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Sample records for choppers neutron

  1. Neutron chopper development at LANSCE

    International Nuclear Information System (INIS)

    Progress is reported on neutron chopper systems for the Los Alamos Neutron Scattering Center pulsed spallation neutron source. This includes the development of 600+ Hz active magnetic bearing neutron chopper and a high speed control system designed to operate with the Proton Storage Ring to phase the chopper to the neutron source. 5 refs., 3 figs

  2. A microprocessor system for a neutron chopper

    International Nuclear Information System (INIS)

    An electronic system with the use of a microprocessor for operation automation, stabilization of speed and phase in the IBR-2 neutron chopper sis described. The root mean square deviation of chopper phase for 5 Hz frequency of reactor operation does not exceed 50 μs

  3. IPNS accelerator system and neutron chopper synchronization

    International Nuclear Information System (INIS)

    Several of the neutron scattering instruments at the Intense Pulsed Neutron Source (IPNS) at Argonne use neutron choppers for monochromatization of the neutron beam. Since the neutron burst is produced by a proton beam extracted from the Rapid Cycling Synchrotron (RCS), precise synchronization must be maintained between the RCS and the chopper aperture to minimize the degradation of energy resolution. The first attempts at synchronization were made in 1978 on the ZING-P' facility with a single chopper. Synchronization was further complicated after IPNS began operating in 1981 when a total of three chopper experiments came on-line. The system in use during that period of time was able to maintain synchronization with typical data collection efficiencies ranging from 20 to 70%. A synchronization system improvement, installed in late 1982, increased the data collection efficiencies of all the IPNS chopper systems to 99+%. The development of the RCS and neutron chopper synchronization system is described together with a detailed description of the present system

  4. Introduction to modern chopper spectrometers for pulsed neutron sources

    International Nuclear Information System (INIS)

    Introduction to the latest modern chopper spectrometers for pulsed neutron sources is shown. After coming up of recent high-performance pulsed neutron sources such as J-PARC, SNS and 2nd target station of ISIS, much progress have been achieved in technology regarding to chopper spectrometers in both hardware and software. A multi-Ei measurement based on repetition rate multiplication technique alters strategy of the measurements. Source pulse shaping provides opportunity precise measurements with high intensity. Current data analysis software enables us to access to the four dimensional space in energy and momentum transfers. (author)

  5. Chopper spectrometer (2). Toward the expansion of observation area in inelastic neutron scattering

    International Nuclear Information System (INIS)

    The High Resolution Chopper Spectrometer (HRC) was installed and is being operated at BL12 of J-PARC/MLF to study condensed matter dynamics with high resolutions using relatively high energy neutrons. The Polarized Neutron Spectrometer (POLANO) is being constructed at BL23 to utilize polarized neutrons for dynamical studies. We hope that these two chopper spectrometers provide an opportunity to expand the observation area in inelastic neutron scattering experiments by using high energy neutrons and polarized neutrons with a good sample environment. (author)

  6. Chopper spectrometers

    International Nuclear Information System (INIS)

    Chopper spectrometers are devices which measure the dynamics of condensed systems expressed in terms of the scattering function. The scattering function depends on the energy and momentum transfers which are related to the initial and final neutron wave vectors. The resolution of the instrument is limited by the time-of-flight measurements on the scattered beam but the wide range of accessible energy and momentum transfers make chopper spectrometers popular. Several examples of experiments using chopper spectrometers are presented

  7. Development of a fast traveling-wave beam chopper for the National Spallation Neutron Source

    International Nuclear Information System (INIS)

    High current and severe restrictions on beam losses, below 1 nA/m, in the designed linac for the National Spallation Neutron Source (NSNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns to accommodate a 402.5-MHz beam structure--beam chopping in its front end, at the beam energy 2.5 MeV. The R and D program includes both modification of the existing LANSCE coax-plate chopper to reduce parasitic coupling between adjacent plates, and development of new traveling-wave deflecting structures, in particular, based on a meander line. Using analytical methods and three-dimensional time-domain computer simulations the authors study transient effects in such structures to choose an optimal chopper design

  8. Contamination from the next higher incident energy in inelastic neutron scattering measurements with multiple incident energies on chopper spectrometers

    International Nuclear Information System (INIS)

    A highly efficient measurement technique utilizing multiple incident energies (Eis) simultaneously on a neutron chopper spectrometer has recently become popular in inelastic neutron scattering studies of condensed matter. However, the inelastic scattering spectrum of a target incident energy can be contaminated by the scattering process of other Eis. In this study, we quantitatively evaluated the extent to which the spectrum of a target Ei in this type of measurement can be contaminated by the scattering process of the next higher Ei. We estimated the relative intensity of the scattering from the next higher Ei for the neutron chopper spectrometers 4SEASONS and AMATERAS at the Japan Proton Accelerator Research Complex (J-PARC)

  9. Study of converging neutron guides for the cold neutron double-chopper spectrometer at J-PARC

    Energy Technology Data Exchange (ETDEWEB)

    Kajimoto, Ryoichi [Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan)]. E-mail: ryoichi.kajimoto@j-parc.jp; Nakamura, Mitsutaka [Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Osakabe, Toyotaka [Advanced Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Sato, Taku J. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Tokai, Ibaraki 316-1106 (Japan); Nakajima, Kenji [Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan); Arai, Masatoshi [Neutron Science Research Center, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195 (Japan)

    2006-11-15

    Performance of converging neutron guides was studied for the cold neutron double-chopper spectrometer proposed for the spallation neutron source at J-PARC. Intensity, spatial distribution, and angular distribution of a neutron beam at a sample are compared for linearly tapered and elliptic geometries by Monte Carlo simulation. For low-energy neutrons, the flux on the sample is much increased by an elliptic geometry whose focal points are on the moderator and on the sample in compensation for the angular resolution. To keep a substantial gain for a wide energy range, an elliptic guide with one of the focal points far behind the moderator is better. It also gives good spatial and angular intensity profiles at the sample.

  10. The Cold Neutron Chopper Spectrometer at the Spallation Neutron Source - A Review of the first 8 Years of Operation

    CERN Document Server

    Ehlers, Georg; Kolesnikov, Alexander I

    2016-01-01

    The first eight years of operation of the Cold Neutron Chopper Spectrometer (CNCS) at the Spallation Neutron Source in Oak Ridge is being reviewed. The instrument has been part of the facility user program since 2009, and more than 250 individual user experiments have been performed to date. CNCS is an extremely powerful and versatile instrument and offers leading edge performance in terms of beam intensity, energy resolution, and flexibility to trade one for another. Experiments are being routinely performed with the sample at extreme conditions: T~0.05K, p>=2GPa and B=8T 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.

  11. Design and operation of the wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source.

    Science.gov (United States)

    Abernathy, D L; Stone, M B; Loguillo, M J; Lucas, M S; Delaire, O; Tang, X; Lin, J Y Y; Fultz, B

    2012-01-01

    The wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source (SNS) is optimized to provide a high neutron flux at the sample position with a large solid angle of detector coverage. The instrument incorporates modern neutron instrumentation, such as an elliptically focused neutron guide, high speed magnetic bearing choppers, and a massive array of (3)He linear position sensitive detectors. Novel features of the spectrometer include the use of a large gate valve between the sample and detector vacuum chambers and the placement of the detectors within the vacuum, both of which provide a window-free final flight path to minimize background scattering while allowing rapid changing of the sample and sample environment equipment. ARCS views the SNS decoupled ambient temperature water moderator, using neutrons with incident energy typically in the range from 15 to 1500 meV. This range, coupled with the large detector coverage, allows a wide variety of studies of excitations in condensed matter, such as lattice dynamics and magnetism, in both powder and single-crystal samples. Comparisons of early results to both analytical and Monte Carlo simulation of the instrument performance demonstrate that the instrument is operating as expected and its neutronic performance is understood. ARCS is currently in the SNS user program and continues to improve its scientific productivity by incorporating new instrumentation to increase the range of science covered and improve its effectiveness in data collection. PMID:22299993

  12. A new chopper spectrometer for neutron Brillouin scattering and low-angle neutron inelastic scattering: PHAROS (Phase 1)

    International Nuclear Information System (INIS)

    Phase I of PHAROS, the new chopper spectrometer at LANSCE, is described in detail. The main components are a water moderator, a 60-Hz double-bladed T-zero chopper, a 600Hz magnetic-bearing Fermi chopper, a 6m-long vacuum vessel with thin aluminium-alloy vacuum window and a 1.2m2 array of linear position-sensitive detectors

  13. A high-resolution disk chopper with two-stage rotors for neutron time-of-flight spectroscopy

    Science.gov (United States)

    Ono, Masayoshi

    1997-02-01

    Two-stage three-rotor disk chopper has been designed and constructed with the aim of bringing the resolution of crystal lattive strain ° d/ d = 10 -4-10 -5. The first two of them rotate at 150 rps in reverse directions from each other by a timing-belt system. This means that the actual rotation speed becomes 300 rps. The last rotor rotates as a tail-cutter for TOF measurements. The highest time resolution of the present Bragg scattering set-up is about 15 μs for 2 Å neutrons, realizing ° {d}/{d}<10 -4.

  14. A high-resolution disk chopper with two-stage rotors for neutron time-of-flight spectroscopy

    International Nuclear Information System (INIS)

    Two-stage three-rotor disk chopper has been designed and constructed with the aim of bringing the resolution of crystal lattice strain δd/d=10-4-10-5. The first two of them rotate at 150 rps in reverse directions from each other by a timing-belt system. This means that the actual rotation speed becomes 300 rps. The last rotor rotates as a tail-cutter for TOF measurements. The highest time resolution of the present Bragg scattering set-up is about 15 μs for 2 A neutrons, realizing δd/d-4. (orig.)

  15. Spectrum measurements in the ZENITH plutonium core 7 using a neutron chopper

    International Nuclear Information System (INIS)

    As part of the experimental programme on the first plutonium loading of ZENITH (Core 7) a series of measurements was carried out with the neutron chopper on a beam emerging from the core centre. The general experimental programme on the two ZENITH plutonium cores has been covered elsewhere. Core 7 had a carbon/Pu239 atomic ratio of 2666 and a steel/Pu239 ratio of 76.8, giving an absorption cross-section at 2200 m/sec. of 0.31 barns/carbon atom. The fuel was in the form of 'spikes' of 0.020 in. thick Pu/Al alloy sheathed in 0.020 in. aluminium, the isotopic composition of the plutonium being 97.4% Pu239, 2.55% Pu240 and 0.1% Pu241. The overall layout of the reactor core and reflector is shown in the vertical section through the reactor vessel and the plan view. The core consists of a vertical array of 235 cylindrical graphite sleeves of outer diameter 7.37 cm into each of which a cylindrical graphite box may be loaded. Sunning longitudinally inside the box are six parallel grooves which act as locations for the edges of either the Pu/Al spikes or graphite dummies of the same external dimensions. Each groove accommodates two spikes end-to-end, with a small graphite spacer between to avoid welding together of the spike sheaths when heated. Lateral spacers of graphite or stainless steel fill the five spaces between the six spikes or dummies. The total length of the plutonium-loaded core region is 140 cm, the ends of the element forming graphite reflectors of length 53 cm. In Core 7 each fuel element contained 10 Pu-Al spikes. The fuel elements are arranged in a triangular lattice of pitch 7.62 cm to form the reactor core, of diameter 1.23 m. A radial graphite reflector approximately 1 metre thick surrounds the core and is separated from it by an annular lampblack thermal barrier, contained within graphite tiles, which reduces heat transfer from the core. The reactor can be heated by circulation of nitrogen through a 250 kW heater below the core. The nitrogen flows

  16. Development and applications of the reverse neutron time-of-flight method with Fourier-type beam chopper

    International Nuclear Information System (INIS)

    The neutron powder diffraction method has been applied to the crystal structure analysis of high-temperature superconductors such as La0.8Sr0.2CuO4-y, YBa2Cu3O7-y and Bi2Sr2CaCu2O8+y optically active yttriumformate Y(HCOO)3, and β phase of deuterated acetonitrile, CD3CN. The structural information, containing symmetry, positional and thermal parameters, occupation factors and the order parameter, was obtained by measuring the coherent elastic scattering cross-section. The Rietveld profile refinement method was used for the extraction of structural parameters from experimental data. The diffraction spectra were obtained by measuring the time-of-flight distribution of neutrons with a Fourier-type beam chopper. The neutron diffraction spectrum is created by the on-line synthesis of the cross-correlation function between the beam modulation function and the detector intensity. Such an operational mode, called the reverse time-of-flight method, has many unique properties. The possibility of filtering out a low-frequency part of a diffraction spectrum, eg. incoherent background, by a properly selected band-pass filter has been studied. One of the practical applications of the reverse time-of-flight method, the Mini-Sfinks facility, is described with technical details, and its operational characteristics are compared with other high-resolution instruments

  17. IPNS Chopper Control and Accelerator Interface Systems

    International Nuclear Information System (INIS)

    Several of the instruments at the Intense Pulsed Neutron Source (IPNS) at Argonne use rotating Fermi choppers. The techniques used to control the speed and phase of these rotating devices are discussed

  18. Conceptual design of a Disk Chopper Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Copley, J.R.D. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    1997-09-01

    We describe methods that we have used for the conceptual design of the Disk Chopper Spectrometer at the Cold Neutron Research Facility, National Institute of Standards and Technology. Most of the discussion concerns the multiple chopper system. No single design method is best in every situation. We believe that an analytical approach is preferable, whenever possible. Graphical methods of expressing problems have been very instructive. We have also found it useful, and occasionally invaluable, to cross-check results obtained using different methods, such as analytical integration and ray-tracing.

  19. Uhv compatible chopper system

    International Nuclear Information System (INIS)

    A time-of-flight system utilizing a novel mechanical chopper has been developed to measure the energy spectrum of neutral deuterium atoms emitted from a tokamak plasma. The chopper system consists of a motor, a magnetically levitated shaft, and a chopper disc. The 20 g disc is rigidly attached to a 159 g shaft assembly and the set is supported against gravity in vacuum by permanent magnets and a stabilizing servo system. All components are uhv compatible to avoid contamination to the tokamak and to the detector. The 25.4 cm OD, .005 cm thick, 301 stainless steel chopper disc has 24 .025 cm wide slots photoetched at an 11.4 cm radius. An effective aperture time of .55 μs is achieved during typical steady state operation at 22,500 rpm with a vacuum pressure of 2 x 10-8 torr

  20. Uhv compatible chopper system

    Energy Technology Data Exchange (ETDEWEB)

    Voss, D.E.; Cohen, S.A.

    1979-11-01

    A time-of-flight system utilizing a novel mechanical chopper has been developed to measure the energy spectrum of neutral deuterium atoms emitted from a tokamak plasma. The chopper system consists of a motor, a magnetically levitated shaft, and a chopper disc. The 20 g disc is rigidly attached to a 159 g shaft assembly and the set is supported against gravity in vacuum by permanent magnets and a stabilizing servo system. All components are uhv compatible to avoid contamination to the tokamak and to the detector. The 25.4 cm OD, .005 cm thick, 301 stainless steel chopper disc has 24 .025 cm wide slots photoetched at an 11.4 cm radius. An effective aperture time of .55 ..mu..s is achieved during typical steady state operation at 22,500 rpm with a vacuum pressure of 2 x 10/sup -8/ torr.

  1. Experimental results of an ExB chopper system

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Christoph; Dinter, Hannes; Droba, Martin; Meusel, Oliver; Noll, Daniel; Nowottnick, Tobias; Payir, Onur; Ratzinger, Ulrich; Schneider, Philipp [IAP, Goethe-Universitaet Frankfurt, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2014-07-01

    A new chopper system for low-energy high-perveance beams and high repetition rates was developed for the Low Energy Beam Transport (LEBT) section of the accelerator-driven neutron source FRANZ. The chopper combines a static magnetic deflection field with a pulsed electric compensation field in a Wien filter-type E x B configuration. The total system length is 80 cm. Successful beam operation of the chopper has started. Helium beams with 14 keV energy were chopped with the required repetition rate of 257 kHz. The beam pulses have rise times of 120 ns and Full Width at Half Maximum (FWHM) of 240 ns to 370 ns. When the future high-current proton source of the FRANZ facility is available, the chopper will operate with a 50 mA, 120 keV beam. The design of the chopper and results of beam experiments are presented.

  2. Momentum and Energy Dependent Resolution Function of the ARCS Neutron Chopper Spectrometer at High Momentum Transfer: Comparing Simulation and Experimen

    CERN Document Server

    Diallo, S O; Abernathy, D L; Azuah, R T

    2016-01-01

    Inelastic neutron scattering at high momentum transfers (i.e. $Q\\ge20$ {\\AA}) or DINS provides direct observation of the momentum distribution of light atoms, making it a powerful probe for studying single-particle motions in liquids and solids. The quantitative analysis of DINS data requires an accurate knowledge of the instrument resolution function $R_{i}({Q},E)$ at each $Q$ and energy transfer $E$, where the label $i$ indicates whether the resolution was experimentally observed $i={obs}$ or simulated $i=sim$. Here, we describe two independent methods for determining the total resolution function $R_{i}({Q},E)$ of the ARCS neutron instrument at the Spallation Neutron Source, Oak Ridge National Laboratory. The first method uses experimental data from an archetypical system (liquid $^4$He) studied with DINS, which are then numerically deconvoluted using its previously determined intrinsic scattering function to yield $R_{obs}({Q},E)$. The second approach uses accurate Monte Carlo simulations of the ARCS spec...

  3. New chopper control at ILL

    Energy Technology Data Exchange (ETDEWEB)

    Descamps, F. [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France)

    1997-04-01

    Proper phasing is an essential characteristic of the chopper systems used at ILL. A wide variety of choppers and selectors differing in weight, speed and bearing types are controlled by a unique electronic card performing digital adaptative filtering. The chopper regulation system is described. (author).

  4. First results from PHAROS, the new chopper spectrometer at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, B.J.; Sandoval, J.P.; Lysaght, P.; Nutter, M.; Robinson, R.A.

    1993-06-01

    In this article we present the first experimental measurements obtained on PHAROS during the 1992 run cycle at LANSCE. These are data on the phasing of the choppers relative to the accelerator system along with the consequent neutronic resolution, data on the real-space position resolution of the main detectors, a white-beam nickel powder calibration, and our first inelastic scattering measurement made on TiH{sub 2} with an incident energy of 300 MeV. The characteristic features of the new chopper spectrometer PHAROS, designed for low-angle inelastic neutron scattering and neutron Brillouin scattering, are described elsewhere in these proceedings.

  5. First results from PHAROS, the new chopper spectrometer at LANSCE

    International Nuclear Information System (INIS)

    In this article we present the first experimental measurements obtained on PHAROS during the 1992 run cycle at LANSCE. These are data on the phasing of the choppers relative to the accelerator system along with the consequent neutronic resolution, data on the real-space position resolution of the main detectors, a white-beam nickel powder calibration, and our first inelastic scattering measurement made on TiH2 with an incident energy of 300 MeV. The characteristic features of the new chopper spectrometer PHAROS, designed for low-angle inelastic neutron scattering and neutron Brillouin scattering, are described elsewhere in these proceedings

  6. Feasibility demonstration of a new Fermi chopper with supermirror-coated slit package

    International Nuclear Information System (INIS)

    The efficiency of inelastic neutron scattering measurements using a chopper spectrometer can be markedly improved by utilizing multiple incident energies (Multi-Ei method). However, in conventional chopper systems, optimization of the experimental condition for all incident energies is absolutely impossible. We developed a new Fermi chopper with a supermirror-coated slit package in order to overcome the problem and experimentally demonstrated that the full optimization of the experimental condition for multiple incident energies is nearly achieved

  7. Quantitative structure refinement from the ARCS chopper spectrometer

    Science.gov (United States)

    Božin, E. S.; Juhás, P.; Zhou, W.; Stone, M. B.; Abernathy, D. L.; Huq, A.; Billinge, S. J. L.

    2010-11-01

    The new wide angular-range chopper spectrometer ARCS at the Spallation Neutron Source at Oak Ridge National Laboratory has been successfully used in white-beam mode, with no Fermi chopper, to obtain neutron powder diffraction based atomic pair distribution functions (PDFs). Obtained PDF patterns of Si, Ni, and Al2O3 were refined using the PDFfit method and the results compared to data collected at the NPDF diffractometer at Los Alamos National Laboratory. High quality resulting fits are presented, demonstrating that reliable powder diffraction data can be obtained from ARCS when operated in this configuration.

  8. Design and placement considerations for propeller-type t-zero choppers

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, R.A.

    1998-12-31

    The author discusses factors to do with placement and running speeds of propeller-type t-zero choppers, as implemented at ISIS (on chopper spectrometers) and at LANSCE (on a reflectometer, chopper spectrometer and small-angle scattering instrument). In all cases, the purpose is to block the burst of high-energy neutrons that emanates from the source when the proton beam strikes the target, and still be fully open when the thermal neutrons of interest pass through the space occupied by the t-zero chopper. In general, roughly 30 cm of high-strength high-Ni alloy (like nimonic or inconel) is placed in the beam, and for background purposes, it is desirable to place the chopper as far upstream as possible.

  9. Infrared Sensor with Liquid Crystal Chopper

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    An infrared sensor using the liquid crystal chopper is presented. The infrared sensor is designed to detect infrared rays with a pyroelectric element used as a liquid crystal chopper in such an infrared sensor or the like.

  10. Design, construction, and initial operation of the SNS MEBT chopper system

    International Nuclear Information System (INIS)

    The chopper system for the Spallation Neutron Source (SNS) provides a gap in the beans for clean extraction from the accumulator ring. It consists of a pre-chopper in the low-energy bean transport (LEBT) and a faster chopper in the medium-energy beam transport (MEBT). We report here on the final design, fabrication, installation, and first beans tests of the MEBT chopper. The traveling-wave deflector is a meander-line design that matches the propagation of the deflecting pulse with the velocity of the beam at 2.5 MeV, after the radio-frequency quadrupole (RFQ) acceleration stage. The pulses uses a series of fast-risetime MOSFET transistors to generate the deflecting pulses of +- 2.5 kV with rise and fall times of 10 ns. We describe the design and fabrication of the meander line and pulsers and report on the first operation during initial beam tests at SNS.

  11. HELIOS: A high intensity chopper spectrometer at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Mason, T.E. [Oak Ridge National Lab., TN (United States); Broholm, C. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Physics and Astronomy; Fultz, B. [California Inst. of Tech., Pasadena, CA (United States). Dept. of Materials Science] [and others

    1998-12-31

    A proposal to construct a high intensity chopper spectrometer at LANSCE as part of the SPSS upgrade project is discussed. HELIOS will be optimized for science requiring high sensitivity neutron spectroscopy. This includes studies of phonon density of states in small polycrystalline samples, magnetic excitations in quantum magnets and highly correlated electron systems, as well as parametric studies (as a function of pressure, temperature, or magnetic field) of S(Q,{omega}). By employing a compact design together with the use of supermirror guide in the incident flight path the neutron flux at HELIOS will be significantly higher than any other comparable instrument now operating.

