at the National Ignition Facility (NIF). This new system is an important diagnostic tool for inertial fusion studies at the NIF for measuring the size and shape of the burning DT plasma during the ignition stage of Inertial Confinement Fusion (ICF) implosions. The imaging technique utilizes a pinhole neutron aperture, placed between the neutron source and a neutron detector. The detection system measures the two dimensional distribution of neutrons passing through the pinhole. This diagnostic has been designed to collect two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically the first image measures the distribution of the 14 MeV neutrons and the second image of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core.

  1. Neutron Spectroscopy on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.

    2012-10-01

    The performance of cryogenic fuel implosion experiments in progress at the National Ignition Facility (NIF) is measured by an experimental threshold factorfootnotetextM. J. Edwards et al., Phys. Plasmas 18, 051003 (2011). (ITFX) and a generalized Lawson Criterion.footnotetextC. D. Zhou and R. Betti, Phys. Plasmas 15, 102707 (2008); P. Y. Chang et al., Phys. Rev. Lett. 104, 135002 (2010); and R. Betti et al., Phys. Plasmas 17, 058102 (2010). The ITFX metric is determined by the fusion yield and the areal density of an assembled deuterium-tritium (DT) fuel mass. Typical neutron yields from NIF implosions are greater than 10^14 allowing the neutron energy spectrum to be measured with unprecedented precision. A NIF spectrum is composed of neutrons created by fusion (DT, DD, and TT reactions) and neutrons scattered by the dense, cold fuel layer. Neutron scattering is used to determine the areal density of a NIF implosion and is measured along four lines of sight by two neutron time-of-flight detectors, a neutron imaging system, and the magnetic recoil spectrometer. An accurate measurement of the instrument response function for these detectors allows for the routine production of neutron spectra showing DT fuel areal densities up to 1.3 g/cm^2. Spectra over neutron energies of 10 to 17 MeV show areal-density asymmetries of 20% that are inconsistent with simulations. New calibrations and analyses have expended the spectral coverage down to energies less than the deuterium backscatter edge (1.5 MeV for 14 MeV neutrons). These data and analyses are presented along with a compilation of other nuclear diagnostic data that show a larger-than-expected variation in the areal density over the cold fuel mass. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No DE-FC52-08NA28302. In collaboration with NIC.

  2. NEUTRONIC REACTOR

    DOEpatents

    Wade, E.J.

    1958-09-16

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

  3. Cyclotron-based neutron source for BNCT

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  4. Cyclotron-based neutron source for BNCT

    SciTech Connect

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

    2013-04-19

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

  5. [Assessment on the yield loss risk of longan caused by cold damage in South China].

    PubMed

    Zhao, Jun-fang; Yu, Hui-kang

    2016-02-01

    Using daily climate variables gathered from 64 meteorological stations in South China from 1961 to 2012, recognized hazard indicators about disaster grades of cold damage for longan, and methods on agricultural meteorological disasters risk and simulation technology, the yield loss risks of longan caused by cold damage in South China during different developmental periods were assessed. The results showed that during the period of physiologic differentiation of flower bud, the disasters of longan affected by mild cold damage in South China were the most common, followed by severe cold damage and moderate cold damage. The hazards caused by cold damage under different grades varied. In particular, under mild cold damage, light disaster of longan was found in Fujian, followed by Guangdong and Hainan, and Guangxi was serious. Under moderate cold damage, light disaster of longan was found in Hainan, followed by Guangdong and Guangxi, and Fujian was serious. Under severe cold damage, light disaster of longan was found in Hainan, followed by Guangdong and Guangxi, Fujian was serious. During the period of morphologic differentiation of flower bud, the disasters of longan affected by mild cold damage in South China were the most common, followed by severe cold damage and moderate cold damage, while the disasters of longan under mild, moderate and severe cold damages within this period were similar. Specifically, light disasters of longan were all found in Hainan, followed by Guangdong, Guangxi and Fujian. During the period of dormancy, the disaster of longan affected by mild cold damage in South China was the most common, followed by severe cold damage and moderate cold damage. Under mild and severe cold damage, light disaster of longan was found in Fujian, followed by Guangdong and Hainan, and Guangxi was serious. However, under moderate cold damage, light disaster of longan was found in Hainan and Guangxi, followed by Guangdong, and Fujian was serious. At the same level

  6. [Assessment on the yield loss risk of longan caused by cold damage in South China].

    PubMed

    Zhao, Jun-fang; Yu, Hui-kang

    2016-02-01

    Using daily climate variables gathered from 64 meteorological stations in South China from 1961 to 2012, recognized hazard indicators about disaster grades of cold damage for longan, and methods on agricultural meteorological disasters risk and simulation technology, the yield loss risks of longan caused by cold damage in South China during different developmental periods were assessed. The results showed that during the period of physiologic differentiation of flower bud, the disasters of longan affected by mild cold damage in South China were the most common, followed by severe cold damage and moderate cold damage. The hazards caused by cold damage under different grades varied. In particular, under mild cold damage, light disaster of longan was found in Fujian, followed by Guangdong and Hainan, and Guangxi was serious. Under moderate cold damage, light disaster of longan was found in Hainan, followed by Guangdong and Guangxi, and Fujian was serious. Under severe cold damage, light disaster of longan was found in Hainan, followed by Guangdong and Guangxi, Fujian was serious. During the period of morphologic differentiation of flower bud, the disasters of longan affected by mild cold damage in South China were the most common, followed by severe cold damage and moderate cold damage, while the disasters of longan under mild, moderate and severe cold damages within this period were similar. Specifically, light disasters of longan were all found in Hainan, followed by Guangdong, Guangxi and Fujian. During the period of dormancy, the disaster of longan affected by mild cold damage in South China was the most common, followed by severe cold damage and moderate cold damage. Under mild and severe cold damage, light disaster of longan was found in Fujian, followed by Guangdong and Hainan, and Guangxi was serious. However, under moderate cold damage, light disaster of longan was found in Hainan and Guangxi, followed by Guangdong, and Fujian was serious. At the same level

  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. High resolution neutron imaging capabilities at BOA beamline at Paul Scherrer Institut

    NASA Astrophysics Data System (ADS)

    Tremsin, A. S.; Morgano, M.; Panzner, T.; Lehmann, E.; Filgers, U.; Vallerga, J. V.; McPhate, J. B.; Siegmund, O. H. W.; Feller, W. B.

    2015-06-01

    The cold neutron spectrum of the Beamline for neutron Optics and other Applications (BOA) at Paul Scherrer Institut enables high contrast neutron imaging because neutron cross sections for many materials increase with neutron wavelength. However, for many neutron imaging applications, spatial resolution can be as important as contrast. In this paper the neutron transmission imaging capabilities of an MCP/Timepix detector installed at the BOA beamline are presented, demonstrating the possibilities for studying sub-20 μm features in various samples. In addition to conventional neutron radiography and microtomography, the high degree of neutron polarization at the BOA beamline can be very attractive for imaging of magnetic fields, as demonstrated by our measurements. We also show that a collimated cold neutron beamline combined with a high resolution detector can produce image artifacts, (e.g. edge enhancements) due to neutron refraction and scattering. The results of our experiments indicate that the BOA beamline is a valuable addition to neutron imaging facilities, providing improved and sometimes unique capabilities for non-destructive studies with cold neutrons.

  9. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  10. Cold Fronts in Cold Dark Matter Clusters

    NASA Astrophysics Data System (ADS)

    Nagai, Daisuke; Kravtsov, Andrey V.

    2003-04-01

    Recently, high-resolution Chandra observations revealed the existence of very sharp features in the X-ray surface brightness and temperature maps of several clusters. These features, called cold fronts, are characterized by an increase in surface brightness by a factor >~2 over 10-50 kpc accompanied by a drop in temperature of a similar magnitude. The existence of such sharp gradients can be used to put interesting constraints on the physics of the intracluster medium (ICM) if their mechanism and longevity are well understood. Here, we present results of a search for cold fronts in high-resolution simulations of galaxy clusters in cold dark matter models. We show that sharp gradients with properties similar to those of observed cold fronts naturally arise in cluster mergers when the shocks heat gas surrounding the merging subcluster, while its dense core remains relatively cold. The compression induced by supersonic motions and shock heating during the merger enhance the amplitude of gas density and temperature gradients across the front. Our results indicate that cold fronts are nonequilibrium transient phenomena and can be observed for a period of less than a billion years. We show that the velocity and density fields of gas surrounding the cold front can be very irregular, which would complicate analyses aiming to put constraints on the physical conditions of the ICM in the vicinity of the front.

  11. New thermal neutron scattering files for ENDF/B-VI release 2

    SciTech Connect

    MacFarlane, R.E.

    1994-03-01

    At thermal neutron energies, the binding of the scattering nucleus in a solid, liquid, or gas affects the cross section and the distribution of secondary neutrons. These effects are described in the thermal sub-library of Version VI of the Evaluated Nuclear Data Files (ENDF/B-VI) using the File 7 format. In the original release of the ENDF/B-VI library, the data in File 7 were obtained by converting the thermal scattering evaluations of ENDF/B-III to the ENDF-6 format. These original evaluations were prepared at General Atomics (GA) in the late sixties, and they suffer from accuracy limitations imposed by the computers of the day. This report describes new evaluations for six of the thermal moderator materials and six new cold moderator materials. The calculations were made with the LEAPR module of NJOY, which uses methods based on the British code LEAP, together with the original GA physics models, to obtain new ENDF files that are accurate over a wider range of energy and momentum transfer than the existing files. The new materials are H in H{sub 2}O, Be metal, Be in BeO, C in graphite, H in ZrH, Zr in ZrH, liquid ortho-hydrogen, liquid para-hydrogen, liquid ortho-deuterium, liquid para-deuterium liquid methane, and solid methane.

