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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. HFIR cold neutron source moderator vessel design analysis

    SciTech Connect

    Chang, S.J.

    1998-04-01

    A cold neutron source capsule made of aluminum alloy is to be installed and located at the tip of one of the neutron beam tubes of the High Flux Isotope Reactor. Cold hydrogen liquid of temperature approximately 20 degree Kelvin and 15 bars pressure is designed to flow through the aluminum capsule that serves to chill and to moderate the incoming neutrons produced from the reactor core. The cold and low energy neutrons thus produced will be used as cold neutron sources for the diffraction experiments. The structural design calculation for the aluminum capsule is reported in this paper.

  3. The world's first pelletized cold neutron moderator at a neutron scattering facility

    NASA Astrophysics Data System (ADS)

    Ananiev, V.; Belyakov, A.; Bulavin, M.; Kulagin, E.; Kulikov, S.; Mukhin, K.; Petukhova, T.; Sirotin, A.; Shabalin, D.; Shabalin, E.; Shirokov, V.; Verhoglyadov, A.

    2014-02-01

    In July 10, 2012 cold neutrons were generated for the first time with the unique pelletized cold neutron moderator CM-202 at the IBR-2M reactor. This new moderator system uses small spherical beads of a solid mixture of aromatic hydrocarbons (benzene derivatives) as the moderating material. Aromatic hydrocarbons are known as the most radiation-resistant hydrogenous substances and have properties to moderate slow neutrons effectively. Since the new moderator was put into routine operation in September 2013, the IBR-2 research reactor of the Frank Laboratory of Neutron Physics has consolidated its position among the world's leading pulsed neutron sources for investigation of matter with neutron scattering methods.

  4. Cold neutron moderator on an upgraded IBR-2 reactor: The first set of results

    NASA Astrophysics Data System (ADS)

    Anan'ev, V. D.; Belyakov, A. A.; Bulavin, M. V.; Verkhoglyadov, A. E.; Kulikov, S. A.; Mukhin, K. A.; Shabalin, E. P.

    2014-02-01

    The first criticality of a new KZ-202 neutron moderator on the IBR-2M reactor is achieved. The moderator consists of thermal and cold units. The former is a room-temperature comb water moderator; the latter, a moderator using a mixture of aromatic hydrocarbons (mesitylene and m-xylene). The cold moderator is filled with granules of this mixture, which are supplied by a cold helium flow, and operates at 30 K. The combination of two units in one moderator makes it possible to simultaneously take the thermal and cold neutron spectra for extracted-beam spectrometers. The arrangement of the thermal and cold moderators is numerically optimized by the Monte Carlo method. The use of the cold moderator allows a 13-fold increase in the cold neutron intensity from its surface.

  5. Pulsed neutron source cold moderators --- concepts, design and engineering

    SciTech Connect

    Bauer, Guenter S.

    1997-01-01

    Moderator design for pulsed neutron sources is becoming more and more an interface area between source designers and instrument designers. Although there exists a high degree of flexibility, there are also physical and technical limitations. This paper aims at pointing out these limitations and examining ways to extend the current state of moderator technology in order to make the next generation neutron sources even more versatile and flexible tools for science in accordance with the users' requirements. (auth)

  6. Measurement of cold neutron spectra using a model cryogenic moderator of the IBR-2M reactor

    NASA Astrophysics Data System (ADS)

    Kulikov, S. A.; Kalinin, I. V.; Morozov, V. M.; Novikov, A. G.; Puchkov, A. V.; Chernikov, A. N.; Shabalin, E. P.

    2010-01-01

    The method and results of an experiment to determine the cold neutron spectrum from solid mesitylene at moderator temperatures of 10-50 K are presented. This study was performed at the DIN-2PI spectrometer of the IBR-2 reactor. The objective of the study was to verify the system of constants used in the Monte Carlo simulation of cryogenic neutron moderators of the IBR-2M reactor and to obtain the cold neutron yield as a function of the moderator temperature. Satisfactory agreement between the experimental and calculated neutron spectra at a mesitylene temperature of 20 K has been obtained; the ratio of cold neutron intensities at 10 and 50 K is ˜1.8.

  7. 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.

  8. Cold moderators at ORNL

    SciTech Connect

    Lucas, A. T.

    1997-09-01

    The Advanced Neutron Source (ANS) cold moderators were not an 'Oak Ridge first', but would have been the largest both physically and in terms of cold neutron flux. Two cold moderators were planned each 410 mm in diameter and containing about 30L of liquid deuterium. They were to be completely independent of each other. A modular system design was used to provide greater reliability and serviceability. When the ANS was terminated, up–grading of the resident High Flux Isotope Reactor (HFIR) was examined and an initial study was made into the feasibility of adding a cold source. Because the ANS design was modular, it was possible to use many identical design features. Sub-cooled liquid at 4 bar abs was initially chosen for the HFIR design concept, but this was subsequently changed to 15 bar abs to operate above the critical pressure. As in the ANS, the hydrogen will operate at a constant pressure throughout the temperature range and a completely closed loop with secondary containment was adopted. The heat load of 2 kW made the heat flux comparable with that of the ANS. Subsequent studies into the construction of cryogenic moderators for the proposed new Synchrotron Neutron source indicated that again many of the same design concepts could be used. By connecting the two cold sources together in series, the total heat load of 2 kW is very close to that of the HFIR allowing a very similar supercritical hydrogen system to be configured. The two hydrogen moderators of the SNS provide a comparable heat load to the HFIR moderator. It is subsequently planned to connect the two in series and operate from a single cold loop system, once again using supercritical hydrogen. The spallation source also provided an opportunity to re-examine a cold pellet solid methane moderator operating at 20K.

  9. Control system of pelletized cold neutron moderator at the IBR-2 reactor

    NASA Astrophysics Data System (ADS)

    Belyakov, A.; Bulavin, M.; Chernikov, A.; Churakov, A.; Kulikov, S.; Litvinenko, E.; Mukhin, K.; Petrenko, A.; Petukhova, T.; Sirotin, A.; Shabalin, E.; Shirokov, V.; Verhoglyadov, A.

    2015-11-01

    The unique pelletized cold neutron moderator CM-202 at the IBR-2 reactor was put into test operation and have already worked more than 2000 hours. Normal, fast and trouble-free operation of the cryogenic moderator requires strict adherence to technological conditions (fast charging and discharging of moderator chamber, maintenance of required temperature and pressure at different parts of cryogenic system). The system of control and measuring equipment, designed for cryogenic moderator of the IBR-2 reactor, satisfies all the requirements and is simple to use. Access to the system of measuring instruments is organized via network. The working cycles of moderator confirmed the reliability and stable operation of the whole control system.

  10. Analysis of neutron spectra and fluxes obtained with cold and thermal moderators at IBR-2 reactor: Experimental and computer-modeling studies

    NASA Astrophysics Data System (ADS)

    Kuklin, A. I.; Rogov, A. D.; Gorshkova, Yu. E.; Utrobin, P. K.; Kovalev, Yu. S.; Rogachev, A. V.; Ivankov, O. I.; Kutuzov, S. A.; Soloviov, D. V.; Gordeliy, V. I.

    2011-03-01

    The results of experimental and computer-modeling investigations of neutron spectra and fluxes obtained with cold and thermal moderators at the IBR-2 reactor (Joint Institute for Nuclear Research (JINR), Dubna) are presented. These studies are for the YuMO small-angle neutron scattering (SANS) spectrometer (IBR-2 beamline 4). The neutron spectra have been measured for two methane cold moderators for the standard configuration of the SANS instrument. The data from both moderators under different conditions of their operation are compared. The ratio of experimentally determined neutron fluxes of cold and thermal moderators is shown at different wavelengths. Monte Carlo simulations have been carried out to determine the spectra for cold-methane and thermal moderators. The results of calculations of the ratio of neutron fluxes of cold and thermal moderators at different wavelengths are demonstrated. In addition, the absorption of neutrons in the air gaps on the way from the moderator to the investigated sample is presented. SANS with the protein apoferritin was done with both cold methane and a thermal moderator and the data were compared. The prospects for the use of a cold moderator for a SANS spectrometer at IBR-2 are discussed. The advantages of using the YuMO spectrometer with a thermal moderator with respect to the tested cold moderator are shown.

  11. 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.

  12. Application of gamma densitometer for measurement of void fraction in liquid hydrogen moderator of HANARO cold neutron source

    NASA Astrophysics Data System (ADS)

    Kim, Myong-Seop; Choi, Jungwoon; Sun, Gwang-Min; Lee, Kye-Hong

    2009-06-01

    The void fraction in the liquid hydrogen used for the moderator of the HANARO cold neutron source (CNS) was measured by using a gamma densitometer technique. A mock-up of the HANARO CNS facility with an electric heating system as the heat source instead of radiations was constructed. The photon transmissions through the hydrogen moderator were simulated to search for an optimum experimental condition. From the simulation, it was confirmed that Am-241 was suitable for the measurement of the void fraction in the liquid hydrogen medium. A gamma densitometer using the Am-241 gamma-ray source was designed and installed at the mock-up of the CNS. The attenuation of 59.5 keV gamma-rays from the Am-241 through the hydrogen medium was measured by using an HPGe detector. The void fraction was determined using the amount of the gamma-ray attenuation. The void fractions in the hydrogen moderator were measured for stable thermo-siphon loops with several electric heat loads applied to the moderator cell of the CNS mock-up. The longitudinal distribution of the void fraction inside the moderator cell was also determined. The void fraction measured at a heat load of 720 W had values of 8-41% depending on the height from the bottom of the moderator cell. The overall void fraction was obtained by volume-weighted averaging of its longitudinal distribution. The void fraction at the nuclear heating power expected at the normal operation condition of the HANARO CNS facility was determined to be about 20%. The large uncertainty was expected in the void fraction determination by a gamma densitometer for the liquid hydrogen medium with the void fraction less than 10%. When the void fraction of the liquid hydrogen was near 20%, the uncertainty in the void fraction determination by using a gamma densitometer became relatively small, and it was regarded as an acceptable level. The measurements for the void fraction will be very useful for the design and operation of the HANARO CNS.

  13. 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.

  14. 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.

  15. Imaging with cold neutrons

    NASA Astrophysics Data System (ADS)

    Lehmann, E. H.; Kaestner, A.; Josic, L.; Hartmann, S.; Mannes, D.

    2011-09-01

    Neutrons for imaging purposes are provided mainly from thermal beam lines at suitable facilities around the world. The access to cold neutrons is presently limited to very few places only. However, many challenging options for imaging with cold neutrons have been found out, given by the interaction behavior of the observed materials with neutrons in the cold energy range (3-10 Å). For absorbing materials, the interaction probability increases proportionally with the wavelength with the consequence of more contrast but less transmission with cold neutrons. Many materials are predominantly scattering neutrons, in particular most of crystalline structural materials. In these cases, cold neutrons play an important role by covering the energy range of the most important Bragg edges given by the lattice planes of the crystallites. This particular behavior can be used for at least two important aspects—choosing the right energy of the initial beam enables to have a material more or less transparent, and a direct macroscopic visualization of the crystalline structure and its change in a manufacturing process. Since 2006, PSI operates its second beam line for neutron imaging, where cold neutrons are provided from a liquid deuterium cold source (operated at 25 K). It has been designed to cover the most current aspects in neutron imaging research with the help of high flexibility. This has been done with changeable inlet apertures, a turbine based velocity selector, two beam positions and variable detector systems, satisfying the demands of the individual investigation. The most important detection system was found to be a micro-tomography system that enables studies in the presently best spatial resolution. In this case, the high contrast from the sample interaction process and the high detection probability for the cold neutrons combines in an ideal combination for the best possible performance. Recently, it was found out that the energy selective studies might become a

  16. 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.

  17. A modular approach to the design of cold moderators

    SciTech Connect

    Lucas, A.T.

    1998-11-01

    Cold moderators are usually designed to the specific requirements of the parent neutron source. However since all cryogenic moderators within a broad design envelope require certain common parameters, it should be possible to create a central core design served by smaller packages designed, or selected to satisfy a wide range of individual requirements. This paper describes a modular design philosophy that has been applied to two very different cold sources with only minor changes to two of the modules in the system. Both of the systems and the basic differences between them are described in detail.

  18. 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)

  19. Neutronic moderator design for the Spallation Neutron Source (SNS)

    SciTech Connect

    Charlton, L.A.; Barnes, J.M.; Johnson, J.O.; Gabriel, T.A.

