Overview of the Conceptual Design of the Future VENUS Neutron Imaging Beam Line at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Bilheux, Hassina; Herwig, Ken; Keener, Scott; Davis, Larry

VENUS (Versatile Neutron Imaging Beam line at the Spallation Neutron Source) will be a world-class neutron-imaging instrument that will uniquely utilize the Spallation Neutron Source (SNS) time-of-flight (TOF) capabilities to measure and characterize objects across several length scales (mm to μm). When completed, VENUS will provide academia, industry and government laboratories with the opportunity to advance scientific research in areas such as energy, materials, additive manufacturing, geosciences, transportation, engineering, plant physiology, biology, etc. It is anticipated that a good portion of the VENUS user community will have a strong engineering/industrial research focus. Installed at Beam line 10 (BL10), VENUS will be a 25-m neutron imaging facility with the capability to fully illuminate (i.e., umbra illumination) a 20 cm x 20 cm detector area. The design allows for a 28 cm x 28 cm field of view when using the penumbra to 80% of the full illumination flux. A sample position at 20 m will be implemented for magnification measurements. The optical components are comprised of a series of selected apertures, T0 and bandwidth choppers, beam scrapers, a fast shutter to limit sample activation, and flight tubes filled with Helium. Techniques such as energy selective, Bragg edge and epithermal imaging will be available at VENUS.

HYSPEC : A CRYSTAL TIME OF FLIGHT HYBRID SPECTROMETER FOR THE SPALLATION NEUTRON SOURCE.

DOE Office of Scientific and Technical Information (OSTI.GOV)

SHAPIRO,S.M.; ZALIZNYAK,I.A.

2002-12-30

This document lays out a proposal by the Instrument Development Team (IDT) composed of scientists from leading Universities and National Laboratories to design and build a conceptually new high-flux inelastic neutron spectrometer at the pulsed Spallation Neutron Source (SNS) at Oak Ridge. This instrument is intended to supply users of the SNS and scientific community, of which the IDT is an integral part, with a platform for ground-breaking investigations of the low-energy atomic-scale dynamical properties of crystalline solids. It is also planned that the proposed instrument will be equipped with a polarization analysis capability, therefore becoming the first polarized beammore » inelastic spectrometer in the SNS instrument suite, and the first successful polarized beam inelastic instrument at a pulsed spallation source worldwide. The proposed instrument is designed primarily for inelastic and elastic neutron spectroscopy of single crystals. In fact, the most informative neutron scattering studies of the dynamical properties of solids nearly always require single crystal samples, and they are almost invariably flux-limited. In addition, in measurements with polarization analysis the available flux is reduced through selection of the particular neutron polarization, which puts even more stringent limits on the feasibility of a particular experiment. To date, these investigations have mostly been carried out on crystal spectrometers at high-flux reactors, which usually employ focusing Bragg optics to concentrate the neutron beam on a typically small sample. Construction at Oak Ridge of the high-luminosity spallation neutron source, which will provide intense pulsed neutron beams with time-averaged fluxes equal to those at medium-flux reactors, opens entirely new opportunities for single crystal neutron spectroscopy. Drawing upon experience acquired during decades of studies with both crystal and time-of-flight (TOF) spectrometers, the IDT has developed a

Determination of the Secondary Neutron Flux at the Massive Natural Uranium Spallation Target

NASA Astrophysics Data System (ADS)

Zeman, M.; Adam, J.; Baldin, A. A.; Furman, W. I.; Gustov, S. A.; Katovsky, K.; Khushvaktov, J.; Mar`in, I. I.; Novotny, F.; Solnyshkin, A. A.; Tichy, P.; Tsoupko-Sitnikov, V. M.; Tyutyunnikov, S. I.; Vespalec, R.; Vrzalova, J.; Wagner, V.; Zavorka, L.

The flux of secondary neutrons generated in collisions of the 660 MeV proton beam with the massive natural uranium spallation target was investigated using a set of monoisotopic threshold activation detectors. Sandwiches made of thin high-purity Al, Co, Au, and Bi metal foils were installed in different positions across the whole spallation target. The gamma-ray activity of products of (n,xn) and other studied reactions was measured offline with germanium semiconductor detectors. Reaction yields of radionuclides with half-life exceeding 100 min and with effective neutron energy thresholds between 3.6 MeV and 186 MeV provided us with information about the spectrum of spallation neutrons in this energy region and beyond. The experimental neutron flux was determined using the measured reaction yields and cross-sections calculated with the TALYS 1.8 nuclear reaction program and INCL4-ABLA event generator of MCNP6. Neutron spectra in the region of activation sandwiches were also modeled with the radiation transport code MCNPX 2.7. Neutron flux based on excitation functions from TALYS provides a reasonable description of the neutron spectrum inside the spallation target and is in good agreement with Monte-Carlo predictions. The experimental flux that uses INCL4 cross-sections rather underestimates the modeled spectrum in the whole region of interest, but the agreement within few standard deviations was reached as well. The paper summarizes basic principles of the method for determining the spectrum of high-energy neutrons without employing the spectral adjustment routines and points out to the need for model improvements and precise cross-section measurements.

Opportunities for Neutrino Physics at the Spallation Neutron Source: A White Paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bolozdynya, A.; Cavanna, F.; Efremenko, Y.

2012-11-01

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory, Tennessee, provides an intense flux of neutrinos in the few tens-of-MeV range, with a sharply-pulsed timing structure that is beneficial for background rejection. In this document, the product of a workshop at the SNS in May 2012, we describe this free, high-quality stopped-pion neutrino source and outline various physics that could be done using it. We describe without prioritization some specific experimental configurations that could address these physics topics.

Introduction to spallation physics and spallation-target design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, G.J.; Pitcher, E.J.; Daemen, L.L.

1995-10-01

When coupled with the spallation process in appropriate target materials, high-power accelerators can be used to produce large numbers of neutrons, thus providing an alternate method to the use of nuclear reactors for this purpose. Spallation offers exciting new possibilities for generating intense neutron fluxes for a variety of applications, including: (a) spallation-neutron sources for materials science research; (b) accelerator-based production of tritium; (c) accelerator-based transmutation of waste; (d) accelerator-based destruction of plutonium; and (e) radioisotope production for medical and energy applications. Target design plays a key role in these applications, with neutron production/leakage being strongly dependent on the incidentmore » particle type and energy, and target material and geometry.« less

Initial observations of cavitation-induced erosion of liquid metal spallation target vessels at the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

McClintock, David A; Riemer, Bernie; Ferguson, Phillip D

2012-01-01

During operation of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory the mechanical properties of the AISI 316L target module are altered by high-energy neutron and proton radiation. The interior surfaces of the target vessel are also damaged by cavitation-induced erosion, which results from repetitive rapid heating of the liquid mercury by high-energy proton beam pulses. Until recently no observations of cavitation-induced erosion were possible for conditions prototypical to the SNS. Post irradiation examination (PIE) of the first and second operational SNS targets was performed to gain insight into the radiation-induced changes in mechanical properties of the 316Lmore » target material and the extent of cavitation-induced erosion to the target vessel inner surfaces. Observations of cavitation-induced erosion of the first and second operational SNS target modules are presented here, including images of the target vessel interiors and specimens removed from the target beam-entrance regions.« less

Thermal-hydraulic simulation of mercury target concepts for a pulsed spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siman-Tov, M.; Wendel, M.; Haines, J.

1996-06-01

The Oak Ridge Spallation Neutron Source (ORSNS) is a high-power, accelerator-based pulsed spallation neutron source being designed by a multi-laboratory team led by Oak Ridge National Laboratory to achieve very high fluxes of neutrons for scientific experiments. The ORSNS is projected to have a 1 MW proton beam upgradable to 5 MW. About 60% of the beam power (1-5 MW, 17-83 kJ/pulse in 0.5 microsec at 60 cps) is deposited in the liquid metal (mercury) target having the dimensions of 65x30x10 cm (about 19.5 liter). Peak steady state power density is about 150 and 785 MW/m{sup 3} for 1 MWmore » and 5 MW beam respectively, whereas peak pulsed power density is as high as 5.2 and 26.1 GW/m{sup 3}, respectively. The peak pulse temperature rise rate is 14 million C/s (for 5 MW beam) whereas the total pulse temperature rise is only 7 C. In addition to thermal shock and materials compatibility, key feasibility issues for the target are related to its thermal-hydraulic performance. This includes proper flow distribution, flow reversals, possible {open_quotes}hot spots{close_quotes} and the challenge of mitigating the effects of thermal shock through possible injection of helium bubbles throughout the mercury volume or other concepts. The general computational fluid dynamics (CFD) code CFDS-FLOW3D was used to simulate the thermal and flow distribution in three preliminary concepts of the mercury target. Very initial CFD simulation of He bubbles injection demonstrates some potential for simulating behavior of He bubbles in flowing mercury. Much study and development will be required to be able to `predict`, even in a crude way, such a complex phenomena. Future direction in both design and R&D is outlined.« less

Pairing-energy coefficients of neutron-rich fragments in spallation reactions

NASA Astrophysics Data System (ADS)

Niu, Fei; Ma, Chun-Wang

2018-02-01

The ratio of pairing-energy coefficient to temperature (a p/T) of neutron-rich fragments produced in spallation reactions has been investigated by adopting an isobaric yield ratio method deduced in the framework of a modified Fisher model. A series of spallation reactions, 0.5A and 1A GeV 208Pb + p, 1A GeV 238U + p, 0.5A GeV 136Xe + d, 0.2A, 0.5A and 1A GeV 136Xe + p, and 56Fe + p with incident energy ranging from 0.3A to 1.5A GeV, has been analysed. An obvious odd-even staggering is shown in the fragments with small neutron excess (I ≡ N-Z), and in the relatively small-A fragments which have large I. The values of a p/T for the fragments, with I from 0 to 36, have been found to be in a range from -4 to 4, and most values of a p/T fall in the range from -1 to 1. It is suggested that a small pairing-energy coefficient should be considered in predicting the cross sections of fragments in spallation reactions. It is also concluded that the method proposed in this article is not good for fragments with A/A s > 85% (where A s is the mass number of the spallation system). Supported by National Natural Science Foundation of China (U1732135), Natural Science Foundation of Henan Province (162300410179) and Henan Normal University for the Excellent Youth (154100510007)

Oak Ridge Spallation Neutron Source (ORSNS) target station design integration

DOE Office of Scientific and Technical Information (OSTI.GOV)

McManamy, T.; Booth, R.; Cleaves, J.

1996-06-01

The conceptual design for a 1- to 3-MW short pulse spallation source with a liquid mercury target has been started recently. The design tools and methods being developed to define requirements, integrate the work, and provide early cost guidance will be presented with a summary of the current target station design status. The initial design point was selected with performance and cost estimate projections by a systems code. This code was developed recently using cost estimates from the Brookhaven Pulsed Spallation Neutron Source study and experience from the Advanced Neutron Source Project`s conceptual design. It will be updated and improvedmore » as the design develops. Performance was characterized by a simplified figure of merit based on a ratio of neutron production to costs. A work breakdown structure was developed, with simplified systems diagrams used to define interfaces and system responsibilities. A risk assessment method was used to identify potential problems, to identify required research and development (R&D), and to aid contingency development. Preliminary 3-D models of the target station are being used to develop remote maintenance concepts and to estimate costs.« less

Study of neutron shielding collimators for curved beamlines at the European Spallation Source

NASA Astrophysics Data System (ADS)

Santoro, V.; DiJulio, D. D.; Ansell, S.; Cherkashyna, N.; Muhrer, G.; Bentley, P. M.

2018-06-01

The European Spallation Source is being constructed in Lund, Sweden and is planned to be the world’s brightest pulsed spallation neutron source for cold and thermal neutron beams (≤ 1 eV). The facility uses a 2 GeV proton beam to produce neutrons from a tungsten target. The neutrons are then moderated in a moderator assembly consisting of both liquid hydrogen and water compartments. Surrounding the moderator are 22 beamports, which view the moderator’s outside surfaces. The beamports are connected to long neutron guides that transport the moderated neutrons to the sample position via reflections. As well as the desired moderated neutrons, fast neutrons coming directly from the target can find their way down the beamlines. These can create unwanted sources of background for the instruments. To mitigate such a kind of background, several instruments will use curved guides to lose direct line-of-sight (LoS) to the moderator and the target. In addition instruments can also use shielding collimators to reduce the amount of fast neutrons further traveling down the guide due to albedo reflections or streaming. Several different materials have been proposed for this purpose. We present the results of a study of different options for collimators and identify the optimal choices that balance cost, background and activation levels.

Principles for timing at spallation neutron sources based on developments at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, R. O.; Merl, R. B.; Rose, C. R.

2001-01-01

Due to AC-power-grid frequency fluctuations, the designers for accelerator-based spallation-neutron facilities have worked to optimize the conflicting demands of accelerator and neutron chopper performance. For the first time, we are able to quantitatively access the tradeoffs between these two constraints and design or upgrade a facility to optimize total system performance using powerful new simulation techniques. We have modeled timing systems that integrate chopper controllers and chopper hardware and built new systems. Thus, at LANSCE, we now operate multiple chopper systems and the accelerator as simple slaves to a single master-timing-reference generator. Based on this experience we recommend that spallationmore » neutron sources adhere to three principles. First, timing for pulsed sources should be planned starting with extraction at a fixed phase and working backwards toward the leading edge of the beam pulse. Second, accelerator triggers and storage ring extraction commands from neutron choppers offer only marginal benefits to accelerator-based spallation sources. Third, the storage-ring RF should be phase synchronized with neutron choppers to provide extraction without the one orbit timing uncertainty.« less

The National Spallation Neutron Source Target Station.

NASA Astrophysics Data System (ADS)

Gabriel, T. A.

1997-05-01

The technologies that are being utilized to design and build a state-of-the-art high powered (>= 1 MW), short pulsed (<= 1 μsec), and reliable spallation neutron source target station are discussed. The protons which directly and indirectly produce the neutrons will be obtained from a 1 GeV proton accelerator composed of an ion gun, rfq, linac, and storage ring. Many scientific and technical disciplines are required to produce a successful target station. These disciplines include engineering, remote handling, neutronics, materials, thermal hydraulics, shock analysis, etc. In the areas of engineering and remote handling special emphasis is being given to rapid and efficient assembly and disassembly of critical parts of the target station. In the neutronics area, emphasis is being given to neutron yield and pulse optimization from the moderators, and heating and activation rates throughout the station. Development of structural materials to withstand aggressive radiation environments and that are compatible with other materials is also an important area. Thermal hydraulics and shock analysis are being closely studied since large amounts of energy are being deposited in small volumes in relatively short time periods (< 1 μsec). These areas will be expanded upon in the paper.

Spallation neutron production and the current intra-nuclear cascade and transport codes

NASA Astrophysics Data System (ADS)

Filges, D.; Goldenbaum, F.; Enke, M.; Galin, J.; Herbach, C.-M.; Hilscher, D.; Jahnke, U.; Letourneau, A.; Lott, B.; Neef, R.-D.; Nünighoff, K.; Paul, N.; Péghaire, A.; Pienkowski, L.; Schaal, H.; Schröder, U.; Sterzenbach, G.; Tietze, A.; Tishchenko, V.; Toke, J.; Wohlmuther, M.

A recent renascent interest in energetic proton-induced production of neutrons originates largely from the inception of projects for target stations of intense spallation neutron sources, like the planned European Spallation Source (ESS), accelerator-driven nuclear reactors, nuclear waste transmutation, and also from the application for radioactive beams. In the framework of such a neutron production, of major importance is the search for ways for the most efficient conversion of the primary beam energy into neutron production. Although the issue has been quite successfully addressed experimentally by varying the incident proton energy for various target materials and by covering a huge collection of different target geometries --providing an exhaustive matrix of benchmark data-- the ultimate challenge is to increase the predictive power of transport codes currently on the market. To scrutinize these codes, calculations of reaction cross-sections, hadronic interaction lengths, average neutron multiplicities, neutron multiplicity and energy distributions, and the development of hadronic showers are confronted with recent experimental data of the NESSI collaboration. Program packages like HERMES, LCS or MCNPX master the prevision of reaction cross-sections, hadronic interaction lengths, averaged neutron multiplicities and neutron multiplicity distributions in thick and thin targets for a wide spectrum of incident proton energies, geometrical shapes and materials of the target generally within less than 10% deviation, while production cross-section measurements for light charged particles on thin targets point out that appreciable distinctions exist within these models.

rf improvements for Spallation Neutron Source H- ion sourcea)

NASA Astrophysics Data System (ADS)

Kang, Y. W.; Fuja, R.; Goulding, R. H.; Hardek, T.; Lee, S.-W.; McCarthy, M. P.; Piller, M. C.; Shin, K.; Stockli, M. P.; Welton, R. F.

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering ˜38 mA H- beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

rf improvements for Spallation Neutron Source H- ion source.

PubMed

Kang, Y W; Fuja, R; Goulding, R H; Hardek, T; Lee, S-W; McCarthy, M P; Piller, M C; Shin, K; Stockli, M P; Welton, R F

2010-02-01

The Spallation Neutron Source at Oak Ridge National Laboratory is ramping up the accelerated proton beam power to 1.4 MW and just reached 1 MW. The rf-driven multicusp ion source that originates from the Lawrence Berkeley National Laboratory has been delivering approximately 38 mA H(-) beam in the linac at 60 Hz, 0.9 ms. To improve availability, a rf-driven external antenna multicusp ion source with a water-cooled ceramic aluminum nitride (AlN) plasma chamber is developed. Computer modeling and simulations have been made to analyze and optimize the rf performance of the new ion source. Operational statistics and test runs with up to 56 mA medium energy beam transport beam current identify the 2 MHz rf system as a limiting factor in the system availability and beam production. Plasma ignition system is under development by using a separate 13 MHz system. To improve the availability of the rf power system with easier maintenance, we tested a 70 kV isolation transformer for the 80 kW, 6% duty cycle 2 MHz amplifier to power the ion source from a grounded solid-state amplifier.

Universal odd-even staggering in isotopic fragmentation and spallation cross sections of neutron-rich fragments

NASA Astrophysics Data System (ADS)

Mei, B.; Tu, X. L.; Wang, M.

2018-04-01

An evident odd-even staggering (OES) in fragment cross sections has been experimentally observed in many fragmentation and spallation reactions. However, quantitative comparisons of this OES effect in different reaction systems are still scarce for neutron-rich nuclei near the neutron drip line. By employing a third-order difference formula, the magnitudes of this OES in extensive experimental cross sections are systematically investigated for many neutron-rich nuclei with (N -Z ) from 1 to 23 over a broad range of atomic numbers (Z ≈3 -50 ). A comparison of these magnitude values extracted from fragment cross sections measured in different fragmentation and spallation reactions with a large variety of projectile-target combinations over a wide energy range reveals that the OES magnitude is almost independent of the projectile-target combinations and the projectile energy. The weighted average of these OES magnitudes derived from cross sections accurately measured in different reaction systems is adopted as the evaluation value of the OES magnitude. These evaluated OES magnitudes are recommended to be used in fragmentation and spallation models to improve their predictions for fragment cross sections.

Design specification for the European Spallation Source neutron generating target element

NASA Astrophysics Data System (ADS)

Aguilar, A.; Sordo, F.; Mora, T.; Mena, L.; Mancisidor, M.; Aguilar, J.; Bakedano, G.; Herranz, I.; Luna, P.; Magan, M.; Vivanco, R.; Jimenez-Villacorta, F.; Sjogreen, K.; Oden, U.; Perlado, J. M.; Martinez, J. L.; Bermejo, F. J.

2017-06-01

The paper addresses some of the most relevant issues concerning the thermal hydraulics and radiation damage of the neutron generation target to be built at the European Spallation Source as recently approved after a critical design review. The target unit consists of a set of Tungsten blocks placed inside a wheel of 2.5 m diameter which rotates at some 0.5 Hz in order to distribute the heat generated from incoming protons which reach the target in the radial direction. The spallation material elements are composed of an array of Tungsten pieces which rest on a rotating steel support (the cassette) and are distributed in a cross-flow configuration. The thermal, mechanical and radiation effects resulting from the impact of a 2 GeV proton pulse are analysed in detail as well as an evaluation of the inventory of spallation products. The current design is found to conform to specifications and found to be robust enough to deal with several accident scenarios.

Mercury Cavitation Phenomenon in Pulsed Spallation Neutron Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Futakawa, Masatoshi; Naoe, Takashi; Kawai, Masayoshi

2008-06-24

Innovative researches will be performed at Materials and Life Science Experimental Facility in J-PARC, in which a mercury target system will be installed as MW-class pulse spallation neutron sources. Proton beams will be injected into mercury target to induce the spallation reaction. At the moment the intense proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. Localized impacts by micro-jets and/or shock waves which are caused by cavitation bubble collapse imposemore » pitting damage on the vessel wall. The pitting damage which degrades the structural integrity of target vessels is a crucial issue for high power mercury targets. Micro-gas-bubbles injection into mercury may be useful to mitigate the pressure wave and the pitting damage. The visualization of cavitation-bubble and gas-bubble collapse behaviors was carried out by using a high-speed video camera. The differences between them are recognized.« less

Core Vessel Insert Handling Robot for the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graves, Van B; Dayton, Michael J

2011-01-01

The Spallation Neutron Source provides the world's most intense pulsed neutron beams for scientific research and industrial development. Its eighteen neutron beam lines will eventually support up to twenty-four simultaneous experiments. Each beam line consists of various optical components which guide the neutrons to a particular instrument. The optical components nearest the neutron moderators are the core vessel inserts. Located approximately 9 m below the high bay floor, these inserts are bolted to the core vessel chamber and are part of the vacuum boundary. They are in a highly radioactive environment and must periodically be replaced. During initial SNS construction,more » four of the beam lines received Core Vessel Insert plugs rather than functional inserts. Remote replacement of the first Core Vessel Insert plug was recently completed using several pieces of custom-designed tooling, including a highly complicated Core Vessel Insert Robot. The design of this tool are discussed.« less

In situ polarized 3He system for the Magnetism Reflectometer at the Spallation Neutron Source.

PubMed

Tong, X; Jiang, C Y; Lauter, V; Ambaye, H; Brown, D; Crow, L; Gentile, T R; Goyette, R; Lee, W T; Parizzi, A; Robertson, J L

2012-07-01

We report on the in situ polarized (3)He neutron polarization analyzer developed for the time-of-flight Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Using the spin exchange optical pumping method, we achieved a (3)He polarization of 76% ± 1% and maintained it for the entire three-day duration of the test experiment. Based on transmission measurements with unpolarized neutrons, we show that the average analyzing efficiency of the (3)He system is 98% for the neutron wavelength band of 2-5 Å. Using a highly polarized incident neutron beam produced by a supermirror bender polarizer, we obtained a flipping ratio of >100 with a transmission of 25% for polarized neutrons, averaged over the wavelength band of 2-5 Å. After the cell was depolarized for transmission measurements, it was reproducibly polarized and this performance was maintained for three weeks. A high quality polarization analysis experiment was performed on a reference sample of Fe/Cr multilayer with strong spin-flip off-specular scattering. Using a combination of the position sensitive detector, time-of-flight method, and the excellent parameters of the (3)He cell, the polarization analysis of the two-dimensional maps of reflected, refracted, and off-specular scattered intensity above and below the horizon were obtained, simultaneously.

Characterization of γ-ray background at IMAT beamline of ISIS Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Festa, G.; Andreani, C.; Arcidiacono, L.; Burca, G.; Kockelmann, W.; Minniti, T.; Senesi, R.

2017-08-01

The environmental γ -ray background on the IMAT beamline at ISIS Spallation Neutron Source, Target Station 2, is characterized via γ spectroscopy. The measurements include gamma exposure at the imaging detector position, along with the gamma background inside the beamline. Present results are discussed and compared with previous measurements recorded at INES and VESUVIO beamlines operating at Target Station 1. They provide new outcome for expanding and optimizing the PGAA experimental capability at the ISIS neutron source for the investigation of materials, engineering components and cultural heritage objects at the ISIS neutron source.

Fast neutron irradiation tests of flash memories used in space environment at the ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

Andreani, C.; Senesi, R.; Paccagnella, A.; Bagatin, M.; Gerardin, S.; Cazzaniga, C.; Frost, C. D.; Picozza, P.; Gorini, G.; Mancini, R.; Sarno, M.

2018-02-01

This paper presents a neutron accelerated study of soft errors in advanced electronic devices used in space missions, i.e. Flash memories performed at the ChipIr and VESUVIO beam lines at the ISIS spallation neutron source. The two neutron beam lines are set up to mimic the space environment spectra and allow neutron irradiation tests on Flash memories in the neutron energy range above 10 MeV and up to 800 MeV. The ISIS neutron energy spectrum is similar to the one occurring in the atmospheric as well as in space and planetary environments, with intensity enhancements varying in the range 108- 10 9 and 106- 10 7 respectively. Such conditions are suitable for the characterization of the atmospheric, space and planetary neutron radiation environments, and are directly applicable for accelerated tests of electronic components as demonstrated here in benchmark measurements performed on flash memories.

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

NASA Astrophysics Data System (ADS)

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

2015-04-01

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

Overview of the Neutron Radiography and Computed Tomography at the Oak Ridge National Laboratory and Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilheux, Hassina Z; Bilheux, Jean-Christophe; Tremsin, Anton S

2015-01-01

The Oak Ridge National Laboratory (ORNL) Neutron Sciences Directorate (NScD) has installed a neutron imaging (NI) beam line at the High Flux Isotope Reactor (HFIR) cold guide hall. The CG-1D beam line produces cold neutrons for a broad range of user research spanning from engineering to material research, additive manufacturing, vehicle technologies, archaeology, biology, and plant physiology. Recent efforts have focused on increasing flux and spatial resolution. A series of selected engineering applications is presented here. Historically and for more than four decades, neutron imaging (NI) facilities have been installed exclusively at continuous (i.e. reactor-based) neutron sources rather than atmore » pulsed sources. This is mainly due to (1) the limited number of accelerator-based facilities and therefore the fierce competition for beam lines with neutron scattering instruments, (2) the limited flux available at accelerator-based neutron sources and finally, (3) the lack of high efficiency imaging detector technology capable of time-stamping pulsed neutrons with sufficient time resolution. Recently completed high flux pulsed proton-driven neutron sources such as the ORNL Spallation Neutron Source (SNS) at ORNL and the Japanese Spallation Neutron Source (JSNS) of the Japan Proton Accelerator Research Complex (J-PARC) in Japan produce high neutron fluxes that offer new and unique opportunities for NI techniques. Pulsed-based neutron imaging facilities RADEN and IMAT are currently being built at J-PARC and the Rutherford National Laboratory in the U.K., respectively. ORNL is building a pulsed neutron imaging beam line called VENUS to respond to the U.S. based scientific community. A team composed of engineers, scientists and designers has developed a conceptual design of the future VENUS imaging instrument at the SNS.« less

Spallation radiation effects in materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mansur, L.K.; Farrell, K.; Wechsler, M.S.

1996-06-01

Spallation refers to the process whereby particles (chiefly neutrons) are ejected from nuclei upon bombardment by high-energy protons. Spallation neutron sources (SNS`s) use these neutrons for neutron scattering and diffraction research, and SNS`s are proposed as the basis for systems for tritium production and transmutation of nuclear waste. Materials in SNS`s are exposed to the incident proton beam (energies typically about 1000 MeV) and to the spallation neutrons (spectrum of energies extending up to about 1000 MeV). By contrast the fission neutrons in nuclear reactors have an average energy of only about 2 MeV, and the neutrons in fusion reactorsmore » would have energies below about 14 MeV. Furthermore, the protons and neutrons in SNS`s for scattering and diffraction research are pulsed at frequencies of about 10 to 60 Hz, from which significant changes in the kinetics of point and extended defects may be expected. In addition, much higher transmutation rates occur in SNS-irradiated materials, On the whole, then, significant differences in microstructural development and macroscopic properties may result upon exposure in SNS systems, as compared with fission and fusion irradiations. In a more general sense, subjecting materials to new radiation environments has almost routinely led to new discoveries. To the extent that data are avaiable, however, the spallation environment appears to increase the degree of damage without introducing totally new effects. The first part of this presentation is an overview of radiation effects in materials, outlining essential concepts and property changes and their physical bases. This background is followed by a description of SNS irradiation environments and the effects on materials of exposure to these environments. A special discussion is given of the selection of target (e.g., liquid mercury), container (e.g., austenitic stainless steel or ferritic/martensitic steel), and structural materials in SNS systems.« less

Spallation Neutron Source Second Target Station Integrated Systems Update

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ankner, John Francis; An, Ke; Blokland, Willem

The Spallation Neutron Source (SNS) was designed from the beginning to accommodate both an accelerator upgrade to increase the proton power and a second target station (STS). Four workshops were organized in 2013 and 2014 to identify key science areas and challenges where neutrons will play a vital role [1-4]. Participants concluded that the addition of STS to the existing ORNL neutron sources was needed to complement the strengths of High Flux Isotope Reactor (HFIR) and the SNS first target station (FTS). To address the capability gaps identified in the workshops, a study was undertaken to identify instrument concepts thatmore » could provide the required new science capabilities. The study outlined 22 instrument concepts and presented an initial science case for STS [5]. These instrument concepts formed the basis of a planning suite of instruments whose requirements determined an initial site layout and moderator selection. An STS Technical Design Report (TDR) documented the STS concept based on those choices [6]. Since issue of the TDR, the STS concept has significantly matured as described in this document.« less

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

DOE PAGES

Gallmeier, F. X.; Lu, W.; Riemer, B. W.; ...

2016-06-14

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

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.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallmeier, F. X.; Lu, W.; Riemer, B. W.

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

Spin exchange optical pumping based polarized 3He filling station for the Hybrid Spectrometer at the Spallation Neutron Source.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Culbertson, H; Graves-Brook, M K; Hagen, M E; Kadron, B; Lee, W T; Robertson, J L; Winn, B

2013-06-01

The Hybrid Spectrometer (HYSPEC) is a new direct geometry spectrometer at the Spallation Neutron Source at the Oak Ridge National Laboratory. This instrument is equipped with polarization analysis capability with 60° horizontal and 15° vertical detector coverages. In order to provide wide angle polarization analysis for this instrument, we have designed and built a novel polarized (3)He filling station based on the spin exchange optical pumping method. It is designed to supply polarized (3)He gas to HYSPEC as a neutron polarization analyzer. In addition, the station can optimize the (3)He pressure with respect to the scattered neutron energies. The depolarized (3)He gas in the analyzer can be transferred back to the station to be repolarized. We have constructed the prototype filling station. Preliminary tests have been carried out demonstrating the feasibility of the filling station. Here, we report on the design, construction, and the preliminary results of the prototype filling station.

General-purpose readout electronics for white neutron source at China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Wang, Q.; Cao, P.; Qi, X.; Yu, T.; Ji, X.; Xie, L.; An, Q.

2018-01-01

The under-construction White Neutron Source (WNS) at China Spallation Neutron Source is a facility for accurate measurements of neutron-induced cross section. Seven spectrometers are planned at WNS. As the physical objectives of each spectrometer are different, the requirements for readout electronics are not the same. In order to simplify the development of the readout electronics, this paper presents a general method for detector signal readout. This method has advantages of expansibility and flexibility, which makes it adaptable to most detectors at WNS. In the WNS general-purpose readout electronics, signals from any kinds of detectors are conditioned by a dedicated signal conditioning module corresponding to this detector, and then digitized by a common waveform digitizer with high speed and high precision (1 GSPS at 12-bit) to obtain the full waveform data. The waveform digitizer uses a field programmable gate array chip to process the data stream and trigger information in real time. PXI Express platform is used to support the functionalities of data readout, clock distribution, and trigger information exchange between digitizers and trigger modules. Test results show that the performance of the WNS general-purpose readout electronics can meet the requirements of the WNS spectrometers.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gallmeier, F. X., E-mail: gallmeierfz@ornl.gov; Lu, W.; Riemer, B. W.

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 comparedmore » 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{sup 2} to 20 × 20 mm{sup 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.« less

Neutron Imaging at the Oak Ridge National Laboratory: Application to Biological Research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bilheux, Hassina Z; Cekanova, Maria; Bilheux, Jean-Christophe

2014-01-01

The Oak Ridge National Laboratory Neutron Sciences Directorate (NScD) has recently installed a neutron imaging beamline at the High Flux Isotope Reactor (HFIR) cold guide hall. The CG-1D beamline supports a broad range of user research spanning from engineering to material research, energy storage, additive manufacturing, vehicle technologies, archaeology, biology, and plant physiology. The beamline performance (spatial resolution, field of view, etc.) and its utilization for biological research are presented. The NScD is also considering a proposal to build the VENUS imaging beamline (beam port 10) at the Spallation Neutron Source (SNS). Unlike CG-1D which provides cold neutrons, VENUS willmore » offer a broad range of neutron wavelengths, from epithermal to cold, and enhanced contrast mechanisms. This new capability will also enable the imaging of thicker biological samples than is currently available at CG-1D. A brief overview of the VENUS capability for biological research is discussed.« less

New precision measurements of free neutron beta decay with cold neutrons

DOE PAGES

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

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.

Probing light sterile neutrino signatures at reactor and Spallation Neutron Source neutrino experiments

NASA Astrophysics Data System (ADS)

Kosmas, T. S.; Papoulias, D. K.; Tórtola, M.; Valle, J. W. F.

2017-09-01

We investigate the impact of a fourth sterile neutrino at reactor and Spallation Neutron Source neutrino detectors. Specifically, we explore the discovery potential of the TEXONO and COHERENT experiments to subleading sterile neutrino effects through the measurement of the coherent elastic neutrino-nucleus scattering event rate. Our dedicated χ2-sensitivity analysis employs realistic nuclear structure calculations adequate for high purity sub-keV threshold Germanium detectors.

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

DOE PAGES

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.; ...

2018-02-21

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

The suite of small-angle neutron scattering instruments at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heller, William T.; Cuneo, Matthew J.; Debeer-Schmitt, Lisa M.

Oak Ridge National Laboratory is home to the High Flux Isotope Reactor (HFIR), a high-flux research reactor, and the Spallation Neutron Source (SNS), the world's most intense source of pulsed neutron beams. The unique co-localization of these two sources provided an opportunity to develop a suite of complementary small-angle neutron scattering instruments for studies of large-scale structures: the GP-SANS and Bio-SANS instruments at the HFIR and the EQ-SANS and TOF-USANS instruments at the SNS. This article provides an overview of the capabilities of the suite of instruments, with specific emphasis on how they complement each other. As a result, amore » description of the plans for future developments including greater integration of the suite into a single point of entry for neutron scattering studies of large-scale structures is also provided.« less

Study on induced radioactivity of China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Wu, Qing-Biao; Wang, Qing-Bin; Wu, Jing-Min; Ma, Zhong-Jian

2011-06-01

China Spallation Neutron Source (CSNS) is the first High Energy Intense Proton Accelerator planned to be constructed in China during the State Eleventh Five-Year Plan period, whose induced radioactivity is very important for occupational disease hazard assessment and environmental impact assessment. Adopting the FLUKA code, the authors have constructed a cylinder-tunnel geometric model and a line-source sampling physical model, deduced proper formulas to calculate air activation, and analyzed various issues with regard to the activation of different tunnel parts. The results show that the environmental impact resulting from induced activation is negligible, whereas the residual radiation in the tunnels has a great influence on maintenance personnel, so strict measures should be adopted.

Calculation Package: Derivation of Facility-Specific Derived Air Concentration (DAC) Values in Support of Spallation Neutron Source Operations

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLaughlin, David A

Derived air concentration (DAC) values for 175 radionuclides* produced at the Oak Ridge National Laboratory (ORNL) Spallation Neutron Source (SNS), but not listed in Appendix A of 10 CFR 835 (01/01/2009 version), are presented. The proposed DAC values, ranging between 1 E-07 {micro}Ci/mL and 2 E-03 {micro}Ci/mL, were calculated in accordance with the recommendations of the International Commission on Radiological Protection (ICRP), and are intended to support an exemption request seeking regulatory relief from the 10 CFR 835, Appendix A, requirement to apply restrictive DACs of 2E-13 {micro}Ci/mL and 4E-11 {micro}Ci/mL and for non-listed alpha and non-alpha-emitting radionuclides, respectively.

International workshop on cold neutron sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 ofmore » 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.« less

The European scene regarding spallation neutron sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, G.S.

1996-06-01

In Europe, a short pulse spallation neutron source, ISIS, has been operating for over 10 years, working its way up to a beam power level of 200 kW. A continuous source, SINQ, designed for a beam power of up to 1 MW, is scheduled to start operating at the end of 1996, and a detailed feasibility study has been completed for a 410 kW short pulse source, AUSTRON. Each of these sources seems to have settled for a target concept which is at or near the limits of its feasibility: The ISIS depleted uranium plate targets, heavy water cooled andmore » Zircaloy clad, have so far not shown satisfactory service time and operation is likely to continue with a Ta-plate target, which, in the past has been used successfully for the equivalent of one full-beam-year before it was taken out of service due to degrading thermal properties. SINQ will initially use a rod target, made of Zircaloy only, but plans exist to move on to clad lead rods as quickly as possible. Apart from the not yet explored effect of hydrogen and helium production, there are also concerns about the generation of 7-Be in the cooling water from the spallation of oxygen, which might result in undesirably high radioactivity in the cooling plant room. A Liquid metal target, also under investigation for SINQ, would not only reduce this problem to a level of about 10 %, but would also minimize the risk of radiolytic corrosion in the beam interaction zone. Base on similar arguments, AUSTRON has been designed for edge cooled targets, but thermal and stress analyses show, that this concept is not feasible at higher power levels.« less

New generation high performance in situ polarized 3He system for time-of-flight beam at spallation sources.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Glavic, A; Ambaye, H; Goyette, R; Hoffmann, M; Parizzi, A A; Robertson, L; Lauter, V

2017-02-01

Modern spallation neutron sources generate high intensity neutron beams with a broad wavelength band applied to exploring new nano- and meso-scale materials from a few atomic monolayers thick to complicated prototype device-like systems with multiple buried interfaces. The availability of high performance neutron polarizers and analyzers in neutron scattering experiments is vital for understanding magnetism in systems with novel functionalities. We report the development of a new generation of the in situ polarized 3 He neutron polarization analyzer for the Magnetism Reflectometer at the Spallation Neutron Source at Oak Ridge National Laboratory. With a new optical layout and laser system, the 3 He polarization reached and maintained 84% as compared to 76% in the first-generation system. The polarization improvement allows achieving the transmission function varying from 50% to 15% for the polarized neutron beam with the wavelength band of 2-9 Angstroms. This achievement brings a new class of experiments with optimal performance in sensitivity to very small magnetic moments in nano systems and opens up the horizon for its applications.

Decommissioning and PIE of the MEGAPIE spallation target

DOE Office of Scientific and Technical Information (OSTI.GOV)

Latge, C.; Henry, J.; Wohlmuther, M.

2013-07-01

A key experiment in the Accelerated Driven Systems roadmap, the MEGAwatt PIlot Experiment (MEGAPIE) (1 MW) was initiated in 1999 in order to design and build a liquid lead-bismuth spallation target, then to operate it into the Swiss spallation neutron facility SINQ at Paul Scherrer Institute. The target has been designed, manufactured, and tested during integral tests, before irradiation carried out end of 2006. During irradiation, neutron and thermo hydraulic measurements were performed allowing deep interpretation of the experiment and validation of the models used during design phase. The decommissioning, Post Irradiation Examinations and waste management phases were defined properly.more » The phases dedicated to cutting, sampling, cleaning, waste management, samples preparation and shipping to various laboratories were performed by PSI teams: all these phases constitute a huge work, which allows now to perform post-irradiation examination (PIE) of structural material, irradiated in relevant conditions. Preliminary results are presented in the paper, they concern chemical characterization. The following radio-nuclides have been identified by γ-spectrometry: {sup 60}Co, {sup 101}Rh, {sup 102}Rh, {sup 108m}Ag, {sup 110m}Ag, {sup 133}Ba, {sup 172}Hf/Lu, {sup 173}Lu, {sup 194}Hg/Au, {sup 195}Au, {sup 207}Bi. For some of these nuclides the activities can be easily evaluated from γ-spectrometry results ({sup 207}Bi, {sup 194}Hg/Au), while other nuclides can only be determined after chemical separations ({sup 108m}Ag, {sup 110m}Ag, {sup 195}Au, {sup 129}I, {sup 36}Cl and α-emitting {sup 208-210}Po). The concentration of {sup 129}I is lower than expected. The chemical analysis already performed on spallation and corrosion products in the lead-bismuth eutectic (LBE) are very relevant for further applications of LBE as a spallation media and more generally as a coolant.« less

Detection of spallation neutrons and protons using the (nat)Cd activation technique in transmutation experiments at Dubna.

PubMed

Manolopoulou, M; Stoulos, S; Fragopoulou, M; Brandt, R; Westmeier, W; Krivopustov, M; Sosnin, A; Zamani, M

2006-07-01

Various spallation sources have been used to transmute long-lived radioactive waste, mostly making use of the wide energy neutron fluence. In addition to neutrons, a large number of protons and gamma rays are also emitted from these sources. In this paper (nat)Cd is proved to be a useful activation detector for determining both thermal-epithermal neutron as well as secondary proton fluences. The fluences measured with (nat)Cd compared with other experimental data and calculations of DCM-DEM code were found to be in reasonable agreement. An accumulation of thermal-epithermal neutrons around the center of the target (i.e. after approx. 10 cm) and of secondary protons towards the end of the target is observed.

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

DOE PAGES

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

2016-09-13

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

Ductility recovery in structural materials for spallation targets by post-irradiation annealing

NASA Astrophysics Data System (ADS)

Chen, J.; Jung, P.; Rödig, M.; Ullmaier, H.; Bauer, G. S.

2005-08-01

Low temperature irradiation embrittlement is one of the major criteria to determine the lifetime of spallation targets. Embrittlement is especially high at low service temperatures, e.g. 250 °C in liquid-mercury sources. It was the aim of the present study to investigate the effect of post-irradiation annealing on the mechanical properties of irradiated structural materials. The specimens used were obtained from spent target components of operating spallation facilities (Los Alamos Neutron Science Center, LANSCE, and the Spallation Neutron Source at Rutherford-Appleton Laboratory, ISIS). The investigated materials include a nickel-based alloy (IN718), an austenitic stainless steel (AISI 304L), a martensitic stainless steel (DIN 1.4926) and a refractory metal (Ta) which experienced 800 MeV proton irradiation to fluences of several 10 25 p/m 2. The specimens were annealed from 300 °C to 700 °C for 1 to 10 h, respectively, and their mechanical property changes were subsequently investigated at room temperature and 250 °C by tensile testing and fracture surface analysis conducted by scanning electron microscopy (SEM). The results showed that the ductility recovered to a large degree in 304L and DIN 1.4926 materials while their strength remained almost unchanged. Especially for DIN 1.4926, the ductility recovery is remarkable already at 400 °C. Together with its favorable thermo-mechanical properties, this makes martensitic steel a candidate for structural materials of spallation targets.

Observations of Space Charge effects in the Spallation Neutron Source Accumulator Ring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Potts III, Robert E; Cousineau, Sarah M; Holmes, Jeffrey A

2012-01-01

The Spallation Neutron Source accumulator ring was designed to allow independent control of the transverse beam distribution in each plane. However, at high beam intensities, nonlinear space charge forces can strongly influence the final beam distribution and compromise our ability to independently control the transverse distributions. In this study we investigate the evolution of the beam at intensities of up to ~8x10^13 ppp through both simulation and experiment. Specifically, we analyze the evolution of the beam distribution for beams with different transverse aspect ratios and tune splits. We present preliminary results of simulations of our experiments.

HPC simulations of grain-scale spallation to improve thermal spallation drilling

NASA Astrophysics Data System (ADS)

Walsh, S. D.; Lomov, I.; Wideman, T. W.; Potter, J.

2012-12-01

Thermal spallation drilling and related hard-rock hole opening techniques are transformative technologies with the potential to dramatically reduce the costs associated with EGS well drilling and improve the productivity of new and existing wells. In contrast to conventional drilling methods that employ mechanical means to penetrate rock, thermal spallation methods fragment rock into small pieces ("spalls") without contact via the rapid transmission of heat to the rock surface. State-of-the-art constitutive models of thermal spallation employ Weibull statistical failure theory to represent the relationship between rock heterogeneity and its propensity to produce spalls when heat is applied to the rock surface. These models have been successfully used to predict such factors as penetration rate, spall-size distribution and borehole radius from drilling jet velocity and applied heat flux. A properly calibrated Weibull model would permit design optimization of thermal spallation drilling under geothermal field conditions. However, although useful for predicting system response in a given context, Weibull models are by their nature empirically derived. In the past, the parameters used in these models were carefully determined from laboratory tests, and thus model applicability was limited by experimental scope. This becomes problematic, for example, if simulating spall production at depths relevant for geothermal energy production, or modeling thermal spallation drilling in new rock types. Nevertheless, with sufficient computational resources, Weibull models could be validated in the absence of experimental data by explicit small-scale simulations that fully resolve rock grains. This presentation will discuss how high-fidelity simulations can be used to inform Weibull models of thermal spallation, and what these simulations reveal about the processes driving spallation at the grain-scale - in particular, the role that inter-grain boundaries and micro-pores play in the

Design progress of cryogenic hydrogen system for China Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, G. P.; Zhang, Y.; Xiao, J.

2014-01-29

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

Polarized neutron scattering on HYSPEC: the HYbrid SPECtrometer at SNS

DOE PAGES

Zaliznyak, Igor A.; Savici, Andrei T.; Ovidiu Garlea, V.; ...

2017-06-20

Here, we describe some of the first polarized neutron scattering measurements performed at HYSPEC [1-4] spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. Furthermore, we discuss details of the instrument setup and the experimental procedures in the mode with full polarization analysis. Examples of polarized neutron diffraction and polarized inelastic neutron data obtained on single crystal samples are presented.

The continued development of the Spallation Neutron Source external antenna H- ion sourcea)

NASA Astrophysics Data System (ADS)

Welton, R. F.; Carmichael, J.; Desai, N. J.; Fuga, R.; Goulding, R. H.; Han, B.; Kang, Y.; Lee, S. W.; Murray, S. N.; Pennisi, T.; Potter, K. G.; Santana, M.; Stockli, M. P.

2010-02-01

The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that the SNS will meet its operational commitments as well as provide for future facility upgrades with high reliability, we are developing a rf-driven, H- ion source based on a water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions of this source have delivered up to 42 mA to the SNS front end and unanalyzed beam currents up to ˜100 mA (60 Hz, 1 ms) to the ion source test stand. This source was operated on the SNS accelerator from February to April 2009 and produced ˜35 mA (beam current required by the ramp up plan) with availability of ˜97%. During this run several ion source failures identified reliability issues, which must be addressed before the source re-enters production: plasma ignition, antenna lifetime, magnet cooling, and cooling jacket integrity. This report discusses these issues, details proposed engineering solutions, and notes progress to date.

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

DOE PAGES

Mauro, N. A.; Vogt, A. J.; Derendorf, K. S.; ...

2016-01-01

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. But, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. Furthermore, to demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr 64Ni 36 measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample ( 100 mg).« less

Electrostatic levitation facility optimized for neutron diffraction studies of high temperature liquids at a spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mauro, N. A., E-mail: namauro@noctrl.edu; Vogt, A. J.; Derendorf, K. S.

2016-01-15

Neutron diffraction studies of metallic liquids provide valuable information about inherent topological and chemical ordering on multiple length scales as well as insight into dynamical processes at the level of a few atoms. However, there exist very few facilities in the world that allow such studies to be made of reactive metallic liquids in a containerless environment, and these are designed for use at reactor-based neutron sources. We present an electrostatic levitation facility, NESL (for Neutron ElectroStatic Levitator), which takes advantage of the enhanced capabilities and increased neutron flux available at spallation neutron sources (SNSs). NESL enables high quality elasticmore » and inelastic neutron scattering experiments to be made of reactive metallic and other liquids in the equilibrium and supercooled temperature regime. The apparatus is comprised of a high vacuum chamber, external and internal neutron collimation optics, and a sample exchange mechanism that allows up to 30 samples to be processed between chamber openings. Two heating lasers allow excellent sample temperature homogeneity, even for samples approaching 500 mg, and an automated temperature control system allows isothermal measurements to be conducted for times approaching 2 h in the liquid state, with variations in the average sample temperature of less than 0.5%. To demonstrate the capabilities of the facility for elastic scattering studies of liquids, a high quality total structure factor for Zr{sub 64}Ni{sub 36} measured slightly above the liquidus temperature is presented from experiments conducted on the nanoscale-ordered materials diffractometer (NOMAD) beam line at the SNS after only 30 min of acquisition time for a small sample (∼100 mg)« less

Commissioning of cryogenic system for China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Ye, Bin; He, Chongchao; Li, Na; Ding, Meiying; Wang, Yaqiong; Yu, Zhang; He, Kun

2017-12-01

China Spallation Neutron Source(CSNS) cryogenic system provides supercritical cryogenic hydrogen to neutron moderators, including a helium refrigerator, hydrogen loop and hydrogen safety equipment. The helium refrigerator is provided by Linde with cooling capacity of 2200 W at 20 K. Hydrogen loop system mainly includes cryogenic hydrogen pipes, hydrogen circulator cold-box and accumulator cold-box. Cryogenic hydrogen pump, ortho-para convertor, helium-hydrogen heat-exchanger, hydrogen heater and accumulator are integrated in hydrogen circulation cold-box, and accumulator cold-box. Hydrogen safety equipment includes safety valves, rupture disk, hydrogen sensor, flame detector and other equipment to ensure that cryogenic system in dangerous situations will go down, vents, or takes other measures. The cryogenic system commissioning work includes four steps. First, in order to test the refrigerating capacity of refrigerator, when acceptance testing, refrigerator internal heater was used as thermal load. Second, using simulation load as heat load of moderator, hydrogen loop use helium instead of hydrogen, and cooled down to 20 K, then re-warming and test the leak detection of hydrogen loop system. Third, base on the step 2, using hydrogen as working medium, and optimized the control logic. Forth, cryogenic system with the moderators joint commissioning. Now, cryogenic system is connected with the moderators, and the forth step will be carried out in the near future.

γ-Ray background sources in the VESUVIO spectrometer at ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

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

2009-09-01

An investigation of the gamma background was carried out in the VESUVIO spectrometer at the ISIS spallation neutron source. This study, performed with a yttrium-aluminum-perovskite (YAP) scintillator, follows high resolution pulse height measurements of the gamma background carried out on the same instrument with the use of a high-purity germanium detector. In this experimental work, a mapping of the gamma background was attempted, trying to find the spatial distribution and degree of directionality of the different contributions identified in the previous study. It is found that the gamma background at low times is highly directional and mostly due to the gamma rays generated in the moderator-decoupler system. The other contributions, consistently to the findings of a previous experiment, are identified as a nearly isotropic one due to neutron absorption in the walls of the experimental hall, and a directional one coming from the beam dump.

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

DOE PAGES

Ito, Takeyasu M.; Adamek, E. R.; Callahan, N. B.; ...