  12. Neutron Imaging Developments at LANSCE

    NASA Astrophysics Data System (ADS)

    Nelson, Ron; Hunter, James; Schirato, Richard; Vogel, Sven; Swift, Alicia; Ickes, Tim; Ward, Bill; Losko, Adrian; Tremsin, Anton

    2015-10-01

    Neutron imaging is complementary to x-ray imaging because of its sensitivity to light elements and greater penetration of high-Z materials. Energy-resolved neutron imaging can provide contrast enhancements for elements and isotopes due to the variations with energy in scattering cross sections due to nuclear resonances. These cross section differences exist due to compound nuclear resonances that are characteristic of each element and isotope, as well as broader resonances at higher energies. In addition, multi-probe imaging, such as combined photon and neutron imaging, is a powerful tool for discerning properties and features in materials that cannot be observed with a single probe. Recently, we have demonstrated neutron imaging, both radiography and computed tomography, using the moderated (Lujan Center) and high-energy (WNR facility) neutron sources at LANSCE. Flat panel x-ray detectors with suitable scintillator-converter screens provide good sensitivity for both low and high neutron energies. Micro-Channel-Plate detectors and iCCD scintillator camera systems that provide the fast time gating needed for energy-resolved imaging have been demonstrated as well. Examples of recent work will be shown including fluid flow in plants and imaging through dense thick objects. This work is funded by the US Department of Energy, National Nuclear Security Administration, and performed by Los Alamos National Security LLC under Contract DE-AC52-06NA25396.

  13. 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.

  14. FOREWORD: Neutron metrology Neutron metrology

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. High Intensity Neutron Beams for Small Samples

    NASA Astrophysics Data System (ADS)

    Böni, Peter

    2014-04-01

    As novel materials of excellent homogeneity can often only be grown in small quantities it is important to optimize the transport of neutrons from the moderator to the sample while keeping the background low. Using elliptically or parabolically tapered guides the losses can be strongly reduced such that 50% - 90% of the useful neutrons arrive at the sample. If not properly designed, however, the divergence at the sample becomes inhomogeneous. In contrast, pairs of nested Kirkpatrick-Baez mirrors in Montel geometry yield well focused beams with a compact phase space. The mirrors extract only the useful neutrons from the moderator and effectively interrupt the line of sight leading to a very low background. As the focal distances are typically several meters, the extraction of the neutrons and the installation of bulky sample environment is facilitated.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  17. Cough and Cold Medicine Abuse

    MedlinePlus

    ... and Cold Medicine Abuse DrugFacts: Cough and Cold Medicine Abuse Email Facebook Twitter Revised May 2014 Some ... diverted for abuse. How Are Cough and Cold Medicines Abused? Cough and cold medicines are usually consumed ...

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

    PubMed

    Lee, K W; Sheu, R J

    2015-04-01

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

  19. A clean, bright, and versatile source of neutron decay products

    NASA Astrophysics Data System (ADS)

    Dubbers, D.; Abele, H.; Baeßler, S.; Märkisch, B.; Schumann, M.; Soldner, T.; Zimmer, O.

    2008-11-01

    We present a case study on a new type of beam station for the measurement of angular correlations in the β-decay of free neutrons. This beam station, called proton and electron radiation channel (PERC), is a cold-neutron guide that delivers at its open end, instead of neutrons, a beam of electrons and protons from neutron decays that take place far inside the guide. These charged neutron-decay products are magnetically guided to the end of the neutron guide, where they are separated from the cold-neutron beam. In this way, a general-purpose source of neutron decay products is obtained which can be operated as a user facility for a variety of different experiments in neutron decay correlation spectroscopy that may be installed at this beam station. The angular distribution of the emitted charged particles depends on the magnetic field configuration and can be chosen freely, according to the need of the experiment being carried out. A gain in phase space density of several orders of magnitude can be achieved with PERC, as compared to existing neutron decay spectrometers. Detailed calculations show that the spectra and angular distributions of the emerging electrons and protons will be distortion- and background-free on the level of 10 -4, more than 10 times better than that achieved today.

  20. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1962-12-25

    A reactor is described comprising a plurality of horizontal trays containing a solution of a fissionable material, the trays being sleeved on a vertical tube which contains a vertically-reciprocable control rod, a gas-tight chamber enclosing the trays, and means for conducting vaporized moderator from the chamber and for replacing vaporized moderator in the trays. (AEC)

  1. NEUTRONIC REACTOR

    DOEpatents

    Daniels, F.

    1959-10-27

    A reactor in which at least a portion of the moderator is in the form of movable refractory balls is described. In addition to their moderating capacity, these balls may serve as carriers for fissionable material or fertile material, or may serve in a coolant capacity to remove heat from the reactor. A pneumatic system is used to circulate the balls through the reactor.

  2. NEUTRONIC REACTOR HAVING LOCALIZED AREAS OF HIGH THERMAL NEUTRON DENSITIES

    DOEpatents

    Newson, H.W.

    1958-06-01

    A nuclear reactor for the irradiation of materials designed to provide a localized area of high thermal neutron flux density in which the materials to be irradiated are inserted is described. The active portion of the reactor is comprised of a cubicle graphite moderator of about 25 feet in length along each axis which has a plurality of cylindrical channels for accommodatirg elongated tubular-shaped fuel elements. The fuel elements have radial fins for spacing the fuel elements from the channel walls, thereby providing spaces through which a coolant may be passed, and also to serve as a heatconductirg means. Ducts for accommnodating the sample material to be irradiated extend through the moderator material perpendicular to and between parallel rows of fuel channels. The improvement is in the provision of additional fuel element channels spaced midway between 2 rows of the regular fuel channels in the localized area surrounding the duct where the high thermal neutron flux density is desired. The fuel elements normally disposed in the channels directly adjacent the duct are placed in the additional channels, and the channels directly adjacent the duct are plugged with moderator material. This design provides localized areas of high thermal neutron flux density without the necessity of providing additional fuel material.

  3. GEANT4 used for neutron beam design of a neutron imaging facility at TRIGA reactor in Morocco

    NASA Astrophysics Data System (ADS)

    Ouardi, A.; Machmach, A.; Alami, R.; Bensitel, A.; Hommada, A.

    2011-09-01

    Neutron imaging has a broad scope of applications and has played a pivotal role in visualizing and quantifying hydrogenous masses in metallic matrices. The field continues to expand into new applications with the installation of new neutron imaging facilities. In this scope, a neutron imaging facility for computed tomography and real-time neutron radiography is currently being developed around 2.0MW TRIGA MARK-II reactor at Maamora Nuclear Research Center in Morocco (Reuscher et al., 1990 [1]; de Menezes et al., 2003 [2]; Deinert et al., 2005 [3]). The neutron imaging facility consists of neutron collimator, real-time neutron imaging system and imaging process systems. In order to reduce the gamma-ray content in the neutron beam, the tangential channel was selected. For power of 250 kW, the corresponding thermal neutron flux measured at the inlet of the tangential channel is around 3×10 11 ncm 2/s. This facility will be based on a conical neutron collimator with two circular diaphragms with diameters of 4 and 2 cm corresponding to L/D-ratio of 165 and 325, respectively. These diaphragms' sizes allow reaching a compromise between good flux and efficient L/D-ratio. Convergent-divergent collimator geometry has been adopted. The beam line consists of a gamma filter, fast neutrons filter, neutron moderator, neutron and gamma shutters, biological shielding around the collimator and several stages of neutron collimator. Monte Carlo calculations by a fully 3D numerical code GEANT4 were used to design the neutron beam line ( http://www.info.cern.ch/asd/geant4/geant4.html[4]). To enhance the neutron thermal beam in terms of quality, several materials, mainly bismuth (Bi) and sapphire (Al 2O 3) were examined as gamma and neutron filters respectively. The GEANT4 simulations showed that the gamma and epithermal and fast neutron could be filtered using the bismuth (Bi) and sapphire (Al 2O 3) filters, respectively. To get a good cadmium ratio, GEANT 4 simulations were used to

  4. Moderate views of abortion.

    PubMed

    Sumner, L W

    1997-01-01

    This essay offers a moderate view of abortion that imposes a time limit for unrestricted abortion and specific indications for later abortions. The introduction notes that the discussion will provide a defense for this policy based on a moral analysis but that other options for moderates, especially options provided by freestanding views (the defense of which does not rest on any prior commitment about the morality of abortion), will also be considered. The next section considers the moral status of the fetus grounded in a criterion of moral standing that stipulates the necessary characteristics to achieve moral standing. This discussion concludes that a fetus acquires moral standing only when it becomes sentient. Section 3 moves the argument from ethics to politics to prove that a moderate policy must place no limitations on abortion before the time the fetus becomes sentient because before that time the fetus has no interest for the state to protect. The final section notes that some pro-choice advocates may be happier with the moderate policy proposed than with its controversial defense based on the moral status of the fetus and that another defense of a moderate policy could be based on a finding that the ethical issue can not be decided and that no view about abortion ethics is more reasonable than any other. The essay concludes that the ethical debate is ultimately unavoidable. PMID:12348328

  5. How cold is cold dark matter?

    SciTech Connect

    Armendariz-Picon, Cristian; Neelakanta, Jayanth T. E-mail: jtneelak@syr.edu

    2014-03-01

    If cold dark matter consists of particles, these must be non-interacting and non-relativistic by definition. In most cold dark matter models however, dark matter particles inherit a non-vanishing velocity dispersion from interactions in the early universe, a velocity that redshifts with cosmic expansion but certainly remains non-zero. In this article, we place model-independent constraints on the dark matter temperature to mass ratio, whose square root determines the dark matter velocity dispersion. We only assume that dark matter particles decoupled kinetically while non-relativistic, when galactic scales had not entered the horizon yet, and that their momentum distribution has been Maxwellian since that time. Under these assumptions, using cosmic microwave background and matter power spectrum observations, we place upper limits on the temperature to mass ratio of cold dark matter today (away from collapsed structures). These limits imply that the present cold dark matter velocity dispersion has to be smaller than 54 m/s. Cold dark matter has to be quite cold, indeed.

  6. Calibration of neutron albedo dosemeters.

    PubMed

    Schwartz, R B; Eisenhauer, C M

    2002-01-01

    It is shown that by calibrating neutron albedo dosemeters under the proper conditions, two complicating effects will essentially cancel out, allowing accurate calibrations with no need for explicit corrections. The 'proper conditions' are: a large room (> or = 8 m on a side). use of a D2O moderated 252Cf source, and a source-to-phantom calibration distance of approximately 70 cm. PMID:12212898

  7. NEUTRONIC REACTOR COUNTER METHOD AND SYSTEM

    DOEpatents

    Graham, C.B.; Spiewak, I.