    1998-11-01

    Neutronics analyses are now in progress to support the initial selection of moderator design parameters for the Spallation Neutron Source (SNS). The results of the initial optimization studies involving moderator poison plate location, moderator position, and premoderator performance for the target system are presented in this paper. Also presented is an initial study of the use of a composite moderator to produce a liquid methane like spectrum.

  20. Cold neutron gain calculations for the NBSR using MCNP

    SciTech Connect

    Williams, R.E.; Rowe, J.M. ); Blau, M. )

    1993-01-01

    The existing D[sub 2]O-ice cold neutron source in the 20-MW National Bureau of Standards reactor (NBSR) will be replaced in 1994 with a liquid-hydrogen (LH2) source, to increase the yield of cold neutrons (X > 0.4 nm). Two series of Monte Carlo calculations using MCNP were performed to determine the optimum cold moderator geometry and to verify its performance. Only the region near the cryostat was modeled for the first series of calculations, leading to the choice of a spherical annulus for the LH[sub 2] source. A complete MCNP model of the core was subsequently developed.

  1. 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.

  2. 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. PMID:21964903

  3. 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.

  4. A liquid-hydrogen cold neutron source for the NBSR

    SciTech Connect

    Williams, R.E.; Roew, J.M.; Kopetka, P. )

    1992-01-01

    The National Bureau of Standards Reactor (NBSR) is a 20-MW research reactor operated by the National Institute of Standards and Technology. It was designed with a 55-cm-diam beamport for the purpose of installing a D[sub 2]O-ice cold neutron source, completed in 1987. The success of the cold source led to the construction of the Cold Neutron Research Facility, an experimental hall ultimately to have 7 neutron guides and 15 instruments. A liquid-hydrogen cold neutron source is being developed to replace the D[sub 2]O ice in order to increase the cold neutron yield. A simple, passively safe system has been designed with multiple barriers that prevent air from mixing with hydrogen. A thermosiphon will be used to maintain the liquid-hydrogen inventory in the moderator chamber. The thermosiphon relies on natural circulation; no pumps or moving parts are required to adequately cool the moderator chamber. The hydrogen condenser is cooled by a 3.5-kW helium refrigerator. A ballast tank is connected to the condenser so the entire hydrogen inventory can expand freely into the tank, providing completely passive protection against refrigerator failures.

  5. Experimental investigation of new neutron moderator materials

    SciTech Connect

    Mocko, Michal; Daemen, Luke L; Hartl, Monika; Huegle, Thomas; Muhrer, Guenter

    2010-01-01

    In this study we present experimental investigation of thermal neutron energy spectra produced by lead and bismuth hydroxides (Pb(OH){sub 2}, and Bi(OH){sub 3}). The experimental energy spectra are compared with a thermal neutron energy spectrum of water measured in the same geometry. We present an MCNPX geometry model used to help with the experimental data interpretation. We demonstrate a very good reproduction of the experimental thermal neutron energy spectrum produced by the water moderator. We show a sensitivity study with the Pb(OH){sub 2}, and Bi(OH){sub 3} materials on different combinations of thermal neutron scattering kernels.

  6. 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.

  7. Physics design of a cold neutron source for KIPT neutron source facility.

    SciTech Connect

    Zhong, Z.; Gohar, Y.; Kellogg, R.; Nuclear Engineering Division

    2009-02-17

    Argonne National Laboratory (ANL) of USA and Kharkov Institute of Physics and Technology (KIPT) of Ukraine have been collaborating on the conceptual design development of a neutron source facility. It is based on the use of an electron accelerator driven subcritical (ADS) facility with low enriched uranium fuel, using the existing electron accelerators at KIPT of Ukraine [1]. The neutron source of the subcritical assembly is generated from the interaction of 100-KW electron beam, which has a uniform spatial distribution and the electron energy in the range of 100 to 200 MeV, with a natural uranium target [2]. The main functions of the facility are the production of medical isotopes and the support of the Ukraine nuclear power industry. Neutron beam experiments and material studies are also included. Over the past two-three decades, structures with characteristic lengths of 100 {angstrom} and correspondingly smaller vibrational energies have become increasingly important for both science and technology [3]. The characteristic dimensions of the microstructures can be well matched by neutrons with longer vibrational wavelength and lower energy. In the accelerator-driven subcritical facility, most of the neutrons are generated from fission reactions with energy in the MeV range. They are slowed down to the meV energy range through scattering reactions in the moderator and reflector materials. However, the fraction of neutrons with energies less than 5 meV in a normal moderator spectrum is very low because of up-scattering caused by the thermal motion of moderator or reflector molecules. In order to obtain neutrons with energy less than 5 meV, cryogenically cooled moderators 'cold neutron sources' should be used to slow down the neutrons. These cold moderators shift the neutron energy spectrum down because the thermal motion of moderator molecules as well as the up-scattering is very small, which provides large gains in intensity of low energy neutrons, E < 5 meV. The

  8. Current status of advanced pelletized cold moderators development for IBR-2M research reactor

    NASA Astrophysics Data System (ADS)

    Kulikov, S.; Belyakov, A.; Bulavin, M.; Mukhin, K.; Shabalin, E.; Verhoglyadov, A.

    2013-03-01

    The world's first advanced pelletized cold neutron moderator is prepared to be put into operation at the IBR-2M pulsed research reactor. It provides long-wavelength neutrons to the most of neutron spectrometers at the beams of the IBR-2M reactor. Aromatic hydrocarbons are used as a material for cold moderators. It is a very attractive material because of its high radiation resistance, good moderating properties, incombustibility, etc. It is shown that the idea of beads transport by a helium flow at cryogenic temperatures is successful. The recent progress and plans for moderator development at the IBR-2M reactor as well as the experimental results of beads transport are discussed in the paper.

  9. 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.

  10. 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.

  11. 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%.

  12. The Advanced Neutron Source liquid deuterium cold source

    SciTech Connect

    Lucas, A.T.

    1995-08-01

    The Advanced Neutron Source will employ two cold sources to moderate neutrons to low energy (<10 meV). The cold neutrons produced are then passed through beam guides to various experiment stations. Each cold source moderator is a sphere of 410-mm internal diameter. The moderator material is liquid deuterium flowing at a rate of 1 kg/s and maintained at subcooled temperatures at all points of the circuit, to prevent boiling. Nuclear beat deposited within the liquid deuterium and its containment structure totals more than 30 kW. All of this heat is removed by the liquid deuterium, which raises its temperature by 5 K. The liquid prime mover is a cryogenic circulator that is situated in the return leg of the flow loop. This arrangement minimizes the heat added to the liquid between the heat exchanger and the moderator vessel, allowing the moderator to be operated at the minimum practical temperature. This report describes the latest thinking at the time of project termination. It also includes the status of various systems at that time and outlines anticipated directions in which the design would have progressed. In this regard, some detail differences between this report and official design documents reflect ideas that were not approved at the time of closure but are considered noteworthy.

  13. Shaping micron-sized cold neutron beams

    NASA Astrophysics Data System (ADS)

    Ott, Frédéric; Kozhevnikov, Sergey; Thiaville, André; Torrejón, Jacob; Vázquez, Manuel

    2015-07-01

    In the field of neutron scattering, the need for micro-sized (1-50 μm) thermal or cold neutron beams has recently appeared, typically in the field of neutron imaging to probe samples with a high spatial resolution. We discuss various possibilities of producing such micro-sized neutron beams. The advantages and drawbacks of the different techniques are discussed. We show that reflective optics offers the most flexible way of producing tiny neutron beams together with an enhanced signal to background ratio. The use of such micro beams is illustrated by the study of micrometric diameter magnetic wires.

  14. 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.

  15. Compact thermal neutron sensors for moderator-based neutron spectrometers.

    PubMed

    Pola, A; Bortot, D; Introini, M V; Bedogni, R; Gentile, A; Esposito, A; Gómez-Ros, J M; Passoth, E; Prokofiev, A

    2014-10-01

    In the framework of the NESCOFI@BTF project of the Italian Institute of Nuclear Physics, different types of active thermal neutron sensors were studied by coupling semiconductor devices with a suitable radiator. The objective was to develop a detector of small dimensions with a proper sensitivity to use at different positions in a novel moderating assembly for neutron spectrometry. This work discusses the experimental activity carried out in the framework of the ERINDA program (PAC 3/9 2012) to characterise the performance of a thermal neutron pulse detector based on (6)Li. PMID:24277874

  16. Polarized Cold Neutron Capture in ^27Al

    NASA Astrophysics Data System (ADS)

    Balascuta, Septimiu

    2013-04-01

    The NPDGamma Experiment at the Spallation Neutron Source at ORNL is measuring the parity-odd correlation between the neutron spin and the direction of the emitted photon in the capture of cold neutrons on a 16-liter liquid parahydrogen target. The goal is to determine the strength of the weak nucleon-nucleon interaction. One of the main background contributions comes from the gamma rays produced by neutrons captured in the Al walls of the target vessel. To quantify this effect a commissioning experiment measured the parity-odd and parity-even asymmetries in the angular distribution of the gamma rays from the capture of polarized cold neutrons in a solid Al target. A status of the analysis of this experiment will be presented.

  17. 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.

  18. 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.

  19. New Pulsed Cold Neutron Beam Line for Fundamental Nuclear Physics at LANSCE

    PubMed Central

    Seo, P.-N.; Bowman, J. D.; Gericke, M.; Gillis, R. C.; Greene, G. L.; Leuschner, M. B.; Long, J.; Mahurin, R.; Mitchell, G. S.; Penttila, S. I.; Peralta, G.; Sharapov, E. I.; Wilburn, W. S.

    2005-01-01

    The NPDGamma collaboration has completed the construction of a pulsed cold neutron beam line on flight path12 at the Los Alamos Neutron Science Center (LANSCE). We describe the new beam line and characteristics of the beam. We report results of the moderator brightness and the guide performance measurements. FP12 has the highest pulsed cold neutron intensity for nuclear physics in the world. PMID:27308111

  20. New Pulsed Cold Neutron Beam Line for Fundamental Nuclear Physics at LANSCE.

    PubMed

    Seo, P-N; Bowman, J D; Gericke, M; Gillis, R C; Greene, G L; Leuschner, M B; Long, J; Mahurin, R; Mitchell, G S; Penttila, S I; Peralta, G; Sharapov, E I; Wilburn, W S

    2005-01-01

    The NPDGamma collaboration has completed the construction of a pulsed cold neutron beam line on flight path12 at the Los Alamos Neutron Science Center (LANSCE). We describe the new beam line and characteristics of the beam. We report results of the moderator brightness and the guide performance measurements. FP12 has the highest pulsed cold neutron intensity for nuclear physics in the world. PMID:27308111

  1. The decompression of cold neutron star matter

    NASA Technical Reports Server (NTRS)

    Lattimer, J. M.; Mackie, F.; Ravenhall, D. G.; Schramm, D. N.

    1977-01-01

    The ejection of cold neutron-star matter is examined, and an attempt is made to determine whether the final composition of this matter may be similar to that normally associated with the hot high-neutron-flux r-process. A semiempirical liquid-drop model is used for the nucleus, and the equilibrium composition of the matter is determined by assuming it to be in its absolute ground state at a given density. Physical mechanisms operating during the expansion are analyzed, and the composition of the ejected matter is found as a function of its density during expansion. The results indicate that it is virtually impossible for deuterium to form, that neutrons can be captured only after beta decay increases the atomic numbers of nuclei, and that no free neutrons can escape. It is concluded that neutron-star ejecta can produce heavy neutron-rich nuclei and may produce somewhat heavier nuclei than a standard r-process.

  2. Precision Polarimetry for Cold Neutrons

    NASA Astrophysics Data System (ADS)

    Barron-Palos, Libertad; Bowman, J. David; Chupp, Timothy E.; Crawford, Christopher; Danagoulian, Areg; Gentile, Thomas R.; Jones, Gordon; Klein, Andreas; Penttila, Seppo I.; Salas-Bacci, Americo; Sharma, Monisha; Wilburn, W. Scott

    2007-10-01

    The abBA and PANDA experiments, currently under development, aim to measure the correlation coefficients in the polarized free neutron beta decay at the FnPB in SNS. The polarization of the neutron beam, polarized with a ^3He spin filter, has to be known with high precision in order to achieve the goal accuracy of these experiments. In the NPDGamma experiment, where a ^3He spin filter was used, it was observed that backgrounds play an important role in the precision to which the polarization can be determined. An experiment that focuses in the reduction of background sources to establish techniques and find the upper limit for the polarization accuracy with these spin filters is currently in progress at LANSCE. A description of the measurement and results will be presented.