2018-01-29

We report the ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN densitymore » measured at the exit of the biological shield was 184(32) UCN / cm 3, a fourfold increase from the highest previously reported. Finally, the polarized UCN density stored in an external chamber was measured to be 39(7) UCN / cm 3, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ(d n) = 3 × 10 -27 e cm.« less

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

NASA Astrophysics Data System (ADS)

Ito, T. M.; Adamek, E. R.; Callahan, N. B.; Choi, J. H.; Clayton, S. M.; Cude-Woods, C.; Currie, S.; Ding, X.; Fellers, D. E.; Geltenbort, P.; Lamoreaux, S. K.; Liu, C.-Y.; MacDonald, S.; Makela, M.; Morris, C. L.; Pattie, R. W.; Ramsey, J. C.; Salvat, D. J.; Saunders, A.; Sharapov, E. I.; Sjue, S.; Sprow, A. P.; Tang, Z.; Weaver, H. L.; Wei, W.; Young, A. R.

2018-01-01

The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was 184 (32 ) UCN /cm3 , a fourfold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be 39 (7 ) UCN /cm3 , which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ (dn) =3 ×10-27e cm .

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ito, Takeyasu M.; Adamek, E. R.; Callahan, N. B.

We report the ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN densitymore » measured at the exit of the biological shield was 184(32) UCN / cm 3, a fourfold increase from the highest previously reported. Finally, the polarized UCN density stored in an external chamber was measured to be 39(7) UCN / cm 3, which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ(d n) = 3 × 10 -27 e cm.« less

Validation of Monte Carlo simulation of neutron production in a spallation experiment

DOE PAGES

Zavorka, L.; Adam, J.; Artiushenko, M.; ...

2015-02-25

A renewed interest in experimental research on Accelerator-Driven Systems (ADS) has been initiated by the global attempt to produce energy from thorium as a safe(r), clean(er) and (more) proliferation-resistant alternative to the uranium-fuelled thermal nuclear reactors. The ADS research has been actively pursued at the Joint Institute for Nuclear Research (JINR), Dubna, since decades. Most recently, the emission of fast neutrons was experimentally investigated at the massive (m = 512 kg) natural uranium spallation target QUINTA. The target has been irradiated with the relativistic deuteron beams of energy from 0.5 AGeV up to 4 AGeV at the JINR Nuclotron acceleratormore » in numerous experiments since 2011. Neutron production inside the target was studied through the gamma-ray spectrometry measurement of natural uranium activation detectors. Experimental reaction rates for (n,γ), (n,f) and (n,2n) reactions in uranium have provided valuable information about the neutron distribution over a wide range of energies up to some GeV. The experimental data were compared to the predictions of Monte Carlo simulations using the MCNPX 2.7.0 code. In conclusion, the results are presented and potential sources of partial disagreement are discussed later in this work.« less

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

DOE PAGES

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; ...

2014-10-02

Here we discuss a gripping capability that was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory.

Characterization of irradiated AISI 316L stainless steel disks removed from the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vevera, Bradley J; Hyres, James W; McClintock, David A

2014-01-01

Irradiated AISI 316L stainless steel disks were removed from the Spallation Neutron Source (SNS) for post-irradiation examination (PIE) to assess mechanical property changes due to radiation damage and erosion of the target vessel. Topics reviewed include high-resolution photography of the disk specimens, cleaning to remove mercury (Hg) residue and surface oxides, profile mapping of cavitation pits using high frequency ultrasonic testing (UT), high-resolution surface replication, and machining of test specimens using wire electrical discharge machining (EDM), tensile testing, Rockwell Superficial hardness testing, Vickers microhardness testing, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The effectiveness of the cleaning proceduremore » was evident in the pre- and post-cleaning photography and permitted accurate placement of the test specimens on the disks. Due to the limited amount of material available and the unique geometry of the disks, machine fixturing and test specimen design were critical aspects of this work. Multiple designs were considered and refined during mock-up test runs on unirradiated disks. The techniques used to successfully machine and test the various specimens will be presented along with a summary of important findings from the laboratory examinations.« less

Radionuclide production and dose rate estimation during the commissioning of the W-Ta spallation target

NASA Astrophysics Data System (ADS)

Yu, Q. Z.; Liang, T. J.

2018-06-01

China Spallation Neutron Source (CSNS) is intended to begin operation in 2018. CSNS is an accelerator-base multidisciplinary user facility. The pulsed neutrons are produced by a 1.6GeV short-pulsed proton beam impinging on a W-Ta spallation target, at a beam power of100 kW and a repetition rate of 25 Hz. 20 neutron beam lines are extracted for the neutron scattering and neutron irradiation research. During the commissioning and maintenance scenarios, the gamma rays induced from the W-Ta target can cause the dose threat to the personal and the environment. In this paper, the gamma dose rate distributions for the W-Ta spallation are calculated, based on the engineering model of the target-moderator-reflector system. The shipping cask is analyzed to satisfy the dose rate limit that less than 2 mSv/h at the surface of the shipping cask. All calculations are performed by the Monte carlo code MCNPX2.5 and the activation code CINDER’90.

Experiment Automation with a Robot Arm using the Liquids Reflectometer Instrument at the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zolnierczuk, Piotr A; Vacaliuc, Bogdan; Sundaram, Madhan

The Liquids Reflectometer instrument installed at the Spallation Neutron Source (SNS) enables observations of chemical kinetics, solid-state reactions and phase-transitions of thin film materials at both solid and liquid surfaces. Effective measurement of these behaviors requires each sample to be calibrated dynamically using the neutron beam and the data acquisition system in a feedback loop. Since the SNS is an intense neutron source, the time needed to perform the measurement can be the same as the alignment process, leading to a labor-intensive operation that is exhausting to users. An update to the instrument control system, completed in March 2013, implementedmore » the key features of automated sample alignment and robot-driven sample management, allowing for unattended operation over extended periods, lasting as long as 20 hours. We present a case study of the effort, detailing the mechanical, electrical and software modifications that were made as well as the lessons learned during the integration, verification and testing process.« less

Radiation effects in structural materials of spallation targets

NASA Astrophysics Data System (ADS)

Jung, P.

2002-02-01

Effects of radiation damage by protons and neutrons in structural materials of spallation neutron sources are reviewed. Effects of atomic displacements, defect mobility and transmutation products, especially hydrogen and helium, on physical and mechanical properties are discussed. The most promising candidate materials (austenitic stainless steels, ferritic/martensitic steels and refractory alloys) are compared, and needed investigations are identified.

Low-energy beam transport studies supporting the spallation neutron source 1-MW beam operation.

PubMed

Han, B X; Kalvas, T; Tarvainen, O; Welton, R F; Murray, S N; Pennisi, T R; Santana, M; Stockli, M P

2012-02-01

The H(-) injector consisting of a cesium enhanced RF-driven ion source and a 2-lens electrostatic low-energy beam transport (LEBT) system supports the spallation neutron source 1 MW beam operation with ∼38 mA beam current in the linac at 60 Hz with a pulse length of up to ∼1.0 ms. In this work, two important issues associated with the low-energy beam transport are discussed: (1) inconsistent dependence of the post-radio frequency quadrupole accelerator beam current on the ion source tilt angle and (2) high power beam losses on the LEBT electrodes under some off-nominal conditions compromising their reliability.

Low-level rf control of Spallation Neutron Source: System and characterization

NASA Astrophysics Data System (ADS)

Ma, Hengjie; Champion, Mark; Crofford, Mark; Kasemir, Kay-Uwe; Piller, Maurice; Doolittle, Lawrence; Ratti, Alex

2006-03-01

The low-level rf control system currently commissioned throughout the Spallation Neutron Source (SNS) LINAC evolved from three design iterations over 1 yr intensive research and development. Its digital hardware implementation is efficient, and has succeeded in achieving a minimum latency of less than 150 ns which is the key for accomplishing an all-digital feedback control for the full bandwidth. The control bandwidth is analyzed in frequency domain and characterized by testing its transient response. The hardware implementation also includes the provision of a time-shared input channel for a superior phase differential measurement between the cavity field and the reference. A companion cosimulation system for the digital hardware was developed to ensure a reliable long-term supportability. A large effort has also been made in the operation software development for the practical issues such as the process automations, cavity filling, beam loading compensation, and the cavity mechanical resonance suppression.

Assessment of Laser-Driven Pulsed Neutron Sources for Poolside Neutron-based Advanced NDE – A Pathway to LANSCE-like Characterization at INL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roth, Markus; Vogel, Sven C.; Bourke, Mark Andrew M.

A variety of opportunities for characterization of fresh nuclear fuels using thermal (~25meV) and epithermal (~10eV) neutrons have been documented at Los Alamos National Laboratory. They include spatially resolved non-destructive characterization of features, isotopic enrichment, chemical heterogeneity and stoichiometry. The LANSCE spallation neutron source is well suited in neutron fluence and temporal characteristics for studies of fuels. However, recent advances in high power short pulse lasers suggest that compact neutron sources might, over the next decade, become viable at a price point that would permit their consideration for poolside characterization on site at irradiation facilities. In a laser-driven neutron sourcemore » the laser is used to accelerate deuterium ions into a beryllium target where neutrons are produced. At this time, the technology is new and their total neutron production is approximately four orders of magnitude less than a facility like LANSCE. However, recent measurements on a sub-optimized system demonstrated >10 10 neutrons in sub-nanosecond pulses in predominantly forward direction. The compactness of the target system compared to a spallation target may allow exchanging the target during a measurement to e.g. characterize a highly radioactive sample with thermal, epithermal, and fast neutrons as well as hard X-rays, thus avoiding sample handling. At this time several groups are working on laser-driven neutron production and are advancing concepts for lasers, laser targets, and optimized neutron target/moderator systems. Advances in performance sufficient to enable poolside fuels characterization with LANSCE-like fluence on sample within a decade may be possible. This report describes the underlying physics and state-of-the-art of the laser-driven neutron production process from the perspective of the DOE/NE mission. It also discusses the development and understanding that will be necessary to provide customized capability for

Data processing workflow for time of flight polarized neutrons inelastic measurements

DOE PAGES

Savici, Andrei T.; Zaliznyak, Igor A.; Ovidiu Garlea, V.; ...

2017-06-01

We discuss the data processing workflow for polarized neutron scattering measurements performed at HYSPEC spectrometer at the Spallation Neutron Source, Oak Ridge National Laboratory. The effects of the focusing Heusler crystal polarizer and the wide-angle supermirror transmission polarization analyzer are added to the data processing flow of the non-polarized case. The implementation is done using the Mantid software package.

Transmutation of 129I and 237Np using spallation neutrons produced by 1.5, 3.7 and 7.4 GeV protons

NASA Astrophysics Data System (ADS)

Wan, J.-S.; Schmidt, Th.; Langrock, E.-J.; Vater, P.; Brandt, R.; Adam, J.; Bradnova, V.; Bamblevski, V. P.; Gelovani, L.; Gridnev, T. D.; Kalinnikov, V. G.; Krivopustov, M. I.; Kulakov, B. A.; Sosnin, A. N.; Perelygin, V. P.; Pronskikh, V. S.; Stegailov, V. I.; Tsoupko-Sitnikov, V. M.; Modolo, G.; Odoj, R.; Phlippen, P.-W.; Zamani-Valassiadou, M.; Adloff, J. C.; Debeauvais, M.; Hashemi-Nezhad, S. R.; Guo, S.-L.; Li, L.; Wang, Y.-L.; Dwivedi, K. K.; Zhuk, I. V.; Boulyga, S. F.; Lomonossova, E. M.; Kievitskaja, A. F.; Rakhno, I. L.; Chigrinov, S. E.; Wilson, W. B.

2001-05-01

Small samples of 129I and 237Np, two long-lived radwaste nuclides, were exposed to spallation neutron fluences from relatively small metal targets of lead and uranium, that were surrounded with a 6 cm thick paraffin moderator, and irradiated with 1.5, 3.7 and 7.4 GeV protons. The (n,γ) transmutation rates were determined for these nuclides. Conventional radiochemical La- and U-sensors and a variety of solid-state nuclear track detectors were irradiated simultaneously with secondary neutrons. Compared with results from calculations with well-known cascade codes (LAHET from Los Alamos and DCM/CEM from Dubna), the observed secondary neutron fluences are larger.

Mercury target R&D for the Oak Ridge spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haines, J.R.; DiStefano, J.; Farrell, K.

1996-06-01

The conceptual design for the Oak Ridge Spallation Neutron Source (ORSNS) incorporates liquid mercury as its reference target material. A flowing liquid target was selected mainly because of the increased power handling capability possible with the convective transport process. The major reasons for choosing mercury as the liquid target material are because it: (1) is a liquid at room temperature, (2) has good heat transport properties, and (3) has a high atomic number and mass density resulting in high neutron yield and source brightness. Since liquid targets are not widely utilized in presently operating accelerator targets and because of themore » challenges posed by the intense, pulsed thermal energy deposition ({approximately}20-100 kJ deposited during each 1-10 {mu}s pulse), considerable R&D is planned for the mercury target concept. The key feasibility issue that will be addressed in early R&D efforts are the effects of the thermal shock environment, which will include development and testing of approaches to mitigate these effects. Materials compatiblity and ES&H issues associated with the use of liquid mercury are also of major importance in early R&D efforts. A brief description of the mercury target design concept, results of initial evaluations of its performance characteristics, identification of its critical issues, and an outline of the R&D program aimed at addressing these issues will be presented.« less

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

NASA Astrophysics Data System (ADS)

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

2015-02-01

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

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Kim, S.-H.; Afanador, R.; Barnhart, D. L.; Crofford, M.; Degraff, B. D.; Doleans, M.; Galambos, J.; Gold, S. W.; Howell, M. P.; Mammosser, J.; McMahan, C. J.; Neustadt, T. S.; Peters, C.; Saunders, J. W.; Strong, W. H.; Vandygriff, D. J.; Vandygriff, D. M.

2017-04-01

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenance activities for cryomodules are introduced.

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

DOE PAGES

Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.; ...

2017-02-04

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less

Overview of ten-year operation of the superconducting linear accelerator at the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Sang-Ho; Afanador, Ralph; Barnhart, Debra L.

The Spallation Neutron Source (SNS) has acquired extensive operational experience of a pulsed proton superconducting linear accelerator (SCL) as a user facility. Numerous lessons have been learned in its first 10 years operation to achieve a stable and reliable operation of the SCL. In this paper, an overview of the SNS SCL design, qualification of superconducting radio frequency (SRF) cavities and ancillary subsystems, an overview of the SNS cryogenic system, the SCL operation including SCL output energy history and downtime statistics, performance stability of the SRF cavities, efforts for SRF cavity performance recovery and improvement at the SNS, and maintenancemore » activities for cryomodules are introduced.« less

Improvements to the internal and external antenna H(-) ion sources at the Spallation Neutron Source.

PubMed

Welton, R F; Dudnikov, V G; Han, B X; Murray, S N; Pennisi, T R; Pillar, C; Santana, M; Stockli, M P; Turvey, M W

2014-02-01

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30-40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 mA of H(-) beam current (∼1 ms, 60 Hz) at 65-kV into a Radio Frequency Quadrupole (RFQ) accelerator through a closely coupled electrostatic Low-Energy Beam Transport system. Over the last several years a decrease in RFQ transmission and issues with internal antennas has stimulated source development at the SNS both for the internal and external antenna ion sources. This report discusses progress in improving internal antenna reliability, H(-) yield improvements which resulted from modifications to the outlet aperture assembly (applicable to both internal and external antenna sources) and studies made of the long standing problem of beam persistence with the external antenna source. The current status of the external antenna ion source will also be presented.

Electrical Engineering in Los Alamos Neutron Science Center Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, Michael James

The field of electrical engineering plays a significant role in particle accelerator design and operations. Los Alamos National Laboratories LANSCE facility utilizes the electrical energy concepts of power distribution, plasma generation, radio frequency energy, electrostatic acceleration, signals and diagnostics. The culmination of these fields produces a machine of incredible potential with uses such as isotope production, neutron spallation, neutron imaging and particle analysis. The key isotope produced in LANSCE isotope production facility is Strontium-82 which is utilized for medical uses such as cancer treatment and positron emission tomography also known as PET scans. Neutron spallation is one of the verymore » few methods used to produce neutrons for scientific research the other methods are natural decay of transuranic elements from nuclear reactors. Accelerator produce neutrons by accelerating charged particles into neutron dense elements such as tungsten imparting a neutral particle with kinetic energy, this has the benefit of producing a large number of neutrons as well as minimizing the waste generated. Utilizing the accelerator scientist can gain an understanding of how various particles behave and interact with matter to better understand the natural laws of physics and the universe around us.« less

MW Spallation Neutron Sources for Fusion Materials Testing

ScienceCinema

Dr. Donald Rej

2018-04-18

Dr. Donald Rej of Los Alamos National Laboratory presents an overview of issues, needs, and performance gaps related to materials testing and how they are being addressed at their facility. Current projects such as the Los Alamos Neutron Science Center (LANSCE) and Matter-Radiation Interactions in Extremes (MaRIE) are also discussed.

HEKATE-A novel grazing incidence neutron scattering concept for the European Spallation Source.

PubMed

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

HEKATE—A novel grazing incidence neutron scattering concept for the European Spallation Source

NASA Astrophysics Data System (ADS)

Glavic, Artur; Stahn, Jochen

2018-03-01

Structure and magnetism at surfaces and buried interfaces on the nanoscale can only be accessed by few techniques, one of which is grazing incidence neutron scattering. While the technique has its strongest limitation in a low signal and large background, due to the low scattering probability and need for high resolution, it can be expected that the high intensity of the European Spallation Source in Lund, Sweden, will make many more such studies possible, warranting a dedicated beamline for this technique. We present an instrument concept, Highly Extended K range And Tunable Experiment (HEKATE), for surface scattering that combines the advantages of two Selene neutron guides with unique capabilities of spatially separated distinct wavelength frames. With this combination, it is not only possible to measure large specular reflectometry ranges, even on free liquid surfaces, but also to use two independent incident beams with tunable sizes and resolutions that can be optimized for the specifics of the investigated samples. Further the instrument guide geometry is tuned for reduction of high energy particle background and only uses low to moderate supermirror coatings for high reliability and affordable cost.

Chamber for mechanical testing in H2 with observation by neutron scattering

NASA Astrophysics Data System (ADS)

Connolly, Matthew; Bradley, Peter; Slifka, Andrew; Drexler, Elizabeth

2017-06-01

A gas-pressure chamber has been designed, constructed, and tested at a moderate pressure (3.4 MPa, 500 psi) and has the capability of mechanical loading of steel specimens for neutron scattering measurements. The chamber will allow a variety of in situ neutron scattering measurements: in particular, diffraction, quasielastic scattering, inelastic scattering, and imaging. The chamber is compatible with load frames available at the user facilities at the NIST Center for Neutron Research and Oak Ridge National Laboratory Spallation Neutron Source. A demonstration of neutron Bragg edge imaging using the chamber is presented.

New controller for high voltage converter modulator at spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wezensky, Mark W; Brown, David L; Lee, Sung-Woo

2017-01-01

The Spallation Neutron Source (SNS) has developed a new control system for the High Voltage Convertor Modulator (HVCM) at the SNS to replace the original control system which is approaching obsolescence. The original system was based on controllers for similar high voltage systems that were already in use [1]. The new controller, based on National Instruments PXI/FlexRIO Field Programmable Gate Array (FPGA) platform, offers enhancements such as modular construction, flexibility and non-proprietary software. The new controller also provides new capabilities like various methods for modulator pulse flattening, waveform capture, and first fault detection. This paper will discuss the design ofmore » the system, including the human machine interface, based on lessons learned at the SNS and other projects. It will also discuss performance and other issues related to its operation in an accelerator facility which requires high availability. To date, 73% of the operational HVCMs have been upgraded to with the new controller, and the remainder are scheduled for completion by mid-2017.« less

Stripper foil failure modes and cures at the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cousineau, Sarah M; Galambos, John D; Kim, Sang-Ho

2011-01-01

The Spallation Neutron Source comprises a 1 GeV, 1.4 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the $H^0$ excited states created during the $H^-$ charge exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming $H^-$ beam, which circled around to strike the foilmore » bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less

Operational performance characteristics of the WISH detector array on the ISIS spallation neutron source

NASA Astrophysics Data System (ADS)

Duxbury, D.; Khalyavin, D.; Manuel, P.; Raspino, D.; Rhodes, N.; Schooneveld, E.; Spill, E.

2014-12-01

The performance of the position sensitive neutron detector array of the WISH diffractometer is discussed. WISH (Wide angle In a Single Histogram) is one of the seven instruments currently available for users on the second target station (TS2) of the ISIS spallation neutron source, and is used mainly for magnetic studies of materials. WISH is instrumented with an array of 10 detector panels, covering an angular range of 320o, orientated in two semi-cylindrical annuli around a central sample position at a radius of 2.2m. In total the 10 detector panels are composed of 1520 3He based position sensitive detector tubes. Each tube has an active length of one metre, a diameter of 8mm and is filled with 3He at 15 bar. The specification for the WISH detectors included a neutron detection efficiency of 50% at a neutron wavelength of 1Å with good gamma rejection. A position resolution better than 8 mm FWHM along the length of the tubes was also required which has been met experimentally. Results obtained from the detector arrays showing pulse height and positional information both prior to and post installation are shown. The first 5 of the 10 detector panels have been operational since 2009, and comparable diffraction data from powder and single crystal samples taken from the remaining 5 panels (installation completed in 2013) shows that we have a detector array with a highly stable performance which is easily assembled and maintained. Finally some real user data is shown, highlighting the excellent quality of data attainable with this instrument.

Design of the low energy beam transport line for the China spallation neutron source

NASA Astrophysics Data System (ADS)

Li, Jin-Hai; Ouyang, Hua-Fu; Fu, Shi-Nian; Zhang, Hua-Shun; He, Wei

2008-03-01

The design of the China Spallation Neutron Source (CSNS) low-energy beam transport (LEBT) line, which locates between the ion source and the radio-frequency quadrupole (RFQ), has been completed with the TRACE3D code. The design aims at perfect matching, primary chopping, a small emittance growth and sufficient space for beam diagnostics. The line consists of three solenoids, three vacuum chambers, two steering magnets and a pre-chopper. The total length of LEBT is about 1.74 m. This LEBT is designed to transfer 20 mA of H-pulsed beam from the ion source to the RFQ. An induction cavity is adopted as the pre-chopper. The electrostatic octupole steerer is discussed as a candidate. A four-quadrant aperture for beam scraping and beam position monitoring is designed.

Gadolinium-148 and other spallation production cross section measurements for accelerator target facilities

NASA Astrophysics Data System (ADS)

Kelley, Karen Corzine

At the Los Alamos Neutron Science Center accelerator complex, protons are accelerated to 800 MeV and directed to two tungsten targets, Target 4 at the Weapons Neutron Research facility and the 1L target at the Lujan Center. The Department of Energy requires hazard classification analyses to be performed on these targets and places limits on certain radionuclide inventories in the targets to avoid characterizing the facilities as "nuclear facilities." Gadolinium-148 is a radionuclide created from the spallation of tungsten. Allowed isotopic inventories are particularly low for this isotope because it is an alpha-particle emitter with a 75-year half-life. The activity level of Gadolinium-148 is low, but it encompasses almost two-thirds of the total dose burden for the two tungsten targets based on present yield estimates. From a hazard classification standpoint, this severely limits the lifetime of these tungsten targets. The cross section is not well-established experimentally and this is the motivation for measuring the Gadolinium-148 production cross section from tungsten. In a series of experiments at the Weapons Neutron Research facility, Gadolinium-148 production was measured for 600- and 800-MeV protons on tungsten, tantalum, and gold. These experiments used 3 mum thin tungsten, tantalum, and gold foils and 10 mum thin aluminum activation foils. In addition, spallation yields were determined for many short-lived and long-lived spallation products with these foils using gamma and alpha spectroscopy and compared with predictions of the Los Alamos National Laboratory codes CEM2k+GEM2 and MCNPX. The cumulative Gadolinium-148 production cross section measured from tantalum, tungsten, and gold for incident 600-MeV protons were 15.2 +/- 4.0, 8.31 +/- 0.92, and 0.591 +/- 0.155, respectively. The average production cross sections measured at 800 MeV were 28.6 +/- 3.5, 19.4 +/- 1.8, and 3.69 +/- 0.50 for tantalum, tungsten, and gold, respectively. These cumulative

R&D of A MW-class solid-target for a spallation neutron source

NASA Astrophysics Data System (ADS)

Kawai, Masayoshi; Furusaka, Michihiro; Kikuchi, Kenji; Kurishita, Hiroaki; Watanabe, Ryuzo; Li, Jing-Feng; Sugimoto, Katsuhisa; Yamamura, Tsutomu; Hiraoka, Yutaka; Abe, Katsunori; Hasegawa, Akira; Yoshiie, Masatoshi; Takenaka, Hiroyuki; Mishima, Katsuichiro; Kiyanagi, Yoshiaki; Tanabe, Tetsuo; Yoshida, Naoaki; Igarashi, Tadashi

2003-05-01

R&D for a MW-class solid target composed of tungsten was undertaken to produce a pulsed intense neutron source for a future neutron scattering-facility. In order to solve the corrosion of tungsten, tungsten target blocks were clad with tantalum by means of HIP'ing, brazing and electrolytic coating in a molten salt bath. The applicability of the HIP'ing method was tested through fabricating target blocks for KENS (spallation neutron source at KEK). A further investigation to certify the optimum HIP conditions was made with the small punch test method. The results showed that the optimum temperature was 1500 °C at which the W/Ta interface gave the strongest fracture strength. In the case of the block with a hole for thermocouple, it was found that the fabrication preciseness of a straight hole and a tantalum sheath influenced the results. The development of a tungsten stainless-steel alloy was tried to produce a bare tungsten target, using techniques in powder metallurgy. Corrosion tests for various tungsten alloys were made while varying the water temperature and velocity. The mass loss of tungsten in very slow water at 180 °C was as low as 0.022 mg/y, but increased remarkably with water velocity. Simulation experiments for radiation damage to supplement the STIP-III experiments were made to investigate material hardening by hydrogen and helium, and microstructures irradiated by electrons. Both experiments showed consistent results on the order of the dislocation numbers and irradiation hardness among the different tungsten materials. Thermal-hydraulic designs were made for two types of solid target system of tungsten: slab and rod geometry as a function of the proton beam power. The neutronic performance of a solid target system was compared with that of mercury target based on Monte Carlo calculations by using the MCNP code.

The Los Alamos Neutron Science Center Spallation Neutron Sources

NASA Astrophysics Data System (ADS)

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutrons are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ∼100 keV. The characteristics of these sources, and

High power neutron production targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wender, S.

1996-06-01

The author describes issues of concern in the design of targets and associated systems for high power neutron production facilities. The facilities include uses for neutron scattering, accelerator driven transmutation, accelerator production of tritium, short pulse spallation sources, and long pulse spallation sources. Each of these applications requires a source with different design needs and consequently different implementation in practise.

Use of the WNR spallation neutron source at LAMPF to determine the absolute efficiency of a neutron scintillation detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Staples, P.A.; Egan, J.J.; Kegel, G.H.R.

1994-06-01

Prompt fission neutron spectrum measurements at the University of Massachusetts Lowell 5.5 MV Van de Graaff accelerator laboratory require that the neutron detector efficiency be well known over a neutron energy range of 100 keV to 20 MeV. The efficiency of the detector, has been determined for energies greater than 5.0 MeV using the Weapons Neutron Research (WNR) white neutron source at the Los Alamos Meson Physics Facility (LAMPF) in a pulsed beam, time-of-flight (TOF) experiment. Carbon matched polyethylene and graphite scatterers were used to obtain a hydrogen spectrum. The detector efficiency was determined using the well known H(n,n) scatteringmore » cross section. Results are compared to the detector efficiency calculation program SCINFUL available from the Radiation Shielding Information Center at Oak Ridge National Laboratory.« less

The Los Alamos Neutron Science Center Spallation Neutron Sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources

The Los Alamos Neutron Science Center Spallation Neutron Sources

DOE PAGES

Nowicki, Suzanne F.; Wender, Stephen A.; Mocko, Michael

2017-10-26

The Los Alamos Neutron Science Center (LANSCE) provides the scientific community with intense sources of neutrons, which can be used to perform experiments supporting civilian and national security research. These measurements include nuclear physics experiments for the defense program, basic science, and the radiation effect programs. This paper focuses on the radiation effects program, which involves mostly accelerated testing of semiconductor parts. When cosmic rays strike the earth's atmosphere, they cause nuclear reactions with elements in the air and produce a wide range of energetic particles. Because neutrons are uncharged, they can reach aircraft altitudes and sea level. These neutronsmore » are thought to be the most important threat to semiconductor devices and integrated circuits. The best way to determine the failure rate due to these neutrons is to measure the failure rate in a neutron source that has the same spectrum as those produced by cosmic rays. Los Alamos has a high-energy and a low-energy neutron source for semiconductor testing. Both are driven by the 800-MeV proton beam from the LANSCE accelerator. The high-energy neutron source at the Weapons Neutron Research (WNR) facility uses a bare target that is designed to produce fast neutrons with energies from 100 keV to almost 800 MeV. The measured neutron energy distribution from WNR is very similar to that of the cosmic-ray-induced neutrons in the atmosphere. However, the flux provided at the WNR facility is typically 5×107 times more intense than the flux of the cosmic-ray-induced neutrons. This intense neutron flux allows testing at greatly accelerated rates. An irradiation test of less than an hour is equivalent to many years of neutron exposure due to cosmic-ray neutrons. The low-energy neutron source is located at the Lujan Neutron Scattering Center. It is based on a moderated source that provides useful neutrons from subthermal energies to ~100 keV. The characteristics of these sources

Spallation of Cu by 500- and 1570-MeV. pi. /sup -/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haustein, P.E.; Ruth, T.J.

1978-11-01

Relative yields of 36 products extending from /sup 7/Be to /sup 65/Zn have been measured for the interaction of 500- and 1570-MeV negative pions with Cu. These results are compared with calculations from the ISOBAR model, with earlier studies of Cu spallation with lower (resonance) energy pions, energetic protons, and heavy ions. Relative yield patterns at both ..pi../sup -/ energies show only slight differences when compared to spallation by protons of comparable energy. Calculations from the ISOBAR model adequately reproduce the shapes of the mass yield and charge yield of the experimental data for 500-MeV ..pi../sup -/. The calculation, however,more » overestimates the yield of neutron-rich isotopes from deep spallation. At the 1570-MeV ..pi../sup -/ energy the yield patterns, charge-dispersion, and mass-yield curves are nearly identical to those for 2-GeV proton spallation. These results suggest that pion-nucleon resonance effects probably decrease at higher energies and that limiting fragmentation and factorization concepts may be applied to understanding high-energy pion spallation.« less

Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peter Kneisel; John Brawley; Richard Bundy

2001-06-01

The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV. For this energy range two types of cavities are needed with geometrical beta - values of beta = 0.61 and beta = 0.81. An aggressive cavity prototyping program is being pursued at Jlab, which calls for fabricating and testing of four beta = 0.61 cavities and two beta = 0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler of the TESLA type on each beam pipe and a port for amore » high power coaxial input coupler. Three of the four beta = 0.61 cavities will be used for a cryomodule test at the end of the year 2001. At this time two cavities of each type have been fabricated and the first tests on the beta = 0.61 cavity exceeded the design values for gradient and Q - value: Eacc = 10.3 MV/m and Q = 6.5 x 10{sup 9} at 2.1K. This paper will describe the cavity design with respect to electrical and mechanical features, the fabrication efforts and the results obtained with the different cavities existing at the time of the conference.« less

Comparison between experimental data and Monte-Carlo simulations of neutron production in spallation reactions of 0.7-1.5 GeV protons on a thick, lead target

NASA Astrophysics Data System (ADS)

Krása, A.; Majerle, M.; Krízek, F.; Wagner, V.; Kugler, A.; Svoboda, O.; Henzl, V.; Henzlová, D.; Adam, J.; Caloun, P.; Kalinnikov, V. G.; Krivopustov, M. I.; Stegailov, V. I.; Tsoupko-Sitnikov, V. M.

2006-05-01

Relativistic protons with energies 0.7-1.5 GeV interacting with a thick, cylindrical, lead target, surrounded by a uranium blanket and a polyethylene moderator, produced spallation neutrons. The spatial and energetic distributions of the produced neutron field were measured by the Activation Analysis Method using Al, Au, Bi, and Co radio-chemical sensors. The experimental yields of isotopes induced in the sensors were compared with Monte-Carlo calculations performed with the MCNPX 2.4.0 code.

In-situ structural integrity evaluation for high-power pulsed spallation neutron source - Effects of cavitation damage on structural vibration

NASA Astrophysics Data System (ADS)

Wan, Tao; Naoe, Takashi; Futakawa, Masatoshi

2016-01-01

A double-wall structure mercury target will be installed at the high-power pulsed spallation neutron source in the Japan Proton Accelerator Research Complex (J-PARC). Cavitation damage on the inner wall is an important factor governing the lifetime of the target-vessel. To monitor the structural integrity of the target vessel, displacement velocity at a point on the outer surface of the target vessel is measured using a laser Doppler vibrometer (LDV). The measured signals can be used for evaluating the damage inside the target vessel because of cyclic loading and cavitation bubble collapse caused by pulsed-beam induced pressure waves. The wavelet differential analysis (WDA) was applied to reveal the effects of the damage on vibrational cycling. To reduce the effects of noise superimposed on the vibration signals on the WDA results, analysis of variance (ANOVA) and analysis of covariance (ANCOVA), statistical methods were applied. Results from laboratory experiments, numerical simulation results with random noise added, and target vessel field data were analyzed by the WDA and the statistical methods. The analyses demonstrated that the established in-situ diagnostic technique can be used to effectively evaluate the structural response of the target vessel.

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

NASA Astrophysics Data System (ADS)

Kaiserfeld, Thomas

2016-03-01

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

RF H-minus ion source development in China spallation neutron source

NASA Astrophysics Data System (ADS)

Chen, W.; Ouyang, H.; Xiao, Y.; Liu, S.; Lü, Y.; Cao, X.; Huang, T.; Xue, K.

2017-08-01

China Spallation Neutron Source (CSNS) phase-I project currently uses a Penning surface plasma H- ion source, which has a life time of several weeks with occasional sparks between high voltage electrodes. To extend the life time of the ion source and prepare for the CSNS phase-II, we are trying to develop a RF negative hydrogen ion source with external antenna. The configuration of the source is similar to the DESY external antenna ion source and SNS ion source. However several changes are made to improve the stability and the life time. Firstly, Si3N4 ceramic with high thermal shock resistance, and high thermal conductivity is used for plasma chamber, which can endure an average power of 2000W. Secondly, the water-cooled antenna is brazed on the chamber to improve the energy efficiency. Thirdly, cesium is injected directly to the plasma chamber if necessary, to simplify the design of the converter and the extraction. Area of stainless steel exposed to plasma is minimized to reduce the sputtering and degassing. Instead Mo, Ta, and Pt coated materials are used to face the plasma, which makes the self-cleaning of the source possible.

A target development program for beamhole spallation neutron sources in the megawatt range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, G.S.; Atchison, F.

1995-10-01

Spallation sources as an alternative to fission neutron sources have been operating successfully up to 160 kW of beam power. With the next generation of these facilities aiming at the medium power range between 0.5 and 5 MW, loads on the targets will be high enough to make present experience of little relevance. With the 0.6 MW continuous facility SINQ under construction, and a 5 MW pulsed facility (ESS) under study in Europe, a research and development program is about to be started which aimes at assessing the limits of stationary and moving solid targets and the feasibility and potentialmore » benefits of flowing liquid metal targets. Apart from theoretical work and examination of existing irradiated material, including used targets from ISIS, it is intended to take advantage of the SINQ solid rod target design to improve the relevant data base by building the target in such a way that individual rods can be equipped as irradiation capsules.« less

Lorentz force detuning analysis of the Spallation Neutron Source (SNS) accelerating cavities.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitchell, R.R.; Matsumoto, K. Y.; Ciovati, G.

2001-01-01

The Spallation Neutron Source (SNS) project incorporates a superconducting radio-frequency (SRF) accelerator for the final section of the pulsed mode linac. Cavities with geometrical {beta} values of {beta}=0.61 and {beta}=0.81 are utilized in the SRF section, and are constructed out of thin-walled niobium with stiffener rings welded between the cells near the iris. The welded titanium helium vessel and tuner assembly restrains the cavity beam tubes. Cavities with {beta} values less than one have relatively steep and flat side-walls making the cavities susceptible to Lorentz force detuning. In addition, the pulsed RF induces cyclic Lorentz pressures that mechanically excite themore » cavities, producing a dynamic Lorentz force detuning different from a continuous RF system. The amplitude of the dynamic detuning for a given cavity design is a function of the mechanical damping, stiffness of the tuner/helium vessel assembly, RF pulse profile, and the RF pulse rate. This paper presents analysis and testing results to date, and indicates areas where more investigation is required.« less

Spectral unfolding of fast neutron energy distributions

NASA Astrophysics Data System (ADS)

Mosby, Michelle; Jackman, Kevin; Engle, Jonathan

2015-10-01

The characterization of the energy distribution of a neutron flux is difficult in experiments with constrained geometry where techniques such as time of flight cannot be used to resolve the distribution. The measurement of neutron fluxes in reactors, which often present similar challenges, has been accomplished using radioactivation foils as an indirect probe. Spectral unfolding codes use statistical methods to adjust MCNP predictions of neutron energy distributions using quantified radioactive residuals produced in these foils. We have applied a modification of this established neutron flux characterization technique to experimentally characterize the neutron flux in the critical assemblies at the Nevada National Security Site (NNSS) and the spallation neutron flux at the Isotope Production Facility (IPF) at Los Alamos National Laboratory (LANL). Results of the unfolding procedure are presented and compared with a priori MCNP predictions, and the implications for measurements using the neutron fluxes at these facilities are discussed.

SPEAR — ToF neutron reflectometer at the Los Alamos Neutron Science Center

NASA Astrophysics Data System (ADS)

Dubey, M.; Jablin, M. S.; Wang, P.; Mocko, M.; Majewski, J.

2011-11-01

This article discusses the Surface ProfilE Analysis Reflectometer (SPEAR), a vertical scattering geometry time-of-flight reflectometer, at the Los Alamos National Laboratory Lujan Neutron Scattering Center. SPEAR occupies flight path 9 and receives spallation neutrons from a polychromatic, pulsed (20Hz) source that pass through a liquid-hydrogen moderator at 20K coupled with a Be filter to shift their energy spectrum. The spallation neutrons are generated by bombarding a tungsten target with 800MeV protons obtained from an accelerator. The process produces an integrated neutron flux of ˜ 3.4×106 cm-2 s-1 at a proton current of 100 μA. SPEAR employs choppers and frame overlap mirrors to obtain a neutron wavelength range of 4.5-16 Å. SPEAR uses a single 200mm long 3He linear position-sensitive detector with ˜ 2 mm FWHM resolution for simultaneous studies of both specular and off-specular scattering. SPEAR's moderated neutrons are collimated into a beam which impinges from above upon a level sample with an average angle of 0.9° to the horizontal, to facilitate air-liquid interface studies. In the vertical direction, the beam converges at the sample position. The neutrons can be further collimated to the desired divergence by finely slitting the beam using a set of two 10B4C slit packages. The instrument is ideally suited to study organic and inorganic thin films with total thicknesses between 5 and 3000 Å in a variety of environments. Specifically designed sample chambers available at the instrument provide the opportunity to study biological systems at the solid-liquid interface. SPEAR's unique experimental capabilities are demonstrated by specific examples in this article. Finally, an outlook for SPEAR and perspectives on future instrumentation are discussed.

Spallation reactions: A successful interplay between modeling and applications

NASA Astrophysics Data System (ADS)

David, J.-C.

2015-06-01

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200MeV deuterons and 400MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. In the same year, R. Serber described the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a workshop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.

Analysis of radiation environmental safety for China's Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Wang, Qing-Bin; Wu, Qing-Biao; Ma, Zhong-Jian; Zhang, Qing-Jiang; Li, Nan; Wu, Jing-Min; Liu, Jian; Zhang, Gang

2010-07-01

The China Spallation Neutron Source (CSNS) is going to be located in Dalang Town, Dongguan City in the Guangdong Province. In this paper we report the results of the parameters related with environment safety based on experiential calculations and Monte Carlo simulations. The main project of the accelerator is an under ground construction. On top there is a 0.5 m concrete and 5.0 m soil covering for shielding, which can reduce the dose out of the tunnel's top down to 0.2 μSv/h. For the residents on the boundary of the CSNS, the dose produced by skyshine, which is caused by the penetrated radiation leaking from the top of the accelerator, is no more than 0.68 μSv/a. When CSNS is operating normally, the maximal annual effective dose due to the emission of gas from the tunnel is 2.40×10-3 mSv/a to the public adult, and 2.29×10-3 mSv/a to a child, both values are two orders of magnitude less than the limiting value for control and management. CSNS may give rise to an activation of the soil and groundwater in the nearest tunnels, where the main productions are 3H, 7Be, 22Na, 54Mn, etc. But the specific activity is less than the exempt specific activity in the national standard GB13376-92. So it is safe to say that the environmental impact caused by the activation of soil and groundwater is insignificant. To sum up, for CSNS, as a powerful neutron source device, driven by a high-energy high-current proton accelerator, a lot of potential factors affecting the environment exist. However, as long as effective shieldings for protection are adopted and strict rules are drafted, the environmental impact can be kept under control within the limits of the national standard.

Acoustic attenuation, phase and group velocities in liquid-filled pipes II: simulation for Spallation Neutron Sources and planetary exploration.

PubMed

Jiang, Jian; Baik, Kyungmin; Leighton, Timothy G

2011-08-01

This paper uses a finite element method (FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.

Stripper foil failure modes and cures at the Oak Rdige Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Plum, M.A.; Raparia, D.; Cousineau, S.M.

2011-03-28

The Oak Ridge Spallation Neutron Source comprises a 1 GeV, 1.5 MW linear accelerator followed by an accumulator ring and a liquid mercury target. To manage the beam loss caused by the H{sup 0} excited states created during the H{sup -} charge-exchange injection into the accumulator ring, the stripper foil is located inside one of the chicane dipoles. This has some interesting consequences that were not fully appreciated until the beam power reached about 840 kW. One consequence was sudden failure of the stripper foil system due to convoy electrons stripped from the incoming H{sup -} beam, which circled aroundmore » to strike the foil bracket and cause bracket failure. Another consequence is that convoy electrons can reflect back up from the electron catcher and strike the foil and bracket. An additional contributor to foil system failure is vacuum breakdown due to the charge developed on the foil by secondary electron emission. In this paper we detail these and other interesting failure mechanisms and describe the improvements we have made to mitigate them.« less

Effects of geochemical composition on neutron die-away measurements: Implications for Mars Science Laboratory's Dynamic Albedo of Neutrons experiment

NASA Astrophysics Data System (ADS)

Hardgrove, C.; Moersch, J.; Drake, D.

2011-12-01

The Dynamic Albedo of Neutrons (DAN) experiment, part of the scientific payload of the Mars Science Laboratory (MSL) rover mission, will have the ability to assess both the abundance and the burial depth of subsurface hydrogen as the rover traverses the Martian surface. DAN will employ a method of measuring neutron fluxes called “neutron die-away” that has not been used in previous planetary exploration missions. This method requires the use of a pulsed neutron generator that supplements neutrons produced via spallation in the subsurface by the cosmic ray background. It is well established in neutron remote sensing that low-energy (thermal) neutrons are sensitive not only to hydrogen content, but also to the macroscopic absorption cross-section of near-surface materials. To better understand the results that will be forthcoming from DAN, we model the effects of varying abundances of high absorption cross-section elements that are likely to be found on the Martian surface (Cl, Fe) on neutron die-away measurements made from a rover platform. Previously, the Mars Exploration Rovers (MER) Spirit and Opportunity found that elevated abundances of these two elements are commonly associated with locales that have experienced some form of aqueous activity in the past, even though hydrogen-rich materials are not necessarily still present. By modeling a suite of H and Cl compositions, we demonstrate that (for abundance ranges reasonable for Mars) both the elements will significantly affect DAN thermal neutron count rates. Additionally, we show that the timing of thermal neutron arrivals at the detector can be used together with the thermal neutron count rates to independently determine the abundances of hydrogen and high neutron absorption cross-section elements (the most important being Cl). Epithermal neutron die-away curves may also be used to separate these two components. We model neutron scattering in actual Martian compositions that were determined by the MER Alpha

Towards high-resolution neutron imaging on IMAT

NASA Astrophysics Data System (ADS)

Minniti, T.; Tremsin, A. S.; Vitucci, G.; Kockelmann, W.

2018-01-01

IMAT is a new cold-neutron imaging facility at the neutron spallation source ISIS at the Rutherford Appleton Laboratory, U.K.. The ISIS pulsed source enables energy-selective and energy-resolved neutron imaging via time-of-flight (TOF) techniques, which are available in addition to the white-beam neutron radiography and tomography options. A spatial resolution of about 50 μm for white-beam neutron radiography was achieved early in the IMAT commissioning phase. In this work we have made the first steps towards achieving higher spatial resolution. A white-beam radiography with 18 μm spatial resolution was achieved in this experiment. This result was possible by using the event counting neutron pixel detector based on micro-channel plates (MCP) coupled with a Timepix readout chip with 55 μm sized pixels, and by employing an event centroiding technique. The prospects for energy-selective neutron radiography for this centroiding mode are discussed.

CHELSI: a portable neutron spectrometer for the 20-800 MeV region.

PubMed

McLean, T D; Olsher, R H; Romero, L L; Miles, L H; Devine, R T; Fallu-Labruyere, A; Grudberg, P

2007-01-01

CHELSI is a CsI-based portable spectrometer being developed at Los Alamos National Laboratory for use in high-energy neutron fields. Based on the inherent pulse shape discrimination properties of CsI(Tl), the instrument flags charged particle events produced via neutron-induced spallation events. Scintillation events are processed in real time using digital signal processing and a conservative estimate of neutron dose rate is made based on the charged particle energy distribution. A more accurate dose estimate can be made by unfolding the 2D charged particle versus pulse height distribution to reveal the incident neutron spectrum from which dose is readily obtained. A prototype probe has been assembled and data collected in quasi-monoenergetic fields at The Svedberg Laboratory (TSL) in Uppsala as well as at the Los Alamos Neutron Science Center (LANSCE). Preliminary efforts at deconvoluting the shape/energy data using empirical response functions derived from time-of-flight measurements are described.

The CENNS-10 liquid argon detector to measure CEvNS at the Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Tayloe, R.

2018-04-01

The COHERENT collaboration is deploying a suite of low-energy detectors in a low-background corridor of the ORNL Spallation Neutron Source (SNS) to measure coherent elastic neutrino-nucleus scattering (CEvNS) on an array of nuclear targets employing different detector technologies. A measurement of CEvNS on different nuclei will test the N2-dependence of the CEvNS cross section and further the physics reach of the COHERENT effort. The first step of this program has been realized recently with the observation of CEvNS in a 14.6 kg CsI detector. Operation and deployment of Ge and NaI detectors are also underway. A 22 kg, single-phase, liquid argon detector (CENNS-10) started data-taking in Dec. 2016 and will provide results on CEvNS from a lighter nucleus. Initial results indicate that light output, pulse-shape discrimination, and background suppression are sufficient for a measurement of CEvNS on argon.

Neutron bursts from long laboratory sparks

NASA Astrophysics Data System (ADS)

Kochkin, P.; Lehtinen, N. G.; Montanya, J.; Van Deursen, A.; Ostgaard, N.

2016-12-01

Neutron emission in association with thunderstorms and lightning discharges was reported by different investigators from ground-based observation platforms. In both cases such emission is explained by photonuclear reaction, since high-energy gamma-rays in sufficient fluxes are routinely detected from both, lightning and thunderclouds. The required gamma-rays are presumably generated by high-energy electrons in Bremsstrahlung process after their acceleration via cold and/or relativistic runaway mechanisms. This phenomenon attracted moderate scientific attention until fast neutron bursts (up to 10 MeV) from long 1 MV laboratory sparks have been reported. Clearly, with such relatively low applied voltage the electrons are unable to accelerate to the energies required for photo/electro disintegration. Moreover, all known elementary neutron generation processes are not capable to explain this emission right away. We performed an independent laboratory experiment on long sparks with the aim to confirm or disprove the neutron emission from them. The experimental setup was assembled at High-Voltage Laboratory in Barcelona and contained a Marx generator in a cone-cone spark gap configuration. The applied voltage was as low as 800 kV and the gap distance was only 60 cm. Two ns-fast cameras were located near the gap capturing short-exposure images of the pre-breakdown phenomenon at the expected neutron generation time. A plastic scintillation detector sensitive to neutrons was covered in 11 cm of lead and placed near the spark gap. The detector was calibrated and showed good performance in neutron detection. Apart of it, voltage, currents through both electrodes, and three X-ray detectors were also monitored in sophisticated measuring system. We will give an overview of the previous experimental and theoretical work in this topic, and present the results of our new experimental campaign. The conclusions are based on good signal-to-noise ratio measurements and are

Neutron Scattering Facilities

Science.gov Websites

Low Energy Neutron Source (LENS), Indiana University Cyclotron Facility, USA McMaster Nuclear Reactor Research, Gaithersburg, Maryland, USA Peruvian Institute of Nuclear Energy (IPEN), Lima, Peru Spallation Nuclear Science and Technology Organisation, Lucas Heights, Australia High-flux Advanced Neutron

Novel diamond cells for neutron diffraction using multi-carat CVD anvils.

PubMed

Boehler, R; Molaison, J J; Haberl, B

2017-08-01

Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ∼0.15 mm 3 . High quality spectra were obtained in 1 h for crystalline Ni and in ∼8 h for disordered glassy carbon. These new techniques will open the way for routine megabar neutron diffraction experiments.

Electron volt spectroscopy on a pulsed neutron source

NASA Astrophysics Data System (ADS)

Newport, R. J.; Penfold, J.; Williams, W. G.

1984-07-01

The principal design aspects of a pulsed source neutron spectrometer in which the scattered neutron energy is determined by a resonance absorption filter difference method are discussed. Calculations of the accessible dynamic range, resolution and spectrum simulations are given for the spectrometer on a high intensity pulsed neutron source, such as the spallation neutron source (SNS) now being constructed at the Rutherford Appleton Laboratory. Special emphasis is made of the advantage gained by placing coarse and fixed energy-sensitive filters before and after the scatterer; these enhance the inelastic/elastic descrimination of the method. A brief description is given of a double difference filter method which gives a superior difference peak shape, as well as a better energy transfer resolution. Finally, some first results of scattering from zirconium hydride, obtained on a test spectrometer, are presented.

Cryogenic magnetic coil and superconducting magnetic shield for neutron electric dipole moment searches

NASA Astrophysics Data System (ADS)

Slutsky, S.; Swank, C. M.; Biswas, A.; Carr, R.; Escribano, J.; Filippone, B. W.; Griffith, W. C.; Mendenhall, M.; Nouri, N.; Osthelder, C.; Pérez Galván, A.; Picker, R.; Plaster, B.

2017-08-01

A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6 ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparatus [1], particularly the introduction of super-conducting magnetic shielding and the associated cryogenic apparatus. The magnetic gradients observed are sufficiently low for the nEDM search at SNS.

Production of radioactive isotopes through cosmic muon spallation in KamLAND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abe, S.; Furuno, K.; Gando, Y.

2010-02-15

Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in nu detectors, double-beta-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, themore » neutron production yield in the KamLAND liquid scintillator is measured to be Y{sub n}=(2.8+-0.3)x10{sup -4} mu{sup -1} g{sup -1} cm{sup 2}. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.« less

Neutron Collar Evolution and Fresh PWR Assembly Measurements with a New Fast Neutron Passive Collar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menlove, Howard Olsen; Geist, William H.; Root, Margaret A.