    1960-05-31

    An improved method is given for controlling the rate of fission in circulating-fuel neutronic reactors in which the fuel is a homogeneous liquid containing fissionable material and a neutron moderator. A change in the rate of flssion is effected by preferentially retaining apart from the circulating fuel a variable amount of either fissionable material or moderator, thereby varying the concentration of fissionable material in the fuel. In the case of an aqueous fuel solution a portion of the water may be continuously vaporized from the circulating solution and the amount of condensate, or condensate plus make-up water, returned to the solution is varied to control the fission rate.

  8. The Advanced Neutron Source (ANS) project: A world-class research reactor facility

    SciTech Connect

    Thompson, P.B.; Meek, W.E.

    1993-07-01

    This paper provides an overview of the Advanced Neutron Source (ANS), a new research facility being designed at Oak Ridge National Laboratory. The facility is based on a 330 MW, heavy-water cooled and reflected reactor as the neutron source, with a thermal neutron flux of about 7.5{times}10{sup 19}m{sup {minus}2}{center_dot}sec{sup {minus}1}. Within the reflector region will be one hot source which will serve 2 hot neutron beam tubes, two cryogenic cold sources serving fourteen cold neutron beam tubes, two very cold beam tubes, and seven thermal neutron beam tubes. In addition there will be ten positions for materials irradiation experiments, five of them instrumented. The paper touches on the project status, safety concerns, cost estimates and scheduling, a description of the site, the reactor, and the arrangements of the facilities.

  9. REACTOR MODERATOR STRUCTURE

    DOEpatents

    Fraas, A.P.; Tudor, J.J.

    1963-08-01

    An improved moderator structure for nuclear reactors consists of moderator blocks arranged in horizontal layers to form a multiplicity of vertically stacked columns of blocks. The blocks in each vertical column are keyed together, and a ceramic grid is disposed between each horizontal layer of blocks. Pressure plates cover- the lateral surface of the moderator structure in abutting relationship with the peripheral terminal lengths of the ceramic grids. Tubular springs are disposed between the pressure plates and a rigid external support. The tubular springs have their axes vertically disposed to facilitate passage of coolant gas through the springs and are spaced apart a selected distance such that at sonae preselected point of spring deflection, the sides of the springs will contact adjacent springs thereby causing a large increase in resistance to further spring deflection. (AEC)

  10. 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.

  11. Neutron Tube Design Study for Boron Neutron Capture TherapyApplication

    SciTech Connect

    Verbeke, J.M.; Lee, Y.; Leung, K.N.; Vujic, J.; Williams, M.D.; Wu, L.K.; Zahir, N.

    1998-01-04

    Radio-frequency (RF) driven ion sources are being developed in Lawrence Berkeley National Laboratory (LBNL) for sealed-accelerator-tube neutron generator application. By using a 5-cm-diameter RF-driven multicusp source H{sup +} yields over 95% have been achieved. These experimental findings will enable one to develop compact neutron generators based on the D-D or D-T fusion reactions. In this new neutron generator, the ion source, the accelerator and the target are all housed in a sealed metal container without external pumping. Recent moderator design simulation studies have shown that 14 MeV neutrons could be moderated to therapeutically useful energy ranges for boron neutron capture therapy (BNCT). The dose near the center of the brain with optimized moderators is about 65% higher than the dose obtained from a typical neutron spectrum produced by the Brookhaven Medical Research Reactor (BMRR), and is comparable to the dose obtained by other accelerator-based neutron sources. With a 120 keV and 1 A deuteron beam, a treatment time of {approx}35 minutes is estimated for BNCT.

  12. Neutron Damage and MAX Phase Ternary Compounds

    SciTech Connect

    Barsoum, Michael; Hoffman, Elizabeth; Sindelar, Robert; Garcua-Duaz, Brenda; Kohse, Gordon

    2014-06-17

    The Demands of Gen IV nuclear power plants for long service life under neutron radiation at high temperature are severe. Advanced materials that would withstand high temperatures (up to 1000+ C) to high doses in a neutron field would be ideal for reactor internal structures and would add to the long service life and reliability of the reactors. The objective of this work is to investigate the response of a new class of machinable, conductive, layered, ternary transition metal carbides and nitrides - the so-called MAX phases - to low and moderate neutron dose levels.

  13. Proton linacs for boron neutron capture therapy

    SciTech Connect

    Lennox, A.J. |

    1993-08-01

    Recent advances in the ability to deliver boron-containing drugs to brain tumors have generated interest in {approximately}4 MeV linacs as sources of epithermal neutrons for radiation therapy. In addition, fast neutron therapy facilities have been studying methods to moderate their beams to take advantage of the high cross section for epithermal neutrons on boron-10. This paper describes the technical issues involved in each approach and presents the motivation for undertaking such studies using the Fermilab linac. the problems which must be solved before therapy can begin are outlined. Status of preparatory work and results of preliminary measurements are presented.

  14. Assay of the Martian Regolith with Neutrons

    NASA Technical Reports Server (NTRS)

    Drake, Darrell M.; Reedy, R.; Jakowsky, B.; Clark, B.; Squyres, S.

    1998-01-01

    Different aspects of assaying Martian regolith using neutrons have been investigated. The epithermal portion of moderated neutrons spectra is dramatically effected by the presence of hydrogen (usually in the form of water). A simple analytic formula has been derived to describe the amplitude of this portion of the neutron spectrum as a function of water concentration. Several demonstration experiments have been performed and modeled with a Monte Carlo code. Results of these experiments generally agreed with the calculations to within 20%. In addition to He-3 detectors, lithium-glass scintillators and U-238 fission ion chambers were investigated to determine their applicability to space experiments.

  15. Designing accelerator-based epithermal neutron beams for boron neutron capture therapy

    SciTech Connect

    Bleuel, D.L. |; Donahue, R.J.; Ludewigt, B.A.; Vujic, J.

    1998-09-01

    The {sup 7}Li(p,n){sup 7}Be reaction has been investigated as an accelerator-driven neutron source for proton energies between 2.1 and 2.6 MeV. Epithermal neutron beams shaped by three moderator materials, Al/AlF{sub 3}, {sup 7}LiF, and D{sub 2}O, have been analyzed and their usefulness for boron neutron capture therapy (BNCT) treatments evaluated. Radiation transport through the moderator assembly has been simulated with the Monte Carlo {ital N}-particle code (MCNP). Fluence and dose distributions in a head phantom were calculated using BNCT treatment planning software. Depth-dose distributions and treatment times were studied as a function of proton beam energy and moderator thickness. It was found that an accelerator-based neutron source with Al/AlF{sub 3} or {sup 7}LiF as moderator material can produce depth-dose distributions superior to those calculated for a previously published neutron beam design for the Brookhaven Medical Research Reactor, achieving up to {approximately}50{percent} higher doses near the midline of the brain. For a single beam treatment, a proton beam current of 20 mA, and a {sup 7}LiF moderator, the treatment time was estimated to be about 40 min. The tumor dose deposited at a depth of 8 cm was calculated to be about 21 Gy-Eq. {copyright} {ital 1998 American Association of Physicists in Medicine.}

  16. Optimizing Neutron Thermal Scattering Effects in very High Temperature Reactors. Final Report

    SciTech Connect

    Hawari, Ayman; Ougouag, Abderrafi

    2014-07-08

    This project aims to develop a holistic understanding of the phenomenon of neutron thermalization in the VHTR. Neutron thermalization is dependent on the type and structure of the moderating material. The fact that the moderator (and reflector) in the VHTR is a solid material will introduce new and interesting considerations that do not apply in other (e.g. light water) reactors. The moderator structure is expected to undergo radiation induced changes as the irradiation (or burnup) history progresses. In this case, the induced changes in structure will have a direct impact on many properties including the neutronic behavior. This can be easily anticipated if one recognizes the dependence of neutron thermalization on the scattering law of the moderator. For the pebble bed reactor, it is anticipated that the moderating behavior can be tailored, e.g. using moderators that consist of composite materials, which could allow improved optimization of the moderator-to-fuel ratio.

  17. 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.

  18. Neutron β Decay: Status and Future of the Asymmetry Measurement

    SciTech Connect

    Ito, Takeyasu M.

    2007-04-04

    With more intense sources of cold and ultracold neutrons becoming available and with improved experimental techniques being developed, determination of ΙVud l from neutron β decay with a similar precision to that from from superallowed β decays is within reach. Determination of IVud l from neutron β decay, free from nuclear corrections, holds the most promise for a further improvement of the determination of IVud l· The current and future neutron β decay correlation experiments including the UCNA experiment at Los Alamos National Laboratory are reviewed.

  19. 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.

  20. Investigation of Thermal Hydraulics of a Nuclear Reactor Moderator

    NASA Astrophysics Data System (ADS)

    Sarchami, Araz

    A three-dimensional numerical modeling of the thermo hydraulics of Canadian Deuterium Uranium (CANDU) nuclear reactor is conducted. The moderator tank is a Pressurized heavy water reactor which uses heavy water as moderator in a cylindrical tank. The main use of the tank is to bring the fast neutrons to the thermal neutron energy levels. The moderator tank compromises of several bundled tubes containing nuclear rods immersed inside the heavy water. It is important to keep the water temperature in the moderator at sub-cooled conditions, to prevent potential failure due to overheating of the tubes. Because of difficulties in measuring flow characteristics and temperature conditions inside a real reactor moderator, tests are conducted using a scaled moderator in moderator test facility (MTF) by Chalk River Laboratories of Atomic Energy of Canada Limited (CRL, AECL). MTF tests are conducted using heating elements to heat tube surfaces. This is different than the real reactor where nuclear radiation is the source of heating which results in a volumetric heating of the heavy water. The data recorded inside the MTF tank have shown levels of fluctuations in the moderator temperatures and requires in depth investigation of causes and effects. The purpose of the current investigation is to determine the causes for, and the nature of the moderator temperature fluctuations using three-dimensional simulation of MTF with both (surface heating and volumetric heating) modes. In addition, three dimensional simulation of full scale actual moderator tank with volumetric heating is conducted to investigate the effects of scaling on the temperature distribution. The numerical simulations are performed on a 24-processor cluster using parallel version of the FLUENT 12. During the transient simulation, 55 points of interest inside the tank are monitored for their temperature and velocity fluctuations with time.