  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. Nuclear heat load calculations for the NBSR cold neutron source using MCNP

    SciTech Connect

    Blau, M. ); Rowe, J.M.; Williams, R.E. )

    1993-01-01

    A liquid-hydrogen (LH2) cold neutron source is being designed for installation in the 20-MW National Bureau of Standards reactor (NBSR) at National Institute of Standards and Technology to replace the D[sub 2]O-ice cold source currently in use. An accurate estimate of the heat deposited in the cold source is needed to ensure that it can be adequately cooled for successful operation. The heat load is caused by the interaction of neutrons and gamma rays with the cold moderator and the walls of the moderator chamber. The Monte Carlo code, MCNP (Version 4.2), was used to model the entire NBSR core and both the existing and the proposed cold sources. The model was used to calculate not only the heat load but also the reactivity and neutron gain of each source.

  5. Hypohydration effects on thermoregulation during moderate exercise in the cold.

    PubMed

    Kenefick, Robert W; Mahood, Nicholas V; Hazzard, Melissa P; Quinn, Timothy J; Castellani, John W

    2004-08-01

    Hyperosmotic hypovolemia impairs vasoconstriction during sedentary cold exposure. The purpose of this study was to determine whether hypohydration alters thermoregulation and cardiovascular responses to exercise in cold air. On four occasions, eight males [35.1 (2.7) years, 175.5 (3.1) cm, 73.3 (2.6) kg, 57.2 (2.6) ml kg(-1) min(-1) maximal oxygen uptake (VO(2max)), 19.6 (2.4)% fat] walked, in t-shirt, shorts, and shoes, at 50% VO(2max), for 60 min in either a 4 degrees C (Cold) or a 25 degrees C (Temperate) environment in both hypohydrated state (HYPO, -4% body mass) and euhydrated state (EU). During exercise-cold stress, rectal temperature ( T(re)), mean weighted skin temperature, heart rate (HR), cardiac output (CO), and stroke volume (SV) were measured every 20 min. Mean weighted skin temperature values were not different between HYPO and EU but were lower ( P<0.05) in Cold versus Temperate trials. T(re) was not different ( P>0.05) between HYPO-Cold and EU-Cold. CO and SV were not different within hydration states and were not different between Cold and Temperate trials ( P<0.05). HR was not different between HYPO-Cold and EU-Cold. These data demonstrate that moderate intensity exercise in the cold while hypohydrated does not alter metabolic heat production, skin temperatures and heat loss, nor does it increase thermoregulatory and cardiovascular strain. PMID:15045503

  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. 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.

  8. Holographic cold nuclear matter and neutron star

    NASA Astrophysics Data System (ADS)

    Ghoroku, Kazuo; Kubo, Kouki; Tachibana, Motoi; Toyoda, Fumihiko

    2014-04-01

    We have previously found a new phase of cold nuclear matter based on a holographic gauge theory, where baryons are introduced as instanton gas in the probe D8//lineD8 branes. In our model, we could obtain the equation of state (EOS) of our nuclear matter by introducing Fermi momentum. Then, here we apply this model to the neutron star and study its mass and radius by solving the Tolman-Oppenheimer-Volkoff (TOV) equations in terms of the EOS given here. We give some comments for our holographic model from a viewpoint of the other field theoretical approaches.

  9. 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.

  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

    SciTech Connect

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

    2013-12-15

    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. 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). PMID:24387465

  14. Determination of boron in materials by cold neutron prompt gamma-ray activation analysis.

    PubMed

    Paul, Rick L

    2005-01-01

    An instrument for cold neutron prompt gamma-ray activation analysis (PGAA), located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of boron in a variety of materials. Neutrons, moderated by passage through liquid hydrogen at 20 K, pass through a (58)Ni coated guide to the PGAA station in the cold neutron guide hall of the NCNR. The thermal equivalent neutron fluence rate at the sample position is 9 x 10(8) cm(-2) s(-1). Prompt gamma rays are measured by a cadmium- and lead-shielded high-purity germanium detector. The instrument has been used to measure boron mass fractions in minerals, in NIST SRM 2175 (Refractory Alloy MP-35-N) for certification of boron, and most recently in semiconductor-grade silicon. The limit of detection for boron in many materials is <10 ng g(-1). PMID:15614360

  15. Deterioration of performance of neutron moderators under intense irradiation

    SciTech Connect

    Carpenter, J.M.; Cudrnak, S.S.; DeCusatis, C.M.

    1986-01-01

    In pulsed neutron sources, fixed moderators such as polyethylene and solid methane slow down fast (MeV) neutrons from the primary source to energies of use for spectroscopy (less than or equal to10 eV). Radiation-induced changes in their composition alter their spectral and pulse characteristics. We report the results of fitting time-average spectra from polyethylene and solid methane moderators in Argonne's Intense Pulsed Neutron Source as a function of total fast-neutron radiation dose. The thermal-to-epithermal flux ratio varies most significantly, while the Maxwellian energy and the parameters describing the epithermal component change only slightly. We have used modified forms of Westcott's joining function for this purpose. We provide an integral of the spectrum that is useful for determining the delayed neutron background.

  16. 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.

  17. 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.

  18. Optimizing Moderator Dimensions for Neutron Scattering at the Spallation Neutron Source

    SciTech Connect

    Zhao, Jinkui; Robertson, Lee; Herwig, Kenneth W; Gallmeier, Franz X; Riemer, Bernie

    2013-01-01

    In this work, we investigate the effect of neutron moderator dimensions on the performance of neutron scattering instruments at the Spallation Neutron Source. In a recent study of the planned second target station at the Spallation Neutron Source (SNS) facility [1,2], 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 for a smaller viewing area [4]. 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. We found that the cross-sections of the sample and the neutron guide, respectively, are the deciding factors for choosing the moderator. Beam divergence plays no role as long as it is within the reach of practical constraints. Namely, the required divergence is not too large for the guide or sample to be located close enough to the moderator on an actual spallation source.

  19. 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.

  20. Production and storage of ultra cold neutrons in superfluid helium

    SciTech Connect

    Greene, G.L.; Lamoreaux, S.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL) concerning the investigation of a new method for the experimental exploitation of ultra-cold neutrons. The production and storage of ultra cold neutrons in superfluid helium has been suggested as a tool for the production of high densities of ultra cold neutrons for fundamental nuclear physics as well as for sensitive measurements for condensed matter. A particular application of this technique has been suggested by Doyle and Lamoreaux that involves the trapping of neutrons in a magnetic field within the superfluid helium volume. Neutron decays within the trap volume are detected by the scintillation light produced in the liquid helium. A cryostat and magnetic trap have been constructed as well as a prototype light detection system. This system was installed on a cold neutron beam line at the NIST Cold Neutron Research Facility in the summer of 1997. Preliminary results indicate the detection of helium scintillation light from the detection vessel.

  1. 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.

  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. 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.

  4. Cold Neutrons Trapped in External Fields

    SciTech Connect

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

    2011-01-07

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

  5. Cold neutrons trapped in external fields.

    SciTech Connect

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

    2011-01-05

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

  6. 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

  7. 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.

  8. Biomembranes research using thermal and cold neutrons

    DOE PAGESBeta

    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

  9. 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.

  10. 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.

  11. Cold neutron diffraction contrast tomography of polycrystalline material.

    PubMed

    Peetermans, S; King, A; Ludwig, W; Reischig, P; Lehmann, E H

    2014-11-21

    Traditional neutron imaging is based on the attenuation of a neutron beam through scattering and absorption upon traversing a sample of interest. It offers insight into the sample's material distribution at high spatial resolution in a non-destructive way. In this work, it is expanded to include the diffracted neutrons that were ignored so far and obtain a crystallographic distribution (grain mapping). Samples are rotated in a cold neutron beam of limited wavelength band. Projections of the crystallites formed by the neutrons they diffract are captured on a two dimensional imaging detector. Their positions on the detector reveal their orientation whereas the projections themselves are used to reconstruct the shape of the grains. Indebted to established synchrotron diffraction contrast tomography, this 'cold neutron diffraction contrast tomography' is performed on recrystallized aluminium for experimental comparison between both. Differences between set-up and method are discussed, followed by the application range in terms of sample properties (crystallite size and number, mosaicity and typical materials). Neutron diffraction contrast tomography allows to study large grains in bulky metallic structures. PMID:25274183

  12. 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)

  13. 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.

  14. A small angle neutron scattering (SANS) experiment using very cold neutrons (VCN)

    NASA Astrophysics Data System (ADS)

    Bleuel, M.; Carpenter, J. M.; Micklich, B. J.; Geltenbort, P.; Mishima, K.; Shimizu, H. M.; Iwashita, Y.; Hirota, K.; Hino, M.; Kennedy, S. J.; Lal, J.

    2009-09-01

    This paper describes the results of SANS measurements of small samples using the very cold neutron (VCN) beam of the PF2 instrument at the Institut Laue Langevin (ILL), France. In addition to a classical SANS pinhole collimation, the experiment used a polarizing supermirror as a monochromator and a magnetic sextupole lens to focus the neutron beam in order to gain intensity and avoid any material in the neutron beam besides the sample.

  15. 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

  16. 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.

  17. Measurement of the Neutron Spectrum of the HB-4 Cold Source at the High Flux Isotope Reactor at Oak Ridge National Laboratory

    NASA Astrophysics Data System (ADS)

    Robertson, J. L.; Iverson, E. B.

    2009-08-01

    Measurements of the cold neutron spectrum from the super critical hydrogen cold source at the High Flux Isotope Reactor at Oak Ridge National Laboratory were made using time-of-flight spectroscopy. Data were collected at reactor power levels of 8.5MW, 42.5MW and 85MW. The moderator temperature was also varied. Data were collected at 17K and 25K while the reactor power was at 8.5MW, 17K and 25K while at 42.5MW and 18K and 22K while at 85MW. The purpose of these measurements was to characterize the brightness of the cold source and to better understand the relationship between reactor power, moderator temperature, and cold neutron production. The authors will discuss the details of the measurement, the changes observed in the neutron spectrum, and the process for determining the source brightness from the measured neutron intensity.

  18. The new cold neutron chopper spectrometer at the Spallation Neutron Source: design and performance.

    PubMed

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

    2011-08-01

    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. PMID:21895276

  19. 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.

  20. 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.

  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. 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.

  3. Deuterated polyethylene coatings for ultra-cold neutron applications

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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 × 104 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.

  4. 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.

  5. "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.

  6. 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.

  7. 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.

  8. A Precision Measurement of Neutron Beta Decay Angular Correlations with Polarized Pulsed Cold Neutrons

    NASA Astrophysics Data System (ADS)

    Seo, Pil-Neyo

    2004-05-01

    The abBA collaboration is developing an experiment to measure the neutron beta decay angular correlations, a, b, B, A, to 0.1the very high pulsed cold neutron intensities in a new nuclear physics beam line that is under construction at SNS. The design of the experiment is based on three important technical advances: the pulsed cold neutron beam, a polarized ^3He neutron spin filter, and large-area thin-dead layer silicon detectors. Both electrons and protons resulting from the decay will be guided in the spectrometer by electric and magnetic fields and then detected in coincidence with two 2π large-segmented silicon detectors. Measuring the correlations in the same apparatus provides a redundant measurement of λ=G_A/G_V. I will describe the experiment and report the status of the development.

  9. Designing of the 14 MeV neutron moderator for BNCT

    NASA Astrophysics Data System (ADS)

    Cheng, Dao-Wen; Lu, Jing-Bin; Yang, Dong; Liu, Yu-Min; Wang, Hui-Dong; Ma, Ke-Yan

    2012-09-01

    In boron neutron capture therapy (BNCT), the ratio of the fast neutron flux to the neutron flux in the tumor (RFNT) must be less than 3%. If a D-T neutron generator is used in BNCT, the 14 MeV neutron moderator must be optimized to reduce the RFNT. Based on the neutron moderation theory and the simulation results, tungsten, lead and diamond were used to moderate the 14 MeV neutrons. Satisfying RFNT of less than 3%, the maximum neutron flux in the tumor was achieved with a three-layer moderator comprised of a 3 cm thick tungsten layer, a 14 cm thick lead layer and a 21 cm thick diamond layer.

  10. 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.

  11. 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.