The passive neutron collar approach removes the effect of poison rods when using a 1mm Gd liner. This project sets out to solve the following challenges: BWR fuel assemblies have less mass and less neutron multiplication than PWR; and effective removal of cosmic ray spallation neutron bursts needed via QC tests.

Novel diamond cells for neutron diffraction using multi-carat CVD anvils

DOE PAGES

Boehler, R.; Molaison, J. J.; Haberl, B.

2017-08-17

Traditionally, neutron diffraction at high pressure has been severely limited in pressure because low neutron flux required large sample volumes and therefore large volume presses. At the high-flux Spallation Neutron Source at the Oak Ridge National Laboratory, we have developed in this paper new, large-volume diamond anvil cells for neutron diffraction. The main features of these cells are multi-carat, single crystal chemical vapor deposition diamonds, very large diffraction apertures, and gas membranes to accommodate pressure stability, especially upon cooling. A new cell has been tested for diffraction up to 40 GPa with an unprecedented sample volume of ~0.15 mm 3.more » High quality spectra were obtained in 1 h for crystalline Ni and in ~8 h for disordered glassy carbon. Finally, these new techniques will open the way for routine megabar neutron diffraction experiments.« less

Generic guide concepts for the European Spallation Source

NASA Astrophysics Data System (ADS)

Zendler, C.; Martin Rodriguez, D.; Bentley, P. M.

2015-12-01

The construction of the European Spallation Source (ESS) faces many challenges from the neutron beam transport point of view: the spallation source is specified as being driven by a 5 MW beam of protons, each with 2 GeV energy, and yet the requirements in instrument background suppression relative to measured signal vary between 10-6 and 10-8. The energetic particles, particularly above 20 MeV, which are expected to be produced in abundance in the target, have to be filtered in order to make the beamlines safe, operational and provide good quality measurements with low background. We present generic neutron guides of short and medium length instruments which are optimised for good performance at minimal cost. Direct line of sight to the source is avoided twice, with either the first point out of line of sight or both being inside the bunker (20 m) to minimise shielding costs. These guide geometries are regarded as a baseline to define standards for instruments to be constructed at ESS. They are used to find commonalities and develop principles and solutions for common problems. Lastly, we report the impact of employing the over-illumination concept to mitigate losses from random misalignment passively, and that over-illumination should be used sparingly in key locations to be effective. For more widespread alignment issues, a more direct, active approach is likely to be needed.

Dose profile modeling of Idaho National Laboratory's active neutron interrogation laboratory.

PubMed

Chichester, D L; Seabury, E H; Zabriskie, J M; Wharton, J; Caffrey, A J

2009-06-01

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium-tritium (DT) fusion (14.1 MeV) neutron generators (2 x 10(8) n/s), deuterium-deuterium (DD) fusion (2.5 MeV) neutron generators (1 x 10(7) n/s), and (252)Cf spontaneous fission neutron sources (6.96 x 10(7) n/s, 30 microg). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for (252)Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield walls and entrance mazes and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

Cavitation damage prediction for spallation target vessels by assessment of acoustic vibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Futakawa, Masatoshi; Kogawa, Hiroyuki; Hasegawa, Shoichi

2008-01-01

Liquid-mercury target systems for MW-class spallation neutron sources are being developed around the world. Proton beams are used to induce the spallation reaction. At the moment the proton beam hits the target, pressure waves are generated in the mercury because of the abrupt heat deposition. The pressure waves interact with the target vessel leading to negative pressure that may cause cavitation along the vessel wall. In order to estimate the cavitation erosion, i.e. the pitting damage formed by the collapse of cavitation bubbles, off-beam tests were performed by using an electric magnetic impact testing machine (MIMTM), which can impose equivalentmore » pressure pulses in mercury. The damage potential was defined based on the relationship between the pitting damage and the time-integrated acoustic vibration induced by impact due to the bubble collapses. Additionally, the damage potential was measured in on-beam tests carried out by using the proton beam at WNR (Weapons Neutron Research) facility in Los Alamos Neutron Science Center (LANSCE). In this paper, the concept of the damage potential, the relationship between the pitting damage formation and the damage potential both in off-beam and on-beam tests is shown.« less

Thermohydraulic behavior of the liquid metal target of a spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takeda, Y.

1996-06-01

The author presents work done on three main problems. (1) Natural circulation in double coaxial cylindircal container: The thermohydraulic behaviour of the liquid metal target of the spallation neutron source at PSI has been investigated. The configuration is a natural-circulation loop in a concentric double-tube-type container. The results show that the natural-circulation loop concept is valid for the design phase of the target construction, and the current specified design criteria will be fulfilled with the proposed parameter values. (2) Flow around the window: Water experiments were performed for geometry optimisation of the window shape of the SINQ container for avoidingmore » generating recirculation zones at peripheral area and the optimal cooling of the central part of the beam entrance window. Flow visualisation technique was mainly used for various window shapes, gap distance between the window and the guide tube edge. (3) Flow in window cooling channels: Flows in narrow gaps of cooling channels of two different types of windows were studied by flow visualisation techniques. One type is a slightly curved round cooling channel and the other is hemispherical shape, both of which have only 2 mm gap distance and the water inlet is located on one side and flows out from the opposite side. In both cases, the central part of the flow area has lower velocity than peripheral area.« less

Evaluation of Side Stream Filtration Technology at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boyd, Brian K.

2014-08-01

This technology evaluation was performed by Pacific Northwest National Laboratory and Oak Ridge National Laboratory on behalf of the Federal Energy Management Program. The objective was to quantify the benefits side stream filtration provides to a cooling tower system. The evaluation assessed the performance of an existing side stream filtration system at a cooling tower system at Oak Ridge National Laboratory’s Spallation Neutron Source research facility. This location was selected because it offered the opportunity for a side-by-side comparison of a system featuring side stream filtration and an unfiltered system.

Impedance measurements of the extraction kicker system for the rapid cycling synchrotron of China Spallation Neutron Source

NASA Astrophysics Data System (ADS)

Huang, Liang-Sheng; Wang, Sheng; Liu, Yu-Dong; Li, Yong; Liu, Ren-Hong; Xiao, Ou-Zheng

2016-04-01

The fast extraction kicker system is one of the most important accelerator components and the main source of impedance in the Rapid Cycling Synchrotron of the China Spallation Neutron Source. It is necessary to understand the kicker impedance before its installation into the tunnel. Conventional and improved wire methods are employed in the impedance measurement. The experimental results for the kicker impedance are explained by comparison with simulation using CST PARTICLE STUDIO. The simulation and measurement results confirm that the window-frame ferrite geometry and the end plate are the important structures causing coupling impedance. It is proved in the measurements that the mismatching from the power form network to the kicker leads to a serious oscillation sideband of the longitudinal and vertical impedance and the oscillation can be reduced by ferrite absorbing material. Supported by National Natural Science Foundation of China (11175193, 11275221)

EDITORIAL: Instrumentation and Methods for Neutron Scattering—papers from the 4th European Conference on Neutron Scattering in Lund, Sweden, June 2007

NASA Astrophysics Data System (ADS)

Rennie, Adrian R.

2008-03-01

Neutron scattering is used as a tool to study problems in disciplines that include chemistry, materials science, biology and condensed matter physics as well as problems from neighbouring disciplines such as geology, environmental sciences and archaeology. Equipment for these studies is found at laboratories with research reactors or spallation neutron sources and there are many recent or current developments with new instruments and even entirely new facilities such as the Spallation Neutron Source at Oak Ridge, USA, the OPAL reactor at Lucas Heights, Australia and the second target station at the ISIS facility in the UK. Design and optimization of the instruments at these facilities involves work with many research laboratories and groups in universities. Every four years the European Conference on Neutron Scattering (ECNS) brings together both the specialists in neutron instrumentation and the community of users (in intervening years there are International and American conferences). In June 2007 about 700 delegates came to the 4th ECNS that was held in Lund, Sweden. There were more than 600 presentations as talks and posters. The opportunity to publish papers in Measurement Science and Technology that relate to neutron scattering instrumentation and method development was offered to the participants, and the papers that follow describe some of the recent activity in this field. Accounts of work on condensed matter science and the applications of neutron scattering appear separately in Journal of Physics: Condensed Matter. There are, of course, many features of neutron instrumentation that are specific to this particular field of measurement. However, there are also many elements of apparatus and experiment design that can usefully be shared with a broader community. It is hoped that this issue with papers from ECNS will find a broad community of interest. Apart from descriptions of overall design of diffractometers and spectrometers there are accounts of new

Simulation of a suite of generic long-pulse neutron instruments to optimize the time structure of the European Spallation Source.

PubMed

Lefmann, Kim; Klenø, Kaspar H; Birk, Jonas Okkels; Hansen, Britt R; Holm, Sonja L; Knudsen, Erik; Lieutenant, Klaus; von Moos, Lars; Sales, Morten; Willendrup, Peter K; Andersen, Ken H

2013-05-01

We here describe the result of simulations of 15 generic neutron instruments for the long-pulsed European Spallation Source. All instruments have been simulated for 20 different settings of the source time structure, corresponding to pulse lengths between 1 ms and 2 ms; and repetition frequencies between 10 Hz and 25 Hz. The relative change in performance with time structure is given for each instrument, and an unweighted average is calculated. The performance of the instrument suite is proportional to (a) the peak flux and (b) the duty cycle to a power of approximately 0.3. This information is an important input to determining the best accelerator parameters. In addition, we find that in our simple guide systems, most neutrons reaching the sample originate from the central 3-5 cm of the moderator. This result can be used as an input in later optimization of the moderator design. We discuss the relevance and validity of defining a single figure-of-merit for a full facility and compare with evaluations of the individual instrument classes.

Neutron Focusing Mirrors for Neutron Radiography of Irradiated Nuclear Fuel at Idaho National Laboratory

NASA Astrophysics Data System (ADS)

Rai, Durgesh K.; Wu, Huarui; Abir, Muhammad; Giglio, Jeffrey; Khaykovich, Boris

Post irradiation examination (PIE) of samples irradiated in nuclear reactors is a challenging but necessary task for the development on novel nuclear power reactors. Idaho National Laboratory (INL) has neutron radiography capabilities, which are especially useful for the PIE of irradiated nuclear fuel. These capabilities are limited due to the extremely high gamma-ray radiation from the irradiated fuel, which precludes the use of standard digital detectors, in turn limiting the ability to do tomography and driving the cost of the measurements. In addition, the small 250 kW Neutron Radiography Reactor (NRAD) provides a relatively weak neutron flux, which leads to low signal-to-noise ratio. In this work, we develop neutron focusing optics suitable for the installation at NRAD. The optics would separate the sample and the detector, potentially allowing for the use of digital radiography detectors, and would provide significant intensity enhancement as well. The optics consist of several coaxial nested Wolter mirrors and is suited for polychromatic thermal neutron radiation. Laboratory Directed Research and Development program of Idaho National Laboratory.

Simulation of a beam rotation system for a spallation source

NASA Astrophysics Data System (ADS)

Reiss, Tibor; Reggiani, Davide; Seidel, Mike; Talanov, Vadim; Wohlmuther, Michael

2015-04-01

With a nominal beam power of nearly 1 MW on target, the Swiss Spallation Neutron Source (SINQ), ranks among the world's most powerful spallation neutron sources. The proton beam transport to the SINQ target is carried out exclusively by means of linear magnetic elements. In the transport line to SINQ the beam is scattered in two meson production targets and as a consequence, at the SINQ target entrance the beam shape can be described by Gaussian distributions in transverse x and y directions with tails cut short by collimators. This leads to a highly nonuniform power distribution inside the SINQ target, giving rise to thermal and mechanical stresses. In view of a future proton beam intensity upgrade, the possibility of homogenizing the beam distribution by means of a fast beam rotation system is currently under investigation. Important aspects which need to be studied are the impact of a rotating proton beam on the resulting neutron spectra, spatial flux distributions and additional—previously not present—proton losses causing unwanted activation of accelerator components. Hence a new source description method was developed for the radiation transport code MCNPX. This new feature makes direct use of the results from the proton beam optics code TURTLE. Its advantage to existing MCNPX source options is that all phase space information and correlations of each primary beam particle computed with TURTLE are preserved and transferred to MCNPX. Simulations of the different beam distributions together with their consequences in terms of neutron production are presented in this publication. Additionally, a detailed description of the coupling method between TURTLE and MCNPX is provided.

Towards neutron scattering experiments with sub-millisecond time resolution

DOE PAGES

Adlmann, F. A.; Gutfreund, Phillip; Ankner, John Francis; ...

2015-02-01

Neutron scattering techniques offer several unique opportunities in materials research. However, most neutron scattering experiments suffer from the limited flux available at current facilities. This limitation becomes even more severe if time-resolved or kinetic experiments are performed. A new method has been developed which overcomes these limitations when a reversible process is studied, without any compromise on resolution or beam intensity. We demonstrate that, by recording in absolute time the neutron detector events linked to an excitation, information can be resolved on sub-millisecond timescales. Specifically, the concept of the method is demonstrated by neutron reflectivity measurements in time-of-flight mode atmore » the Liquids Reflectometer located at the Spallation Neutron Source, Oak Ridge National Laboratory, Tennessee, USA, combined with in situ rheometry. Finally, the opportunities and limitations of this new technique are evaluated by investigations of a micellar polymer solution offering excellent scattering contrast combined with high sensitivity to shear.« less

New sources and instrumentation for neutron science

NASA Astrophysics Data System (ADS)

Gil, Alina

2011-04-01

Neutron-scattering research has a lot to do with our everyday lives. Things like medicine, food, electronics, cars and airplanes have all been improved by neutron-scattering research. Neutron research also helps scientists improve materials used in a multitude of different products, such as high-temperature superconductors, powerful lightweight magnets, stronger, lighter plastic products etc. Neutron scattering is one of the most effective ways to obtain information on both, the structure and the dynamics of condensed matter. Most of the world's neutron sources were built decades ago, and although the uses and demand for neutrons have increased throughout the years, few new sources have been built. The new construction, accelerator-based neutron source, the spallation source will provide the most intense pulsed neutron beams in the world for scientific research and industrial development. In this paper it will be described what neutrons are and what unique properties make them useful for science, how spallation source is designed to produce neutron beams and the experimental instruments that will use those beams. Finally, it will be described how past neutron research has affected our everyday lives and what we might expect from the most exciting future applications.

Neutron Reflectometry and Small Angle Neutron Scattering of ABC Miktoarm Terpolymer Thin-Films

NASA Astrophysics Data System (ADS)

Arras, Matthias M. L.; Wang, Weiyu; Mahalik, Jyoti P.; Hong, Kunlun; Sumpter, Bobby G.; Smith, Gregory S.; Chernyy, Sergey; Kim, Hyeyoung; Russell, Thomas P.

Due to the constraint of the junction point in miktoarm terpolymers, where three chains meet, ABC miktoarm terpolymers are promising to obtain nanostructured, long-range ordered materials. We present details of the thin-film structure of ABC miktoarm terpolymers in the poly(styrene), poly(isoprene), poly(2-vinylpyridine) (PS-PI-P2VP) system, investigated by neutron reflectometry and small angle neutron scattering. To this end, we synthesized partially deuterated versions of the PS-PI-P2VP and investigated annealed samples, spin-coated to various thicknesses of the bulk repeat period. Furthermore, we investigated the structural change upon selective blending with homopolymers or fullerenes. We find that thin-film constraints on the morphology can vanish after only twice the repetition period. In addition, it is indicated that nanoparticles improve the ordering in these systems, however, this seems to be not necessarily true for homopolymer blending. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

H- radio frequency source development at the Spallation Neutron Source.

PubMed

Welton, R F; Dudnikov, V G; Gawne, K R; Han, B X; Murray, S N; Pennisi, T R; Roseberry, R T; Santana, M; Stockli, M P; Turvey, M W

2012-02-01

The Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability of ∼90%. H(-) beam pulses (∼1 ms, 60 Hz) are produced by a Cs-enhanced, multicusp ion source closely coupled with an electrostatic low energy beam transport (LEBT), which focuses the 65 kV beam into a radio frequency quadrupole accelerator. The source plasma is generated by RF excitation (2 MHz, ∼60 kW) of a copper antenna that has been encased with a thickness of ∼0.7 mm of porcelain enamel and immersed into the plasma chamber. The ion source and LEBT normally have a combined availability of ∼99%. Recent increases in duty-factor and RF power have made antenna failures a leading cause of downtime. This report first identifies the physical mechanism of antenna failure from a statistical inspection of ∼75 antennas which ran at the SNS, scanning electron microscopy studies of antenna surface, and cross sectional cuts and analysis of calorimetric heating measurements. Failure mitigation efforts are then described which include modifying the antenna geometry and our acceptance∕installation criteria. Progress and status of the development of the SNS external antenna source, a long-term solution to the internal antenna problem, are then discussed. Currently, this source is capable of delivering comparable beam currents to the baseline source to the SNS and, an earlier version, has briefly demonstrated unanalyzed currents up to ∼100 mA (1 ms, 60 Hz) on the test stand. In particular, this paper discusses plasma ignition (dc and RF plasma guns), antenna reliability, magnet overheating, and insufficient beam persistence.

Determination of the ¹⁴C content in activated steel components from a neutron spallation source and a nuclear power plant.

PubMed

Schumann, Dorothea; Stowasser, Tanja; Volmert, Benjamin; Günther-Leopold, Ines; Linder, Hanspeter; Wieland, Erich

2014-06-03

The (14)C content in activated steel components from the Swiss Nuclear Power Plant (NPP) Gösgen and the Spallation Neutron Source SINQ at the Paul Scherrer Institute is determined using a wet chemistry digestion technique and liquid scintillation counting for (14)C activity measurements. The (14)C activity of an activated fuel assembly steel nut from the NPP is further compared with theoretical predictions made on the basis of a Monte Carlo reactor model for this NPP. Knowledge of the (14)C inventory in these activated steel materials is important in conjunction with future corrosion studies on these materials aimed at identifying the (14)C containing organic compounds possibly formed in the cement-based near field of a repository for radioactive waste.

Effects of environment and frequency on the fatigue behavior of the spallation neutron source (SNS) target container material - 316 LN stainless steel

NASA Astrophysics Data System (ADS)

Tian, Hongbo

As the candidate target container material of the new Spallation Neutron Source (SNS) being designed and constructed at the Oak Ridge National Laboratory (ORNL), Type 316 low-carbon nitrogen-added (LN) stainless steel (SS) will operate in an aggressive environment, subjected to intense fluxes of high-energy protons and neutrons while exposed to liquid mercury. The current project is oriented toward materials studies regarding the effects of test environment and frequency on the fatigue behavior of 316 LN SS. In order to study the structural applications of this material and improve the fundamental understanding of the fatigue damage mechanisms, fatigue tests were performed in air and mercury environments at various frequencies and R ratios (R = sigma min/sigmamax, sigmamin and sigmamax are the applied minimum and maximum stresses, respectively). Fatigue data were developed for the structural design and engineering applications of this material. Specifically, high-cycle fatigue tests, fatigue crack-propagation tests, and ultrahigh cycle fatigue tests up to 10 9 cycles were conducted in air and mercury with test frequencies from 10 Hz to 700 Hz. Microstructure characterizations were performed using optical microscopy (OM), scanning-electron microscopy (SEM), and transmission-electron microscopy (TEM). It was found that mercury doesn't seem to have a large impact on the crack-initiation behavior of 316 LN SS. However, the crack-propagation mechanisms in air and mercury are different in some test conditions. Transgranular cracks seem to be the main mechanism in air, and intergranular in mercury. A significant specimen self-heating effect was found during high-cycle faituge. Theoretical calculation was performed to predict temperature responses of the material subjected to cyclic deformation. The predicted cyclic temperature evolution seems to be in good agreement with the experimental results.

Neutron stars: A cosmic hadron physics laboratory

NASA Technical Reports Server (NTRS)

Pines, David

1989-01-01

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

Attempt to Measure (n, xn) Double-Differential Cross Sections for Incident Neutron Energies above 100 MeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, T.; Kunieda, S.; Shigyo, N.

The experimental technique for measurement of (n, xn) double differential cross sections for incident neutron energy above 100 MeV has been attempted to be developed with continuous-energy neutrons up to 400 MeV. Neutrons were produced in the spallation reaction by the 800 MeV proton beam, which was incident on a thick, heavily shielded tungsten target at the WNR facility at Los Alamos National Laboratory. The energies of incident neutrons were determined by the time-of-flight method. Emitted neutrons were detected by the recoil proton method. A phoswich detector consisting of NaI(Tl) and NE102A plastic scintillators was used for detecting recoil protons.more » We compared the preliminary experimental cross section data with the calculations by PHITS and QMD codes.« less

Testing Single Phase IGBT H-Bridge Switch Plates for the High Voltage Converter Modulator at the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peplov, Vladimir V; Anderson, David E; Solley, Dennis J

2014-01-01

Three IGBT H-bridge switching networks are used in each High Voltage Converter Modulator (HVCM) system at the Spallation Neutron Source (SNS) to generate drive currents to three boost transformer primaries switching between positive and negative bus voltages at 20 kHz. Every switch plate assembly is tested before installing it into an operational HVCM. A Single Phase Test Stand has been built for this purpose, and it is used for adjustment, measurement and testing of different configurations of switch plates. This paper will present a description of the Test Stand configuration and discuss the results of testing switch plates with twomore » different types of IGBT gate drivers currently in use on the HVCM systems. Comparison of timing characteristics of the original and new drivers and the resulting performance reinforces the necessity to replace the original H-bridge network drivers with the upgraded units.« less

Thermal neutron radiative capture on cadmium as a counting technique at the INES beam line at ISIS: A preliminary investigation of detector cross-talk.

PubMed

Festa, G; Grazzi, F; Pietropaolo, A; Scherillo, A; Schooneveld, E M

2017-12-01

Experimental tests are presented that assess the cross-talk level among three scintillation detectors used as neutron counters exploiting the thermal neutron radiative capture on Cd. The measurements were done at the INES diffractometer operating at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK). These tests follow a preliminary set of measurements performed on the same instrument to study the effectiveness of this thermal neutron counting strategy in neutron diffraction measurements, typically performed on INES using squashed 3 He filled gas tubes. The experimental data were collected in two different geometrical configurations of the detectors and compared to results of Monte Carlo simulations, performed using the MCNP code. Copyright © 2017 Elsevier Ltd. All rights reserved.

The thermal triple-axis-spectrometer EIGER at the continuous spallation source SINQ

NASA Astrophysics Data System (ADS)

Stuhr, U.; Roessli, B.; Gvasaliya, S.; Rønnow, H. M.; Filges, U.; Graf, D.; Bollhalder, A.; Hohl, D.; Bürge, R.; Schild, M.; Holitzner, L.; Kaegi, C.,; Keller, P.; Mühlebach, T.

2017-05-01

EIGER is the new thermal triple-axis-spectrometer at the continuous spallation SINQ at PSI. The shielding of the monochromator consists only of non- or low magnetizable materials, which allows the use of strong magnetic fields with the instrument. This shielding reduces the high energy neutron contamination to a comparable level of thermal spectrometers at reactor sources. The instrument design, the performance and first results of the spectrometer are presented.

Possibility of a crossed-beam experiment involving slow-neutron capture by unstable nuclei - ``rapid-process tron''

NASA Astrophysics Data System (ADS)

Yamazaki, T.; Katayama, I.; Uwamino, Y.

1993-02-01

The possibility of a crossed beam facility of slow neutrons capturing unstable nuclei is examined in connection with the Japanese Hadron Project. With a pulsed proton beam of 50 Hz repetition and with a 100 μA average beam current, one obtains a spallation neutron source of 2.4 × 10 8 thermal neutrons/cm 3/spill over a 60 cm length with a 3 ms average duration time by using a D 2O moderator. By confining radioactive nuclei of 10 9 ions in a beam circulation ring of 0.3 MHz revolution frequency, so that nuclei pass through the neutron source, one obtains a collision luminosity of 3.9 × 10 24/cm 2/s. A new research domain aimed at studying rapid processes in nuclear genetics in a laboratory will be created.

In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory

DOE PAGES

Conrad, P. G.; Malespin, C. A.; Franz, H. B.; ...

2016-11-01

Mars Science Laboratory's Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking mission's krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. But, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stablemore » isotopes, unmeasured by Viking. Our new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, but, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.« less

In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory

NASA Astrophysics Data System (ADS)

Conrad, P. G.; Malespin, C. A.; Franz, H. B.; Pepin, R. O.; Trainer, M. G.; Schwenzer, S. P.; Atreya, S. K.; Freissinet, C.; Jones, J. H.; Manning, H.; Owen, T.; Pavlov, A. A.; Wiens, R. C.; Wong, M. H.; Mahaffy, P. R.

2016-11-01

Mars Science Laboratory's Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking mission's krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. However, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stable isotopes, unmeasured by Viking. The new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, however, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.

In Situ Measurement of Atmospheric Krypton and Xenon on Mars with Mars Science Laboratory

NASA Technical Reports Server (NTRS)

Conrad, P. G.; Malespin, C. A.; Franz, H. B.; Pepin, R. O.; Trainer, M. G.; Schwenzer, S. P.; Atreya, S. K.; Freissinet, C.; Jones, J. H.; Manning, H.;

In situ measurement of atmospheric krypton and xenon on Mars with Mars Science Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Conrad, P. G.; Malespin, C. A.; Franz, H. B.

Mars Science Laboratory's Sample Analysis at Mars (SAM) investigation has measured all of the stable isotopes of the heavy noble gases krypton and xenon in the martian atmosphere, in situ, from the Curiosity Rover at Gale Crater, Mars. Previous knowledge of martian atmospheric krypton and xenon isotope ratios has been based upon a combination of the Viking mission's krypton and xenon detections and measurements of noble gas isotope ratios in martian meteorites. But, the meteorite measurements reveal an impure mixture of atmospheric, mantle, and spallation contributions. The xenon and krypton isotopic measurements reported here include the complete set of stablemore » isotopes, unmeasured by Viking. Our new results generally agree with Mars meteorite measurements but also provide a unique opportunity to identify various non-atmospheric heavy noble gas components in the meteorites. Kr isotopic measurements define a solar-like atmospheric composition, but deviating from the solar wind pattern at 80Kr and 82Kr in a manner consistent with contributions originating from neutron capture in Br. The Xe measurements suggest an intriguing possibility that isotopes lighter than 132Xe have been enriched to varying degrees by spallation and neutron capture products degassed to the atmosphere from the regolith, and a model is constructed to explore this possibility. Such a spallation component, but, is not apparent in atmospheric Xe trapped in the glassy phases of martian meteorites.« less

Thermal hydraulic design and decay heat removal of a solid target for a spallation neutron source

NASA Astrophysics Data System (ADS)

Takenaka, N.; Nio, D.; Kiyanagi, Y.; Mishima, K.; Kawai, M.; Furusaka, M.

2005-08-01

Thermal hydraulic design and thermal stress calculations were conducted for a water-cooled solid target irradiated by a MW-class proton beam for a spallation neutron source. Plate type and rod bundle type targets were examined. The thickness of the plate and the diameter of the rod were determined based on the maximum and the wall surface temperature. The thermal stress distributions were calculated by a finite element method (FEM). The neutronics performance of the target is roughly proportional to its average density. The averaged densities of the designed targets were calculated for tungsten plates, tantalum clad tungsten plates, tungsten rods sheathed by tantalum and Zircaloy and they were compared with mercury density. It was shown that the averaged density was highest for the tungsten plates and was high for the tantalum cladding tungsten plates, the tungsten rods sheathed by tantalum and Zircaloy in order. They were higher than or equal to that of mercury for the 1 2 MW proton beams. Tungsten target without the cladding or the sheath is not practical due to corrosion by water under irradiation condition. Therefore, the tantalum cladding tungsten plate already made successfully by HIP and the sheathed tungsten rod are the candidate of high performance solid targets. The decay heat of each target was calculated. It was low enough low compared to that of ISIS for the target without tantalum but was about four times as high as that of ISIS when the thickness of the tantalum cladding was 0.5 mm. Heat removal methods of the decay heat with tantalum were examined. It was shown that a special cooling system was required for the target exchange when tantalum was used for the target. It was concluded that the tungsten rod target sheathed with stainless steel or Zircaloy was the most reliable from the safety considerations and had similar neutronics performance to that of mercury.

Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

G. Ciovati, P. Kneisel , J. Brawley, R. Bundy, I. Campisi, K. Davis; K. Macha; D. Machie

2001-09-01

The Spallation Neutron Source project includes a superconducting linac section in the energy range from 192 MeV to 1000 MeV, operating at a frequency of 805 MHz at 2.1 K. For this energy range two types of cavities are needed with geometrical beta - values of beta= 0.61 and beta= 0.81. An aggressive cavity prototyping program is being pursued at Jlab, which calls for fabricating and testing of four beta= 0.61 cavities and two beta= 0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler on each beam pipe and a portmore » for a high power coaxial input coupler. Three of the four beta= 0.61 cavities will be used for a cryomodule test in early 2002. At this time four medium beta cavities and one high beta cavity have been completed at JLab. The first tests on the beta=0.61 cavity and the beta= 0.81 exceeded the design values for gradient and Q - value: E{sub acc} = 1 0.3 MV/m and Q = 5 x 10{sup 9} at 2.1K for beta= 0.61 and E{sub acc} = 12.3 MV/m and Q = 5 x 10{sup 9} at 2.1K for beta= 0.81. One of the medium beta cavities has been equipped with an integrated helium vessel and measurements of the static and dynamic Lorentz force detuning will be done and compared to the ''bare'' cavities. In addition two single cell cavities have been fabricated, equipped with welded-on HOM couplers. They are being used to evaluate the HOM couplers with respect to multipacting, fundamental mode rejection and HOM damping as far as possible in a single cell. This paper will describe the cavity design with respect to electrical and mechanical features, the fabrication efforts and the results obtained with the different cavities existing at the time of this workshop.« less

Superconducting Prototype Cavities for the Spallation Neutron Source (SNS) Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

G. Ciovati; P. Kneisel; K. Davis

2002-06-01

The Spallation Neutron Source project includes a superconducting linac section in the energy range from 186 MeV to 1000 MeV operating at a frequency of 805 MHz at 2.1 K. For this energy range two types of cavities are needed with geometrical Beta-values of Beta=0.61 and Beta=0.81. An aggressive cavity prototyping program is being pursued at JLab, which calls for fabricating and testing of four Beta=0.61 cavities and two Beta=0.81 cavities. Both types consist of six cells made from high purity niobium and feature one HOM coupler of the TESLA type on each beam pipe and a port for amore » high power coaxial input coupler. Three of the four Beta=0.61 cavities will be used for a cryomodule test in early 2002. At this time, four medium beta cavities and one high beta cavity have been completed and tested at JLab. In addition, the three medium beta cavities for the prototype cryomodule have been equipped with the integrated Ti-Helium vessel, successfully retested and will be assembled into a cavity string. Results from the cryo-module test should be available by the time of the conference. The tests on the Beta=0.61 cavity and the Beta=0.81 cavity exceeded the design values for gradient and Q - value: E{sub acc} =10.1 MV/m and Q = 5 x 10{sup 9} at 2.1K for Beta=0.61 and E{sub acc} = 12.3 MV/m and Q=5 x 10{sup 9} at 2.1K for Beta = 0.81. The medium beta cavities reached gradients between E{sub acc} = 15 MV/m and 21 MV/m. This paper will describe the test results obtained with the various cavities, some aspects of the HOM damping at cryogenic temperatures, results from microphonics and Lorentz force detuning tests and the cavity string assembly at the time of this workshop.« less

Moisture-Induced TBC Spallation on Turbine Blade Samples

NASA Technical Reports Server (NTRS)

Smialek, James L.

2011-01-01

Delayed failure of TBCs is a widely observed laboratory phenomenon, although many of the early observations went unreported. "The weekend effect" or "DeskTop Spallation" (DTS) is characterized by initial survival of a TBC after accelerated laboratory thermal cycling, then failure by exposure to ambient humidity or water. Once initiated, failure can occur quite dramatically in less than a second. To this end, the water drop test and digital video recordings have become useful techniques in studies at NASA (Smialek, Zhu, Cuy), DECHMA (Rudolphi, Renusch, Schuetze), and CNRS Toulouse/SNECMA (Deneux, Cadoret, Hervier, Monceau). In the present study the results for a commercial turbine blade, with a standard EB-PVD 7YSZ TBC top coat and Pt-aluminide diffusion bond monitored by weight change and visual appearance. Failures were distributed widely over a 5-100 hr time range, depending on temperature. At some opportune times, failure was captured by video recording, documenting the appearance and speed of the moisture-induced spallation process. Failure interfaces exhibited alumina scale grains, decorated with Ta-rich oxide particles, and alumina inclusions as islands and streamers. The phenomenon is thus rooted in moisture-induced delayed spallation (MIDS) of the alumina scale formed on the bond coat. In that regard, many studies show the susceptibility of alumina scales to moisture, as long as high strain energy and a partially exposed interface exist. The latter conditions result from severe cyclic oxidation conditions, which produce a highly stressed and partially damaged scale. In one model, it has been proposed that moisture reacts with aluminum in the bond coat to release hydrogen atoms that 'embrittle' the interface. A negative synergistic effect with interfacial sulfur is also invoked.

Measurement of Continuous-Energy Neutron-Incident Neutron-Production Cross Section

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shigyo, Nobuhiro; Kunieda, Satoshi; Watanabe, Takehito

Continuous energy neutron-incident neutron-production double differential cross sections were measured at the Weapons Neutron Research (WNR) facility of the Los Alamos Neutron Science Center. The energy of emitted neutrons was derived from the energy deposition in a detector. The incident-neutron energy was obtained by the time-of-flight method between the spallation target of WNR and the emitted neutron detector. Two types of detectors were adopted to measure the wide energy range of neutrons. The liquid organic scintillators covered up to 100 MeV. The recoil proton detectors that constitute the recoil proton radiator and phoswich type NaI (Tl) scintillators were used formore » neutrons above several tens of MeV. Iron and lead were used as sample materials. The experimental data were compared with the evaluated nuclear data, the results of GNASH, JQMD, and PHITS codes.« less

Neutron production for 250 MeV protons bombarding on thick grain-made tungsten target

NASA Astrophysics Data System (ADS)

Zhang, Xueying; Zhang, Yanbin; Ma, Fei; Ju, Yongqin; Chen, Liang; Zhang, Hongbin; Li, Yanyan; Wan, Bo; Wang, Jianguo; Ge, Honglin

2015-08-01

Neutron yield for 250 MeV protons incident on a tungsten target has been measured using the water bath method. The target was made of many randomly placed tungsten grains. Through analyzing the activity of Au foils, the neutron flux distribution in water was obtained. The neutrons slowing down process shows that the neutrons from tungsten have an average energy lower than neutrons from the lead target. The neutron yield was experimentally determined to be 2.02 ± 0.15 neutron/proton. Detailed simulation was also performed with the Geant4 toolkit. Comparison has been made with the experimentally derived neutron yield. It was found that, around 250 MeV, experimental results were described satisfactorily with a combination of high-energy spallation, low-energy neutron reaction and scattering. It was shown that the grain-packed target does not affect much the main neutronic properties, which are of crucial importance for the design of the spallation target.

Compatibility of photomultiplier tube operation with SQUIDs for a neutron EDM experiment

NASA Astrophysics Data System (ADS)

Libersky, Matthew; nEDM Collaboration

2013-10-01

An experiment at the Spallation Neutron Source at Oak Ridge National Laboratory with the goal of reducing the experimental limit on the electric dipole moment (EDM) of the neutron will measure the precession frequencies of neutrons when a strong electric field is applied parallel and anti-parallel to a weak magnetic field. A difference in these frequencies would indicate a nonzero neutron EDM. To correct for drifts of the magnetic field in the measurement volume, polarized 3He will be used as a co-magnetometer. In one of the two methods built into the apparatus, superconducting quantum interference devices (SQUIDs) will be used to read out the 3He magnetization. Photomultiplier tubes will be used concurrently to measure scintillation light from neutron capture by 3He. However, the simultaneous noise-sensitive magnetic field measurement by the SQUIDs makes conventional PMT operation problematic due to the alternating current involved in generating the high voltages needed. Tests were carried out at Los Alamos National Laboratory to study the compatibility of simultaneous SQUID and PMT operation, using a custom battery-powered high-voltage power supply developed by Meyer and Smith (NIM A 647.1) to operate the PMT. The results of these tests will be presented.

Feasibility and applications of the spin-echo modulation option for a small angle neutron scattering instrument at the European Spallation Source

NASA Astrophysics Data System (ADS)

Kusmin, A.; Bouwman, W. G.; van Well, A. A.; Pappas, C.

2017-06-01

We describe theoretical and practical aspects of spin-echo modulated small-angle neutron scattering (SEMSANS) as well as the potential combination with SANS. Based on the preliminary technical designs of SKADI (a SANS instrument proposed for the European Spallation Source) and a SEMSANS add-on, we assess the practicability, feasibility and scientific merit of a combined SANS and SEMSANS setup by calculating tentative SANS and SEMSANS results for soft matter, geology and advanced material samples that have been previously studied by scattering methods. We conclude that lengths from 1 nm up to 0.01 mm can be observed simultaneously in a single measurement. Thus, the combination of SANS and SEMSANS instrument is suited for the simultaneous observation of a wide range of length scales, e.g. for time-resolved studies of kinetic processes in complex multiscale systems.

The performance of the upgraded Los Alamos Neutron Source

NASA Astrophysics Data System (ADS)

Ito, Takeyasu; LANL UCN Source Collaboration

2017-09-01

Los Alamos National Laboratory has been operating an ultracold (UCN) source based on a solid deuterium (SD2) UCN converter driven by spallation neutrons for over 10 years. It has recently been successfully upgraded, by replacing the cryostat that contains the cold neutron moderator, SD2 volume, and vertical UCN guide. The horizontal UCN guide that transports UCN out of the radiation shield was also replaced. The new design reflects lessons learned from the 10+ year long operation of the previous version of the UCN source and is optimized to maximize the cold neutron flux at the SD2 volume, featuring a close coupled cold neutron moderator, and maximize the transport of the UCN to experiments. During the commissioning of the upgraded UCN source, data were collected to measure its performance, including cold neutron spectra as a function of the cold moderator temperature, and the UCN density in a vessel outside the source. In this talk, after a brief overview of the design of the upgraded source, the results of the performance tests and comparison to prediction will be presented. This work was funded by LANL LDRD.

Energy deposition calculated by PHITS code in Pb spallation target

NASA Astrophysics Data System (ADS)

Yu, Quanzhi

2016-01-01

Energy deposition in a Pb spallation target irradiated by high energetic protons was calculated by PHITS2.52 code. The validation of the energy deposition and neutron production calculated by PHITS code was performed. Results show good agreements between the simulation results and the experimental data. Detailed comparison shows that for the total energy deposition, PHITS simulation result was about 15% overestimation than that of the experimental data. For the energy deposition along the length of the Pb target, the discrepancy mainly presented at the front part of the Pb target. Calculation indicates that most of the energy deposition comes from the ionizations of the primary protons and the produced secondary particles. With the event generator mode of PHITS, the deposit energy distribution for the particles and the light nulclei is presented for the first time. It indicates that the primary protons with energy more than 100 MeV are the most contributors to the total energy deposition. The energy depositions peaking at 10 MeV and 0.1 MeV, are mainly caused by the electrons, pions, d, t, 3He and also α particles during the cascade process and the evaporation process, respectively. The energy deposition density caused by different proton beam profiles are also calculated and compared. Such calculation and analyses are much helpful for better understanding the physical mechanism of energy deposition in the spallation target, and greatly useful for the thermal hydraulic design of the spallation target.

Moisture-Induced TBC Spallation on Turbine Blade Samples

NASA Technical Reports Server (NTRS)

Smialek, James

2011-01-01

Delayed failure of TBCs is a widely observed laboratory phenomenon, although many of the early observations went unreported. The weekend effect or DeskTop Spallation (DTS) is characterized by initial survival of a TBC after accelerated laboratory thermal cycling, then failure by exposure to ambient humidity or water. Once initiated, failure can occur quite dramatically in less than a second. To this end, the water drop test and digital video recordings have become useful techniques in studies at NASA (Smialek, Zhu, Cuy), DECHMA (Rudolphi, Renusch, Schuetze), and CNRS Toulouse/SNECMA (Deneux, Cadoret, Hervier, Monceau). In the present study the results for a commercial turbine blade, with a standard EB-PVD 7YSZ TBC top coat and Pt-aluminide diffusion bond coat are reported. Cut sections were intermittently oxidized at 1100, 1150, and 1200 C and monitored by weight change and visual appearance. Failures were distributed widely over a 5-100 hr time range, depending on temperature. At some opportune times, failure was captured by video recording, documenting the appearance and speed of the moisture-induced spallation process. Failure interfaces exhibited alumina scale grains, decorated with Ta-rich oxide particles, and alumina inclusions as islands and streamers. The phenomenon is thus rooted in moisture-induced delayed spallation (MIDS) of the alumina scale formed on the bond coat. In that regard, many studies show the susceptibility of alumina scales to moisture, as long as high strain energy and a partially exposed interface exist. The latter conditions result from severe cyclic oxidation conditions, which produce a highly stressed and partially damaged scale. In one model, it has been proposed that moisture reacts with aluminum in the bond coat to release hydrogen atoms that embrittle the interface. A negative synergistic effect with interfacial sulfur is also invoked.

AC magnetic field measurement using a small flip coil system for rapid cycling AC magnets at the China Spallation Neutron Source (CSNS)

NASA Astrophysics Data System (ADS)

Zhou, Jianxin; Kang, Wen; Li, Shuai; Liu, Yudong; Liu, Yiqin; Xu, Shouyan; Guo, Xiaoling; Wu, Xi; Deng, Changdong; Li, Li; Wu, Yuwen; Wang, Sheng

2018-02-01

The China Spallation Neutron Source (CSNS) has two major accelerator systems, a linear accelerator and a rapid cycling synchrotron (RCS). The RCS accelerator is used to accumulate and accelerate protons from the energy of 80 MeV to the design energy of 1.6 GeV at the repetition rate of 25 Hz, and extract the high energy beam to the target. The main magnets of the RCS accelerator are excited by AC current with DC bias. The magnetic field quality is very important for the RCS accelerator operation, since it should guarantee and focus a circulating beam. In order to characterize the AC magnets, a small flip coil measurement system has been developed and one of each type of AC magnets has been studied. The measurement system and selected measurement results are presented in this paper.

Aerial Neutron Detection of Cosmic-Ray Interactions with the Earth's Surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richard Maurer

2008-09-18

We have demonstrated the ability to measure the neutron flux produced by the cosmic-ray interaction with nuclei in the ground surface using aerial neutron detection. High energy cosmic-rays (primarily muons with GeV energies) interact with the nuclei in the ground surface and produce energetic neutrons via spallation. At the air-surface interface, the neutrons produced by spallation will either scatter within the surface material, become thermalized and reabsorbed, or be emitted into the air. The mean free path of energetic neutrons in air can be hundreds of feet as opposed to a few feet in dense materials. As such, the fluxmore » of neutrons escaping into the air provides a measure of the surface nuclei composition. It has been demonstrated that this effect can be measured at long range using neutron detectors on low flying helicopters. Radiological survey measurements conducted at Government Wash in Las Vegas, Nevada, have shown that the neutron background from the cosmic-soil interactions is repeatable and directly correlated to the geological data. Government Wash has a very unique geology, spanning a wide variety of nuclide mixtures and formations. The results of the preliminary measurements are presented.« less

Applications of a micro-pixel chamber (μPIC) based, time-resolved neutron imaging detector at pulsed neutron beams

NASA Astrophysics Data System (ADS)

Parker, J. D.; Harada, M.; Hattori, K.; Iwaki, S.; Kabuki, S.; Kishimoto, Y.; Kubo, H.; Kurosawa, S.; Matsuoka, Y.; Miuchi, K.; Mizumoto, T.; Nishimura, H.; Oku, T.; Sawano, T.; Shinohara, T.; Suzuki, J.-I.; Takada, A.; Tanimori, T.; Ueno, K.; Ikeno, M.; Tanaka, M.; Uchida, T.

2014-04-01

The realization of high-intensity, pulsed spallation neutron sources such as J-PARC in Japan and SNS in the US has brought time-of-flight (TOF) based neutron techniques to the fore and spurred the development of new detector technologies. When combined with high-resolution imaging, TOF-based methods become powerful tools for direct imaging of material properties, including crystal structure/internal strain, isotopic/temperature distributions, and internal and external magnetic fields. To carry out such measurements in the high-intensities and high gamma backgrounds found at spallation sources, we have developed a new time-resolved neutron imaging detector employing a micro-pattern gaseous detector known as the micro-pixel chamber (μPIC) coupled with a field-programmable-gate-array-based data acquisition system. The detector combines 100μm-level (σ) spatial and sub-μs time resolutions with low gamma sensitivity of less than 10-12 and a rate capability on the order of Mcps (mega-counts-per-second). Here, we demonstrate the application of our detector to TOF-based techniques with examples of Bragg-edge transmission and neutron resonance transmission imaging (with computed tomography) carried out at J-PARC. We also consider the direct imaging of magnetic fields with our detector using polarized neutrons.

Spallation behaviour of a Zr-bulk metallic glass

NASA Astrophysics Data System (ADS)

Ling, Z.; Huang, X.; Shen, L. T.; Dai, L. H.

2012-08-01

Plate impact experiments have been conducted on a Zr-based bulk metal glass (BMG) using a single stage light gas gun. To understand the spallation process of the material, samples were subjected to dynamic tensile loadings of the same amplitude but different durations. Fractographs of spallation surface and fracture features were characterized and the fracture mechanism of different regions of the spallation surface was discussed. Morphology of the spallation surface in the Zr-BMG exhibited a typical equiaxial cellular pattern and porous microstructure. These experiments revealed that, subjected to hydro-tensile stresses, the microdamage of the spallation occurred in the Zr-BMG is microvoids; the spallation in the Zr-BMG is resulted from nucleation, growth and coalescence of microvoids; and the time needed for these microvoids nucleation is less than 100 ns with a stress amplitude of 3.18 GPa.

A history of neutrons in biology: the development of neutron protein crystallography at BNL and LANL.

PubMed

Schoenborn, Benno P

2010-11-01

The first neutron diffraction data were collected from crystals of myoglobin almost 42 years ago using a step-scan diffractometer with a single detector. Since then, major advances have been made in neutron sources, instrumentation and data collection and analysis, and in biochemistry. Fundamental discoveries about enzyme mechanisms, biological complex structures, protein hydration and H-atom positions have been and continue to be made using neutron diffraction. The promise of neutrons has not changed since the first crystal diffraction data were collected. Today, with the developments of beamlines at spallation neutron sources and the use of the Laue method for data collection, the field of neutrons in structural biology has renewed vitality.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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

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

DOE PAGES

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

2017-02-09

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

Overview of the Neutron experimental facilities at LANSCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mocko, Michal

2016-06-30

This presentation gives an overview of the neutron experimental facilities at LANSCE. The layout is mentioned in detail, with a map of the south-side experimental facilities, information on Target-4 and the Lujan Center. Then it goes into detail about neutron sources, specifically continuous versus pulsed. Target 4 is then discussed. In conclusion, we have introduced the south-side experimental facilities in operation at LANSCE. 1L target and Target 4 provide complementary neutron energy spectra. Two spallation neutron sources taken together cover more than 11 orders of magnitude in neutron energy.

New developments in the McStas neutron instrument simulation package

NASA Astrophysics Data System (ADS)

Willendrup, P. K.; Knudsen, E. B.; Klinkby, E.; Nielsen, T.; Farhi, E.; Filges, U.; Lefmann, K.

2014-07-01

The McStas neutron ray-tracing software package is a versatile tool for building accurate simulators of neutron scattering instruments at reactors, short- and long-pulsed spallation sources such as the European Spallation Source. McStas is extensively used for design and optimization of instruments, virtual experiments, data analysis and user training. McStas was founded as a scientific, open-source collaborative code in 1997. This contribution presents the project at its current state and gives an overview of the main new developments in McStas 2.0 (December 2012) and McStas 2.1 (expected fall 2013), including many new components, component parameter uniformisation, partial loss of backward compatibility, updated source brilliance descriptions, developments toward new tools and user interfaces, web interfaces and a new method for estimating beam losses and background from neutron optics.

Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

DOE PAGES

Grammer, K. B.; Alarcon, R.; Barrón-Palos, L.; ...

2015-05-08

Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many-body physics. Unfortunately, the pair correlation function g(r) inferred from neutron scattering measurements of the differential cross section dσ/dΩ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43 and 16.1 meV on liquid hydrogen at 15.6 K (which is dominated by the parahydrogen component)more » using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1 meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra nonequilibrium component of orthohydrogen. Liquid parahydrogen is also a widely used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. Furthermore, we describe our measurements and compare them with previous work.« less

Neutron radiography of irradiated nuclear fuel at Idaho National Laboratory

DOE PAGES

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

2015-09-10

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

The HB-2D Polarized Neutron Development Beamline at the High Flux Isotope Reactor

NASA Astrophysics Data System (ADS)

Crow, Lowell; Hamilton, WA; Zhao, JK; Robertson, JL

2016-09-01

The Polarized Neutron Development beamline, recently commissioned at the HB-2D position on the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory, provides a tool for development and testing of polarizers, polarized neutron devices, and prototyping of polarized neutron techniques. With available monochromators including pyrolytic graphite and polarizing enriched Fe-57 (Si), the instrument has operated at 4.25 and 2.6 Å wavelengths, using crystal, supermirror, or He-3 polarizers and analyzers in various configurations. The Neutron Optics and Development Team has used the beamline for testing of He-3 polarizers for use at other HFIR and Spallation Neutron Source (SNS) instruments, as well as a variety of flipper devices. Recently, we have acquired new supermirror polarizers which have improved the instrument performance. The team and collaborators also have continuing demonstration experiments of spin-echo focusing techniques, and plans to conduct polarized diffraction measurements. The beamline is also used to support a growing use of polarization techniques at present and future instruments at SNS and HFIR.

Development of time projection chamber for precise neutron lifetime measurement using pulsed cold neutron beams

NASA Astrophysics Data System (ADS)

Arimoto, Y.; Higashi, N.; Igarashi, Y.; Iwashita, Y.; Ino, T.; Katayama, R.; Kitaguchi, M.; Kitahara, R.; Matsumura, H.; Mishima, K.; Nagakura, N.; Oide, H.; Otono, H.; Sakakibara, R.; Shima, T.; Shimizu, H. M.; Sugino, T.; Sumi, N.; Sumino, H.; Taketani, K.; Tanaka, G.; Tanaka, M.; Tauchi, K.; Toyoda, A.; Tomita, T.; Yamada, T.; Yamashita, S.; Yokoyama, H.; Yoshioka, T.

2015-11-01

A new time projection chamber (TPC) was developed for neutron lifetime measurement using a pulsed cold neutron spallation source at the Japan Proton Accelerator Research Complex (J-PARC). Managing considerable background events from natural sources and the beam radioactivity is a challenging aspect of this measurement. To overcome this problem, the developed TPC has unprecedented features such as the use of polyether-ether-ketone plates in the support structure and internal surfaces covered with 6Li-enriched tiles to absorb outlier neutrons. In this paper, the design and performance of the new TPC are reported in detail.