  12. HELIOS: A high intensity chopper spectrometer at LANSCE

    International Nuclear Information System (INIS)

    A proposal to construct a high intensity chopper spectrometer at LANSCE as part of the SPSS upgrade project is discussed. HELIOS will be optimized for science requiring high sensitivity neutron spectroscopy. This includes studies of phonon density of states in small polycrystalline samples, magnetic excitations in quantum magnets and highly correlated electron systems, as well as parametric studies (as a function of pressure, temperature, or magnetic field) of S(Q,ω). By employing a compact design together with the use of supermirror guide in the incident flight path the neutron flux at HELIOS will be significantly higher than any other comparable instrument now operating

  13. Text experiments of disk chopper with supermirror converging system

    International Nuclear Information System (INIS)

    We measured transportation property of neutron pulsed by disk chopper with three kinds of setting of supermirror guide at JRR-3M, JAERI. We confirmed a gain of supermirror converging system to narrow straight supermirror system. The gain is approximately same as the ratio of entrance width of converging guide to width of narrow straight guide. On the other hand, we did not get a gain of supermirror converging system to wide straight supermirror system which has a same width to entrance width of converging guide and we will plan more precisely experiment. (author)

  14. A design study of VOR: a versatile optimal resolution chopper spectrometer for the ESS

    International Nuclear Information System (INIS)

    VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS), 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1 - 120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from ΔE/E = 1% up to ΔE/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1 - 3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM) and is therefore able to measure, in a single ESS period, 6 - 14 incident wavelengths, across a wavelength band of 9 Angstroms with a novel chopper configuration that transmits all incident wavelengths with equivalent counting statistics. The characteristics of VOR make it a unique instrument with capabilities to access small, limited-lifetime samples and transient phenomena with inelastic neutron scattering. (authors)

  15. A design study of VOR: A versatile optimal resolution chopper spectrometer for the ESS

    Science.gov (United States)

    Deen, P. P.; Vickery, A.; Andersen, K. H.; Hall-Wilton, R.

    2015-01-01

    VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS), 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1-120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from ΔE/E = 1% up to ΔE/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1-3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM) and is therefore able to measure, in a single ESS period, 6-14 incident wavelengths, across a wavelength band of 9 Å with a novel chopper configuration that transmits all incident wavelengths with equivalent counting statistics. The characteristics of VOR make it a unique instrument with capabilities to access small, limited-lifetime samples and transient phenomena with inelastic neutron scattering.

  16. A design study of VOR: A versatile optimal resolution chopper spectrometer for the ESS

    Directory of Open Access Journals (Sweden)

    Deen P.P.

    2015-01-01

    Full Text Available VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS, 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1–120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from ΔE/E = 1% up to ΔE/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, ΔE/E = 1–3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition rate multiplication (RRM and is therefore able to measure, in a single ESS period, 6–14 incident wavelengths, across a wavelength band of 9 Å with a novel chopper configuration that transmits all incident wavelengths with equivalent counting statistics. The characteristics of VOR make it a unique instrument with capabilities to access small, limited-lifetime samples and transient phenomena with inelastic neutron scattering.

  17. Chopper Circuits Developed for EV Drive Application

    Science.gov (United States)

    Tsuruta, Yukinori; Kawamura, Atsuo

    In this paper, the technical stream on a high efficiency and high frequency chopper for the automotive industry, new energy and energy conservation technology field is surveyed. QRAS (Quasi-resonant Regenerating Active Snubber) and SAZZ (Snubber Assisted Zero Voltage and Zero Current Transition) topologies aimed for the electric vehicle (EV) drive application are proposed. 25kHz-8kW QRAS, 100kHz-8kW SAZZ choppers and 50kHz-25kW bilateral SAZZ-1 chopper are constructed and tested under rating conditions. It is verified that SAZZ topology retains high efficiency even at the increased operating frequency of 100kHz. It is shown that high efficiency can be realized at high operating frequency even in high power converters by QRAS and newly proposed SAZZ soft switching topologies.

  18. Chopper:Efficient Algorithm for Tree Mining

    Institute of Scientific and Technical Information of China (English)

    Chen Wang; Ming-Sheng Hong; Wei Wang; Bai-Le Shi

    2004-01-01

    With the development of Internet, frequent pattern mining has been extended to more complex patterns like tree mining and graph mining. Such applications arise in complex domains like bioinformatics, web mining, etc. In this paper, we present a novel algorithm, named Chopper, to discover frequent subtrees from ordered labeled trees. An extensive performance study shows that the newly developed algorithm outperforms TreeMinerV, one of the fastest methods proposed previously, in mining large databases. At the end of this paper,the potential improvement of Chopper is mentioned.

  19. Development of a voltage scanner of chopper

    International Nuclear Information System (INIS)

    Development of voltage sweeper of chopper with CPNG are introduced. Voltage sweeper is one of important key parts of chopper. Two years working prove that it is stable and reliable. Its main technology performance save: sine wave frequency: 750 kHz +- 20 Hz; total distortion: 65 Db; output voltage (V-V): 0-≥4000 V; the error≤+-25 V; output power: >7 W; voltage supply: 220V AC +-10%, 50 +- 1 Hz; total power supply: <100W; Work temperature range: 0 - 40 degree; Stability in long time ≤1%

  20. Optical chopper for the HIRDLS instrument

    Science.gov (United States)

    Opyd, Walter G.; Loewenthal, Stuart

    2003-12-01

    Requirements, performance and life-test results are presented for the optical chopper installed in the High-Resolution Dynamics Limb Sounder (HIRDLS) to be flown on the AURA mission of the NASA Earth Observing System (EOS). Optical chopping is essential in order to achieve the required sensitivity and accuracy in measurement of infrared emission from various chemical species in the earth's atmosphere. Chopping of the optical input as far forward in the telescope as practical minimizes calibration errors arising from variations in emission from warm optics and due to electronic drifts in the infrared detecting system. At 500 Hz, a reflective chopper blade is used to alternate the instrument view between the atmospheric limb and cold space. The HIRDLS chopper is a six-toothed, mirrored wheel driven by a brushless DC motor. Chopper design was driven by requirements of 1) continuous operation at 5000 RPM for 50,000 hours in space vacuum, 2) chopping amplitude stability of one part in 100,000, 3) lubricant loss control for both bearing reliability and prevention of optics contamination, 4) compact size to fit in the folded telescope, and 5) survival in the launch environment.

  1. Negative coupled inductors for polyphase choppers

    Science.gov (United States)

    Jamieson, Robert S. (Inventor)

    1984-01-01

    A technique for negatively coupling the outputs of polyphase choppers is disclosed, wherein the output inductance of each phase is divided into two windings, and each winding is negatively coupled to a corresponding winding of a neighboring phase. In a preferred embodiment for a three-phase chopper circuit, the output inductance of phase A is divided into windings 100 and 102, the output inductance of phase B is divided into windings 110 and 112, and the output inductance of phase C is divided into windings 120 and 122. Pairs of windings 100 and 110, 112 and 120, and 102 and 122 are respectively disposed in transformers arranged for negatively coupling the windings of each pair.

  2. Modeling and control of parallel multicell chopper using Petri nets

    OpenAIRE

    Amghar, Bilal; Darcherif, Moumen; Barbot, Jean-Pierre; Gauthier, Patrick

    2012-01-01

    International audience In this paper a new class of converters power will be studied (Parallel Multicell Chopper). The topology of these chopper is based on a combination of n cells switching interconnected via independent inductors. This type of choppers is a new DC/DC static power converter which has an output current equals to n times the source current where n is the number of cells . After recalling the dynamical equations of the converter, its hybrid dynamical behavior and properties...

  3. Development of a fast traveling-wave beam chopper for the SNS project

    International Nuclear Information System (INIS)

    High current and stringent restrictions on beam losses, below 1 nA/m, in the designed linac for the Spallation Neutron Source (SNS) require clean and fast--with the rise time from 2% to 98% less than 2.5 ns--beam chopping in its front end, at the beam energy 2.5 MeV. The development of new traveling-wave deflecting current structures based on meander lines is discussed. Three-dimensional time-domain computer simulations with MAFIA are used to study transient effects in the chopper and to optimize current structure design. Two options for the fast pulsed voltage generator--based on FETs and vacuum tubes--are considered, and their advantages and shortcomings for the SNS chopper are discussed

  4. A design study of VOR: a versatile optimal resolution chopper spectrometer for the ESS

    CERN Document Server

    Deen, P P; Andersen, K H; Hall-Wilton, R

    2014-01-01

    VOR, the versatile optimal resolution chopper spectrometer, is designed to probe dynamic phenomena that are currently inaccessible for inelastic neutron scattering due to flux limitations. VOR is a short instrument by the standards of the European Spallation Source (ESS), 30.2 m moderator to sample, and provides instantaneous access to a broad dynamic range, 1 - 120 meV within each ESS period. The short instrument length combined with the long ESS pulse width enables a quadratic flux increase, even at longer wavelengths, by relaxing energy resolution from $\\Delta$E/E = 1% up to $\\Delta$E/E = 7%. This is impossible both on a long chopper spectrometer at the ESS and with instruments at short pulsed sources. In comparison to current day chopper spectrometers, VOR can offer an order of magnitude improvement in flux for equivalent energy resolutions, $\\Delta$E/E = 1-3%. Further relaxing the energy resolution enables VOR to gain an extra order of magnitude in flux. In addition, VOR has been optimised for repetition...

  5. Considerations about Chopper Configuration at a time-of-flight SANS Instrument at a Spallation Source

    CERN Document Server

    Jaksch, Sebastian

    2016-01-01

    In any neutron scattering experiment the measurement of the position of the scattered neutrons and their respective velocities is necessary. In order to do so, a position sensitive detector as well as a way to determine the velocities is needed. Measuring the velocities can either be done by using only a single wavelength and therefore velocity or by creating pulses, where the start and end time of each pulse is known and registering the time of arrival at the detector, which is the case we want to consider here. This pulse shaping process in neutron scattering instruments is usually done by using a configuration of several choppers. This set of choppers is then used to define both the beginning and the end of the pulse. Additionally there is of course also a selection in phase space determining the final resolution that can be achieved by the instrument. Taking into account the special requirements of a specific instrument, here a small-angle neutron scattering instrument, creates an additional set of restri...

  6. Linac4 chopper line commissioning strategy

    CERN Document Server

    Bellodi, G; Lombardi, A M; Posocco, P A; Sargsyan, E

    2010-01-01

    The report outlines the strategy for beam-based commissioning of the Linac4 3 MeV chopper line as currently scheduled to start in the second half of 2011 in the Test Stand Area. A dedicated temporary diagnostics test bench will complement the measurement devices foreseen for permanent installation in the chopper line. A commissioning procedure is set out as a series of consecutive phases, each one supposed to meet a well- defined milestone in the path to fully characterise the beam-line. Specific set-ups for each stage are defined in terms of beam characteristics, machine settings and diagnostics used. Operational guidelines are given and expected results at the relative points of measurements are shown for simulated scenarios (on the basis of multi-particle tracking studies carried out with the codes PATH and TRACEWin). These are then interpreted in the light of the resolution limits of the available diagnostics instruments to assess the precision reach on individual measurements and the feasibility of techn...

  7. Analysis of Input and Output Ripples of PWM AC Choppers

    Directory of Open Access Journals (Sweden)

    Pekik Argo Dahono

    2008-11-01

    Full Text Available This paper presents an analysis of input and output ripples of PWM AC choppers. Expressions of input and output current and voltage ripples of single-phase PWM AC choppers are first derived. The derived expressions are then extended to three-phase PWM AC choppers. As input current and output voltage ripples specification alone cannot be used to determine the unique values of inductance and capacitance of the LC filters, an additional criterion based on the minimum reactive power is proposed. Experimental results are included in this paper to show the validity of the proposed analysis method.

  8. A new high-speed X-ray beam chopper

    International Nuclear Information System (INIS)

    A new high-speed x-ray beam chopper using laser scanner technology has been developed and tested on the SRI-CAT sector 1 beamline at the Advanced Photon Source (APS) storage ring (1). As illustrated in figure 1, it is compact in size and has two sets of transmission windows: BK-7 glass for visible light transmission and 0.23-mm-thick Be for the transmission of x-rays. The rotor is made of aluminum and has a diameter of 50.8 mm. A 0.5-mm-wide and 2.29-mm-tall slit is cut through the center of the rotor. The circumference of the rotor has a coating of 1-mm-thick Ni, which gives an attenuation of 108 at 30 keV. Turning at nearly 80000 RPM, this beam chopper has an opening time window of 2450 ns, corresponding to 67% of the revolution time of the APS storage ring. The primary feature in selecting laser scanner technology to develop into an x-ray beam chopper was the high level of rotational speed control of the rotor that makes up the beam chopper element (2). By using an optical feedback circuit to sample the rotational speed four times each revolution, the jitter in the position of the transmission open time window is only 3 ns at the 3 standard deviation level. The APS storage ring orbital frequency, supplied by the control room, is divided down to provide the appropriate drive frequency for the beam chopper motor controller. By this means, both the storage ring and the beam chopper are operating off the same master clock. After a turn-on time of about 15 to 20 seconds, the rotational precision of the motor results in immediate phase locking to the temporal structure of the APS storage ring. By inserting a Stanford delay generator between the frequency divider and the beam chopper motor controller, the phase between the storage ring temporal structure and the beam chopper rotation can be adjusted to position the transmission time window of the beam chopper on any desired part of the storage ring fill pattern. If an asymmetric fill pattern is used in the APS storage

  9. Study on Rotor IGBT Chopper Control for Induction Motor Drive

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Rotor chopper control is a simple and effective drive method for induction motor. This paper presents a novel IGBT chopper topology,which can both adjust rotor resistance and protect IGBT efficiently. Investigation on the quasi-transient state of the rotor rectifying circuit is made, and a nonlinear mapping between the equivalent resistance and the duty cycle is deduced. Furthermore, the method for determining the magnitude of the external resistor is introduced.

  10. Neural network based PWM AC chopper fed induction motor drive

    Directory of Open Access Journals (Sweden)

    Venkatesan Jamuna

    2009-01-01

    Full Text Available In this paper, a new Simulink model for a neural network controlled PWM AC chopper fed single phase induction motor is proposed. Closed loop speed control is achieved using a neural network controller. To maintain a constant fluid flow with a variation in pressure head, drives like fan and pump are operated with closed loop speed control. The need to improve the quality and reliability of the drive circuit has increased because of the growing demand for improving the performance of motor drives. With the increased availability of MOSFET's and IGBT's, PWM converters can be used efficiently in low and medium power applications. From the simulation studies, it is seen that the PWM AC chopper has a better harmonic spectrum and lesser copper loss than the Phase controlled AC chopper. It is observed that the drive system with the proposed model produces better dynamic performance, reduced overshoot and fast transient response. .

  11. A prototype chopper for synchrotron time-resolved crystallographic measurements

    International Nuclear Information System (INIS)

    A mechanical x-ray chopper has been designed to perform microsecond time-resolved crystallographic studies at the DIAMOND synchrotron I19 beamline. It consists of two asymmetric absorbers rotating synchronously at frequencies from 0 to 50 Hz in the same direction around a rotation axis that is parallel to the x-ray beam. The duration of the x-ray pulses produced by the chopper is determined by the relative phase between the two blades, which can be adjusted. The chopper system presented in this paper offers a time resolution suitable for conducting in situ experiments that afford the crystal structure of materials while in their transient (>10 μs) photoactivated excited states.

  12. ARCS A wide-Anglular Range Chopper Spectrometer at the SNS

    Energy Technology Data Exchange (ETDEWEB)

    Prof. Brent Fultz; Dr. Doug Abernathy

    2005-01-03

    The ARCS spectrometer project has been funded for 39 months. Procurements are now amain activity, although engineering effort remains, and installation has begun. Most of the subsystems are under control, and represent no risk to the project. These are: cryo-goniometer, detectors and electronics, Fermi chopper system, computing cluster, basic reduction software, T0 chopper and main neutron guide. The sample hutch and radiationshielding are still items of some risk. At the time of this writing, we are awaiting vendor proposals for the scattering chamber with integrated sample isolation system. This is thelargest uncertainty in the ARCS project today. The ARCS Chief Engineer, Kevin Shaw, joined the project in 2004. Project controlsservices are now performed by the SNS. A construction progress review was held in the August, 2004, before which the project was rebaselined, and after which the ProjectExecution Plan was updated. The ARCS project will be rebaselined in March 2005 after a vendor is selected for the scattering chamber with integrated isolation system. Projectcompletion by Sept. 2006 is possible but challenging.

  13. Design of an SFQ Microwave Chopper for Controlling Quantum Bits

    OpenAIRE

    Matsuda, G; Yamanashi, Y; Yoshikawa, N.

    2007-01-01

    A microwave chopper using single-flux-quantum (SFQ) circuits is proposed for the control of quantum bits (qubits). The proposed microwave chopper is composed of a DC/SFQ converter, an SFQ switch and a band-pass filter (BPF). In operation, an externally applied microwave is input to a DC/SFQ converter to generate an SFQ pulse train, which is chopped at high speed by the SFQ switch. The SFQ pulse train is then filtered by the BPYA I to remove higher harmonics. The transient response, the amplit...

  14. First flux measurement in a SINQ supermirror neutron guide

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S.; Schlumpf, N.; Bauer, G. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1997-09-01

    On Dec. 3, 1996, the Swiss spallation neutron source SINQ was taken into operation and produced its first neutrons successfully. The neutron spectrum within one of the supermirror guides was estimated by a chopper Time-of-Flight method. The result shows a 30% higher neutron intensity at the flux maximum than expected from previous Monte-Carlo simulations. (author) 1 fig., 4 refs.

  15. Fiber optic yield monitor for a sugarcane chopper harvester

    Science.gov (United States)

    A fiber optic yield monitoring system was developed for a sugarcane chopper harvester that utilizes a duty-cycle type approach with three fiber optic sensors mounted in the elevator floor to estimate cane yield. Field testing of the monitor demonstrated that there was a linear relationship between t...

  16. Thermal chopper spectrometer for the European spallation source

    DEFF Research Database (Denmark)

    Klenø, Kaspar Hewitt; Lefmann, Kim

    2011-01-01

    One of the instruments being considered for the ESS is a thermal chopper spectrometer, intended for the study of lattice vibrations and magnetic excitations. However, as the ESS will be a long pulsed source, we propose a very long instrument (180–300 m). We here present a guide system that can...

  17. A CMOS low-noise instrumentation amplifier using chopper modulation

    DEFF Research Database (Denmark)

    Nielsen, Jannik Hammel; Bruun, Erik

    2005-01-01

    This paper describes a low-power, low-noise chopper stabilized CMOS instrumentation amplifier for biomedical applications. Low thermal noise is achieved by employing MOSTs biased in the weak/moderate inversion region, whereas chopper stabilization is utilized to shift 1/f-noise out of the signal...... band hereby ensuring overall low noise performance. The resulting equivalent input referred noise is approximately 7 nV/rootHz for a chopping frequency of 20 kHz. The amplifier operates from a modest supply voltage of 1.8 V, drawing 136 muA of current thus consuming 245 muW of power. The gain is 72.5 d...

  18. New chopper modulators using differential voltage current conveyor

    OpenAIRE

    Kumngern, M.

    2011-01-01

    This paper presents new chopper modulators which can enable to assign three modulators in one circuit. Full amplitude modulators as Cowan and Ring modulators are kinds of the amplitude modulators as well. The proposed circuit is implemented from the differential voltage current conveyor, four-MOS transistors switch and two-MOS transistors inverter. The advantage of this proposed circuit is high input and low output impedance and is able to be connected with any load without buffer and the num...

  19. Travelling wave chopper for the high current injector at IUAC

    International Nuclear Information System (INIS)

    IUAC is developing High Current Injector (HCI) accelerator as an alternative injector for the existing superconducting linear accelerator. The HCI project was envisaged to overcome the low current limitation of the Pelletron Accelerator and to provide varieties of ion species like nobel gases etc. which are not possible with existing Pelletron Accelerator. The LEBT (low energy beam transport) section of HCI consists of various beam dynamics components like GP Tubes, Diagnostic Box, Chopper and TWD, Multi Harmonic Buncher (MHB), Vacuum System, Magnetic Quadruple, and Fast Faraday Cup etc. A Chopper and Travelling Wave Deflector (TWD) is required to provide the chopped beam with various repetition rate to IUAC experimental facilities ego NAND, HYRA, HlRA, INGA etc. The proposed MHB in the LEBT section of HCI, is having 60 ns linear portion in its saw tooth wave form. The requirement of the repetition rate for the experimental facilities are 250ns, 500ns, 1μs, 2μs, 4μs and 8μs. It was decided that output of chopper must have 60 ns pulse length with maximum current and TWD must provide the various repetition rate as mentioned above. In this paper we will present the details of the design and fabrication of prototype

  20. Chopper mode analysis of beam distribution based on time in HIRFL

    International Nuclear Information System (INIS)

    Chopper is an important equipment in beam distribution system based on time of heavy ion research facility in Lanzhou (HIRFL). This paper introduces its mode analysis system's architecture and hardware composition, analyzes corresponding software requirements, and designs the mode analysis program using multithreading technology. Firstly the program reads mode pulse data of chopper from data acquisition card by NI-DAQmx function, then uses the data for further analysis, and finally sends corresponding work mode control instruction to chopper controller through TCP/IP protocol. The designed program meets system requirements, realizing the function of chopper mode automatic conversion, and has passed the field test. (authors)

  1. Reflective Optical Chopper Used in NIST High-Power Laser Measurements

    Directory of Open Access Journals (Sweden)

    Cromer, Chris

    2008-11-01

    Full Text Available For the past ten years, NIST has used high-reflectivity, optical choppers as beamsplitters and attenuators when calibrating the absolute responsivity and response linearity of detectors used with high-power CW lasers. The chopper-based technique has several advantages over the use of wedge-shaped transparent materials (usually crystals often used as beam splitters in this type of measurement system. We describe the design, operation and calibration of these choppers. A comparison between choppers and transparent wedge beampslitters is also discussed.