  12. Beam-transport optimization for cold-neutron spectrometer

    NASA Astrophysics Data System (ADS)

    Nakajima, Kenji; Ohira-Kawamura, Seiko; Kikuchi, Tatsuya; Kajimoto, Ryoichi; Takahashi, Nobuaki; Nakamura, Mitsutaka; Soyama, Kazuhiko; Osakabe, Toyotaka

    2015-01-01

    We report the design of the beam-transport system (especially the vertical geometry) for a cold-neutron disk-chopper spectrometer AMATERAS at J-PARC. Based on the elliptical shape, which is one of the most effective geometries for a ballistic mirror, the design was optimized to obtain, at the sample position, a neutron beam with high flux without serious degrading in divergence and spacial homogeneity within the boundary conditions required from actual spectrometer construction. The optimum focal point was examined. An ideal elliptical shape was modified to reduce its height without serious loss of transmission. The final result was adapted to the construction requirements of AMATERAS. Although the ideas studied in this paper are considered for the AMATERAS case, they can be useful also to other spectrometers in similar situations.

  13. Neutron capture studies of 206Pb at a cold neutron beam

    NASA Astrophysics Data System (ADS)

    Schillebeeckx, P.; Belgya, T.; Borella, A.; Kopecky, S.; Mengoni, A.; Quétel, C. R.; Szentmiklósi, L.; Trešl, I.; Wynants, R.

    2013-11-01

    Gamma-ray transitions following neutron capture in 206Pb have been studied at the cold neutron beam facility of the Budapest Neutron Centre using a metallic sample enriched in 206Pb and a natural lead nitrate powder pellet. The measurements were performed using a coaxial HPGe detector with Compton suppression. The observed -rays have been incorporated into a decay scheme for neutron capture in 206Pb . Partial capture cross sections for 206Pb(n,) at thermal energy have been derived relative to the cross section for the 1884keV transition after neutron capture in 14N . From the average crossing sum a total thermal neutron capture cross section of mb was derived for the 206Pb(n,) reaction. The thermal neutron capture cross section for 206Pb has been compared with contributions due to both direct capture and distant unbound s-wave resonances. From the same measurements a thermal neutron-induced capture cross section of mb was determined for the 207Pb(n,) reaction.

  14. 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.

  15. The new cold neutron radiography and tomography instrument CONRAD at HMI Berlin

    NASA Astrophysics Data System (ADS)

    Hilger, A.; Kardjilov, N.; Strobl, M.; Treimer, W.; Banhart, J.

    2006-11-01

    The new cold neutron radiography instrument CONRAD is a multifunctional facility for radiography and tomography with cold neutrons at Hahn-Meitner Institut, Berlin. It is located at the end of a curved neutron guide, which faces the cold-neutron source of the BER-II research reactor. The geometry provides a cold-neutron beam with wavelengths between 2 and 12 Å. Two measuring positions are available for radiography and tomography investigations. The first one is placed at the end of the guide and it is optimized for in situ experiments in which a high neutron flux is required. The available flux at this position is approximately 10 8 cm -2 s -1. The second measuring position uses a pin-hole geometry which allows better beam collimation ( L/ D up to 1000) and higher image resolution in the range of 200 μm in the CCD based detector system (10×10 cm 2). The use of cold neutrons for radiography purposes increases the image contrast and improves the sensibility e.g., the detection of small amounts of water and hydrogen-containing materials in metal matrixes. On the other hand the cold-neutron beam can be modified easily by using diffraction and neutron optical techniques. This enables to perform radiography and tomography experiments with more sophisticated measuring techniques. Recent examples of research and industrial applications will be presented.

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

    DOE PAGESBeta

    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

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

    SciTech Connect

    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 tubes 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.

  18. Search for Neutron Anti-Neutron Oscillation using Cold Neutron Beams with Focusing Optics

    NASA Astrophysics Data System (ADS)

    Shimizu, Hirohiko; NNBar Collaboration

    2014-09-01

    The electric charge of neutrons is experimentally known as less than 10-21 e and considered as exactly zero and the transition between neutron and anti-neutron is allowed in terms of the conservation of the electric charge but is considered forbidden according to the empirical conservation law of the baryon number. On the other hand, the existence of physical processes which violates the conservation of the baryon number is required in the Sakharov's conditions to explain the baryon assymmetry in the big-bang cosmology. The search for the neutron antineutron (n n) oscillation offers information the baryon number violation with the Δ (B - L) = 2 complementary to the attempts with Δ (B - L) = 0 . The sensitivity to the n n oscillation has been improved by searching for the instability of nuclei via n n oscillation in large-scale deep-underground experiments, which are now limited by the background. On the other hand, the improvement of accelerator-driven neutron sources and transport optics of slow neutron beams have introduced new possibility to improve the sensitivity to n n by orders of magnitude. In this paper, we discuss the experimental sensitivity to n n oscillation with accelerator-based neutron sources and neutron focusing optics.

  19. 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)

  20. 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

  1. 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

  2. Physics Analyses in the Design of the HFIR Cold Neutron Source

    SciTech Connect

    Bucholz, J.A.

    1999-09-27

    Physics analyses have been performed to characterize the performance of the cold neutron source to be installed in the High Flux Isotope Reactor at the Oak Ridge National Laboratory in the near future. This paper provides a description of the physics models developed, and the resulting analyses that have been performed to support the design of the cold source. These analyses have provided important parametric performance information, such as cold neutron brightness down the beam tube and the various component heat loads, that have been used to develop the reference cold source concept.

  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.

    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

  5. Filter/moderator system for a BNCT beam of epithermal neutrons at nuclear reactor MARIA

    NASA Astrophysics Data System (ADS)

    Tyminska, Katarzyna

    2009-01-01

    Boron Neutron Capture Therapy is a very promising form of cancer therapy, consisting in irradiating a stable isotope of boron (10B) concentrated in tumor cells with a low energy neutron beam. This technique makes it possible to destroy tumor cells, leaving healthy tissues practically unaffected. In order to carry out the therapy in the proper way, the proper range of the neutron beam energy has to be chosen. In this paper we present a filter/moderator system modeled with MCNP code in order to obtain an epithermal neutron beam for BNCT post at MARIA reactor in Swierk.

  6. 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.

  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. A New Method for Precision Cold Neutron Polarimetry Using a 3He Spin Filter

    PubMed Central

    Wietfeldt, F. E.; Gentile, T. R.

    2005-01-01

    We present a new method for precision measurement of the capture flux polarization of a polychromatic (white), continuous cold neutron beam, polarized by a 3He spin filter. This method allows an in situ measurement and does not require knowledge of the neutron beam wavelength distribution. We show that a polarimetry precision of 0.1 % is possible.

  9. Accelerator-based neutron source using a cold deuterium target with degenerate electrons

    SciTech Connect

    Phillips, R. E.; Ordonez, C. A.

    2013-07-15

    A neutron generator is considered in which a beam of tritons is incident on a hypothetical cold deuterium target with degenerate electrons. The energy efficiency of neutron generation is found to increase substantially with electron density. Recent reports of potential targets are discussed.

  10. 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}.

  11. Powder diffraction in materials science using the KENS cold-neutron source

    SciTech Connect

    Kamiyama, T.; Oikawa, K.; Akiba, E.

    1997-12-01

    Since superconductivity fever spread around the world, neutron powder diffraction has become very popular and been widely used by crystallographers, physicists, chemists, mineralogists, and materials scientists. The purpose of present paper is to show, firstly, important characteristics of time-of-flight TOF powder diffraction using cold-neutron source in the study of materials science, and, secondly, recent studies on the structure and function of batteries at the Neutron Science Laboratory (KENS) in the High Energy Accelerator Research Organization (KEK).

  12. Industrial applications at the new cold neutron radiography and tomography facility of the HMI

    NASA Astrophysics Data System (ADS)

    Kardjilov, N.; Hilger, A.; Manke, I.; Strobl, M.; Treimer, W.; Banhart, J.

    2005-04-01

    The new cold neutron radiography and tomography facility at the Hahn-Meitner-Institut Berlin is suited for the investigation of components and materials from different industrial fields. The high-flux measuring position of the facility allows real-time imaging of fast dynamical processes. Cold neutrons interact stronger with the matter compared to thermal neutrons, which leads to a much better radiography contrast. Some examples of different industry applications like investigations on discharging of a Lithium battery or on oil sediments in a vent pipe are presented.

  13. 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.

  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. ASIC Development for Three-Dimensional Silicon Imaging Array for Cold Neutrons

    SciTech Connect

    Britton, C.L.; Jagadish, U.; Bryan, W.L.

    2004-05-19

    An Integrated Circuit (IC) readout chip with four channels arranged so as to receive input charge from the corners of the chip was designed for use with 5- to 7-mm pixel detectors. This Application Specific IC (ASIC) can be used for cold neutron imaging, for study of structural order in materials using cold neutron scattering or for particle physics experiments. The ASIC is fabricated in a 0.5-{micro}m n-well AMI process. The design of the ASIC and the test measurements made is reported. Noise measurements are also reported.

  16. 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.

  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. Neutron Spectral Brightness of Cold Guide 4 at the High Flux Isotope Reactor

    SciTech Connect

    Winn, B. L.; Robertson, J. L.; Iverson, Erik B.; Selby, D. L.

    2009-05-03

    The High Flux Isotope Reactor resumed operation in June of 2007 with a super-critical hydrogen cold source in horizontal beam tube 4. Cold guide 4 is a guide system designed to deliver neutrons from this source at reasonable flux at wavelengths greater than 4 Å to several instruments, and includes a 15-m, 96-section, 4-channel bender. A time-of-flight spectrum with calibrated detector was recorded at port C of cold guide 4, and compared to McStas simulations, to generate a brightness spectrum.

  19. 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

  20. 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.

  1. Properties of a Cold-Neutron Irradiation Facility for In Vitro Research on Boron Neutron Capture Therapy at the Geesthacht Neutron Facility

    SciTech Connect

    Luedemann, L.; Kampmann, R.; Sosaat, W.; Staron, P.; Wille, P.

    2000-05-15

    A new irradiation facility, GBET (basic research on boron neutron capture therapy), especially designed for in vitro experiments on boron neutron capture therapy was put into operation at the Geesthacht Neutron Facility of the GKSS Research Center. Its location at a cold-neutron guide without direct view of the reactor core has two advantages: First, contamination of the primary beam with fast neutrons or photons is negligible. Second, GBET yields a high cold-neutron flux of 1.4 x 10{sup 8}/(cm{sup 2}.s) over an area of 3 x 4 cm. As a result of the energy dependence of the neutron absorption cross section of boron, this corresponds to a higher effective thermal flux of 4.7 x 10{sup 8}/(cm{sup 2}.s). This effect is used to reduce the irradiation times by a factor of 3.32.The effective flux is sufficient for irradiation of thin samples like cell monolayers in conventional culture flasks. For such in vitro irradiations, a survival fraction of 1% is achieved at a homogeneous boron concentration of 100 ppm {sup 10}B within {approx}20 min. Furthermore, the beam can be used for boron radiography. The respective experimental conditions are discussed, especially the neutron flux distribution, available for these different types of samples.

  2. 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.

  3. 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. PMID:26298435

  4. 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.

  5. 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.

  6. 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.

  7. Cold neutron depth profiling of lithium-ion battery materials

    NASA Astrophysics Data System (ADS)

    Lamaze, G. P.; Chen-Mayer, H. H.; Becker, D. A.; Vereda, F.; Goldner, R. B.; Haas, T.; Zerigian, P.

    We report the characterization of two thin-film battery materials using neutron techniques. Neutron depth profiling (NDP) has been employed to determine the distribution of lithium and nitrogen simultaneously in lithium phosphorous oxynitride (LiPON) deposited by ion beam assisted deposition (IBAD). The depth profiles are based on the measurement of the energy of the charged particle products from the 6Li(n,α) 3H and 14N(n,p) 14C reactions for lithium and nitrogen, respectively. Lithium at the level of 10 22 atoms/cm 3 and N of 10 21 atoms/cm 3, distributed in the film thickness on the order of 1 μm, have been determined. This information provides insights into nitrogen incorporation and lithium concentration in the films under various fabrication conditions. NDP of lithium has also been performed on IBAD LiCoO 2 films, in conjunction with instrumental neutron activation analysis (INAA) to determine the cobalt concentration. The Li/Co ratio thus obtained serves as an ex situ control for the thin-film evaporation process. The non-destructive nature of the neutron techniques is especially suitable for repeated analysis of these materials and for actual working devices.