  1. Beam extraction and delivery at compact neutron sources

    NASA Astrophysics Data System (ADS)

    Mezei, F.

    2016-11-01

    The beam performance of a source of radiation is primarily characterized by its brightness, which remains constant in a conservative force field along the propagation of the beam. The neutron flux at an area with direct view to a homogenous radiation emitting moderator surface will just depend on the solid angle of beam divergence as determined by the moderator size. Recently it was found that by reducing the size of neutron moderators their brightness can be enhanced by a factor in the range of up to 3-6. In direct view of such moderators from sizable distances often required in neutron scattering applications the beam divergence will become reduced. Supermirror based neutron optical guide systems allow us to deliver neutron beam divergences independently of distance from the source. Due to the low radiation fields at compact sources such systems can be placed close to the neutron emitting moderators, a specific advantage and a new design feature. Focusing type neutron guides with phase space acceptance properly matched to the phase space to be delivered over distance can provide for beam delivery with small losses of brightness within a convenient and flexible range of beam parameters.

  2. Neutron spectrometry using LNL bonner spheres and FLUKA

    NASA Astrophysics Data System (ADS)

    Sarchiapone, L.; Zafiropoulos, D.

    2013-07-01

    The characterization of neutron fields has been made with a system based on a scintillation detector and multiple moderating spheres. The system, together with the unfolding procedure, have been tested in quasi-monochromatic neutron energy fields and in complex, mixed, cyclotron based environments. FLUKA simulations have been used to produce response functions and reference energy spectra.

  3. Moderator Chemistry Program

    SciTech Connect

    Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

    1990-11-01

    Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department`s moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

  4. Moderator Chemistry Program

    SciTech Connect

    Dewitt, L.V.; Gibbs, A.; Lambert, D.P.; Bohrer, S.R.; Fanning, R.L.; Houston, M.W.; Stinson, S.L.; Deible, R.W.; Abdel-Khalik, S.I.

    1990-11-01

    Over the past fifteen months, the Systems Chemistry Group of the Reactor Engineering Department has undertaken a comprehensive study of the Department's moderator chemistry program at Savannah River Site (SRS). An internal review was developed to formalize and document this program. Objectives were as outlined in a mission statement and action plan. In addition to the mission statement and action plan, nine separate task reports have been issued during the course of this study. Each of these task reports is included in this document as a chapter. This document is an organized compilation of the individual reports issued by the Systems Chemistry Group in assessment of SRS moderator chemistry to determine if there were significant gaps in the program as ft existed in October, 1989. While these reviews found no significant gaps in that mode of operation, or any items that adversely affected safety, items were identified that could be improved. Many of the items have already been dear with or are in the process of completion under this Moderator Chemistry Program and other Reactor Restart programs. A complete list of the items of improvement found under this assessment is found in Chapter 9, along with a proposed time table for correcting remaining items that can be improved for the chemistry program of SRS reactors. An additional external review of the moderator chemistry processes, recommendations, and responses to/from the Reactor Corrosion Mitigation Committee is included as Appendix to this compilation.

  5. Cold pool dissipation

    NASA Astrophysics Data System (ADS)

    Grant, Leah D.; Heever, Susan C.

    2016-02-01

    The mechanisms by which sensible heat fluxes (SHFs) alter cold pool characteristics and dissipation rates are investigated in this study using idealized two-dimensional numerical simulations and an environment representative of daytime, dry, continental conditions. Simulations are performed with no SHFs, SHFs calculated using a bulk formula, and constant SHFs for model resolutions with horizontal (vertical) grid spacings ranging from 50 m (25 m) to 400 m (200 m). In the highest resolution simulations, turbulent entrainment of environmental air into the cold pool is an important mechanism for dissipation in the absence of SHFs. Including SHFs enhances cold pool dissipation rates, but the processes responsible for the enhanced dissipation differ depending on the SHF formulation. The bulk SHFs increase the near-surface cold pool temperatures, but their effects on the overall cold pool characteristics are small, while the constant SHFs influence the near-surface environmental stability and the turbulent entrainment rates into the cold pool. The changes to the entrainment rates are found to be the most significant of the SHF effects on cold pool dissipation. SHFs may also influence the timing of cold pool-induced convective initiation by altering the environmental stability and the cold pool intensity. As the model resolution is coarsened, cold pool dissipation is found to be less sensitive to SHFs. Furthermore, the coarser resolution simulations not only poorly but sometimes wrongly represent the SHF impacts on the cold pools. Recommendations are made regarding simulating the interaction of cold pools with convection and the land surface in cloud-resolving models.

  6. High Brightness Neutron Source for Radiography

    SciTech Connect

    Cremer, J. T.; Piestrup, Melvin, A.; Gary, Charles, K.; Harris, Jack, L. Williams, David, J.; Jones, Glenn, E.; Vainionpaa, J. , H.; Fuller, Michael, J.; Rothbart, George, H.; Kwan, J., W.; Ludewigt, B., A.; Gough, R.., A..; Reijonen, Jani; Leung, Ka-Ngo

    2008-12-08

    This research and development program was designed to improve nondestructive evaluation of large mechanical objects by providing both fast and thermal neutron sources for radiography. Neutron radiography permits inspection inside objects that x-rays cannot penetrate and permits imaging of corrosion and cracks in low-density materials. Discovering of fatigue cracks and corrosion in piping without the necessity of insulation removal is possible. Neutron radiography sources can provide for the nondestructive testing interests of commercial and military aircraft, public utilities and petrochemical organizations. Three neutron prototype neutron generators were designed and fabricated based on original research done at the Lawrence Berkeley National Laboratory (LBNL). The research and development of these generators was successfully continued by LBNL and Adelphi Technology Inc. under this STTR. The original design goals of high neutron yield and generator robustness have been achieved, using new technology developed under this grant. In one prototype generator, the fast neutron yield and brightness was roughly 10 times larger than previously marketed neutron generators using the same deuterium-deuterium reaction. In another generator, we integrate a moderator with a fast neutron source, resulting in a high brightness thermal neutron generator. The moderator acts as both conventional moderator and mechanical and electrical support structure for the generator and effectively mimics a nuclear reactor. In addition to the new prototype generators, an entirely new plasma ion source for neutron production was developed. First developed by LBNL, this source uses a spiral antenna to more efficiently couple the RF radiation into the plasma, reducing the required gas pressure so that the generator head can be completely sealed, permitting the possible use of tritium gas. This also permits the generator to use the deuterium-tritium reaction to produce 14-MeV neutrons with increases

  7. Response of six neutron survey meters in mixed fields of fast and thermal neutrons.

    PubMed

    Kim, S I; Kim, B H; Chang, I; Lee, J I; Kim, J L; Pradhan, A S

    2013-10-01

    Calibration neutron fields have been developed at KAERI (Korea Atomic Energy Research Institute) to study the responses of commonly used neutron survey meters in the presence of fast neutrons of energy around 10 MeV. The neutron fields were produced by using neutrons from the (241)Am-Be sources held in a graphite pile and a DT neutron generator. The spectral details and the ambient dose equivalent rates of the calibration fields were established, and the responses of six neutron survey meters were evaluated. Four single-moderator-based survey meters exhibited an under-responses ranging from ∼9 to 55 %. DINEUTRUN, commonly used in fields around nuclear reactors, exhibited an over-response by a factor of three in the thermal neutron field and an under-response of ∼85 % in the mixed fields. REM-500 (tissue-equivalent proportional counter) exhibited a response close to 1.0 in the fast neutron fields and an under-response of ∼50 % in the thermal neutron field.

  8. Neutron-Absorbing Coatings for Safe Storage of Fissile Materials with Enhanced Shielding & Criticality Safety

    SciTech Connect

    Choi, J; Farmer, J; Lee, C; Fischer, L; Boussoufi, M; Liu, B; Egbert, H

    2007-07-03

    Neutron-absorbing Fe-based amorphous-metal coatings have been developed that are more corrosion resistant than other criticality-control materials, including Al-B{sub 4}C composites, borated stainless steels, and Ni-Cr-Mo-Gd alloys. The presence of relatively high concentration of boron in these coatings not only enhances its neutron-absorption capability, but also enables these coatings to exist in the amorphous state. Exceptional corrosion resistance has been achieved with these Fe-based amorphous-metal alloys through additions of chromium, molybdenum, and tungsten. The addition of rare earth elements such as yttrium has lowered the critical cooling rate of these materials, thereby rendering them more easily processed. Containers used for the storage of nuclear materials, and protected from corrosion through the application of amorphous metal coatings, would have greatly enhanced service lives, and would therefore provide greater long-term safety. Amorphous alloy powders have been successfully produced in multi-ton quantities with gas atomization, and applied to several half-scale spent fuel storage containers and criticality control structures with the high-velocity oxy-fuel (HVOF) thermal spray process. Salt fog testing and neutron radiography of these prototypes indicates that such an approach is viable for the production of large-scale industrial-scale facilities and containers. The use of these durable neutron-absorbing materials to coat stainless steel containers and storage racks, as well as vaults, hot-cell facilities and glove boxes could substantially reduce the risk of criticality in the event of an accident. These materials are particularly attractive for shielding applications since they are fire proof. Additionally, layers of other cold and thermal sprayed materials that include carbon and/or carbides can be used in conjunction with the high-boron amorphous metal coatings for the purpose of moderation. For example, various carbides, including boron

  9. Cold fusion, Alchemist's dream

    SciTech Connect

    Clayton, E.D.

    1989-09-01

    In this report the following topics relating to cold fusion are discussed: muon catalysed cold fusion; piezonuclear fusion; sundry explanations pertaining to cold fusion; cosmic ray muon catalysed cold fusion; vibrational mechanisms in excited states of D{sub 2} molecules; barrier penetration probabilities within the hydrogenated metal lattice/piezonuclear fusion; branching ratios of D{sub 2} fusion at low energies; fusion of deuterons into {sup 4}He; secondary D+T fusion within the hydrogenated metal lattice; {sup 3}He to {sup 4}He ratio within the metal lattice; shock induced fusion; and anomalously high isotopic ratios of {sup 3}He/{sup 4}He.