Study of proton- and deuteron-induced spallation reactions on the long-lived fission product 93Zr at 105 MeV/nucleon in inverse kinematics

NASA Astrophysics Data System (ADS)

Kawase, Shoichiro; Nakano, Keita; Watanabe, Yukinobu; Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Ahn, Deuk Soon; Aikawa, Masayuki; Ando, Takashi; Araki, Shouhei; Chen, Sidong; Chiga, Nobuyuki; Doornenbal, Pieter; Fukuda, Naoki; Isobe, Tadaaki; Kawakami, Shunsuke; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shunpei; Kubono, Shigeru; Maeda, Yukie; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shin'ichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakamura, Takashi; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Taniuchi, Ryo; Togano, Yasuhiro; Tsubota, Jun'ichi; Uesaka, Meiko; Watanabe, Yasushi; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-09-01

Spallation reactions for the long-lived fission product ^{93}Zr have been studied in order to provide basic data necessary for nuclear waste transmutation. Isotopic-production cross sections via proton- and deuteron-induced spallation reactions on ^{93}Zr at 105 MeV/nucleon were measured in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Remarkable jumps in isotopic production originating from the neutron magic number N=50 were observed in Zr and Y isotopes. The experimental results were compared to the PHITS calculations considering both the intranuclear cascade and evaporation processes, and the calculations greatly overestimated the measured production yield, corresponding to few-nucleon-removal reactions. The present data suggest that the spallation reaction is a potential candidate for the treatment of ^{93}Zr in spent nuclear fuel.

Neutron diffraction studies of a four-coordinated hydride in near square-planar geometry

DOE PAGES

Liao, Jian -Hong; Dhayal, Rajendra Singh; Wang, Xiaoping; ...

2014-10-07

The structure of a nanospheric polyhydrido copper cluster, [Cu 20(H) 11{S 2P(O iPr) 2} 9], was determined by single-crystal neutron diffraction. Cu 20 cluster consists of an elongated triangular orthobicupola constructed from 18 Cu atoms that encapsulate a [Cu 2H 5} 3- ion in the center with an exceptionally short Cu-Cu distance. The eleven hydrides in the cluster display three different coordination modes to the Cu atoms: Six μ 3-hydrides in pyramidal geometry, two μ 4-hydrides in tetrahedral cavity, and three μ 4-hydrides in an unprecedented near square-planar geometry. The neutron data set was collected on a small crystal ofmore » the size 0.20 mm x 0.50 mm x 0.65 mm for seven days using the Spallation Neutron Source TOPAZ single-crystal time-of-flight Laue diffractometer at the Oak Ridge National Laboratory. Furthermore, the final R-factor is 8.64% for 16014 reflections.« less

Helium Bubble Injection Solution To The Cavitation Damage At The Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francis, M. W.; Ruggles, A. E.

2009-03-10

The Spallation Neutron Source (SNS) is one of the largest science projects in the United States, with total cost near 1.4 Billion Dollars. The limiting factor of the facility had always been assumed to be the lifetime of the target window due to radiation damage. After further investigation, the lifetime of the target was determined not to be limited by radiation damage but by cavitation damage. The cavitation damage derives from pressure waves caused by the beam energy deposition. Vapor bubbles form when low to negative pressures occur in the mercury near the stainless steel target window due to wavemore » interaction with the structure. Collapse of these bubbles can focus wave energy in small liquid jets that erode the window surface. Compressibility of the mercury can be enhanced to reduce the amplitude of the pressure wave caused by the beam energy deposition. To enhance compressibility, small (10 to 30 micron diameter) gas bubbles could be injected into the bulk of the mercury. Solubility and diffusivity parameters of inert gas in mercury are required for a complete mechanical simulation and engineering of these strategies. Using current theoretical models, one obtains a theoretical Henry coefficient of helium in mercury on the order of 3.9E15 Pa-molHg/molHe at 300 K. This low solubility was confirmed by a direct, offline experimental method. Mercury was charged with helium and any pressure change was recorded. Any pressure change was attributed to gas going into solution. Therefore, with the sensitivity of the experiment, a lower limit of 9E12 Pa-molHg/molHe was placed on the mercury-helium system. These values guarantee a stable bubble lifetime needed within the SNS mercury target to mitigate cavitation issues.« less

A Neutron Diffractometer for a Long Pulsed Neutron Source

NASA Astrophysics Data System (ADS)

Sokol, Paul; Wang, Cailin

Long pulsed neutron sources are being actively developed as small university based sources and are being considered for the next generation of high powered sources, such as the European Neutron Source (ESS) and the Spallation Neutron Source (SNS) second target station. New instrumentation concepts will be required to effectively utilize the full spectrum of neutrons generated by these sources. Neutron diffractometers, which utilize time-of-flight (TOF) techniques for wavelength resolution, are particularly problematic. We describe an instrument for a long pulsed source that provides resolution comparable to that obtained on short pulsed sources without the need of long incident flight paths. We accomplish this by utilizing high speed choppers to impose a time structure on the spectrum of incident neutrons. By strategically positioning these choppers the response matrix assumes a convenient form that can be deconvoluted from the measured TOF spectrum to produce the diffraction pattern of the sample. We compare the performance of this instrument to other possible diffraction instruments that could be utilized on a long pulsed source.

Accelerator driven neutron source design via beryllium target and 208Pb moderator for boron neutron capture therapy in alternative treatment strategy by Monte Carlo method.

PubMed

Khorshidi, Abdollah

2017-01-01

The reactor has increased its area of application into medicine especially boron neutron capture therapy (BNCT); however, accelerator-driven neutron sources can be used for therapy purposes. The present study aimed to discuss an alternative method in BNCT functions by a small cyclotron with low current protons based on Karaj cyclotron in Iran. An epithermal neutron spectrum generator was simulated with 30 MeV proton energy for BNCT purposes. A low current of 300 μA of the proton beam in spallation target concept via 9Be target was accomplished to model neutron spectrum using 208Pb moderator around the target. The graphite reflector and dual layer collimator were planned to prevent and collimate the neutrons produced from proton interactions. Neutron yield per proton, energy distribution, flux, and dose components in the simulated head phantom were estimated by MCNPX code. The neutron beam quality was investigated by diverse filters thicknesses. The maximum epithermal flux transpired using Fluental, Fe, Li, and Bi filters with thicknesses of 7.4, 3, 0.5, and 4 cm, respectively; as well as the epithermal to thermal neutron flux ratio was 161. Results demonstrated that the induced neutrons from a low energy and low current proton may be effective in tumor therapy using 208Pb moderator with average lethargy and also graphite reflector with low absorption cross section to keep the generated neutrons. Combination of spallation-based BNCT and proton therapy can be especially effective, if a high beam intensity cyclotron becomes available.

2011 U.S. National School on Neutron and X-ray Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, Jonathan; te Vethuis, Suzanne; Ekkebus, Allen E

The 13th annual U.S. National School on Neutron and X-ray Scattering was held June 11 to 25, 2011, at both Oak Ridge and Argonne National Laboratories. This school brought together 65 early career graduate students from 56 different universities in the US and provided them with a broad introduction to the techniques available at the major large-scale neutron and synchrotron x-ray facilities. This school is focused primarily on techniques relevant to the physical sciences, but also touches on cross-disciplinary bio-related scattering measurements. During the school, students received lectures by over 30 researchers from academia, industry, and national laboratories and participatedmore » in a number of short demonstration experiments at Argonne's Advanced Photon Source (APS) and Oak Ridge's Spallation neutron Source (SNS) and High Flux Isotope Reactor (HFIR) facilities to get hands-on experience in using neutron and synchrotron sources. The first week of this year's school was held at Oak Ridge National Lab, where Lab director Thom Mason welcomed the students and provided a shitorical perspective of the neutron and x-ray facilities both at Oak Ridge and Argonne. The first few days of the school were dedicated to lectures laying out the basics of scattering theory and the differences and complementarity between the neutron and x-ray probes given by Sunil Sinha. Jack Carpenter provided an introduction into how neutrons are generated and detected. After this basic introduction, the students received lectures each morning on specific techniques and conducted demonstration experiments each afternoon on one of 15 different instruments at either the SNS or HFIR. Some of the topics covered during this week of the school included inelastic neutron scattering by Bruce Gaulin, x-ray and neutron reflectivity by Chuck Majkrazak, small-angle scattering by Volker Urban, powder diffraction by Ashfia Huq and diffuse scattering by Gene Ice.« less

New large volume hydrothermal reaction cell for studying chemical processes under supercritical hydrothermal conditions using time-resolved in situ neutron diffraction.

PubMed

Ok, Kang Min; O'Hare, Dermot; Smith, Ronald I; Chowdhury, Mohammed; Fikremariam, Hanna

2010-12-01

The design and testing of a new large volume Inconel pressure cell for the in situ study of supercritical hydrothermal syntheses using time-resolved neutron diffraction is introduced for the first time. The commissioning of this new cell is demonstrated by the measurement of the time-of-flight neutron diffraction pattern for TiO(2) (Anatase) in supercritical D(2)O on the POLARIS diffractometer at the United Kingdom's pulsed spallation neutron source, ISIS, Rutherford Appleton Laboratory. The sample can be studied over a wide range of temperatures (25-450 °C) and pressures (1-355 bar). This novel apparatus will now enable us to study the kinetics and mechanisms of chemical syntheses under extreme environments such as supercritical water, and in particular to study the crystallization of a variety of technologically important inorganic materials.

Characterization of the high-energy neutron beam of the PRISMA beamline using a diamond detector

NASA Astrophysics Data System (ADS)

Cazzaniga, C.; Frost, C. D.; Minniti, T.; Schooneveld, E.; Perelli Cippo, E.; Tardocchi, M.; Rebai, M.; Gorini, G.

2016-07-01

The high-energy neutron component (En > 10 MeV) of the neutron spectrum of PRISMA, a beam-line at the ISIS spallation source, has been characterized for the first time. Neutron measurements using a Single-crystal Diamond Detector at a short-pulse source are obtained by a combination of pulse height and time of flight analysis. An XY scan provides a 2D map of the high-energy neutron beam which has a diameter of about 40 mm. The high neutron flux, that has been found to be (3.8 ± 0.7) · 105 cm-2s-1 for En > 10 MeV in the centre, opens up for a possible application of the beam-line as a high-energy neutron irradiation position. Results are of interest for the development of the ChipIR beam-line, which will feature an atmospheric-like neutron spectrum for chip irradiation experiment. Furthermore, these results demonstrate that diamond detectors can be used at spallation sources to investigate the transport of high-energy neutrons down instruments which is of interest in general to designers as high-energy neutrons are a source of background in thermal beamlines.

Evaluation of the 3-GeV proton beam profile at the spallation target of the JSNS

NASA Astrophysics Data System (ADS)

Meigo, Shin-ichiro; Noda, Fumiaki; Ishikura, Syuichi; Futakawa, Masatoshi; Sakamoto, Shinichi; Ikeda, Yujiro

2006-06-01

At JSNS, 3-GeV protons beam is delivered from rapid cycling synchrotron (RCS) to the spallation neutron target. In order to reduce the damage of pitting on the target container, the peak current density should be kept as small as possible. In this study, the beam profile at spallation neutron target is evaluated. The phase-space distribution, including the space-charge effect, is calculated with SIMPSONS code. The beam profile on the target is obtained with the transfer matrix from exit of RCS to the target. As for injection to RCS, two methods of correlated and anti-correlated painting are considered. By using anti-correlated painting for injection of beam at RCS, it is found the shape of beam becomes flatter than the distribution by using correlated painting. As other aspect for the study of target, in order to carry out target performance test especially for the study of pitting issue, it is better to have the beam profile variety from the beginning of facility. The adjustable range for the beam profile at the beginning is also studied. Although the beam shape is narrow and the duty is very low, the strong enough peak density is achievable equivalent as 1 MW.

Single Crystal Diffuse Neutron Scattering

DOE PAGES

Welberry, Richard; Whitfield, Ross

2018-01-11

Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. Here, we compare three different instruments that have been used bymore » us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.« less

Single Crystal Diffuse Neutron Scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welberry, Richard; Whitfield, Ross

Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. Here, we compare three different instruments that have been used bymore » us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source.« less

Ship Effect Neutron Measurements And Impacts On Low-Background Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Siciliano, Edward R.

2013-10-01

The primary particles entering the upper atmosphere as cosmic rays create showers in the atmosphere that include a broad spectrum of secondary neutrons, muons and protons. These cosmic-ray secondaries interact with materials at the surface of the Earth, yielding prompt backgrounds in radiation detection systems, as well as inducing long-lived activities through spallation events, dominated by the higher-energy neutron secondaries. For historical reasons, the multiple neutrons produced in spallation cascade events are referred to as “ship effect” neutrons. Quantifying the background from cosmic ray induced activities is important to low-background experiments, such as neutrino-less double beta decay. Since direct measurementsmore » of the effects of shielding on the cosmic-ray neutron spectrum are not available, Monte Carlo modeling is used to compute such effects. However, there are large uncertainties (orders of magnitude) in the possible cross-section libraries and the cosmic-ray neutron spectrum for the energy range needed in such calculations. The measurements reported here were initiated to validate results from Monte Carlo models through experimental measurements in order to provide some confidence in the model results. The results indicate that the models provide the correct trends of neutron production with increasing density, but there is substantial disagreement between the model and experimental results for the lower-density materials of Al, Fe and Cu.« less

Plastic fiber scintillator response to fast neutrons

NASA Astrophysics Data System (ADS)

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

2014-11-01

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

Plastic fiber scintillator response to fast neutrons.

PubMed

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

2014-11-01

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

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

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Fifteen years of the Protein Crystallography Station: the coming of age of macromolecular neutron crystallography.

PubMed

Chen, Julian C-H; Unkefer, Clifford J

2017-01-01

The Protein Crystallography Station (PCS), located at the Los Alamos Neutron Scattering Center (LANSCE), was the first macromolecular crystallography beamline to be built at a spallation neutron source. Following testing and commissioning, the PCS user program was funded by the Biology and Environmental Research program of the Department of Energy Office of Science (DOE-OBER) for 13 years (2002-2014). The PCS remained the only dedicated macromolecular neutron crystallography station in North America until the construction and commissioning of the MaNDi and IMAGINE instruments at Oak Ridge National Laboratory, which started in 2012. The instrument produced a number of research and technical outcomes that have contributed to the field, clearly demonstrating the power of neutron crystallo-graphy in helping scientists to understand enzyme reaction mechanisms, hydrogen bonding and visualization of H-atom positions, which are critical to nearly all chemical reactions. During this period, neutron crystallography became a technique that increasingly gained traction, and became more integrated into macromolecular crystallography through software developments led by investigators at the PCS. This review highlights the contributions of the PCS to macromolecular neutron crystallography, and gives an overview of the history of neutron crystallography and the development of macromolecular neutron crystallography from the 1960s to the 1990s and onwards through the 2000s.

VSI@ESS: Case study for a vibrational spectroscopy instrument at the european spallation source

NASA Astrophysics Data System (ADS)

Zoppi, Marco; Fedrigo, Anna; Celli, Milva; Colognesi, Daniele

2015-01-01

Neutron Vibrational Spectroscopy is a well-established experimental technique where elementary excitations at relatively high frequency are detected via inelastic neutron scattering. This technique attracts a high interest in a large fraction of the scientific community in the fields of chemistry, materials science, physics, and biology, since one of its main applications exploits the large incoherent scattering cross section of the proton with respect to all the other elements, whose dynamics can be spectroscopically detected, even if dissolved in very low concentration in materials composed of much heavier atoms. We have proposed a feasibility study for a Vibrational Spectroscopy Instrument (VSI) at the European Spallation Source ESS. Here, we will summarize the preliminary design calculations and the corresponding McStas simulation results for a possible ToF, Inverted Geometry, VSI beamline.

Neutron diffraction measurements on a reference metallic sample with a high-efficiency GEM side-on 10B-based thermal neutron detector

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Claps, G.; Fedrigo, A.; Grazzi, F.; Höglund, C.; Murtas, F.; Scherillo, A.; Schmidt, S.; Schooneveld, E. M.

2018-03-01

The upgraded version of the GEM side-on thermal neutron detector was successfully tested in a neutron diffraction experiment on a reference sample using the INES diffractometer at the ISIS spallation neutron source, UK. The performance of the new 10B4C-based detector is compared to that of a standard 3He tube, operating at the instrument as a part of the detectors assembly. The results show that the upgraded detector has a better resolution and an efficiency of the same order of magnitude of a 3He-based detector.

The Los ALamos Neutron Science Center Hydrogen Moderator System

NASA Astrophysics Data System (ADS)

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

2006-04-01

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

Validation of PHITS Spallation Models from the Perspective of the Shielding Design of Transmutation Experimental Facility

NASA Astrophysics Data System (ADS)

Iwamoto, Hiroki; Meigo, Shin-ichiro

2017-09-01

The impact of different spallation models implemented in the particle transport code PHITS on the shielding design of Transmutation Experimental Facility is investigated. For 400-MeV proton incident on a lead-bismuth eutectic target, an effective dose rate at the end of a thick radiation shield (3-m-thick iron and 3-m-thick concrete) calculated by the Liège intranuclear cascade (INC) model version 4.6 (INCL4.6) coupled with the GEMcode (INCL4.6/GEM) yields about twice as high as the Bertini INC model (Bertini/GEM). A comparison with experimental data for 500-MeV proton incident on a thick lead target suggest that the prediction accuracy of INCL4.6/GEM would be better than that of Bertini/GEM. In contrast, it is found that the dose rates in beam ducts in front of targets calculated by the INCL4.6/GEMare lower than those by the Bertini/GEM. Since both models underestimate the experimental results for neutron-production doubledifferential cross sections at 180° for 140-MeV proton incident on carbon, iron, and gold targets, it is concluded that it is necessary to allow a margin for uncertainty caused by the spallation models, which is a factor of two, in estimating the dose rate induced by neutron streaming through a beam duct.

Study of the Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND

DOE Office of Scientific and Technical Information (OSTI.GOV)

KamLAND Collaboration; Abe, S.; Enomoto, S.

2009-06-30

Radioactive isotopes produced through cosmic muon spallation are a background for rare event detection in {nu} detectors, double-beta-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of {sup 11}C. Data from the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillator, and for checking estimates from current simulations based upon MUSIC, FLUKA, and Geant4. Using the time correlation between detected muons and neutronmore » captures, the neutron production yield in the KamLAND liquid scintillator is measured to be (2.8 {+-} 0.3) x 10{sup -4} n/({mu} {center_dot} (g/cm{sup 2})). For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.« less

Characterization of the Shielded Neutron Source at Triangle Universities Nuclear Laboratory

NASA Astrophysics Data System (ADS)

Hobson, Chad; Finch, Sean; Howell, Calvin; Malone, Ron; Tornow, Wernew

2016-09-01

In 2015, Triangle Universities Nuclear Laboratory rebuilt its shielded neutron source (SNS) with the goal of improving neutron beam collimation and reducing neutron and gamma-ray backgrounds. Neutrons are produced via the 2H(d,n)3He reaction and then collimated by heavy shielding to form a beam. The SNS has the ability to produce both a rectangular and circular neutron beam through use of two collimators with different beam apertures. Our work characterized both the neutron beam profiles as well as the neutron and gamma-ray backgrounds at various locations around the SNS. This characterization was performed to provide researchers who use the SNS with beam parameters necessary to plan and conduct an experiment. Vertical and horizontal beam profiles were measured at two different distances from the neutron production cell by scanning a small plastic scintillator across the face of the beam at various energies for each collimator. Background neutron and gamma-ray intensities were measured using time-of-flight techniques at 10 MeV and 16 MeV with the rectangular collimator. We present results on the position and size of neutron beam as well as on the structure and magnitude of the backgrounds.

Radiological Hazard of Spallation Products in Accelerator-Driven System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saito, M.; Stankovskii, A.; Artisyuk, V.

The central issue underlying this paper is related to elucidating the hazard of radioactive spallation products that might be an important factor affecting the design option of accelerator-driven systems (ADSs). Hazard analysis based on the concept of Annual Limit on Intake identifies alpha-emitting isotopes of rare earths (REs) (dysprosium, gadolinium, and samarium) as the dominant contributors to the overall toxicity of traditional (W, Pb, Pb-Bi) targets. The matter is addressed from several points of view: code validation to simulate their yields, choice of material for the neutron producing targets, and challenging the beam type. The paper quantitatively determines the domainmore » in which the toxicity of REs exceeds that of polonium activation products broadly discussed now in connection with advertising lead-bismuth technology for the needs of ADSs.« less

Preliminary Evaluation of Cavitation-Erosion Resistance of Ti-Alloys in Mercury for the Spallation Neutron Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J; Mansur, Louis K

2010-01-01

A number of Ti-based alloys in both the mill-annealed and 20% cold-worked conditions were subjected to sonication conditions in Hg using a vibratory horn to assess relative cavitation-erosion resistance. Weight loss as a function of exposure time was roughly proportional to hardness for all alloys/conditions examined, with Ti-6Al-4V (Ti-Grade 5) and Ti-6Al-2Sn-4Zr-2Mo yielding the best resistance to cavitation-erosion as evidenced by low weight losses and little or no tendency to form pits on the exposed surface. Unalloyed Ti (Ti-Grade 4) and Ti-0.12Pd (Ti-Grade 7) exhibited greater weight losses by a factor or about two and about five, respectively, with Ti-0.12Pdmore » particularly prone to pitting development. The mean erosion rates of the best two Ti-alloys examined here were about a factor of three higher than identically tested 316LN stainless steel following a low temperature carburizing treatment, but this difference is considered minor given that the rate for both materials is very low/manageable and represents a through-thickness property for the Ti-alloys. A nitriding surface treatment was also evaluated as a potential method to further increase the cavitation-erosion resistance of these alloys in Hg, but the selected treatment proved largely ineffective. Recommendations for further work to evaluate the efficacy of Ti-based alloys for use in high-powered targets for the Spallation Neutron Source are given.« less

Determination of the axial-vector weak coupling constant with ultracold neutrons.

PubMed

Liu, J; Mendenhall, M P; Holley, A T; Back, H O; Bowles, T J; Broussard, L J; Carr, R; Clayton, S; Currie, S; Filippone, B W; García, A; Geltenbort, P; Hickerson, K P; Hoagland, J; Hogan, G E; Hona, B; Ito, T M; Liu, C-Y; Makela, M; Mammei, R R; Martin, J W; Melconian, D; Morris, C L; Pattie, R W; Pérez Galván, A; Pitt, M L; Plaster, B; Ramsey, J C; Rios, R; Russell, R; Saunders, A; Seestrom, S J; Sondheim, W E; Tatar, E; Vogelaar, R B; VornDick, B; Wrede, C; Yan, H; Young, A R

2010-10-29

A precise measurement of the neutron decay β asymmetry A₀ has been carried out using polarized ultracold neutrons from the pulsed spallation ultracold neutron source at the Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report A₀ = -0.119 66±0.000 89{-0.001 40}{+0.001 23}, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon g{A}/g{V}=-1.275 90{-0.004 45}{+0.004 09}.

High-temperature long-lasting stability assessment of a single-crystal diamond detector under high-flux neutron irradiation

NASA Astrophysics Data System (ADS)

Pilotti, R.; Angelone, M.; Marinelli, M.; Milani, E.; Verona-Rinati, G.; Verona, C.; Prestopino, G.; Montereali, R. M.; Vincenti, M. A.; Schooneveld, E. M.; Scherillo, A.; Pietropaolo, A.

2016-11-01

An innovative diamond detector layout is presented that is designed to operate at high temperature under intense neutron and gamma fluxes. It is made of a 500 μm “electronic grade” diamond film with 100 nm thick Ag metal contacts deposited onto each surface of the film by means of thermal evaporation. A 2 μ \\text{m} thick layer of 6LiF has been deposited on top of one of the two Ag contacts to make the detector sensitive to thermal neutrons. The device was tested at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK) using the INES beam line. The detector was continuously irradiated for 100 hours in vacuum (p = 10-5 \\text{mbar}) , exposed to a neutron flux of about 106 n cm-2 s-1 at a temperature T =150 ^\\circ \\text{C} . The aim of this experiment was to study the time dependence of the diamond detector performance while operating at high temperature under irradiation, providing a first experimental proof of reliable continuous operation for 100 hours at high temperature in a harsh environment.

SINGLE EVENT EFFECTS TEST FACILITY AT OAK RIDGE NATIONAL LABORATORY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riemer, Bernie; Gallmeier, Franz X; Dominik, Laura J

2015-01-01

Increasing use of microelectronics of ever diminishing feature size in avionics systems has led to a growing Single Event Effects (SEE) susceptibility arising from the highly ionizing interactions of cosmic rays and solar particles. Single event effects caused by atmospheric radiation have been recognized in recent years as a design issue for avionics equipment and systems. To ensure a system meets all its safety and reliability requirements, SEE induced upsets and potential system failures need to be considered, including testing of the components and systems in a neutron beam. Testing of ICs and systems for use in radiation environments requiresmore » the utilization of highly advanced laboratory facilities that can run evaluations on microcircuits for the effects of radiation. This paper provides a background of the atmospheric radiation phenomenon and the resulting single event effects, including single event upset (SEU) and latch up conditions. A study investigating requirements for future single event effect irradiation test facilities and developing options at the Spallation Neutron Source (SNS) is summarized. The relatively new SNS with its 1.0 GeV proton beam, typical operation of 5000 h per year, expertise in spallation neutron sources, user program infrastructure, and decades of useful life ahead is well suited for hosting a world-class SEE test facility in North America. Emphasis was put on testing of large avionics systems while still providing tunable high flux irradiation conditions for component tests. Makers of ground-based systems would also be served well by these facilities. Three options are described; the most capable, flexible, and highest-test-capacity option is a new stand-alone target station using about one kW of proton beam power on a gas-cooled tungsten target, with dual test enclosures. Less expensive options are also described.« less

ICANS-XIV. The fourteenth meeting of the international collaboration on advanced neutron sources.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carpenter, J. M., ed.; Tobin, C. A., ed.

1999-02-10

The meeting began with a reception on Sunday evening. Monday's plenary sessions included status reports on the four operating spallation neutron sources, IPNS, ISIS, KENS, and the Lujan Center; on the INR source under construction at Troitsk; on the IBR-2 pulsed reactor at Dubna; and on proposals for five new installations. We also heard reports on spin-off activities: the ASTE tests (liquid mercury target tests at the AGS accelerator at Brookhaven), the ACoM activities (developments aimed to provide cold moderators suitable for high-power pulsed sources), and the International Workshop on Cold Moderators for Pulsed Neutron Sources, held in September 1997more » at Argonne. Jose Alonso and Bob Macek delivered enlightening invited talks overviewing linear accelerators and rings for spallation neutron sources. The rest of the meeting was devoted to targets and moderators and to instrumentation in a normal rotation of ICANS topics. There were altogether 84 oral reports and 23 poster presentations. On Tuesday and on Wednesday morning, we divided into separate series of sessions on Instrumentation and on Targets and Moderators. In the first, we had reports and discussions on instrumentation and techniques, on computer software, on instrument suites, and on new instruments and equipment. In the second series were sessions on liquid target systems, on solid target systems, on neutron production and target physics, on moderator physics and performance, and on target and moderator neutronics. The Tuesday evening meetings went on until 10:00, making for a 14-hour working day. That everyone willingly endured the long hours is a credit to the dedication of the attendees. On Wednesday afternoon, we boarded buses for the 1-hour trip to Argonne, where attendees toured IPNS and the Advanced Photon Source. Returning to Starved Rock, we enjoyed boat rides on the Illinois River and then a barbecue banquet dinner at the Lodge. All day Thursday and Friday morning, the attendees, in

ORNL Neutron Sciences Annual Report for 2007

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Ian S; Horak, Charlie M; Counce, Deborah Melinda

2008-07-01

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

Fifteen years of the Protein Crystallography Station: The coming of age of macromolecular neutron crystallography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Julian C.-H.; Unkefer, Clifford Jay

The Protein Crystallography Station (PCS), located at the Los Alamos Neutron Scattering Center (LANSCE), was the first macromolecular crystallography beamline to be built at a spallation neutron source. Following testing and commissioning, the PCS user program was funded by the Biology and Environmental Research program of the Department of Energy Office of Science (DOE-OBER) for 13 years (2002–2014). The PCS remained the only dedicated macromolecular neutron crystallography station in North America until the construction and commissioning of the MaNDi and IMAGINE instruments at Oak Ridge National Laboratory, which started in 2012. The instrument produced a number of research and technicalmore » outcomes that have contributed to the field, clearly demonstrating the power of neutron crystallography in helping scientists to understand enzyme reaction mechanisms, hydrogen bonding and visualization of H-atom positions, which are critical to nearly all chemical reactions. During this period, neutron crystallography became a technique that increasingly gained traction, and became more integrated into macromolecular crystallography through software developments led by investigators at the PCS. As a result, this review highlights the contributions of the PCS to macromolecular neutron crystallography, and gives an overview of the history of neutron crystallography and the development of macromolecular neutron crystallography from the 1960s to the 1990s and onwards through the 2000s.« less

Fifteen years of the Protein Crystallography Station: The coming of age of macromolecular neutron crystallography

DOE PAGES

Chen, Julian C.-H.; Unkefer, Clifford Jay

2017-01-01

The Protein Crystallography Station (PCS), located at the Los Alamos Neutron Scattering Center (LANSCE), was the first macromolecular crystallography beamline to be built at a spallation neutron source. Following testing and commissioning, the PCS user program was funded by the Biology and Environmental Research program of the Department of Energy Office of Science (DOE-OBER) for 13 years (2002–2014). The PCS remained the only dedicated macromolecular neutron crystallography station in North America until the construction and commissioning of the MaNDi and IMAGINE instruments at Oak Ridge National Laboratory, which started in 2012. The instrument produced a number of research and technicalmore » outcomes that have contributed to the field, clearly demonstrating the power of neutron crystallography in helping scientists to understand enzyme reaction mechanisms, hydrogen bonding and visualization of H-atom positions, which are critical to nearly all chemical reactions. During this period, neutron crystallography became a technique that increasingly gained traction, and became more integrated into macromolecular crystallography through software developments led by investigators at the PCS. As a result, this review highlights the contributions of the PCS to macromolecular neutron crystallography, and gives an overview of the history of neutron crystallography and the development of macromolecular neutron crystallography from the 1960s to the 1990s and onwards through the 2000s.« less

Fifteen years of the Protein Crystallography Station: the coming of age of macromolecular neutron crystallography

PubMed Central

Chen, Julian C.-H.

2017-01-01

The Protein Crystallography Station (PCS), located at the Los Alamos Neutron Scattering Center (LANSCE), was the first macromolecular crystallography beamline to be built at a spallation neutron source. Following testing and commissioning, the PCS user program was funded by the Biology and Environmental Research program of the Department of Energy Office of Science (DOE-OBER) for 13 years (2002–2014). The PCS remained the only dedicated macromolecular neutron crystallography station in North America until the construction and commissioning of the MaNDi and IMAGINE instruments at Oak Ridge National Laboratory, which started in 2012. The instrument produced a number of research and technical outcomes that have contributed to the field, clearly demonstrating the power of neutron crystallo­graphy in helping scientists to understand enzyme reaction mechanisms, hydrogen bonding and visualization of H-atom positions, which are critical to nearly all chemical reactions. During this period, neutron crystallography became a technique that increasingly gained traction, and became more integrated into macromolecular crystallography through software developments led by investigators at the PCS. This review highlights the contributions of the PCS to macromolecular neutron crystallography, and gives an overview of the history of neutron crystallography and the development of macromolecular neutron crystallography from the 1960s to the 1990s and onwards through the 2000s. PMID:28250943

Energy-resolved fast neutron resonance radiography at CSNS

NASA Astrophysics Data System (ADS)

Tan, Zhixin; Tang, Jingyu; Jing, Hantao; Fan, Ruirui; Li, Qiang; Ning, Changjun; Bao, Jie; Ruan, Xichao; Luan, Guangyuan; Feng, Changqin; Zhang, Xianpeng

2018-05-01

The white neutron beamline at the China Spallation Neutron Source will be used mainly for nuclear data measurements. It will be characterized by high flux and broad energy spectra. To exploit the beamline as a neutron imaging source, we propose a liquid scintillator fiber array for fast neutron resonance radiography. The fiber detector unit has a small exposed area, which will limit the event counts and separate the events in time, thus satisfying the requirements for single-event time-of-flight (SEToF) measurement. The current study addresses the physical design criteria for ToF measurement, including flux estimation and detector response. Future development and potential application of the technology are also discussed.

Extracting grain-orientation-dependent data from in situ time-of-flight neutron diffraction. I. Inverse pole figures

DOE PAGES

Stoica, Grigoreta M.; Stoica, Alexandru Dan; An, Ke; ...

2014-11-28

The problem of calculating the inverse pole figure (IPF) is analyzed from the perspective of the application of time-of flight neutron diffraction toin situmonitoring of the thermomechanical behavior of engineering materials. On the basis of a quasi-Monte Carlo (QMC) method, a consistent set of grain orientations is generated and used to compute the weighting factors for IPF normalization. The weighting factors are instrument dependent and were calculated for the engineering materials diffractometer VULCAN (Spallation Neutron Source, Oak Ridge National Laboratory). The QMC method is applied to face-centered cubic structures and can be easily extended to other crystallographic symmetries. Examples includemore » 316LN stainless steelin situloaded in tension at room temperature and an Al–2%Mg alloy, substantially deformed by cold rolling and in situannealed up to 653 K.« less

Longitudinal space charge compensation at PSR

NASA Astrophysics Data System (ADS)

Neri, Filippo

1998-11-01

The longitudinal space-charge force in neutron spallation source compressor ring or other high intensity proton storage rings can be compensated by introducing an insert in the ring. The effect of the inductor is to cancel all or part of the space charge potential, because it is capacitive. The Proton Storage Ring at Los Alamos National Laboratory is a compressor ring used to produce short pulses of spallation neutrons. Inductive inserts design for space charge compensation at the Los Alamos Proton Storage Ring is described.

Monte carlo simulations of the n_TOF lead spallation target with the Geant4 toolkit: A benchmark study

NASA Astrophysics Data System (ADS)

Lerendegui-Marco, J.; Cortés-Giraldo, M. A.; Guerrero, C.; Quesada, J. M.; Meo, S. Lo; Massimi, C.; Barbagallo, M.; Colonna, N.; Mancussi, D.; Mingrone, F.; Sabaté-Gilarte, M.; Vannini, G.; Vlachoudis, V.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Cortés, G.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; Gómez-Hornillos, M. B.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Valenta, S.; Variale, V.; Vaz, P.; Ventura, A.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec, P.

2017-09-01

Monte Carlo (MC) simulations are an essential tool to determine fundamental features of a neutron beam, such as the neutron flux or the γ-ray background, that sometimes can not be measured or at least not in every position or energy range. Until recently, the most widely used MC codes in this field had been MCNPX and FLUKA. However, the Geant4 toolkit has also become a competitive code for the transport of neutrons after the development of the native Geant4 format for neutron data libraries, G4NDL. In this context, we present the Geant4 simulations of the neutron spallation target of the n_TOF facility at CERN, done with version 10.1.1 of the toolkit. The first goal was the validation of the intra-nuclear cascade models implemented in the code using, as benchmark, the characteristics of the neutron beam measured at the first experimental area (EAR1), especially the neutron flux and energy distribution, and the time distribution of neutrons of equal kinetic energy, the so-called Resolution Function. The second goal was the development of a Monte Carlo tool aimed to provide useful calculations for both the analysis and planning of the upcoming measurements at the new experimental area (EAR2) of the facility.

Measurement of the fast neutron background at the China Jinping Underground Laboratory

NASA Astrophysics Data System (ADS)

Du, Q.; Lin, S. T.; Liu, S. K.; Tang, C. J.; Wang, L.; Wei, W. W.; Wong, H. T.; Xing, H. Y.; Yue, Q.; Zhu, J. J.

2018-05-01

We report on the measurements of the fluxes and spectra of the environmental fast neutron background at the China Jinping Underground Laboratory (CJPL) with a rock overburden of about 6700 meters water equivalent, using a liquid scintillator detector doped with 0.5% gadolinium. The signature of a prompt nuclear recoil followed by a delayed high energy γ-ray cascade is used to identify neutron events. The large energy deposition of the delayed γ-rays from the (n , γ) reaction on gadolinium, together with the excellent n- γ discrimination capability provides a powerful background suppression which allows the measurement of a low intensity neutron flux. The neutron flux of (1 . 51 ± 0 . 03(stat .) ± 0 . 10(syst .)) × 10-7cm-2s-1 in the energy range of 1-10 MeV in the Hall A of CJPL was measured based on 356 days of data. In the same energy region, measurement with the same detector placed in a room surrounding with one meter thick polyethylene shielding gives a significantly lower flux of (4 . 9 ± 0 . 9(stat .) ± 0 . 5(syst .)) × 10-9cm-2s-1 with 174 days of data. This represents a measurement of the lowest environmental fast neutron background among the underground laboratories in the world, prior to additional experiment-specific attenuation. Additionally, the fast neutron spectra both in the Hall A and the polyethylene room were reconstructed with the help of GEANT4 simulations.

Correlation between simulations and cavitation-induced erosion damage in Spallation Neutron Source target modules after operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riemer, Bernie; McClintock, David A; Kaminskas, Saulius

2014-01-01

An explicit finite element (FE) technique developed for estimating dynamic strain in the Spallation Neutron Source (SNS) mercury target module vessel is now providing insight into cavitation damage patterns observed in used targets. The technique uses an empirically developed material model for the mercury that describes liquid-like volumetric stiffness combined with a tensile pressure cut-off limit that approximates cavitation. The longest period each point in the mercury is at the tensile cut-off threshold is denoted its saturation time. Now, the pattern of saturation time can be obtained from these simulations and is being positively correlated with observed damage patterns andmore » is interpreted as a qualitative measure of damage potential. Saturation time has been advocated by collaborators at J-Parc as a factor in predicting bubble nuclei growth and collapse intensity. The larger the ratio of maximum bubble size to nucleus, the greater the bubble collapse intensity to be expected; longer saturation times result in greater ratios. With the recent development of a user subroutine for the FE solver saturation time is now provided over the entire mercury domain. Its pattern agrees with spots of damage seen above and below the beam axis on the SNS inner vessel beam window and elsewhere. The other simulation result being compared to observed damage patterns is mercury velocity at the wall. Related R&D has provided evidence for the damage mitigation that higher wall velocity provides. In comparison to observations in SNS targets, inverse correlation of high velocity to damage is seen. In effect, it is the combination of the patterns of saturation time and low velocity that seems to match actual damage patterns.« less

Neutron capture cross section measurement of 151Sm at the CERN neutron time of flight facility (n_TOF).

PubMed

Abbondanno, U; Aerts, G; Alvarez-Velarde, F; Alvarez-Pol, H; Andriamonje, S; Andrzejewski, J; Badurek, G; Baumann, P; Becvár, F; Benlliure, J; Berthoumieux, E; Calviño, F; Cano-Ott, D; Capote, R; Cennini, P; Chepel, V; Chiaveri, E; Colonna, N; Cortes, G; Cortina, D; Couture, A; Cox, J; Dababneh, S; Dahlfors, M; David, S; Dolfini, R; Domingo-Pardo, C; Duran, I; Embid-Segura, M; Ferrant, L; Ferrari, A; Ferreira-Marques, R; Frais-Koelbl, H; Furman, W; Goncalves, I; Gallino, R; Gonzalez-Romero, E; Goverdovski, A; Gramegna, F; Griesmayer, E; Gunsing, F; Haas, B; Haight, R; Heil, M; Herrera-Martinez, A; Isaev, S; Jericha, E; Käppeler, F; Kadi, Y; Karadimos, D; Kerveno, M; Ketlerov, V; Koehler, P; Konovalov, V; Krticka, M; Lamboudis, C; Leeb, H; Lindote, A; Lopes, I; Lozano, M; Lukic, S; Marganiec, J; Marrone, S; Martinez-Val, J; Mastinu, P; Mengoni, A; Milazzo, P M; Molina-Coballes, A; Moreau, C; Mosconi, M; Neves, F; Oberhummer, H; O'Brien, S; Pancin, J; Papaevangelou, T; Paradela, C; Pavlik, A; Pavlopoulos, P; Perlado, J M; Perrot, L; Pignatari, M; Plag, R; Plompen, A; Plukis, A; Poch, A; Policarpo, A; Pretel, C; Quesada, J; Raman, S; Rapp, W; Rauscher, T; Reifarth, R; Rosetti, M; Rubbia, C; Rudolf, G; Rullhusen, P; Salgado, J; Soares, J C; Stephan, C; Tagliente, G; Tain, J; Tassan-Got, L; Tavora, L; Terlizzi, R; Vannini, G; Vaz, P; Ventura, A; Villamarin, D; Vincente, M C; Vlachoudis, V; Voss, F; Wendler, H; Wiescher, M; Wisshak, K

2004-10-15

The151Sm(n,gamma)152Sm cross section has been measured at the spallation neutron facility n_TOF at CERN in the energy range from 1 eV to 1 MeV. The new facility combines excellent resolution in neutron time-of-flight, low repetition rates, and an unsurpassed instantaneous luminosity, resulting in rather favorable signal/background ratios. The 151Sm cross section is of importance for characterizing neutron capture nucleosynthesis in asymptotic giant branch stars. At a thermal energy of kT=30 keV the Maxwellian averaged cross section of this unstable isotope (t(1/2)=93 yr) was determined to be 3100+/-160 mb, significantly larger than theoretical predictions.

(3) He Spin Filter for Neutrons.

PubMed

Batz, M; Baeßler, S; Heil, W; Otten, E W; Rudersdorf, D; Schmiedeskamp, J; Sobolev, Y; Wolf, M

2005-01-01

The strongly spin-dependent absorption of neutrons in nuclear spin-polarized (3)He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable (3)He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts.

3He Spin Filter for Neutrons

PubMed Central

Batz, M.; Baeßler, S.; Heil, W.; Otten, E. W.; Rudersdorf, D.; Schmiedeskamp, J.; Sobolev, Y.; Wolf, M.

2005-01-01

The strongly spin-dependent absorption of neutrons in nuclear spin-polarized 3He opens up the possibility of polarizing neutrons from reactors and spallation sources over the full kinematical range of cold, thermal and hot neutrons. This paper gives a report on the neutron spin filter (NSF) development program at Mainz. The polarization technique is based on direct optical pumping of metastable 3He atoms combined with a polarization preserving mechanical compression of the gas up to a pressure of several bar, necessary to run a NSF. The concept of a remote type of operation using detachable NSF cells is presented which requires long nuclear spin relaxation times of order 100 hours. A short survey of their use under experimental conditions, e.g. large solid-angle polarization analysis, is given. In neutron particle physics NSFs are used in precision measurements to test fundamental symmetry concepts. PMID:27308139

First measurement of the VESUVIO neutron spectrum in the 30-80 MeV energy range using a Proton Recoil Telescope technique

NASA Astrophysics Data System (ADS)

Cazzaniga, C.; Tardocchi, M.; Croci, G.; Frost, C.; Giacomelli, L.; Grosso, G.; Hjalmarsson, A.; Rebai, M.; Rhodes, N. J.; Schooneveld, E. M.; Gorini, G.

2013-11-01

Measurements of the fast neutron energy spectrum at the ISIS spallation source are reported. The measurements were performed with a Proton Recoil Telescope consisting of a thin plastic foil placed in the neutron beam and two scintillator detectors. Results in the neutron energy range 30 MeV < En < 80 MeV are in good agreement with Monte Carlo simulations of the neutron spectrum.

Superconducting thermal neutron detectors

NASA Astrophysics Data System (ADS)

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

2016-09-01

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

Single Event Effects Test Facility Options at the Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riemer, Bernie; Gallmeier, Franz X; Dominik, Laura J

2015-01-01

Increasing use of microelectronics of ever diminishing feature size in avionics systems has led to a growing Single Event Effects (SEE) susceptibility arising from the highly ionizing interactions of cosmic rays and solar particles. Single event effects caused by atmospheric radiation have been recognized in recent years as a design issue for avionics equipment and systems. To ensure a system meets all its safety and reliability requirements, SEE induced upsets and potential system failures need to be considered, including testing of the components and systems in a neutron beam. Testing of integrated circuits (ICs) and systems for use in radiationmore » environments requires the utilization of highly advanced laboratory facilities that can run evaluations on microcircuits for the effects of radiation. This paper provides a background of the atmospheric radiation phenomenon and the resulting single event effects, including single event upset (SEU) and latch up conditions. A study investigating requirements for future single event effect irradiation test facilities and developing options at the Spallation Neutron Source (SNS) is summarized. The relatively new SNS with its 1.0 GeV proton beam, typical operation of 5000 h per year, expertise in spallation neutron sources, user program infrastructure, and decades of useful life ahead is well suited for hosting a world-class SEE test facility in North America. Emphasis was put on testing of large avionics systems while still providing tunable high flux irradiation conditions for component tests. Makers of ground-based systems would also be served well by these facilities. Three options are described; the most capable, flexible, and highest-test-capacity option is a new stand-alone target station using about one kW of proton beam power on a gas-cooled tungsten target, with dual test enclosures. Less expensive options are also described.« less

A high-rate 10B-loaded liquid scintillation detector for parity-violation studies in neutron resonances

NASA Astrophysics Data System (ADS)

Yen, Yi-Fen; Bowman, J. D.; Bolton, R. D.; Crawford, B. E.; Delheij, P. P. J.; Hart, G. W.; Haseyama, T.; Frankle, C. M.; Iinuma, M.; Knudson, J. N.; Masaike, A.; Masuda, Y.; Matsuda, Y.; Mitchell, G. E.; Penttilä, S. I.; Roberson, N. R.; Seestrom, S. J.; Sharapov, E.; Shimizu, H. M.; Smith, D. A.; Stephenson, S. L.; Szymanski, J. J.; Yoo, S. H.; Yuan, V. W.

2000-06-01

We have developed a large-area 10B-loaded liquid scintillation detector for parity-violation studies in neutron resonances with high instantaneous neutron fluxes from the LANSCE short-pulse spallation source. The detector has an efficiency of 95%, 85% and 71% at neutron energies of 10, 100 and 1000 eV, respectively. The neutron mean capture time in the detector is (416±5) ns. We describe the detector and the current-mode signal processing system, that can handle neutron rates up to 500 MHz.

Event-Based Processing of Neutron Scattering Data

DOE PAGES

Peterson, Peter F.; Campbell, Stuart I.; Reuter, Michael A.; ...

2015-09-16

Many of the world's time-of-flight spallation neutrons sources are migrating to the recording of individual neutron events. This provides for new opportunities in data processing, the least of which is to filter the events based on correlating them with logs of sample environment and other ancillary equipment. This paper will describe techniques for processing neutron scattering data acquired in event mode that preserve event information all the way to a final spectrum, including any necessary corrections or normalizations. This results in smaller final errors, while significantly reducing processing time and memory requirements in typical experiments. Results with traditional histogramming techniquesmore » will be shown for comparison.« less

Multi-criteria comparative evaluation of spallation reaction models

NASA Astrophysics Data System (ADS)

Andrianov, Andrey; Andrianova, Olga; Konobeev, Alexandr; Korovin, Yury; Kuptsov, Ilya

2017-09-01

This paper presents an approach to a comparative evaluation of the predictive ability of spallation reaction models based on widely used, well-proven multiple-criteria decision analysis methods (MAVT/MAUT, AHP, TOPSIS, PROMETHEE) and the results of such a comparison for 17 spallation reaction models in the presence of the interaction of high-energy protons with natPb.

Mining Archived HYSPEC User Data to Analyze the Prompt Pulse at the SNS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Michael B.; Iverson, Erik B.; Gallmeier, Franz X.

The Hybrid-Spectrometer (HYSPEC) is one of 17 instruments currently operated at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratories (ORNL). The secondary spectrometer of this instrument is located inside an out-building off the north side of the SNS instrument hall. HYSPEC has experienced a larger background feature than similar inelastic instruments since its commissioning in 2011. This background feature is caused by a phenomenon known as the “prompt pulse” which is an essential part of neutron production in a pulsed spallation source but comes with unfortunate side effects.

Measurement of the energy and multiplicity distributions of neutrons from the photofission of U 235

DOE PAGES

Clarke, S. D.; Wieger, B. M.; Enqvist, A.; ...

2017-06-20

For the first time, the complete neutron multiplicity distribution has been measured in this study from the photofission of 235U induced by high-energy spallation γ rays arriving ahead of the neutron beam at the Los Alamos Neutron Science Center. The resulting average neutron multiplicity 3.80 ± 0.08 (stat.) neutrons per photofission is in general agreement with previous measurements. In addition, unique measurements of the prompt fission energy spectrum of the neutrons from photofission and the angular correlation of two-neutron energies emitted in photofission also were made. Finally, the results are compared to calculations with the complete event fission model FREYA.

The planned search for free neutron-antineutron transformation using the nnbarX experiment at Fermilab and how it relates to bound neutron oscillations at Super-Kamiokande and elsewhere

NASA Astrophysics Data System (ADS)

Banuelos, Eddie

2012-11-01

In this presentation we will describe the role of CSUDH and present initial planning results on a new experiment at Fermilab called nnbarX that will use neutrons from a 1 MW cold spallation source near the Fermilab main accelerator ring which is being upgraded. This project will eventually probe theories of grand unification of the fundamental forces, the stability of matter, and how Baryons were created in the early stages of the big bang, at levels of sensitivity to the baryon lifetime that will be 100-10000 higher than what is currently available and will rule out or confirm leading theories of grand unification in which neutrons and other fermions are equally mixed with their antiparticles and can transform to each other in Right-Left symmetric theories such as SO(10). We at CSUDH will be directly collaborating with the University of Tennessee Knoxville, University of Indiana Bloomington, North Carolina State University, Femilab and Los Alamos National Laboratory on detector R & D for nnbarX and will be also working with a few other institutions in the US and in other countries.

GRAIN-SCALE FAILURE IN THERMAL SPALLATION DRILLING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walsh, S C; Lomov, I; Roberts, J J

2012-01-19

Geothermal power promises clean, renewable, reliable and potentially widely-available energy, but is limited by high initial capital costs. New drilling technologies are required to make geothermal power financially competitive with other energy sources. One potential solution is offered by Thermal Spallation Drilling (TSD) - a novel drilling technique in which small particles (spalls) are released from the rock surface by rapid heating. While TSD has the potential to improve drilling rates of brittle granitic rocks, the coupled thermomechanical processes involved in TSD are poorly described, making system control and optimization difficult for this drilling technology. In this paper, we discussmore » results from a new modeling effort investigating thermal spallation drilling. In particular, we describe an explicit model that simulates the grain-scale mechanics of thermal spallation and use this model to examine existing theories concerning spalling mechanisms. We will report how borehole conditions influence spall production, and discuss implications for macro-scale models of drilling systems.« less

Neutron Radiography and Computed Tomography at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Raine, Dudley A. III; Hubbard, Camden R.; Whaley, Paul M.