  8. Development of modulating permanent magnet sextupole lens for focusing of pulsed cold neutrons

    NASA Astrophysics Data System (ADS)

    Yamada, Masako; Iwashita, Yoshihisa; Ichikawa, Masahiro; Sugimoto, Takanori; Tongu, Hiromu; Fujisawa, Hiroshi; Shimizu, Hirohiko M.; Ino, Takashi; Mishima, Kenji; Taketani, Kaoru; Yoshioka, Tamaki; Muto, Suguru; Morishima, Takahiro; Oku, Takayuki; Suzuki, Jun-ichi; Shinohara, Takenao; Sakai, Kenji; Sato, Hiromi; Hirota, Katsuya; Otake, Yoshie; Seki, Yoshichika; Kawasaki, Shinsuke; Komamiya, Sachio; Kamiya, Yoshio; Otono, Hidetoshi; Yamashita, Satoru; Geltenbort, Peter

    2009-09-01

    Modulating permanent magnet sextupole lens (PMSx) for focusing pulsed cold neutrons is under development. The synchronized modulation of its field gradient suppresses the chromatic aberration which arises from the Time Of Flight method. The strength of the magnetic field, the torque, and the rise of temperature during its operation are studied on a fabricated prototype. Experiments on focusing pulsed very cold neutrons (VCN) at ILL (Institute of Laue Langevin, France) were carried out and VCN with around λ=40 Å were focused by the PMSx at a focal length of about 0.5 m. The experimental results are presented in conjunction with the principle of the neutron focusing and the modulating method of the focal strength of permanent magnet lens with the double ring structure.

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

    SciTech Connect

    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.

  10. Pulsed ultra-cold neutron production using a Doppler shifter at J-PARC

    NASA Astrophysics Data System (ADS)

    Imajo, S.; Mishima, K.; Kitaguchi, M.; Iwashia, Y.; Yamada, N. L.; Hino, M.; Oda, T.; Ino, T.; Shimizu, H. M.; Yamashita, S.; Katayama, R.

    2016-01-01

    We have constructed a Doppler-shifter-type pulsed ultra-cold neutron (UCN) source at the Materials and Life Science Experiment Facility of the Japan Proton Accelerator Research Complex. Very cold neutrons (VCNs) with 136 m s^{-1} velocity in a neutron beam supplied by a pulsed neutron source are decelerated by reflection on an m=10 wide-band multilayer mirror, yielding pulsed UCNs. The mirror is fixed to the tip of a 2000 rpm rotating arm moving with 68 m s^{-1} velocity in the same direction as the VCNs. The repetition frequency of the pulsed UCNs is 8.33 Hz and the time width of the pulse at production is 4.4 ms. In order to increase the UCN flux, a supermirror guide, wide-band monochromatic mirrors, focus guides, and a UCN extraction guide have been newly installed or improved. The 1 MW-equivalent count rate of the output neutrons with longitudinal wavelengths longer than 58 nm is 1.6 × 102 cps, while that of the true UCNs is 80 cps. The spatial density at production is 1.4 UCN cm^{-3}. This new UCN source enables us to research and develop apparatuses necessary for the investigation of the neutron electric dipole moment.

  11. 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.

  12. Production of ultra cold neutrons by a doppler shifter with pulsed neutrons at J-PARC

    NASA Astrophysics Data System (ADS)

    Mishima, K.; Imajo, S.; Hino, M.; Ino, T.; Iwashita, Y.; Katayama, R.; Kitaguchi, M.; Oda, T.; Shimizu, H. M.; Utsuro, M.; Yamashita, S.; Yoshioka, T.

    2014-07-01

    Ultracold neutrons (UCNs) are neutrons whose kinetic energy is around a few hundred nanoelectronvolts. Neutrons with such small kinetic energy can be trapped in a material vessel or magnetic fields. Because of these unique characteristics, UCNs are used for some important experiments of fundamental physics. The Doppler shifter is a device to produce UCN by slowing them down by the reflection on a mirror moving with half of the velocity of incoming neutrons. A Doppler shifter using a quadruple-stack of monochromatic supermirrors that reflects neutrons with a velocity around 68m/s [1, Hino et al.(2010)] was fabricated, and operated with a pulsed neutron source of J-PARC. An important feature of the Doppler shifter is the use of a pulsed neutron beam. Unlike in continuous neutron beams, the neutron velocity can be selected by choosing a time slice in a pulsed neutron bunch. Thus the UCN production improves by ~80 times in the case of J-PARC. We successfully produced the UCNs by the Doppler shifter: the measured UCN production rate is consistent with the simulations.

  13. Development of a cold-neutron reflectometer (CN REF-V) at the HANARO

    NASA Astrophysics Data System (ADS)

    Lee, Jeong-Soo; Koo, Jaseung; So, Ji-Yong; Kim, Tae Ho; Park, Sungkyun

    2015-11-01

    A new neutron reflectometer, CN REF-V, has been installed in the cold-neutron laboratory building at the HANARO, a research reactor in Korea. The instrument has a vertical scattering plane and uses a constant wavelength of λ = 4.7535 Å, and it is monochromated by using pyrolytic graphite (PG) crystals. Its measurable minimum reflectivity and maximum momentum transfer for typical solid films are 10-8 and 0.3 Å-1, respectively. A liquid-nitrogen-cooled beryllium filter is used to remove λ/2 contamination due to the PG (002) crystals. With a gold wire activation analysis method, the neutron flux at its sample position was measured and found to be 5.67 × 105 neutrons/cm2 /s. Reflectivity measurements of thin films were successfully carried out with the instrument. A detailed characterization of the instrument and the results of the reflectivity measurements are described.

  14. 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.

  15. Magnetic compound refractive lens for focusing and polarizing cold neutron beams.

    PubMed

    Littrell, K C; te Velthuis, S G E; Felcher, G P; Park, S; Kirby, B J; Fitzsimmons, M R

    2007-03-01

    Biconcave cylindrical lenses are used to focus beams of x rays or neutrons using the refractive properties of matter. In the case of neutrons, the refractive properties of magnetic induction can similarly focus and simultaneously polarize the neutron beam without the concomitant attenuation of matter. This concept of a magnetic refractive lens was tested using a compound lens consisting of 99 pairs of cylindrical permanent magnets. The assembly successfully focused the intensity of a white beam of cold neutrons of one spin state at the detector, while defocusing the other. This experiment confirmed that a lens of this nature may boost the intensity locally by almost an order of magnitude and create a polarized beam. An estimate of the performance of a more practically dimensioned device suitable for incorporation in reflectometers and slit-geometry small angle scattering instruments is given. PMID:17411211

  16. A Precision Measurement of Neutron {beta}-Decay Angular Correlations with Pulsed Cold Neutrons -- The abBA Experiment

    SciTech Connect

    Seo, P.-N.; Bowman, J.D.; O'Donnell, J.M.; Mitchell, G.S.; Penttilae, S.I.; Wilburn, W.S.; Calarco, J.R.; Hersman, F.W.; Chupp, T.E.; Cianciolo, T.V.; Rykaczewski, K.P.; Young, G.R.; Desai, D.; Grzywacz, R.K.; Souza, R.T. de; Snow, W.M.; Frlez, E.; Pocanic, D.; Gentile, T.; Greene, G.L.

    2005-05-24

    The abBA collaboration is developing a new type of field-expansion spectrometer to measure neutron beta decay angular parameters, a, b, B, and A, to the 0.1% precision level. This precision will be achieved by combining three new technical approaches; a pulsed cold neutron beam, a 3He neutron spin filter, and segmented large-area thin-dead layer silicon detectors. Both the electron and proton resulting from the decay will be guided by electric and magnetic fields and detected in coincidence by two 2{pi} solid-angle silicon detectors. For the neutron polarization-dependent observables A and B, a novel precision neutron polarimetry technique has been developed. The parameters a and b will be obtained from the proton time-of-flight and the measured electron energy spectrum. Measurement of the four parameters in the same apparatus provides a redundant determination of parameter {lambda}=gA/gV, providing a test of the standard electroweak interaction.

  17. A Precision Measurement of Neutron β-Decay Angular Correlations with Pulsed Cold Neutrons — The abBA Experiment

    NASA Astrophysics Data System (ADS)

    Seo, P.-N.; Bowman, J. D.; Calarco, J. R.; Chupp, T. E.; Cianciolo, T. V.; Desai, D.; De Souza, R. T.; O'Donnell, J. M.; Frlež, E.; Gentile, T.; Greene, G. L.; Grzywacz, R. K.; Gudkov, V.; Hersman, F. W.; Jones, G. L.; Mitchell, G. S.; Penttilä, S. I.; Počanić, D.; Rykaczewski, K. P.; Snow, W. M.; Wilburn, W. S.; Young, G. R.

    2005-05-01

    The abBA collaboration is developing a new type of field-expansion spectrometer to measure neutron beta decay angular parameters, a, b, B, and A, to the 0.1% precision level. This precision will be achieved by combining three new technical approaches; a pulsed cold neutron beam, a 3He neutron spin filter, and segmented large-area thin-dead layer silicon detectors. Both the electron and proton resulting from the decay will be guided by electric and magnetic fields and detected in coincidence by two 2π solid-angle silicon detectors. For the neutron polarization-dependent observables A and B, a novel precision neutron polarimetry technique has been developed. The parameters a and b will be obtained from the proton time-of-flight and the measured electron energy spectrum. Measurement of the four parameters in the same apparatus provides a redundant determination of parameter λ=gA/gV, providing a test of the standard electroweak interaction.

  18. 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.

  19. 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

  20. New Converging Collimator for Cold Neutrons Time-Of-Flight Measurements

    NASA Astrophysics Data System (ADS)

    Naguib, K.; Sallam, O. H.; Salama, Mohamed

    An idea to design a new converging collimator for cold neutron time-of-flight measurements is presented. Using this new facility in combination with a neutron time-of-flight spectrometer, we may have neutron intensity gain factors about three times that obtained using the conventional straight slit collimators. Expressions for calculating the collimators dimensions as well as the intensity gain and the time resolution broading were presented.Translated AbstractEin neuer, konvergierender Kollimator für Flugzeitmessungen mit langsamen NeutronenDie Idee der Konstruktion eines neuen, konvergierenden Kollimators für Flugzeitmessungen mit langsamen Neutronen wird vorgestellt. Mit diesem neuen Gerät in Kombination mit einem Neutronenflugzeitspektrometer sollte sich ein Intensitätsgewinn von drei gegenüber konventionellen Anordnungen ergeben. Die Kollimatordimensionen, der Intensitätsgewinn und die Verbreiterung der Zeitauflösung werden berechnet.

  1. 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.

  2. Flexible polyvinyl chloride neutron guides for transporting ultracold and very cold neutrons

    SciTech Connect

    Arzumanov, S. S. Bondarenko, L. N.; Geltenbort, P.; Morozov, V. I.; Nesvizhevsky, V. V.; Panin, Yu. N.; Strepetov, A. N.; Chuvilin, D. Yu.

    2011-12-15

    The transmission of ultracold neutrons (UCNs) through flexible polyvinyl chloride (PVC) tubes with lengths of up to 3 m and an internal diameter of 6-8 mm has been studied. High UCN transmission is found even for arbitrarily bent tubes (single bend, double bend, triple bend, figure eight, etc.). The transmission can be improved significantly by coating the inner surface of the tube with a thin layer of liquid fluorine polymer. The prospects of these neutron guides in fundamental and applied research are discussed.

  3. 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}.

  4. Solid-methane moderator systems at KENS

    SciTech Connect

    Furusaka, M.

    1997-09-01

    An overview of the target-moderator-reflector assembly (TMRA) systems at the Neutron Science Laboratory (KENS) at the High Energy Accelerator Research Organization (KEK) is described together with the historical changes. Because of the optimized design of TMRA, the neutron-generation efficiency is very high. The characteristics of the cold moderator system, such as the absolute intensity, spectrum and radiation damage to it, are also described. There are a number of new neutron-scattering instruments which are being viewed at the moderator. A brief description of the proposed TMRA for our future project is also given. (auth)

  5. 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

  6. Optimized geometry for bulk coal PGNAA with external moderation of the source neutrons

    NASA Astrophysics Data System (ADS)

    Oliveira, C.; Salgado, J.; Carvalho, F. G.

    1995-10-01

    A simulation study of a PGNAA system for the analysis of coal with a 252Cf neutron source has been carried out using the MCNP code to investigate the effect on the system response of variable thickness, density and composition of the sample when the source is placed at the center of a moderating sphere of polyethylene. Results for different radii of the moderating sphere are reported. The results show that the geometry of the measuring arrangement can be chosen so that the γ count rate/wt % of an arbitrary element (including hydrogen) is independent both of the hydrogen content of the coal, ωH, expressed as a mass fraction, and of the bulk density, d, or volume hydrogen content of the sample νH, at least in the range of ωH-values commonly found in bituminous coals. The system response, defined as the magnitude of the output signal/wt % of an arbitrary element in the coal composition is then independent of composition and bulk density of the coal sample.

  7. 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.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-11-01

    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 nonevaporative 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.