  10. Neutron Imaging Calibration to Measure Void Fraction

    SciTech Connect

    Geoghegan, Patrick J; Bilheux, Hassina Z; Sharma, Vishaldeep; Fricke, Brian A

    2015-01-01

    Void fraction is an intuitive parameter that describes the fraction of vapor in a two-phase flow. It appears as a key variable in most heat transfer and pressure drop correlations used to design evaporating and condensing heat exchangers, as well as determining charge inventory in refrigeration systems. Void fraction measurement is not straightforward, however, and assumptions on the invasiveness of the measuring technique must be made. Neutron radiography or neutron imaging has the potential to be a truly non-invasive void fraction measuring technique but has until recently only offered qualitative descriptions of two-phase flow, in terms of flow maldistributions, for example. This paper describes the calibration approach necessary to employ neutron imaging to measure steady-state void fraction. Experiments were conducted at the High Flux Isotope Reactor (HFIR) Cold Guide 1D neutron imaging facility at Oak Ridge National Laboratory (ORNL), Oak Ridge, TN, USA.

  11. 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.

  12. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1960-09-27

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

  13. The Impact of Craters on Neutron Fluxes and Lunar Polar Hydrogen Abundances

    NASA Astrophysics Data System (ADS)

    Eke, V.; Bower, K.; Diserens, S.; Ryder, M.; Yeomans, P.; Teodoro, L.; Elphic, R.; Feldman, W.; Hermalyn, B.; Lavelle, C.; Lawrence, D.; Maurice, S.

    2015-10-01

    Hydrogen abundances in lunar polar cold traps are investigated using remotely-sensed neutron count rates. The effect of neutron beaming from craters is measured using data from the Lunar Prospector Neutron Spectrometer (LPNS) and understood in the context of a simple model. This enables a reanalysis of data near the lunar poles, accounting for the topographical impact on the neutron count rates, leading to improved estimates of the hydrogen abundance in the various cold traps. For the case of Cabeus, taking into account the topographical effect increases the inferred water- equivalent hydrogen weight percentage from˜1%to˜4%, consistent with that measured using the LCROSS impactor.

  14. Neutron Compound Refractive Prisms - DOE SBIR Phase II Final Report

    SciTech Connect

    Cremer, Jr, Jay Theodore

    2011-06-25

    The results of the research led to a pulsed electromagnetic periodic magnetic field array (PMF), which coupled with a pair of collimation slits, and a mechanical chopper slit, were able to deflect spin-up neutrons to a band of line-fused neutrons a focal plane heights that correspond to the time-varying magnetic field amplitude. The electromagnetic field PMF produced 5.4 pulses per minute in which each pulse was 50 msec in duration with a full width half maximum (FWHM) of 7.5 msec. The calculated 7.7 mm vertical height of the band of focused spin-up neutrons corresponded closely to the measured 7.5 mm height of the center line of the imaged band of neutrons. The band of deflected spin-up neutrons was 5 mm in vertical width and the bottom of the band was 5 mm above the surface of the PMF pole. The limited exposure time of 3 hours and the smaller 0.78 T magnetic field allowed focused and near focused neutrons of 1.8 to 2.6 neutrons, which were in the tails of the McClellan Nuclear Radiation Center Bay 4 Maxwell Boltzmann distribution of neutrons with peak flux at 1.1-1.2. The electromagnetic PMF was expected to produces a 2.0 T peak magnetic field amplitude, which would be operational at a higher duty factor, rather than the as built 7.5 msec FWHM with pulse repetition frequency of 5.4 pulses per minute. The fabricated pulsed electromagnetic PMF with chopper is expected to perform well on a cold, very cold or ultra cold beam line as a spectrometer or monochromator source of spin-up polarized neutron. In fact there may be a possible use of the PMF to do ultra-cold neutron trapping, see paper by A. I. Frank1, V. G. Nosov, Quantum Effects in a One-Dimensional Magnetic Gravitational Trap for Ultracold Neutrons, JETP Letters, Vol. 79, No. 7, 2004, pp. 313-315. The next step is to find a cold or very cold neutron facility, where further testing or use of the pulsed magnetic field PMF can be pursued.

  15. Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

    NASA Technical Reports Server (NTRS)

    Poindexter, A. M.

    1967-01-01

    Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

  16. Fiber optic thermal/fast neutron and gamma ray scintillation detector

    DOEpatents

    Neal, John S.; Mihalczo, John T.

    2006-11-28

    A detector system that combines a .sup.6Li loaded glass fiber scintillation thermal neutron detector with a fast scintillation detector in a single layered structure. Detection of thermal and fast neutrons and ionizing electromagnetic radiation is achieved in the unified detector structure. The fast scintillator replaces the polyethelene moderator layer adjacent the .sup.6Li loaded glass fiber panel of the neutron detector and acts as the moderator for the glass fibers. Fast neutrons, x-rays and gamma rays are detected in the fast scintillator. Thermal neutrons, x-rays and gamma rays are detected in the glass fiber scintillator.

  17. Martian Neutron Energy Spectrometer (MANES)

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  18. Methods for absorbing neutrons

    DOEpatents

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

    2012-07-24

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

  19. Neutron multiplication error in TRU waste measurements

    SciTech Connect

    Veilleux, John; Stanfield, Sean B; Wachter, Joe; Ceo, Bob

    2009-01-01

    Total Measurement Uncertainty (TMU) in neutron assays of transuranic waste (TRU) are comprised of several components including counting statistics, matrix and source distribution, calibration inaccuracy, background effects, and neutron multiplication error. While a minor component for low plutonium masses, neutron multiplication error is often the major contributor to the TMU for items containing more than 140 g of weapons grade plutonium. Neutron multiplication arises when neutrons from spontaneous fission and other nuclear events induce fissions in other fissile isotopes in the waste, thereby multiplying the overall coincidence neutron response in passive neutron measurements. Since passive neutron counters cannot differentiate between spontaneous and induced fission neutrons, multiplication can lead to positive bias in the measurements. Although neutron multiplication can only result in a positive bias, it has, for the purpose of mathematical simplicity, generally been treated as an error that can lead to either a positive or negative result in the TMU. While the factors that contribute to neutron multiplication include the total mass of fissile nuclides, the presence of moderating material in the matrix, the concentration and geometry of the fissile sources, and other factors; measurement uncertainty is generally determined as a function of the fissile mass in most TMU software calculations because this is the only quantity determined by the passive neutron measurement. Neutron multiplication error has a particularly pernicious consequence for TRU waste analysis because the measured Fissile Gram Equivalent (FGE) plus twice the TMU error must be less than 200 for TRU waste packaged in 55-gal drums and less than 325 for boxed waste. For this reason, large errors due to neutron multiplication can lead to increased rejections of TRU waste containers. This report will attempt to better define the error term due to neutron multiplication and arrive at values that are

  20. Cold stress and the cold pressor test.

    PubMed

    Silverthorn, Dee U; Michael, Joel

    2013-03-01

    Temperature and other environmental stressors are known to affect blood pressure and heart rate. In this activity, students perform the cold pressor test, demonstrating increased blood pressure during a 1- to 2-min immersion of one hand in ice water. The cold pressor test is used clinically to evaluate autonomic and left ventricular function. This activity is easily adapted to an inquiry format that asks students to go to the scientific literature to learn about the test and then design a protocol for carrying out the test in classmates. The data collected are ideal for teaching graphical presentation of data and statistical analysis.

  1. 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)

  2. 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.

  3. 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.

  4. Cold Sores (HSV-1)

    MedlinePlus

    ... Help a Friend Who Cuts? Cold Sores (HSV-1) KidsHealth > For Teens > Cold Sores (HSV-1) Print A A A Text Size What's in ... person's lips, are caused by herpes simplex virus-1 (HSV-1) . But they don't just show ...

  5. Hot and cold fusion

    SciTech Connect

    Not Available

    1990-08-01

    This article presents an overview of research in cold fusion research and development in cold fusion at the Tokomak Fusion Test Reactor at the Princeton Plasma Physics Lab, and at the inertial containment facility at Lawrence Livermore National Lab. is described.

  6. Liquid metal cold trap

    DOEpatents

    Hundal, Rolv

    1976-01-01

    A cold trap assembly for removing impurities from a liquid metal being provided with a hole between the incoming impure liquid metal and purified outgoing liquid metal which acts as a continuous bleed means and thus prevents the accumulation of cover gases within the cold trap assembly.

  7. Preliminary Analysis of the Multisphere Neutron Spectrometer

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  8. Neutron detector simultaneously measures fluence and dose equivalent

    NASA Technical Reports Server (NTRS)

    Dvorak, R. F.; Dyer, N. C.

    1967-01-01

    Neutron detector acts as both an area monitoring instrument and a criticality dosimeter by simultaneously measuring dose equivalent and fluence. The fluence is determined by activation of six foils one inch below the surface of the moderator. Dose equivalent is determined from activation of three interlocked foils at the center of the moderator.

  9. High efficiency proportional neutron detector with solid liner internal structures

    DOEpatents

    Kisner, Roger Allen; Holcomb, David Eugene; Brown, Gilbert M.

    2014-08-05

    A tube-style neutron detector, a panel-style neutron detector incorporating a plurality of tube-style neutron detectors, and a panel-style neutron detector including a plurality of anode wires are provided. A plurality of channels is provided in a neutron detector such that each channel has an inner surface of a coating layer including a neutron-absorbing material. A wire anode is provided at end of each channel so that electrons generated by a charged daughter particle generated by a neutron are collected to detect a neutron-matter interaction. Moderator units can be incorporated into a neutron detector to provide improved detection efficiencies and/or to determine neutron energy spectrum. Gas-based proportional response from the neutron detectors can be employed for special nuclear material (SNM) detection. This neutron detector can provide similar performance to .sup.3He-based detectors without requiring .sup.3He and without containing toxic, flammable, or high-pressure materials.