  2. Feasibility study into the use of mechanical choppers to alter the natural time structure of the APS

    International Nuclear Information System (INIS)

    The prospect of extending static x-ray measurements into the time domain is an exciting one indeed. The foundations for this extension have already been laid by some very innovative experiments performed at existing storage ring sources. The enormous enhancement in brilliance that the APS will afford over existing sources will, I believe, foster a tremendous growth in the area of time-resolved x-ray experimentation. The growing interest in this field is evidenced by both the number of participants and their enthusiasm at an APS Workshop on Time-Resolved Studies and Ultrafast Detectors held on January 25-26, 1988, at Argonne. We present here what may be a viable approach to the problem of altering the natural time structure of the APS with a minimal impact on other users. Our technique involves placing 19 of the 20 circulating bunches of positrons in (nearly) contiguous RF buckets and the remaining one bunch 180 degrees around the ring from this pack. The method we are advocating has several advantages over other schemes (such as wobblers) in that it is a passive technique: there are no external forces on the particle beam to destroy its stability, emittance, or lifetime properties, and it will not limit the total number of bunches in the beam to one (or a few) in order to get long dark periods between x-ray bursts. In this configuaration is should be possible to transmit the lone bunch and mechanically shutter the remaining 19 bunches with a chopper running at approximately 18,000 RPM. Although high, such revolution frequencies are achieved in neutron choppers which are generally much more massive than what is envisioned for an x-ray chopper

  3. Development of fast beam-stop system using RF chopper

    International Nuclear Information System (INIS)

    To avoid heat damage and radioactivation by beam loss of the J-PARC accelerator, Machine Protection System (MPS) has been developed. Actually, high responsibility and high reliability have been achieved in J-PARC. Beam-stop method in addition to a way of RFQ OFF has been requested in order to avoid damage to the RFQ. Therefore, we have been developing a fast beam-stop system by using a RF chopper. The fast beam-stop system, including beam test, is described in this paper. (author)

  4. Tuning of MEBT-Chopper by using wire scanner monitor

    International Nuclear Information System (INIS)

    In J-PARC, a macro pulse with several hundred micro seconds is shaped into a pulse with medium bunch structure of about one MHz, by a RF chopper at MEBT section. The comb-like structured pulse is injected into the following DTL section. The remaining fraction of the beam in the bottom of the comb-like structure, is measured by a wire scanner monitor (with preamplifier) located in the downstream. The remaining fraction (compared to the nominal signal) is of the order of 0.1%. (author)

  5. Ultra-high vacuum compatible optical chopper system for synchrotron x-ray scanning tunneling microscopy

    International Nuclear Information System (INIS)

    High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM

  6. Ultra-high vacuum compatible optical chopper system for synchrotron x-ray scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Hao, E-mail: hc000211@ohio.edu [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701 (United States); Cummings, Marvin; Shirato, Nozomi; Stripe, Benjamin; Preissner, Curt; Freeland, John W. [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Rosenmann, Daniel [Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Kersell, Heath; Hla, Saw-Wai [Nanoscale and Quantum Phenomena Institute, Physics & Astronomy Department, Ohio University, Athens, Ohio 45701 (United States); Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Rose, Volker, E-mail: vrose@anl.gov [Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439 (United States)

    2016-01-28

    High-speed beam choppers are a crucial part of time-resolved x-ray studies as well as a necessary component to enable elemental contrast in synchrotron x-ray scanning tunneling microscopy (SX-STM). However, many chopper systems are not capable of operation in vacuum, which restricts their application to x-ray studies with high photon energies, where air absorption does not present a significant problem. To overcome this limitation, we present a fully ultra-high vacuum (UHV) compatible chopper system capable of operating at variable chopping frequencies up to 4 kHz. The lightweight aluminum chopper disk is coated with Ti and Au films to provide the required beam attenuation for soft and hard x-rays with photon energies up to about 12 keV. The chopper is used for lock-in detection of x-ray enhanced signals in SX-STM.

  7. Enhanced Performance Neutron Scattering Spectroscopy by Use of Correlation Techniques

    CERN Document Server

    Mezei, F; Migliardo, F; Magazù, S

    2016-01-01

    Neutron correlation spectroscopy can exceed direct spectroscopy in the incoming beam intensity by up to two orders of magnitude at the same energy resolution. However, the propagation of the counting noise in the correlation algorithm of data reduction is disadvantageous for the lowest intensity parts of the observed spectrum. To mitigate this effect at pulsed neutron sources we propose two dimensional time-of-flight recording of each neutron detection event: with respect to both the neutron source pulses and to the rotation phase of the pseudo-random beam modulation statistical chopper. We have identified a formulation of the data reduction algorithm by matching the data processing time channel width to the inherent time resolution of this chopper, which makes the reconstruction of the direct time-of-flight spectra exact and independent of all other contributions to instrumental resolution. Two ways are proposed for most flexible choice of intensity vs. resolution without changing the statistical chopper or ...

  8. Status of CERN Chopper Driver and the Solid State Alternative

    CERN Document Server

    Paoluzzi, M

    2005-01-01

    The Superconducting H- Linac under study at CERN requires a high performance 3 MeV chopper. It has to establish the required beam time-structure by dumping part of the beam exiting the RFQ in 0.6 ms bursts of 1 ns bunches spaced by 2.84 ns and repeated at 50 Hz. For maximum flexibility, the system must be able to remove any number of consecutive bunches with a minimum of 3 and up to a few thousand. The amplifier driving the chopper structure has thus to provide 500 V on 50 omega, with rise and fall times below 2 ns and repetition rate as high as 45 MHz. To achieve the very wide frequency response required for this application a first proposal based on the idea of generating the low and high frequency part of the required spectrum with distinct amplifiers has been followed. In-depth studies and prototyping have proven the principle but also shown its fragilities. Distortions, saturation effects in the ferrite or in the driving circuits, vacuum tube ageing, etc. are difficult to keep within the limits required ...

  9. Optimization of ''reverse time of flight'' neutron scattering devices

    International Nuclear Information System (INIS)

    The ''reverse time of flight'' (RTOF) elastic neutron scattering technique for powdered samples is briefly described. The advantages and some problems of this high resolution technique are discussed. The main task is to illustrate opportunities and solutions for an optimization of a RTOF instrument, especially for the neutron chopper device and the detector system. (orig.)

  10. A fast chopper for programmed population of the longitudinal phase space of the AGS booster

    International Nuclear Information System (INIS)

    This paper reports on a fast chopper which has been built, that can switch the beam injected into the AGS or AGS Booster on and off with rise and fall times in the order of 10 ns. The chopper will be used to control the initial population of longitudinal phase space in order to eliminate rf capture losses and achieve an optimal phase space density distribution. The chopper operates on the 35 keV H- beam between the ion source and the RFQ. The interaction between the electrostatic fields of the chipper and the space charge neutralizing ions in the beam has been seen to be a significant but manageable effect

  11. SMALL-SIGNAL ANALYZING OF SEPARATELY EXCITED DC MOTOR FED DC - DC CHOPPER

    OpenAIRE

    İSMAİL COŞKUN

    1999-01-01

    Choppers are widely used in order to get smooth speed characteristics of DC motors. If the load or input voltage is changed, a feedback control technique is used to get the constant speed. To design the proper feedback control, the transfer function of the chopper-motor combination should be kno\\vn. ln this study, the effort was given to obtain the general black diagram, inciurling the field current and aı1na ture current of chopper-fed DC motor. It can be seen from the black diagram that the...

  12. New chopper modulators using differential voltage current conveyor

    Directory of Open Access Journals (Sweden)

    M. Kumngern

    2011-06-01

    Full Text Available This paper presents new chopper modulators which can enable to assign three modulators in one circuit. Full amplitude modulators as Cowan and Ring modulators are kinds of the amplitude modulators as well. The proposed circuit is implemented from the differential voltage current conveyor, four-MOS transistors switch and two-MOS transistors inverter. The advantage of this proposed circuit is high input and low output impedance and is able to be connected with any load without buffer and the number of transistors is quite less which is suitable for integrated circuits. The technique is to control the switch by using the square pulse which is obtained from a direct signal generator. All simulation results are based on the PSPICE program simulator which confirms the performance of the proposed circuit and technique.

  13. A fast chopper of TOF-LEIS experiments

    International Nuclear Information System (INIS)

    Full text: Time-Of-Flight Low Energy Ion Scattering (TOF-LEIS) is a very powerful technique for surface analysis. Recently, a new TOF-LEIS experiment (ACOLISSA) has been set to operation and measurements have been performed at the institute of experimental physics, department of atomic physics and surface science. Within this contribution we present a new, fast electrostatic chopper which has been designed and constructed for this experiment. As examples total intensity TOF-LEIS spectra from He-ions and Cu in the keV energy range are presented with a minimal time resolution of about 5-10 ns corresponding to a depth resolution in the total intensity TOF-LEIS spectra of less than 1 monolayer. (author)

  14. Analysis of Variable Speed PFC Chopper Fed BLDC Motor Drive

    Directory of Open Access Journals (Sweden)

    A Jeya Selvan Renius

    2015-02-01

    Full Text Available This paper provides the detailed analysis of the DC-DC chopper fed Brushless DC motor drive used for low-power applications. The various methods used to improve the power quality at the ac mains with lesser number of components are discussed. The most effective method of power quality improvement is also simulated using MATLAB Simulink. Improved method of speed control by controlling the dc link voltage of Voltage Source Inverter is also discussed with reduced switching losses. The continuous and discontinuous modes of operation of the converters are also discussed based on the improvement in power quality. The performance of the most effective solution is simulated in MATLAB Simulink environment and the obtained results are presented.

  15. The resolution function for a time-of-flight diffractometer with curved slits chopper

    Energy Technology Data Exchange (ETDEWEB)

    Ionita, I. [Institute for Nuclear Research, Pitesti (Romania); Stoica, A.D. [Institute for Physics and Technology for Materials (Romania)

    1996-07-01

    The procedure for computing the resolution function for a time-of-flight diffractometer with curved slits chopper is presented. Some focusing conditions concerning the sample and detector inclination angle are also given. (orig.)

  16. The Effect of the Chopper on Granules from Wet High-Shear Granulation Using a PMA-1 Granulator

    OpenAIRE

    Briens, Lauren; Logan, Ryan

    2011-01-01

    Chopper presence and then chopper speed was varied during wet high shear granulation of a placebo formulation using a PMA-1 granulator while also varying the impeller speed. The granules were extensively analyzed for differences due to the chopper. The effect of the chopper on the granules varied with impeller speed from no effect at a low impeller speed of 300 rpm to flow interruptions at an impeller speed of 700 rpm to minimal impact at very high impeller speeds as caking at the bowl perime...

  17. Java-based software for chopper-spectrometer data reduction

    International Nuclear Information System (INIS)

    We introduce a software application for analyzing time-of-flight data obtained from a chopper spectrometer. This Chop Analysis Package (CAP) is written in Java to take advantage of its platform independence and Internet accessibility. CAP is a component within the architecture of the Integrated Spectral Analysis Workbench (ISAW) being developed at Argonne. Multiple large data sets, each containing ∼1000 spectra, can be examined for removal of noise and contamination. Appropriate sample, background and calibration runs are combined and normalized. Afterward, data from detector groups are binned and converted into various scattering functions in momentum- and energy-transfer (|Q|, E) space. The resulting datasets can be analyzed further by users with additional methods. By virtue of the object-oriented programming (OOP) methods and graphic user interface (GUI) of ISAW, immediate steps of the evaluation are easily displayed in interactive viewers as images or line plots. Repetitive procedures can be executed through command-line scripts. The results can be saved as formatted tables in text files or pasted into other applications. (author)

  18. Extracting source parameters from beam monitors on a chopper spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Abernathy, Douglas L [ORNL; Niedziela, Jennifer L [ORNL; Stone, Matthew B [ORNL

    2015-01-01

    The intensity distributions of beam monitors in direct-geometry time-of-flight neutron spectrometers provide important information about the instrument resolution. For short-pulse spallation neutron sources in particular, the asymmetry of the source pulse may be extracted and compared to Monte Carlo source simulations. An explicit formula using a Gaussian-convolved Ikeda-Carpenter distribution is given and compared to data from the ARCS instrument at the Spallation Neutron Source.

  19. Larger research programs at the beam holes of the Austrian TRIGA Mark II reactor. Design and construction of a Fourier chopper-selector at the Austrian TRIGA reactor

    International Nuclear Information System (INIS)

    A neutron chopping system utilizing Fourier analysis has great advantages to alternative systems. For this purpose the chopper consists of a disc, opaque to neutrons, rotating on an axis perpendicular to its centre. Around its outside edge a series of uniformly spaced teeth and spaces are formed with neutron transparent gaps extending towards the centre. By using a stationary section having the same pattern of teeth and gaps it is possible to utilize a beam area considerably larger than the area of one tooth. During the last years at the TRIGA Reactor in Vienna a neutron chopping-and selecting-system is developed and in construction, which will not only chop the beam in that way necessary for Fourier analysis but also select the energy. The selection is done by seven discs of the form described above mounted on an axis. The selector is designed for neutron wave lengths between 3 and 30 A. The resolution is constant over the whole range of energy and depends on the beam divergence. Thus the modulation frequency is 104 sec-1 and the half-width of the neutron pulse about 50 μsec

  20. FOCUS: neutron time-of-flight spectrometer at SINQ: recent progress

    Energy Technology Data Exchange (ETDEWEB)

    Janssen, S.; Mesot, J.; Holitzner, L. [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Hempelmann, R. [Saarbruecken Univ. (Germany)

    1997-09-01

    At the Swiss neutron spallation source SINQ a time-of-flight spectrometer for cold neutrons is under construction. The design foresees a Hybrid solution combining a Fermi chopper with a doubly focusing crystal monochromator. During 1996 important progress has been made concerning the main spectrometer components such as the spectrometer housing and the detector system. (author) 2 figs., 3 refs.

  1. Correcting beam monitor and diffraction data for chopped delayed neutron backgrounds

    International Nuclear Information System (INIS)

    Delayed neutron choppers in pulsed source neutron beams serve to reduce the background caused by delayed neutrons in pulsed source instruments. The authors analyze the effect of a drum chopper placed in an incident pulsed beam which contains delayed neutrons and compute its influence on the detector counting rate. Expressions are found for the time and wavelength dependence of the counting rates for both prompt and delayed neutrons, in both monitor and scattered neutron detectors. On the basis of these results, they suggest an exact, random-phasing method for determining the delayed neutron background for use in measuring the delayed neutron counting rate, and propose a rapidly convergent iterative scheme for computing the correction from normally measured data. They report measurements which confirm the analysis. 5 refs., 7 figs

  2. SMALL-SIGNAL ANALYZING OF SEPARATELY EXCITED DC MOTOR FED DC - DC CHOPPER

    OpenAIRE

    İsmail COŞKUN

    1999-01-01

    Choppers are widely used in order to get smooth speed characteristics of DC motors. If the  load or input voltage is changed, a feedback control technique is used to get the constant speed. To design the proper feedback control, the transfer function of the chopper-motor combination should be kno\\vn. ln this study, the effort was given to obtain the general black diagram, inciurling the field current and aı1na ture current of chopper-fed DC motor. It can be seen from the black diagram that th...

  3. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    International Nuclear Information System (INIS)

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper

  4. Risk Assessment of the Chopper Dipole Kicker Magnets for the MedAustron Facility

    CERN Document Server

    Kramer, T; Barnes, M J; Benedikt, M; Fowler, T

    2011-01-01

    The MedAustron facility, to be built in Wiener Neustadt (Austria), will provide protons and ions for both cancer therapy and research [1]. Different types of kicker magnets will be used in the accelerator complex, including fast beam chopper dipoles: these allow the beam to be switched on and off for routine operational reasons or in case of emergency. Main requirements for the beam chopper system are safety and reliability. A criticality analysis, to chart the probability of failure modes against the severity of their consequences of the fault, has been carried out for the chopper dipole system. This "Failure Mode, Effects, and Criticality Analysis" (FMECA), has been used to highlight failure modes with relatively high probability and severity of consequences: conservative ratings of critical components and appropriate redundancy, together with measurements and interlocks, have been used to reduce the probability and criticality of faults. This paper gives an overview of the Risk Assessment approach and pres...

  5. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Müller, O., E-mail: o.mueller@uni-wuppertal.de; Lützenkirchen-Hecht, D.; Frahm, R. [Bergische Universität Wuppertal, Gaußstraße 20, Wuppertal 42119 (Germany)

    2015-03-15

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  6. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Science.gov (United States)

    Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.

    2015-03-01

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  7. Buck-Boost Control of Four Quadrant Chopper using Symmetrical Impedance Network for Adjustable Speed Drive

    OpenAIRE

    Saswati Swapna Dash; Byamakesh Nayak

    2015-01-01

    This paper proposes buck-boost capabilities of four quadrant chopper for wide range speed control of DC motor drives using symmetrical impedance network called Z-source network. By controlling the shoot through duty ratio from 0 to 0.5 and non-shoot through techniques, the Z-source four quadrant choppers can produce any desired DC voltage across the DC motor. The switching patterns for both buck and boost operations are presented to achieve four modes of operation of DC motor. As a result, th...

  8. Development of TMS320F2810 DSP Based Bidirectional buck-boost Chopper

    OpenAIRE

    Mr. K.S. Chakradhar*1,; M.Ayesha siddiqa2; T.Vandhana3

    2014-01-01

    A DC - DC converter is an electronic circuit which converts a source of direct current (DC) from one voltage level to another. It is a class of power converter. One common application of DC - DC converters is DC motor control. The Buck - Boost Chopper is a type of DC - DC converter. They are static devices which are used to obtain variable DC voltage from the source of constant DC voltage. Besides the saving in power, Buck-Boost choppers offer greater efficiency, faster respon...

  9. Feasibility of a fast beam chopper using laser stripping of H- ions for the JHP

    International Nuclear Information System (INIS)

    The feasibility of a fast beam chopper of the photodetachment neutralizer type by means of a pulsed Nd laser was studied in order to realize a decrease in the beam losses after injection into a circular accelerator for the JHP (Japanese Hadron Project). A 54-kW peak-power laser of 400 μs in length and a fast external amplitude modulator are required in order to produce 130-ns H0 pulses from H- pulses in the beam line between the ion source and the RFQ. Several possible installation points for the chopper are discussed. (author)

  10. Design and characteristics of a high-precision chopper wheel motor driver

    International Nuclear Information System (INIS)

    The circuit diagram and design principles of a high-stability chopper wheel motor driver are presented. Experimental results show that this unit can be interfaced to molecular-beam machines to generate supersonic beams with extremely stable root-mean-square and peak velocities fluctuating on a day-to-day basis by less than 0.2%

  11. Upgrade of power supply system for RF-chopper at J-PARC linac

    International Nuclear Information System (INIS)

    In the J-PARC Linac, the radio frequency deflector was adopted as a chopper to capture the particles into the RF-bucket in the next synchrotron. The chopper, consists of two deflectors, was installed on the medium-energy beam-transport line. In the operation of the RF-chopper, the fast rise/fall time of the pulse is a fundamental requirement to minimize the beam loss. In the previous system, the two series coupled chopper deflectors were driven by one solid-state amplifier due to the cost. However, the fell time indicated a poor result to effect the ringing into each cavity. Therefore, the additional solid-state amplifier and low level RF system were installed in the summer 2012 and the connection changed to the parallel system from the series using two amplifiers. The rise/fall time of the chopped beam was about 20 nsec in the beam current of 15 mA and the effect of the ringing was decreased. (author)

  12. Construction of polarized inelastic neutron spectrometer in J-PARC

    International Nuclear Information System (INIS)

    The instrumental design of the Polarization Analysis Neutron Spectrometer with Correlation Method (POLANO) is almost ready for its construction, although some discussion on the design still remains. POLANO is a new inelastic neutron spectrometer in the Japan Proton Accelerator Research Complex (J-PARC) utilizing polarized neutrons for comprehensive materials research, focusing on the use of quasi-elastic and inelastic scattering techniques. For instrumental construction, the basic shield design is complete and the shielding capability against radiation has been assessed. Additionally, the designs of the beam transport section using 4 Qc supermirror guide tube are almost complete. Also, detecting section and a large vacuum chamber is now under designing. The development of polarization and chopper devices are the key to the success for the very first application of polarization analysis to inelastic scattering at spallation neutron source. High performance Fermi and T0 choppers are now under manufacturing.

  13. Quasielastic neutron scattering study on polymer nanocomposites

    International Nuclear Information System (INIS)

    By using a quasielastic neutron scattering technique (disk-chopper-type spectrometer AMATERAS at J-PARC), we have investigated the microscopic dynamics of polybutadiene (PB) in which silica particles were embedded. The experimental results gave us both a damped vibration mode of PB and jumped diffusion motion of the segments. It was found that these dynamical features remain unaffected by the presence of the silica particle, while the residence time of the jumped diffusion motion becomes longer at the high filler loading.

  14. A mechanical chopper with continuously adjustable duty cycle for a wide X-ray beam

    International Nuclear Information System (INIS)

    The prototype of a fast beam chopper for hard X-rays, with a continuously variable duty cycle from less than 10 to more than 90% has been successfully developed, built and tested. The apparatus consists in 12 planetary stainless-steel blades that are 100 mm wide and are mounted on two large discs. All blades are kept permanently parallel to each other, thanks to a gear system, which also allows changing their orientation. The two main parameters of the chopper (duty cycle and chopping frequency) are controlled independently and remotely. In the present design, the device allows chopping frequencies ranging from 0 to 300 Hz. The principle of operation, preliminary results of the instrument's performance and an example demonstrating the capacity of the system for image quality improvement and X-ray dose reduction at the specimen are presented

  15. Design of RF chopper system for improving beam quality in FEL injector with thermionic gun

    International Nuclear Information System (INIS)

    For a linac-based Free Electron Laser (FEL), good beam quality largely contributes to the success of the final radiation. An imperfection confronted with the HUST THz-FEL facility is the long beam tail that emerges in the electron gun and exists through the whole beam line. This paper proposes to deploy a chopper system after the electron gun to truncate the beam tails before they enter into the linac. Physical dimensions of the chopper cavity are discussed in detail and we have developed and derived new analytical expressions applying to all frequencies for the optimal design. Also, technical issues of the cavity are considered. Beam dynamic simulation is performed to examine the truncation effect and the results show that more than 78% of the beam tail can be removed effectively, while preserving the emittance and energy spread in acceptable level

  16. Buck-Boost Control of Four Quadrant Chopper using Symmetrical Impedance Network for Adjustable Speed Drive

    Directory of Open Access Journals (Sweden)

    Saswati Swapna Dash

    2015-02-01

    Full Text Available This paper proposes buck-boost capabilities of four quadrant chopper for wide range speed control of DC motor drives using symmetrical impedance network called Z-source network. By controlling the shoot through duty ratio from 0 to 0.5 and non-shoot through techniques, the Z-source four quadrant choppers can produce any desired DC voltage across the DC motor. The switching patterns for both buck and boost operations are presented to achieve four modes of operation of DC motor. As a result, the proposed model will have ride through capability during voltage sags, manage during voltage swells, used in any types of DC voltage sources such as fuel cell and solar cell and improve the reliability by reducing EMI noise. Analysis and simulation results are presented to demonstrate these new findings.