  10. The rotation of scissioning nucleus considered trajectory calculations for ternary fission induced by cold polarized neutrons

    NASA Astrophysics Data System (ADS)

    Guseva, I.; Gusev, Yu.

    2009-10-01

    On the base of modified trajectory calculations the shift of angular distribution of α-particles accompanied the reaction 235U(n,f) induced by cold polarized neutrons is evaluated. It was supposed that angular distribution shift is caused by the rotation of nuclear system before scission. The orientation of a rotation motion is determined by the neutron spin polarization along and opposite to the beam direction. For the first time the estimation was done in the frame of trajectory calculations assuming the rotation motion of scissioning nucleus [1]. The result of the calculation is in a good agreement with experimental data of paper [2], where this new phenomenon was named as ROT-effect.

  11. 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.

  12. Helium refrigerator maintenance and reliability at the OPAL cold neutron source

    NASA Astrophysics Data System (ADS)

    Thiering, Russell; Taylor, David; Lu, Weijian

    2012-06-01

    Australia's first Cold Neutron Source (CNS) is a major asset to its nuclear research program. The CNS, and associated helium refrigerator, was commissioned in 2006 and is operated at the Open Pool Light Water nuclear Reactor (OPAL). The OPAL CNS operates a 20K, 5 kW Brayton cycle helium refrigerator. In this paper relevant experiences from helium refrigerator operation, maintenance and repair are presented along with the lessons learnt from a series of technical investigations. Turbine failure, due to volatile organic species, is discussed along with the related compressor oil degradation and oil separation efficiency.

  13. 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.

  14. Opacities and spectra of hydrogen atmospheres of moderately magnetized neutron stars

    NASA Astrophysics Data System (ADS)

    Potekhin, A. Y.; Chabrier, G.; Ho, W. C. G.

    2014-12-01

    Context. There is observational evidence that central compact objects (CCOs) in supernova remnants have moderately strong magnetic fields B ~ 1011 G. Meanwhile, available models of partially ionized hydrogen atmospheres of neutron stars with strong magnetic fields are restricted to B ≳ 1012 G. Extension of the applicability range of the photosphere models to lower field strengths is complicated by a stronger asymmetry of decentered atomic states and by the importance of excited bound states. Aims: We extend the equation of state and radiative opacities, as presented in previous papers for 1012G ≲ B ≲ 1015 G, to weaker fields. Methods: We constructed analytical fitting formulae for binding energies, sizes, and oscillator strengths for different bound states of a hydrogen atom moving in moderately strong magnetic fields and calculate an extensive database for photoionization cross sections of such atoms. Using these atomic data, in the framework of the chemical picture of plasmas we solved the ionization equilibrium problem and calculated thermodynamic functions and basic opacities of partially ionized hydrogen plasmas at these field strengths. Then plasma polarizabilities were calculated from the Kramers-Kronig relation, and the radiative transfer equation for the coupled normal polarization modes was solved to obtain model spectra. Results: An equation of state and radiative opacities for a partially ionized hydrogen plasma are obtained at magnetic fields B, temperatures T, and densities ρ typical for atmospheres of CCOs and other isolated neutron stars with moderately strong magnetic fields. The first- and second-order thermodynamic functions, monochromatic radiative opacities, and Rosseland mean opacities are calculated and tabulated, considering partial ionization, for 3 × 1010G ≲ B ≲ 1012 G, 105 K ≲ T ≲ 107 K, and a wide range of densities. Atmosphere models and spectra are calculated to verify the applicability of the results and to determine

  15. 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.

  16. 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.

  17. Development of low temperature solid state detectors for ultra-cold neutrons within superfluid 4He

    NASA Astrophysics Data System (ADS)

    Baker, C. A.; Balashov, S. N.; Green, K.; van der Grinten, M. G. D.; Iaydjiev, P. S.; Ivanov, S. N.; Pendlebury, J. M.; Shiers, D. B.; Tucker, M. A. H.; Yoshiki, H.; Geltenbort, P.

    2003-04-01

    As part of an R&D programme for the development of a next-generation experiment to measure the neutron electric dipole moment, in which ultra-cold neutrons (UCN) are produced and stored in superfluid 4He (superthermal source), we have developed cryogenic detectors of UCN that can operate in situ within the superfluid. Surface barrier detectors and PIN diode detectors have been tested and proven to work well at temperatures as low as 80 mK. When combined with a layer of 6LiF which converts neutrons to charged particles, these detectors form a reliable UCN detection system which has been tested in liquid helium down to 430 mK. The detectors have operated within superfluid helium for periods of up to 30 days with no signs of degradation. The development of this detection system has enabled us to measure the flux of UCN from a superthermal UCN source with no intervening transmission windows which can attenuate the flux. The addition of thin films of magnetically aligned iron also enables these detectors to be used in situ for neutron spin-polarisation analysis.

  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. PMID:10676516

  19. 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

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

    PubMed Central

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

    2005-01-01

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

  1. 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)

  2. 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.

  3. Preliminary probabilistic design accident evaluation of the cold source facilities of the advanced neutron source

    SciTech Connect

    Harrington, R.M.; Ramsey, C.T.

    1995-08-01

    Consistent with established Advanced Neutron Source (ANS) project policy for the use of probabilistic risk assessment (PRA) in design, a task has been established to use PRA techniques to help guide the design and safety analysis of the ANS cold sources. The work discussed in this report is the first formal output of the cold source PRA task. The major output at this stage is a list of design basis accidents, categorized into approximate frequency categories. This output is expected to focus attention on continued design work to define and optimize the design such that design basis accidents are better defined and have acceptable outcomes. Categorizing the design basis events (DBEs) into frequency categories should prove helpful because it will allow appropriate acceptance criteria to be applied. Because the design of the cold source is still proceeding, it is beyond the scope of this task to produce detailed event probability calculations or even, in some cases, detailed event sequence definitions. That work would take place as a logically planned follow-on task, to be completed as the design matures. Figure 1.1 illustrates the steps that would typically be followed in selecting design basis accidents with the help of PRA. Only those steps located above the dashed line on Fig. 1.1 are included in the scope of the present task. (Only an informal top-level failure modes and effects analysis was done.) With ANS project closeout expected in the near future, the scope of this task has been abbreviated somewhat beyond the state of available design information on the ANS cold sources, or what could be achieved in a reasonable time. This change was necessary to ensure completion before the closeout and because the in-depth analytical support necessary to define fully some of the accidents has already been curtailed.

  4. The upgrade of the cold neutron three-axis spectrometer IN12 at the ILL

    NASA Astrophysics Data System (ADS)

    Schmalzl, K.; Schmidt, W.; Raymond, S.; Feilbach, H.; Mounier, C.; Vettard, B.; Brückel, T.

    2016-05-01

    After nearly 40 years of successful operation the cold three-axis spectrometer IN12 at the Institut Laue-Langevin, Grenoble, France, has been relocated to a new position and the primary spectrometer has been upgraded. Latest modern optical components are employed. A new guide in combination with a virtual source concept and a double focusing monochromator guarantee highest flux. With its high unpolarized and polarized neutron flux IN12 allows for demanding experiments. A velocity selector in the guide ensures a clean beam and a very low background. A gain in flux of about an order of magnitude at the sample position has been achieved compared to the previous instrument and IN12's wavelength range now extends far into the warmish region.

  5. The New Cold Neutron Radiography Facility (CNRF) at the Mianyang Research Reactor of the China Academy of Engineering Physics

    NASA Astrophysics Data System (ADS)

    Bin, Tang; Heyong, Huo; Ke, Tang; Rogers, John; Haste, Martin; Christodoulou, Marios

    A new cold neutron radiography beamline has been designed and constructed for the Mianyang reactor at the Institute of Nuclear Physics and Chemistry of the China Academy of Engineering Physics. This paper describes the components of the system and demonstrates the achievable image resolution.

  6. 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.

  7. Optimization of a moderator-neutron guide system for diffractometers of beam line 7A of the IBR-2M reactor

    NASA Astrophysics Data System (ADS)

    Manoshin, S. A.; Belushkin, A. V.; Kulikov, S. A.; Shabalin, E. P.; Walther, K.; Scheffzuek, C.; Zhuravlev, V. V.

    2009-09-01

    Neutron guides are widely used to transport the neutrons from the moderator to the sample. Due to the constructive features of the ring corridor of the fast pulsed reactor IBR-2, the minimal distance between the moderator and the guide entrance is around 6 m. The main goal of the paper is to optimize the neutron optical system between the moderator and the entrance of the new neutron guides. Using Monte Carlo simulations we calculate the possible best gain of the neutron flux density at the guide exit. After the described optimization process, the optimal system is obtained. The recommendations for construction of the new beam line are provided too. Similar technique and the proposed system could be easily adapted for another similar beam line at the neutron sources.

  8. A compact TOF-SANS using focusing lens and very cold neutrons

    NASA Astrophysics Data System (ADS)

    Yamada, Masako; Iwashita, Yoshihisa; Kanaya, Toshiji; Yamada, Norifumi L.; Shimizu, Hirohiko M.; Mishima, Kenji; Hino, Masahiro; Kitaguchi, Masaaki; Hirota, Katsuya; Geltenbort, Peter; Guerard, Bruno; Manzin, Giuliana; Andersen, Ken; Lal, Jyotsana; Carpenter, John M.; Bleuel, Markus; Kennedy, Shane J.

    2011-06-01

    We are developing a high-resolution small angle neutron scattering instrument for very cold neutrons (VCN). Our concept includes a magnetic lens for focusing of the beam at the detector plane. The lens consists of one permanent-magnet sextupole array rotating outside another stationary sextupole array, to focus a pulsed white beam of neutrons. Thus the instrument operates in time of flight mode. The prototype magnetic lens has a bore of 15 mm diameter and length of 66 mm, producing a magnetic field gradient oscillating from 1.5×10 4 to 5.9×10 4 T/m 2, with frequency ≤25 Hz. A torque-canceling magnet around the lens suppresses the torque of rotation from the outer array to 1/3. We have demonstrated the performance of the lens, over wavelength range from 30 to 48 Å, on the PF2-VCN beam line at the Institut Laue-Langevin, France. The focused beam image was the same size as the source, without chromatic aberration, with focal length of 1.14 m. We also studied the performance of this configuration for high-resolution SANS, in a compact geometry (just 5 m long). The measurable q range of this system was 0.009 Å -1≤ q≤0.3 Å -1 or 0.004 Å -1≤ q≤0.08 Å -1 for sample to detector distances of 100 and 465 mm, respectively. Here, we present the results of our lens characterization study along with the SANS results on a tri-block copolymer (F127 Pluronic) and on a stretched polymer blend (with the Shish-Kebab structure).

  9. 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

  10. 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. PMID:26133664

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Longitudinal-gradient magnet for time focusing of ultra-cold neutrons

    NASA Astrophysics Data System (ADS)

    Arimoto, Y.; Yoshioka, T.; Shimizu, H. M.; Mishima, K.; Ino, T.; Taketani, K.; Muto, S.; Kitaguchi, M.; Imajo, S.; Iwashita, Y.; Yamashita, S.; Kamiya, Y.; Yoshimi, A.; Asahi, K.; Shima, T.; Sakai, K.