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

    SciTech Connect

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

    1996-09-01

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

  11. Neutron Imaging at the Oak Ridge National Laboratory: Application to Biological Research

    SciTech Connect

    Bilheux, Hassina Z; Cekanova, Maria; Bilheux, Jean-Christophe; Bailey, William Barton; Keener, Wylie S; Davis, Larry E; Herwig, Kenneth W

    2014-01-01

    The Oak Ridge National Laboratory Neutron Sciences Directorate (NScD) has recently installed a neutron imaging beamline at the High Flux Isotope Reactor (HFIR) cold guide hall. The CG-1D beamline supports a broad range of user research spanning from engineering to material research, energy storage, additive manufacturing, vehicle technologies, archaeology, biology, and plant physiology. The beamline performance (spatial resolution, field of view, etc.) and its utilization for biological research are presented. The NScD is also considering a proposal to build the VENUS imaging beamline (beam port 10) at the Spallation Neutron Source (SNS). Unlike CG-1D which provides cold neutrons, VENUS will offer a broad range of neutron wavelengths, from epithermal to cold, and enhanced contrast mechanisms. This new capability will also enable the imaging of thicker biological samples than is currently available at CG-1D. A brief overview of the VENUS capability for biological research is discussed.

  12. Status report on the Low Energy Neutron Source for 2015

    NASA Astrophysics Data System (ADS)

    Baxter, D. V.; Rinckel, T.

    2016-11-01

    The Low Energy Neutron Source at Indiana University first produced cold neutrons in April of 2005. Ten years after first reaching this milestone, the facility has three instruments in operation on its cold target station, and a second target station is devoted to thermal and fast neutron physics offers capabilities in radiation effects research (single-event effects in electronics) and radiography. Key elements in our success over these last ten years have been the diversity of activities we have been able maintain (which often involves using each of our instruments for multiple different activities), the close relationship we have developed with a number of major sources, and the focus we have had on innovation in neutron instrumentation. In this presentation, we will introduce some of the highlights from our most recent activities, provide an update on some of our technical challenges, and describe some of our ideas for the future.

  13. Integrated neutron/gamma-ray portal monitors for nuclear safeguards

    SciTech Connect

    Fehlau, P.E.

    1993-09-01

    Radiation monitoring is one nuclear-safeguards measure used to protect against the theft of special nuclear materials (SNM) by pedestrians departing from SNM access areas. The integrated neutron/gamma-ray portal monitor is an ideal radiation monitor for the task when the SNM is plutonium. It achieves high sensitivity for detecting both bare and shielded plutonium by combining two types of radiation detector. One type is a neutron-chamber detector, comprising a large, hollow, neutron moderator that contains a single thermal-neutron proportional counter. The entrance wall of each chamber is thin to admit slow neutrons from plutonium contained in a moderating shield, while the other walls are thick to moderate fast neutrons from bare or lead-shielded plutonium so that they can be detected. The other type of detector is a plastic scintillator that is primarily for detecting gamma rays from small amounts of unshielded plutonium. The two types of detector are easily integrated by making scintillators part of the thick back wall of each neutron chamber or by inserting them into each chamber void. We compared the influence of the two methods of integration on detecting neutrons and gamma rays, and we examined the effectiveness of other design factors and the methods for signal detection as well.

  14. Development of Neutron Interferometer with Wide-Gapped ''BSE''s for Precision Measurements

    SciTech Connect

    Seki, Y.; Kitaguchi, M.; Hino, M.; Funahashi, H.; Taketani, K.; Otake, Y.; Shimizu, H. M.

    2007-06-13

    We are developing large-dimensional cold-neutron interferometers with multilayer mirrors in order to investigate small interactions. In particular Jamin type interferometers composed of wide-gapped 'BSE's, which divide the beam completely, can realize the precision measurement of topological Aharonov-Casher effect. We have made a prototype with 200 {mu}m gapped BSEs and confirmed the spatial separation of its two paths at monochromatic cold-neutron beamline MINE2 on JRR-3M reactor in JAEA.

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

    PubMed

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

    2004-01-01

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

  16. Detection of explosives and illicit drugs using neutrons

    NASA Astrophysics Data System (ADS)

    Király, B.; Sanami, T.; Dóczi, R.; Csikai, J.

    2004-01-01

    A procedure developed for the determination of the flux perturbation factor required for the thermal neutron activation analysis of bulky samples of unknown composition has been extended for epithermal neutrons using hydrogenous and graphite moderators. Measurements on the diffusion and backscattering of thermal neutrons in soil components were carried out for the development of novel nuclear methods in order to speed up the humanitarian demining process. Results obtained for the diffusion length were checked by MCNP-4C calculations. In addition, the effect of the weight and density of the explosives on the observation of the anomaly in the reflected thermal neutrons was examined by using different dummy landmines.

  17. NEUTRONIC REACTOR

    DOEpatents

    Metcalf, H.E.; Johnson, H.W.

    1961-04-01

    BS>A nuclear reactor incorporating fuel rods passing through a moderator and including tubes of a material of higher Thermal conductivity than the fuel in contact with the fuel is described. The tubes extend beyond the active portion of the reactor into contant with a fiuld coolant.

  18. How do people define moderation?

    PubMed

    vanDellen, Michelle R; Isherwood, Jennifer C; Delose, Julie E

    2016-06-01

    Eating in moderation is considered to be sound and practical advice for weight maintenance or prevention of weight gain. However, the concept of moderation is ambiguous, and the effect of moderation messages on consumption has yet to be empirically examined. The present manuscript examines how people define moderate consumption. We expected that people would define moderate consumption in ways that justified their current or desired consumption rather than view moderation as an objective standard. In Studies 1 and 2, moderate consumption was perceived to involve greater quantities of an unhealthy food (chocolate chip cookies, gummy candies) than perceptions of how much one should consume. In Study 3, participants generally perceived themselves to eat in moderation and defined moderate consumption as greater than their personal consumption. Furthermore, definitions of moderate consumption were related to personal consumption behaviors. Results suggest that the endorsement of moderation messages allows for a wide range of interpretations of moderate consumption. Thus, we conclude that moderation messages are unlikely to be effective messages for helping people maintain or lose weight. PMID:26964691

  19. How do people define moderation?

    PubMed

    vanDellen, Michelle R; Isherwood, Jennifer C; Delose, Julie E

    2016-06-01

    Eating in moderation is considered to be sound and practical advice for weight maintenance or prevention of weight gain. However, the concept of moderation is ambiguous, and the effect of moderation messages on consumption has yet to be empirically examined. The present manuscript examines how people define moderate consumption. We expected that people would define moderate consumption in ways that justified their current or desired consumption rather than view moderation as an objective standard. In Studies 1 and 2, moderate consumption was perceived to involve greater quantities of an unhealthy food (chocolate chip cookies, gummy candies) than perceptions of how much one should consume. In Study 3, participants generally perceived themselves to eat in moderation and defined moderate consumption as greater than their personal consumption. Furthermore, definitions of moderate consumption were related to personal consumption behaviors. Results suggest that the endorsement of moderation messages allows for a wide range of interpretations of moderate consumption. Thus, we conclude that moderation messages are unlikely to be effective messages for helping people maintain or lose weight.

  20. Colossal Light-Induced Refractive-Index Modulation for Neutrons in Holographic Polymer-Dispersed Liquid Crystals

    SciTech Connect

    Fally, Martin; Ellabban, Mostafa A.; Drevensek-Olenik, Irena; Pranzas, Klaus P.; Vollbrandt, Juergen

    2006-10-20

    We report strong diffraction of cold neutrons from an only 30 {mu}m thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10{sup -6}, i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

  1. Advanced Neutron Source (ANS) Project Progress report, FY 1991

    SciTech Connect

    Campbell, J.H. ); Selby, D.L.; Harrington, R.M. ); Thompson, P.B. . Engineering Division)

    1992-01-01

    This report discusses the following about the Advanced Neutron Source: Project Management; Research and Development; Fuel Development; Corrosion Loop Tests and Analyses; Thermal-Hydraulic Loop Tests; Reactor Control and Shutdown Concepts; Critical and Subcritical Experiments; Material Data, Structural Tests, and Analysis; Cold-Source Development; Beam Tube, Guide, and Instrument Development; Hot-Source Development; Neutron Transport and Shielding; I C Research and Development; Design; and Safety.

  2. Advanced Neutron Source (ANS) Project Progress report, FY 1991

    SciTech Connect

    Campbell, J.H.; Selby, D.L.; Harrington, R.M.; Thompson, P.B.

    1992-01-01

    This report discusses the following about the Advanced Neutron Source: Project Management; Research and Development; Fuel Development; Corrosion Loop Tests and Analyses; Thermal-Hydraulic Loop Tests; Reactor Control and Shutdown Concepts; Critical and Subcritical Experiments; Material Data, Structural Tests, and Analysis; Cold-Source Development; Beam Tube, Guide, and Instrument Development; Hot-Source Development; Neutron Transport and Shielding; I & C Research and Development; Design; and Safety.

  3. Split-target neutronics and the MLNSC spallation target system

    SciTech Connect

    Russell, G.J.; Ferguson, P.D.; Pitcher, E.J.; Court, J.D.

    1996-12-31

    The Manuel Lujan, Jr., Neutron Scattering Center (MLNSC) at the Los Alamos National Laboratory is one of four operating Short-Pulse Spallation Sources worldwide. The MLNSC target system (composed of targets, moderators, and reflectors) was first installed in 1985. The target system employs a split tungsten spallation target with a void space in between (the flux-trap gap); this target system will be upgraded in 1998. The ability to efficiently split a spallation target allowed us to introduce the concept of flux-trap moderators and ultimately the notion of backscattering and upstream moderators. The upgraded MLNSC target system will employ both flux-trap and upstream/backscattering moderators to simultaneously service 16 neutron flight paths with high-intensity neutron beams for materials science research.

  4. The Fascinating World of Neutron Stars

    NASA Astrophysics Data System (ADS)

    Piekarewicz, J.

    2009-07-01

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the EOS of cold baryonic matter with special emphasis on its impact on the structure and dynamics of neutron stars. In particular, I will discuss the many fascinating phases that one encounters in the journey from the low-density crust to the high-density core.