1997-12-31

The capability to perform neutron radiography and computed tomography is being developed at Oak Ridge National Laboratory. The facility will be located at the High Flux Isotope Reactor (HFIR), which has the highest steady state neutron flux of any reactor in the world. The Monte Carlo N-Particle transport code (MCNP), versions 4A and 4B, has been used extensively in the design phase of the facility to predict and optimize the operating characteristics, and to ensure the safety of personnel working in and around the blockhouse. Neutrons are quite penetrating in most engineering materials and can be useful to detect internalmore » flaws and features. Hydrogen atoms, such as in a hydrocarbon fuel, lubricant or a metal hydride, are relatively opaque to neutron transmission. Thus, neutron based tomography or radiography is ideal to image their presence. The source flux also provides unparalleled flexibility for future upgrades, including real time radiography where dynamic processes can be observed. A novel tomography detector has been designed using optical fibers and digital technology to provide a large dynamic range for reconstructions. Film radiography is also available for high resolution imaging applications. This paper summarizes the results of the design phase of this facility and the potential benefits to science and industry.« less

Neutronics performance and activation calculation of dense tungsten granular target for China-ADS

NASA Astrophysics Data System (ADS)

Zhang, Yaling; Li, Jianyang; Zhang, Xunchao; Cai, Hanjie; Yan, Xuesong; Yu, Lin; Fu, Fen; Lin, Ping; Gao, Xiaofei; Zhang, Zhilei; Zhang, Yanshi; Yang, Lei

2017-11-01

Spallation target, which constitutes the physical and functional interface between the high power accelerator and the subcritical core, is one of the most important components in Accelerator Driven Subcritical System (ADS). In this paper, we investigated the neutronics performance, the radiation damage and the activation of dense tungsten granular flow spallation target by using the Monte Carlo programs GMT and FLUKA at the proton energy of 250 MeV with a beam current of 10 mA . First, the leaking neutron yield, leaking neutron energy spectrum and laterally leaking neutron distribution at several time nodes and with different target parameters are explored. After that, the displacement per atom (DPA) and the helium/hydrogen production for tungsten grains and structural materials with stainless steel 316L are estimated. Finally, the radioactivity, residual dose rate and afterheat of granular target are presented. Results indicate that granule diameter below 1 cm and the beam profile diameter have negligible impact on neutronics performance, while the target diameter and volume fraction of grain have notable influence. The maximum DPA for target vessel (beam tube) is about 1.0 (1.6) DPA/year in bare target, and increased to 2.6 (2.8) DPA/year in fission environment. Average DPA for tungsten grains is relatively low. The decline rate of radioactivity and afterheat with cooling time grows with the decrease of the irradiation time.

Search for Time Reversal Violating Effects: R-Correlation Measurement in Neutron Decay.

PubMed

Bodek, K; Ban, G; Beck, M; Bialek, A; Bryś, T; Czarnecki, A; Fetscher, W; Gorel, P; Kirch, K; Kistryn, St; Kozela, A; Kuźniak, M; Lindroth, A; Naviliat-Cuncic, O; Pulut, J; Serebrov, A; Severijns, N; Stephan, E; Zejma, J

2005-01-01

An experiment aiming at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons begins data taking using the polarized cold neutron beam (FUNSPIN) from the Swiss Neutron Spallation Source (SINQ) at the Paul-Scherrer Institute, Villigen. A non-zero value of R due to the e(-) polarization component, which is perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal symmetry and thus physics beyond the Standard Model. Present status of the project and the results from analysis of the first data sample will be discussed.

Characterization of the new neutron imaging and materials science facility IMAT

NASA Astrophysics Data System (ADS)

Minniti, Triestino; Watanabe, Kenichi; Burca, Genoveva; Pooley, Daniel E.; Kockelmann, Winfried

2018-04-01

IMAT is a new cold neutron imaging and diffraction instrument located at the second target station of the pulsed neutron spallation source ISIS, UK. A broad range of materials science and materials testing areas will be covered by IMAT. We present the characterization of the imaging part, including the energy-selective and energy-dispersive imaging options, and provide the basic parameters of the radiography and tomography instrument. In particular, detailed studies on mono and bi-dimensional neutron beam flux profiles, neutron flux as a function of the neutron wavelength, spatial and energy dependent neutron beam uniformities, guide artifacts, divergence and spatial resolution, and neutron pulse widths are provided. An accurate characterization of the neutron beam at the sample position, located 56 m from the source, is required to optimize collection of radiographic and tomographic data sets and for performing energy-dispersive neutron imaging via time-of-flight methods in particular.

Monte Carlo simulation of neutron backscattering from concrete walls in the dense plasma focus laboratory of Bologna University.

PubMed

Frignani, M; Mostacci, D; Rocchi, F; Sumini, M

2005-01-01

Between 2001 and 2003 a 3.2 kJ dense plasma focus (DPF) device has been built at the Montecuccolino Laboratory of the Department of Energy, Nuclear and Environmental Control Engineering (DIENCA) of the University of Bologna. A DPF is a pulsed device in which deuterium nuclear fusion reactions can be obtained through the pinching effects of electromagnetic fields upon a dense plasma. The empirical scale law that governs the total D-D neutron yield from a single pulse of a DPF predicts for this machine a figure of approximately 10(7) fast neutrons per shot. The aim of the present work is to evaluate the role of backscattering of neutrons from the concrete walls surrounding the Montecuccolino DPF in total neutron yield measurements. The evaluation is performed by MCNP-5 simulations that are aimed at estimating the neutron spectra at a few points of interest in the laboratory, where neutron detectors will be placed during the experimental campaigns. Spectral information from the simulations is essential because the response of detectors is influenced by neutron energy. Comparisons are made with the simple r(-2) law, which holds for a DPF in infinite vacuum. The results from the simulations will ultimately be used both in the design and optimisation of the neutron detectors and in their final calibration and placement inside the laboratory.

DANCE : a 4[pi] barium fluoride detector for measuring neutron capture on unstable nuclei /.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ullmann, J. L.; Haight, Robert C.; Hunt, L. F.

2002-01-01

Measurements of neutron capture on unstable nuclei are important for studies of s-process nucleosynthesis, nuclear waste transmutation, and stewardship science. A 160-element, 4{pi} barium fluoride detector array, and associated neutron flight path, is being constructed to make capture measurements at the moderated neutron spallation source at LANSCE. Measurements can be made on as little as 1 mg of sample material over energies from near thermal to near 100 keV. The design of the DANCE array is described and neutron flux measurements from flight path commissioning are shown. The array is expected to be complete by the end of 2002.

Voss with Bonner Ball Neutron Detector Control Unit in Destiny laboratory

NASA Image and Video Library

2001-03-23

ISS002-E-5714 (23 March 2001) --- Astronaut James S. Voss, Expedition Two flight engineer, sets up the Bonner Ball Neutron Detector (BBND) in the Destiny laboratory. The BBND is connected to the Human Research Facility (HRF). This image was recorded with a digital still camera.

Design of a facility for the in situ measurement of catalytic reaction by neutron scattering spectroscopy

NASA Astrophysics Data System (ADS)

Tan, Shuai; Cheng, Yongqiang; Daemen, Luke L.; Lutterman, Daniel A.

2018-01-01

Catalysis is a critical enabling science for future energy needs. The next frontier of catalysis is to evolve from catalyst discovery to catalyst design, and for this next step to be realized, we must develop new techniques to better understand reaction mechanisms. To do this, we must connect catalytic reaction rates and selectivities to the kinetics, energetics, and dynamics of individual elementary steps and relate these to the structure and dynamics of the catalytic sites involved. Neutron scattering spectroscopies offer unique capabilities that are difficult or impossible to match by other techniques. The current study presents the development of a compact and portable instrumental design that enables the in situ investigation of catalytic samples by neutron scattering techniques. The developed apparatus was tested at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory and includes a gas handling panel that allows for computer hookups to control the panel externally and online measurement equipment such as coupled GC-FID/TCD (Gas Chromatography-Flame Ionization Detector/Thermal Conductivity Detector) and MS (Mass Spectrometry) to characterize offgassing while the sample is in the neutron scattering spectrometer. This system is flexible, modular, compact, and portable enabling its use for many types of gas-solid and liquid-solid reactions at the various beamlines housed at the SNS.

Modularized Parallel Neutron Instrument Simulation on the TeraGrid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Meili; Cobb, John W; Hagen, Mark E

2007-01-01

In order to build a bridge between the TeraGrid (TG), a national scale cyberinfrastructure resource, and neutron science, the Neutron Science TeraGrid Gateway (NSTG) is focused on introducing productive HPC usage to the neutron science community, primarily the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). Monte Carlo simulations are used as a powerful tool for instrument design and optimization at SNS. One of the successful efforts of a collaboration team composed of NSTG HPC experts and SNS instrument scientists is the development of a software facility named PSoNI, Parallelizing Simulations of Neutron Instruments. Parallelizing the traditional serialmore » instrument simulation on TeraGrid resources, PSoNI quickly computes full instrument simulation at sufficient statistical levels in instrument de-sign. Upon SNS successful commissioning, to the end of 2007, three out of five commissioned instruments in SNS target station will be available for initial users. Advanced instrument study, proposal feasibility evalua-tion, and experiment planning are on the immediate schedule of SNS, which pose further requirements such as flexibility and high runtime efficiency on fast instrument simulation. PSoNI has been redesigned to meet the new challenges and a preliminary version is developed on TeraGrid. This paper explores the motivation and goals of the new design, and the improved software structure. Further, it describes the realized new fea-tures seen from MPI parallelized McStas running high resolution design simulations of the SEQUOIA and BSS instruments at SNS. A discussion regarding future work, which is targeted to do fast simulation for automated experiment adjustment and comparing models to data in analysis, is also presented.« less

Raw neutron scattering data for strain measurement of hydraulically loaded granite and marble samples in triaxial stress state

DOE Data Explorer

Polsky, Yarom

2014-05-23

This entry contains raw data files from experiments performed on the Vulcan beamline at the Spallation Neutron Source at Oak Ridge National Laboratory using a pressure cell. Cylindrical granite and marble samples were subjected to confining pressures of either 0 psi or approximately 2500 psi and internal pressures of either 0 psi, 1500 psi or 2500 psi through a blind axial hole at the center of one end of the sample. The sample diameters were 1.5" and the sample lengths were 6". The blind hole was 0.25" in diameter and 3" deep. One set of experiments measured strains at points located circumferentially around the center of the sample with identical radii to determine if there was strain variability (this would not be expected for a homogeneous material based on the symmetry of loading). Another set of experiments measured load variation across the radius of the sample at a fixed axial and circumferential location. Raw neutron diffraction intensity files and experimental parameter descriptions are included.

2010 Neutron Review: ORNL Neutron Sciences Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bardoel, Agatha A; Counce, Deborah M; Ekkebus, Allen E

2011-06-01

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

Characterization of the Multi-Blade 10B-based detector at the CRISP reflectometer at ISIS for neutron reflectometry at ESS

NASA Astrophysics Data System (ADS)

Piscitelli, F.; Mauri, G.; Messi, F.; Anastasopoulos, M.; Arnold, T.; Glavic, A.; Höglund, C.; Ilves, T.; Lopez Higuera, I.; Pazmandi, P.; Raspino, D.; Robinson, L.; Schmidt, S.; Svensson, P.; Varga, D.; Hall-Wilton, R.

2018-05-01

The Multi-Blade is a Boron-10-based gaseous thermal neutron detector developed to face the challenge arising in neutron reflectometry at neutron sources. Neutron reflectometers are challenging instruments in terms of instantaneous counting rate and spatial resolution. This detector has been designed according to the requirements given by the reflectometers at the European Spallation Source (ESS) in Sweden. The Multi-Blade has been installed and tested on the CRISP reflectometer at the ISIS neutron and muon source in U.K.. The results on the detailed detector characterization are discussed in this manuscript.

Intense fusion neutron sources

NASA Astrophysics Data System (ADS)

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

2010-04-01

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

Improved neutron-gamma discrimination for a {sup 6}Li-glass neutron detector using digital signal analysis methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, C. L., E-mail: wangc@ornl.gov; Riedel, R. A.

2016-01-15

A {sup 6}Li-glass scintillator (GS20) based neutron Anger camera was developed for time-of-flight single-crystal diffraction instruments at Spallation Neutron Source. Traditional Pulse-Height Analysis (PHA) for Neutron-Gamma Discrimination (NGD) resulted in the neutron-gamma efficiency ratio (defined as NGD ratio) on the order of 10{sup 4}. The NGD ratios of Anger cameras need to be improved for broader applications including neutron reflectometers. For this purpose, six digital signal analysis methods of individual waveforms acquired from photomultiplier tubes were proposed using (i) charge integration, (ii) pulse-amplitude histograms, (iii) power spectrum analysis combined with the maximum pulse-amplitude, (iv) two event parameters (a{sub 1}, b{submore » 0}) obtained from a Wiener filter, (v) an effective amplitude (m) obtained from an adaptive least-mean-square filter, and (vi) a cross-correlation coefficient between individual and reference waveforms. The NGD ratios are about 70 times those from the traditional PHA method. Our results indicate the NGD capabilities of neutron Anger cameras based on GS20 scintillators can be significantly improved with digital signal analysis methods.« less

Student Tutorials II

NASA Astrophysics Data System (ADS)

Student Tutorials

2006-05-01

(Open to all conferees) Lunch followed by a tour of the Spallation Neutron Source and Center for Nanophase Materials at of Oak Ridge National Laboratory. Buses leave from the University of Tenessee-Knoxville Nielsen Physics Building.

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

DOE PAGES

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

2016-11-14

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roecker, Caleb; Bernstein, Adam; Marleau, Peter

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

Note: Versatile sample stick for neutron scattering experiments in high electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bartkowiak, M., E-mail: marek.bartkowiak@psi.ch; White, J. S.; Laboratory for Quantum Magnetism, Ecole Polytechnique Fédérale de Lausanne

2014-02-15

We present a versatile high voltage sample stick that fits into all cryomagnets and standard cryostats at the Swiss Spallation Neutron Source, Paul Scherrer Institut, and which provides a low effort route to neutron scattering experiments that combine electric field with low temperature and magnetic field. The stick allows for voltages up to 5 kV and can be easily adapted for different scattering geometries. We discuss the design consideration and thermal behavior of the stick, and give one example to showcase the abilities of the device.

Measurement of the absolute neutron beam polarization from a supermirror polarizer and the absolute efficiency of a neutron spin rotator for the NPDGamma experiment using a polarized 3He neutron spin-filter

NASA Astrophysics Data System (ADS)

Musgrave, M. M.; Baeßler, S.; Balascuta, S.; Barrón-Palos, L.; Blyth, D.; Bowman, J. D.; Chupp, T. E.; Cianciolo, V.; Crawford, C.; Craycraft, K.; Fomin, N.; Fry, J.; Gericke, M.; Gillis, R. C.; Grammer, K.; Greene, G. L.; Hamblen, J.; Hayes, C.; Huffman, P.; Jiang, C.; Kucuker, S.; McCrea, M.; Mueller, P. E.; Penttilä, S. I.; Snow, W. M.; Tang, E.; Tang, Z.; Tong, X.; Wilburn, W. S.

2018-07-01

Accurately measuring the neutron beam polarization of a high flux, large area neutron beam is necessary for many neutron physics experiments. The Fundamental Neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS) is a pulsed neutron beam that was polarized with a supermirror polarizer for the NPDGamma experiment. The polarized neutron beam had a flux of ∼ 109 neutrons per second per cm2 and a cross sectional area of 10 × 12 cm2. The polarization of this neutron beam and the efficiency of a RF neutron spin rotator installed downstream on this beam were measured by neutron transmission through a polarized 3He neutron spin-filter. The pulsed nature of the SNS enabled us to employ an absolute measurement technique for both quantities which does not depend on accurate knowledge of the phase space of the neutron beam or the 3He polarization in the spin filter and is therefore of interest for any experiments on slow neutron beams from pulsed neutron sources which require knowledge of the absolute value of the neutron polarization. The polarization and spin-reversal efficiency measured in this work were done for the NPDGamma experiment, which measures the parity violating γ-ray angular distribution asymmetry with respect to the neutron spin direction in the capture of polarized neutrons on protons. The experimental technique, results, systematic effects, and applications to neutron capture targets are discussed.

Spallation yield of neutrons produced in thick lead target bombarded with 250 MeV protons

NASA Astrophysics Data System (ADS)

Chen, L.; Ma, F.; Zhanga, X. Y.; Ju, Y. Q.; Zhang, H. B.; Ge, H. L.; Wang, J. G.; Zhou, B.; Li, Y. Y.; Xu, X. W.; Luo, P.; Yang, L.; Zhang, Y. B.; Li, J. Y.; Xu, J. K.; Liang, T. J.; Wang, S. L.; Yang, Y. W.; Gu, L.

2015-01-01

The neutron yield from thick target of Pb irradiated with 250 MeV protons has been studied experimentally. The neutron production was measured with the water-bath gold method. The thermal neutron distributions in the water were determined according to the measured activities of Au foils. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data. It was found out that the Au foils with cadmium cover significantly changed the spacial distribution of the thermal neutron field. The corrected neutron yield was deduced to be 2.23 ± 0.19 n/proton by considering the influence of the Cd cover on the thermal neutron flux.

Aerodynamic laser-heated contactless furnace for neutron scattering experiments at elevated temperatures

NASA Astrophysics Data System (ADS)

Landron, Claude; Hennet, Louis; Coutures, Jean-Pierre; Jenkins, Tudor; Alétru, Chantal; Greaves, Neville; Soper, Alan; Derbyshire, Gareth

2000-04-01

Conventional radiative furnaces require sample containment that encourages contamination at elevated temperatures and generally need windows which restrict the entrance and exit solid angles required for diffraction and scattering measurements. We describe a contactless windowless furnace based on aerodynamic levitation and laser heating which has been designed for high temperature neutron scattering experiments. Data from initial experiments are reported for crystalline and amorphous oxides at temperatures up to 1900 °C, using the spallation neutron source ISIS together with our laser-heated aerodynamic levitator. Accurate reproduction of thermal expansion coefficients and radial distribution functions have been obtained, demonstrating the utility of aerodynamic levitation methods for neutron scattering methods.

The Manuel Lujan, Jr. Neutron Scattering Center, LANSCE experiment reports: 1990 Run Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiStravolo, M.A.

1991-10-01

This year was the third in which LANSCE ran a formal user program. A call for proposals was issued before the scheduled run cycles, and experiment proposals were submitted by scientists from universities, industry, and other research facilities around the world. An external program advisory committee, which LANSCE shares with the Intense Pulsed Neutron Source (IPNS), Argonne National Laboratory examined the proposals and made recommendations. At LANSCE, neutrons are produced by spallation when a pulsed, 800-MeV proton beam impinges on a tungsten target. The proton pulses are provided by the Clinton P. Anderson Meson Physics Facility (LAMPF) accelerator and anmore » associated Proton Storage Ring (PSR), which can alter the intensity, time structure, and repetition rate of the pulses. The LAMPF protons of Line D are shared between the LANSCE target and the Weapons Neutron Research facility, which results in LANSCE spectrometers being available to external users for unclassified research about 80% of each six-month LAMPF run cycle. Measurements of interest to the Los Alamos National Laboratory may also be performed and may occupy up to an additional 20% of the available beam time. These experiments are reviewed by an internal program advisory committee. One hundred thirty-four proposals were submitted for unclassified research and twelve proposals for research of a programmatic nature to the Laboratory. Our definition of beam availability is when the proton current from the PSR exceeds 50% of the planned value. The PSR ran at 65{mu}A current (average) at 20 Hz for most of 1990. All of the scheduled experiments were performed and experiments in support of the LANSCE research program were accomplished during the discretionary periods.« less

Prompt fission neutron spectra from fission induced by 1 to 8 MeV neutrons on U235 and Pu239 using the double time-of-flight technique

NASA Astrophysics Data System (ADS)

Noda, S.; Haight, R. C.; Nelson, R. O.; Devlin, M.; O'Donnell, J. M.; Chatillon, A.; Granier, T.; Bélier, G.; Taieb, J.; Kawano, T.; Talou, P.

2011-03-01

Prompt fission neutron spectra from U235 and Pu239 were measured for incident neutron energies from 1 to 200 MeV at the Weapons Neutron Research facility (WNR) of the Los Alamos Neutron Science Center, and the experimental data were analyzed with the Los Alamos model for the incident neutron energies of 1-8 MeV. A CEA multiple-foil fission chamber containing deposits of 100 mg U235 and 90 mg Pu239 detected fission events. Outgoing neutrons were detected by the Fast Neutron-Induced γ-Ray Observer array of 20 liquid organic scintillators. A double time-of-flight technique was used to deduce the neutron incident energies from the spallation target and the outgoing energies from the fission chamber. These data were used for testing the Los Alamos model, and the total kinetic energy parameters were optimized to obtain a best fit to the data. The prompt fission neutron spectra were also compared with the Evaluated Nuclear Data File (ENDF/B-VII.0). We calculate average energies from both experimental and calculated fission neutron spectra.

Improvement of analytical capabilities of neutron activation analysis laboratory at the Colombian Geological Survey

NASA Astrophysics Data System (ADS)

Parrado, G.; Cañón, Y.; Peña, M.; Sierra, O.; Porras, A.; Alonso, D.; Herrera, D. C.; Orozco, J.

2016-07-01

The Neutron Activation Analysis (NAA) laboratory at the Colombian Geological Survey has developed a technique for multi-elemental analysis of soil and plant matrices, based on Instrumental Neutron Activation Analysis (INAA) using the comparator method. In order to evaluate the analytical capabilities of the technique, the laboratory has been participating in inter-comparison tests organized by Wepal (Wageningen Evaluating Programs for Analytical Laboratories). In this work, the experimental procedure and results for the multi-elemental analysis of four soil and four plant samples during participation in the first round on 2015 of Wepal proficiency test are presented. Only elements with radioactive isotopes with medium and long half-lives have been evaluated, 15 elements for soils (As, Ce, Co, Cr, Cs, Fe, K, La, Na, Rb, Sb, Sc, Th, U and Zn) and 7 elements for plants (Br, Co, Cr, Fe, K, Na and Zn). The performance assessment by Wepal based on Z-score distributions showed that most results obtained |Z-scores| ≤ 3.

Pulsed Neutron Powder Diffraction for Materials Science

NASA Astrophysics Data System (ADS)

Kamiyama, T.

2008-03-01

The accelerator-based neutron diffraction began in the end of 60's at Tohoku University which was succeeded by the four spallation neutron facilities with proton accelerators at the High Energy Accelerator Research Organization (Japan), Argonne National Laboratory and Los Alamos Laboratory (USA), and Rutherford Appleton Laboratory (UK). Since then, the next generation source has been pursued for 20 years, and 1MW-class spallation neutron sources will be appeared in about three years at the three parts of the world: Japan, UK and USA. The joint proton accelerator project (J-PARC), a collaborative project between KEK and JAEA, is one of them. The aim of the talk is to describe about J-PARC and the neutron diffractometers being installed at the materials and life science facility of J-PARC. The materials and life science facility of J-PARC has 23 neutron beam ports and will start delivering the first neutron beam of 25 Hz from 2008 May. Until now, more than 20 proposals have been reviewed by the review committee, and accepted proposal groups have started to get fund. Those proposals include five polycrystalline diffractometers: a super high resolution powder diffractometer (SHRPD), a 0.2%-resolution powder diffractometer of Ibaraki prefecture (IPD), an engineering diffractometers (Takumi), a high intensity S(Q) diffractometer (VSD), and a high-pressure dedicated diffractometer. SHRPD, Takumi and IPD are being designed and constructed by the joint team of KEK, JAEA and Ibaraki University, whose member are originally from the KEK powder group. These three instruments are expected to start in 2008. VSD is a super high intensity diffractometer with the highest resolution of Δd/d = 0.3%. VSD can measure rapid time-dependent phenomena of crystalline materials as well as glass, liquid and amorphous materials. The pair distribution function will be routinely obtained by the Fourier transiformation of S(Q) data. Q range of VSD will be as wide as 0.01 Å-1

Experimental demonstration of a compact epithermal neutron source based on a high power laser

NASA Astrophysics Data System (ADS)

Mirfayzi, S. R.; Alejo, A.; Ahmed, H.; Raspino, D.; Ansell, S.; Wilson, L. A.; Armstrong, C.; Butler, N. M. H.; Clarke, R. J.; Higginson, A.; Kelleher, J.; Murphy, C. D.; Notley, M.; Rusby, D. R.; Schooneveld, E.; Borghesi, M.; McKenna, P.; Rhodes, N. J.; Neely, D.; Brenner, C. M.; Kar, S.

2017-07-01

Epithermal neutrons from pulsed-spallation sources have revolutionised neutron science allowing scientists to acquire new insight into the structure and properties of matter. Here, we demonstrate that laser driven fast (˜MeV) neutrons can be efficiently moderated to epithermal energies with intrinsically short burst durations. In a proof-of-principle experiment using a 100 TW laser, a significant epithermal neutron flux of the order of 105 n/sr/pulse in the energy range of 0.5-300 eV was measured, produced by a compact moderator deployed downstream of the laser-driven fast neutron source. The moderator used in the campaign was specifically designed, by the help of MCNPX simulations, for an efficient and directional moderation of the fast neutron spectrum produced by a laser driven source.

Astrophysical Li-7 as a product of big bang nucleosynthesis and galactic cosmic-ray spallation

NASA Technical Reports Server (NTRS)

Olive, Keith A.; Schramm, David N.

1992-01-01

The astrophysical Li-7 abundance is considered to be largely primordial, while the Be and B abundances are thought to be due to galactic cosmic ray (GCR) spallation reactions on top of a much smaller big bang component. But GCR spallation should also produce Li-7. As a consistency check on the combination of big bang nucleosynthesis and GCR spallation, the Be and B data from a sample of hot population II stars is used to subtract from the measured Li-7 abundance an estimate of the amount generated by GCR spallation for each star in the sample, and then to add to this baseline an estimate of the metallicity-dependent augmentation of Li-7 due to spallation. The singly reduced primordial Li-7 abundance is still consistent with big bang nucleosynthesis, and a single GCR spallation model can fit the Be, B, and corrected Li-7 abundances for all the stars in the sample.

Workshop on Probing Frontiers in Matter with Neutron Scattering, Wrap-up Session Chaired by John C. Browne on December 14, 1997, at Fuller Lodge, Los Alamos, New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mezei, F.; Thompson, J.

1998-12-01

The Workshop on Probing Frontiers in Matter with Neutron Scattering consisted of a series of lectures and discussions about recent highlights in neutron scattering. In this report, we present the transcript of the concluding discussion session (wrap-up session) chaired by John C. Browne, Director of Los Alamos National Laboratory. The workshop had covered a spectrum of topics ranging from high T{sub c} superconductivity to polymer science, from glasses to molecular biology, a broad review aimed at identifying trends and future needs in condensed matter research. The focus of the wrap-up session was to summarize the workshop participants' views on developmentsmore » to come. Most of the highlights presented during the workshop were the result of experiments performed at the leading reactor-based neutron scattering facilities. However, recent advances with very high power accelerators open up opportunities to develop new approaches to spallation technique that could decisively advance neutron scattering research in areas for which reactor sources are today by far the best choice. The powerful combination of neutron scattering and increasingly accurate computer modeling emerged as another area of opportunity for research in the coming decades.« less

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

NASA Technical Reports Server (NTRS)

Smialek, James L.

2010-01-01

For some time the oxidation community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cool down, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of thermal barrier coatings (TBCs) refer to this process. It is most apparent for relatively adherent alumina scales that have survived initial cool down in a dry environment, have built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sensitive zone" can be described that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement. Hydrogen is derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen-induced effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic-tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen detection as a reaction product or interfacial species. Further support is provided by critical experiments that recreate the moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H 2-containing atmospheres or cathodic hydrogen charging. Accordingly, they strongly indicate that interfacial hydrogen, derived from moisture, is the key chemical species accounting for delayed alumina scale spallation.

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer.

PubMed

Benafan, O; Padula, S A; Skorpenske, H D; An, K; Vaidyanathan, R

2014-10-01

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel(®) 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N·m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ∼1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes.

Design and implementation of a multiaxial loading capability during heating on an engineering neutron diffractometer

NASA Astrophysics Data System (ADS)

Benafan, O.; Padula, S. A.; Skorpenske, H. D.; An, K.; Vaidyanathan, R.

2014-10-01

A gripping capability was designed, implemented, and tested for in situ neutron diffraction measurements during multiaxial loading and heating on the VULCAN engineering materials diffractometer at the spallation neutron source at Oak Ridge National Laboratory. The proposed capability allowed for the acquisition of neutron spectra during tension, compression, torsion, and/or complex loading paths at elevated temperatures. The design consisted of age-hardened, Inconel® 718 grips with direct attachment to the existing MTS load frame having axial and torsional capacities of 100 kN and 400 N.m, respectively. Internal cooling passages were incorporated into the gripping system for fast cooling rates during high temperature experiments up to ˜1000 K. The specimen mounting couplers combined a threaded and hexed end-connection for ease of sample installation/removal without introducing any unwanted loads. Instrumentation of this capability is documented in this work along with various performance parameters. The gripping system was utilized to investigate deformation in NiTi shape memory alloys under various loading/control modes (e.g., isothermal, isobaric, and cyclic), and preliminary results are presented. The measurements facilitated the quantification of the texture, internal strain, and phase fraction evolution in NiTi shape memory alloys under various loading/control modes.

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

PubMed

Dilmanian, F A; Lidofsky, L J; Stamatelatos, I; Kamen, Y; Yasumura, S; Vartsky, D; Pierson, R N; Weber, D A; Moore, R I; Ma, R

1998-02-01

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.

Phonon characteristics of high {Tc} superconductors from neutron Doppler broadening measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trela, W.J.; Kwei, G.H.; Lynn, J.E.

Statistical information on the phonon frequency spectrum of materials can be measured by neutron transmission techniques if they contain nuclei with low energy resonances, narrow enough to be Doppler-broadened, in their neutron cross sections. The authors have carried out some measurements using this technique for materials of the lanthanum barium cuprate class, La{sub 2{minus}x}Ba{sub x}CuO{sub 4}. Two samples with slightly different concentrations of oxygen, one being superconductive, the other not, were examined. Pure lanthanum cuprate was also measured. Lanthanum, barium and copper all have relatively low energy narrow resonances. Thus it should be possible to detect differences in the phononsmore » carried by different kinds of atom in the lattice. Neutron cross section measurements have been made with high energy resolution and statistical precision on the 59m flight path of LANSCE, the pulsed spallation neutron source at Los Alamos National Laboratory. Measurements on all three materials were made over a range of temperatures from 15K to 300K, with small steps through the critical temperature region near 27K. No significant changes in the mean phonon energy of the lanthanum atoms were observed near the critical temperature of the super-conducting material. It appears however that the mean phonon energy of lanthanum in the superconductor is considerably higher than that in the non-superconductors. The samples used in this series of experiments were too thin in barium and copper to determine anything significant about their phonon spectra.« less

How does spallation microdamage nucleate in bulk amorphous alloys under shock loading?

NASA Astrophysics Data System (ADS)

Huang, X.; Ling, Z.; Zhang, H. S.; Ma, J.; Dai, L. H.

2011-11-01

Specially designed plate-impact experiments have been conducted on a Zr-based amorphous alloy using a single-stage light gas gun. To understand the microdamage nucleation process in the material, the samples are subjected to dynamic tensile loadings of identical amplitude (˜ 3.18 GPa) but with different durations (83-201 ns). A cellular pattern with an equiaxed shape is observed on the spallation surface, which shows that spallation in the tested amorphous alloy is a typical ductile fracture and that microvoids have been nucleated during the process. Based on the observed fracture morphologies of the spallation surface and free-volume theory, we propose a microvoid nucleation model of bulk amorphous alloys. It is found that nucleation of microvoids at the early stage of spallation in amorphous alloys results from diffusion and coalescence of free volume, and that high mean tensile stress plays a dominant role in microvoid nucleation.

Spallation reaction study for the long-lived fission product 107Pd

NASA Astrophysics Data System (ADS)

Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Ahn, DeukSoon; Aikawa, Masayuki; Ando, Takashi; Araki, Shouhei; Chen, Sidong; Nobuyuki, Chiga; Doornenbal, Pieter; Fukuda, Naoki; Isobe, Tadaaki; Kawakami, Shunsuke; Kawase, Shoichiro; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shunpei; Kubono, Shigeru; Maeda, Yukie; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shin'ichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakamura, Takashi; Nakano, Keita; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Taniuchi, Ryo; Togano, Yasuhiro; Tsubota, Junichi; Uesaka, Meiko; Watanabe, Yasushi; Watanabe, Yukinobu; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-02-01

Spallation reactions for the long-lived fission product 107Pd have been studied for the purpose of nuclear waste transmutation. The cross sections on the proton- and deuteron-induced spallation were obtained at 196 and 118 MeV/nucleon in inverse kinematics at the RIKEN Radioactive Isotope Beam Factory. Both the target and energy dependences of cross sections have been investigated systematically. It was found that the proton-induced cross sections at 196 MeV/nucleon are close to those for deuteron obtained at 118 MeV/nucleon for the light-mass products. The experimental data are compared with the SPACS semi-empirical parameterization and the PHITS calculations including both the intranuclear cascade and evaporation processes. Our data give a design goal of proton/deuteron flux for the transmutation of 107Pd using the spallation reaction. In addition, it is found that the spallation reaction at 118 MeV/nucleon may have an advantage over the 107Pd transmutation because of the low production of other long-lived radioactive isotopes.

A Survey of Students from the National School on Neutron and X-ray Scattering: Communication Habits and Preferences

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryant, Rebecca

2010-12-01

Oak Ridge National Laboratory (ORNL) offers the scientific community unique access to two types of world-class neutron sources at a single site - the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR). The 85-MW HFIR provides one of the highest steady-state neutron fluxes of any research reactor in the world. And the SNS is one of the world's most intense pulse neutron beams. Management of these resources is the responsibility of the Neutron Sciences Directorate (NScD). NScD started conducting the National School on Neutron and X-ray Scattering (NXS) in conjunction with the Advanced Photon Source (APS) atmore » Argonne National Laboratory in 2007. This survey was conducted to determine the most effective ways to reach students with information about what SNS and HFIR offer the scientific community, including content and communication vehicles. The emphasis is on gaining insights into compelling messages and the most effective channels, e.g., Web sites and social media, for communicating with students about neutron science The survey was conducted in two phases using a classic qualitative investigation to confirm language and content followed by a survey designed to quantify issues, assumptions, and working hypotheses. Phase I consisted of a focus group in late June 2010 with students attending NXS. The primary intent of the group was to inform development of an online survey. Phase two consisted of an online survey that was developed and pre-tested in July 2010 and launched on August 9, 2010 and remained in the field until September 9, 2010. The survey achieved an overall response rate of 48% for a total of 157 completions. The objective of this study is to determine the most effective ways to reach students with information about what SNS and HFIR offer the scientific community, including content and communication vehicles. The emphasis is on gaining insights into compelling messages and the most effective channels, e.g., Web sites, social

Design and verification of the shielding around the new Neutron Standards Laboratory (LPN) at CIEMAT.

PubMed

Méndez-Villafañe, R; Guerrero, J E; Embid, M; Fernández, R; Grandio, R; Pérez-Cejuela, P; Márquez, J L; Alvarez, F; Ortego, P

2014-10-01

The construction of the new Neutron Standards Laboratory at CIEMAT (Laboratorio de Patrones Neutrónicos) has been finalised and is ready to provide service. The facility is an ∼8 m×8 m×8 m irradiation vault, following the International Organization for Standardization 8529 recommendations. It relies on several neutron sources: a 5-GBq (5.8× 10(8) s(-1)) (252)Cf source and two (241)Am-Be neutron sources (185 and 11.1 GBq). The irradiation point is located 4 m over the ground level and in the geometrical centre of the room. Each neutron source can be moved remotely from its storage position inside a water pool to the irradiation point. Prior to this, an important task to design the neutron shielding and to choose the most appropriate materials has been developed by the Radiological Security Unit and the Ionizing Radiations Metrology Laboratory. MCNPX was chosen to simulate the irradiation facility. With this information the walls were built with a thickness of 125 cm. Special attention was put on the weak points (main door, air conditioning system, etc.) so that the ambient dose outside the facility was below the regulatory limits. Finally, the Radiation Protection Unit carried out a set of measurements in specific points around the installation with an LB6411 neutron monitor and a Reuter-Stokes high-pressure ion chamber to verify experimentally the results of the simulation. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Neutron Characterization for Additive Manufacturing

NASA Technical Reports Server (NTRS)

Watkins, Thomas; Bilheux, Hassina; An, Ke; Payzant, Andrew; DeHoff, Ryan; Duty, Chad; Peter, William; Blue, Craig; Brice, Craig A.

2013-01-01

Oak Ridge National Laboratory (ORNL) is leveraging decades of experience in neutron characterization of advanced materials together with resources such as the Spallation Neutron Source (SNS) and the High Flux Isotope Reactor (HFIR) shown in Fig. 1 to solve challenging problems in additive manufacturing (AM). Additive manufacturing, or three-dimensional (3-D) printing, is a rapidly maturing technology wherein components are built by selectively adding feedstock material at locations specified by a computer model. The majority of these technologies use thermally driven phase change mechanisms to convert the feedstock into functioning material. As the molten material cools and solidifies, the component is subjected to significant thermal gradients, generating significant internal stresses throughout the part (Fig. 2). As layers are added, inherent residual stresses cause warping and distortions that lead to geometrical differences between the final part and the original computer generated design. This effect also limits geometries that can be fabricated using AM, such as thin-walled, high-aspect- ratio, and overhanging structures. Distortion may be minimized by intelligent toolpath planning or strategic placement of support structures, but these approaches are not well understood and often "Edisonian" in nature. Residual stresses can also impact component performance during operation. For example, in a thermally cycled environment such as a high-pressure turbine engine, residual stresses can cause components to distort unpredictably. Different thermal treatments on as-fabricated AM components have been used to minimize residual stress, but components still retain a nonhomogeneous stress state and/or demonstrate a relaxation-derived geometric distortion. Industry, federal laboratory, and university collaboration is needed to address these challenges and enable the U.S. to compete in the global market. Work is currently being conducted on AM technologies at the ORNL

A novel small-angle neutron scattering detector geometry

PubMed Central

Kanaki, Kalliopi; Jackson, Andrew; Hall-Wilton, Richard; Piscitelli, Francesco; Kirstein, Oliver; Andersen, Ken H.

2013-01-01

A novel 2π detector geometry for small-angle neutron scattering (SANS) applications is presented and its theoretical performance evaluated. Such a novel geometry is ideally suited for a SANS instrument at the European Spallation Source (ESS). Motivated by the low availability and high price of 3He, the new concept utilizes gaseous detectors with 10B as the neutron converter. The shape of the detector is inspired by an optimization process based on the properties of the conversion material. Advantages over the detector geometry traditionally used on SANS instruments are discussed. The angular and time resolutions of the proposed detector concept are shown to satisfy the requirements of the particular SANS instrument. PMID:24046504

Immersive Visual Analytics for Transformative Neutron Scattering Science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Steed, Chad A; Daniel, Jamison R; Drouhard, Margaret

The ORNL Spallation Neutron Source (SNS) provides the most intense pulsed neutron beams in the world for scientific research and development across a broad range of disciplines. SNS experiments produce large volumes of complex data that are analyzed by scientists with varying degrees of experience using 3D visualization and analysis systems. However, it is notoriously difficult to achieve proficiency with 3D visualizations. Because 3D representations are key to understanding the neutron scattering data, scientists are unable to analyze their data in a timely fashion resulting in inefficient use of the limited and expensive SNS beam time. We believe a moremore » intuitive interface for exploring neutron scattering data can be created by combining immersive virtual reality technology with high performance data analytics and human interaction. In this paper, we present our initial investigations of immersive visualization concepts as well as our vision for an immersive visual analytics framework that could lower the barriers to 3D exploratory data analysis of neutron scattering data at the SNS.« less

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.

Development of a compact in situ polarized ³He neutron spin filter at Oak Ridge National Laboratory.

PubMed

Jiang, C Y; Tong, X; Brown, D R; Chi, S; Christianson, A D; Kadron, B J; Robertson, J L; Winn, B L

2014-07-01

We constructed a compact in situ polarized (3)He neutron spin filter based on spin-exchange optical pumping which is capable of continuous pumping of the (3)He gas while the system is in place in the neutron beam on an instrument. The compact size and light weight of the system simplifies its utilization on various neutron instruments. The system has been successfully tested as a neutron polarizer on the triple-axis spectrometer (HB3) and the hybrid spectrometer (HYSPEC) at Oak Ridge National Laboratory. Over 70% (3)He polarization was achieved and maintained during the test experiments. Over 90% neutron polarization and an average of 25% transmission for neutrons of 14.7 meV and 15 meV was also obtained.

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

DOEpatents

Parkin, Don M.; Dudey, Norman D.

1976-01-01

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

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.

Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions ofmore » neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B 4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

Neutron multiplicity measurements with 3He alternative: Straw neutron detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukhopadhyay, Sanjoy; Wolff, Ronald; Detwiler, Ryan

Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as ‘‘ship effect ’’) and to the complicated nature of the neutron scattering in that environment. A prototype neutron detector was built using 10B as the converter in a special form factor called ‘‘straws’’ that would address the above problems by looking into the details of multiplicity distributions of neutrons originatingmore » from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B 4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

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

DOE PAGES

Mukhopadhyay, Sanjoy; Wolff, Ronald S.; Meade, John A.; ...

2015-01-27

Counting neutrons emitted by special nuclear material (SNM) and differentiating them from the background neutrons of various origins is the most effective passive means of detecting SNM. Unfortunately, neutron detection, counting, and partitioning in a maritime environment are complex due to the presence of high-multiplicity spallation neutrons (commonly known as “ship effect”) and to the complicated nature of the neutron scattering in that environment. In this study, a prototype neutron detector was built using 10B as the converter in a special form factor called “straws” that would address the above problems by looking into the details of multiplicity distributions ofmore » neutrons originating from a fissioning source. This paper describes the straw neutron multiplicity counter (NMC) and assesses the performance with those of a commercially available fission meter. The prototype straw neutron detector provides a large-area, efficient, lightweight, more granular (than fission meter) neutron-responsive detection surface (to facilitate imaging) to enhance the ease of application of fission meters. Presented here are the results of preliminary investigations, modeling, and engineering considerations leading to the construction of this prototype. This design is capable of multiplicity and Feynman variance measurements. This prototype may lead to a near-term solution to the crisis that has arisen from the global scarcity of 3He by offering a viable alternative to fission meters. This paper describes the work performed during a 2-year site-directed research and development (SDRD) project that incorporated straw detectors for neutron multiplicity counting. The NMC is a two-panel detector system. We used 10B (in the form of enriched boron carbide: 10B 4C) for neutron detection instead of 3He. In the first year, the project worked with a panel of straw neutron detectors, investigated its characteristics, and developed a data acquisition (DAQ) system to collect

Observed diurnal variations in Mars Science Laboratory Dynamic Albedo of Neutrons passive mode data

NASA Astrophysics Data System (ADS)

Tate, C. G.; Moersch, J.; Jun, I.; Mitrofanov, I.; Litvak, M.; Boynton, W. V.; Drake, D.; Fedosov, F.; Golovin, D.; Hardgrove, C.; Harshman, K.; Kozyrev, A. S.; Kuzmin, R.; Lisov, D.; Maclennan, E.; Malakhov, A.; Mischna, M.; Mokrousov, M.; Nikiforov, S.; Sanin, A. B.; Starr, R.; Vostrukhin, A.

2018-06-01

The Mars Science Laboratory Dynamic Albedo of Neutrons (DAN) experiment measures the martian neutron leakage flux in order to estimate the amount of water equivalent hydrogen present in the shallow regolith. When DAN is operating in passive mode, it is sensitive to neutrons produced through the interactions of galactic cosmic rays (GCR) with the regolith and atmosphere and neutrons produced by the rover's Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). During the mission, DAN passive mode data were collected over the full diurnal cycle at the locations known as Rocknest (sols 60-100) and John Klein (sols 166-272). A weak, but unexpected, diurnal variation was observed in the neutron count rates reported at these locations. We investigate different hypotheses that could be causing these observed variations. These hypotheses are variations in subsurface temperature, atmospheric pressure, the exchange of water vapor between the atmosphere and regolith, and instrumental effects on the neutron count rates. Our investigation suggests the most likely factors contributing to the observed diurnal variations in DAN passive data are instrumental effects and time-variable preferential shielding of alpha particles, with other environmental effects only having small contributions.

The very low angle detector for high-energy inelastic neutron scattering on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

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

2008-05-01

The Very Low Angle Detector (VLAD) bank has been installed on the VESUVIO spectrometer at the ISIS spallation neutron source. The new device allows for high-energy inelastic neutron scattering measurements, at energies above 1 eV, maintaining the wave vector transfer lower than 10Å-1. This opens a still unexplored region of the kinematical (q, ω) space, enabling new and challenging experimental investigations in condensed matter. This paper describes the main instrumental features of the VLAD device, including instrument design, detector response, and calibration procedure.

Moisture-Induced Spallation and Interfacial Hydrogen Embrittlement of Alumina Scales

NASA Technical Reports Server (NTRS)

Smialek, James L.

2005-01-01

Thermal expansion mismatch stresses and interfacial sulfur activity are the major factors producing primary Al2O3 scale spallation on high temperature alloys. However, moisture-induced delayed spallation appears as a secondary, but often dramatic, illustration of an additional mechanistic detail. A historical review of delayed failure of alumina scales and TBC s on superalloys is presented herein. Similarities with metallic phenomena suggest that hydrogen embrittlement from ambient humidity, resulting from the reaction Al+3H2O=Al(OH)3+3H(+)+3e(-), is the operative mechanism. This proposal was tested by standard cathodic hydrogen charging in 1N H2SO4, applied to Rene N5 pre-oxidized at 1150 C for 1000 1-hr cycles, and monitored by weight change, induced current, and microstructure. Here cathodic polarization at -2.0 V abruptly stripped mature Al2O3 scales at the oxide-metal interface. Anodic polarization at +2.0 V, however, produced alloy dissolution. Finally, with no applied voltage, the electrolyte alone produced neither scale spallation nor alloy dissolution. These experiments thus highlight the detrimental effects of hydrogen charging on alumina scale adhesion. It is proposed that interfacial hydrogen embrittlement is produced by moist air and is the root cause of both moisture-induced, delayed scale spallation and desktop TBC failures.

Probing the Hydrogen Sublattice of FeHx with High-Pressure Neutron Diffraction

NASA Astrophysics Data System (ADS)

Murphy, C. A.; Guthrie, M.; Boehler, R.; Somayazulu, M.; Fei, Y.; Molaison, J.; dos Santos, A. M.

2013-12-01

The combination of seismic, cosmochemical, and mineral physics observations have revealed that Earth's iron-rich core must contain some light elements, such as hydrogen, carbon, oxygen, silicon, and/or sulfur. Therefore, understanding the influence of these light elements on the structural, thermoelastic, and electronic properties of iron is important for constraining the composition of this remote layer of the Earth and, in turn, providing constraints on planetary differentiation and core formation models. The high-pressure structural and magnetic properties of iron hydride (FeHx) have previously been studied using synchrotron x-ray diffraction and Mössbauer spectroscopy. Such experiments revealed that the double hexagonal close-packed (dhcp) structure of FeHx is stable above a pressure of ~5 GPa and up to at least 80 GPa at 300 K [1]. In addition, dhcp-FeHx is ferromagnetic at low-pressures, but undergoes a magnetic collapse around 22 GPa [2]. X-ray experiments provide valuable insight into the properties of FeHx, but such techniques are largely sensitive to the iron component because it is difficult to detect the hydrogen sublattice with x-rays. Therefore, neutron diffraction has been used to investigate metastable FeHx, which is formed by quenching the high-pressure phase to liquid nitrogen temperatures and probing the sample at ambient pressure [3]. However, such neutron experiments have been limited to formation pressures below 10 GPa, and cannot be performed at ambient temperature. Here we present the first in-situ investigation of FeHx at 300 K using high-pressure neutron diffraction experiments performed at the Spallation Neutrons and Pressure Diffractometer (SNAP) instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. In order to achieve pressures of ~50 GPa, we loaded iron samples with a hydrogen gas pressure medium into newly designed large-volume panoramic diamond-anvil cells (DACs) for neutron diffraction experiments [4; 5]. We

Neutronics Studies for the Nab Experiment

NASA Astrophysics Data System (ADS)

Scott, Elizabeth; Nab Collaboration

2017-09-01

The Nab experiment at the Spallation Neutron Source at ORNL aims to measure the neutron beta decay electron-neutrino correlation coefficient ``a'' and the Fierz interference term ``b'' with competitive precision. In Nab, the parameter ``a'' is extracted from the proton momentum and electron energy using an asymmetric magnetic spectrometer and two large-area highly pixelated Si detectors . To achieve 10-3 accuracy, there must be low background rates compared to our 1 kHz signal rates. The background is primarily reduced by using coincidence detection of the electron and photon from the decay. However, further reduction is still necessary. Neutron and gamma rates in the Si detectors can lead to false coincidences. The majority of this background radiation can be reduced by well designed collimation and shielding. The collimation design was done with McStas and the background shielding with MCNP6 (Monte Carlo N-Particle 6). Neutrons are absorbed by 6Li -loaded materials or borated polyethylene and gammas close to spectrometer with non magnetic materials such as lead and stainless steel. I will present the shielding design and MCNP6 results.

Oxidative Recession, Sulfur Release, and Al203 Spallation for Y-Doped Alloys

NASA Technical Reports Server (NTRS)

Smialek, James L.

2001-01-01

Second-order spallation phenomena have been noted for Y-doped Rene'N5 after long term oxidation at 1150 degrees C. The reason for this behavior has not been conclusively identified. A mass equivalence analysis has shown that the surface recession resulting from oxidation has the potential of releasing about 0.15 monolayer of sulfur for every 1 mg/sq cm of oxygen reacted for an alloy containing 5 ppmw of sulfur. This amount is significant in comparison to levels that have been shown to result in first-order spallation behavior for undoped alloys. Oxidative recession is therefore speculated to be a contributing source of sulfur and second-order spallation for Y-doped alloys.

Investigation of Monodisperse Dendrimeric Polysaccharide Nanoparticle Dispersions Using Small Angle Neutron Scattering

NASA Astrophysics Data System (ADS)

Atkinson, John; Nickels, Jonathan; Papp-Szabo, Erzsi; Katsaras, John; Dutcher, John

2015-03-01

Phytoglycogen is a highly branched polysaccharide that is very similar to the energy storage molecule glycogen. We have isolated monodisperse phytoglycogen nanoparticles from corn and these particles are attractive for applications in the cosmetic, food and beverage, and biomedical industries. Many of these promising applications are due to the special interaction between the nanoparticles and water, which results in: (1) high solubility; (2) low viscosity and high stability in aqueous dispersions; and (3) a remarkable capacity to sequester and retain water. Our rheology measurements indicate that the nanoparticles behave like hard spheres in water, with the viscosity diverging for concentrations >25% (w/w). Because of this, aqueous suspensions of phytoglycogen provide an ideal platform for detailed testing of theories of colloidal glasses and jamming. To further explore the interaction of the phytoglycogen particles and water, we have performed small angle neutron scattering (SANS) measurements on the Extended Q-Range SANS (EQ-SANS) diffractometer at the Spallation Neutron Source at Oak Ridge National Laboratory. Measurements performed on phytoglycogen dispersions in mixtures of hydrogenated and deuterated water have allowed us to determine the particle size and average particle spacing as a function of the phytoglycogen concentration in the limits of dilute and concentrated dispersions.