  17. Neutron Spectrum Measurements from a Neutron Guide Tube Facility at the ETRR-1 Reactor

    International Nuclear Information System (INIS)

    The present work deals with measurements of the neutron spectrum emitted from a neutron guide tube (NGT) recently installed at one of the ETRR-1 reactor horizontal channels; designed to deliver thermal neutrons, free from fast neutrons and gamma-rays background, to a Fourier reverse-time-of-flight (RTOF) diffractometer. The measurements were preformed using a 6Li glass scintillation detector installed at 3.45 m from a disc Fermi chopper, combined with a multichannel analyzer set at channel width 4 mu sec. Also a theoretical model was especially developed for the neutron spectrum calculations. The spectrum calculated according to the developed model was found to be in good agreement with the measured one. It was found, both from measurements and calculations, that the spectrum emitted from the NGT covers, after transmission through a Fourier chopper, neutron wavelengths from 1-4 A degree. The maximum of the neutron spectrum was found to be at neutron wavelength lambda=1.39 A degree which is consistent with the value 1.377 A degree calculated for the curved NGT characteristic wavelength

  18. The Multiple Functions of T Stellate/Multipolar/Chopper Cells in the Ventral Cochlear Nucleus

    OpenAIRE

    Oertel, Donata; Wright, Samantha; Cao, Xiao-Jie; Ferragamo, Michael; Bal, Ramazan

    2010-01-01

    Acoustic information is brought to the brain by auditory nerve fibers, all of which terminate in the cochlear nuclei, and is passed up the auditory pathway through the principal cells of the cochlear nuclei. A population of neurons variously known as T stellate, type I multipolar, planar multipolar, or chopper cells forms one of the major ascending auditory pathways through the brain stem. T Stellate cells are sharply tuned; as a population they encode the spectrum of sounds. In these neurons...

  19. Polarization analysis for the thermal chopper spectrometer TOPAS

    Directory of Open Access Journals (Sweden)

    Voigt Jörg

    2015-01-01

    Full Text Available We report on the progress of the construction of the thermal time-of-flight spectrometer with polarization analysis TOPAS at the Mayer-Leibnitz Zentrum (MLZ. The instrument components approach the status to be ready for installation. The special feature of the instrument is its capability for wide-angle polarization analysis in the thermal spectral range. Here we describe a novel approach to rotate the neutron spin adiabatically into the X, Y or Z direction of the laboratory frame by combination of permanent magnets aligned as Halbach rings and electrically generated fields. Despite the severe spatial restrictions the design exhibits a very high adiabaticity and interacts only weakly with the coil layout for the analyzing 3He spin filter cell (SFC.

  20. Quasielastic high-resolution time-of-flight spectrometers employing multi-disk chopper cascades for spallation sources

    International Nuclear Information System (INIS)

    The design of multi-disk chopper time-of-flight (MTOF) spectrometers for high-resolution quasielastic and low-energy inelastic neutron scattering at spallation sources is discussed in some detail. A continuously variable energy resolution (1 μeV to 10 meV), and a large dynamic range (1 μeV to 100 meV), are outstanding features of this type of instrument, which are easily achieved also at a pulsed source using state-of-the-art technology. The method of intensity-resolution optimization of MTOF spectrometers at spallation sources is treated on the basis of the requirement of using (almost) 'all the neutrons of the pulse', taking into account the constant, but wavelength-dependent duration of the source pulse. It follows, that the optimization procedure (which is slightly different from that employed in the steady-state source case) should give priority to the highest resolution, whenever such a choice becomes necessary. This leads to long monochromator distances (Ll2) of the order of 50 m, for achieving resolutions now available at reactor sources. A few examples of spectrometer layout and corresponding design parameters for large-angle and for small-angle quasielastic scattering instruments are given. In the latter case higher energy resolution than for large-angle scattering is required and achieved. The use of phase-space transformers, neutron wavelength band-pass filters and multichromatic operation for the purpose of intensity-resolution optimization are discussed. This spectrometer can be designed to make full use of the pulsed source peak flux. Therefore, and because of a number of improvements, high resolution will be available at high intensity: for any given resolution the total intensity at the detectors, when placed at one of the planned new spallation sources (SNS, JSNS, ESS, AUSTRON) will be larger by at least three orders of magnitude than the total intensity of any of the presently existing instruments of this type in routine operation at steady

  1. Neutron spectrum measurements from a neutron guide tube facility at the ETRR-1 reactor

    International Nuclear Information System (INIS)

    The present work deals with measurements of the neutron spectrum emitted from a neutron guide tube (NGT) recently installed at one of the ETRR-1 reactor horizontal channels designed to deliver thermal neutrons, free from fast neutrons and gamma ray background, to a fourier reverse-time-of-flight (RTOF) diffractometer. The measurements were performed using a 6 Li glass scintillation detector combined with a multichannel analyzer set at channel width 4 M sec and installed at 3.4 m from a disc Fermi chopper. Also a theoretical model was specially developed for the neutron spectrum calculations. According to the model developed, the spectrum calculated was found to be in good agreement with the measured one. It was found, both from measurements and calculations, that the spectrum emitted from the NGT covers, after transmission through a fourier chopper, neutron wavelengths from 1-4 A adequate for neutron diffraction measurements at D values between 0.71-2.9 A respectively. 6 FIGS

  2. PERFORMING DIAGNOSTICS ON THE SPALLATION NEUTRON SOURCE VISION BEAM LINE TO ELIMINATE HIGH VIBRATION LEVELS AND PROVIDE A SUSTAINABLE OPERATION

    Energy Technology Data Exchange (ETDEWEB)

    Van Hoy, Blake W [ORNL

    2014-01-01

    The Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory (ORNL) provides variable energy neutrons for a variety of experiments. The neutrons proceed down beam lines to the experiment hall, which houses a variety of experiments and test articles. Each beam line has one or more neutron choppers which filter the neutron beam based on the neutron energy by using a rotating neutron absorbing material passing through the neutron beam. Excessive vibration of the Vision beam line, believed to be caused by the T0 chopper, prevented the Vision beam line from operating at full capacity. This problem had been addressed several times by rebalancing/reworking the T0 beam chopper but the problem stubbornly persisted. To determine the cause of the high vibration, dynamic testing was performed. Twenty-seven accelerometer and motor current channels of data were collected during drive up, drive down, coast down, and steady-state conditions; resonance testing and motor current signature analysis were also performed. The data was analyzed for traditional mechanical/machinery issues such as misalignment and imbalance using time series analysis, frequency domain analysis, and operating deflection shape analysis. The analysis showed that the chopper base plate was experiencing an amplified response to the excitation provided by the T0 beam chopper. The amplified response was diagnosed to be caused by higher than expected base plate flexibility, possibly due to improper grouting or loose floor anchors. Based on this diagnosis, a decision was made to dismantle the beam line chopper and remount the base plate. Neutron activation of the beam line components make modifications to the beam line especially expensive and time consuming due to the radiation handling requirements, so this decision had significant financial and schedule implications. It was found that the base plate was indeed loose because of improper grouting during its initial installation. The base plate was

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

    Science.gov (United States)

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

    2011-04-01

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

  4. Longitudinal Bunch Shape Monitor Using the Beam Chopper of the J-PARC

    CERN Document Server

    Naito, F

    2004-01-01

    We propose the longitudinal bunch shape monitor for the low energy part of the linac of the J-PARC. The monitor uses the beam chopper cavity installled in the MEBT line between thr RFQ and the DTL of the J-PARC as a kind of the bunch rotator. Consequentry the longitudinal bunch shape is measured along the horizontal direction. If we can measure the energy distribution of the bunch also, the longitudinal emittance of the beam is derived. In the paper, the basic idea of the monitor is discussed in detail.

  5. Rapid and economical data acquisition in ultrafast frequency-resolved spectroscopy using choppers and a microcontroller.

    Science.gov (United States)

    Guo, Liang; Monahan, Daniele M; Fleming, Graham

    2016-08-01

    Spectrometers and cameras are used in ultrafast spectroscopy to achieve high resolution in both time and frequency domains. Frequency-resolved signals from the camera pixels cannot be processed by common lock-in amplifiers, which have only a limited number of input channels. Here we demonstrate a rapid and economical method that achieves the function of a lock-in amplifier using mechanical choppers and a programmable microcontroller. We demonstrate the method's effectiveness by performing a frequency-resolved pump-probe measurement on the dye Nile Blue in solution. PMID:27505778

  6. SIMULATION AND IMPLEMENTATION OF PID-ANN CONTROLLER FOR CHOPPER FED EMBEDDED PMDC MOTOR

    OpenAIRE

    M. Madheswaran; Muruganandam, M.

    2012-01-01

    The closed loop control of PMDC drive with an inner current controller and an outer PID-ANN (Proportional Integral Derivative – Artificial Neural Network) based speed controller is designed and presented in this paper. Motor is fed by DC / DC buck converter (DC Chopper). The controller is used to change the duty cycle of the converter and thereby, the voltage fed to the PMDC motor to regulate the speed. The PID-ANN controller designed was evaluated by computer simulation and it was implemente...

  7. SIMULATION AND IMPLEMENTATION OF PID-ANN CONTROLLER FOR CHOPPER FED EMBEDDED PMDC MOTOR

    Directory of Open Access Journals (Sweden)

    M. Madheswaran

    2012-04-01

    Full Text Available The closed loop control of PMDC drive with an inner current controller and an outer PID-ANN (Proportional Integral Derivative – Artificial Neural Network based speed controller is designed and presented in this paper. Motor is fed by DC / DC buck converter (DC Chopper. The controller is used to change the duty cycle of the converter and thereby, the voltage fed to the PMDC motor to regulate the speed. The PID-ANN controller designed was evaluated by computer simulation and it was implemented using an 8051 based embedded system. This system will operate in forward motoring with variable speed.

  8. Monte-Carlo-simulations of a high resolution neutron TOF instrument at the FRM II

    International Nuclear Information System (INIS)

    It is proposed to build a flexible, high resolution time of flight diffractometer and spectrometer at the new reactor FRM II of the Technische Universitaet Muenchen. To optimize the layout of individual components and to estimate the performance of the entire instrument, analytical calculations and Monte-Carlo-simulations have been carried out mainly with 'McStas', programmed by RISO, Denmark. MC-simulation routines for neutron devices like curved guides, disc- and Fermi choppers have been added. The influence of diverging and curved guides in neutron phase space has been developed and are shown. Line shapes and widths of neutron pulses have been studied for disc- and Fermi choppers. Analytical calculations and MC-simulation results are discussed dependent on slit forms and beam asymmetries. (author)

  9. Design of the HEBT chopper system for multiple-energy operation at HIMAC

    International Nuclear Information System (INIS)

    To realize fast scanning irradiation without the use of the energy absorbers, NIRS has developed multiple-energy operation with more than 200 energy steps. This operation can change the output energy of the synchrotron quickly; however, a part of the circulating particles spills uncontrollably during the procedure of the energy variation. The cause of that is emittance growth due to beam deceleration, and we must prevent the spilled particles from delivering to the patient. For the purpose, we have developed the beam chopping system of the High Energy Beam Transport (HEBT) section. The chopping system will interrupt the beam within 1 ms, and it will allow the quick change of the output energy within 50 ms. This paper describes the system design of the HEBT chopper and its control scheme in multiple-energy operation. (author)

  10. A step-down chopper-controlled slip energy recovery induction motor drive

    Energy Technology Data Exchange (ETDEWEB)

    Refoufi, L. (Inst. National D' Electricite et D' Electronique, Boumerdes (Algeria)); Pillay, P. (Univ. of New Orleans, LA (United States). Dept. of Electrical Engineering); Harris, M.R. (Univ. of Southampton, England (United Kingdom). Dept. of Electrical Engineering)

    1993-09-01

    The design of a chopper-controlled slip energy recovery drive (SERIMD), also known as a static Kramer drive, demands an exact knowledge of the steady state and dynamic performance of the system over the complete operating range. To accomplish this, a coupled circuit approach is necessary whereby the self and mutual coupling effects, voltage and current harmonics in the machine and voltage and current ripple at different points in the drive system are duly taken into account. Such a model should enable the accurate prediction of all instantaneous current values which leads to accurate prediction of electric torque and harmonics injected into the supply. This paper presents a model to accomplish the above. Mathematical predictions are verified with detailed experimental results.

  11. Research on a new active power filter topology based on chopper circuit

    CERN Document Server

    Xiaoling, Guo; Bo, Zhang; Jing, Zhang

    2015-01-01

    The active power filter (APF) is attracting more and more attention for its outstanding performance in current and voltage ripple compensation. As modern high-energy accelerators are demanding much more stringent current ripple guideline, the APF is introduced to the magnet power supply (MPS) in accelerator system. However, the conventional APF has a lot of shortages and drawbacks due to its traditional topology, such as complex structure, nonadjustable working voltage, requirement of power supply, and so on. This paper proposes a new topology of APF, which is working as two types of chopper circuits. This APF need not extra electricity, but to use the power of the MPS current ripple to realize ripple depressing. At the end of this paper, the experiment result proves its feasibility and effect.

  12. Bi-level Control and Chopper Control Methods for Improving the Dynamic Performance of Stepper Motor

    Directory of Open Access Journals (Sweden)

    Dr. Walid Emar, Eng. Ziad Sobih, Dr. Musbah Aqel & Dr. Mahmoud Awad

    2010-06-01

    Full Text Available This paper compares between chopper control method and bi-level controlmethod. Both methods are used for improving the dynamic performance ofvariable reluctance stepper motor (VRSM by modifying its time constant andthus, increasing its stepping rate. Therefore, the initial torque developed by themotor is high; the switching from one coil to the next is faster than normal andconsequently, the rotor moves as quickly as it should be. The circuitry discussedin this paper is connected directly to the motor windings and the motor powersupply, and this circuitry is controlled by a digital system that determines whenthe switches are turned on or off. Each class of drive circuit is illustrated withpractical examples, but these examples are not intended as an exhaustivecatalog of the commercially available control circuits, nor is the information givenhere intended to substitute for the information found on the manufacturer'scomponent data sheets for the parts mentioned.

  13. Neutron Scattering Experiment Automation with Python

    International Nuclear Information System (INIS)

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory currently holds the Guinness World Record as the world most powerful pulsed spallation neutron source. Neutrons scattered off atomic nuclei in a sample yield important information about the position, motions, and magnetic properties of atoms in materials. A neutron scattering experiment usually involves sample environment control (temperature, pressure, etc.), mechanical alignment (slits, sample and detector position), magnetic field controllers, neutron velocity selection (choppers) and neutron detectors. The SNS Data Acquisition System (DAS) consists of real-time sub-system (detector read-out with custom electronics, chopper interface), data preprocessing (soft real-time) and a cluster of control and ancillary PCs. The real-time system runs FPGA firmware and programs running on PCs (C++, LabView) typically perform one task such as motor control and communicate via TCP/IP networks. PyDas is a set of Python modules that are used to integrate various components of the SNS DAS system. It enables customized automation of neutron scattering experiments in a rapid and flexible manner. It provides wxPython GUIs for routine experiments as well as IPython command line scripting. Matplotlib and numpy are used for data presentation and simple analysis. We will present an overview of SNS Data Acquisition System and PyDas architectures and implementation along with the examples of use. We will also discuss plans for future development as well as the challenges that have to be met while maintaining PyDas for 20+ different scientific instruments.

  14. Neutron Scattering Experiment Automation with Python

    Energy Technology Data Exchange (ETDEWEB)

    Zolnierczuk, Piotr A [ORNL; Riedel, Richard A [ORNL

    2010-01-01

    The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory currently holds the Guinness World Record as the world most powerful pulsed spallation neutron source. Neutrons scattered off atomic nuclei in a sample yield important information about the position, motions, and magnetic properties of atoms in materials. A neutron scattering experiment usually involves sample environment control (temperature, pressure, etc.), mechanical alignment (slits, sample and detector position), magnetic field controllers, neutron velocity selection (choppers) and neutron detectors. The SNS Data Acquisition System (DAS) consists of real-time sub-system (detector read-out with custom electronics, chopper interface), data preprocessing (soft real-time) and a cluster of control and ancillary PCs. The real-time system runs FPGA firmware and programs running on PCs (C++, LabView) typically perform one task such as motor control and communicate via TCP/IP networks. PyDas is a set of Python modules that are used to integrate various components of the SNS DAS system. It enables customized automation of neutron scattering experiments in a rapid and flexible manner. It provides wxPython GUIs for routine experiments as well as IPython command line scripting. Matplotlib and numpy are used for data presentation and simple analysis. We will present an overview of SNS Data Acquisition System and PyDas architectures and implementation along with the examples of use. We will also discuss plans for future development as well as the challenges that have to be met while maintaining PyDas for 20+ different scientific instruments.

  15. System for Automation of experiments on Neutron Fourier Diffractometer FSD

    CERN Document Server

    Bogdzel, A A; Butenko, V A; Drozdov, V A; Zhuravlev, V V; Kuzmin, E S; Levchanovsky, F V; Pole, A V; Prikhodko, V I; Sirotin, A P

    2004-01-01

    The report presents a description of the system for the automation of experiments on the Fourier neutron diffractometer FSD at the reactor IBR-2 in FLNR JINR. The system is a complex of hard- and software that enables necessary control of experiments and data acquisition and includes - detector electronics, - electronics and instruments in sample environment, - device for control of fast Fourier chopper of neutron beam, - electronics for measurement and acquisition of low- and high-resolution spectra, - software for control of spectrometers and automation of experiments. The description and characteristics of basic blocks together with characteristics of the special-purpose software are also provided.

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

    Science.gov (United States)

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

    2015-07-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time is conducted with static objects mainly due to the limited flux intensity of neutron beamline facilities and sometimes due to the limitations of the detectors. However, some applications require the studies of dynamic phenomena and can now be conducted at several high intensity beamlines such as the recently rebuilt ANTARES beam line at the FRM-II reactor. In this paper we demonstrate the capabilities of time resolved imaging for repetitive processes, where different phases of the process can be imaged simultaneously and integrated over multiple cycles. A fast MCP/Timepix neutron counting detector was used to image the water distribution within a model steam engine operating at 10 Hz frequency. Within neutron radiography for the future applications. The neutron spectrum of the ANTARES beamline as well as transmission spectra of a Fe sample were also measured with the Time Of Flight (TOF) technique in combination with a high resolution beam chopper. The energy resolution of our setup was found to be ~ 0.8% at 5 meV and ~ 1.7% at 25 meV. The background level (most likely gammas and epithermal/fast neutrons) of the ANTARES beamline was also measured in our experiments and found to be on the scale of 3% when no filters are installed in the beam. Online supplementary data available from stacks.iop.org/jinst/10/P07008/mmedia. The videos are given as supplementary material linked to the main article.

  17. Design of a medium-energy beam-transport line with an anti-chopper for the JAERI/KEK project

    International Nuclear Information System (INIS)

    The medium-energy beam-transport line (MEBT) plays an important role in reducing beam loss in the JAERI/KEK project. A MEBT was designed two years ago, with good beam matching and lower beam loss. To further reduce beam loss during the transient time of the chopper to meet the new requirement from the DTL, a medium-energy beam-transport line with an anti-chopper has been designed. The 3.5 m long transport line consists of nine quadrupole magnets, three bunchers and four chopper/anti-chopper cavities. It accomplishes two tasks: matching the beam from the RFQ to the acceptance of the DTL and chopping the beam to produce gaps for injection into the rapid-cycling ring, which follows the linac. A RF Chopper and an anti-chopper have been adopted in the lattice, resulting in a clean chopping effect and no beam losses during the transient time. Details of the beam dynamics analysis are given

  18. Design of a medium-energy beam-transport line with an anti-chopper for the JAERI/KEK project

    International Nuclear Information System (INIS)

    The medium-energy beam-transport line (MEBT) plays an important role in reducing beam loss in the JAERI/KEK project. A MEBT was designed two years ago, with good beam matching and lower beam loss. To further reduce beam loss during the transient time of the chopper to meet the new requirement from the DTL, a medium-energy beam-transport line with an anti-chopper has been designed. The 3.5 m long transport line consists of nine quadrupole magnets, three bunchers and four chopper/anti-chopper cavities. It accomplishes two tasks: matching the beam from the RFQ to the acceptance of the DTL and chopping the beam to produce gaps for injection into the rapid-cycling ring, which follows the linac. An RF Chopper and an anti-chopper have been adopted in the lattice, resulting in a clean chopping effect, and no beam losses during the transient time. Details of the beam dynamics analysis are given. (author)

  19. Neutron Spectra Near to a Temperature Discontinuity in Graphite

    International Nuclear Information System (INIS)

    Thermal neutron spectra have been measured on either side of a temperature discontinuity in a large graphite stack. The stack was fed with thermal neutrons from the source reactor LIDO. Spectra were measured by the time-of-flight method using a chopper, and also by integral activation techniques. Simple diffusion theory calculations considering two Maxwellian groups give as good agreement with the measured 'neutron temperature' distributions as multigroup transport theory. Direction-averaged spectra were calculated using the transport theory code WDSN, with 39 thermal energy groups. Results using heavy gas (mass 30 or 35) scattering kernels for graphite or realistic kernels based on the measured scattering law give agreement with the measured spectra to better than 10%. The measured spectra of fluxes in the direction of the neutron current were found to be dependent on the orientation of the graphite blocks since the mean free path of neutrons in graphite depends on its extrusion direction. (author)

  20. Design and manufacture of neutron time of flight spectrometer on China Advanced Research Reactor

    International Nuclear Information System (INIS)

    The cold or thermal neutron energy spectra on China Advanced Research Reactor (CARR) could be directly measured by neutron time of flight spectrometer. Spectrometer structure and selected parameters of its key components were introduced. The impact of chopper slit and flux limit slit on neutron counts and pulse width was analyzed. The formulas of neutron counts and pulse width which were dependent on neutron wavelength were acquired. According to neutron energy spectrum measurement requirement for high fluence rate neutron beam, low-sensitivity detector, detector flux limit slit and multi-channel scaler for data acquisition were selected. These would ensure that the count loss rate was less than 0.5%. Electronics framework of detection system was designed and the total resolution time was 22.15-29.46 μs. (authors)

  1. The neutron reflectometer at 'SINQ'

    International Nuclear Information System (INIS)

    SINQ's dedicated reflectometer will be a flexible instrument in many respect. A 'white beam time of flight' as well as a 'constant wavelength' setup are possible for reflectometric experiments in a vertical scattering geometry. The phase controlled double chopper at the beginning of the instrument together with properly chosen time channels at the detector allow for the variation of the temporal resolution. Collimation slits serve to determine the angular resolution. In combination, the resolution can be tailored to the experimental needs. Additionally, one can adjust the illumination of the sample by setting the sample table and the detector to an appropriate distance. A mounting for exchangeable mirrors can be used to supply polarized neutrons by a multilayer polarizer or monochromatic neutrons by a multilayer monochromator. When it is equipped with a supermirror as a deflecting unit one can maintain a horizontal sample position which makes reflectometry on liquid samples practicable. Remanent polarizers are assigned for the changing over of the neutron polarization. A 1 T electromagnet installed on the sample manipulation table and polarization analyzers complete the polarized reflectometry setup. Alternately, an x-y-detector and single detectors will be available. By 1997/1998 the neutron reflectometer will be operational as a users' instrument. (author) 9 figs., 2 tabs., 30 refs

  2. The neutron reflectometer at `SINQ`

    Energy Technology Data Exchange (ETDEWEB)

    Clemens, D. [Lab. for Neutron Scattering ETH Zurich, Zurich (Switzerland) and Paul Scherrer Institute, Villigen (Switzerland)

    1996-11-01

    SINQ`s dedicated reflectometer will be a flexible instrument in many respect. A `white beam time of flight` as well as a `constant wavelength` setup are possible for reflectometric experiments in a vertical scattering geometry. The phase controlled double chopper at the beginning of the instrument together with properly chosen time channels at the detector allow for the variation of the temporal resolution. Collimation slits serve to determine the angular resolution. In combination, the resolution can be tailored to the experimental needs. Additionally, one can adjust the illumination of the sample by setting the sample table and the detector to an appropriate distance. A mounting for exchangeable mirrors can be used to supply polarized neutrons by a multilayer polarizer or monochromatic neutrons by a multilayer monochromator. When it is equipped with a supermirror as a deflecting unit one can maintain a horizontal sample position which makes reflectometry on liquid samples practicable. Remanent polarizers are assigned for the changing over of the neutron polarization. A 1 T electromagnet installed on the sample manipulation table and polarization analyzers complete the polarized reflectometry setup. Alternately, an x-y-detector and single detectors will be available. By 1997/1998 the neutron reflectometer will be operational as a users` instrument. (author) 9 figs., 2 tabs., 30 refs.