  5. The Fascinating World of Neutron Stars

    SciTech Connect

    Piekarewicz, J.

    2009-07-06

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the EOS of cold baryonic matter with special emphasis on its impact on the structure and dynamics of neutron stars. In particular, I will discuss the many fascinating phases that one encounters in the journey from the low-density crust to the high-density core.

  6. The cold reading technique.

    PubMed

    Dutton, D L

    1988-04-15

    For many people, belief in the paranormal derives from personal experience of face-to-face interviews with astrologers, palm readers, aura and Tarot readers, and spirit mediums. These encounters typically involve cold reading, a process in which a reader makes calculated guesses about a client's background and problems and, depending on the reaction, elaborates a reading which seems to the client so uniquely appropriate that it carries with it the illusion of having been produced by paranormal means. The cold reading process is shown to depend initially on the Barnum effect, the tendency for people to embrace generalized personality descriptions as idiosyncratically their own. Psychological research into the Barnum effect is critically reviewed, and uses of the effect by a professional magician are described. This is followed by detailed analysis of the cold reading performances of a spirit medium. Future research should investigate the degree to which cold readers may have convinced themselves that they actually possess psychic or paranormal abilities.

  7. Cold wave lotion poisoning

    MedlinePlus

    Thioglycolate poisoning ... Below are symptoms of cold wave lotion poisoning in different parts of the body. EYES, EARS, NOSE, AND THROAT Mouth irritation Burning and redness of the eyes Possibly serious damage to ...

  8. Colds and flus - antibiotics

    MedlinePlus

    Fashner J, Ericson K, Werner S. Treatment of the common cold in children and adults. Am Fam Physician. 2012; ... gov/pubmed/22962927 . Melio FR, Berge LR. Upper respiratory tract infections. In: Marx JA, Hockberger RS, Walls RM, et ...

  9. 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.

  10. 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.

  11. Transcriptome and gene expression analysis in cold-acclimated guayule (Parthenium argentatum)rubber-producing tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural rubber biosynthesis in guayule (Parthenium argentatum) is associated with moderately cold night temperatures. To begin to dissect the molecular events triggered by cold temperatures that govern rubber synthesis induction in guayule, the transcriptome of bark tissue, where rubber is produced...

  12. Results from neutron imaging of ICF experiments at NIF

    NASA Astrophysics Data System (ADS)

    Merrill, F. E.; Danly, C. R.; Fittinghoff, D. N.; Grim, G. P.; Guler, N.; Volegov, P. L.; Wilde, C. H.

    2016-03-01

    In 2011 a neutron imaging diagnostic was commissioned at the National Ignition Facility (NIF). This new system has been used to collect neutron images to measure the size and shape of the burning DT plasma and the surrounding fuel assembly. The imaging technique uses a pinhole neutron aperture placed between the neutron source and a neutron detector. The detection system measures the two-dimensional distribution of neutrons passing through the pinhole. This diagnostic collects two images at two times. The long flight path for this diagnostic, 28 m, results in a chromatic separation of the neutrons, allowing the independently timed images to measure the source distribution for two neutron energies. Typically one image measures the distribution of the 14 MeV neutrons, and the other image measures the distribution of the 6-12 MeV neutrons. The combination of these two images has provided data on the size and shape of the burning plasma within the compressed capsule, as well as a measure of the quantity and spatial distribution of the cold fuel surrounding this core. Images have been collected for the majority of the experiments performed as part of the ignition campaign. Results from this data have been used to estimate a burn-averaged fuel assembly as well as providing performance metrics to gauge progress towards ignition. This data set and our interpretation are presented.

  13. Cold-start characteristics of polymer electrolyte fuel cells

    SciTech Connect

    Mishler, Jeff; Mukundan, Rangachary; Wang, Yun; Mishler, Jeff; Mukherjee, Partha P

    2010-01-01

    In this paper, we investigate the electrochemical reaction kinetics, species transport, and solid water dynamics in a polymer electrolyte fuel cell (PEFC) during cold start. A simplitied analysis is developed to enable the evaluation of the impact of ice volume fraction on cell performance during coldstart. Supporting neutron imaging data are also provided to reveal the real-time water evolution. Temperature-dependent voltage changes due to the reaction kinetics and ohmic loss are also analyzed based on the ionic conductivity of the membrane at subfreezing temperature. The analysis is valuable for the fundamental study of PEFC cold-start.

  14. FLUID MODERATED REACTOR

    DOEpatents

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

    1957-10-22

    A reactor which utilizes fissionable fuel elements in rod form immersed in a moderator or heavy water and a means of circulating the heavy water so that it may also function as a coolant to remove the heat generated by the fission of the fuel are described. In this design, the clad fuel elements are held in vertical tubes immersed in heavy water in a tank. The water is circulated in a closed system by entering near the tops of the tubes, passing downward through the tubes over the fuel elements and out into the tank, where it is drawn off at the bottom, passed through heat exchangers to give up its heat and then returned to the tops of the tubes for recirculation.

  15. Present status and plans for upgrading the Lujan neutron scattering center

    SciTech Connect

    Rhyne, James J

    2010-01-01

    The Lujan Center, part of the LANSCE accelerator complex at Los Alamos National Laboratory, operates a comprehensive neutron scattering facility for the U.S. Department of Energy that serves approximately 300 users per year. This paper will discuss the current instruments and status of the facility and also focus on the plans for a major upgrade of the Center including new instruments and enhancements to specific existing instruments. The instrument suite currently includes two reflectometers (one with full polarization), an engineering diffraction machine, a diffractometer specialized to pair-distribution analysis, 2 general purpose powder diffractometers, and 2 inelastic spectrometers. To complement these spectrometers, a full range of pressure, temperature, and magnetic field sample environments is available for users. As part of the planning for a forthcoming enhancement of Lujan Center, a series of workshops have been held over the past year to encourage user input to the design for new instruments as well as major upgrades of existing machines. Many of the planned facilities are designed to take advantage of the Lujan Center 20 Hz pulse repetition rate and cold source moderators, both of which are beneficial for high-resolution instruments using long neutron wavelengths.

  16. Direct evidence for inelastic neutron 'acceleration' by {sup 177}Lu{sup m}

    SciTech Connect

    Roig, O.; Meot, V.; Rosse, B.; Belier, G.; Daugas, J.-M.; Morel, P.; Letourneau, A.; Menelle, A.

    2011-06-15

    The inelastic neutron acceleration cross section on the long-lived metastable state of {sup 177}Lu has been measured using a direct method. High-energy neutrons have been detected using a specially designed setup placed on a cold neutron beam extracted from the ORPHEE reactor in Saclay. The 146{+-}19 b inelastic neutron acceleration cross section in the ORPHEE cold neutron flux confirms the high cross section for this process on the {sup 177}Lu{sup m} isomer. The deviation from the 258{+-}58 b previously published obtained for a Maxwellian neutron flux at a 323 K temperature could be explained by the presence of a low energy resonance. Resonance parameters are deduced and discussed.

  17. NEUTRONIC REACTOR

    DOEpatents

    Metcalf, H.E.

    1957-10-01

    A reactor of the type which preferably uses plutonium as the fuel and a liquid moderator, preferably ordinary water, and which produces steam within the reactor core due to the heat of the chain reaction is described. In the reactor shown the fuel elements are essentially in the form of trays and are ventically stacked in spaced relationship. The water moderator is continuously supplied to the trays to maintain a constant level on the upper surfaces of the fuel element as it is continually evaporated by the heat. The steam passes out through the spaces between the fuel elements and is drawn off at the top of the core. The fuel elements are clad in aluminum to prevent deterioration thereof with consequent contamimation of the water.

  18. NEUTRONIC REACTOR

    DOEpatents

    Wigner, E.P.

    1957-09-17

    A reactor of the type having coolant liquid circulated through clad fuel elements geometrically arranged in a solid moderator, such as graphite, is described. The core is enclosed in a pressure vessel and suitable shielding, wherein means is provided for circulating vapor through the core to superheat the same. This is accomplished by drawing off the liquid which has been heated in the core due to the fission of the fuel, passing it to a nozzle within a chamber where it flashes into a vapor, and then passing the vapor through separate tubes extending through the moderator to pick up more heat developed in the core due to the fission of the fuel, thereby producing superheated vapor.

  19. Toward precision D coefficient measurement in polarized neutron decay and the development of A helium-3 neutron polarizer

    NASA Astrophysics Data System (ADS)

    Hwang, Shenq-Rong

    1998-12-01

    I describe the search for possible time reversal symmetry violation by measurement of the coefficient D in polarized neutron decay. This relates to the triple product among the neutron polarization vector, electron momentum, and proton momentum in the neutron decay rate (w~[-]/σnċ(/vec pe×/vec pp)). With the improvements in neutron polarization (97%), an optimal octagonal detector geometry, and neutron spin transport system, about 15×106 decay events were selected from data acquired at the Cold Neutron Research Facility at NIST, Gaithersburg. I have developed techniques for extracting D from the positive and negative triple product decay rates. My preliminary result is D=(12.1/pm13.4)×10-4 where the uncertainty is statistical only. The false D resulting from the instrumental factor (σκ) and neutron polarization uncertainty (σP) are negligible. I also estimate the false D of the asymmetric transverse polarization (ATP) effect with an upper limit 5×10-4 for the preliminary analysis of the initial data. I also describe development of an optical pumping/spin exchange neutron spin filter and obtained 40% neutron polarization for 2 A neutrons with a 10 amagat-cm 35 cm3 polarized 3He cell.

  20. Cold Hardening in Citrus Stems

    PubMed Central

    Yelenosky, George

    1975-01-01

    Stem cold hardening developed to different levels in citrus types tested in controlled environments. Exotherms indicated ice spread was more uniform and rapid in unhardened than in cold-hardened stems. All attempts to inhibit the functioning of citrus leaves resulted in less cold hardening in the stems. Citrus leaves contribute a major portion of cold hardening in the wood. PMID:16659340

  1. Teaching in a Cold Environment.

    ERIC Educational Resources Information Center

    Ewert, Alan

    1979-01-01

    Designed to help teachers deal with students in a cold environment, this article explains cold physiology and fundamental laws of heat; describes 14 common cold injuries and their current treatment; and lists a number of useful teaching techniques for cold environments. (SB)

  2. Teaching in a Cold Environment.

    ERIC Educational Resources Information Center

    Ewert, Alan

    Instructors who teach outdoors in an environment so cold as to cause injury must satisfy program objectives while avoiding cold injury to themselves and students, help students focus on learning instead of discomfort, and alleviate some students' intense fear of the cold. Dealing with the cold successfully requires a thorough knowledge of:…

  3. Neutronic reactor

    DOEpatents

    Lewis, Warren R.