    A gradient DC magnet is designed using 3D magnetic field analysis code. This magnet, referred to as a B0 magnet, is one of the key elements of a time-focusing device for ultra-cold neutrons (UCNs) based on a radio frequency gradient flipper - a so-called rebuncher. The magnet generates a guide and a potential field that interacts with the magnetic moment of UCNs and its main body comprises a C-shaped yoke made from iron. A field gradient is generated by a pole arrangement that includes an anisotropic inter-pole, which causes the fringe field to be uniform in the longitudinal direction even when the pole gap distance changes. The designed magnet has the following properties: (1) a maximum B-field of 10 kGauss, decreasing to 2 kGauss at a longitudinal distance of 25 cm, with a gradient of less than 400 Gauss/cm, (2) variations in the fringe field along the y direction is less than 4% over a range of - 3 cm≤ y ≤ 3 cm at any z position in the spin-flipping region. Tracking simulations show that the B0 magnet is capable of accepting UCNs in the velocity range 2.3∼3.3 m/s.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this study was to estimate the heritabilities for and genetic correlations among resistance to bacterial cold-water disease and growth traits in a population of rainbow trout. Bacterial cold-water disease, a chronic disease of rainbow trout, is caused by Flavobacterium psychrophilu...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Commissioning of the NPDGamma Detector Array: Counting Statistics in Current Mode Operation and Parity Violation in the Capture of Cold Neutrons on B4C and 27Al

    PubMed Central

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

    2005-01-01

    The NPDGamma γ-ray detector has been built to measure, with high accuracy, the size of the small parity-violating asymmetry in the angular distribution of gamma rays from the capture of polarized cold neutrons by protons. The high cold neutron flux at the Los Alamos Neutron Scattering Center (LANSCE) spallation neutron source and control of systematic errors require the use of current mode detection with vacuum photodiodes and low-noise solid-state preamplifiers. We show that the detector array operates at counting statistics and that the asymmetries due to B4C and 27Al are zero to with- in 2 × 10−6 and 7 × 10−7, respectively. Boron and aluminum are used throughout the experiment. The results presented here are preliminary. PMID:27308124

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. On the optimisation of the spectral resolution in spectrographs for cold neutrons based on refraction at grazing incidence

    NASA Astrophysics Data System (ADS)

    Jark, Werner

    2014-01-01

    Recently the wavelength dispersion of cold neutrons in the refraction process at inclined interfaces was identified as an efficient tool for neutron spectrographs, in which a larger wavelength band can be registered simultaneously. This registration mode reduces the data acquisition time significantly as no need to monochromatise the incident neutron beam by use of inefficient choppers exists. In the related studies the spectrograph performance is treated with rather complex equations. This study instead provides a theoretical treatment of the dispersion properties with simpler analytical equations, which were previously used in connection with X-rays. It can be shown, that the spectral resolution in the original spectrographs is mostly limited by the finite size of the refracted beam, which is inconveniently increasing upon refraction at grazing internal incidence onto an inclined refracting interface. The blurring of the beam size of a monochromatic beam at the detector due to the angular spread of the incident beam is mostly negligible. It is thus proposed that a significant improvement in the spectral resolution of such a spectrograph can be achieved, when the beam size at the detector is reduced by introducing focusing in the refraction process. It is shown, that the spectral resolution can then ultimately be limited by the smaller size of the blurred image caused by the angular spread of the beam. Then the improvement in this beam divergence limit can be by an order of magnitude and it is achieved by refraction upon internal incidence onto a concave interface. It is found that such a configuration will focus appropriately in a larger wavelength interval. By this means for wavelengths between 5 Å and 12 Å spectral resolutions of below 1% are feasible, which are not yet reported for such prism spectrographs.

  14. 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.

  15. 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.

  16. 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.

  17. Neutronic reactor

    DOEpatents

    Wende, Charles W. J.; Babcock, Dale F.; Menegus, Robert L.

    1983-01-01

    A nuclear reactor includes an active portion with fissionable fuel and neutron moderating material surrounded by neutron reflecting material. A control element in the active portion includes a group of movable rods constructed of neutron-absorbing material. Each rod is movable with respect to the other rods to vary the absorption of neutrons and effect control over neutron flux.

  18. Quantum diffusion of ultra-cold neutrons in a rough waveguide in a gravity field

    NASA Astrophysics Data System (ADS)

    Escobar, Mauricio

    We report the results of our study of propagation of gravitationally quantized ultracold neutrons in rough waveguides in conjunction with GRANIT experiments (ILL, Grenoble). Our theoretical study is done within the frame of the general theory of transport in systems with random rough boundaries developed by Meyerovich et al. We present a theoretical description of GRANIT experiments in the biased diffusion approximation for waveguides with one- and two-dimensional (1Dd and 2D) roughness. All system parameters collapse into a single constant (phi) which determines the depletion times for the gravitational quantum states and the exit neutron count. phi is determined by a complicated integral of the correlation function (CF) of surface roughness. For waveguides with 1D roughness most of the calculations can be performed analytically for the main common types of CF. For waveguides with 2D roughness the final calculations are mostly numerical. We also developed useful scaling equations for phi which can allow experimentalists to accommodate our results to different experimental setups. The reliable identification of the CF is always hindered by the presence of long fluctuation-driven correlation tails in finite-size samples. In order to deal with this issue, we perform numerical experiments relevant for the identification of the roughness CF. We generate surfaces with predetermined CF using rotation of uncorrelated surfaces or using Monte Carlo simulations based on the Ising model. These numerical experiments show how to circumvent the difficulties that arise in extracting the correlation properties of surface roughness using the data on the surface profile obtained in STM-like experiments. This experience helps us to analyze the new rough mirror and make theoretical predictions for ongoing GRANIT experiments. We also propose an alternative waveguide design which can improve the accuracy of experimental results.

  19. Atomic dynamics in molten AlCu alloys of different compositions and at different temperatures by cold neutron scattering

    SciTech Connect

    Dahlborg, U.; Besser, M.; Kramer, Matthew J.; Morris, J. R.; Calvo-Dahlborg, M.

    2013-12-21

    The atomic motions in molten Al1-xCux (x=0.10, 0.171 and 0.25) around the eutectic composition (x=0.171) were studied by cold neutron inelastic scattering at three different temperatures (973 K, 1173 K and 1373 K). An alloy of eutectic composition containing the 63Cu isotope was also studied. Self-diffusion coefficients for the Cu ions were determined from the width of quasielastic peaks and were found to decrease slightly with increasing Cu concentration. Longitudinal current correlation functions Jl(Q,E) exhibit at all temperatures and at all compositions a shoulder at energies below 10 meV and one main maximum at higher energies. These features can be interpreted in terms of excitations of acoustic and optic nature. The shape of Jl(Q,E) is sensitive to composition, being considerably more structured for larger Cu content. This can be coupled to the existence of a prepeak in the measured zeroth moment of dynamic scattering function indicating an increased chemical ordering with increasing Cu concentration for all temperatures. Indications for an existence of a liquid–liquid phase transition are presented.

  20. 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.

  1. Rotation of the compound nucleus 236U ∗ in the fission reaction 235U( n,f) induced by cold polarised neutrons

    NASA Astrophysics Data System (ADS)

    Goennenwein, F.; Mutterer, M.; Gagarski, A.; Guseva, I.; Petrov, G.; Sokolov, V.; Zavarukhina, T.; Gusev, Yu.; von Kalben, J.; Nesvizhevski, V.; Soldner, T.

    2007-08-01

    Surprisingly, for one of the best investigated nuclear reactions a new phenomenon was discovered. In an experiment performed at the High Flux Reactor of the Institut Laue Langevin in Grenoble, France, the reaction 235U(n , f) was studied. Fission was induced by cold polarised neutrons. Besides the two main fragments also ternary light charged particles were measured. The centres or the detector assemblies for fragments and light particles were positioned at right angles relative to each other in a plane perpendicular to the neutron beam. It is well known that the majority of ternary particles are emitted closely perpendicular to the fission axis. With the neutron spin pointing parallel or anti-parallel to the neutron beam it was observed that, upon flipping periodically the neutron spin, the distributions of angles between fragments and light particles are wobbling back and forth. The phenomenon is traced to the rotation of the scissioning nucleus while the light particles are ejected. This interpretation is corroborated by trajectory calculations for ternary α-particles being accelerated in a rotating Coulomb field provided by the two main fragments. The angle through which the fission axis and the trajectories of α-particles rotate is very small and barely exceeds 0.2°. This so far unreported feature of nuclear fission has been called the “ROT-effect”.

  2. 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.

  3. 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.

  4. 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.

  5. Fission with cold neutrons

    SciTech Connect

    Sanchez, R. G.

    2002-01-01

    As NASA continues the exploration of deep space, there is a need for safe, reliable, and long-lasting source of energy. Solar cells, which are useful at the inner solar system, cannot provide adequate power for a spacecraft once it has passed beyond Jupiter's orbit. For missions to the outer planets, NASA has relied on radioisotope thermoelectric generators (RTGs) using 238Pua s a heat source. RTGs are an excellent power conversion technology but, unfortunately, 238Pu is a potential environmental hazard. In the past, the use of 238Pu has generated much controversy and turmoil. Its use in future missions is doubtful because of environmental concerns. This paper presents calculations performed with MCNP for a power source that will take advantage of the low temperatures found in deep space.

  6. A neutron detector to monitor the intensity of transmitted neutrons for small-angle neutron scattering instruments

    NASA Astrophysics Data System (ADS)

    De Lurgio, Patrick M.; Klann, Raymond T.; Fink, Charles L.; McGregor, Douglas S.; Thiyagarajan, Pappannan; Naday, Istvan

    2003-06-01

    A semiconductor-based neutron detector was developed at Argonne National Laboratory (ANL) for use as a neutron beam monitor for small-angle neutron scattering instruments. The detector is constructed using a coating of 10B on a gallium-arsenide semiconductor detector and is mounted directly within a cylindrical (2.2 cm dia. and 4.4 cm long) enriched 10B 4C beam stop in the time-of-flight Small Angle Neutron Diffractometer (SAND) instrument at the Intense Pulsed Neutron Source (IPNS) facility at ANL. The neutron beam viewed by the SAND is from a pulsed spallation source moderated by a solid methane moderator that produces useful neutrons in the wavelength range of 0.5-14 Å. The SAND instrument uses all detected neutrons in the above wavelength range sorted by time-of-flight into 68 constant Δ T/ T=0.05 channels. This new detector continuously monitors the transmitted neutron beam through the sample during scattering measurements and takes data concurrently with the other detectors in the instrument. The 10B coating on the GaAs detector allows the detection of the cold neutron spectrum with reasonable efficiency. This paper describes the details of the detector fabrication, the beam stop monitor design, and includes a discussion of results from preliminary tests using the detector during several run cycles at the IPNS.

  7. 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.

  8. 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.

  9. 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.

  10. Neutron beam characterization at the Intense Pulsed Neutron Source.

    SciTech Connect

    Iverson, E. B.

    1998-05-18

    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 neutron scattering instruments and test facilities. The moderators at IPNS are of cryogenic methane (CH{sub 4}); one of liquid methane at 100 K, and two of solid methane at 30 K. These moderators produce intense beams of both cold and thermal neutrons. The moderators are each of a different physical configuration in order to tailor their performance for the instruments and facilities that operate on the neutron beams. As part of the ongoing operation of IPNS, as well as new enhancements to the target, moderator, and reflector systems, we have performed experiments characterizing the energy and time distribution of neutrons in the various beams. These measurements provide absolutely normalized energy spectra using foil activation techniques joined with time-of-flight measurements, and energy-dependent time distributions using a time-focused crystal analyzer. The IPNS accelerator system delivers 14 {micro}A of 450 MeV protons, in 100 ns pulses at 30 Hz, to a target composed of water-cooled depleted uranium disks. The solid methane ''H'' moderator is 100 by 100 by 45 mm in size, centerline poisoned with 0.25 mg/mm{sup 2} gadolinium, and decoupled from the graphite reflector with 0.5 mm of cadmium. The liquid methane ''F'' moderator, which is viewed from both faces, is also 100 by 100 by 45 mm in size, gadolinium poisoned 16 mm below each of the two viewed surfaces, and decoupled from the graphite reflector with cadmium. The solid methane ''C'' moderator has a re-entrant ''grooved'' geometry. The moderator is 100 by 100 by 80 mm overall, with 40 mm deep 12 mm wide horizontal grooves in the viewed surface. These grooves cover 50% of the viewed surface area. The ''C'' moderator is unpoisoned, but is decoupled from the graphite reflector with 0.5 mm of cadmium.

  11. The Jülich high-brilliance neutron source project

    NASA Astrophysics Data System (ADS)

    Rücker, U.; Cronert, T.; Voigt, J.; Dabruck, J. P.; Doege, P.-E.; Ulrich, J.; Nabbi, R.; Beßler, Y.; Butzek, M.; Büscher, M.; Lange, C.; Klaus, M.; Gutberlet, T.; Brückel, T.

    2016-01-01

    With the construction of the European Spallation Source ESS, the European neutron user community is looking forward to the brightest source worldwide. At the same time there is an ongoing concentration of research with neutrons to only a few but very powerful neutron facilities. Responding to this situation the Jülich Centre for Neutron Science has initiated a project for a compact accelerator driven high-brilliance neutron source, optimized for neutron scattering on small samples and to be realized at reasonable costs. The project deals with the optimization of potential projectiles, target and moderator concepts, versatile accelerator systems, cold sources, beam extraction systems and optimized instrumentation. A brief outline of the project, the achievements already reached, will be presented, as well as a vision for the future neutron landscape in Europe.

  12. 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)

  13. Experimental test of a newly developed single-moderator, multi-detector, directional neutron spectrometer in reference monochromatic fields from 144 keV to 16.5 MeV

    NASA Astrophysics Data System (ADS)

    Bedogni, R.; Gómez-Ros, J. M.; Pola, A.; Bortot, D.; Gentile, A.; Introini, M. V.; Buonomo, B.; Lorenzoli, M.; Mazzitelli, M.; Sacco, D.