Utilization of the High Flux Isotope Reactor at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selby, Douglas L; Bilheux, Hassina Z; Meilleur, Flora

2015-01-01

This paper addresses several aspects of the scientific utilization of the Oak Ridge National Laboratory High Flux Isotope Reactor (HFIR). Topics to be covered will include: 1) HFIR neutron scattering instruments and the formal instrument user program; 2) Recent upgrades to the neutron scattering instrument stations at the reactor, and 3) eMod a new tool for addressing instrument modifications and providing configuration control and design process for scientific instruments at HFIR and the Spallation Neutron Source (SNS). There are 15 operating neutron instrument stations at HFIR with 12 of them organized into a formal user program. Since the last presentationmore » on HFIR instruments at IGORR we have installed a Single Crystal Quasi-Laue Diffractometer instrument called IMAGINE; and we have made significant upgrades to HFIR neutron scattering instruments including the Cold Triple Axis Instrument, the Wide Angle Neutron Diffractometer, the Powder Diffractometer, and the Neutron Imaging station. In addition, we have initiated upgrades to the Thermal Triple Axis Instrument and the Bio-SANS cold neutron instrument detector system. All of these upgrades are tied to a continuous effort to maintain a high level neutron scattering user program at the HFIR. For the purpose of tracking modifications such as those mentioned and configuration control we have been developing an electronic system for entering instrument modification requests that follows a modification or instrument project through concept development, design, fabrication, installation, and commissioning. This system, which we call eMod, electronically leads the task leader through a series of questions and checklists that then identifies such things as ES&H and radiological issues and then automatically designates specific individuals for the activity review process. The system has been in use for less than a year and we are still working out some of the inefficiencies, but we believe that this will become a

Passive Neutron Non-Destructive Assay for Remediation of Radiological Waste at Hanford Burial Grounds- 13189

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, A.; Pitts, M.; Ludowise, J.D.

The Hanford burial grounds contains a broad spectrum of low activity radioactive wastes, transuranic (TRU) wastes, and hazardous wastes including fission products, byproduct material (thorium and uranium), plutonium and laboratory chemicals. A passive neutron non-destructive assay technique has been developed for characterization of shielded concreted drums exhumed from the burial grounds. This method facilitates the separation of low activity radiological waste containers from TRU waste containers exhumed from the burial grounds. Two identical total neutron counting systems have been deployed, each consisting of He-3 detectors surrounded by a polyethylene moderator. The counts are processed through a statistical filter that removesmore » outliers in order to suppress cosmic spallation events and electronic noise. Upon completion of processing, a 'GO / NO GO' signal is provided to the operator based on a threshold level equivalent to 0.5 grams of weapons grade plutonium in the container being evaluated. This approach allows instantaneous decisions to be made on how to proceed with the waste. The counting systems have been set up using initial on-site measurements (neutron emitting standards loaded into surrogate waste containers) combined with Monte Carlo modeling techniques. The benefit of this approach is to allow the systems to extend their measurement ranges, in terms of applicable matrix types and container sizes, with minimal interruption to the operations at the burial grounds. (authors)« less

Cross section measurement of residues produced in proton- and deuteron-induced spallation reactions on 93Zr at 105 MeV/u using the inverse kinematics method

NASA Astrophysics Data System (ADS)

Kawase, Shoichiro; Watanabe, Yukinobu; Wang, He; Otsu, Hideaki; Sakurai, Hiroyoshi; Takeuchi, Satoshi; Togano, Yasuhiro; Nakamura, Takashi; Maeda, Yukie; Ahn, Deuk Soon; Aikawa, Masayuki; Araki, Shouhei; Chen, Sidong; Chiga, Nobuyuki; Doornenbal, Pieter; Fukuda, Naoki; Ichihara, Takashi; Isobe, Tadaaki; Kawakami, Shunsuke; Kin, Tadahiro; Kondo, Yosuke; Koyama, Shunpei; Kubo, Toshiyuki; Kubono, Shigeru; Kurokawa, Meiko; Makinaga, Ayano; Matsushita, Masafumi; Matsuzaki, Teiichiro; Michimasa, Shin'ichiro; Momiyama, Satoru; Nagamine, Shunsuke; Nakano, Keita; Niikura, Megumi; Ozaki, Tomoyuki; Saito, Atsumi; Saito, Takeshi; Shiga, Yoshiaki; Shikata, Mizuki; Shimizu, Yohei; Shimoura, Susumu; Sumikama, Toshiyuki; Söderström, Pär-Anders; Suzuki, Hiroshi; Takeda, Hiroyuki; Taniuchi, Ryo; Tsubota, Jun'ichi; Watanabe, Yasushi; Wimmer, Kathrin; Yamamoto, Tatsuya; Yoshida, Koichi

2017-09-01

Isotopic production cross sections in the proton- and deuteron-induced spallation reactions on 93Zr at an energy of 105 MeV/u were measured in inverse kinematics conditions for the development of realistic nuclear transmutation processes for long-lived fission products (LLFPs) with neutron and light-ion beams. The experimental results were compared to the PHITS calculations describing the intra-nuclear cascade and evaporation processes. Although an overall agreement was obtained, a large overestimation of the production cross sections for the removal of a few nucleons was seen. A clear shell effect associated with the neutron magic number N = 50 was observed in the measured isotopic production yields of Zr and Y isotopes, which can be reproduced reasonably by the PHITS calculation.

Neutron optics concept for the materials engineering diffractometer at the ESS

NASA Astrophysics Data System (ADS)

Šaroun, J.; Fenske, J.; Rouijaa, M.; Beran, P.; Navrátil, J.; Lukáš, P.; Schreyer, A.; Strobl, M.

2016-09-01

The Beamline for European Materials Engineering Research (BEER) has been recently proposed to be built at the European Spallation Source (ESS). The presented concept of neutron delivery optics for this instrument addresses the problems of bi-spectral beam extraction from a small moderator, optimization of neutron guides profile for long-range neutron transport and focusing at the sample under various constraints. They include free space before and after the guides, a narrow guide section with gaps for choppers, closing of direct line of sight and cost reduction by optimization of the guides cross-section and coating. A system of slits and exchangeable focusing optics is proposed in order to match various wavelength resolution options provided by the pulse shaping and modulation choppers, which permits to efficiently trade resolution for intensity in a wide range. Simulated performance characteristics such as brilliance transfer ratio are complemented by the analysis of the histories of “useful” neutrons obtained by back tracing neutrons hitting the sample, which helps to optimize some of the neutron guide parameters such as supermirror coating.

Deep inelastic neutron scattering on 207Pb and NaHF 2 as a test of a detectors array on the VESUVIO spectrometer

NASA Astrophysics Data System (ADS)

Pietropaolo, A.; Senesi, R.

2008-01-01

A prototype array of resonance detectors for deep inelastic neutron scattering experiments has been installed on the VESUVIO spectrometer, at the ISIS spallation neutron source. Deep inelastic neutron scattering measurements on a reference lead sample and on NaHF 2 molecular system are presented. Despite on an explorative level, the results obtained for the values of mean kinetic energy are found in good agreement with the theoretical predictions, thus assessing the potential capability of the device for a routine use on the instrument.

Neutron resonance spectroscopy for the characterization of materials and objects

NASA Astrophysics Data System (ADS)

Schillebeeckx, P.; Borella, A.; Emiliani, F.; Gorini, G.; Kockelmann, W.; Kopecky, S.; Lampoudis, C.; Moxon, M.; Perelli Cippo, E.; Postma, H.; Rhodes, N. J.; Schooneveld, E. M.; Van Beveren, C.

2012-03-01

The resonance structure in neutron induced reaction cross sections can be used to determine the elemental compositions of materials or objects. The occurrence of resonances is the basis of neutron resonance capture analysis (NRCA) and neutron resonance transmission analysis (NRTA). NRCA and NRTA are fully non-destructive methods to determine the bulk elemental composition without the need of any sample preparation and resulting in a negligible residual activity. They have been applied to determine the elemental composition of archaeological objects and to characterize reference materials used for cross section measurements. For imaging applications a position sensitive neutron detector has been developed within the ANCIENT CHARM project. The detector is based on a 10 × 10 array of 6Li-glass scintillators mounted on a pitch of 2.5 mm, resulting in a 25 × 25 mm2 active area. The detector has been tested at the time-of-flight facility GELINA and used at the ISIS spallation source to study cultural heritage objects.

Measurement of the Parity-Violating directional Gamma-ray Asymmetry in Polarized Neutron Capture on ^35Cl

NASA Astrophysics Data System (ADS)

Fomin, Nadia

2012-03-01

The NPDGamma experiment aims to measure the parity-odd correlation between the neutron spin and the direction of the emitted photon in neutron-proton capture. A parity violating asymmetry (to be measured to 10-8) from this process can be directly related to the strength of the hadronic weak interaction between nucleons. As part of the commissioning runs on the Fundamental Neutron Physics beamline at the Spallation Neutron Source at ORNL, the gamma-ray asymmetry from the parity-violating capture of cold neutrons on ^35Cl was measured, primarily to check for systematic effects and false asymmtries. The current precision from existing world measurements on this asymmetry is at the level of 10-6 and we believe we can improve it. The analysis methodology as well as preliminary results will be presented.

Energy-dispersive neutron imaging and diffraction of magnetically driven twins in a Ni2MnGa single crystal magnetic shape memory alloy

NASA Astrophysics Data System (ADS)

Kabra, Saurabh; Kelleher, Joe; Kockelmann, Winfried; Gutmann, Matthias; Tremsin, Anton

2016-09-01

Single crystals of a partially twinned magnetic shape memory alloy, Ni2MnGa, were imaged using neutron diffraction and energy-resolved imaging techniques at the ISIS spallation neutron source. Single crystal neutron diffraction showed that the crystal produces two twin variants with a specific crystallographic relationship. Transmission images were captured using a time of flight MCP/Timepix neutron counting detector. The twinned and untwinned regions were clearly distinguishable in images corresponding to narrow-energy transmission images. Further, the spatially-resolved transmission spectra were used to elucidate the orientations of the crystallites in the different volumes of the crystal.

A virtual laboratory for neutron and synchrotron strain scanning

NASA Astrophysics Data System (ADS)

James, J. A.; Santisteban, J. R.; Edwards, L.; Daymond, M. R.

2004-07-01

The new generation of dedicated Engineering Strain Scanners at neutron and synchrotron facilities offer considerable improvements in both counting time and spatial resolution. In order to make full use of these advances in instrumentation, the routine tasks associated with setting up measurement runs and analysing the data need to be made as efficient as possible. Such tasks include the planning of the experiment, the alignment and positioning of the specimen, the least-squares refinement of diffraction spectra, the definition of strain in the sample coordinate system, and its visualization within a 3D model of the specimen. With this aim in mind, we have written a software providing support for most of these operations. The approach is based on a virtual lab consisting of 3D models of the sample and laboratory equipment. The system has been developed for ENGIN-X, the new engineering strain scanner recently commissioned at ISIS, but it is flexible enough to be ported to other neutron or synchrotron strain scanners. The software has been designed with visiting industrial and academic researchers in mind, users who need to be able to control the instrument after only a short period of training.

Application of pixel-cell detector technology for Advanced Neutron Beam Monitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopp, Daniel M.

2011-01-11

Application of Pixel-Cell Detector Technology for Advanced Neutron Beam Monitors Specifications of currently available neutron beam detectors limit their usefulness at intense neutron beams of large-scale national user facilities used for the advanced study of materials. A large number of neutron-scattering experiments require beam monitors to operate in an intense neutron beam flux of >10E+7 neutrons per second per square centimeter. For instance, a 4 cm x 4 cm intense beam flux of 6.25 x 10E+7 n/s/cm2 at the Spallation Neutron Source will put a flux of 1.00 x 10E+9 n/s at the beam monitor. Currently available beam monitors withmore » a typical efficiency of 1 x 10E-4 will need to be replaced in less than two years of operation due to wire and gas degradation issues. There is also a need at some instruments for beam position information that are beyond the capabilities of currently available He-3 and BF3 neutron beam monitors. ORDELA, Inc.’s research under USDOE SBIR Grant (DE-FG02-07ER84844) studied the feasibility of using pixel-cell technology for developing a new generation of stable, long-life neutron beam monitors. The research effort has led to the development and commercialization of advanced neutron beam detectors that will directly benefit the Spallation Neutron Source and other intense neutron sources such as the High Flux Isotope Reactor. A prototypical Pixel-Cell Neutron Beam Monitor was designed and constructed during this research effort. This prototype beam monitor was exposed to an intense neutron beam at the HFIR SNS HB-2 test beam site. Initial measurements on efficiency, uniformity across the detector, and position resolution yielded excellent results. The development and test results have provided the required data to initiate the fabrication and commercialization of this next generation of neutron-detector systems. ORDELA, Inc. has (1) identified low-cost design and fabrication strategies, (2) developed and built pixel-cell detectors and

Neutron Science TeraGrid Gateway

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lynch, Vickie E; Chen, Meili; Cobb, John W

The unique contributions of the Neutron Science TeraGrid Gateway (NSTG) are the connection of national user facility instrument data sources to the integrated cyberinfrastructure of the National Science FoundationTeraGrid and the development of a neutron science gateway that allows neutron scientists to use TeraGrid resources to analyze their data, including comparison of experiment with simulation. The NSTG is working in close collaboration with the Spallation Neutron Source (SNS) at Oak Ridge as their principal facility partner. The SNS is a next-generation neutron source. It has completed construction at a cost of $1.4 billion and is ramping up operations. The SNSmore » will provide an order of magnitude greater flux than any previous facility in the world and will be available to all of the nation's scientists, independent of funding source, on a peer-reviewed merit basis. With this new capability, the neutron science community is facing orders of magnitude larger data sets and is at a critical point for data analysis and simulation. There is a recognized need for new ways to manage and analyze data to optimize both beam time and scientific output. The TeraGrid is providing new capabilities in the gateway for simulations using McStas and a fitting service on distributed TeraGrid resources to improved turnaround. NSTG staff are also exploring replicating experimental data in archival storage. As part of the SNS partnership, the NSTG provides access to gateway support, cyberinfrastructure outreach, community development, and user support for the neutron science community. This community includes not only SNS staff and users but extends to all the major worldwide neutron scattering centers.« less

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

NASA Technical Reports Server (NTRS)

Smialek, James L.

2009-01-01

For some time our community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cooldown, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of TBC's refer to this process. It is most apparent for relatively adherent alumina scales that have survived cool down in a dry environment, built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sweet zone" can be defined that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen as a reaction product or detected interfacial species. Further support is provided by critical experiments that produce the same moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H2-containing atmospheres or cathodic hydrogen charging.

Development of the front end test stand and vessel for extraction and source plasma analyses negative hydrogen ion sources at the Rutherford Appleton Laboratory.

PubMed

Lawrie, S R; Faircloth, D C; Letchford, A P; Perkins, M; Whitehead, M O; Wood, T; Gabor, C; Back, J

2014-02-01

The ISIS pulsed spallation neutron and muon facility at the Rutherford Appleton Laboratory (RAL) in the UK uses a Penning surface plasma negative hydrogen ion source. Upgrade options for the ISIS accelerator system demand a higher current, lower emittance beam with longer pulse lengths from the injector. The Front End Test Stand is being constructed at RAL to meet the upgrade requirements using a modified ISIS ion source. A new 10% duty cycle 25 kV pulsed extraction power supply has been commissioned and the first meter of 3 MeV radio frequency quadrupole has been delivered. Simultaneously, a Vessel for Extraction and Source Plasma Analyses is under construction in a new laboratory at RAL. The detailed measurements of the plasma and extracted beam characteristics will allow a radical overhaul of the transport optics, potentially yielding a simpler source configuration with greater output and lifetime.

On the empirical determination of positron trapping coefficient at nano-scale helium bubbles in steels irradiated in spallation target

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Kuriplach, Jan; Vieh, Christiane; Peng, Lei; Dai, Yong

2018-06-01

In the present work, the specific positron trapping rate of small helium bubbles was empirically derived from positron annihilation lifetime spectroscopy (PALS) and transmission electron microscopy (TEM) studies of Fe9Cr martensitic steels. Both techniques are well known to be sensitive to nanometer-sized helium-filled cavities induced during irradiation in a mixed proton-neutron spectrum of spallation target. Complementary TEM and PALS studies show that positrons are being trapped to these defects at a rate of 1.2 ± 0.8 × 10-14 m3s-1. This suggests that helium bubbles in ferritic/martensitic steels are attractive traps for positrons comparable to mono-vacancies and quantitative analysis of the bubbles by PALS technique is plausible.

A nuclear method to measure spallation by thermal cycling of protective surface layers

NASA Astrophysics Data System (ADS)

Stroosnijder, M. F.; Macchi, G.

1995-05-01

After a general introduction on spallation by thermal cycling, the principle of Thin Layer Activation (TLA) is outlined. A practical setup to measure spallation of protective surface layers by thermal cycling using TLA is discussed. Its use is illustrated with the study of the spallation behaviour of an advanced thermal barrier coating. It is shown that among the various benefits, TLA has a direct relation to material loss and shows a significant increase in sensitivity over other test methods. Due to its intrinsic properties, TLA can contribute to a greater scientific understanding of material degradation by thermal cycling and it can provide a more reliable assessment of the service lives of technical components.

Numerical simulations of stripping effects in high-intensity hydrogen ion linacs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carneiro, J.-P.; /Fermilab; Mustapha, B.

2008-12-01

Numerical simulations of H{sup -} stripping losses from blackbody radiation, electromagnetic fields, and residual gas have been implemented into the beam dynamics code TRACK. Estimates of the stripping losses along two high-intensity H{sup -} linacs are presented: the Spallation Neutron Source linac currently being operated at Oak Ridge National Laboratory and an 8 GeV superconducting linac currently being designed at Fermi National Accelerator Laboratory.

Condensed-matter research at the Los Alamos pulsed neutron source (WNR)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eckert, J.

1982-01-01

The experimental program at the WNR in condensed matter research at present is aimed principally at utilizing the high epithermal neutron flux available at a spallation neutron source. Interesting new results have been obtained in several areas including hydrogen vibrations in metals, chemical vibrational spectroscopy and the structure of liquids. For example, extensive vibrational spectra were obtained of hydrogen in Nb which could be described in terms of a three-dimensional localized anharmonic oscillator, deuterium substitution methods were used to determine the variation with 0-0 distance of the hydrogen bending mode frequency in extremely short intramolecular hydrogen bonds, and model-independent partialmore » structure factors were determined for liquid water.« less

High-pressure studies on Ba-doped cobalt perovskites by neutron diffraction

NASA Astrophysics Data System (ADS)

Cao, Huibo; Garlea, Vasile; Wang, Fangwei; Dos Santos, Antonio; Cheng, Zhaohua

2012-02-01

Cobalt perovskite possess rich structural, magnetic and electrical properties depending on the subtle balance of the interactions among the spin, charge, and orbital degrees of freedom. Divalent hole-doped cobalt perovskites LaA^2+CoO3 exhibit structural phase transitions, metal-insulator transitions, and multi-magnetic phase transitions. High-pressure measurement is believed to mimic the size effects of the doped ions. We performed neutron diffraction experiments on selected Ba-doped LaCoO3 under pressures up to 6.3 GPa at SNAP at Spallation Neutron Source of ORNL. This work focuses on the high-pressure effects of the selected Ba-doped samples and the change of the phase diagram with pressure.

Possible Itinerant Moment Contributions to the Magnetic Excitations in Gd, Studied by Neutron Spectroscopy

NASA Astrophysics Data System (ADS)

Granroth, G. E.; Aczel, A. A.; Fernandez-Baca, J. A.; Nagler, S. E.

2013-03-01

Many experimental features in magnetic superconductors are also present when these complex materials are in the normal state. Therefore studies of simpler itinerant magnets may help provide understanding of these phenomena. We chose to study Gd as it is has an ~ 0 . 6μB itinerant moment in addition to a ~ 7 . 0μB localized moment. The SEQUOIA spectrometer, at the Spallation Neutron Source at Oak Ridge National Laboratory, was used in fine resolution mode with Ei=50 meV neutrons, to measure the magnetic excitations in a 12 gm 160Gd single crystal. The crystal was mounted with the h 0 l plane horizontal and rotated around the vertical axis to map out the excitations. The measured magnetic structure factor for the acoustic modes in the hh 0 direction has an intensity step at h ~ 0 . 3 . Electronic band structure calculations (W. M. Temmerman and P. A. Sterne, J. Phys: Condes. Matter,2, 5529 (1990)) show this Q position to be near several band crossings of the Fermi surface. A detailed analysis, including instrumental resolution, is presented to clarify any relationship between the magnetic structure factor and the electronic band structure. This work was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.

Advances in Neutron Radiography: Application to Additive Manufacturing Inconel 718

DOE PAGES

Bilheux, Hassina Z; Song, Gian; An, Ke; ...

2016-01-01

Reactor-based neutron radiography is a non-destructive, non-invasive characterization technique that has been extensively used for engineering materials such as inspection of components, evaluation of porosity, and in-operando observations of engineering parts. Neutron radiography has flourished at reactor facilities for more than four decades and is relatively new to accelerator-based neutron sources. Recent advances in neutron source and detector technologies, such as the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN, and the microchannel plate (MCP) detector, respectively, enable new contrast mechanisms using the neutron scattering Bragg features for crystalline information such as averagemore » lattice strain, crystalline plane orientation, and identification of phases in a neutron radiograph. Additive manufacturing (AM) processes or 3D printing have recently become very popular and have a significant potential to revolutionize the manufacturing of materials by enabling new designs with complex geometries that are not feasible using conventional manufacturing processes. However, the technique lacks standards for process optimization and control compared to conventional processes. Residual stresses are a common occurrence in materials that are machined, rolled, heat treated, welded, etc., and have a significant impact on a component s mechanical behavior and durability. They may also arise during the 3D printing process, and defects such as internal cracks can propagate over time as the component relaxes after being removed from its build plate (the base plate utilized to print materials on). Moreover, since access to the AM material is possible only after the component has been fully manufactured, it is difficult to characterize the material for defects a priori to minimize expensive re-runs. Currently, validation of the AM process and materials is mainly through expensive trial-and-error experiments at the

Polarized 3He Spin Filters for Slow Neutron Physics

PubMed Central

Gentile, T. R.; Chen, W. C.; Jones, G. L.; Babcock, E.; Walker, T. G.

2005-01-01

Polarized 3He spin filters are needed for a variety of experiments with slow neutrons. Their demonstrated utility for highly accurate determination of neutron polarization are critical to the next generation of betadecay correlation coefficient measurements. In addition, they are broadband devices that can polarize large area and high divergence neutron beams with little gamma-ray background, and allow for an additional spin-flip for systematic tests. These attributes are relevant to all neutron sources, but are particularly well-matched to time of flight analysis at spallation sources. There are several issues in the practical use of 3He spin filters for slow neutron physics. Besides the essential goal of maximizing the 3He polarization, we also seek to decrease the constraints on cell lifetimes and magnetic field homogeneity. In addition, cells with highly uniform gas thickness are required to produce the spatially uniform neutron polarization needed for beta-decay correlation coefficient experiments. We are currently employing spin-exchange (SE) and metastability-exchange (ME) optical pumping to polarize 3He, but will focus on SE. We will discuss the recent demonstration of 75 % 3He polarization, temperature-dependent relaxation mechanism of unknown origin, cell development, spectrally narrowed lasers, and hybrid spin-exchange optical pumping. PMID:27308140

Polarized (3) He Spin Filters for Slow Neutron Physics.

PubMed

Gentile, T R; Chen, W C; Jones, G L; Babcock, E; Walker, T G

2005-01-01

Polarized (3)He spin filters are needed for a variety of experiments with slow neutrons. Their demonstrated utility for highly accurate determination of neutron polarization are critical to the next generation of betadecay correlation coefficient measurements. In addition, they are broadband devices that can polarize large area and high divergence neutron beams with little gamma-ray background, and allow for an additional spin-flip for systematic tests. These attributes are relevant to all neutron sources, but are particularly well-matched to time of flight analysis at spallation sources. There are several issues in the practical use of (3)He spin filters for slow neutron physics. Besides the essential goal of maximizing the (3)He polarization, we also seek to decrease the constraints on cell lifetimes and magnetic field homogeneity. In addition, cells with highly uniform gas thickness are required to produce the spatially uniform neutron polarization needed for beta-decay correlation coefficient experiments. We are currently employing spin-exchange (SE) and metastability-exchange (ME) optical pumping to polarize (3)He, but will focus on SE. We will discuss the recent demonstration of 75 % (3)He polarization, temperature-dependent relaxation mechanism of unknown origin, cell development, spectrally narrowed lasers, and hybrid spin-exchange optical pumping.

Spallation of Cu by. pi. /sup -/ across the T = 1/2 resonances and at high energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haustein, P.E.

1979-09-01

Relative yields of 11 selected products (/sup 24/Na, /sup 43,44,46,47,48/Sc, /sup 55,56,57,58,60/Co) have been measured for the interaction of 0.6- and 0.9-GeV negative pions with Cu. In addition, the yields of /sup 24/Na and /sup 58/Co from Cu have been measured for 12-GeV ..pi../sup -/. Results at the two lower energies which correspond to the first two isospin T = 1/2 pion-nucleon resonances are compared with earlier studies of Cu spallation by ..pi../sup -/ at energies across the first T = 3/2 resonance, i.e., 50 to 350 MeV. The 12-GeV ..pi../sup -/ results are compared with similar investigations in whichmore » both energetic protons and heavy ions were used. For E/sub ..pi../ > or = 0.5 GeV no evidence of strong resonance effects can be found in the pattern of the spallation yields. As the pion energy is raised a smooth trend of enhanced yields of deep spallation products to near-target yields closely parallels the same trend observed for both high-energy proton and heavy-ion spallation of Cu. These results indicate that at high energy, pi-mesic spallation exhibits the same features of limiting fragmentation and factorization of the isotopic yields that have been observed previously in hadron induced spallation.« less

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

DOEpatents

Miley, George H.; Yang, Xiaoling

2013-09-03

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

Neutron Imaging at LANSCE—From Cold to Ultrafast

DOE PAGES

Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.; ...

2018-02-23

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

Neutron Imaging at LANSCE—From Cold to Ultrafast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nelson, Ronald Owen; Vogel, Sven C.; Hunter, James F.

In recent years, neutron radiography and tomography have been applied at different beam lines at Los Alamos Neutron Science Center (LANSCE), covering a very wide neutron energy range. The field of energy-resolved neutron imaging with epi-thermal neutrons, utilizing neutron absorption resonances for contrast as well as quantitative density measurements, was pioneered at the Target 1 (Lujan center), Flight Path 5 beam line and continues to be refined. Applications include: imaging of metallic and ceramic nuclear fuels, fission gas measurements, tomography of fossils and studies of dopants in scintillators. The technique provides the ability to characterize materials opaque to thermal neutronsmore » and to utilize neutron resonance analysis codes to quantify isotopes to within 0.1 atom %. The latter also allows measuring fuel enrichment levels or the pressure of fission gas remotely. More recently, the cold neutron spectrum at the ASTERIX beam line, also located at Target 1, was used to demonstrate phase contrast imaging with pulsed neutrons. This extends the capabilities for imaging of thin and transparent materials at LANSCE. In contrast, high-energy neutron imaging at LANSCE, using unmoderated fast spallation neutrons from Target 4 [Weapons Neutron Research (WNR) facility] has been developed for applications in imaging of dense, thick objects. Using fast (ns), time-of-flight imaging, enables testing and developing imaging at specific, selected MeV neutron energies. The 4FP-60R beam line has been reconfigured with increased shielding and new, larger collimation dedicated to fast neutron imaging. The exploration of ways in which pulsed neutron beams and the time-of-flight method can provide additional benefits is continuing. We will describe the facilities and instruments, present application examples and recent results of all these efforts at LANSCE.« less

Application of activation methods on the Dubna experimental transmutation set-ups.

PubMed

Stoulos, S; Fragopoulou, M; Adloff, J C; Debeauvais, M; Brandt, R; Westmeier, W; Krivopustov, M; Sosnin, A; Papastefanou, C; Zamani, M; Manolopoulou, M

2003-02-01

High spallation neutron fluxes were produced by irradiating massive heavy targets with proton beams in the GeV range. The experiments were performed at the Dubna High Energy Laboratory using the nuclotron accelerator. Two different experimental set-ups were used to produce neutron spectra convenient for transmutation of radioactive waste by (n,x) reactions. By a theoretical analysis neutron spectra can be reproduced from activation measurements. Thermal-epithermal and fast-super-fast neutron fluxes were estimated using the 197Au, 238U (n,gamma) and (n,2n) reactions, respectively. Depleted uranium transmutation rates were also studied in both experiments.

Interfacing MCNPX and McStas for simulation of neutron transport

NASA Astrophysics Data System (ADS)

Klinkby, Esben; Lauritzen, Bent; Nonbøl, Erik; Kjær Willendrup, Peter; Filges, Uwe; Wohlmuther, Michael; Gallmeier, Franz X.

2013-02-01

Simulations of target-moderator-reflector system at spallation sources are conventionally carried out using Monte Carlo codes such as MCNPX (Waters et al., 2007 [1]) or FLUKA (Battistoni et al., 2007; Ferrari et al., 2005 [2,3]) whereas simulations of neutron transport from the moderator and the instrument response are performed by neutron ray tracing codes such as McStas (Lefmann and Nielsen, 1999; Willendrup et al., 2004, 2011a,b [4-7]). The coupling between the two simulation suites typically consists of providing analytical fits of MCNPX neutron spectra to McStas. This method is generally successful but has limitations, as it e.g. does not allow for re-entry of neutrons into the MCNPX regime. Previous work to resolve such shortcomings includes the introduction of McStas inspired supermirrors in MCNPX. In the present paper different approaches to interface MCNPX and McStas are presented and applied to a simple test case. The direct coupling between MCNPX and McStas allows for more accurate simulations of e.g. complex moderator geometries, backgrounds, interference between beam-lines as well as shielding requirements along the neutron guides.

Bombs, Bosons and Beer Cans-Research at the Los Alamos Neutron Science Center

NASA Astrophysics Data System (ADS)

Pynn, Roger

1997-04-01

The neutron scattering community is justifiably proud of the contributions it has made to basic research in many areas of science. Information obtained using neutrons has contributed strongly to our basic understanding of phenomena in diverse systems of interest to physicists, chemists and biologists - think, for example, of how little we would know about excitations in quantum fluids, the spin-density-wave state of chromium, electronic back-donation in the bonding of organometallic compounds, or the conformation of proteins and DNA in nucleosomes without neutron scattering. However, illustrious as this history of neutron scattering may be, it is not the only type of contribution neutrons have made to our modern scientific and technological enterprise. Increasingly in recent years, we have witnessed the application of neutrons to later parts of the R&D cycle, to problems that have been called ''strategic research'' and even in areas that are ''applied research'' or ''product development''. The purpose of my talk at this meeting is to illustrate this aspect of research at spallation neutron sources, using examples of work that has been done at the Los Alamos Neutron Science Center (LANSCE). Some of this work is driven by the fact that our principal funding agency, the Office of Defense Programs within the U.S. Department of Energy, has a need to master the science behind technologies relevant to nuclear weapons. Even so, most of the examples I have picked are equally relevant to the industrial sector and several would not shame even the most devout proponent of ''pure'' research. To demonstrate the breadth of the research performed at LANSCE, I will describe examples of recent experiments in the following areas: materials texture; temperature and particle velocity measurement in reacting high explosives; radiographic imaging with protons; chemical bonding in metal-dihydride complexes; and the structure of thin adhesive layers. LANSCE operates a user program and

Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory.

PubMed

Köhler, J; Ehresmann, B; Zeitlin, C; Wimmer-Schweingruber, R F; Hassler, D M; Reitz, G; Brinza, D E; Appel, J; Böttcher, S; Böhm, E; Burmeister, S; Guo, J; Lohf, H; Martin, C; Posner, A; Rafkin, S

2015-04-01

The Mars Science Laboratory spacecraft, containing the Curiosity rover, was launched to Mars on 26 November 2011. Although designed for measuring the radiation on the surface of Mars, the Radiation Assessment Detector (RAD) measured the radiation environment inside the spacecraft during most of the 253-day, 560-million-kilometer cruise to Mars. An important factor for determining the biological impact of the radiation environment inside the spacecraft is the specific contribution of neutrons with their high biological effectiveness. We apply an inversion method (based on a maximum-likelihood estimation) to calculate the neutron and gamma spectra from the RAD neutral particle measurements. The measured neutron spectrum (12-436 MeV) translates into a radiation dose rate of 3.8±1.2 μGy/day and a dose equivalent of 19±5 μSv/day. Extrapolating the measured spectrum (0.1-1000 MeV), we find that the total neutron-induced dose rate is 6±2 μGy/day and the dose equivalent rate is 30±10 μSv/day. For a 360 day round-trip from Earth to Mars with comparable shielding, this translates into a neutron induced dose equivalent of about 11±4 mSv. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.

Preface: Proceedings of the 4th European Conference on Neutron Scattering (Lund, Sweden, 25 29 June 2007)

NASA Astrophysics Data System (ADS)

Rennie, Adrian R.

2008-03-01

Approximately 700 delegates came to the small university city of Lund in southern Sweden at the end of June 2007 to attend the 4th European Conference on Neutron Scattering. The majority of these participants are primarily interested in specific areas of condensed matter science and use neutron techniques as a powerful tool to study the structure and dynamic behaviour of materials. These range from liquids, superconductors, magnetic materials and archaeological artefacts. The diversity of scientific problems is reflected by the attendance of many laboratories with specializations in numerous different disciplines. The maturity of the technique is shown by the fact that neutron scattering is now applied widely in so many areas. Most results from neutron scattering experiements are published as articles that primarily relate to a specific scientific discipline in the context of problem oriented research. The neutron scattering conference provided an opportunity to exchange ideas between different fields. It is hoped that this collection of papers, from participants that submitted articles on applications of neutron scattering, will continue to promote the exchange of ideas for new studies, as was seen at the conference. The papers that describe instrumentation and advances in methods of neutron scattering will appear separately in Measurement Science and Technology Worldwide activity in developing new facilities for neutron scattering and the motivation for substantial projects, such as the new target station at the ISIS facility in the UK or the proposed European Spallation Source, comes from unique information obtained from working with neutrons. The results reported in the following papers show that there is substantial exciting work still to be performed as the community of users expands into new fields. The participants, as well as the organizers, are extremely grateful to the numerous sponsors that helped to make the conference a resounding success. We are

Neutron Detection Efficiency Optimization Studies of the Neutron Polarimeter for the C-GEN Electric Form Factor at Jefferson National Laboratory

NASA Astrophysics Data System (ADS)

Adzima, Ashley; Tireman, William; C-Gen Collaboration

The electric form factor is an important quantity to further the understanding of the atom and its constituent parts. The C-GEN collaboration at Jefferson National Laboratory plans to measure this fundamental quantity using recoil polarimetry. An efficient neutron polarimeter is essential for the collection of precise data and involves maximizing the ratio of elastic to inelastic events identified. The determination of the elastic to inelastic ratio of neutron events was simulated using GEANT-4 on 5 cm, 10 cm, and 15 cm thick detectors. Specific requirements were set in place by C-GEN to determine what marks an elastic event. Plots of neutron scattering events versus detector thickness were analyzed, and the ratio of elastic to inelastic events was extracted for each section per vertical slice, as well as an average ratio. The average ratio of elastic to inelastic events were 0.2206, 0.1706, and 0.1507 for the 5 cm, 10 cm, and 15 cm detectors, respectfully. The impact of these ratios on the statistics and costs of altering the polarimeter's original 10 cm detector design will be further discussed. U.S. Department of Education - TRIO McNair Scholars Program.

Spallation-induced roughness promoting high spatial frequency nanostructure formation on Cr

NASA Astrophysics Data System (ADS)

Abou-Saleh, A.; Karim, E. T.; Maurice, C.; Reynaud, S.; Pigeon, F.; Garrelie, F.; Zhigilei, L. V.; Colombier, J. P.

2018-04-01

Interaction of ultrafast laser pulses with metal surfaces in the spallation regime can result in the formation of anisotropic nanoscale surface morphology commonly referred to as laser-induced periodic surface structures (LIPSS) or ripples. The surface structures generated by a single pulse irradiation of monocrystalline Cr samples are investigated experimentally and computationally for laser fluences that produce high spatial frequency nanostructures in the multi-pulse irradiation regime. Electron microscopy reveals distinct response of samples with different crystallographic surface orientations, with (100) surfaces exhibiting the formation of more refined nanostructure by a single pulse irradiation and a more pronounced LIPSS after two laser pulses as compared to (110) surfaces. A large-scale molecular dynamics simulation of laser interaction with a (100) Cr target provides detailed information on processes responsible for spallation of a liquid layer, redistribution of molten material, and rapid resolidification of the target. The nanoscale roughness of the resolidified surface predicted in the simulation features elongated frozen nanospikes, nanorims and nanocavities with dimensions and surface density similar to those in the surface morphology observed for (100) Cr target with atomic force microscopy. The results of the simulation suggest that the types, sizes and dimensions of the nanoscale surface features are defined by the competition between the evolution of transient liquid structures generated in the spallation process and the rapid resolidification of the surface region of the target. The spallation-induced roughness is likely to play a key role in triggering the generation of high-frequency LIPSS upon irradiation by multiple laser pulses.

Dynamics of spallation during femtosecond laser ablation studied by time-resolved reflectivity with double pump pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumada, Takayuki, E-mail: kumada.takayuki@jaea.go.jp; Otobe, Tomohito; Nishikino, Masaharu

2016-01-04

The dynamics of photomechanical spallation during femtosecond laser ablation of fused silica was studied by time-resolved reflectivity with double pump pulses. Oscillation of reflectivity was caused by interference between the probe pulses reflected at the sample surface and the spallation layer, and was enhanced when the surface was irradiated with the second pump pulse within a time interval, Δτ, of several picoseconds after the first pump pulse. However, as Δτ was increased, the oscillation amplitude decreased with an exponential decay time of 10 ps. The oscillation disappeared when Δτ exceeded 20 ps. This result suggests that the formation time of the spallationmore » layer is approximately 10 ps. A second pump pulse with Δτ shorter than 10 ps excites the bulk sample. The spallation layer that is photo-excited by the first and second pump pulses is separated afterward. In contrast, a pulse with Δτ longer than the formation time excites and breaks up the spallation layer that has already been separated from the bulk. The formation time of the spallation layer, as determined in this experiment, is attributed to the characteristic time of the mechanical equilibration corresponding to the thickness divided by the sound velocity of the photo-excited layer.« less

Spallation backgrounds in Super-Kamiokande are made in muon-induced showers

NASA Astrophysics Data System (ADS)

Li, Shirley Weishi; Beacom, John F.

2015-05-01

Crucial questions about solar and supernova neutrinos remain unanswered. Super-Kamiokande has the exposure needed for progress, but detector backgrounds are a limiting factor. A leading component is the beta decays of isotopes produced by cosmic-ray muons and their secondaries, which initiate nuclear spallation reactions. Cuts of events after and surrounding muon tracks reduce this spallation decay background by ≃ 90 % (at a cost of ≃ 20 % deadtime), but its rate at 6-18 MeV is still dominant. A better way to cut this background was suggested in a Super-Kamiokande paper by Bays et al. [Phys. Rev. D 85, 052007 (2012)] on a search for the diffuse supernova neutrino background. They found that spallation decays above 16 MeV were preceded near the same location by a peak in the apparent Cherenkov light profile from the muon; a more aggressive cut was applied to a limited section of the muon track, leading to decreased background without increased deadtime. We put their empirical discovery on a firm theoretical foundation. We show that almost all spallation decay isotopes are produced by muon-induced showers and that these showers are rare enough and energetic enough to be identifiable. This is the first such demonstration for any detector. We detail how the physics of showers explains the peak in the muon Cherenkov light profile and other Super-K observations. Our results provide a physical basis for practical improvements in background rejection that will benefit multiple studies. For solar neutrinos, in particular, it should be possible to dramatically reduce backgrounds at energies as low as 6 MeV.

LOS ALAMOS NEUTRON SCIENCE CENTER CONTRIBUTIONS TO THE DEVELOPMENT OF FUTURE POWER REACTORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

GAVRON, VICTOR I.; HILL, TONY S.; PITCHER, ERIC J.

The Los Alamos Neutron Science Center (LANSCE) is a large spallation neutron complex centered around an 800 MeV high-currently proton accelerator. Existing facilities include a highly-moderated neutron facility (Lujan Center) where neutrons between thermal and keV energies are produced, and the Weapons Neutron Research Center (WNR), where a bare spallation target produces neutrons between 0.1 and several hundred MeV.The LANSCE facility offers a unique capability to provide high precision nuclear data over a large energy region, including that for fast reactor systems. In an ongoing experimental program the fission and capture cross sections are being measured for a number ofmore » minor actinides relevant for Generation-IV reactors and transmutation technology. Fission experiments makes use of both the highly moderated spallation neutron spectrum at the Lujan Center, and the unmoderated high energy spectrum at WNR. By combininb measurements at these two facilities the differential fission cross section is measured relative to the {sup 235}U(n,f) standard from subthermal energies up to about 200 MeV. An elaborate data acquisition system is designed to deal with all the different types of background present when spanning 10 energy decades. The first isotope to be measured was {sup 237}Np, and the results were used to improve the current ENDF/B-VII evaluation. Partial results have also been obtained for {sup 240}Pu and {sup 242}Pu, and the final results are expected shortly. Capture cross sections are measured at LANSCE using the Detector for Advanced Neutron Capture Experiments (DANCE). This unique instrument is highly efficient in detecting radiative capture events, and can thus handle radioactive samples of half-lives as low as 100 years. A number of capture cross sections important to fast reaction applications have been measured with DANCE. The first measurement was on {sup 237}Np(n,{gamma}), and the results have been submitted for publication. Other capture

Linac design for the European spallation source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, H.

1995-10-01

A study group has started to develop a conceptual design for a European Spallation Source (ESS). This pulsed 5 MW source presently consists of a 1.334 GeV linac and two compressor rings. In the following mainly the high intensity linac part will be discussed, which has some features of interest for accelerators for transmutation of radioactive waste too.

Solid methane in neutron radiation: Cryogenic moderators and cometary cryo volcanism

NASA Astrophysics Data System (ADS)

Kirichek, O.; Lawson, C. R.; Jenkins, D. M.; Ridley, C. J. T.; Haynes, D. J.

2017-12-01

The effect of ionizing radiation on solid methane has previously been an area of interest in the astrophysics community. In the late 1980s this interest was further boosted by the possibility of using solid methane as a moderating medium in spallation neutron sources. Here we present test results of solid methane moderators commissioned at the ISIS neutron source, and compare them with a model based on the theory of thermal explosion. Good agreement between the moderator test data and our model suggests that the process of radiolysis defect recombination happens at two different temperature ranges: the ;lower temperature; recombination process occurs at around 20 K, with the ;higher temperature; process taking place between 50 and 60 K. We discuss consequences of this mechanism for the designing and operation of solid methane moderators used in advanced neutron sources. We also discuss the possible role of radiolysis defect recombination processes in cryo-volcanism on comets, and suggest an application based on this phenomenon.

Design of a transportable high efficiency fast neutron spectrometer

DOE PAGES

Roecker, C.; Bernstein, A.; Bowden, N. S.; ...

2016-04-12

A transportable fast neutron detection system has been designed and constructed for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The transportability of the spectrometer reduces the detector-related systematic bias between different neutron spectra and flux measurements, which allows for the comparison of measurements above or below ground. The spectrometer will measure neutron fluxes that are of prohibitively low intensity compared to the site-specific background rates targeted by other transportable fast neutron detection systems. To measure low intensity high-energy neutron fluxes, a conventional capture-gating technique is used for measuring neutron energies above 20 MeV andmore » a novel multiplicity technique is used for measuring neutron energies above 100 MeV. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. To calibrate and characterize the position dependent response of the spectrometer, a Monte Carlo model was developed and used in conjunction with experimental data from gamma ray sources. Multiplicity event identification algorithms were developed and used with a Cf-252 neutron multiplicity source to validate the Monte Carlo model Gd concentration and secondary neutron capture efficiency. The validated Monte Carlo model was used to predict an effective area for the multiplicity and capture gating analyses. For incident neutron energies between 100 MeV and 1000 MeV with an isotropic angular distribution, the multiplicity analysis predicted an effective area of 500 cm 2 rising to 5000 cm 2. For neutron energies above 20 MeV, the capture-gating analysis predicted an effective area between 1800 cm 2 and 2500 cm 2. As a result, the multiplicity mode was found to be sensitive to the incident neutron angular distribution.« less

Neutron and antineutron production in accretion onto compact objects

NASA Technical Reports Server (NTRS)

Dermer, C. D.; Ramaty, R.

1986-01-01

Nuclear reactions in the hot accretion plasma surrounding a collapsed star are a source of neutrons, primarily through spallation and pion-producing reactions, and antineutrons, principally through the reaction p+p yields p+p+n+anti-n. We calculate spectra of neutrons and antineutrons produced by a variety of nonthermal energetic particle distributions in which the target particles are either at rest or in motion. If only neutral particles are free to escape the interaction site, a component of the proton and antiproton fluxes in the cosmic radiation results from the neutrons and antineutrons which leave the accretion plasma and subsequently decay in the interstellar medium. This additional antiproton component could account for the enhanced flux of antiprotons in the cosmic radiation, compared to values expected from the standard leaky-box model of cosmic-ray propagation and confinement. Moreover, the low-energy antiproton flux measured by Buffington et al. (1981) could result from target-particle motion in the accretion plasma. This model for the origin of antiprotons predicts a narrow 2.223 MeV line which could be observable.

Moisture-Induced Delayed Alumina Scale Spallation on a Ni(Pt)Al Coating

NASA Technical Reports Server (NTRS)

Smialek, James L.

2009-01-01

Delayed interfacial scale failure takes place after cooling for samples of a Ni(Pt)Al-coated CMSX4 single crystal superalloy, cycled at 1150 C for up to 2000 hr. One sample exhibited premature coating grain boundary wrinkling, alumina scale spallation to bare metal, and a final weight loss of 3.3 mg/cm2 . Spallation under ambient conditions was monitored with time after cooldown and was found to continue for 24 hr. This produced up to 0.05 mg/cm2 additional loss for each hold, accumulating 0.7 mg/cm 2 (20 percent of the total) over the course of the test. After test termination, water immersion produced an additional 0.15 mg/cm2 loss. (A duplicate sample produced much less wrinkling and time dependent spalling, maintaining a net weight gain.) The results are consistent with the general phenomena of moisture-induced delayed spallation (MIDS) of mature, distressed alumina scales formed on oxidation resistant M-Al alloys. Relative ambient humidity is discussed as the factor controlling adsorbed moisture, reaction with the substrate, and hydrogen effects on interface strength.

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

DOE PAGES

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

2016-09-23

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

Vacuum System Upgrade for Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) at SNS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, Christopher M.; Williams, Derrick C.; Price, Jeremy P.

The Extended Q-Range Small-Angle Neutron Scattering Diffractometer (EQ-SANS) instrument at the Spallation Neutron Source (SNS), Oak Ridge, Tennessee, incorporates a 69m3 detector vessel with a vacuum system which required an upgrade with respect to performance, ease of operation, and maintenance. The upgrade focused on improving pumping performance as well as optimizing system design to minimize opportunity for operational error. This upgrade provided the following practical contributions: Reduced time required to evacuate from atmospheric pressure to 2mTorr from 500-1,000 minutes to 60-70 minutes Provided turn-key automated control with a multi-faceted interlock for personnel and machine safety.

Status of the NPDGamma experiment

NASA Astrophysics Data System (ADS)

Fry, J.; Alarcon, R.; Allen, R.; Askanazi, E.; Balascuta, S.; Barron-Palos, L.; Baeßler, S.; Barzilov, A.; Blessinger, C.; Blyth, D.; Bowman, J. D.; Calarco, J. R.; Chupp, T. E.; Coppola, C. E.; Crawford, C.; Craycraft, K.; Dabaghyan, M.; Evans, D.; Favela, J.; Fieseler, C.; Fomin, N.; Fox, W.; Freedman, S.; Frlež, E.; Fu, C.; Garcia, C.; Garishvili, I.; Gericke, M. T.; Gillis, R. C.; Grammer, K.; Greene, G. L.; Hamblen, J.; Hayes, C.; Hersman, F. W.; Ino, T.; Iverson, E. B.; Jones, G. L.; Kabir, L.; Kucucker, S.; Lauss, B.; Li, Y.; Mahurin, R.; Maldonado-Velazquez, M.; McCrea, M.; Masuda, Y.; Mei, J.; Milburn, R.; Mitchell, G. S.; Mueller, P.; Muto, S.; Musgrave, M.; Nann, H.; Novikov, I.; Page, S.; Parsons, D.; Počanić, D.; Penttilä, S. I.; Ramsay, W. D.; Salas-Bacci, A.; Santra, S.; Seo, P.-N.; Sharapov, E.; Sharma, M.; Simmons, F.; Smith, T.; Snow, W. M.; Stuart, J.; Tang, E.; Tang, Z.; Thomison, J.; Tong, T.; Vanderwerp, J.; Waldecker, S.; Wilburn, W. S.; Xu, W.; Yuan, V.; Zhang, Y.

2017-11-01

The NPDGamma experiment measures the parity-violating (PV) gamma asymmetry from polarized cold neutrons captured on protons at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The (PV) neutron spin asymmetry A γ of photons from polarized cold neutron capture on protons is proportional to the Δ I=1 long range weak meson coupling h_{π }1 between nucleons in the hadronic weak interaction (HWI). Liquid para-hydrogen production data taking concluded in April 2014 and once the background aluminum asymmetry measurements are complete, the PV asymmetry A γ can be extracted. Preliminary results of the analysis of A γ are presented.

Spallation studies on shock loaded uranium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tonks, D.L.; Hixson, R.; Gustavsen, R.L.

1997-12-31

Uranium samples at two different purity levels were used for spall strength measurements at three different stress levels. A 50 mm single-stage gas-gun was used to produce planar impact conditions using Z-cut quartz impactors. Samples of depleted uranium were taken from very high purity material and from material that had 300 ppm of carbon added. A pair of shots was done for each impact strength, one member of the pair with VISAR diagnostics and the second with soft recovery for metallographical examination. A series of increasing final stress states were chosen to effectively freeze the microstructural damage at three placesmore » in the development to full spall separation. This allowed determination of the dependence of spall mechanisms on stress level and sample purity. This report will discuss both the results of the metallurgical examination of soft recovered samples and the modeling of the free surface VISAR data. The micrographs taken from the recovered samples show brittle cracking as the spallation failure mechanism. Deformation induced twins are plentiful and obviously play a role in the spallation process. The twins are produced in the initial shock loading and, so, are present already before the fracture process begins. The 1 d characteristics code CHARADE has been used to model the free surface VISAR data.« less

Sulfur and Moisture Effects on Alumina Scale and TBC Spallation

NASA Technical Reports Server (NTRS)

Smialek, James L.

2007-01-01

It has been well established that a few ppmw sulfur impurity may segregate to the interface of thermally grown alumina scales and the underlying substrate, resulting in bond degradation and premature spallation. This has been shown for NiAl and NiCrAl-based alloys, bare single crystal superalloys, or coated superalloys. The role of reactive elements (especially Y) has been to getter the sulfur in the bulk and preclude interfacial segregation. Pt additions are also very beneficial, however a similar thermodynamic explanation does not apply. The purpose of the present discussion is to highlight some observations of these effects on Rene'142, Rene'N5, PWA1480, and PWA1484. For PWA1480, we have mapped cyclic oxidation and spallation in terms of potential sulfur interfacial layers and found that a cumulative amount of about one monolayer is sufficient to degrade long term adhesion. Depending on substrate thickness, optimum performance occurs if sulfur is reduced below about 0.2-0.5 ppmw. This is accomplished in the laboratory by hydrogen annealing or commercially by melt-fluxing. Excellent 1150 C cyclic oxidation is thus demonstrated for desulfurized Rene'142, Rene'N5, and PWA1484. Alternatively, a series of N5 alloys provided by GE-AE have shown that as little as 15 ppmw of Y dopant was effective in providing remarkable scale adhesion. In support of a Y-S gettering mechanism, hydrogen annealing was unable to desulfurize these alloys from their initial level of 5 ppmw S. This impurity and critical doping level corresponds closely to YS or Y2S3 stoichiometry. In many cases, Y-doped alloys or alloys with marginal sulfur levels exhibit an oxidative sensitivity to the ambient humidity called Moisture-Induced Delayed Spallation (MIDS). After substantial scale growth, coupled with damage from repeated cycling, cold samples may spall after a period of time, breathing on them, or immersing them in water. While stress corrosion arguments may apply, we propose that the underlying

Multimaterial lamination as a means of retarding penetration and spallation failures in plates

NASA Technical Reports Server (NTRS)

Dibattista, J. D.; Humes, D. H.