  3. TOSCA incoherent inelastic neutron spectrometer. Progress and results

    International Nuclear Information System (INIS)

    The back-scattering part (phase I) of the new incoherent inelastic neutron spectrometer, TOSCA, replacing the old TFXA, has been successfully installed at the ISIS pulsed neutron spallation source. The results, owing to the much larger detector area, show a significant enhancement of the counting rate and a slight improvement of the low energy resolution. In spring 2000 the forward scattering bank (phase II) will be completed and, during the final installation, the whole instrument will be moved from the present 12 m of primary flight path to 17 m. This will result in a large improvement of the overall resolution (from 2-3% to 1-1.5% of the energy transfer). In addition, a chopper will be added in order to avoid neutron frame overlap and to reduce the fast neutron background. (author)

  4. Levels in 237U studied by resonant neutron capture

    International Nuclear Information System (INIS)

    Primary and secondary γ rays in 237U from resonant neutron capture in 236U have been measured with the fast chopper facility, the neutron monochromator, and 2- and 24-keV neutron beam filters. A level scheme was constructed including 27 levels with spin and parity assignments. Rotational band members of the Nilsson configurations [631arrow-down], [622up-arrow], [624arrow-down], [631up-arrow], [633arrow-down], and [501arrow-down] and of the vibrational bands ][622up-arrow] - 2+] and ][631arrow-down] + 0+] were identified. There are more levels below 800 keV, in particular, K = 1/2- bands, than expected from comparison with 235U and 239U. The neutron binding energy in 237U was determined to be 5125.9 +- 0.5 keV

  5. Current Development Status of Time-of-Flight Inelastic Neutron Spectrometer at HANARO

    International Nuclear Information System (INIS)

    As part of the Cold Neutron Research Facility (CNRF) project launched in 2003, disk chopper time-off light (DC-TOF) spectrometer was proposed for the study of slow dynamics of all condensed matter sciences, which has been increasingly proven to be invaluable information. Here we present the current status of the DC-TOF instrument development. The HANARO research reactor has started operation since 1995 and reached its full operation power of 30 MW in 2004. Three neutron scattering instruments such as HRPD, FCD and SANS have been since running for user program, both domestic and foreign researchers. Till now, however there has been no inelastic neutron spectrometer in Korea, which has deterred otherwise natural growth of an inelastic neutron scattering community. Disk chopper time-of-flight inelastic neutron spectrometer is an advanced neutron scattering instrument, which has been proven worldwide to be very versatile for both basic science and material engineering studies. Therefore, when the Korea Atomic Energy Research Institute (KAERI) started the CNRF project in 2003, it was a natural choice that it decided to build DC-TOF for the cold neutron laboratory. Day-1 instruments of the CNRF project include a DC-TOF, a cold TAS, a 40m-SANS, and two reflectometers. In this paper, we present the current design specifications of the DC-TOF at the KAERI

  6. The multipurpose time-of-flight neutron reflectometer “Platypus” at Australia's OPAL reactor

    Science.gov (United States)

    James, M.; Nelson, A.; Holt, S. A.; Saerbeck, T.; Hamilton, W. A.; Klose, F.

    2011-03-01

    In this manuscript we describe the major components of the Platypus time-of-flight neutron reflectometer at the 20 MW OPAL reactor in Sydney, Australia. Platypus is a multipurpose spectrometer for the characterisation of solid thin films, materials adsorbed at the solid-liquid interface and free-liquid surfaces. It also has the capacity to study magnetic thin films using spin-polarised neutrons. Platypus utilises a white neutron beam ( λ=2-20 Å) that is pulsed using boron-coated disc chopper pairs; thus providing the capacity to tailor the wavelength resolution of the pulses to suit the system under investigation. Supermirror optical components are used to focus, deflect or spin-polarise the broad bandwidth neutron beams, and typical incident spectra are presented for each configuration. A series of neutron reflectivity datasets are presented, indicating the quality and flexibility of this spectrometer. Minimum reflectivity values of Platypus time-of-flight neutron reflectometer are presented.

  7. Charging of capacitors with double switch. The principle of operation of auto-zero and chopper-stabilized DC amplifiers

    CERN Document Server

    Yordanov, Vasil G; Manolev, Stojan G; Mishonov, Todor M

    2015-01-01

    The principle of operation of auto-zero and chopper-stabilized DC amplifiers, which is realized in many contemporary operational amplifiers is illustrated by a simple experimental setup given at the Open Experimental Physics Olympiad 2014 - "The Day of the Capacitor", held in Sofia and Gevgelija. The Olympiad was organized by the Sofia Branch of the Union of Physicists in Bulgaria and the Regional Society of Physicists of Strumica, Macedonia. In addition to the solution of the secondary school task in the paper is given a detailed engineering description of the patent by Edwin Goldberg and Jules Lehmann, Stabilized direct current amplifier, U.S. Patent 2,684,999 (1949).

  8. A chopper current-feedback instrumentation amplifier with a 1 mHz 1/f noise corner and an AC-coupled ripple reduction loop

    OpenAIRE

    Wu, R; Makinwa, K.A.A.; Huijsing, J.H.

    2009-01-01

    This paper presents a chopper instrumentation amplifier for interfacing precision thermistor bridges. For high CMRR and DC gain, the amplifier employs a three-stage current-feedback topology with nested-Miller compensation. By chopping both the input and intermediate stages of the amplifier, a 1 mHz 1/f noise corner was achieved at an input-referred noise power spectral density (PSD) of 15 nV/¿Hz. To reduce chopper ripple, the amplifier employs a continuous-time AC-coupled ripple reduction l...

  9. Visualization of cavitation phenomena in a Diesel engine fuel injection nozzle by neutron radiography

    Science.gov (United States)

    Takenaka, N.; Kadowaki, T.; Kawabata, Y.; Lim, I. C.; Sim, C. M.

    2005-04-01

    Visualization of cavitation phenomena in a Diesel engine fuel injection nozzle was carried out by using neutron radiography system at KUR in Research Reactor Institute in Kyoto University and at HANARO in Korea Atomic Energy Research Institute. A neutron chopper was synchronized to the engine rotation for high shutter speed exposures. A multi-exposure method was applied to obtain a clear image as an ensemble average of the synchronized images. Some images were successfully obtained and suggested new understanding of the cavitation phenomena in a Diesel engine fuel injection nozzle.

  10. Basic neutronics. Neutrons migration

    International Nuclear Information System (INIS)

    This article presents the basic neutronics necessary for the understanding of the operation of the different types of nuclear reactors: 1 - introduction to neutronics: principle of fission chain reactions, fast neutron reactors and thermal neutron reactors, capture, neutron status, variations with the reactor lattices; 2 - Boltzmann equation: neutrons population, neutrons migration, characterization of neutrons population and reactions, integral form of the Boltzmann equation, integral-differential form, equivalence between the two forms; 3 - reactor kinetics: fast neutrons and delayed neutrons, kinetic equations in punctual model, Nordheim equation, reactivity jumps, reactivity ramp; 4 - diffusion equation: local neutron status, Fick's law, diffusion equation, initial, boundary and interface conditions, nuclei in infinite and homogenous medium, some examples of solutions, developments in Eigenmodes; 5 - one-group theory: equation of the 'one-group - diffusion' theory, critical condition of the naked and homogenous reactor, critical condition of a reactor with reflectors, generalizations; 6 - neutrons moderation: different moderation mechanisms, elastic shock laws, moderation equation, some examples of solutions; 7 - resonance absorption of neutrons: advantage of the discontinuous moderation character, advantage of an heterogenous disposition, classical formula of the anti-trap factor in homogenous and heterogenous situation; 8 - neutrons thermalization: notions of thermalization mechanisms, thermalization equation, Maxwell spectrum, real spectrum, classical formula of the thermal utilisation factor, classical formula of the reproduction factor, moderation optimum. (J.S.)

  11. Pulse width control at 106 pulses/sec and 15 kV for the KAON factory beam chopper

    International Nuclear Information System (INIS)

    A beam chopper is required in the transfer line between the 1 GeV/c TRIUMF cyclotron and the Accumulator ring of the pro-posed 30 GeV/c KAON Factory synchrotrons. The beam chopper must generate pulses with a magnitude of at l-t 9.5 kV, with rise and fall times of less than 38 ns, at a repetition rate of 106 pulses per second, and at a 100% duty cycle. Precise control of grid timing aid voltage is required at the driver tetrode to achieve deflector kick pulse widths of 48 ns and 92 ns while maintaining an interpulse and flattop ripple at less than ±10% of the deflector kick magnitude. Results of measurements are presented where all of the design criteria have been met, for the first time, over a wide range of pulse widths with sub-nanosecond precision. Rise and fall times of 18 ns to 31 ns have been achieved on 15 kV pulses at 0.93 x 106 pulses per second continuous operation. (author) 10 refs., 9 figs., 1 tab

  12. Basic Design Report of DC-TOF Inelastic Neutron Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    So, Ji Yong; Park, Je Geun; Moon, Myung Kook; Cho, Sang Jin; Choi, Yung Hyun; Lee, Chang Hee

    2006-04-15

    We made Basic designs of neutron guide, choppers, and detectors in order to optimize the design parameters of DC-TOF to be built in the HANARO Cold Neutron Guide Hall. In addition, we calculated the expected performance of DC-TOF using Monte Carlo simulations and evaluated the properties of neutron beam. Based on the results we obtained, we have compared the expected performance of the DC-TOF with those of existing instruments overseas. In conclusion, we believe that we will be able to construct the DC-TOF at HANARO as one of the best instruments of its kinds and it will become an invaluable instrument to researchers in the related field.

  13. Advanced Neutron Reflectometer for Investigation on Dynamic/Static Structures of Soft-Interfaces in J-PARC

    Energy Technology Data Exchange (ETDEWEB)

    Mitamura, Koji; Takahara, Atsushi [JST, ERATO Takahara Soft Interfaces Project (Japan); Yamada, Norifumi L; Sagehashi, Hidenori; Seto, Hideki [High Energy Accelerator Research Organization (KEK) (Japan); Torikai, Naoya [Graduate School of Engineering, Mie University (Japan); Sugita, Tsukasa; Furusaka, Michihiro, E-mail: takahara@cstf.kyushu-u.ac.jp [Graduate School of Engineering, Hokkaido University (Japan)

    2011-01-01

    A novel neutron reflectometer with horizontal geometry will be established at BL16 in Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC) as a successor of a reflectometer ARISA-II. ARISA-II corresponding to a single neutron beam downward at 2.22 deg has achieved off-specular and time-resolved reflectivity measurements. The novel reflectometer is designed so as to receive two tilted neutron beams (2.22 and 5.71 deg), which gives us an opportunity in investigation on a free liquid surface. The reflectometer can provide a micro-sized beam by slit collimation and obtain a fair reflectivity with small sample area. Also, T0 chopper and neutron focusing mirror are newly introduced. The T0 chopper can suppress the background due to fast neutrons. The focusing mirror produces further reduction of measurement time not only for specular reflection by focusing neutrons on a sample, but also grazing incidence small-angle neutron scattering (GISANS) measurements by focusing on a detector.

  14. Neutron polarizing set-up of the Sofia IRT research reactor

    International Nuclear Information System (INIS)

    Neutron polarizing set-up of one of the horizontal beam tubes of the IRT-200 research reactor of the Bulgarian Institute of Nuclear Research and Nuclear Energy is presented. Neutron mirrors are extensively used in an effort to compensate the moderate reactor beam intensity by the high reflected intensity and wide-band transmittance of the mirror neutron guides. Time-to-flight technique using a slotted neutron absorbing chopper with a horizontal rotation axis has been applied to obtain the exit neutron spectra. Beam polarization and flipping ratios have been determined. Cadmium ratio in the polarized beam has been found almost 104 and the average polarization has been measured to be higher than 96%. 3 figs, 3 refs

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

    International Nuclear Information System (INIS)

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

  16. Neutron diffractometers for structural biology at spallation neutron sources

    International Nuclear Information System (INIS)

    Spallation neutron sources are ideal for diffraction studies of proteins and oriented molecular complexes. With spoliation neutrons and their time dependent wavelength structure, it is easy to electronically select data with an optimal wavelength bandwidth and cover the whole Laue spectrum as time (wavelength) resolved snapshots. This optimized data quality with best peak-to-background ratios and provides adequate spatial and energy resolution to eliminate peak overlaps. The application of this concept will use choppers to select the desired Laue wavelength spectrum and employ focusing optics and large cylindrical 3He detectors to optimize data collection rates. Such a diffractometer will cover a Laue wavelength range from 1 to 5 Angstrom with a flight path length of 10m and an energy resolution of 0.25 Angstrom. Moderator concepts for maximal flux distribution within this energy range will be discussed using calculated flux profiles. Since the energy resolution required for such timed data collection in this super Laue techniques is not very high, the use of a linac only (LAMPF) spoliation target is an exciting possibility with an order of magnitude increase in flux

  17. Neutron diffractometers for structural biology at spallation neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Schoenborn, B.P.; Pitcher, E. [Los Alamos National Laboratory, NM (United States)

    1994-12-31

    Spallation neutron sources are ideal for diffraction studies of proteins and oriented molecular complexes. With spoliation neutrons and their time dependent wavelength structure, it is easy to electronically select data with an optimal wavelength bandwidth and cover the whole Laue spectrum as time (wavelength) resolved snapshots. This optimized data quality with best peak-to-background ratios and provides adequate spatial and energy resolution to eliminate peak overlaps. The application of this concept will use choppers to select the desired Laue wavelength spectrum and employ focusing optics and large cylindrical {sup 3}He detectors to optimize data collection rates. Such a diffractometer will cover a Laue wavelength range from 1 to 5{Angstrom} with a flight path length of 10m and an energy resolution of 0.25{Angstrom}. Moderator concepts for maximal flux distribution within this energy range will be discussed using calculated flux profiles. Since the energy resolution required for such timed data collection in this super Laue techniques is not very high, the use of a linac only (LAMPF) spoliation target is an exciting possibility with an order of magnitude increase in flux.

  18. The design of the inelastic neutron scattering mode for the Extreme Environment Diffractometer with the 26 T High Field Magnet

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, Maciej, E-mail: maciej.bartkowiak@helmholtz-berlin.de; Stüßer, Norbert; Prokhnenko, Oleksandr

    2015-10-11

    The Extreme Environment Diffractometer is a neutron time-of-flight instrument, designed to work with a constant-field hybrid magnet capable of reaching fields over 26 T, unprecedented in neutron science; however, the presence of the magnet imposes both spatial and technical limitations on the surrounding instrument components. In addition to the existing diffraction and small-angle neutron scattering modes, the instrument will operate also in an inelastic scattering mode, as a direct time-of-flight spectrometer. In this paper we present the Monte Carlo ray-tracing simulations, the results of which illustrate the performance of the instrument in the inelastic-scattering mode. We describe the focussing neutron guide and the chopper system of the existing instrument and the planned design for the instrument upgrade. The neutron flux, neutron spatial distribution, divergence distribution and energy resolution are calculated for standard instrument configurations.

  19. The design of the inelastic neutron scattering mode for the Extreme Environment Diffractometer with the 26 T High Field Magnet

    International Nuclear Information System (INIS)

    The Extreme Environment Diffractometer is a neutron time-of-flight instrument, designed to work with a constant-field hybrid magnet capable of reaching fields over 26 T, unprecedented in neutron science; however, the presence of the magnet imposes both spatial and technical limitations on the surrounding instrument components. In addition to the existing diffraction and small-angle neutron scattering modes, the instrument will operate also in an inelastic scattering mode, as a direct time-of-flight spectrometer. In this paper we present the Monte Carlo ray-tracing simulations, the results of which illustrate the performance of the instrument in the inelastic-scattering mode. We describe the focussing neutron guide and the chopper system of the existing instrument and the planned design for the instrument upgrade. The neutron flux, neutron spatial distribution, divergence distribution and energy resolution are calculated for standard instrument configurations

  20. Measurement of double-differential neutron emission cross sections of 238U, 232Th and 12C for 18 MeV neutrons

    International Nuclear Information System (INIS)

    Double-differential neutron emission cross sections of 238U, 232Th and 12C have been measured for 18-MeV incident neutrons using the neutron time-of-flight technique and Tohoku University 4.5MV Dynamitron accelerator as a pulsed neutron generator. In the experiment, energy resolution of the spectrometer was improved by employing a newly developed post-acceleration beam-chopper and by adjustment of timing property of the neutron detector. Measurements were made at laboratory angles between 30- and 145- deg., and data were obtained for secondary neutrons between 0.8 and 18 MeV. In the data processing, a care was taken for the data correction for the effects of parasitic neutrons associated with primary neutrons; the correction proved to be of special importance in the present measurement. We compared the data obtained in the present experiment with the evaluated data, JENDL-3 and ENDF/B-IV (B-V for 12C), and discussed the origin of the discrepancies. The anisotropy observed for secondary neutrons from 238U and 232Th was found to be reproduced by Kalbach-Mann systematics on the assumption of isotropy of fission neutrons. The experimental results for 12C showed marked discrepancies concerning the scattering cross sections and neutron spectrum in the continuum region. (author)

  1. Neutron Compound Refractive Prisms - DOE SBIR Phase II Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Cremer, Jr, Jay Theodore

    2011-06-25

    The results of the research led to a pulsed electromagnetic periodic magnetic field array (PMF), which coupled with a pair of collimation slits, and a mechanical chopper slit, were able to deflect spin-up neutrons to a band of line-fused neutrons a focal plane heights that correspond to the time-varying magnetic field amplitude. The electromagnetic field PMF produced 5.4 pulses per minute in which each pulse was 50 msec in duration with a full width half maximum (FWHM) of 7.5 msec. The calculated 7.7 mm vertical height of the band of focused spin-up neutrons corresponded closely to the measured 7.5 mm height of the center line of the imaged band of neutrons. The band of deflected spin-up neutrons was 5 mm in vertical width and the bottom of the band was 5 mm above the surface of the PMF pole. The limited exposure time of 3 hours and the smaller 0.78 T magnetic field allowed focused and near focused neutrons of 1.8 to 2.6 neutrons, which were in the tails of the McClellan Nuclear Radiation Center Bay 4 Maxwell Boltzmann distribution of neutrons with peak flux at 1.1-1.2. The electromagnetic PMF was expected to produces a 2.0 T peak magnetic field amplitude, which would be operational at a higher duty factor, rather than the as built 7.5 msec FWHM with pulse repetition frequency of 5.4 pulses per minute. The fabricated pulsed electromagnetic PMF with chopper is expected to perform well on a cold, very cold or ultra cold beam line as a spectrometer or monochromator source of spin-up polarized neutron. In fact there may be a possible use of the PMF to do ultra-cold neutron trapping, see paper by A. I. Frank1, V. G. Nosov, Quantum Effects in a One-Dimensional Magnetic Gravitational Trap for Ultracold Neutrons, JETP Letters, Vol. 79, No. 7, 2004, pp. 313-315. The next step is to find a cold or very cold neutron facility, where further testing or use of the pulsed magnetic field PMF can be pursued.

  2. FieldChopper, a new tool for automatic model generation and virtual screening based on molecular fields.

    Science.gov (United States)

    Kalliokoski, Tuomo; Ronkko, Toni; Poso, Antti

    2008-06-01

    Algorithms were developed for ligand-based virtual screening of molecular databases. FieldChopper (FC) is based on the discretization of the electrostatic and van der Waals field into three classes. A model is built from a set of superimposed active molecules. The similarity of the compounds in the database to the model is then calculated using matrices that define scores for comparing field values of different categories. The method was validated using 12 publicly available data sets by comparing the method to the electrostatic similarity comparison program EON. The results suggest that FC is competitive with more complex descriptors and could be used as a molecular sieve in virtual screening experiments when multiple active ligands are known. PMID:18489083

  3. Analysis and simulation of a small-angle neutron scattering instrument on a 1 MW long pulse spallation source

    International Nuclear Information System (INIS)

    We studied the design and performance of a small-angle neutron scattering (SANS) instrument for a proposed 1 MW, 60 Hz long pulsed spallation source at the Los Alamos Neutron Science Center (LANSCE). An analysis of the effects of source characteristics and chopper performance combined with instrument simulations using the LANSCE Monte Carlo instrument simulations package shows that the T0 chopper should be no more than 5 m from the source with the frame overlap and frame definition choppers at 5.6 and greater than 7 m, respectively. The study showed that an optimal pulse structure has an exponential decaying tail with τ ∼ 750 μs. The Monte Carlo simulations were used to optimize the LPSS SANS, showing that an optimal length is 18 m. The simulations show that an instrument with variable length is best to match the needs of a given measurement. The performance of the optimized LPSS instrument was found to be comparable with present world standard instruments

  4. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Science.gov (United States)

    Simeoni, G. G.; Valicu, R. G.; Borchert, G.; Böni, P.; Rasmussen, N. G.; Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A.