    2015-05-01

    A new directional neutron spectrometer called CYSP (CYlindrical SPectrometer) was developed within the NESCOFI@BTF (2011-2013) collaboration. The device, composed by seven active thermal neutron detectors located along the axis of a cylindrical moderator, was designed to simultaneously respond from the thermal domain up to hundreds of MeV neutrons. The new spectrometer condenses the performance of the Bonner Sphere Spectrometer in a single moderator; thus requiring only one exposure to determine the whole spectrum. The CYSP response matrix, determined with MCNP, has been experimentally evaluated with monochromatic reference neutron fields from 144 keV to 16.5 MeV, plus a 252Cf source, available at NPL (Teddington, UK). The results of the experiment confirmed the correctness of the response matrix within an overall uncertainty of ±2.5%. The new active spectrometer CYSP offers an innovative option for real-time monitoring of directional neutron fields as those produced in neutron beam-lines.

  14. 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.

  15. 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.

  16. 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}.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Neutron Optics Optimization for the SNS EQ-SANS Diffractometer

    SciTech Connect

    Zhao, Jinkui

    2011-01-01

    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.

  3. Use of Zircaloy 4 material for the pressure vessels of hot and cold neutron sources and beam tubes for research reactors

    NASA Astrophysics Data System (ADS)

    Gutsmiedl, Erwin; Scheuer, Anton

    2002-01-01

    The material Zircaloy 4 can be used for the pressure retaining walls for the cold and hot neutron sources and beam tubes. For the research reactor FRM-II of the Technical University Munich, Germany, the material Zircaloy 4 were chosen for the vessels of the cold and hot neutron source and for the beam tube No. 6. The sheets and forgings of Zircaloy 4 were examined in the temperature range between -256°C and 250°C. The thickness of the sheets are 3, 4, 5 and 10 mm, the maximum diameter of the forgings was 560 mm. This great forging diameters are not be treated in the ASTM rule B 351 for nuclear material, so a special approval with independent experts was necessary. The requirements for the material examinations were specified in a material specification and material test sheets which based on the ASTM rules B 351 and B 352 with additional restriction and additional requirements of the basic safety concept for nuclear power plants in Germany, which was taken into consideration in the nuclear licensing procedure. Charpy-impact-test samples were carried out in the temperature range between -256°C and 150°C to get more information on the ductile behaviour of the Zircaloy 4. The results of the sheet examination confirm the requirements of the specifications, the results of the forging examination in the tangential testing direction are lower than specified and expected for the tensile strength. The axial and transverse values confirm the specification requirements. For the strength calculation of the pressure retaining wall a reduced material value for the forgings has to be taken into consideration. The material behaviour of Zircaloy 4 under irradiation up to a fluence of ∼1×10 22 n/cm 2 was investigated. The loss of ductility was determined. As additional criteria the variation of the fracture toughness was studied. Fracture mechanic calculations of the material were carried out in the licensing procedure with the focus to fulfil the leak criteria before rupture

  4. 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.

  5. Using a multi-parameter monitoring methodology to predict failures in the cryogenic plant of the cold neutron source at Australia's OPAL reactor

    NASA Astrophysics Data System (ADS)

    Lu, Weijian; Thiering, Russell

    2012-06-01

    A 5 kW Brayton-cycle helium refrigeration plant provides cooling at 20 K to the Cold Neutron Source (CNS) at Australia's OPAL Reactor. During several years of operation to the present day, the plant has experienced an unusually high number of turbine and compressor failures. The root cause for some of the failures is known, but for others remains to be determined. All of the failures were catastrophic without any prior warning from standard industrial monitoring based on singular process variables such as temperature, pressure and vibration. The failures and the down time they caused have been very costly. As the operator of the plant, we have developed a multi-parameter monitoring (MPM) methodology to track the performance of the plant. The methodology utilises indicators obtained from a combination of process variables based on their thermodynamic relations. By studying the historical trends of appropriate indicators, especially during the past failures, we have found some indicators that would be able to improve our predictive capability so that we can avoid similar failures in the future.

  6. 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.

  7. 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 ...

  8. 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)

  9. 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.

  10. 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.

  11. High energy neutron dosimeter

    DOEpatents

    Rai, K.S.F.

    1994-01-11

    A device for measuring dose equivalents in neutron radiation fields is described. The device includes nested symmetrical hemispheres (forming spheres) of different neutron moderating materials that allow the measurement of dose equivalents from 0.025 eV to past 1 GeV. The layers of moderating material surround a spherical neutron counter. The neutron counter is connected by an electrical cable to an electrical sensing means which interprets the signal from the neutron counter in the center of the moderating spheres. The spherical shape of the device allows for accurate measurement of dose equivalents regardless of its positioning. 2 figures.

  12. High energy neutron dosimeter

    DOEpatents

    Sun, Rai Ko S.F.

    1994-01-01

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

  13. 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.

  14. Characteristics of the DIN-2PI spectrometer with a neutron concentrator

    NASA Astrophysics Data System (ADS)

    Kalinin, I. V.; Morozov, V. M.; Novikov, A. G.; Puchkov, A. V.; Savostin, V. V.; Sudarev, V. V.; Bulkin, A. P.; Kalinin, S. I.; Pusenkov, V. M.; Ul'yanov, V. A.

    2014-02-01

    The basic characteristics of the upgraded DIN-2PI spectrometer are reported. Based on experimental data and numerical calculation results, it is concluded that a supermirror neutron concentrator, with which the DIN-2PI spectrometer is equipped, raises the density of the cold neutron flux at the sample almost by an order of magnitude. The use of a grooved moderator in channel no. 2 and upgrading of the core of the IBR-2M reactor increases the neutron flux density on the sample by about 40% more.

  15. Probing cold dense nuclear matter.

    PubMed

    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; Sirca, 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

    2008-06-13

    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. PMID:18511658

  16. Probing Cold Dense Nuclear Matter

    SciTech Connect

    Subedi, Ramesh; Shneor, R.; Monaghan, Peter; Anderson, Bryon; Aniol, Konrad; Annand, John; Arrington, John; Benaoum, Hachemi; Benmokhtar, Fatiha; Bertozzi, William; Boeglin, Werner; Chen, Jian-Ping; Choi, Seonho; Cisbani, Evaristo; Craver, Brandon; Frullani, Salvatore; Garibaldi, Franco; Gilad, Shalev; Gilman, Ronald; Glamazdin, Oleksandr; Hansen, Jens-Ole; Higinbotham, Douglas; Holmstrom, Timothy; Ibrahim, Hassan; Igarashi, Ryuichi; De Jager, Cornelis; Jans, Eddy; Jiang, Xiaodong; Kaufman, Lisa; Kelleher, Aidan; Kolarkar, Ameya; Kumbartzki, Gerfried; LeRose, John; Lindgren, Richard; Liyanage, Nilanga; Margaziotis, Demetrius; Markowitz, Pete; Marrone, Stefano; Mazouz, Malek; Meekins, David; Michaels, Robert; Moffit, Bryan; Perdrisat, Charles; Piasetzky, Eliazer; Potokar, Milan; Punjabi, Vina; Qiang, Yi; Reinhold, Joerg; Ron, Guy; Rosner, Guenther; Saha, Arunava; Sawatzky, Bradley; Shahinyan, Albert; Sirca, Simon; Slifer, Karl; Solvignon, Patricia; Sulkosky, Vince; Sulkosky, Vincent; Sulkosky, Vince; Sulkosky, Vincent; Urciuoli, Guido; Voutier, Eric; Watson, John; Weinstein, Lawrence; Wojtsekhowski, Bogdan; Wood, Stephen; Zheng, Xiaochao; Zhu, Lingyan

    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.

  17. 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.

  18. Total cross section of solid mesitylene, toluene and a mixture of them at thermal neutron energies

    NASA Astrophysics Data System (ADS)

    Rodríguez Palomino, L. A.; Cantargi, F.; Blostein, J. J.; Dawidowski, J.; Granada, J. R.

    2009-01-01

    The total neutron cross sections of mesitylene, toluene and a solution 3:2 by volume of mesitylene and toluene were measured at the electron LINAC based pulsed neutron source of Centro Atómico Bariloche. Measurements were performed at 180 K, 120 K and 31.6 K for mesitylene and at 120 K and 31.6 K for toluene and a solution 3:2 by volume of mesitylene and toluene. The systems are potential moderator materials to be considered in the design of a cold neutron source due to their high resistance to radiation and the richness in low-energy excitations of their frequency spectra, that lead to produce an enhanced cold neutron flux.

  19. Common cold

    MedlinePlus

    ... are the most common reason that children miss school and parents miss work. Parents often get colds ... other children. A cold can spread quickly through schools or daycares. Colds can occur at any time ...

  20. Common Cold

    MedlinePlus

    ... coughing - everyone knows the symptoms of the common cold. It is probably the most common illness. In ... people in the United States suffer 1 billion colds. You can get a cold by touching your ...

  1. 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 ...

  2. Cold intolerance

    MedlinePlus

    ... intolerance is an abnormal sensitivity to a cold environment or cold temperatures. ... can be a symptom of a problem with metabolism. Some people (often very thin women) do not tolerate cold environments because they have very little body fat and ...

  3. 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)

  4. High flux isotope reactor cold source preconceptual design study report

    SciTech Connect

    Selby, D.L.; Bucholz, J.A.; Burnette, S.E.

    1995-12-01

    In February 1995, the deputy director of Oak Ridge National Laboratory (ORNL) 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. The anticipated cold source will consist of a cryogenic LH{sub 2} moderator plug, a cryogenic pump system, a refrigerator that uses helium gas as a refrigerant, a heat exchanger to interface the refrigerant with the hydrogen loop, liquid hydrogen transfer lines, a gas handling system that includes vacuum lines, and an instrumentation and control system to provide constant system status monitoring and to maintain system stability. The scope of this project includes the development, design, safety analysis, procurement/fabrication, testing, and installation of all of the components necessary to produce a working cold source within an existing HFIR beam tube. This project will also include those activities necessary to transport the cold neutron beam to the front face of the present HFIR beam room. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and research and development (R and D), (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the preconceptual phase and establishes the concept feasibility. The information presented includes the project scope, the preliminary design requirements, the preliminary cost and schedule, the preliminary performance data, and an outline of the various plans for completing the project.

  5. Relative neutronic performance of proposed high-density dispersion fuels in water-moderated and D{sub 2}O-reflected research reactors

    SciTech Connect

    Bretscher, M.M.; Matos, J.E.; Snelgrove, J.L.

    1996-12-01

    This paper provides an overview of the neutronic performance of an idealized research reactor using several high density LEU fuels that are being developed by the RERTR program. High-density LEU dispersion fuels are needed for new and existing high-performance research reactors and to extend the lifetime of fuel elements in other research reactors. This paper discusses the anticipated neutronic behavior of proposed advanced fuels containing dispersions of U{sub 3}Si{sub 2}, UN, U{sub 2}Mo and several uranium alloys with Mo, or Zr and Nb. These advanced fuels are ranked based on the results of equilibrium depletion calculations for a simplified reactor model having a small H{sub 2}O-cooled core and a D{sub 2}O reflector. Plans have been developed to fabricate and irradiate several uranium alloy dispersion fuels in order to test their stability and compatibility with the matrix material and to establish practical loading limits.

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

    DOE PAGESBeta

    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

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

    SciTech Connect

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

    2016-01-01

    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 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.

  8. 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)

  9. 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.

  10. A neutron and synchrotron X-ray scattering study of Sr 2CuO 3+δ synthesized under moderate pressure: a new compound related to superconducting Sr 2CuO 3.1

    NASA Astrophysics Data System (ADS)

    Ami, T.; Crawford, M. K.; Harlow, R. L.; Li, Z. G.; Vogt, T.; Zhu, Q.; Cox, D. E.

    1994-12-01

    Recently, a new family of cuprate superconductors, Sr 2CuO 3+δ was stabilized at a pressure of 60 kbar 1. Here we report the synthesis at moderate pressures of 50∼3000 bar of a non-superconducting material with a closely related structure. The x-ray diffraction pattern of this lower-pressure phase, also described as Sr 2CuO 3+δ, is nearly identical with that of the superconducting phase, and TEM measurements demonstrate the presence of a 4√2 a × 4√2 a × c superstructure. The results of a high resolution synchrotron x-ray diffraction study indicate a slight orthorhombic distortion in this phase compared to the tetragonal superconducting phase. Rietveld refinement of neutron diffraction data, assuming a K 2NiF 4-type structure, reveals the presence of oxygen vacancies in the CuO 2 planes.