    1978-05-30

    A graphite-moderated, water-cooled nuclear reactor including a plurality of rectangular graphite blocks stacked in abutting relationship in layers, alternate layers having axes which are normal to one another, alternate rows of blocks in alternate layers being provided with a channel extending through the blocks, said channeled blocks being provided with concave sides and having smaller vertical dimensions than adjacent blocks in the same layer, there being nuclear fuel in the channels.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  5. Conceptual Design of the Liquid Hydrogen Moderator Cooling Circuit for the European Spallation Source

    NASA Astrophysics Data System (ADS)

    Klaus, M.; Haberstroh, Ch.; Quack, H.; Beßler, Y.; Butzek, M.

    The European Spallation Sourcein Lund, Sweden, will be a 5 MW beam power neutron spallation research center. As subsystem of the target station the moderators play a vital role by slowing down high energy neutrons set free during the spallation process. To provide maximum neutron flux intensities with high availability for scattering experiments a conceptual liquid hydrogen moderator cooling circulation design proposal was developed. Supercritical hydrogen at 17 K will be utilized to absorb energy of the incoming neutrons in two parallel moderator vessels. A helium refrigerator provides the necessary cooling capacity by implementing an additional helium expansion turbine downstream the refrigerator coldbox. Strategies for the mitigation of pressure fluctuations due to beam trips are being presented. Solutions in form of electrical heaters and an accumulator or an expansion vessel are discussed. Different supercritical hydrogen circulator implementation scenarios are being matched to indicate the most reliable setup. For an efficient moderation process parahydrogen concentrations higher than 99% have to be guaranteed at the moderator inlet. Due to potential conversion of parahydrogen to orthohydrogen via irradiation processes the implementation of an ortho-parahydrogen catalyst bed is being evaluated. Methods for a continuous measurement of the apparent parahydrogen concentration at the moderator in- and outlet will be introduced. The arrangement and interaction of the components will be detailed in the paper.

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

    DOEpatents

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

    1999-05-11

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

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

    DOEpatents

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

    1999-01-01

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

  8. Neutron Radiographic Inspection of Industrial Components using Kamini Neutron Source Facility

    NASA Astrophysics Data System (ADS)

    Raghu, N.; Anandaraj, V.; Kasiviswanathan, K. V.; Kalyanasundaram, P.

    2008-03-01

    Kamini (Kalpakkam Mini) reactor is a U233 fuelled, demineralised light water moderated and cooled, beryllium oxide reflected, low power (30 kW) nuclear research reactor. This reactor functions as a neutron source with a flux of 1012 n/cm2 s-1 at core centre with facilitates for carrying out neutron radiography, neutron activation analysis and neutron shielding experiments. There are two beam tubes for neutron radiography. The length/diameter ratio of the collimators is about 160 and the aperture size is 220 mm×70 mm. Flux at the outer end of the beam tube is ˜106-107 n/cm2 s. The north end beam tube is for radiography of inactive object while the south side beam tube is for radiography of radioactive objects. The availability of high neutron flux coupled with good collimated beam provides high quality radiographs with short exposure time. The reactor being a unique national facility for neutron radiography has been utilized in the examination of irradiated components, aero engine turbine blades, riveted plates, automobile chain links and for various types of pyro devices used in the space programme. In this paper, an overview of the salient features of this reactor facility for neutron radiography and our experience in the inspection of a variety of industrial components will be given.

  9. Heat generation and neutron beam characteristics in a high power pulsed spallation neutron source

    SciTech Connect

    Jerng, D.W.; Carpenter, J.M.

    1996-11-01

    In the course of conceptual design of a high power pulsed spallation source, a Monte Carlo model was developed for heat generation and neutronics studies. In this paper, we present two sets of results. The first set of calculations was performed with a simple target model to investigate general characteristics of power distribution and neutron production with various proton energies ranging from 0.8 to 12 GeV. The second set was performed with a realistic target model including major components of the target system to provide basic parameters for engineering design of a high power pulsed spallation source. Calculated results generally confirm that higher proton energy provides and advantage in target cooling system requirements and yet somewhat lower neutron beam intensity as a counter effect. The heat generation in the systems surrounding the target was investigated in detail and found to have important variation with position and according to proton beam energy. Calculations of the neutron currents from the moderators showed that the neutron beam intensity from moderators in the front region of the target decreased fro higher proton energy while that from moderators in the back region of the target remained almost unchanged.

  10. Active Neutron Interrogation to Detect Shielded Fissionable Material

    SciTech Connect

    D. L. Chichester; E. H. Seabury

    2009-05-01

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

  11. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star = EOS model of high density cold matter in the neutron star cores. Extensive observation and analysis of the data from the rising portions of the bursts = modeling of burst oscillations and thermonuclear flame spreading. Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  12. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Sudip

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star approaching EOS model of high density cold matter in the neutron star cores. +k Extensive observation and analysis of the data from the rising portions of the bursts - modeling of burst oscillations and thermonuclear flame spreading. +k Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  13. Thermal Neutron Capture Cross Section of 22Ne

    NASA Astrophysics Data System (ADS)

    Belgya, T.; Uberseder, E.; Petrich, D.; Käppeler, F.

    2009-01-01

    The radiative thermal neutron capture cross section of the astrophysically important 22Ne nucleus has been measured at the guided cold neutron beam of the Budapest Research Reactor. High-pressure gas-bottles filled with mixtures of enriched 22Ne and CH4 were used. The cross section was determined by means of the comparator method, and an improved decay-scheme obtained in this work. The new value for the thermal neutron cross section is 52.7±0.7 mb, 18% larger than the accepted value. The influence of the new cross section on the astrophysical reaction rate is under investigation.

  14. Short-range nucleon correlations and neutrino emission by neutron stars

    SciTech Connect

    Frankfurt, Leonid; Strikman, Mark

    2008-10-13

    We argue that significant probability of protons with momenta above their Fermi surface leads for proton concentrations p/n{>=}1/8 to the enhancement of termally excited direct and modified URCA processes within a cold neutron star, and to a nonzero probability of direct URCA processes for small proton concentrations (p/n{<=}1/8). We evaluate high momentum tails of neutron, proton and electrons distributions within a neutron star. We expect also significantly faster neutrino cooling of hyperon stars.

  15. Long-duration neutron production by nonflaring transients in the solar corona

    NASA Astrophysics Data System (ADS)

    Feldman, William C.; Lawrence, David J.; Vestrand, W. Thomas; Baker, Daniel N.; Peplowski, Patrick N.; Rodgers, Douglas J.

    2015-10-01

    The purpose of this work is to study neutron enhancements observed using the Neutron Spectrometer aboard MESSENGER in order to identify events that may have been generated at/or near the Sun by solar transients. To securely establish an origin of the observed neutrons that is nonlocal to the MESSENGER spacecraft, a measurement of the energetic ion environment local to MESSENGER is needed. For this purpose, we use energetic ion spectrometers on several spacecraft at 1 AU when they were magnetically connected to MESSENGER during an event. We report strong evidence that for six neutron events studied in detail, the detected neutrons do not likely have a local spacecraft origin. By implication, most of the detected neutrons for these six events may have originated near the Sun, generated by many moderate-level solar eruptive events that produce an extended solar exosphere of moderate-energy neutrons, protons, and electrons.

  16. 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.

  17. Design of the Mechanical Parts for the Neutron Guide System at HANARO

    SciTech Connect

    Shin, J. W.; Cho, Y. G.; Cho, S. J.; Ryu, J. S.

    2008-03-17

    The research reactor HANARO (High-flux Advanced Neutron Application ReactOr) in Korea will be equipped with a neutron guide system, in order to transport cold neutrons from the neutron source to the neutron scattering instruments in the neutron guide hall near the reactor building. The neutron guide system of HANARO consists of the in-pile plug assembly with in-pile guides, the primary shutter with in-shutter guides, the neutron guides in the guide shielding room with dedicated secondary shutters, and the neutron guides connected to the instruments in the neutron guide hall. Functions of the in-pile plug assembly are to shield the reactor environment from nuclear radiation and to support the neutron guides and maintain them precisely oriented. The primary shutter is a mechanical structure to be installed just after the in-pile plug assembly, which stops neutron flux on demand. This paper describes the design of the in-pile assembly and the primary shutter for the neutron guide system at HANARO. The design of the guide shielding assembly for the primary shutter and the neutron guides is also presented.

  18. Progress toward cold antihydrogen

    SciTech Connect

    Gabrielse, G.; Estrada, J.; Peil, S.; Roach, T.; Tan, J. N.; Yesley, P.

    1999-12-10

    The production and study of cold antihydrogen will require the manipulation of dense and cold, single component plasmas of antiprotons and positrons. The undertaking will build upon the experience of the nonneutral plasma physics community. Annihilations of the antimatter particles in the plasmas can be imaged, offering unique diagnostic opportunities not available to this community when electrons and protons are used. The techniques developed by our TRAP collaboration to capture and cool antiprotons will certainly be used by our expanded ATRAP collaboration, and by the competing ATHENA Collaboration, both working at the nearly completed AD facility of CERN. We recently demonstrated a new techniques for accumulating cold positrons directly into a cryogenic vacuum system. The closest we have come to low energy antihydrogen so far is to confine cold positrons and cold antiprotons within the same trap structure and vacuum container. Finally, we mention that stored electrons have been cooled to 70 mK, the first time that elementary particles have been cooled below 4 K. In such an apparatus it should be possible to study highly magnetized plasmas of electrons or positrons at this new low temperature.

  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. 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.

  20. Direct Measurement of Neutron-Neutron Scattering

    SciTech Connect

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

    2003-08-26

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