    2015-12-01

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4-10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  5. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    International Nuclear Information System (INIS)

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers

  6. Focusing adaptive-optics for neutron spectroscopy at extreme conditions

    Energy Technology Data Exchange (ETDEWEB)

    Simeoni, G. G., E-mail: ggsimeoni@outlook.com [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Valicu, R. G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Physics Department E13, Technical University of Munich, D-85748 Garching (Germany); Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Borchert, G. [Heinz Maier-Leibnitz Zentrum (MLZ), FRM II, Technical University of Munich, D-85748 Garching (Germany); Böni, P. [Physics Department E21, Technical University of Munich, D-85748 Garching (Germany); Rasmussen, N. G. [Nanoscience Center, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen (Denmark); Yang, F.; Kordel, T.; Holland-Moritz, D.; Kargl, F.; Meyer, A. [Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln (Germany)

    2015-12-14

    Neutron Spectroscopy employing extreme-conditions sample environments is nowadays a crucial tool for the understanding of fundamental scientific questions as well as for the investigation of materials and chemical-physical properties. For all these kinds of studies, an increased neutron flux over a small sample area is needed. The prototype of a focusing neutron guide component, developed and produced completely at the neutron source FRM II in Garching (Germany), has been installed at the time-of-flight (TOF) disc-chopper neutron spectrometer TOFTOF and came into routine-operation. The design is based on the compressed Archimedes' mirror concept for finite-size divergent sources. It represents a unique device combining the supermirror technology with Adaptive Optics, suitable for broad-bandwidth thermal-cold TOF neutron spectroscopy (here optimized for 1.4–10 Å). It is able to squeeze the beam cross section down to a square centimeter, with a more than doubled signal-to-background ratio, increased efficiency at high scattering angles, and improved symmetry of the elastic resolution function. We present a comparison between the simulated and measured beam cross sections, as well as the performance of the instrument within real experiments. This work intends to show the unprecedented opportunities achievable at already existing instruments, along with useful guidelines for the design and construction of next-generation neutron spectrometers.

  7. AMOR – the time-of-flight neutron reflectometer at SINQ/PSI

    Indian Academy of Sciences (India)

    Mukul Gupta; T Gutberlet; J Stahn; P Keller; D Clemens

    2004-07-01

    The apparatus for multioptional reflectometry (AMOR) at SINQ/PSI is a versatile reflectometer operational in the time-of-flight (TOF) mode (in a wavelength range of 0.15 nm > > 1.3 nm) as well as in the monochromatic ( - 2) mode with both polarized and unpolarized neutrons. AMOR is designed to perform reflectometry measurements in horizontal sample-plane geometry which allows studying both solid–liquid and liquid–liquid interfaces. A pulsed cold neutron beam from the end position of the neutron guide is produced by a dual-chopper system (side-by-side) having two windows at 180° and rotatable with a maximum frequency of 200 Hz. In the TOF mode, the chopper frequency, width of the gating window and the chopper–detector distance can be selected independently providing a wide range of -resolution ( / = 1–10%). Remanent FeCoV/Ti : N supermirrors are used as polarizer/analyzer with a polarization efficiency of ∼ 97%. For the monochromatic wavelength mode, a Ni/Ti multilayer is used as a monochromator, giving ∼ 50% reflectivity at a wavelength of 0.47 nm. In the present work, a detailed description of the instrument and setting-up of the polarization option is described. Results from some of the recent studies with polarized neutrons and measurements on liquid surfaces are presented.

  8. Prompt gamma neutron activation analysis as an active interrogation technique for nuclear materials

    International Nuclear Information System (INIS)

    Prompt gamma neutron activation analysis (PGAA) is proposed as an instant, non-destructive method for the analysis of fissile materials and fission products. Measurements by PGAA were made on technetium and uranium compounds, the latter with various enrichments. Measurements were carried out in thermal and cold neutron beams at the Budapest Research Reactor. A beam chopper was used to collect the delayed decay gamma radiation from short lived nuclides separately. Accurate partial gamma ray production cross-sections were determined with internal standardization for a set of prompt and decay gamma rays following neutron capture in 235U, 238U and 99Tc and compared to those from the literature. In the case of 235U fission, prompt gamma lines were also applied.These cross-sections can be used for non-destructive analyses of uranium and technetium and also for the determination of the enrichment of uranium by prompt gamma activation analysis and neutron activation analysis. (author)

  9. Measurement of free neutron lifetime by electron decay detection with a migration chamber

    International Nuclear Information System (INIS)

    In this study, the different aspects of the realization of the experimental setup are successively described: creation of a pulsed monochromatic neutron beam, design and construction of a detector for neutron decay electrons, development of electronics and of the data acquisition system, measurement of the helium-3 density in a gaseous mixture. A mechanical system called double chopper and a monochromator crystal are used to obtain neutron bursts with a length of about 28 cm and a velocity of 846 m/s. The electron detector is a time projection chamber (TPC) filled at atmospheric pressure with a helium-4 (93%), helium-3 (10-5%) and carbon dioxide (7%) mixture. The problems encountered during the data acquisition with the neutron beam and preliminary results from analysis are also presented

  10. Resolution kernels in time-of-flight neutron reflectometers

    International Nuclear Information System (INIS)

    Instrumental resolution functions must be taken into account when analysing Neutron Reflectometry data. These resolution functions are obtained by convolving the resolution kernels for the angular and wavelength components. In the past most data reduction and analysis processes have assumed that the overall resolution kernel is Gaussian in shape. Whilst this is the case for monochromatic reflectometers this is not true for those Time-Of-Flight (TOF) Neutron Reflectometers, such as Platypus which possess rectangular wavelength resolution distributions (a consequence of the disc chopper systems used). In such situations the resolution function is typically trapezoidal in shape. Here we detail how a more detailed description of the instrumental resolution function is calculated2. In addition, we outline the situations where the differences between the detailed and approximate resolution kernels become apparent, with the main effects being observed when the width of the resolution kernel is similar to the width of the features in the reflectivity curve.

  11. The wavelength frame multiplication chopper system for the ESS test beamline at the BER II reactor—A concept study of a fundamental ESS instrument principle

    International Nuclear Information System (INIS)

    Contributing to the design update phase of the European Spallation Source ESS–scheduled to start operation in 2019–a test beamline is under construction at the BER II research reactor at Helmholtz Zentrum Berlin (HZB). This beamline offers experimental test capabilities of instrument concepts viable for the ESS. The experiments envisaged at this dedicated beamline comprise testing of components as well as of novel experimental approaches and methods taking advantage of the long pulse characteristic of the ESS source. Therefore the test beamline will be equipped with a sophisticated chopper system that provides the specific time structure of the ESS and enables variable wavelength resolutions via wavelength frame multiplication (WFM), a fundamental instrument concept beneficial for a number of instruments at ESS. We describe the unique chopper system developed for these purposes, which allows constant wavelength resolution for a wide wavelength band. Furthermore we discuss the implications for the conceptual design for related instrumentation at the ESS

  12. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 microseconds

    CERN Document Server

    Lam, Jessica; Softley, Tim

    2015-01-01

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 microseconds. Molecular beams seeded with NO or with Br2 and an initial pulse width of greater or equal to 200 microseconds were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3,000 rpm to 80,000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 microseconds to 13 microseconds, and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  13. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 μs

    International Nuclear Information System (INIS)

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br2 and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature

  14. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br{sub 2} down to 13 μs

    Energy Technology Data Exchange (ETDEWEB)

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P. [Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA (United Kingdom)

    2015-05-15

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br{sub 2} and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br{sub 2}. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  15. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 μs

    Science.gov (United States)

    Lam, Jessica; Rennick, Christopher J.; Softley, Timothy P.

    2015-05-01

    A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br2 and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br2. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.

  16. Finite element analysis of interface stress between neutron absorption coating and chop disk

    International Nuclear Information System (INIS)

    The performance of disk chopper is directly affected by bond strength between neutron absorption coating and chop disk. Based on the finite element analysis software ANSYS, the interface stress distribution under high speed centrifugal load was calculated, which was to investigate the effects of coating's elastic modulus, poisson ratio and coating thickness on the interfacial stress distribution. The results show that soft and tough coating can reduce the peak stress effectively, and coating thickness reducing is helpful to avoid the plastic failure of opening in the disk under high speed centrifugal load. (authors)

  17. A method for comparison of experimental and theoretical differential neutron spectra in the Zenith reactor

    International Nuclear Information System (INIS)

    A method of calculation is given which assists the analyses of chopper measurements of spectra from ZENITH and enables complex multigroup theoretical calculations of the spectra to be put into a form which may be compared with experiment. In addition the theory of the cut-off function has been extended to give analytical expressions which take into account the effects of sub-collimators, off centre slits and of a rotor made of a material partially transparent to neutrons. The theoretical cut-off function suggested shows good agreement with experiment. (author)

  18. Polarized neutron spectrometer for inelastic experiments at J-PARC - Status of POLANO project

    International Nuclear Information System (INIS)

    The construction of the newly developed polarization analysis neutron chopper spectrometer (POLANO) has begun in the Japan Proton Accelerator Research Complex (J-PARC), Materials and Life Science Experimental Facility (MLF). POLANO is a direct geometry chopper spectrometer with neutron polarization analysis capability for inelastic scattering experiments. In the suite of inelastic spectrometers, six instruments are now in operation involving direct geometry, inverted geometry, and spin echo instruments. POLANO will be the only spectrometer dedicated to polarization analysis experiments. The polarizer, analyzer, and other magnetic devices installed in the POLANO are currently under development. As the polarizer, a cylindrical 3He spin filter (HeSF) based on the spin-exchange optical pumping (SEOP) technique will be used to polarize neutrons in the wide energy range. During the experiments, the HeSF is operated in the on-beam mode to maintain 3He polarization The primary phase of the construction will be completed by 2014 with beam commissioning scheduled in 2015

  19. Results of calculations on the beam deflection due to the 1 MHz chopper for the Kaon factory

    International Nuclear Information System (INIS)

    Deflection of 1 GeV/c H- beam bunches to be eliminated by the 1 MHz chopper, for the proposed Kaon factory at TRIUMF, will be provided by an electric field between a set of deflector plates. Deflection rise time is a function of beam transit time through the deflector plates and the rise time of the stored voltage pulse. This paper presents the results of time-domain mathematical simulations to assess the relationship between the above quantities: the results of these simulations allow an accurate determination of the required rise-time of the stored voltage pulse. The representation of the deflector plates is modified so that linear displacement of the beam, as well as angular deflection, may be assessed. Simulations have also been performed to assess the attenuating effect of the deflector plates upon both angular deflection and linear displacement of the H- beam caused by voltage ripple. A measured voltage pulse is simulated as driving the deflector plates, and beam deflection is predicted. (Author) 12 refs., 3 figs

  20. Some general reflections on open-quotes long pulseclose quotes neutron sources

    International Nuclear Information System (INIS)

    A long pulse spallation neutron source (LPSS) having about 20 times more time average thermal flux than its short pulse counterpart (SPSS) at the same proton beam power and featuring a pronounced time structure not available on CW sources (CWNS) of equal time average flux can in principle host instruments typical for both classes of facilities. While the need for additional choppers introduces some restrictions on inverted time of flight techniques typical for SPSS and high incident neutron energies are not easier to use on LPSS than on CWNS, taking advantage of the pulsed nature of the neutron flux can enhance significantly the performance of direct time of flight instruments and of crystal spectrometers or diffractometers. In the paper some of the options are reviewed in a general manner and criteria are discussed which can be used to optimize the performance enhancement

  1. A new guide concept for a homogenous neutron beam without direct line of sight

    Energy Technology Data Exchange (ETDEWEB)

    Cussen, Leo D., E-mail: ldc_0@yahoo.com.au [Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); ESS Design Update Programme (Germany); Krist, Thomas, E-mail: krist@helmholtz-berlin.de [Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Lieutenant, Klaus, E-mail: klaus.lieutenant@helmholtz-berlin.de [Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); ESS Design Update Programme (Germany)

    2015-03-21

    Neutron guide tubes are used to transport neutrons efficiently from the source to distant instruments. Ballistic neutron guides, which have an expanding section in the beginning and a contracting section in the end, reduce the total number of reflections and improve transport efficiency in long guides. Long pulse spallation sources like the European Spallation Source require very long guides. Challenges in ballistic guide design are imposed by the need for small virtual sources and the prevention of direct line of sight to the source, because both tend to produce inhomogeneous beam distributions, and the latter reduces transmission for short wavelengths. This article describes a novel ballistic guide design based on elliptic profiles. It incorporates a carefully positioned and angled kink to avoid line of sight to the source and a narrow point to position a chopper. This design reduces the number of reflections in long guides and improves transmission, especially at short wavelengths, compared to other solutions avoiding a direct line of sight.

  2. New developments of TOF neutron diffraction at the IBR-2 pulsed reactor

    International Nuclear Information System (INIS)

    Development of high-resolution RTOF Fourier technique for powder neutron diffraction studies is being continued at the IBR-2 pulsed reactor in Dubna. Besides some technical improvements in the operating HRFD instrument, a new dedicated instrument, Fourier Strain Diffractometer (FSD), for investigation of residual stresses in bulk materials has been constructed at IBR-2 in 1999. With a new HRFD Fourier chopper smaller than 10 μs TOF contribution in a resolution function was obtained in the experiment with perfect Si single crystal. A series of diffraction experiments with the beams from a new methane cold neutron moderator installed at the IBR-2 in 1999 is discussed. A comparison with the results obtained with the conventional water comb-like moderator shows that for various types of experiments, which are performed at HRFD and DN-2 diffractometers, the methane cold neutron source provides better conditions. (author)

  3. Neutron Radiography

    OpenAIRE

    Reddy, A. R.; Rao, M. V. N.

    2012-01-01

    The field of neutron radiography with special reference to isotopic neutron radiography has been reviewed. Different components viz., sources, collimators, imaging systems are described. Various designs of neutron radiography facilities, their relative merits and demerits , the appropriateness of each design depending on the object to be radiographed, and economics of each technique are also dealt. The applications of neutron radiography are also briefly presented.

  4. Neutron reflectometry

    International Nuclear Information System (INIS)

    Neutron research where reflection, refraction, and interference play an essential role is generally referred to as 'neutron optics'. The neutron wavelength, the scattering length density and the magnetic properties of the material determine the critical angle for total reflection. The theoretical background of neutron reflection, experimental methods and the interpretation of reflection data are presented. (K.A.)

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

    Science.gov (United States)

    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.

  6. Ultracold-neutron infrastructure for the PNPI/ILL neutron EDM experiment

    International Nuclear Information System (INIS)

    A PNPI/ILL experiment to measure the neutron electric dipole moment (EDM) is currently being prepared at the facility PF2 for ultracold neutrons (UCN) at the Institut Laue-Langevin in Grenoble. To enable an improvement of sensitivity, one of PF2's beam positions has been equipped with new components for UCN transport, polarization and beam characterization, comprised of a superconducting solenoid-polarizer with magnetic field 4 T, a neutron guide system with diameter 136 mm prepared in replica technology, and a novel beam chopper for time-of-flight analysis. The whole EDM apparatus is set up on a non-magnetic platform. The total flux of polarized UCN with velocities less than 6.8 m/s along the guide axis is 1.5x105 n/s, corresponding to a flux density of 103 cm-2 s-1. The density of polarized UCN at the experimental position is about 5 cm-3, which shall lead to an EDM measurement with a counting statistical accuracy of 1.5x10-26 ecm during 200 days of operation at PF2.

  7. Application of digital signal-processing technique to delayed-neutron yield measurements on thermal-neutron induced fission of 237Np

    International Nuclear Information System (INIS)

    The measurement procedure based on the continuous thermal-neutron beam modulation with a mechanical chopper was developed for delayed-neutron yield measurement of the thermal-neutron induced fission of 237Np. The idea of the procedure is similar to that which is widely used in modern communications for the nonauthorized data access prevention. The data is modulated with predefined pattern before transmission to the public network and only the recipient that has the modulation pattern is able to demodulate it upon reception. For the thermal-neutron induced reaction applications, the thermal-neutron beam modulation pattern was used to demodulate the measured delayed-neutron intensity signals on the detector output resulting in nonzero output only for the detector signals correlated with the beam modulation pattern. A comparison of the method with the conventional measurement procedure was provided, and it was demonstrated that the cross-correlation procedure has special features making it superior over the conventional one when the measured value difference from the background is extremely small. Due to strong sensitivity of measurement procedure on the modulation pattern of the neutron beam, one can implement the modulation pattern of specific shape to separate the effect of the thermal part of the beam from the higher energy one in the most confident way in a particular experiment

  8. Neutron Skins and Neutron Stars

    OpenAIRE

    Piekarewicz, J

    2013-01-01

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

  9. CIAE 600 kV ns pulse neutron generator

    International Nuclear Information System (INIS)

    The overall composition of CIAE 600 kV ns Pulse Neutron Generator (CPNG) are introduced, and its characteristic, main technological performance and application were also given. CPNG consists of high voltage power supply with highest output voltage 600 kV, direct current 15 mA, stability and ripple ≤0.1%, 2214 mm x 1604 mm x 1504 mm stainless steel high voltage electrode, built in head equipment uniform field accelerating tube, ns pulsed installation, turbomolecular vacuum pump system and drift pipes at 0 degree and 45 degree. Its characteristics are: (1) high current beam; (2) high current beam ns pulsed installation made use of low energy for chopper and high energy for buncher; (3) compactly laid out and simple in structure

  10. Neutron scattering investigation of magnetic excitations at high energy transfers

    International Nuclear Information System (INIS)

    With the advance of pulsed spallation neutron sources, neutron scattering investigation of elementary excitations in magnetic materials can now be extended to energies up to several hundreds of MeV. We have measured, using chopper spectrometers and time-of-flight techniques, the magnetic response functions of a series of d and f transition metals and compounds over a wide range of energy and momentum transfer. In PrO2, UO2, BaPrO3 and CeB6 we observed crystal-field transitions between the magnetic ground state and the excited levels in the energy range from 40 to 260 MeV. In materials exhibiting spin-fluctuation or mixed-valent character such as Ce 74Th 26, on the other hand, no sharp crystal-field lines but a broadened quasielastic magnetic peak was observed. The line width of the quasielastic component is thought to be connected to the spin-fluctuation energy of the 4f electrons. The significance of the neutron scattering results in relation to the ground state level structure of the magnetic ions and the spin-dynamics of the f electrons is discussed. Recently, in a study of the spin-wave excitations in itinerant magnetic systems, we have extended the spin-wave measurements in ferromagnetic iron up to about 160 MeV. Neutron scattering data at high energy transfers are of particular interest because they provide direct comparison with recent theories of itinerant magnetism. 26 references, 7 figures

  11. Neutron Radiography

    Directory of Open Access Journals (Sweden)

    A. R. Reddy

    1982-07-01

    Full Text Available The field of neutron radiography with special reference to isotopic neutron radiography has been reviewed. Different components viz., sources, collimators, imaging systems are described. Various designs of neutron radiography facilities, their relative merits and demerits , the appropriateness of each design depending on the object to be radiographed, and economics of each technique are also dealt. The applications of neutron radiography are also briefly presented.

  12. A 55-dB SNDR, 2.2-mW double chopper-stabilized analog front-end for a thermopile sensor

    International Nuclear Information System (INIS)

    A double chopper-stabilized analog front-end (DCS-AFE) circuit for a thermopile sensor is presented, which includes a closed-loop front-end amplifier and a 2nd-order 1 bit quantization sigma—delta modulator. The amplifier with a closed-loop structure ensures the gain stability against the temperature. Moreover, by adopting the chopper-stabilized technique both for the amplifier and 2nd-order 1-bit quantization sigma—delta modulator, the low-frequency 1/f noise and offset is reduced and high resolution is achieved. The AFE is implemented in the SMIC 0.18 μm 1P6M CMOS process. The measurement results show that in a 3.3 V power supply, 1 Hz input frequency and 3KHz clock frequency, the peak signal-to-noise and distortion ratio (SNDR) is 55.4 dB, the effective number of bits (ENOB) is 8.92 bit, and in the range of −20 to 85 degrees, the detection resolution is 0.2 degree. (semiconductor integrated circuits)

  13. The Neutron Spectrum in a Uranium Tube

    International Nuclear Information System (INIS)

    A series of experimental and theoretical investigations on neutron spectra in lattice cells has been started at the reactor R1. This report gives the results from the first one of these cells - one with a tube of natural -uranium surrounded by heavy water. In the measurements the cell was placed in the central, vertical channel of the reactor. The neutron spectrum from a lead scatterer in the uranium tube - outer diameter 49.2 mm, inner diameter 28.3 mm - was measured with a fast chopper in the energy region 0.01 to 100 eV. Subsidiary measurements indicated that the spectrum in the beam from the lead piece corresponds to the spectrum of the angular flux integrated over all angles. This correspondence is important for the interpretation of the experimental data. The thermal part of the spectrum was found to deviate significantly from a Maxwellian. However, the deviation is not very large, and one could use a Maxwellian, at least to give a rough idea of the hardness of the spectrum. For the present tube the temperature of this Maxwellian was estimated as 90 to 100 deg C above the moderator temperature (33 deg C). In the joining region the rise of the spectrum towards the thermal part is slower than for the cell boundary spectrum, measured earlier. In the epithermal region the limited resolution of the chopper has affected the measurements at the energies of the uranium resonances. However, the shape of the spectrum on the flanks of the first resonance in 238U (6.68 eV) has been obtained accurately. In the theoretical treatment the THERMOS code with a free gas scattering model has been used. The energy region was 3.06 - 0.00025 eV. The agreement with the measurements is good for the thermal part - possibly the theoretical spectrum is a little softer than the experimental one. In the joining region the results from THERMOS are comparatively high - probably due to the scattering model used

  14. Proceedings of the workshop on 'possible scientific view from new neutron spectroscopy opportunities in J-PARC'

    International Nuclear Information System (INIS)

    At Materials and Life Science Experimental Facility (MLF) at J-PARC, three chopper spectrometers, AMATERAS, 4SEASONS and HRC have been constructed and a near-backscattering spectrometer, DNA is under construction. By combination of a high intensity neutron source at MLF and advanced technologies equipped, these spectrometers are expected to open new possibilities in scientific research using neutron inelastic and quasi-elastic scattering methods. In such circumstances, the workshop entitled 'Possible Scientific View from New Neutron Spectroscopy Opportunities in J-PARC' was held on 8-9, July 2009 at Ibaraki Quantum Beam Research Center. The purpose of the workshop is to discuss the recent hot research topics and possible investigations utilizing the novel spectrometers at MLF in the wide range of the research field such as solid state physics, chemistry, material science, softmatter science, biology and industrial applications. This report includes abstracts and materials of the presentations in the workshop. (author)

  15. Neutron Capture and Neutron Halos

    OpenAIRE

    A.Mengoni; Otsuka, T; Nakamura, T.(International Center for Elementary Particle Physics and Department of Physics, The University of Tokyo, Tokyo, Japan); Ishihara, M.