1972-01-01

Experimental data are presented which show that hypervelocity impact spallation and penetration failures of a single solid aluminum plate and of a solid aluminum plate spaced a distance behind a Whipple meteor bumper may be retarded by replacing the solid aluminum plate with a laminated plate. Four sets of experiments were conducted. The first set of experiments was conducted with projectile mass and velocity held constant and with polycarbonate cylinders impacted into single plates of different construction. The second set of experiments was done with single plates of various construction and aluminum spherical projectiles of similar mass but different velocities. These two experiments showed that a laminated plate of aluminum and polycarbonate or aluminum and methyl methacrylate could prevent spallation and penetration failures with a lower areal density than either an all-aluminum laminated plate or a solid aluminum plate. The aluminum laminated plate was in turn superior to the solid aluminum plate in resisting spallation and penetration failures. In addition, through an example of 6061-T6 aluminum and methyl methacrylate, it is shown that a laminated structure ballistically superior to its parent materials may be built. The last two sets of experiments were conducted using bumper-protected main walls of solid aluminum and of laminated aluminum and polycarbonate. Again, under hypervelocity impact conditions, the laminated main walls were superior to the solid aluminum main walls in retarding spallation and penetration failures.

Estimation of neutron dose equivalent at the mezzanine of the Advanced Light Source and the laboratory boundary using the ORNL program MORSE.

PubMed

Sun, R K

1990-12-01

To investigate the radiation effect of neutrons near the Advanced Light Source (ALS) at Lawrence Berkeley Laboratory (LBL) with respect to the neutron dose equivalents in nearby occupied areas and at the site boundary, the neutron transport code MORSE, from Oak Ridge National Laboratory (ORNL), was used. These dose equivalents result from both skyshine neutrons transported by air scattering and direct neutrons penetrating the shielding. The ALS neutron sources are a 50-MeV linear accelerator and its transfer line, a 1.5-GeV booster, a beam extraction line, and a 1.9-GeV storage ring. The most conservative total occupational-dose-equivalent rate in the center of the ALS mezzanine, 39 m from the ALS center, was found to be 1.14 X 10(-3) Sv y-1 per 2000-h "occupational" year, and the total environmental-dose-equivalent rate at the ALS boundary, 125 m from the ALS center, was found to be 3.02 X 10(-4) Sv y-1 per 8760-h calendar year. More realistic dose-equivalent rates, using the nominal (expected) storage-ring current, were calculated to be 1.0 X 10(-4) Sv y-1 and 2.65 X 10(-5) Sv y-1 occupational year and calendar year, respectively, which are much lower than the DOE reporting levels.

Analysis of structure and deformation behavior of AISI 316L tensile specimens from the second operational target module at the Spallation Neutron Source

DOE PAGES

Gussev, Maxim N.; McClintock, David A.; Garner, Frank

2015-08-05

In an earlier publication, tensile testing was performed on specimens removed from the first two operational targets of the Spallation Neutron Source (SNS). There were several anomalous features in the results. First, some specimens had very large elongations (up to 57%) while others had significantly smaller values. Second, there was a larger than the usual amount of data scatter in the elongation results. Third, the stress-strain diagrams of nominally similar specimens spanned a wide range of behavior ranging from expected irradiation-induced hardening to varying levels of force drop after yield point and indirect signs of "traveling deformation wave" behavior associatedmore » with strain-induced martensite formation. To investigate the cause(s) of such variable tensile behavior, several specimens from Target 2, spanning the range of observed tensile behavior, were chosen for detailed microstructural examination using electron backscattering analysis (EBSD). It was also shown that the steel employed in the construction of the target contained an unexpected bimodal grain size distribution, containing very large out-of-specification grains surrounded by necklaces of grains of within-specification sizes. The large grains were frequently comparable to the width of the gauge section of the tensile specimen. Moreover, the propensity to form martensite during deformation was shown to be accelerated by radiation but also to be very sensitive to the relative orientation of the grains with respect to the tensile axis. Specimens having large grains in the gauge that were most favorably oriented for production of martensite strongly exhibited the traveling deformation wave phenomenon, while those specimens with less favorably oriented grains had lesser or no degree of the wave effect, thereby accounting for the larger than expected data scatter.« less

Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

DOE PAGES

Wang, H.; Kirkham, M. J.; Watkins, T. R.; ...

2016-02-17

N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubicmore » symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. Ultimately, this knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.« less

Experimental study of boron-coated straws with a neutron source

NASA Astrophysics Data System (ADS)

Xie, Zhaoyang; Zhou, Jianrong; Song, Yushou; Lacy, Jeffrey L.; Sun, Liang; Sun, Zhijia; Hu, Bitao; Chen, Yuanbo

2018-04-01

Multiple types of high quality neutron detectors are proposed for the first phase of the China Spallation Neutron Source (CSNS), which will be commissioned in 2018. Considering the shortage of 3He supply, a detector module composed of 49 boron-coated straws (BCS) was developed by Proportional Technologies Inc. (PTI). Each straw has a length of 1000 mm and a diameter of 7.5 mm. Seven straws are tightly packed in a tube, and seven tubes are organized in a row to form a detector module. The charge division method is used for longitudinal positioning. A specific readout system was utilized to output the signal and simultaneously encode each straw. The performance of this detector module was studied using a moderated 252Cf source at the Institute of High Energy Physics (IHEP). The signal amplitude spectrum indicates its n-gamma discrimination capability. Despite the complex readout method, a longitudinal resolution of FWHM=6.1 ± 0.5 mm was obtained. The three-dimensional positioning ability qualifies this BCS detector module as a promising detector for small angle neutron scattering.

Applications of compact accelerator-driven neutron sources: An updated assessment from the perspective of materials research in Italy

DOE PAGES

Andreani, C.; Anderson, I. S.; Carpenter, J. M.; ...

2014-12-24

In 2005 the International Atomic Energy Agency (IAEA) in Vienna published a report [1] on ‘Development Opportunities of Small and Medium Scale Accelerator Driven Neutron Sources’ which summarized the prospect of smaller sources in supporting the large spallation neutron sources for materials characterization and instrumentation, a theme advocated by Bauer, Clausen, Mank, and Mulhauser in previous publications [2-4]. In 2010 the Union for Compact Accelerator-driven Neutron Sources (UCANS) was established [5], galvanizing cross-disciplinary collaborations on new source and neutronics development and expanded applications based on both slow-neutron scattering and other neutron-matter interactions of neutron energies ranging from 10⁻⁶ to 10²more » MeV [6]. Here, we first cover the recent development of ongoing and prospective projects of compact accelerator-driven neutron sources (CANS) but concentrate on prospective accelerators currently proposed in Italy. Two active R&D topics, irradiation effects on electronics and cultural heritage studies, are chosen to illustrate the impact of state-of-the-art CANS on these programs with respect to the characteristics and complementarity of the accelerator and neutronics systems as well as instrumentation development.« less

Process technology and effects of spallation products: Circuit components, maintenance, and handling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigg, B.; Haines, S.J.; Dressler, R.

1996-06-01

Working Session D included an assessment of the status of the technology and components required to: (1) remove impurities from the liquid metal (mercury or Pb-Bi) target flow loop including the effects of spallation products, (2) provide the flow parameters necessary for target operations, and (3) maintain the target system. A series of brief presentations were made to focus the discussion on these issues. The subjects of these presentations, and presenters were: (1) Spallation products and solubilities - R. Dressler; (2) Spallation products for Pb-Bi - Y. Orlov; (3) Clean/up/impurity removal components - B. Sigg; (4) {open_quotes}Road-Map{close_quotes} and remote handlingmore » needs - T. McManamy; (5) Remote handling issues and development - M. Holding. The overall conclusion of this session was that, with the exception of (i) spallation product related processing issues, (ii) helium injection and clean-up, and (iii) specialized remote handling equipment, the technology for all other circuit components (excluding the target itself) exists. Operating systems at the Institute of Physics in Riga, Latvia (O. Lielausis) and at Ben-Gurion University in Beer Shiva, Israel (S. Lesin) have demonstrated that other liquid metal circuit components including pumps, heat exchangers, valves, seals, and piping are readily available and have been reliably used for many years. In the three areas listed above, the designs and analysis are not judged to be mature enough to determine whether and what types of technology development are required. Further design and analysis of the liquid metal target system is therefore needed to define flow circuit processing and remote handling equipment requirements and thereby identify any development needs.« less

Spallation processes and nuclear interaction products of cosmic rays.

PubMed

Silberberg, R; Tsao, C H

1990-08-01

Most cosmic-ray nuclei heavier than helium have suffered nuclear collisions in the interstellar gas, with transformation of nuclear composition. The isotopic and elemental composition at the sources has to be inferred from the observed composition near the Earth. The source composition permits tests of current ideas on sites of origin, nucleosynthesis in stars, evolution of stars, the mixing and composition of the interstellar medium and injection processes prior to acceleration. The effects of nuclear spallation, production of radioactive nuclides and the time dependence of their decay provide valuable information on the acceleration and propagation of cosmic rays, their nuclear transformations, and their confinement time in the Galaxy. The formation of spallation products that only decay by electron capture and are relatively long-lived permits an investigation of the nature and density fluctuations (like clouds) of the interstellar medium. Since nuclear collisions yield positrons, antiprotons, gamma rays and neutrinos, we shall discuss these topics briefly.

Comparison of different target material options for the European Spallation Source based on certain aspects related to the final disposal

NASA Astrophysics Data System (ADS)

Kókai, Zsófia; Török, Szabina; Zagyvai, Péter; Kiselev, Daniela; Moormann, Rainer; Börcsök, Endre; Zanini, Luca; Takibayev, Alan; Muhrer, Günter; Bevilacqua, Riccardo; Janik, József

2018-02-01

Different target options have been examined for the European Spallation Source, which is under construction in Lund, Sweden. During the design update phase, parameters and characteristics for the target design have been optimized not only for neutronics but also with respect to the waste characteristics related to the final disposal of the target. A rotating, solid tungsten target was eventually selected as baseline concept; the other options considered included mercury and lead-bismuth (LBE) targets suitable for a pulsed source. Since the licensee is obliged to present a decommissioning plan even before the construction phase starts, the radioactive waste category of the target after full operation time is of crucial importance. The results obtained from a small survey among project partners of 7th Framework Program granted by EU 202247 contract have been used. Waste characteristics of different potential spallation target materials were compared. Based on waste index, the tungsten target is the best alternative and the second one is the mercury target. However, all alternatives have HLW category after a 10 year cooling. Based on heat generation alone all of the options would be below the HLW limit after this cooling period. The LBE is the least advantageous alternative based on waste index and heat generation comparison. These results can be useful in compiling the licensing documents of the ESS facility as the target alternatives can be compared from various aspects related to their disposal.

Study of neutron spectra in a water bath from a Pb target irradiated by 250 MeV protons

NASA Astrophysics Data System (ADS)

Li, Yan-Yan; Zhang, Xue-Ying; Ju, Yong-Qin; Ma, Fei; Zhang, Hong-Bin; Chen, Liang; Ge, Hong-Lin; Wan, Bo; Luo, Peng; Zhou, Bin; Zhang, Yan-Bin; Li, Jian-Yang; Xu, Jun-Kui; Wang, Song-Lin; Yang, Yong-Wei; Yang, Lei

2015-04-01

Spallation neutrons were produced by the irradiation of Pb with 250 MeV protons. The Pb target was surrounded by water which was used to slow down the emitted neutrons. The moderated neutrons in the water bath were measured by using the resonance detectors of Au, Mn and In with a cadmium (Cd) cover. According to the measured activities of the foils, the neutron flux at different resonance energies were deduced and the epithermal neutron spectra were proposed. Corresponding results calculated with the Monte Carlo code MCNPX were compared with the experimental data to check the validity of the code. The comparison showed that the simulation could give a good prediction for the neutron spectra above 50 eV, while the finite thickness of the foils greatly effected the experimental data in low energy. It was also found that the resonance detectors themselves had great impact on the simulated energy spectra. Supported by National Natural Science Foundation and Strategic Priority Research Program of the Chinese Academy of Sciences (11305229, 11105186, 91226107, 91026009, XDA03030300)

New opportunities in quasi elastic neutron scattering spectroscopy

NASA Astrophysics Data System (ADS)

Mezei, F.; Russina, M.

2001-07-01

The high energy resolution usually required in quasi elastic neutron scattering (QENS) spectroscopy is commonly achieved by the use of cold neutrons. This is one of the important research areas where the majority of current work is done on instruments on continuous reactor sources. One particular reason for this is the capability of continuous source time-of-flight spectrometers to use instrumental parameters optimally adapted for best data collection efficiency in each experiment. These parameters include the pulse repetition rate and the length of the pulses to achieve optimal balance between resolution and intensity. In addition, the disc chopper systems used provide perfect symmetrical line shapes with no tails and low background. Recent development of a set of novel techniques enhance the efficiency of cold neutron spectroscopy on existing and future spallation sources in a dramatic fashion. These techniques involve the use of extended pulse length, high intensity coupled moderators, disc chopper systems and advanced neutron optical beam delivery, and they will enable Lujan center at Los Alamos to surpass the best existing reactor instruments in time-of-flight QENS work by more than on order of magnitude in terms of beam flux on the sample. Other applications of the same techniques will allow us to combine advantages of backscattering spectroscopy on continuous and pulsed sources in order to deliver μeV resolution in a very broad energy transfer range.

MCViNE- An object oriented Monte Carlo neutron ray tracing simulation package

DOE PAGES

Lin, J. Y. Y.; Smith, Hillary L.; Granroth, Garrett E.; ...

2015-11-28

MCViNE (Monte-Carlo VIrtual Neutron Experiment) is an open-source Monte Carlo (MC) neutron ray-tracing software for performing computer modeling and simulations that mirror real neutron scattering experiments. We exploited the close similarity between how instrument components are designed and operated and how such components can be modeled in software. For example we used object oriented programming concepts for representing neutron scatterers and detector systems, and recursive algorithms for implementing multiple scattering. Combining these features together in MCViNE allows one to handle sophisticated neutron scattering problems in modern instruments, including, for example, neutron detection by complex detector systems, and single and multiplemore » scattering events in a variety of samples and sample environments. In addition, MCViNE can use simulation components from linear-chain-based MC ray tracing packages which facilitates porting instrument models from those codes. Furthermore it allows for components written solely in Python, which expedites prototyping of new components. These developments have enabled detailed simulations of neutron scattering experiments, with non-trivial samples, for time-of-flight inelastic instruments at the Spallation Neutron Source. Examples of such simulations for powder and single-crystal samples with various scattering kernels, including kernels for phonon and magnon scattering, are presented. As a result, with simulations that closely reproduce experimental results, scattering mechanisms can be turned on and off to determine how they contribute to the measured scattering intensities, improving our understanding of the underlying physics.« less

Two detector arrays for fast neutrons at LANSCE

NASA Astrophysics Data System (ADS)

Haight, R. C.; Lee, H. Y.; Taddeucci, T. N.; O'Donnell, J. M.; Perdue, B. A.; Fotiades, N.; Devlin, M.; Ullmann, J. L.; Laptev, A.; Bredeweg, T.; Jandel, M.; Nelson, R. O.; Wender, S. A.; White, M. C.; Wu, C. Y.; Kwan, E.; Chyzh, A.; Henderson, R.; Gostic, J.

2012-03-01

The neutron spectrum from neutron-induced fission needs to be known in designing new fast reactors, predicting criticality for safety analyses, and developing techniques for global security application. The experimental data base of fission neutron spectra is very incomplete and most present evaluated libraries are based on the approach of the Los Alamos Model. To validate these models and to provide improved data for applications, a program is underway to measure the fission neutron spectrum for a wide range of incident neutron energies using the spallation source of fast neutrons at the Weapons Neutron Research (WNR) facility at the Los Alamos Neutron Science Center (LANSCE). In a double time-of-flight experiment, fission neutrons are detected by arrays of neutron detectors to increase the solid angle and also to investigate possible angular dependence of the fission neutrons. The challenge is to measure the spectrum from low energies, down to 100 keV or so, to energies over 10 MeV, where the evaporation-like spectrum decreases by 3 orders of magnitude from its peak around 1 MeV. For these measurements, we are developing two arrays of neutron detectors, one based on liquid organic scintillators and the other on 6Li-glass detectors. The range of fission neutrons detected by organic liquid scintillators extends from about 600 keV to well over 10 MeV, with the lower limit being defined by the limit of pulse-shape discrimination. The 6Li-glass detectors have a range from very low energies to about 1 MeV, where their efficiency then becomes small. Various considerations and tests are in progress to understand important contributing factors in designing these two arrays and they include selection and characterization of photomultiplier tubes (PM), the performance of relatively thin (1.8 cm) 6Li-glass scintillators on 12.5 cm diameter PM tubes, use of 17.5 cm diameter liquid scintillators with 12.5 cm PM tubes, measurements of detector efficiencies with tagged neutrons

Phase 1 environmental report for the Advanced Neutron Source at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blasing, T.J.; Brown, R.A.; Cada, G.F.

1992-02-01

The US Department of Energy (DOE) has proposed the construction and operation of the Advanced Neutron Source (ANS), a 330-MW(f) reactor, at Oak Ridge National Laboratory (ORNL) to support neutron scattering and nuclear physics experiments. ANS would provide a steady-state source of neutrons that are thermalized to produce sources of hot, cold, and very coal neutrons. The use of these neutrons in ANS experiment facilities would be an essential component of national research efforts in basic materials science. Additionally, ANS capabilities would include production of transplutonium isotopes, irradiation of potential fusion and fission reactor materials, activation analysis, and production ofmore » medical and industrial isotopes such as {sup 252}Cf. Although ANS would not require licensing by the US Nuclear Regulatory Commission (NRC), DOE regards the design, construction, and operation of ANS as activities that would produce a licensable facility; that is, DOE is following the regulatory guidelines that NRC would apply if NRC were licensing the facility. Those guidelines include instructions for the preparation of an environmental report (ER), a compilation of available data and preliminary analyses regarding the environmental impacts of nuclear facility construction and operation. The ER, described and outlined in NRC Regulatory Guide 4.2, serves as a background document to facilitate the preparation of environmental impact statements (EISs). Using Regulatory Guide 4.2 as a model, this ANS ER provides analyses and information specific to the ANS site and area that can be adopted (and modified, if necessary) for the ANS EIS. The ER is being prepared in two phases. Phase 1 ER includes many of the data and analyses needed to prepare the EIS but does not include data or analyses of alternate sites or alternate technologies. Phase 2 ER will include the additional data and analyses stipulated by Regulatory Guide 4.2.« less

Resolution of the VESUVIO spectrometer for High-energy Inelastic Neutron Scattering experiments

NASA Astrophysics Data System (ADS)

Imberti, S.; Andreani, C.; Garbuio, V.; Gorini, G.; Pietropaolo, A.; Senesi, R.; Tardocchi, M.

2005-11-01

New perspectives for epithermal neutron spectroscopy have been opened up as a result of the development of the Resonance Detector and its use on inverse geometry time-of-flight spectrometers at spallation sources. A special application of the Resonance Detector is the Very Low Angle Detector Bank (VLAD) for the VESUVIO spectrometer at ISIS, operating in the angular range 1∘<2θ<5∘. This equipment allows High-energy Inelastic Neutron Scattering (HINS) measurements to be performed in the (q,ω) kinematical region at low wavevector (q<10 Å-1) and high energy (unlimited) transfer ℏω>500 meV, a regime so far inaccessible to experimental studies on condensed matter systems. The HINS measurements complement the Deep Inelastic Neutron Scattering (DINS) measurements performed on VESUVIO in the high wavevector q(20 Å-11 eV), where the short-time single-particle dynamics can be sampled. This paper will revise the main components of the resolution for HINS measurements of VESUVIO. Instrument performances and examples of applications for neutron scattering processes at high energy and at low wavevector transfer are discussed.

Binary neutron star mergers: a review of Einstein's richest laboratory.

PubMed

Baiotti, Luca; Rezzolla, Luciano

2017-09-01

In a single process, the merger of binary neutron star systems combines extreme gravity, the copious emission of gravitational waves, complex microphysics and electromagnetic processes, which can lead to astrophysical signatures observable at the largest redshifts. We review here the recent progress in understanding what could be considered Einstein's richest laboratory, highlighting in particular the numerous significant advances of the last decade. Although special attention is paid to the status of models, techniques and results for fully general-relativistic dynamical simulations, a review is also offered on the initial data and advanced simulations with approximate treatments of gravity. Finally, we review the considerable amount of work carried out on the post-merger phase, including black-hole formation, torus accretion onto the merged compact object, the connection with gamma-ray burst engines, ejected material, and its nucleosynthesis.

Numerical Simulations of Thermo-Mechanical Processes during Thermal Spallation Drilling for Geothermal Reservoirs

NASA Astrophysics Data System (ADS)

Vogler, D.; Walsh, S. D. C.; Rudolf von Rohr, P.; Saar, M. O.

2017-12-01

Drilling expenses constitute a significant share of the upfront capital costs and thereby the associated risks of geothermal energy production. This is especially true for deep boreholes, as drilling costs per meter increase significantly with depth. Thermal spallation drilling is a relatively new drilling technique, particularly suited to the hard crystalline (e.g., basement) rocks in which many deep geothermal resources are located. The method uses a hot jet-flame to rapidly heat the rock surface, which leads to large temperature gradients in the rock. These temperature gradients cause localized thermal stresses that, in combination with the in situ stress field, lead to the formation and ejection of spalls. These spalls are then transported out of the borehole with the drilling mud. Thermal spallation not only in principle enables much faster rates of penetration than traditional rotary drilling, but is also contact-less, which significantly reduces the long tripping times associated with conventional rotary head drilling. We present numerical simulations investigating the influence of rock heterogeneities on the thermal spallation process. Special emphasis is put on different mineral compositions, stress regimes, and heat sources.

Application of thin-film breakdown counters for characterization of neutron field of the VESUVIO instrument at the ISIS spallation source

NASA Astrophysics Data System (ADS)

Smirnov, A. N.; Pietropaolo, A.; Prokofiev, A. V.; Rodionova, E. E.; Frost, C. D.; Ansell, S.; Schooneveld, E. M.; Gorini, G.

2012-09-01

The high-energy neutron field of the VESUVIO instrument at the ISIS facility has been characterized using the technique of thin-film breakdown counters (TFBC). The technique utilizes neutron-induced fission reactions of natU and 209Bi with detection of fission fragments by TFBCs. Experimentally determined count rates of the fragments are ≈50% higher than those calculated using spectral neutron flux simulated with the MCNPX code. This work is a part of the project to develop ChipIr, a new dedicated facility for the accelerated testing of electronic components and systems for neutron-induced single event effects in the new Target Station 2 at ISIS. The TFBC technique has shown to be applicable for on-line monitoring of the neutron flux in the neutron energy range 1-800 MeV at the position of the device under test (DUT).

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

DOEpatents

Bowman, C.D.

1992-11-03

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux

DOEpatents

Bowman, Charles D.

1992-01-01

Apparatus for nuclear transmutation and power production using an intense accelerator-generated thermal neutron flux. High thermal neutron fluxes generated from the action of a high power proton accelerator on a spallation target allows the efficient burn-up of higher actinide nuclear waste by a two-step process. Additionally, rapid burn-up of fission product waste for nuclides having small thermal neutron cross sections, and the practicality of small material inventories while achieving significant throughput derive from employment of such high fluxes. Several nuclear technology problems are addressed including 1. nuclear energy production without a waste stream requiring storage on a geological timescale, 2. the burn-up of defense and commercial nuclear waste, and 3. the production of defense nuclear material. The apparatus includes an accelerator, a target for neutron production surrounded by a blanket region for transmutation, a turbine for electric power production, and a chemical processing facility. In all applications, the accelerator power may be generated internally from fission and the waste produced thereby is transmuted internally so that waste management might not be required beyond the human lifespan.

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

PubMed

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

2005-01-01

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

Conceptual design of the time-of-flight backscattering spectrometer MIRACLES, at the European Spallation Source

NASA Astrophysics Data System (ADS)

Tsapatsaris, N.; Lechner, R. E.; Markó, M.; Bordallo, H. N.

2016-08-01

In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å-1) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations.

Conceptual design of the time-of-flight backscattering spectrometer, MIRACLES, at the European Spallation Source.

PubMed

Tsapatsaris, N; Lechner, R E; Markó, M; Bordallo, H N

2016-08-01

In this work, we present the conceptual design of the backscattering time-of-flight spectrometer MIRACLES approved for construction at the long-pulse European Spallation Source (ESS). MIRACLES's unparalleled combination of variable resolution, high flux, extended energy, and momentum transfer (0.2-6 Å(-1)) ranges will open new avenues for neutron backscattering spectroscopy. Its remarkable flexibility can be attributed to 3 key elements: the long-pulse time structure and low repetition rate of the ESS neutron source, the chopper cascade that tailors the moderator pulse in the primary part of the spectrometer, and the bent Si(111) analyzer crystals arranged in a near-backscattering geometry in the secondary part of the spectrometer. Analytical calculations combined with instrument Monte-Carlo simulations show that the instrument will provide a variable elastic energy resolution, δ(ħ ω), between 2 and 32 μeV, when using a wavelength of λ ≈ 6.267 Å (Si(111)-reflection), with an energy transfer range, ħ ω, centered at the elastic line from -600 to +600 μeV. In addition, when selecting λ ≈ 2.08 Å (i.e., the Si(333)-reflection), δ(ħ ω) can be relaxed to 300 μeV and ħ ω from about 10 meV in energy gain to ca -40 meV in energy loss. Finally, the dynamic wavelength range of MIRACLES, approximately 1.8 Å, can be shifted within the interval of 2-20 Å to allow the measurement of low-energy inelastic excitations.

The n_TOF facility: Neutron beams for challenging future measurements at CERN

NASA Astrophysics Data System (ADS)

Chiaveri, E.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Barbagallo, M.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Colonna, N.; Cortés, G.; Cortés-Giraldo, M. A.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Guerrero, C.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lerendegui-Marco, J.; Meo, S. Lo; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Quesada, J. M.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rubbia, C.; Ryan, J. A.; Sabaté-Gilarte, M.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlachoudis, V.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec, P.

2017-09-01

The CERN n_TOF neutron beam facility is characterized by a very high instantaneous neutron flux, excellent TOF resolution at the 185 m long flight path (EAR-1), low intrinsic background and coverage of a wide range of neutron energies, from thermal to a few GeV. These characteristics provide a unique possibility to perform high-accuracy measurements of neutron-induced reaction cross-sections and angular distributions of interest for fundamental and applied Nuclear Physics. Since 2001, the n_TOF Collaboration has collected a wealth of high quality nuclear data relevant for nuclear astrophysics, nuclear reactor technology, nuclear medicine, etc. The overall efficiency of the experimental program and the range of possible measurements has been expanded with the construction of a second experimental area (EAR-2), located 20 m on the vertical of the n_TOF spallation target. This upgrade, which benefits from a neutron flux 30 times higher than in EAR-1, provides a substantial extension in measurement capabilities, opening the possibility to collect data on neutron cross-section of isotopes with short half-lives or available in very small amounts. This contribution will outline the main characteristics of the n_TOF facility, with special emphasis on the new experimental area. In particular, we will discuss the innovative features of the EAR-2 neutron beam that make possible to perform very challenging measurements on short-lived radioisotopes or sub-mg samples, out of reach up to now at other neutron facilities around the world. Finally, the future perspectives of the facility will be presented.

Clinical trials of boron neutron capture therapy [in humans] [at Beth Israel Deaconess Medical Center][at Brookhaven National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wallace, Christine

2001-05-29

Assessment of research records of Boron Neutron Capture Therapy was conducted at Brookhaven National Laboratory and Beth Israel Deaconess Medical Center using the Code of Federal Regulations, FDA Regulations and Good Clinical Practice Guidelines. Clinical data were collected from subjects' research charts, and differences in conduct of studies at both centers were examined. Records maintained at Brookhaven National Laboratory were not in compliance with regulatory standards. Beth Israel's records followed federal regulations. Deficiencies discovered at both sites are discussed in the reports.

Spallation reaction study for fission products in nuclear waste: Cross section measurements for 137Cs and 90Sr on proton and deuteron

NASA Astrophysics Data System (ADS)

Wang, H.; Otsu, H.; Sakurai, H.; Ahn, D. S.; Aikawa, M.; Doornenbal, P.; Fukuda, N.; Isobe, T.; Kawakami, S.; Koyama, S.; Kubo, T.; Kubono, S.; Lorusso, G.; Maeda, Y.; Makinaga, A.; Momiyama, S.; Nakano, K.; Niikura, M.; Shiga, Y.; Söderström, P.-A.; Suzuki, H.; Takeda, H.; Takeuchi, S.; Taniuchi, R.; Watanabe, Ya.; Watanabe, Yu.; Yamasaki, H.; Yoshida, K.

2016-03-01

We have studied spallation reactions for the fission products 137Cs and 90Sr for the purpose of nuclear waste transmutation. The spallation cross sections on the proton and deuteron were obtained in inverse kinematics for the first time using secondary beams of 137Cs and 90Sr at 185 MeV/nucleon at the RIKEN Radioactive Isotope Beam Factory. The target dependence has been investigated systematically, and the cross-section differences between the proton and deuteron are found to be larger for lighter spallation products. The experimental data are compared with the PHITS calculation, which includes cascade and evaporation processes. Our results suggest that both proton- and deuteron-induced spallation reactions are promising mechanisms for the transmutation of radioactive fission products.

High-efficiency Resonant rf Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seo, P. -N.; Barron-Palos, L.; Bowman, J. D.

2008-01-01

High precision fundamental neutron physics experiments have been proposed for the intense pulsed spallation neutron beams at JSNS, LANSCE, and SNS to test the standard model and search for new physics. Certain systematic effects in some of these experiments have to be controlled at the few ppb level. The NPD Gamma experiment, a search for the small parity-violating {gamma}-ray asymmetry A{sub Y} in polarized cold neutron capture on parahydrogen, is one example. For the NPD Gamma experiment we developed a radio-frequency resonant spin rotator to reverse the neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beammore » with high efficiency over a broad cold neutron energy range. The effect of the spin reversal by the rotator on the neutron beam phase space is compared qualitatively to rf neutron spin flippers based on adiabatic fast passage. We discuss the design of the spin rotator and describe two types of transmission-based neutron spin-flip efficiency measurements where the neutron beam was both polarized and analyzed by optically polarized {sup 3}He neutron spin filters. The efficiency of the spin rotator was measured at LANSCE to be 98.8 {+-} 0.5% for neutron energies from 3 to 20 meV over the full phase space of the beam. Systematic effects that the rf spin rotator introduces to the NPD Gamma experiment are considered.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Expanding Lorentz and spectrum corrections to large volumes of reciprocal space for single-crystal time-of-flight neutron diffraction

DOE PAGES

Michels-Clark, Tara M.; Savici, Andrei T.; Lynch, Vickie E.; ...

2016-03-01

Evidence is mounting that potentially exploitable properties of technologically and chemically interesting crystalline materials are often attributable to local structure effects, which can be observed as modulated diffuse scattering (mDS) next to Bragg diffraction (BD). BD forms a regular sparse grid of intense discrete points in reciprocal space. Traditionally, the intensity of each Bragg peak is extracted by integration of each individual reflection first, followed by application of the required corrections. In contrast, mDS is weak and covers expansive volumes of reciprocal space close to, or between, Bragg reflections. For a representative measurement of the diffuse scattering, multiple sample orientationsmore » are generally required, where many points in reciprocal space are measured multiple times and the resulting data are combined. The common post-integration data reduction method is not optimal with regard to counting statistics. A general and inclusive data processing method is needed. In this contribution, a comprehensive data analysis approach is introduced to correct and merge the full volume of scattering data in a single step, while correctly accounting for the statistical weight of the individual measurements. Lastly, development of this new approach required the exploration of a data treatment and correction protocol that includes the entire collected reciprocal space volume, using neutron time-of-flight or wavelength-resolved data collected at TOPAZ at the Spallation Neutron Source at Oak Ridge National Laboratory.« less

Beam commission of the high intensity proton source developed at INFN-LNS for the European Spallation Source

NASA Astrophysics Data System (ADS)

Neri, L.; Celona, L.; Gammino, S.; Miraglia, A.; Leonardi, O.; Castro, G.; Torrisi, G.; Mascali, D.; Mazzaglia, M.; Allegra, L.; Amato, A.; Calabrese, G.; Caruso, A.; Chines, F.; Gallo, G.; Longhitano, A.; Manno, G.; Marletta, S.; Maugeri, A.; Passarello, S.; Pastore, G.; Seminara, A.; Spartà, A.; Vinciguerra, S.

2017-07-01

At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS) the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started in November 2016. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Promising results were obtained since the first source start with a 6 mm diameter extraction hole. The increase of the extraction hole to 8 mm allowed improving PS-ESS performances and obtaining the values required by the ESS accelerator. In this work, extracted beam current characteristics together with Doppler shift and emittance measurements are presented, as well as the description of the next phases before the installation at ESS in Lund.

Negative pressure and spallation in graphite targets under nano- and picosecond laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belikov, R S; Khishchenko, K V; Krasyuk, I K

We present the results of experiments on the spallation phenomena in graphite targets under shock-wave nano- and picosecond irradiation, which have been performed on Kamerton-T (GPI, Moscow, Russia) and PHELIX (GSI, Darmstadt, Germany) laser facilities. In the range of the strain rates of 10{sup 6} – 10{sup 7} s{sup -1}, the data on the dynamic mechanical strength of the material at rapure (spallation) have been for the first time obtained. With a maximal strain rate of 1.4 × 10{sup 7} s{sup -1}, the spall strength of 2.1 GPa is obtained, which constitutes 64% of the theoretical ultimate tensile strength ofmore » graphite. The effect of spallation is observed not only on the rear side of the target, but also on its irradiated (front) surface. With the use of optical and scanning electron microscopes, the morphology of the front and rear surfaces of the targets is studied. By means of Raman scattering of light, the graphite structure both on the target front surface under laser exposure and on its rear side in the spall zone is investigated. A comparison of the dynamic strength of graphite and synthetic diamond is performed. (extreme light fields and their applications)« less

Looking at hydrogen motions in confinement. The uniqueness of Quasi-Elastic Neutron Scattering

NASA Astrophysics Data System (ADS)

Fischer, J.; Tsapatsaris, N.; de Paula, E.; Bordallo, H. N.

2014-09-01

Why in a barren and hot desert, clays can contain a significant fraction of water? Why does concrete crack? How can we demonstrate that complexation of a drug does not alter its conformation in a way that affects its functionality? In this paper we present results on various studies using Quasi-Elastic Neutron Scattering aimed at clarifying these questions. To allow for a better understanding of neutron scattering, a brief introduction to the basics of its theory is presented. Following the theoretical part, experimental results dealing with the effects of confinement on the water dynamics caused by the interfaces in clays and the nano- and micro-pores of concrete are reviewed in detail. At the end, recent Quasi-Elastic Neutron Scattering investigations on the complexation of the local anesthetics Bupivacaine (BVC.HCl, C18H28N20.HCl.H2O) and Ropivacaine (RVC.HCl, C17H26N20.HCl.H2O) into the cyclic β-cyclodextrin oligosaccharide are presented. To conclude, the perspectives that the European Spallation Source brings to this subject are discussed.

Molecular dynamics simulation of shock wave and spallation phenomena in metal foils irradiated by femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Zhakhovsky, Vasily; Demaske, Brian; Inogamov, Nail; Oleynik, Ivan

2010-03-01

Femtosecond laser irradiation of metals is an effective technique to create a high-pressure frontal layer of 100-200 nm thickness. The associated ablation and spallation phenomena can be studied in the laser pump-probe experiments. We present results of a large-scale MD simulation of ablation and spallation dynamics developing in 1,2,3μm thick Al and Au foils irradiated by a femtosecond laser pulse. Atomic-scale mechanisms of laser energy deposition, transition from pressure wave to shock, reflection of the shock from the rear-side of the foil, and the nucleation of cracks in the reflected tensile wave, having a very high strain rate, were all studied. To achieve a realistic description of the complex phenomena induced by strong compression and rarefaction waves, we developed new embedded atom potentials for Al and Au based on cold pressure curves. MD simulations revealed the complex interplay between spallation and ablation processes: dynamics of spallation depends on the pressure profile formed in the ablated zone at the early stage of laser energy absorption. It is shown that the essential information such as material properties at high strain rate and spall strength can be extracted from the simulated rear-side surface velocity as a function of time.

Delayed Alumina Scale Spallation on Rene'n5+y: Moisture Effects and Acoustic Emission

NASA Technical Reports Server (NTRS)

Smialek, James L.; Morscher, Gregory N.

2001-01-01

The single crystal superalloy Rene'N5 (with or without Y-doping and hydrogen annealing) was cyclically oxidized at 1150 C for 1000 hours. After considerable scale growth (>= 500 hours), even the adherent alumina scales formed on Y-doped samples exhibited delayed interfacial spallation during subsequent water immersion tests, performed up to one year after oxidation. Spallation was characterized by weight loss, the amount of spalled area, and acoustic emission response. Hydrogen annealing (prior to oxidation) reduced spallation both before and after immersion, but without measurably reducing the bulk sulfur content of the Y-doped alloys. The duration and frequency of sequential, co-located acoustic emission events implied an interfacial crack growth rate at least 10(exp -3) m/s, but possibly higher than 10(exp 2) m/s. This is much greater than classic moisture-assisted slow crack growth rates in bulk alumina (10(exp -6) to 10(exp -3) m/s), which may still have occurred undetected by acoustic emission. An alternative failure sequence is proposed: an incubation process for preferential moisture ingress leads to a local decrease in interfacial toughness, thus allowing fast fracture driven by stored strain energy.

Surface modification to prevent oxide scale spallation

DOEpatents

Stephens, Elizabeth V; Sun, Xin; Liu, Wenning; Stevenson, Jeffry W; Surdoval, Wayne; Khaleel, Mohammad A

2013-07-16

A surface modification to prevent oxide scale spallation is disclosed. The surface modification includes a ferritic stainless steel substrate having a modified surface. A cross-section of the modified surface exhibits a periodic morphology. The periodic morphology does not exceed a critical buckling length, which is equivalent to the length of a wave attribute observed in the cross section periodic morphology. The modified surface can be created using at least one of the following processes: shot peening, surface blasting and surface grinding. A coating can be applied to the modified surface.

Neutron capture cross section of ^243Am

NASA Astrophysics Data System (ADS)

Jandel, M.

2009-10-01

The Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL) was used for neutron capture cross section measurement on ^243Am. The high granularity of DANCE (160 BaF2 detectors in a 4π geometry) enables the efficient detection of prompt gamma-rays following neutron capture. DANCE is located on the 20.26 m neutron flight path 14 (FP14) at the Manuel Lujan Jr. Neutron Scattering Center at the Los Alamos Neutron Science Center (LANSCE). The methods and techniques established in [1] were used for the determination of the ^243Am neutron capture cross section. The cross sections were obtained in the range of neutron energies from 0.02 eV to 400 keV. The resonance region was analyzed using SAMMY7 and resonance parameters were extracted. The results will be compared to existing evaluations and calculations. Work was performed under the auspices of the U.S. Department of Energy at Los Alamos National Laboratory by the Los Alamos National Security, LLC under Contract No. DE-AC52-06NA25396 and at Lawrence Livermore National Laboratory by the Lawrence Livermore National Security, LLC under Contract No. DE-AC52-07NA27344. [4pt] [1] M. Jandel et al., Phys. Rev. C78, 034609 (2008)

Operational characteristics of the J-PARC cryogenic hydrogen system for a spallation neutron source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tatsumoto, Hideki; Ohtsu, Kiichi; Aso, Tomokazu

2014-01-29

The J-PARC cryogenic hydrogen system provides supercritical hydrogen with the para-hydrogen concentration of more than 99 % and the temperature of less than 20 K to three moderators so as to provide cold pulsed neutron beams of a higher neutronic performance. Furthermore, the temperature fluctuation of the feed hydrogen stream is required to be within ± 0.25 K. A stable 300-kW proton beam operation has been carried out since November 2012. The para-hydrogen concentrations were measured during the cool-down process. It is confirmed that para-hydrogen always exists in the equilibrium concentration because of the installation of an ortho-para hydrogen convertor.more » Propagation characteristics of temperature fluctuation were measured by temporarily changing the heater power under off-beam condition to clarify the effects of a heater control for thermal compensation on the feed temperature fluctuation. The experimental data gave an allowable temperature fluctuation of ± 1.05 K. It is clarified through a 286-kW and a 524-kW proton beam operations that the heater control would be applicable for the 1-MW proton beam operation by extrapolating from the experimental data.« less

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.

Binary neutron star mergers: a review of Einstein’s richest laboratory

NASA Astrophysics Data System (ADS)

Baiotti, Luca; Rezzolla, Luciano

2017-09-01

In a single process, the merger of binary neutron star systems combines extreme gravity, the copious emission of gravitational waves, complex microphysics and electromagnetic processes, which can lead to astrophysical signatures observable at the largest redshifts. We review here the recent progress in understanding what could be considered Einstein’s richest laboratory, highlighting in particular the numerous significant advances of the last decade. Although special attention is paid to the status of models, techniques and results for fully general-relativistic dynamical simulations, a review is also offered on the initial data and advanced simulations with approximate treatments of gravity. Finally, we review the considerable amount of work carried out on the post-merger phase, including black-hole formation, torus accretion onto the merged compact object, the connection with gamma-ray burst engines, ejected material, and its nucleosynthesis.

Thermal Neutron Imaging Using A New Pad-Based Position Sensitive Neutron Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dioszegi I.; Vanier P.E.; Salwen C.

2016-10-29

Thermal neutrons (with mean energy of 25 meV) have a scattering mean free path of about 20 m in air. Therefore it is feasible to find localized thermal neutron sources up to ~30 m standoff distance using thermal neutron imaging. Coded aperture thermal neutron imaging was developed in our laboratory in the nineties, using He-3 filled wire chambers. Recently a new generation of coded-aperture neutron imagers has been developed. In the new design the ionization chamber has anode and cathode planes, where the anode is composed of an array of individual pads. The charge is collected on each of themore » individual 5x5 mm2 anode pads, (48x48 in total, corresponding to 24x24 cm2 sensitive area) and read out by application specific integrated circuits (ASICs). The high sensitivity of the ASICs allows unity gain operation mode. The new design has several advantages for field deployable imaging applications, compared to the previous generation of wire-grid based neutron detectors. Among these are the rugged design, lighter weight and use of non-flammable stopping gas. For standoff localization of thermalized neutron sources a low resolution (11x11 pixel) coded aperture mask has been fabricated. Using the new larger area detector and the coarse resolution mask we performed several standoff experiments using moderated californium and plutonium sources at Idaho National Laboratory. In this paper we will report on the development and performance of the new pad-based neutron camera, and present long range coded-aperture images of various thermalized neutron sources.« less

Neutron star evolution and emission

NASA Astrophysics Data System (ADS)

Epstein, R. I.; Edwards, B. C.; Haines, T. J.

1997-01-01

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 investigated the evolution and radiation characteristics of individual neutron stars and stellar systems. The work concentrated on phenomena where new techniques and observations are dramatically enlarging the understanding of stellar phenomena. Part of this project was a study of x-ray and gamma-ray emission from neutron stars and other compact objects. This effort included calculating the thermal x-ray emission from young neutron stars, deriving the radio and gamma-ray emission from active pulsars and modeling intense gamma-ray bursts in distant galaxies. They also measured periodic optical and infrared fluctuations from rotating neutron stars and search for high-energy TeV gamma rays from discrete celestial sources.

X-ray microtomography study of the spallation response in Ta-W

NASA Astrophysics Data System (ADS)

McDonald, Samuel; Cotton, Matthew; Millett, Jeremy; Bourne, Neil; Withers, Philip

2013-06-01

The response of metallic materials to high strain-rate (impact) loading is of interest to a number of communities. Traditionally, the largest driver has been the military, in its need to understand armour and resistance to ballistic attack. More recently, industries such as aerospace (foreign object damage, bird strike, etc.), automotive (crash-worthiness) and satellite protection (orbital debris) have all appreciated the necessity of such information. It is therefore important to understand the dynamic tensile or spallation response, and in particular to be able to observe in three-dimensions, and in a non-invasive manner, the physical damage present in the spalled region post-impact. The current study presents plate impact experiments investigating the spallation damage response of recovered targets of the tantalum alloy Ta-2.5%W. Using X-ray microtomography the damage resulting from differing impact conditions (impact velocity/stress, pulse duration) is compared and characterised in 3-D. Combined with free surface velocity measurements, the tensile failure mechanisms during dynamic loading have been identified.

Non-Destructive Study of Bulk Crystallinity and Elemental Composition of Natural Gold Single Crystal Samples by Energy-Resolved Neutron Imaging

PubMed Central

Tremsin, Anton S.; Rakovan, John; Shinohara, Takenao; Kockelmann, Winfried; Losko, Adrian S.; Vogel, Sven C.

2017-01-01

Energy-resolved neutron imaging enables non-destructive analyses of bulk structure and elemental composition, which can be resolved with high spatial resolution at bright pulsed spallation neutron sources due to recent developments and improvements of neutron counting detectors. This technique, suitable for many applications, is demonstrated here with a specific study of ~5–10 mm thick natural gold samples. Through the analysis of neutron absorption resonances the spatial distribution of palladium (with average elemental concentration of ~0.4 atom% and ~5 atom%) is mapped within the gold samples. At the same time, the analysis of coherent neutron scattering in the thermal and cold energy regimes reveals which samples have a single-crystalline bulk structure through the entire sample volume. A spatially resolved analysis is possible because neutron transmission spectra are measured simultaneously on each detector pixel in the epithermal, thermal and cold energy ranges. With a pixel size of 55 μm and a detector-area of 512 by 512 pixels, a total of 262,144 neutron transmission spectra are measured concurrently. The results of our experiments indicate that high resolution energy-resolved neutron imaging is a very attractive analytical technique in cases where other conventional non-destructive methods are ineffective due to sample opacity. PMID:28102285

Studies of molecular diffusion in single-supported bilayer lipid membranes at high hydration by quasielastic neutron scattering

NASA Astrophysics Data System (ADS)

Bai, M.; Miskowiec, A.; Wang, S.-K.; Taub, H.; Hansen, F. Y.; Jenkins, T.; Tyagi, M.; Neumann, D. A.; Diallo, S. O.; Mamontov, E.; Herwig, K. W.

2011-03-01

Bilayer lipid membranes supported on a solid surface are attractive model systems for understanding the structure and dynamics of more complex biological membranes that form the outer boundary of living cells. We have recently obtained quasielastic neutron spectra from single-supported bilayer lipid membranes using the backscattering spectrometer BASIS at the Spallation Neutron Source. Protonated DMPC membranes were deposited onto Si O2 -coated Si(100) substrates and characterized by AFM. Analysis of their neutron spectra shows evidence of a relatively broad Lorentzian component that we associate with bulk-like water above a freezing temperature of ~ 267 K. At lower temperatures, the spectra differ qualitatively from that of bulk supercooled water, a behavior that we attribute to water bound to the membrane. We also find evidence of a narrow Lorentzian component that we tentatively identify with a slower motion (time scale ~ 1 ns) associated with conformational changes of the alkyl tails of the lipid molecules. Supported by NSF Grant No. DMR-0705974.

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

PubMed Central

Achyuthan, Komandoor E.; Allen, Matthew; Denton, Michele L. B.; Siegal, Michael P.; Manginell, Ronald P.

2017-01-01

Abstract Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-doped aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and Kα,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources. PMID:28369631

Strain rate effects for spallation of concrete

NASA Astrophysics Data System (ADS)

Häussler-Combe, Ulrich; Panteki, Evmorfia; Kühn, Tino

2015-09-01

Appropriate triaxial constitutive laws are the key for a realistic simulation of high speed dynamics of concrete. The strain rate effect is still an open issue within this context. In particular the question whether it is a material property - which can be covered by rate dependent stress strain relations - or mainly an effect of inertia is still under discussion. Experimental and theoretical investigations of spallation of concrete specimen in a Hopkinson Bar setup may bring some evidence into this question. For this purpose the paper describes the VERD model, a newly developed constitutive law for concrete based on a damage approach with included strain rate effects [1]. In contrast to other approaches the dynamic strength increase is not directly coupled to strain rate values but related to physical mechanisms like the retarded movement of water in capillary systems and delayed microcracking. The constitutive law is fully triaxial and implemented into explicit finite element codes for the investigation of a wide range of concrete structures exposed to impact and explosions. The current setup models spallation experiments with concrete specimen [2]. The results of such experiments are mainly related to the dynamic tensile strength and the crack energy of concrete which may be derived from, e.g., the velocity of spalled concrete fragments. The experimental results are compared to the VERD model and two further constitutive laws implemented in LS-Dyna. The results indicate that both viscosity and retarded damage are required for a realistic description of the material behaviour of concrete exposed to high strain effects [3].