    1996-01-01

    The connection between the neutron halo observed in light neutron rich nuclei and the neutron radiative capture process is outlined. We show how nuclear structure information such as spectroscopic factors and external components of the radial wave function of loosely bound states can be derived from the neutron capture cross section. The link between the direct radiative capture and the Coulomb dissociation process is elucidated.

  16. Attempt to visualize cavitation in nozzle chamber of diesel engine by neutron radiography

    International Nuclear Information System (INIS)

    Preliminary experiment using neutron radiography was attempted on visualization of cavitation (= cold boiling) of fuel flow inside the metallic nozzle chamber of diesel engine. Fuel ejection from a diesel-engine nozzle is dependent on the cavitation conditions in fuel flow, subjective to pressure change, were studied using a cooled CCD camera with electric shutter open and with the help of a synchronous chopper for neutron beams which enables to observe visualized flow at 0.5 mm width nozzle chamber, 1 mm diameter sac chamber, and 0.2 mm diameter nozzle hole in a diesel engine. Each images could be obtained with short exposure time from 100 μs to 1 mx. (S. Ohno)

  17. Performance of the advanced cold neutron source and optics upgrades at the NIST Research Reactor

    International Nuclear Information System (INIS)

    On March 6, 2002, the NIST Research Reactor resumed routine operation following a six-month shutdown for facility upgrades and maintenance. During the shutdown, the original liquid hydrogen cold neutron source was removed, and the advanced cold source was installed. An optical filter was installed on one of the neutron guides, NG-3, replacing a crystal filter for the 30-m SANS instrument and the guide used between the chopper disks of the Disk Chopper time-of-flight Spectrometer (DCS) installed on NG-4 has been recently reconfigured. Additional improvements in the neutron optics of various instruments are being made. The advanced liquid hydrogen cold neutron source performs as expected, nearly doubling the flux available to most instruments. The measured gains range from about 1.4 at 2 A, to over a factor of two at 15 A. Also as expected, the heat load in the new source increased to 1200 watts, but the previously existing refrigerator has easily accommodated the increase. With intensity gains of a factor of two in the important long wavelength region of the spectrum, the advanced cold source significantly enhances the measurement capability of the cold neutron scattering instrumentation at NIST. The optical filter on NG-3 is also very successful; the 30-m SANS has an additional gain of two at 17 A. A system of refracting lenses and prisms near the SANS sample position has made possible measurements at low Q (0.0005 A-1) that were previously not feasible. The DCS has also seen additional intensity gain factors in excess of two for the majority of experiments and at short neutron wavelengths the gains exceed three. In addition, two new triple axis spectrometers will feature double-focusing monochromators in order to exploit the full size of the available thermal and cold neutron beam tubes. The success of the advanced cold source and enhanced neutron optics contributed to the recognition of the NIST Center for Neutron Research as 'the premiere neutron scattering

  18. Measurements of the Thermal Neutron Spectrum in the Core of the Forschungsreaktor Frankfurt (FRF)

    International Nuclear Information System (INIS)

    The thermal neutron spectrum in the core of the FRF was measured using a neutron chopper facility. The FRF is a homogeneous water-boiler reactor (Type L54F, Atomics International). Its fuel solution mainly consists of uranyl sulphate (400 g UO2SO4/I, enriched in U235 to 20%), water and sulphuric acid (concentration 0.4 molar). The absorption cross-section per proton of the solution is 1.85 b. To extract neutrons from the core, a zirconium scatterer was placed in the central beam tube (through-hole) of the reactor. The scatterer could be positioned at various distances from the core centre. The measured spectra can be described in good approximation by a Maxwellian distribution. The neutron temperatures determined from the spectra are higher than those reported in literature for moderating water systems poisoned by an equivalent amount of absorber. The higher neutron temperature may be explained by assuming an increased effective mass of the. moderating protons in the fuel solution. In the joining region between thermal and epithermal energies the spectra differ from those reported for pure water. The cut-off energy of the epithermal spectrum is found to be about En = 5 kTn, Tn being the neutron temperature of the Maxwellian spectrum. In the course of these measurements the influence of the zirconium scatterer on the neutron spectrum in the extracted beam was investigated. The total neutron cross-section of zirconium in the energy range between 0. 002 and 0.1 eV was measured. The results show that only at neutron energies En > 0.02 eV is the total neutron cross-section of zirconium nearly independent of neutron energy. Below this value coherent scattering in zirconium strongly affects the spectral distribution in the scattered beam. (author)

  19. Terahertz antenna electronic chopper

    Energy Technology Data Exchange (ETDEWEB)

    Sterczewski, L. A., E-mail: lukasz.sterczewski@pwr.edu.pl; Grzelczak, M. P.; Plinski, E. F. [Department of Electronics, Wroclaw University of Technology, 27 Wybrzeze Wyspianskiego St., 50-370 Wroclaw (Poland)

    2016-01-15

    In this paper, we present an electronic circuit used to bias a photoconductive antenna that generates terahertz radiation. The working principles and the design process for the device are discussed in detail. The noise and shape of the wave measurements for a built device are considered. Furthermore, their impact on a terahertz pulse and its spectra is also examined. The proposed implementation is simple to build, robust and offers a real improvement over THz instrumentation due to the frequency tuning. Additionally, it provides for galvanic isolation and ESD protection.

  20. Neutron sources

    International Nuclear Information System (INIS)

    As neutron scattering experiments have grown more and more demanding with respect to resolution and quality, it became more and more necessary to include the neutron source itself in the design of an experimental setup. In this sense the generic representation of a neutron scattering arrangement includes the primary neutron source and the associated spectrum shifter (or moderator). In fact, the design of a modern neutron source will start from a set of users requirements and will proceed 'inwards' through a selection of the moderators (spectrum shifters) to the primary source best suited to meet these often conflicting needs. This paper aims at explaining the options source designers have to match the neutron source performance to the users' demands. (author)

  1. Neutron detector

    Science.gov (United States)

    Stephan, Andrew C.; Jardret; Vincent D.

    2011-04-05

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

  2. The multipurpose time-of-flight neutron reflectometer 'Platypus' at Australia's OPAL reactor

    International Nuclear Information System (INIS)

    In this manuscript we describe the major components of the Platypus time-of-flight neutron reflectometer at the 20 MW OPAL reactor in Sydney, Australia. Platypus is a multipurpose spectrometer for the characterisation of solid thin films, materials adsorbed at the solid-liquid interface and free-liquid surfaces. It also has the capacity to study magnetic thin films using spin-polarised neutrons. Platypus utilises a white neutron beam (λ=2-20 A) that is pulsed using boron-coated disc chopper pairs; thus providing the capacity to tailor the wavelength resolution of the pulses to suit the system under investigation. Supermirror optical components are used to focus, deflect or spin-polarise the broad bandwidth neutron beams, and typical incident spectra are presented for each configuration. A series of neutron reflectivity datasets are presented, indicating the quality and flexibility of this spectrometer. Minimum reflectivity values of -7 are observed; while maximum thickness values of 325 nm have been measured for single-component films and 483 nm for a multilayer system. Off-specular measurements have also been made to investigate in-plane features as opposed to those normal to the sample surface. Finally, the first published studies conducted using the Platypus time-of-flight neutron reflectometer are presented.

  3. Atmospheric neutrons

    International Nuclear Information System (INIS)

    Additional calibrations of the University of California double-scatter neutron and additional analysis corrections lead to the slightly changed neutron fluxes reported here. The theoretical angular distributions of Merker (1975) are in general agreement with our experimental fluxes but do not give the peaks for vertical upward and downward moving neutrons. The theoretical neutron escape current J2/sub pi/ (Merker, 1972; Armstrong et al., 1973) is in agreement with the experimental values from 10 to 100 MeV. Our experimental fluxes agree with those of the Kanbach et al. (1974) in the overlap region from 70 to 100 MeV

  4. Neutron dosimetry

    International Nuclear Information System (INIS)

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq 241 Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s-1 and 0,5 μSv s-1. A calibrated 50 nSv s-1 thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the 241 Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold 241 Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,α) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kVpp cm-1, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46± 0,09) 104 tracks cm-2 mSv-1 for thermal neutrons, (9±3) 102 tracks cm-2 mSV-1 for intermediate neutrons and (26±4) tracks cm-2 mSv-1 for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990's ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is sufficiently sensitive to thermal and intermediate neutrons but fast neutron monitoring ar radiological protection level

  5. Micromegas neutron beam monitor neutronics.

    Science.gov (United States)

    Stephan, Andrew C; Miller, Laurence F

    2005-01-01

    The Micromegas is a type of ionising radiation detector that consists of a gas chamber sandwiched between two parallel plate electrodes, with the gas chamber divided by a Frisch grid into drift and amplification gaps. Investigators have applied it to a number of different applications, such as charged particle, X-ray and neutron detection. A Micromegas device has been tested as a neutron beam monitor at CERN and is expected to be used for that purpose at the Spallation Neutron Source (SNS) under construction in Oak Ridge, TN. For the Micromegas to function effectively as neutron beam monitor, it should cause minimal disruption to the neutron beam in question. Specifically, it should scatter as few neutrons as possible and avoid neutron absorption when it does not contribute to generating useful information concerning the neutron beam. Here, we present the results of Monte Carlo calculations of the effect of different types of wall materials and detector gases on neutron beams and suggest methods for minimising disruption to the beam. PMID:16381746

  6. Neutron dosimetry; Dosimetria de neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Fratin, Luciano

    1993-12-31

    A neutron irradiation facility was designed and built in order to establish a procedure for calibrating neutron monitors and dosemeters. A 185 GBq {sup 241} Am Be source of known is used as a reference source. The irradiation facility using this source in the air provides neutron dose rates between 9 nSv s{sup -1} and 0,5 {sup {mu}}Sv s{sup -1}. A calibrated 50 nSv s{sup -1} thermal neutron field is obtained by using a specially designed paraffin block in conjunction with the {sup 241} Am Be source. A Bonner multisphere spectrometer was calibrated, using a procedure based on three methods proposed by international standards. The unfold {sup 241} Am Be neutron spectrum was determined from the Bonner spheres data and resulted in a good agreement with expected values for fluence rate, dose rate and mean energy. A dosimetric system based on the electrochemical etching of CR-39 was developed for personal dosimetry. The dosemeter badge using a (n,{alpha}) converter, the etching chamber and high frequency power supply were designed and built specially for this project. The electrochemical etching (ECE) parameters used were: a 6N KOH solution, 59 deg C, 20 kV{sub pp} cm{sup -1}, 2,0 kHz, 3 hours of ECE for thermal and intermediate neutrons and 6 hours for fast neutrons. The calibration factors for thermal, intermediate and fast neutrons were determined for this personal dosemeter. The sensitivities determined for the developed dosimetric system were (1,46{+-} 0,09) 10{sup 4} tracks cm{sup -2} mSv{sup -1} for thermal neutrons, (9{+-}3) 10{sup 2} tracks cm{sup -2} mSV{sup -1} for intermediate neutrons and (26{+-}4) tracks cm{sup -2} mSv{sup -1} for fast neutrons. The lower and upper limits of detection were respectively 0,002 mSv and 0,6 mSv for thermal neutrons, 0,04 mSv and 8 mSv for intermediate neutrons and 1 mSv and 12 mSv for fast neutrons. In view of the 1990`s ICRP recommendations, it is possible to conclude that the personal dosemeter described in this work is

  7. Neutron gun

    International Nuclear Information System (INIS)

    The neutron gun combines a new core ion source of the cold type based on X-ray ionization and new cold type of neutron source working with core ion generation. The neutrons are formed from the impact of core ions on the negatively charged anode. Based on a new conversion function, the function of the positive anode becomes analogous to the beta-unstable decomposition of a neutron. A core ion and neutron amplifier in the sense of amplifying the number is derived from the beta-unstable neutron decomposition, in order to raise the output of a gun in pulsed operation by using the number amplification in the intervals between the pulses. The method of construction is simple and cheap, the equipment has purely linear acceleration or operation with circular acceleration with linear pre-acceleration as an alternative. Purely linear operation should be sufficient for medical applications, e.g. for neutron photography to replay X-ray photography and particularly for neutron scalpels in the surgical treatment of tumours. (orig./HP)

  8. Neutron transport

    International Nuclear Information System (INIS)

    This bibliographical note presents a reference book which addresses the study of neutron transport in matter, the study of conditions for a chain reaction and the study of modifications of matter composition due to nuclear reactions. This book presents the main nuclear data, their measurement, assessment and processing, and the spallation. It proposes an overview of methods applied for the study of neutron transport: basic equations and their derived forms, deterministic methods and Monte Carlo method of resolution of the Boltzmann equation, methods of resolution of generalized Bateman equations, methods of time resolution of space kinetics coupled equations. It presents the main calculation codes, discusses the qualification and experimental aspects, and gives an overview of neutron transport applications: neutron transport calculation of reactors, neutron transport coupled with other disciplines, physics of fuel cycle, criticality

  9. Neutron tubes

    Science.gov (United States)

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

    2008-03-11

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

  10. Neutron radiography

    International Nuclear Information System (INIS)

    This introduction is addressed to an audience active in diverse forms of neutron source applications but not directly familiar with neutron radiography. Neutron radiography is, of course, similar to, and complementary to, radiography using x-rays. However, neutrons, being sensitive to the nuclear properties of materials, provide information fundamentally different from x-rays. For example, neutrons can penetrate many dense metals such as uranium, lead, bismuth or steel, and can reveal details of internal hydrogenous components: explosives, lubricants and gaskets. For nuclear fuel inspection neutron radiography offers the ability to penetrate dense uranium-238 and contrast the isotopes U-235 or Pu-239 and also offers the ability to discriminate against unwanted interference from gamma radiation. In addition to advantages in industrial applications, there are special situations in fields such as medical diagnostics, dentistry, agriculture and forensic science. Comprehensive accounts of applications in the field can be found in the proceedings of the world conferences on neutron radiography: USA (1981), FRANCE (1986). A third conference in this series is scheduled for May 1989 in Japan

  11. Indigenous design and development of multiPSD array for time of flight neutron spectrometer

    Science.gov (United States)

    Desai, Shraddha S.; Devan, Shylaja; Das, Amrita; Patkar, S. M.; Rao, Mala N.

    2016-05-01

    Time of Flight neutron Spectrometer for inelastic neutron scattering studies is being commissioned at Dhruva reactor. Neutron pulse tagging is carried out using the Fermi chopper. Scattered neutrons at maximum possible scattered solid angle are needed to be detected along with the time information at detector. Precise and efficient detection system is essential for measurement of spatial and temporal distribution. Detection area is optimized to cover an angle of 70° in horizontal direction and 23° in vertical direction. Position sensitive detectors (PSDs) are designed with judicial use of precious 3He gas and a few PSDs with BF3 gas as suitable alternative for 3He gas. An array of vertically arranged 1 m long, 50 PSDs, covers the arc length of 2.5 m and detection area 2.5 m2. The design of the BF3 PSDs is supported by investigations on the gas purity, fill gas pressure, drift region, drift field and neutron absorption in cathode wall. Design details and performance of the PSDs are presented in the paper.

  12. Neutron radiography

    International Nuclear Information System (INIS)

    The digital processing of the neutron radiography images gives the possibility for data quantification. In this case an exact relation between the measured neutron attenuation and the real macroscopic attenuation coefficient for every point of the sample is required. The assumption that the attenuation of the neutron beam through the sample is exponential is valid only in an ideal case where a monochromatic beam, non scattering sample and non background contribution are assumed. In the real case these conditions are not fulfilled and in dependence on the sample material we have more or less deviation from the exponential attenuation law. Because of the high scattering cross-sections of hydrogen (σs=80.26 barn) for thermal neutrons, the problem with the scattered neutrons at quantitative radiography investigations of hydrogenous materials (as PE, Oil, H2O, etc) is not trivial. For these strong scattering materials the neutron beam attenuation is no longer exponential and a dependence of the macroscopic attenuation coefficient on the material thickness and on the distance between the sample and the detector appears. When quantitative radiography (2 D) or tomography investigations (3 D) are performed, some image correction procedures for a description of the scattering effect are required. This thesis presents a method that can be used to enhance the neutron radiography image for objects with high scattering materials like hydrogen, carbon and other light materials. This method uses the Monte Carlo code, MCNP5, to simulate the neutron radiography process and get the flux distribution for each pixel of the image and determine the scattered neutrons distribution that causes the image blur and then subtract it from the initial image to improve its quality.

  13. Neutron tomography

    International Nuclear Information System (INIS)

    In this paper a survey is given of recent developments in selected areas of neutron tomography, within the context of several applications Argonne is involved in, including high penetration of reactor-fuel bundles in thick containers (involving TREAT and NRAD facilities), dual-energy hydrogen imaging (performed at IPNS), dynamic coarse-resolution emission tomography of rector fuel under test (a proposed modification to the TREAT hodoscope), and an associated-particle system that uses neutron flight-time to electronically collimate transmitted neutrons and to tomographically image nuclides identified by reaction gamma-rays

  14. Neutron scattering

    International Nuclear Information System (INIS)

    This report contains the text of 16 lectures given at the Summer School and the report on a panel discussion entitled ''the relative merits and complementarities of x-rays, synchrotron radiation, steady- and pulsed neutron sources''. figs., tabs., refs

  15. Piezonuclear Neutrons

    CERN Document Server

    Cardone, Fabio; Petrucci, Andrea

    2008-01-01

    We report the results of neutron measurements carried out during the application of ultrasounds to a solution containing only stable elements like Iron and Chlorine, without any other radioactive source of any kind. These measurements, carried out by CR39 detectors and a Boron TriFouride electronic detector, evidenced the emission of neutron pulses. These pulses stand well above the electronic noise and the background of the laboratory where the measurements were carried out.

  16. Neutron Scattering

    International Nuclear Information System (INIS)

    The neutron probe is a standard tool for measuring soil water content. This article provides an overview of the underlying theory, describes the methodology for its calibration and use, discusses example applications, and identifies the safety issues. Soil water makes land-based life possible by satisfying plant water requirements, serving as a medium for nutrient movement to plant roots and nutrient cycling, and controlling the fate and transport of contaminants in the soil environment. Therefore, a successful understanding of the dynamics of plant growth, nutrient cycling, and contaminant behavior in the soil requires knowledge of the soil water content as well as its spatial and temporal variability. After more than 50 years, neutron probes remain the most reliable tool available for field monitoring of soil water content. Neutron probes provide integrated measurements over relatively large volumes of soil and, with proper access, allow for repeated sampling of the subsurface at the same locations. The limitations of neutron probes include costly and time-consuming manual operation, lack of data automation, and costly regulatory requirements. As more non-radioactive systems for soil water monitoring are developed to provide automated profiling capabilities, neutron-probe usage will likely decrease. Until then, neutron probes will continue to be a standard for reliable measurements of field water contents in soils around the globe

  17. FOREWORD: Neutron metrology Neutron metrology

    Science.gov (United States)

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

    2011-12-01

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

  18. A Vector Switching Method of Multiphase Chopper in Superconducting Magnetic Energy Storage Systems%超导磁储能系统用多相斩波器矢量切换控制方法

    Institute of Scientific and Technical Information of China (English)

    施啸寒; 王少荣; 左文平

    2013-01-01

    在高功率超导磁储能装置(superconducting magnetic energy storage,SMES)中,电压源型功率调节系统首先利用多相斩波器将超导磁体电流转化成稳定的直流电压,再利用后级电压源型变流器(voltage source converter,VSC)与交流%In the high power superconducting magnetic energy storage (SMES) device, the voltage source converter (VSC) based power conditioning system (PCS) first converts the current of the superconducting magnetic to a stable DC voltage with the help of a multiphase chopper, and then utilizes a VSC to communicate power with the AC system. However, in the situation when the power communication between SMES and the grid changes too fast, a multiphase chopper with traditional current-self-shared PI controller has some problems such as the DC voltage deviation and transient current unbalance. The DC voltage deviation will further exert adverse effects on the control accuracy and speed of the succeeding VSC. To overcome these problems, this paper deduces the switching-function model of the multiphase chopper, and proposes a vector-switching-based control method using the deduced model. This method utilizes the hysteresis to switch the control vector to realize the DC voltage control, at the same time utilizes the redundant switch combinations of a control vector to realize the current sharing. Simulation shows that the proposed method can eliminate the DC voltage deviation when the power communication suddenly changing, and thus, provides a favorable condition for the fast and accurate control of the VSC. Besides, the proposed method can also realize current-sharing of the multiphase chopper in most of the situations, and therefore ensure the long-term operation of the system reliably.

  19. The multipurpose time-of-flight neutron reflectometer 'Platypus' at Australia's OPAL reactor

    Energy Technology Data Exchange (ETDEWEB)

    James, M., E-mail: mja@ansto.gov.a [Bragg Institute, Building 87, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); School of Chemistry, University of New South Wales, Kensington, NSW 2052 (Australia); Nelson, A.; Holt, S.A.; Saerbeck, T.; Hamilton, W.A.; Klose, F. [Bragg Institute, Building 87, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia)

    2011-03-11

    In this manuscript we describe the major components of the Platypus time-of-flight neutron reflectometer at the 20 MW OPAL reactor in Sydney, Australia. Platypus is a multipurpose spectrometer for the characterisation of solid thin films, materials adsorbed at the solid-liquid interface and free-liquid surfaces. It also has the capacity to study magnetic thin films using spin-polarised neutrons. Platypus utilises a white neutron beam ({lambda}=2-20 A) that is pulsed using boron-coated disc chopper pairs; thus providing the capacity to tailor the wavelength resolution of the pulses to suit the system under investigation. Supermirror optical components are used to focus, deflect or spin-polarise the broad bandwidth neutron beams, and typical incident spectra are presented for each configuration. A series of neutron reflectivity datasets are presented, indicating the quality and flexibility of this spectrometer. Minimum reflectivity values of <10{sup -7} are observed; while maximum thickness values of 325 nm have been measured for single-component films and 483 nm for a multilayer system. Off-specular measurements have also been made to investigate in-plane features as opposed to those normal to the sample surface. Finally, the first published studies conducted using the Platypus time-of-flight neutron reflectometer are presented.