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

PubMed Central

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

2009-01-01

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

Small Gas Bubble Experiment for Mitigation of Cavitation Damage and Pressure Waves in Short-pulse Mercury Spallation Targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendel, Mark W; Felde, David K; Sangrey, Robert L

2014-01-01

Populations of small helium gas bubbles were introduced into a flowing mercury experiment test loop to evaluate mitigation of beam-pulse induced cavitation damage and pressure waves. The test loop was developed and thoroughly tested at the Spallation Neutron Source (SNS) prior to irradiations at the Los Alamos Neutron Science Center - Weapons Neutron Research Center (LANSCE-WNR) facility. Twelve candidate bubblers were evaluated over a range of mercury flow and gas injection rates by use of a novel optical measurement technique that accurately assessed the generated bubble size distributions. Final selection for irradiation testing included two variations of a swirl bubblermore » provided by Japan Proton Accelerator Research Complex (J-PARC) collaborators and one orifice bubbler developed at SNS. Bubble populations of interest consisted of sizes up to 150 m in radius with achieved gas void fractions in the 10^-5 to 10^-4 range. The nominal WNR beam pulse used for the experiment created energy deposition in the mercury comparable to SNS pulses operating at 2.5 MW. Nineteen test conditions were completed each with 100 pulses, including variations on mercury flow, gas injection and protons per pulse. The principal measure of cavitation damage mitigation was surface damage assessment on test specimens that were manually replaced for each test condition. Damage assessment was done after radiation decay and decontamination by optical and laser profiling microscopy with damaged area fraction and maximum pit depth being the more valued results. Damage was reduced by flow alone; the best mitigation from bubble injection was between half and a quarter that of flow alone. Other data collected included surface motion tracking by three laser Doppler vibrometers (LDV), loop wall dynamic strain, beam diagnostics for charge and beam profile assessment, embedded hydrophones and pressure sensors, and sound measurement by a suite of conventional and contact microphones.« less

High-accuracy determination of the neutron flux in the new experimental area n_TOF-EAR2 at CERN

NASA Astrophysics Data System (ADS)

Sabaté-Gilarte, M.; Barbagallo, M.; Colonna, N.; Gunsing, F.; Žugec, P.; Vlachoudis, V.; Chen, Y. H.; Stamatopoulos, A.; Lerendegui-Marco, J.; Cortés-Giraldo, M. A.; Villacorta, A.; Guerrero, C.; Damone, L.; Audouin, L.; Berthoumieux, E.; Cosentino, L.; Diakaki, M.; Finocchiaro, P.; Musumarra, A.; Papaevangelou, T.; Piscopo, M.; Tassan-Got, L.; Aberle, O.; Andrzejewski, J.; Bécares, V.; Bacak, M.; Baccomi, R.; Balibrea, J.; Barros, S.; Bečvář, F.; Beinrucker, C.; Belloni, F.; Billowes, J.; Bosnar, D.; Brugger, M.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Castelluccio, D. M.; Cerutti, F.; Chiaveri, E.; Cortés, G.; Deo, K.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Frost, R. J. W.; Furman, V.; Göbel, K.; García, A. R.; Gawlik, A.; Gheorghe, I.; Glodariu, T.; Gonçalves, I. F.; González, E.; Goverdovski, A.; Griesmayer, E.; Harada, H.; Heftrich, T.; Heinitz, S.; Hernández-Prieto, A.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Katabuchi, T.; Kavrigin, P.; Ketlerov, V.; Khryachkov, V.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Licata, M.; Lo Meo, S.; Lonsdale, S. J.; Losito, R.; Macina, D.; Marganiec, J.; Martínez, T.; Massimi, C.; Mastinu, P.; Mastromarco, M.; Matteucci, F.; Maugeri, E. A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Mingrone, F.; Mirea, M.; Montesano, S.; Nolte, R.; Oprea, A.; Palomo-Pinto, F. R.; Paradela, C.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, J. I.; Praena, J.; Quesada, J. M.; Rajeev, K.; Rauscher, T.; Reifarth, R.; Riego-Perez, A.; Robles, M. S.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Saxena, A.; Schillebeeckx, P.; Schmidt, S.; Schumann, D.; Sedyshev, P.; Smith, A. G.; Suryanarayana, S. V.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tsinganis, A.; Valenta, S.; Vannini, G.; Variale, V.; Vaz, P.; Ventura, A.; Vlastou, R.; Wallner, A.; Warren, S.; Weigand, M.; Wolf, C.; Woods, P. J.; Weiss, C.; Wright, T.

2017-10-01

A new high flux experimental area has recently become operational at the n_TOF facility at CERN. This new measuring station, n_TOF-EAR2, is placed at the end of a vertical beam line at a distance of approximately 20m from the spallation target. The characterization of the neutron beam, in terms of flux, spatial profile and resolution function, is of crucial importance for the feasibility study and data analysis of all measurements to be performed in the new area. In this paper, the measurement of the neutron flux, performed with different solid-state and gaseous detection systems, and using three neutron-converting reactions considered standard in different energy regions is reported. The results of the various measurements have been combined, yielding an evaluated neutron energy distribution in a wide energy range, from 2meV to 100MeV, with an accuracy ranging from 2%, at low energy, to 6% in the high-energy region. In addition, an absolute normalization of the n_TOF-EAR2 neutron flux has been obtained by means of an activation measurement performed with 197Au foils in the beam.

The accelerator neutron source for boron neutron capture therapy

NASA Astrophysics Data System (ADS)

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

2016-11-01

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

Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandel, M.; Bredeweg, T. A.; Fowler, M. M.

2009-01-28

Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for {sup 241}Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for {sup 243}Am for neutron energies between 10 eV and 250 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on {sup 242m}Am will be presented where the fission events were actively triggered during the experiments. In these experiments, a Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in themore » center of the DANCE array was used as a fission-tagging detector to separate (n,{gamma}) events from (n,f) events. The first direct observation of neutron capture on {sup 242m}Am in the resonance region in between 2 and 9 eV of the neutron energy was obtained.« less

Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jandel, Marian

2008-01-01

Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for {sup 241}Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for {sup 243}Am for neutron energies between 35 eV and 200 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on {sup 242m}Am will be presented, where the fission events were actively triggered during the experiments. In these experiments, the Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in themore » center of the DANCE array was used as a fission-tagging detector to separate (n,{gamma}) from (n,f) events. The first evidence of neutron capture on {sup 242m}Am in the resonance region in between 2 and 9 eV of the neutron energy was obtained.« less

Integrating labview into a distributed computing environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasemir, K. U.; Pieck, M.; Dalesio, L. R.

2001-01-01

Being easy to learn and well suited for a selfcontained desktop laboratory setup, many casual programmers prefer to use the National Instruments Lab-VIEW environment to develop their logic. An ActiveX interface is presented that allows integration into a plant-wide distributed environment based on the Experimental Physics and Industrial Control System (EPICS). This paper discusses the design decisions and provides performance information, especially considering requirements for the Spallation Neutron Source (SNS) diagnostics system.

Radiological assessment of target materials for accelerator transmutation of waste (ATW) applications

NASA Astrophysics Data System (ADS)

Vickers, Linda Diane

This dissertation issues the first published document of the radiation absorbed dose rate (rad-h-1) to tissue from radioactive spallation products in Ta, W, Pb, Bi, and LBE target materials used in Accelerator Transmutation of Waste (ATW) applications. No previous works have provided an estimate of the absorbed dose rate (rad-h-1) from activated targets for ATW applications. The results of this dissertation are useful for planning the radiological safety assessment to personnel, and for the design, construction, maintenance, and disposition of target materials of high-energy particle accelerators for ATW applications (Charlton, 1996). In addition, this dissertation provides the characterization of target materials of high-energy particle accelerators for the parameters of: (1) spallation neutron yield (neutrons/proton), (2) spallation products yield (nuclides/proton), (3) energy-dependent spallation neutron fluence distribution, (4) spallation neutron flux, (5) identification of radioactive spallation products for consideration in safety of personnel to high radiation dose rates, and (6) identification of the optimum geometrical dimensions for the target applicable to the maximum radial spallation neutron leakage from the target. Pb and Bi target materials yielded the lowest absorbed dose rates (rad-h -1) for a 10-year irradiation/50-year decay scheme, and would be the preferred target materials for consideration of the radiological safety of personnel during ATW operations. A beneficial characteristic of these target materials is that they do not produce radioactive transuranic isotopes, which have very long half-lives and require special handling and disposition requirements. Furthermore, the targets are not considered High-Level Waste (HLW) such as reactor spent fuel for disposal purposes. It is a basic ATW system requirement that the spallation target after it has been expended should be disposable as Class C low-level radioactive waste. Therefore, the disposal

Bacterial spores in granite survive hypervelocity launch by spallation: implications for lithopanspermia.

PubMed

Fajardo-Cavazos, Patricia; Langenhorst, Falko; Melosh, H Jay; Nicholson, Wayne L

2009-09-01

Bacterial spores are considered good candidates for endolithic life-forms that could survive interplanetary transport by natural impact processes, i.e., lithopanspermia. Organisms within rock can only embark on an interplanetary journey if they survive ejection from the surface of the donor planet and the associated extremes of compressional shock, heating, and acceleration. Previous simulation experiments have measured each of these three stresses more or less in isolation of one another, and results to date indicate that spores of the model organism Bacillus subtilis can survive each stress applied singly. Few simulations, however, have combined all three stresses simultaneously. Because considerable experimental and theoretical evidence supports a spallation mechanism for launch, we devised an experimental simulation of launch by spallation using the Ames Vertical Gun Range (AVGR). B. subtilis spores were applied to the surface of a granite target that was impacted from above by an aluminum projectile fired at 5.4 km/s. Granite spall fragments were captured in a foam recovery fixture and then recovered and assayed for shock damage by transmission electron microscopy and for spore survival by viability assays. Peak shock pressure at the impact site was calculated to be 57.1 GPa, though recovered spall fragments were only very lightly shocked at pressures of 5-7 GPa. Spore survival was calculated to be on the order of 10(-5), which is in agreement with results of previous static compressional shock experiments. These results demonstrate that endolithic spores can survive launch by spallation from a hypervelocity impact, which lends further evidence in favor of lithopanspermia theory.

How to organize a neutron imaging user lab? 13 years of experience at PSI, CH

NASA Astrophysics Data System (ADS)

Lehmann, E. H.; Vontobel, P.; Frei, G.; Kuehne, G.; Kaestner, A.

2011-09-01

PSI has a relatively long tradition in neutron imaging since the first trials were done at its formerly existing research reactor SAPHIR with film methods. This reactor source was replaced after its shutdown in 1994 by the spallation neutron source SINQ in 1996, driven by the 590 MeV cyclotron for protons with presently up to 2.3 mA beam current. One of the first experimental devices at SINQ was the thermal neutron imaging facility NEUTRA, which was designed from scratch and has been the first device of its kind at a spallation source. Until now, NEUTRA has been successfully in use for many investigations in a wide range of studies covering fuel cell research, environmental behavior of plants, nuclear fuel inspection and the research on cultural heritage objects. It has been the host of PhD projects for students from all over Europe for years. In a previous meeting it has been offered as a European reference facility. Some of its features were really adapted to the layout of new installations. In 2004, it was possible to initiate the project of a second beam line at SINQ for imaging with cold neutrons. Previous studies have shown the potential of this option in order to broaden the user profile and to extend the scientific basis for neutron imaging. It was inaugurated with a workshop at PSI in 2005. The user service was started at the facility ICON in 2006. Beside the setup, installation and optimization of the facilities, the organization of the user program plays an important role. The two neutron imaging beam lines are equal installations at SINQ among the 14 scientific devices. Therefore, the user approach is organized via "calls for proposals", which are sent out each half year via the "Digital User Office (DUO)" (see http://duo.web.psi.ch). The evaluation of the proposals is done by the "Advisory Committee for Neutron Imaging (ACNI)" consisting of 6 external and PSI internal members. Further requests are given by industrial collaborations. This beam time

Characterization of the neutron irradiation system for use in the Low-Dose-Rate Irradiation Facility at Sandia National Laboratories.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franco, Manuel

The objective of this work was to characterize the neutron irradiation system consisting of americium-241 beryllium (241AmBe) neutron sources placed in a polyethylene shielding for use at Sandia National Laboratories (SNL) Low Dose Rate Irradiation Facility (LDRIF). With a total activity of 0.3 TBq (9 Ci), the source consisted of three recycled 241AmBe sources of different activities that had been combined into a single source. The source in its polyethylene shielding will be used in neutron irradiation testing of components. The characterization of the source-shielding system was necessary to evaluate the radiation environment for future experiments. Characterization of the sourcemore » was also necessary because the documentation for the three component sources and their relative alignment within the Special Form Capsule (SFC) was inadequate. The system consisting of the source and shielding was modeled using Monte Carlo N-Particle transport code (MCNP). The model was validated by benchmarking it against measurements using multiple techniques. To characterize the radiation fields over the full spatial geometry of the irradiation system, it was necessary to use a number of instruments of varying sensitivities. First, the computed photon radiography assisted in determining orientation of the component sources. With the capsule properly oriented inside the shielding, the neutron spectra were measured using a variety of techniques. A N-probe Microspec and a neutron Bubble Dosimeter Spectrometer (BDS) set were used to characterize the neutron spectra/field in several locations. In the third technique, neutron foil activation was used to ascertain the neutron spectra. A high purity germanium (HPGe) detector was used to characterize the photon spectrum. The experimentally measured spectra and the MCNP results compared well. Once the MCNP model was validated to an adequate level of confidence, parametric analyses was performed on the model to optimize for potential

Practical in-situ determination of ortho-para hydrogen ratios via fiber-optic based Raman spectroscopy

DOE PAGES

Sutherland, Liese -Marie; Knudson, James N.; Mocko, Michal; ...

2015-12-17

An experiment was designed and developed to prototype a fiber-optic-based laser system, which measures the ratio of ortho-hydrogen to para-hydrogen in an operating neutron moderator system at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source. Preliminary measurements resulted in an ortho to para ratio of 3.06:1, which is within acceptable agreement with the previously published ratio. As a result, the successful demonstration of Raman Spectroscopy for this measurement is expected to lead to a practical method that can be applied for similar in-situ measurements at operating neutron spallation sources.

Practical in-situ determination of ortho-para hydrogen ratios via fiber-optic based Raman spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sutherland, Liese -Marie; Knudson, James N.; Mocko, Michal

An experiment was designed and developed to prototype a fiber-optic-based laser system, which measures the ratio of ortho-hydrogen to para-hydrogen in an operating neutron moderator system at the Los Alamos Neutron Science Center (LANSCE) spallation neutron source. Preliminary measurements resulted in an ortho to para ratio of 3.06:1, which is within acceptable agreement with the previously published ratio. As a result, the successful demonstration of Raman Spectroscopy for this measurement is expected to lead to a practical method that can be applied for similar in-situ measurements at operating neutron spallation sources.

SPES and the neutron facilities at Laboratori Nazionali di Legnaro

NASA Astrophysics Data System (ADS)

Silvestrin, L.; Bisello, D.; Esposito, J.; Mastinu, P.; Prete, G.; Wyss, J.

2016-03-01

The SPES Radioactive Ion Beam (RIB) facility, now in the construction phase at INFN-LNL, has the aim to provide high-intensity and high-quality beams of neutron-rich nuclei for nuclear physics research as well as to develop an interdisciplinary research center based on the cyclotron proton beam. The SPES system is based on a dual-exit high-current cyclotron, with tunable proton beam energy 35-70MeV and 0.20-0.75mA. The first exit is used as proton driver to supply an ISOL system with an UCx Direct Target able to sustain a power of 10kW. The expected fission rate in the target is of the order of 10^{13} fissions per second. The exotic isotopes will be re-accelerated by the ALPI superconducting LINAC at energies of 10 A MeV and higher, for masses around A=130 amu, with an expected beam intensity of 10^7 - 10^9 pps. The second exit will be used for applied physics: radioisotope production for medicine and neutrons for material studies. Fast neutron spectra will be produced by the proton beam interaction with a conversion target. A production rate in excess of 10^{14} n/s can be achieved: this opens up the prospect of a high-flux neutron irradiation facility (NEPIR) to produce both discrete and continuous energy neutrons. A direct proton beam line is also envisaged. NEPIR and the direct proton line would dramatically increase the wide range of irradiation facilities presently available at LNL. We also present LENOS, a proposed project dedicated to accurate neutron cross-sections measurements using intense, well-characterized, broad energy neutron beams. Other activities already in operation at LNL are briefly reviewed: the SIRAD facility for proton and heavy-ion irradiation at the TANDEM-ALPI accelerator and the BELINA test facility at CN van de Graaff accelerator.

Background estimation of cosmic-ray induced neutrons in Chooz site water veto tank for possible future Ricochet Deployment

NASA Astrophysics Data System (ADS)

Silva, James

2017-09-01

The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CE νNS) using metallic superconducting and germanium semi-conducting detectors with sub-keV thresholds placed near a neutrino source such as the Chooz Nuclear Reactor Complex. In this poster, we present an estimate of the flux of cosmic-ray induced neutrons, which represent an important background in any (CE νNS) search, based on reconstructed cosmic ray data from the Chooz Site. We have simulated a possible Ricochet deployment at the Chooz site in GEANT4 focusing on the spallation neutrons generated when cosmic rays interact with the water tank veto that would surround our detector. We further simulate and discuss the effectiveness of various shielding configurations for optimizing the background levels for a future Ricochet deployment.

Ultracold Neutron Sources

NASA Astrophysics Data System (ADS)

Martin, Jeffery

2016-09-01

The free neutron is an excellent laboratory for searches for physics beyond the standard model. Ultracold neutrons (UCN) are free neutrons that can be confined to material, magnetic, and gravitational traps. UCN are compelling for experiments requiring long observation times, high polarization, or low energies. The challenge of experiments has been to create enough UCN to reach the statistical precision required. Production techniques involving neutron interactions with condensed matter systems have resulted in some successes, and new UCN sources are being pursued worldwide to exploit higher UCN densities offered by these techniques. I will review the physics of how the UCN sources work, along with the present status of the world's efforts. research supported by NSERC, CFI, and CRC.

Neutron-capture Cl-36, Ca-41, Ar-36, and Sm-150 in large chondrites: Evidence for high fluences of thermalized neutrons

NASA Technical Reports Server (NTRS)

Bogard, D. D.; Nyquist, L. E.; Bansal, B. M.; Garrison, D. H.; Wiesmann, H.; Herzog, G. F.; Albrecht, A. A.; Vogt, S.; Klein, J.

1995-01-01

We have measured significant concentrations of Cl-36, Ca-41, Ar-36 from decay of Cl-36, and Sm-150 produced from the capture of thermalized neutrons in the large Chico L6 chondrite. Activities of Cl-36 and Ca-41, corrected for a high-energy spallogenic component and a terrestrial age of approximately 50 ka, give average neutron-capture production rates of 208 atoms/min/g-Cl and 1525 atoms/min/kg-Ca, which correspond to thermal neutron (n) fluxes of 6.2 n/sq cm/s and 4.3 n/sq cm/s, respectively. If sustained for the approximately 65 Ma single-stage, cosmic ray exposure age of Chico, these values correspond to thermal neutron fluences of approximately 1.3 x 10(exp 16) and 0.8 x 10(exp 16) n/sq cm for Cl-36 and Ca-41, respectively. Stepwise temperature extraction of Ar in Chico impact melt shows Ar-36/Ar-38 ratios as large as approximately 9. The correlation of high Ar-36/Ar-38 with high Cl/Ca phases in neutron-irradiated Chico indicates that the excess Ar-36 above that expected from spallation is due to decay of neutron-produced Cl-36. Excess Ar-36 in Chico requires a thermal neutron fluence of 0.9-1.7 x 10(exp 16) n/sq cm. Decreases in Sm-149/Sm-152 due to neutron-capture by Sm-149 correlate with increases in Sm-150/Sm-152 for three samples of Chico, and one of the Torino H-chondrite. The 0.08% decrease in Sm-149 shown by Chico corresponds to a neutron fluence of 1.23 x 10(exp 16) n/sq cm. This fluence derived from Sm considers capture of epithermal neutrons and effects of chemical composition on the neutron energy distribution. Excess Ar-36 identified in the Arapahoe, Bruderheim, and Torino chondrites and the Shallowater aubrite suggest exposure to neutron fluences of approximately 0.2-0.2 x 10(exp 16) n/sq cm. Depletion of Sm-149 in Torino and the LEW86010 angrite suggest neutron fluences of 0.8 x 10(exp 16) n/sq cm and 0.25 x 10(exp 16) n/sq cm, respectively. Neutron fluences of approximately 10(exp 16) n/sq cm in Chico are almost as large as those previously

Self-healing effect of spallation damageability

NASA Astrophysics Data System (ADS)

Buravova, S. N.

2017-10-01

The self-healing effect has been found in a study of the microstructure of the bands of localized deformation. It has been shown that interstitial elements (O, C) and the particles of a doping phase migrate to the zone of growing spallation damageability from the matrix material. When considering the wave pattern of the process of localization, it has been ascertained that the formation of bands of localized deformation is accompanied by the process of reverberation which is characterized by the formation of periodically repeated compression-extension cycles. A weak attenuation of the reverberation has led to an increase in the duration of the deformation pulse of the sample by two to three orders of magnitude compared with the time of the initial compression pulse.

Negative pressures and spallation in water drops subjected to nanosecond shock waves

DOE PAGES

Stan, Claudiu A.; Willmott, Philip R.; Stone, Howard A.; ...

2016-05-16

Most experimental studies of cavitation in liquid water at negative pressures reported cavitation at tensions significantly smaller than those expected for homogeneous nucleation, suggesting that achievable tensions are limited by heterogeneous cavitation. We generated tension pulses with nanosecond rise times in water by reflecting cylindrical shock waves, produced by X-ray laser pulses, at the internal surface of drops of water. Depending on the X-ray pulse energy, a range of cavitation phenomena occurred, including the rupture and detachment, or spallation, of thin liquid layers at the surface of the drop. When spallation occurred, we evaluated that negative pressures below –100 MPamore » were reached in the drops. As a result, we model the negative pressures from shock reflection experiments using a nucleation-and-growth model that explains how rapid decompression could outrun heterogeneous cavitation in water, and enable the study of stretched water close to homogeneous cavitation pressures.« less

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

DOE PAGES

Pfeifer, Kent B.; Achyuthan, Komandoor E.; Allen, Matthew; ...

2017-03-25

Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here in this study, the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-dopedmore » aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm 2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and K α,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.« less

Microfabrication of a gadolinium-derived solid-state sensor for thermal neutrons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pfeifer, Kent B.; Achyuthan, Komandoor E.; Allen, Matthew

Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here in this study, the microfabrication of gadolinium (Gd) conversion material–based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W. Post-deposition Gd oxidation–induced spallation was eliminated by growing a residual stress-free 50 nm neodymium-dopedmore » aluminum cap layer atop Gd. The resultant coatings were stable for at least 6 years, demonstrating excellent stability and product shelf-life. Depositing Gd directly on the diode surface eliminated the air gap, leading to a 200-fold increase in electron capture efficiency and facilitating monolithic microfabrication. The conversion electron spectrum was dominated by ICEs with energies of 72, 132 and 174 keV. Results are reported for neutron reflection and moderation by polyethylene for enhanced sensitivity, and γ- and X-ray elimination for improved specificity. The optimal Gd thickness was 10.4 μm for a 300 μm-thick partially depleted diode of 300 mm 2 active surface area. Fast detection (within 10 min) at a neutron source-to-diode distance of 11.7 cm was achieved with this configuration. All ICE energies along with γ-ray and K α,β X-rays were modeled to emphasize correlations between experiment and theory. Semi-conductor thermal neutron detectors offer advantages for field-sensing of radioactive neutron sources.« less

Crystal structure studies with the Paris-Edinburgh cell: Neutron scattering aspects

NASA Astrophysics Data System (ADS)

Loveday, J. S.; Wilson, R. M.; Nelmes, R. J.; Besson, J. M.; Klotz, S.; Hamel, G.; Hull, S.

1994-07-01

The count rates achieved in neutron powder diffraction experiments create difficulties for high-pressure experiments because large sample volumes (˜100 mm3) must be used. Until recently it has been difficult to build suitable pressure cells with such large volumes and hence the maximum pressure for neutron diffraction has remained at the relatively low value of 3 GPa. We have now developed a pressure cell (the Paris-Edinburgh cell) which is capable of exceeding 10 GPa with a sample volume of ˜100 mm3 for use at the U.K. spallation source ISIS. Considerable effort has been devoted to the opimization of the cell, shielding, and detector geometry to enable the best possible data to be recorded. Finite-element calculations to correct for the systematic errors introduced by the attenuation of the pressure-cell materials have been developed and tested. As a result of this work we are now able to obtain accurate structural data to ˜12 GPa and recent studies of phase IV of ND3, the behaviour of the O-D bondlength in D2O ice VIII, and the structural pressure dependence of B4C illustrate the importance of the extension of neutron-diffraction studies to such pressures.

Toward high-efficiency and detailed Monte Carlo simulation study of the granular flow spallation target

NASA Astrophysics Data System (ADS)

Cai, Han-Jie; Zhang, Zhi-Lei; Fu, Fen; Li, Jian-Yang; Zhang, Xun-Chao; Zhang, Ya-Ling; Yan, Xue-Song; Lin, Ping; Xv, Jian-Ya; Yang, Lei

2018-02-01

The dense granular flow spallation target is a new target concept chosen for the Accelerator-Driven Subcritical (ADS) project in China. For the R&D of this kind of target concept, a dedicated Monte Carlo (MC) program named GMT was developed to perform the simulation study of the beam-target interaction. Owing to the complexities of the target geometry, the computational cost of the MC simulation of particle tracks is highly expensive. Thus, improvement of computational efficiency will be essential for the detailed MC simulation studies of the dense granular target. Here we present the special design of the GMT program and its high efficiency performance. In addition, the speedup potential of the GPU-accelerated spallation models is discussed.

S=2 quasi-one-dimensional spin waves in CrCl2

NASA Astrophysics Data System (ADS)

Stone, Matthew; Ehlers, Georg; Granroth, Garrett

2014-03-01

We examine the magnetic excitation spectrum in the S = 2 Heisenberg antiferromagnet CrCl2. Inelastic neutron scattering measurements on powder samples are able to determine the significant exchange interactions in this system. A large anisotropy gap is observed in the spectrum below the Néel temperature and the ratio of the two largest exchange constants is Jc /Jb = 9 . 1 +/- 2 . 2 . However, no sign of a gapped quantum spin liquid excitation was found in the paramagnetic phase. The research was performed at Oak Ridge National Laboratory's Spallation Neutron Source and was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

The O H stretching band in ice Ih derived via eV neutron spectroscopy on VESUVIO using the new very low angle detector bank

NASA Astrophysics Data System (ADS)

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

2006-06-01

Strong demand exists for an experimental facility enabling new experimental investigations on condensed matter systems based on epithermal neutron scattering at high energy and low momentum transfers. This need will be met by the very low angle detector (VLAD) bank, to be installed on the VESUVIO spectrometer at the ISIS spallation neutron source. The equipment will operate in the scattering angular range 1°<2θ<5°. Scattering measurements from a polycrystalline ice sample using a VLAD prototype demonstrates the effectiveness of the detection technique adopted for the construction of the full detector array. The resulting density of states in ice is 9±2 atoms/cell, in agreement with previous measurements.

"Measurements of the neutron spectrum in transit to Mars on the Mars Science Laboratory", Köhler et al.

NASA Astrophysics Data System (ADS)

Miller, Jack

2015-04-01

The Mars Science Laboratory (MSL) spacecraft carried the Curiosity rover to Mars. While the dramatic, successful landing of Curiosity and its subsequent exploration of the Martian surface have justifiably generated great excitement, from the standpoint of the health of crewmembers on missions to Mars, knowledge of the environment between Earth and Mars is critical. This paper reports data taken during the cruise phase of the MSL by the Radiation Assessment Detector (RAD). The results are of great interest for several reasons. They are a direct measurement of the radiation environment during what will be a significant fraction of the duration of a proposed human mission to Mars; they were made behind the de facto shielding provided by various spacecraft components; and, in particular, they are a measurement of the contribution to radiation dose by neutrons. The neutron environment inside spacecraft is produced primarily by galactic cosmic ray ions interacting in shielding materials, and given the high biological effectiveness of neutrons and the increased contribution of neutrons to dose with increased depth in shielding, accurate knowledge of the neutron energy spectrum behind shielding is vital. The results show a relatively modest contribution from neutrons and gammas compared to that from charged particles, but also a discrepancy in both dose and dose rate between the data and simulations. The failure of the calculations to accurately reproduce the data is significant, given that future manned spacecraft will be more heavily shielded (and thus produce more secondary neutrons) and that spacecraft design will rely on simulations and model calculations of radiation transport. The methodology of risk estimation continues to evolve, and incorporates our knowledge of both the physical and biological effects of radiation. The relatively large uncertainties in the biological data, and the difficulties in reducing those uncertainties, makes it all the more important to

DANCE : Device for Measurement of (n.g.) Reactions on radioactive Species /

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chamberlin, E. P.; Dragowsky, M.; Fowler, Malcolm M.

2001-01-01

DANCE (Device for Advanced Neutron Capture Experiments) is a 4{pi} 162 element BaF{sub 2} array under development at Los Alamos National Laboratory. It is designed to provide high granularity, fast timing and high photon detection efficiency. It will be located at the Los Alamos Neutron Scattering Center where neutrons are produced using 800 MeV proton induced spallation reactions on heavy element production targets. Using the pulsed high neutron fluence available at this facility combined with time of flight techniques it will be possible to make neutron capture measurements in the neutron energy range from eV to 100's of keV onmore » rare and radioactive target material at the milligram and below level. These measurements will provide critically needed data for the interpretation of the astrophysical s-process 'branching point' nuclei as well as information for reactions needed in understanding transmutation processes of radioactive species.« less

Generation of negative pressures and spallation phenomena in diamond exposed to a picosecond laser pulse

NASA Astrophysics Data System (ADS)

Abrosimov, S. A.; Bazhulin, A. P.; Bol'shakov, A. P.; Konov, V. I.; Krasyuk, I. K.; Pashinin, P. P.; Ral'chenko, V. G.; Semenov, A. Yu; Sovyk, D. N.; Stuchebryukhov, I. A.; Fortov, V. E.; Khishchenko, K. V.; Khomich, A. A.

2014-06-01

The spallation phenomena in poly- and single-crystal synthetic diamonds have been experimentally investigated. A shockwave impact on a target was implemented using a 70-ps laser pulse in the Kamerton-T facility. The ablation pressure of 0.66 TPa on the front target surface was formed by pulsed radiation of a neodymium phosphate glass laser (second harmonic λ = 0.527 mm, pulse energy 2.5 J) with an intensity as high as 2 × 1013 W cm-2. The maximum diamond spall strength σ* ≈ 16.5 GPa is found to be 24% of the theoretical ultimate strength. Raman scattering data indicate that a small amount of crystalline diamond in the spallation region on the rear side of the target is graphitised.

The physics of neutron stars.

PubMed

Lattimer, J M; Prakash, M

2004-04-23

Neutron stars are some of the densest manifestations of massive objects in the universe. They are ideal astrophysical laboratories for testing theories of dense matter physics and provide connections among nuclear physics, particle physics, and astrophysics. Neutron stars may exhibit conditions and phenomena not observed elsewhere, such as hyperon-dominated matter, deconfined quark matter, superfluidity and superconductivity with critical temperatures near 10(10) kelvin, opaqueness to neutrinos, and magnetic fields in excess of 10(13) Gauss. Here, we describe the formation, structure, internal composition, and evolution of neutron stars. Observations that include studies of pulsars in binary systems, thermal emission from isolated neutron stars, glitches from pulsars, and quasi-periodic oscillations from accreting neutron stars provide information about neutron star masses, radii, temperatures, ages, and internal compositions.

Spallation and fracture resulting from reflected and intersecting stress waves.

NASA Technical Reports Server (NTRS)

Kinslow, R.

1973-01-01

Discussion of the effects of stress waves produced in solid by explosions or high-velocity impacts. These waves rebound from free surfaces in the form of tensile waves that are capable of causing internal fractures or spallation of the material. The high-speed framing camera is shown to be an important tool for observing the stress waves and fracture in transparent targets, and its photographs provide valuable information on the mechanics of fracture.

Hydrocode modeling of the spallation process during hypervelocity impacts: Implications for the ejection of Martian meteorites

NASA Astrophysics Data System (ADS)

Kurosawa, Kosuke; Okamoto, Takaya; Genda, Hidenori

2018-02-01

Hypervelocity ejection of material by impact spallation is considered a plausible mechanism for material exchange between two planetary bodies. We have modeled the spallation process during vertical impacts over a range of impact velocities from 6 to 21 km/s using both grid- and particle-based hydrocode models. The Tillotson equations of state, which are able to treat the nonlinear dependence of density on pressure and thermal pressure in strongly shocked matter, were used to study the hydrodynamic-thermodynamic response after impacts. The effects of material strength and gravitational acceleration were not considered. A two-dimensional time-dependent pressure field within a 1.5-fold projectile radius from the impact point was investigated in cylindrical coordinates to address the generation of spalled material. A resolution test was also performed to reject ejected materials with peak pressures that were too low due to artificial viscosity. The relationship between ejection velocity veject and peak pressure Ppeak was also derived. Our approach shows that "late-stage acceleration" in an ejecta curtain occurs due to the compressible nature of the ejecta, resulting in an ejection velocity that can be higher than the ideal maximum of the resultant particle velocity after passage of a shock wave. We also calculate the ejecta mass that can escape from a planet like Mars (i.e., veject > 5 km/s) that matches the petrographic constraints from Martian meteorites, and which occurs when Ppeak = 30-50 GPa. Although the mass of such ejecta is limited to 0.1-1 wt% of the projectile mass in vertical impacts, this is sufficient for spallation to have been a plausible mechanism for the ejection of Martian meteorites. Finally, we propose that impact spallation is a plausible mechanism for the generation of tektites.

Influence of the nuclear level density on the odd-even staggering in 56Fe+p spallation at energies from 300 to 1500 MeV/nucleon

NASA Astrophysics Data System (ADS)

Su, Jun; Zhu, Long; Guo, Chenchen

2018-05-01

Background: Special attention has been paid to study the shell effect and odd-even staggering (OES) in the nuclear spallation. Purpose: In this paper, we investigate the influence of the nuclear level density on the OES in the 56Fe+p spallations at energies from 300 to 1500 MeV/nucleon. Method: The isospin-dependent quantum molecular dynamics (IQMD) model is applied to produce the highly excited and equilibrium remnants, which is then de-excited using the statistical model gemini. The excitation energy of the heaviest hot fragments is applied to match the IQMD model with the gemini model. In the gemini model, the statistical description of the evaporation are based on the Hauser-Feshbach formalism, in which level density prescriptions are applied. Results: By investigating the OES of the excited pre-fragments, it is found that the OES originates at the end of the decay process when the excitation energy is close to the nucleon-emission threshold energy, i.e., the smaller value of the neutron separation energy and proton separation energy. The strong influence of level density on the OES is noticed. Two types of the nuclear level densities, the discrepancy of which is only about 7% near the nucleon emission threshold energy, are used in the model. However, the calculated values of the OES differ by the factor of 3 for the relevant nuclei. Conclusions: It is suggested that, although the particle-separation energies play a key role in determining the OES, the level density at excitation energy lower than the particle-separation energies should be taken into consideration

Neutron Particle Effects on a Quad-Redundant Flight Control Computer

NASA Technical Reports Server (NTRS)

Eure, Kenneth; Belcastro, Celeste M.; Gray, W Steven; Gonzalex, Oscar

2003-01-01

This paper describes a single-event upset experiment performed at the Los Alamos National Laboratory. A closed-loop control system consisting of a Quad-Redundant Flight Control Computer (FCC) and a B737 simulator was operated while the FCC was exposed to a neutron beam. The purpose of this test was to analyze the effects of neutron bombardment on avionics control systems operating at altitudes where neutron strikes are probable. The neutron energy spectrum produced at the Los Alamos National Laboratory is similar in shape to the spectrum of atmospheric neutrons but much more intense. The higher intensity results in accelerated life tests that are representative of the actual neutron radiation that a FCC may receive over a period of years.

Prompt γ rays and neutrons from fission

NASA Astrophysics Data System (ADS)

Kwan, E.; Wu, C. Y.; Chyzh, A.; Gostic, J.; Henderson, R.; Haight, R. C.; Lee, H. Y.; O'Donnell, J. M.; Perdue, B. A.; Taddeucci, T. N.

2011-10-01

Nuclear data are needed to test the accuracy of calculations from nuclear reaction codes. Information on the prompt γ-ray distributions from fission is sparse and only a handful of published experiments data that measured the prompt γ-ray distribution above incident neutron energies of 1 MeV can be found. In addition, improvement on the accuracy and shape of neutron spectrum from the fission of actinides been requested by the nuclear data community. An investigation on the shapes of the neutron and γ-ray distributions from the spontaneous fission of 252Cf and the neutron-induced fission of 235U was undertaken using the Chi-Nu detector array at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. Preliminary results will be presented. This work is performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and the Los Alamos National Laboratory under Contract DE-AC52-06NA25396.

HEND Maps of Fast Neutrons

NASA Technical Reports Server (NTRS)

2002-01-01

Observations by NASA's 2001 Mars Odyssey spacecraft show a global view of Mars in high-energy, or fast, neutrons. These maps are based on data acquired by the high-energy neutron detector, one of the instruments in the gamma ray spectrometer suite. Fast neutrons, like epithermal neutrons, are sensitive to the presence of hydrogen. Unlike epithermal neutrons, however, they are not affected by the presence of carbon dioxide, which at the time of these observations covered the north polar area as 'dry ice' frost. The low flux of fast neutrons (blue and purple colors) in the north polar region suggests an abundance of hydrogen in the soil comparable to that determined in the south from the flux of epithermal neutrons. These observations were acquired during the first two months of mapping operations. Contours of topography are superimposed on these maps for geographic reference.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson, and NASA's Johnson Space Center, Houston, operate the science instruments. The gamma-ray spectrometer was provided by the University of Arizona in collaboration with the Russian Aviation and Space Agency, which provided the high-energy neutron detector, and the Los Alamos National Laboratories, New Mexico, which provided the neutron spectrometer. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

The effects of shockwave profile shape and shock obliquity on spallation in Cu and Ta: kinetic and stress-state effects on damage evolution(u)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, George T

2010-12-14

Widespread research over the past five decades has provided a wealth of experimental data and insight concerning shock hardening and the spallation response of materials subjected to square-topped shock-wave loading profiles. Less quantitative data have been gathered on the effect of direct, in-contact, high explosive (HE)-driven Taylor wave (or triangular-wave) loading profile shock loading on the shock hardening, damage evolution, or spallation response of materials. Explosive loading induces an impulse dubbed a 'Taylor Wave'. This is a significantly different loading history than that achieved by a square-topped impulse in terms of both the pulse duration at a fixed peak pressure,more » and a different unloading strain rate from the peak Hugoniot state achieved. The goal of this research is to quantify the influence of shockwave obliquity on the spallation response of copper and tantalum by subjecting plates of each material to HE-driven sweeping detonation-wave loading and quantify both the wave propagation and the post-mortem damage evolution. This talk will summarize our current understanding of damage evolution during sweeping detonation-wave spallation loading in Cu and Ta and show comparisons to modeling simulations. The spallation responses of Cu and Ta are both shown to be critically dependent on the shockwave profile and the stress-state of the shock. Based on variations in the specifics of the shock drive (pulse shape, peak stress, shock obliquity) and sample geometry in Cu and Ta, 'spall strength' varies by over a factor of two and the details of the mechanisms of the damage evolution is seen to vary. Simplistic models of spallation, such as P{sub min} based on 1-D square-top shock data lack the physics to capture the influence of kinetics on damage evolution such as that operative during sweeping detonation loading. Such considerations are important for the development of predictive models of damage evolution and spallation in metals and alloys.« less

IPNS upgrade: A feasibility study

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1995-04-01

Many of Argonne National Laboratory`s (ANL`s) scientific staff members were very active in R&D work related to accelerator-based spoliation sources in the 1970s and early 1980s. In 1984, the Seitz/Eastman Panel of the National Academy of Sciences reviewed U.S. materials science research facilities. One of the recommendations of this panel was that the United States build a reactor-based steady-state source, the Advanced Neutron Source (ANS), at Oak Ridge National Laboratory. Subsequently, R&D activities related to the design of an accelerator-based source assumed a lower priority. The resumption of pulsed-source studies in this country started simultaneously with design activities in Europemore » aimed at the European Spallation Source (ESS). The European Community funded a workshop in September 1991 to define the parameters of the ESS. Participants in this workshop included both accelerator builders and neutron source users. A consortium of European countries has proposed to build a 5-MW pulsed source, and a feasibility study is currently under way. Soon after the birth of the ESS, a small group at ANL set about bringing themselves up to date on pulsed-source information since 1984 and studied the feasibility of upgrading ANL`s Intense Pulsed Neutron Source (IPNS) to 1 MW by means of a rapidly cycling synchrotron that could be housed, along with its support facilities, in existing buildings. In early 1993, the Kohn panel recommended that (1) design and construction of the ANS should be completed according to the proposed project schedule and (2) development of competitive proposals for cost-effective design and construction of a 1-MW pulsed spallation source should be authorized immediately.« less

Development of high flux thermal neutron generator for neutron activation analysis

NASA Astrophysics Data System (ADS)

Vainionpaa, Jaakko H.; Chen, Allan X.; Piestrup, Melvin A.; Gary, Charles K.; Jones, Glenn; Pantell, Richard H.

2015-05-01

The new model DD110MB neutron generator from Adelphi Technology produces thermal (<0.5 eV) neutron flux that is normally achieved in a nuclear reactor or larger accelerator based systems. Thermal neutron fluxes of 3-5 · 107 n/cm2/s are measured. This flux is achieved using four ion beams arranged concentrically around a target chamber containing a compact moderator with a central sample cylinder. Fast neutron yield of ∼2 · 1010 n/s is created at the titanium surface of the target chamber. The thickness and material of the moderator is selected to maximize the thermal neutron flux at the center. The 2.5 MeV neutrons are quickly thermalized to energies below 0.5 eV and concentrated at the sample cylinder. The maximum flux of thermal neutrons at the target is achieved when approximately half of the neutrons at the sample area are thermalized. In this paper we present simulation results used to characterize performance of the neutron generator. The neutron flux can be used for neutron activation analysis (NAA) prompt gamma neutron activation analysis (PGNAA) for determining the concentrations of elements in many materials. Another envisioned use of the generator is production of radioactive isotopes. DD110MB is small enough for modest-sized laboratories and universities. Compared to nuclear reactors the DD110MB produces comparable thermal flux but provides reduced administrative and safety requirements and it can be run in pulsed mode, which is beneficial in many neutron activation techniques.

Partial Cross Sections of Neutron-Induced Reactions on nCu at En = 6, 8, 10, 12, 14, and 16 MeV for 0νββ Background Studies

NASA Astrophysics Data System (ADS)

Gooden, M. E.; Fallin, B. A.; Finch, S. W.; Kelley, J. H.; Howell, C. R.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Stanislav, V.

2014-05-01

Partial cross-section measurements of (n,n'γ) reactions on natCu were carried out at TUNL using monoenergetic neutrons at six energies of En = 6, 8, 10, 12, 14, 16 MeV. These studies were performed to provide accurate cross-section data on materials abundant in experimental setups involving HPGe detectors used to search for rare events, like the neutrino-less double-beta decay of 76Ge. Spallation and (α,n) neutrons are expected to cause the largest source of external background in the energy region of interest. At TUNL pulsed neutron beams were produced via the 2H(d,n)3He reaction and the deexcitation γ rays from the reaction natCu(n,xγ) were detected with clover HPGe detectors. Cross-section results for the strongest transtions in 63Cu and 65Cu will be reported, and will compared to model calculations and to data recently obtained at LANL with a white neutron beam.

FY07 LDRD Final Report Neutron Capture Cross-Section Measurements at DANCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, W; Agvaanluvsan, U; Wilk, P

2008-02-08

both Stockpile Stewardship and for nuclear forensics. We focused on the {sup 242m}Am(n,{gamma}) measurement, as there was no existing capture measurement for this isotope. The cross-section measurements (cross section vs. E{sub n}) were made at the Detector for Advanced Neutron Capture Experiments. DANCE is comprised of a highly segmented array of barium fluoride (BaF{sub 2}) crystals specifically designed for neutron capture-gamma measurements, using small radioactive targets (less than one milligram). A picture of half the array, along with a photo of one crystal, is shown in Fig. 1. DANCE provides the world's leading capability for measurements of neutron capture cross sections with radioactive targets. The DANCE is a 4{pi} calorimeter and uses the intense spallation neutron source the Lujan Center at the Los Alamos National Laboratory. The detector array consists of 159 barium fluoride crystals arranged in a sphere around the target.« less

Neutron scattering at the high flux isotope reactor at Oak Ridge National Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yethiraj, M.; Fernandez-Baca, J.A.

Since its beginnings in Oak Ridge and Argonne in the late 1940`s, neutron scattering has been established as the premier tool to study matter in its various states. Since the thermal neutron wavelength is of the same order of magnitude as typical atomic spacings and because they have comparable energies to those of atomic excitations in solids, both structure and dynamics of matter can be studied via neutron scattering. The High Flux Isotope Reactor (HFIR) provides an intense source of neutrons with which to carry out these measurements. This paper summarizes the available neutron scattering facilities at the HFIR.

Neutron spectroscopy measurements of 14 MeV neutrons at unprecedented energy resolution and implications for deuterium-tritium fusion plasma diagnostics

NASA Astrophysics Data System (ADS)

Rigamonti, D.; Giacomelli, L.; Gorini, G.; Nocente, M.; Rebai, M.; Tardocchi, M.; Angelone, M.; Batistoni, P.; Cufar, A.; Ghani, Z.; Jednorog, S.; Klix, A.; Laszynska, E.; Loreti, S.; Pillon, M.; Popovichev, S.; Roberts, N.; Thomas, D.; Contributors, JET

2018-04-01

An accurate calibration of the JET neutron diagnostics with a 14 MeV neutron generator was performed in the first half of 2017 in order to provide a reliable measurement of the fusion power during the next JET deuterium-tritium (DT) campaign. In order to meet the target accuracy, the chosen neutron generator has been fully characterized at the Neutron Metrology Laboratory of the National Physical Laboratory (NPL), Teddington, United Kingdom. The present paper describes the measurements of the neutron energy spectra obtained using a high-resolution single-crystal diamond detector (SCD). The measurements, together with a new neutron source routine ‘ad hoc’ developed for the MCNP code, allowed the complex features of the neutron energy spectra resulting from the mixed D/T beam ions interacting with the T/D target nuclei to be resolved for the first time. From the spectral analysis a quantitative estimation of the beam ion composition has been made. The unprecedented intrinsic energy resolution (<1% full width at half maximum (FWHM) at 14 MeV) of diamond detectors opens up new prospects for diagnosing DT plasmas, such as, for instance, the possibility to study non-classical slowing down of the beam ions by neutron spectroscopy on ITER.

Improved design of proton source and low energy beam transport line for European Spallation Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neri, L., E-mail: neri@lns.infn.it; Celona, L.; Gammino, S.

2014-02-15

The design update of the European Spallation Source (ESS) accelerator is almost complete and the construction of the prototype of the microwave discharge ion source able to provide a proton beam current larger than 70 mA to the 3.6 MeV Radio Frequency Quadrupole (RFQ) started. The source named PS-ESS (Proton Source for ESS) was designed with a flexible magnetic system and an extraction system able to merge conservative solutions with significant advances. The ESS injector has taken advantage of recent theoretical updates and new plasma diagnostics tools developed at INFN-LNS (Laboratori Nazionali del Sud, Istituto Nazionale di Fisica Nucleare). Themore » design strategy considers the PS-ESS and the low energy beam transport line as a whole, where the proton beam behaves like an almost neutralized non-thermalized plasma. Innovative solutions have been used as hereinafter described. Thermo-mechanical optimization has been performed to withstand the chopped beam and the misaligned focused beam over the RFQ input collimator; the results are reported here.« less

Physics in Strong Magnetic Fields Near Neutron Stars.

ERIC Educational Resources Information Center

Harding, Alice K.

1991-01-01

Discussed are the behaviors of particles and energies in the magnetic fields of neutron stars. Different types of possible research using neutron stars as a laboratory for the study of strong magnetic fields are proposed. (CW)

Improved Determination of the Neutron Lifetime

NASA Astrophysics Data System (ADS)

Yue, A.

2013-10-01

The most precise determination of the neutron lifetime using the beam method reported a result of τn = (886 . 3 +/- 3 . 4) s. The dominant uncertainties were attributed to the absolute determination of the fluence of the neutron beam (2.7 s). The fluence was determined with a monitor that counted the neutron-induced charged particles from absorption in a thin, well-characterized 6Li deposit. The detection efficiency of the monitor was calculated from the areal density of the deposit, the detector solid angle, and the ENDF/B-VI 6Li(n,t)4He thermal neutron cross section. We have used a second, totally-absorbing neutron detector to directly measure the detection efficiency of the monitor on a monochromatic neutron beam of precisely known wavelength. This method does not rely on the 6Li(n,t)4He cross section or any other nuclear data. The monitor detection efficiency was measured to an uncertainty of 0.06%, which represents a five-fold improvement in uncertainty. We have verified the temporal stability of the monitor with ancillary measurements, and the measured neutron monitor efficiency has been used to improve the fluence determination in the past lifetime experiment. An updated neutron lifetime based on the improved fluence determination will be presented. Work done in collaboration with M. Dewey, D. Gilliam, J. Nico, National Institute of Standards and Technology; G. Greene, University of Tennessee / Oak Ridge National Laboratory; A. Laptev, Los Alamos National Laboratory; W. Snow, Indiana University; and F. Wietfeldt, Tulane University.

Neutron detectors for the ESS diffractometers

NASA Astrophysics Data System (ADS)

Stefanescu, I.; Christensen, M.; Fenske, J.; Hall-Wilton, R.; Henry, P. F.; Kirstein, O.; Müller, M.; Nowak, G.; Pooley, D.; Raspino, D.; Rhodes, N.; Šaroun, J.; Schefer, J.; Schooneveld, E.; Sykora, J.; Schweika, W.

2017-01-01

The ambitious instrument suite for the future European Spallation Source whose civil construction started recently in Lund, Sweden, demands a set of diverse and challenging requirements for the neutron detectors. For instance, the unprecedented high flux expected on the samples to be investigated in neutron diffraction or reflectometry experiments requires detectors that can handle high counting rates, while the investigation of sub-millimeter protein crystals will only be possible with large-area detectors that can achieve a position resolution as low as 200 μm. This has motivated an extensive research and development campaign to advance the state-of-the-art detector and to find new technologies that can reach maturity by the time the ESS will operate at full potential. This paper presents the key detector requirements for three of the Time-of-Flight (TOF) diffraction instrument concepts selected by the Scientific Advisory Committee to advance into the phase of preliminary engineering design. We discuss the detector technologies commonly employed at the existing similar instruments and their major challenges for ESS. The detector technologies selected by the instrument teams to collect the diffraction patterns are also presented. Analytical calculations, Monte-Carlo simulations, and real experimental data are used to develop a generic method to estimate the event rate in the diffraction detectors. We apply this method to make predictions for the future diffraction instruments, and thus provide additional information that can help the instrument teams with the optimisation of the detector designs.

Mercury Thermal Hydraulic Loop (MTHL) Summary Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Felde, David K.; Crye, Jason Michael; Wendel, Mark W.

2017-03-01

The Spallation Neutron Source (SNS) is a high-power linear accelerator built at Oak Ridge National Laboratory (ORNL) which incorporates the use of a flowing liquid mercury target. The Mercury Thermal Hydraulic Loop (MTHL) was constructed to investigate and verify the heat transfer characteristics of liquid mercury in a rectangular channel. This report provides a compilation of previously reported results from the water-cooled and electrically heated straight and curved test sections that simulate the geometry of the window cooling channel in the target nose region.

Measurements of the thermal neutron flux for an accelerator-based photoneutron source.

PubMed

Taheri, Ali; Pazirandeh, Ali

2016-12-01

To have access to an appropriate neutron source is one of the most demanding requirements for neutron studies. This is important specially in laboratory and clinical applications, which need more compact and accessible sources. The most known neutron sources are fission reactors and natural isotopes, but there is an increasing interest for using accelerator based neutron sources because of their advantages. In this paper, we shall present a photo-neutron source prototype which is designed and fabricated to be used for different neutron researches including in-laboratory neutron activation analysis and neutron imaging, and also preliminary studies in boron neutron capture therapy (BNCT). Series of experimental tests were conducted to examine the intensity and quality of the neutron field produced by this source. Monte-Carlo simulations were also utilized to provide more detailed evaluation of the neutron spectrum, and determine the accuracy of the experiments. The experiments demonstrated a thermal neutron flux in the order of 10 7 (n/cm 2 .s), while simulations affirmed this flux and showed a neutron spectrum with a sharp peak at thermal energy region. According to the results, about 60 % of produced neutrons are in the range of thermal to epithermal neutrons.