  20. Neutron Spectra in Subcritical Graphite- and Beryllia-Moderated Assemblies

    International Nuclear Information System (INIS)

    A number of subcritical graphite- and beryllia-moderated assemblies fuelled with plutonium and highly enriched uranium plates have been constructed with ratios of moderator atoms to fissile atoms as low as 300. As part of a general study of these small under moderated systems in which fission takes place predominantly at energies above 0.1 eV , time-of-flight measurements have been carried out using a neutron chopper having a resolution of 4 μs/m. This adequately resolves the spectrum in the thermal region and in the region of the resonance in 239Pu at 0.296 eV. Calculations have been carried out using a multigroup transport code with scattering matrices for graphite and beryllia based on data obtained from the Chalk River scattering law experiments. A correct weighting over the experimental source area of the vector flux in the direction of the extracted beam produces a spectrum which can be compared directly with the observed spectrum. It has been found that in the region 0.4 to 1.0 eV the experimental spectra have fewer neutrons than are predicted and this is particularly noticeable in the BeO-moderated assemblies. The factors which could give rise to the discrepancy are discussed but it has not been possible to attribute it to any particular one. (author)

  1. Neutron Repulsion

    CERN Document Server

    Manuel, Oliver K

    2011-01-01

    Earth is connected gravitationally, magnetically and electrically to its heat source - a neutron star that is obscured from view by waste products in the photosphere. Neutron repulsion is like the hot filament in an incandescent light bulb. Excited neutrons are emitted from the solar core and decay into hydrogen that glows in the photosphere like a frosted light bulb. Neutron repulsion was recognized in nuclear rest mass data in 2000 as the overlooked source of energy, the keystone of an arch that locked together these puzzling space-age observations: 1.) Excess 136Xe accompanied primordial helium in the stellar debris that formed the solar system (Fig. 1); 2.) The Sun formed on the supernova core (Fig. 2); 3.) Waste products from the core pass through an iron-rich mantle, selectively carrying lighter elements and lighter isotopes of each element into the photosphere (Figs. 3-4); and 4.) Neutron repulsion powers the Sun and sustains life (Figs. 5-7). Together these findings offer a framework for understanding...

  2. neutron radiography

    International Nuclear Information System (INIS)

    Neutron radiography (or radiology) is a diverse filed that uses neutrons of various energies, subthermal, thermal, epithermal or fast in either steady state or pulsed mode to examine objects for industrial, medical, or other purposes, both microscopic and macroscopic. The applications include engineering design, biological studies, nondestructive inspection and materials evaluation. In the past decade, over 100 different centers in some 30 countries have published reports of pioneering activities using reactors, accelerators and isotopic neutron sources. While film transparency and electronic video are most common imaging methods for static or in motion objects respectively, there are other important data gathering techniques, including track etch, digital gauging and computed tomography. A survey of the world-wide progress shows the field to be gaining steadily in its diversity, its sophistication and its importance. (author)

  3. The Transmission of Thermal Neutrons through a Large Single Crystal of Bismuth at Liquid Nitrogen Temperature

    International Nuclear Information System (INIS)

    The transmission of a bismuth filter, at the temperature of liquid nitrogen, was measured using a slow chopper and a flight path of 5.4 m. The filter is made of two ''single crystals'', each 20 cm long and 5 cm in diameter. According to specification of the manufacturer each ''single crystal'' consists of maximum three of four columns of single crystals. In the energy range from 25 - 10 meV, the transmitted intensity is about 30% of the expected value. In the range from 5 meV to lower energies, the transmission is of the order of 60 - 70%. A cadmium ratio of 5000 was measured. The actual cadmium ratio may still be higher since the measurement was not made with a really fast neutron collimator. In spite of manv coherent dips in the transmission curve, the performance of the filter is rather satisfactory for thhe production of a thermal neutron beam that is predominantly free from fast neutrons and γ-rays. Possible applications of a filtered neutron beam are discussed. (author)

  4. Neutron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Heger, G. [Rheinisch-Westfaelische Technische Hochschule Aachen, Inst. fuer Kristallographie, Aachen (Germany)

    1996-12-31

    X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (author) 15 figs., 1 tab., 10 refs.

  5. QDG1-30型秸秆枝丫切碎机试验分析%Experimental Analysis of QDG1-30 Straw and Branch Chopper

    Institute of Scientific and Technical Information of China (English)

    吴兆迁; 牛晓华; 才丽华

    2015-01-01

    QDG1-30型秸秆枝丫切碎机是我国用于人工林采伐、森林抚育剩余物等木质原料及各种农作物秸秆碎化处理的专用设备,该机采用鼓式切碎装置,结构简单、实用,生产效率高。性能和生产试验的结果显示:与QGP3-30型枝丫切碎机相比,生产率提高了24%以上,作业成本降低了22%以上,具有显著的经济效益。%QDG1-30 Straw and Branch Chopper is special equipment intended for chopping treatment of wooden residuals from plantation felling and forest tending and straws of various kinds in the rural area. This machine has a drum type chopping device, featuring a simple structure and high production efficiency, with the performance and production test result showing that this machine has significantly improved operation efficiency and production efficiency, up more than 24%, compared with QDG3-30, with operation cost falling by more than 22%, showing significant economic benefits.

  6. Neutron reflectometer

    International Nuclear Information System (INIS)

    The neutron reflectometer is the most powerful and nondestructive tool to analyze the surface and buried interfaces in the layered films. Such films often have a close relation to the functional devices. Structural information in the vicinity of the interfaces is a key parameter in the field of the nanoscale science. (author)

  7. Neutron radiography

    International Nuclear Information System (INIS)

    Principles of the method, complementarity with X or gamma rays, neutron energy, detection and applications on irradiated materials and for the industrial quality control are exposed. Examples of applications in pyrotechnics, plastics, fuels, lubricants, metallurgy are given. Techniques developed by the CEA for its own needs or for industry and description of facilities in the nuclear centers are reviewed

  8. Variation of the Binary-to-Ternary Fission Ratio for U235 in the Thermal-Neutron-Energy Region

    International Nuclear Information System (INIS)

    The slow chopper installed at BRI was used to make an accurate determination of the binary-to-ternary fission ratio for U235 in the neutron-energy range from 0.005 eV to 0.2 eV. Large gold-silicon suríace-barrier detectors are used for the consecutive measurement of long-range α-particles (absorber in) and fission fragments (absorber out). The time analysis is done with a 100-channel time-of-flight analyser. A one-metre flight-path and a rotor speed of 50 rev/s is used. The B/T ratio was also measured with a high statistical accuracy (about 1%) in intense beams with well-defined neutron spectra, i.e. a ''cold neutron'' beam, a beam extracted from a thermal column and a beam of 0.3-eV neutrons produced by crystal diffraction. The B/T ratio exhibits a small and smooth variation in the energy range considered. This effect seems to be correlated with measurements of some other fission parameters in the same neutron-energy range. (author)

  9. Methods for absorbing neutrons

    Science.gov (United States)

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

    2012-07-24

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

  10. Recent Advances in Neutron Physics

    Science.gov (United States)

    Feshbach, Herman; Sheldon, Eric

    1977-01-01

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

  11. Neutron rich nuclei and neutron stars

    OpenAIRE

    Horowitz, C. J.

    2013-01-01

    The PREX experiment at Jefferson Laboratory measures the neutron radius of 208Pb with parity violating electron scattering in a way that is free from most strong interaction uncertainties. The 208Pb radius has important implications for neutron rich matter and the structure of neutron stars. We present first PREX results, describe future plans, and discuss a follow on measurement of the neutron radius of 48Ca. We review radio and X-ray observations of neutron star masses and radii. These cons...

  12. Neutron dosimetry

    International Nuclear Information System (INIS)

    It is the object of the present invention to provide a method of measuring neutron radiation which eliminates the use of powders as dosimeter target materials and reduces the requirement for repetitive weighing of dosimeters, for expensive radioisotopes as dosimeter target material, and for dosimeter housings (in many cases). The invention described is a method of measuring neutron radiation within a nuclear reactor consisting of placing one or more extruded sintered oxide wires comprising a dosimeter target oxide within the reactor and measuring the radioactivity induced in the wires by neutron radiation. These oxide wires consist of a dilution containing at least 0.1% by weight of the dosimeter target oxide in a diluent oxide. The diluent oxide is selected from a group consisting of Al2O3 and BeO. Almost any metal oxide may be used as a target oxide. The wires may be encapsulated within a co-extruded housing. These mixed oxide wires have been found to be sufficiently uniform for quantitative analyses. (JTA)

  13. Neutron scattering

    International Nuclear Information System (INIS)

    The annual report on hand gives an overview of the research work carried out in the Laboratory for Neutron Scattering (LNS) of the ETH Zuerich in 1990. Using the method of neutron scattering, it is possible to examine in detail the static and dynamic properties of the condensed material. In accordance with the multidisciplined character of the method, the LNS has for years maintained a system of intensive co-operation with numerous institutes in the areas of biology, chemistry, solid-state physics, crystallography and materials research. In 1990 over 100 scientists from more than 40 research groups both at home and abroad took part in the experiments. It was again a pleasure to see the number of graduate students present, who were studying for a doctorate and who could be introduced into the neutron scattering during their stay at the LNS and thus were in the position to touch on central ways of looking at a problem in their dissertation using this modern experimental method of solid-state research. In addition to the numerous and interesting ways of formulating the questions to explain the structure, nowadays the scientific programme increasingly includes particularly topical studies in connection with high temperature-supraconductors and materials research

  14. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron scattering in contemporary research, neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  15. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, symmetry of crystals, nanostructures investigated by small-angle neutron scattering, structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic neutron scattering, strongly correlated electrons, polymer dynamics, applications of neutron scattering. (HSI)

  16. Development of a pulsed uniform supersonic gas expansion system based on an aerodynamic chopper for gas phase reaction kinetic studies at ultra-low temperatures.

    Science.gov (United States)

    Jiménez, E; Ballesteros, B; Canosa, A; Townsend, T M; Maigler, F J; Napal, V; Rowe, B R; Albaladejo, J

    2015-04-01

    A detailed description of a new pulsed supersonic uniform gas expansion system is presented together with the experimental validation of the setup by applying the CRESU (French acronym for Cinétique de Réaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique to the gas-phase reaction of OH radicals with 1-butene at ca. 23 K and 0.63 millibars of helium (carrier gas). The carrier gas flow, containing negligible mixing ratios of OH-precursor and 1-butene, is expanded from a high pressure reservoir (337 millibars) to a low pressure region (0.63 millibars) through a convergent-divergent nozzle (Laval type). The novelty of this experimental setup is that the uniform supersonic flow is pulsed by means of a Teflon-coated aerodynamic chopper provided with two symmetrical apertures. Under these operational conditions, the designed Laval nozzle achieves a temperature of (22.4 ± 1.4) K in the gas jet. The spatial characterization of the temperature and the total gas density within the pulsed uniform supersonic flow has also been performed by both aerodynamical and spectroscopic methods. The gas consumption with this technique is considerably reduced with respect to a continuous CRESU system. The kinetics of the OH+1-butene reaction was investigated by the pulsed laser photolysis/laser induced fluorescence technique. The rotation speed of the disk is temporally synchronized with the exit of the photolysis and the probe lasers. The rate coefficient (k(OH)) for the reaction under investigation was then obtained and compared with the only available data at this temperature. PMID:25933898

  17. FSY30型林木枝丫切碎机试验分析%Experimental Analysis of FSY30 Tree Branch Chopper

    Institute of Scientific and Technical Information of China (English)

    牛晓华; 吴兆迁; 樊涛; 王晓军

    2011-01-01

    FSY30型林木枝丫切碎机是林区林木剩余物碎化处理的专用设备,该机采用圆盘式切碎装置,结构简单实用,解决了我国现有林木剩余物碎化处理设备野外作业性能差、切削效率低和原料适应面窄等问题,为我国林区人工林迹地整理更新、抚育和采伐等作业产生的各种林木剩余物碎化处理提供了适用的设备。该机性能和生产试验结果表明:其作业效率比现有机型提高20%以上,作业成本减少15%以上,具有显著的经济效益和一定的生态效益。%FSY30 tree branch chopper is a machine specially used for chopping forest residuals in forest areas. The machine uses a disc type chopping device, with a simple and practical structure, and has solved the problems with poor Operation performance in the field, low chopping efficiency and narrow adaptive scope of raw materials of the existing equipment and provided proper equipment for regeneration, tending and harvesting operations in the plantation area in China. Performance and production experiments show that the operation efficiency of the machine has improved by 20% over the current machine types and the operation cost has reduced by15%, with noticeable economic and social benefits.

  18. 四象限斩波控制直流调速系统的技术研究%Technology Research of DC Speeding for Four-quadrant Chopper Control System

    Institute of Scientific and Technical Information of China (English)

    李一鸣; 荣军; 邓斌; 易学良

    2016-01-01

    DC motor has wide speeding range and high precision, and it has very important application for the industrial fields required to speeding and braking performance. Firstly, the mathematical model of DC motor is introduces, and the three methods of its speed regulation are given, and the method of changing the armature voltage is chosen as the method of its speed regulation. Then the working principle of DC speeding system for four-quadrant chopper control is analyzed in detail, andthemodels is established based on Matlab/Simulink, and the simulation results are given. Through the analysis of simulation results, the simulation results are consistent with the theoretical analysis, and the correctness of theoretical analysis and modeling simulation of DC speed control system for the four-quadrant chopper control is verified.Finally, the advantages of DC speed control system for the four-quadrant chopper control are highlighted by comparing the simulation results with the other two kinds of chopper DC drive system.%直流电动机具有调速范围广以及调速精度高的特点,因此在要求调速和制动性能高的工业领域有非常广泛的应用。本文首先介绍了直流电机的数学模型,给出其调速的三种方法,最后选择改变电枢电压作为其调速的方法。然后详细分析了四象限斩波控制直流调速的工作原理,并且在Matlab/Simulink中建立了四象限斩波控制直流调速模型,并给出了其仿真结果。仿真结果与理论分析完全一致,验证了四象限斩波控制直流调速系统理论分析和建模仿真的正确性。最后通过与其它两种斩波直流调速系统仿真结果比较,显示了四象限斩波控制直流调速系统的优越性。

  19. Spallation Neutron Source (SNS)

    Data.gov (United States)

    Federal Laboratory Consortium — The SNS at Oak Ridge National Laboratory is a next-generation spallation neutron source for neutron scattering that is currently the most powerful neutron source in...

  20. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  1. REFRACTIVE NEUTRON LENS

    OpenAIRE

    Petrov, P. V.; Kolchevsky, N.N.

    2013-01-01

    Compound concave refractive lenses are used for focusing neutron beam. Investigations of spectral and focusing properties of a refractive neutron lens are presented. Resolution of the imaging system on the base of refractive neutron lenses depends on material properties and parameters of neutron source. Model of refractive neutron lens are proposed. Results of calculation diffraction resolution and focal depth of refractive neutron lens are discussed.

  2. Neutron Capture Nucleosynthesis

    OpenAIRE

    Kiss, Miklos

    2016-01-01

    Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these resu...

  3. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, neutron properties and elastic scattering, correlation functions measured by scattering experiments, symmetry of crystals, applications of neutron scattering, polarized-neutron scattering and polarization analysis, structural analysis, magnetic and lattice excitation studied by inelastic neutron scattering, macromolecules and self-assembly, dynamics of macromolecules, correlated electrons in complex transition-metal oxides, surfaces, interfaces, and thin films investigated by neutron reflectometry, nanomagnetism. (HSI)

  4. Neutron Therapy Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The Neutron Therapy Facility provides a moderate intensity, broad energy spectrum neutron beam that can be used for short term irradiations for radiobiology (cells)...

  5. Gravitational and Aharonov-Bohm phases in neutron interferometry

    International Nuclear Information System (INIS)

    This thesis describes two experiments with the interferometer for very-cold-neutrons (VCN) at the Institut Laue-Langevin in Grenoble, France. This interferometer operates with neutrons that are 40 m/s slow and uses micro-fabricated phase gratings as beam-splitters. The first experiment is a demonstration of the scalar neutron Aharonov-Bohm (AB) effect, which is the neutron analogue of the electrostatic AB effect for electrons. Aharonov and Bohm (1959) proposed this latter effect together with the magnetic AB effect to clarify the significance of electromagnetic potentials in quantum mechanics. The experiment described here focuses at for the first time simultaneously demonstrating the two essential operational signatures of all AB-type effects: their nondispersivity, i.e. wavelength independence, and the fact that they are not locally observable in a simply connected space-time. In this thesis it will be shown, as was already pointed out by Zeilinger (1984, 1986), that the neutron analogue also has both signatures and thus can be used to demonstrate them. In the experiment the paths of the neutron interferometer are enclosed by two anti-parallel solenoids. When, determined by a chopper, the neutron is completely inside the homogeneous field region of the coils the field is turned on and off, resulting in a phase shift due to the difference in magnetic energy. High-visibility fringes were observed even for phase shifts exceeding the limit given by the coherence length, which is a clear demonstration of the wavelength independence of this effect. Because the interferometer has spatially separated beams and uses unpolarized neutrons the effect of the magnetic field on the neutron is not locally observable in either of the interferometer arms. The second experiment is what is commonly known as a COW-experiment. In these experiments a neutron interferometer is tilted around its optical axis, resulting in a phase shift due to the difference in gravitational potential

  6. Neutron source for Neutron Capture Synovectomy

    International Nuclear Information System (INIS)

    Monte Carlo calculations were performed to obtain a thermal neutron field from a 239PuBe neutron source inside a cylindrical heterogeneous moderators for Neutron Capture Synovectomy. Studied moderators were light water and heavy water, graphite and heavy water, lucite and polyethylene and heavy water. The neutron spectrum of polyethylene and heavy water moderator was used to determine neutron spectra inside a knee model. In this model the elemental composition of synovium and synovial liquid was assumed like blood. Kerma factors for synovium and synovial liquid were calculated to compare with water Kerma factors, in this calculations the synovium was loaded with two different concentrations of Boron

  7. Quality assessment of in-pile guides by energy resolved neutron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Fuezi, Janos [Research Institute for Solid State Physics and Optics, H-1525 Budapest (Hungary); Transilvania University, R-2200 Brasov (Romania)], E-mail: fuzi@szfki.hu

    2008-02-11

    The energy resolved pinhole-imaging method can be applied for surveying the condition of neutron beam extraction systems without the need to remove them. The only condition is the access to a position where direct view of the source is available. Generally this is possible at some stages of the guide system installation or during replacement of first out of pile guide sections. Some facilities have removable sections downstream of the main shutters where the proposed measurement can be performed. The measurement is based on position sensitive neutron detection in time of flight regime. In case of continuous sources, a chopper is required, while in case of pulsed sources the time frame is provided by the source period. The proposed method can be considered an in situ reflectometry experiment. To each pixel of a reflection region corresponds a pixel of the direct view. The ratio of the neutron counts in the image pixel with respect to the corresponding direct pixel gives the reflectivity of the involved mirror plate at the angle which can be determined from the experiment geometry and at the wavelength which results from the flight length and time. The measurement gives an average reflectivity over the mirror surfaces viewed through the given pinhole position and finally the transfer function of the investigated guide sections. The accuracy of the results is affected by the alignment accuracy of the guide sections because the reflection angles are determined with respect to the theoretical positions of the mirror surfaces. As an example, the results obtained at a 100 mm high and 25 mm wide cold neutron beamline at the Budapest Neutron Centre are presented.

  8. Toward a new polyethylene scattering law determined using inelastic neutron scattering

    International Nuclear Information System (INIS)

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S(Q,E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for ambient temperatures (∼300K), and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 294 K which are used to improve the scattering law for HDPE. We review some of the past HDPE scattering laws, describe the experimental methods, and compare computations using these models to the measured S(Q,E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the one phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work. -- Highlights: ► Polyethylene at 5 K and 300 K is measured using inelastic neutron scattering (INS). ► Measurements conducted at the Wide Angular-Range Chopper Spectrometer at SNS. ► Several models for Polyethylene are compared to measurements. ► Improvements to existing models for the polyethylene scattering law are suggested. ► INS is shown to be highly valuable tool for scattering law development

  9. Neutron dosimetry - A review

    International Nuclear Information System (INIS)

    This review summarizes information on the following subjects: (1) physical processes of importance in neutron dosimetry; (2) biological effects of neutrons; (3) neutron sources; and (4) instruments and methods used in neutron dosimetry. Also, possible improvements in dosimetry instrumentation are outlined and discussed. (author)

  10. Borner Ball Neutron Detector

    Science.gov (United States)

    2002-01-01

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

  11. Superfluid neutron stars

    OpenAIRE

    Langlois, David

    2001-01-01

    Neutron stars are believed to contain (neutron and proton) superfluids. I will give a summary of a macroscopic description of the interior of neutron stars, in a formulation which is general relativistic. I will also present recent results on the oscillations of neutron stars, with superfluidity explicitly taken into account, which leads in particular to the existence of a new class of modes.

  12. Neutrostriction in Neutron stars

    OpenAIRE

    Ignatovich, V. K.

    2003-01-01

    It is demonstrated that not only gravity, but also neutrostriction forces due to optical potential created by coherent elastic neutron-neutron scattering can hold a neutron star together. The latter forces can be stronger than gravitational ones. The effect of these forces on mass, radius and structure of the neutron star is estimated.

  13. Neutron scattering. Lectures

    International Nuclear Information System (INIS)

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  14. Neutron scattering. Lectures

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: Neutron sources, symmetry of crystals, diffraction, nanostructures investigated by small-angle neutron scattering, the structure of macromolecules, spin dependent and magnetic scattering, structural analysis, neutron reflectometry, magnetic nanostructures, inelastic scattering, strongly correlated electrons, dynamics of macromolecules, applications of neutron scattering. (HSI)

  15. Neutron standard data

    International Nuclear Information System (INIS)

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

  16. Neutron Capture Nucleosynthesis

    CERN Document Server

    Kiss, Miklos

    2016-01-01

    Heavy elements (beyond iron) are formed in neutron capture nucleosynthesis processes. We have proposed a simple unified model to investigate the neutron capture nucleosynthesis in arbitrary neutron density environment. We have also investigated what neutron density is required to reproduce the measured abundance of nuclei assuming equilibrium processes. We found both of these that the medium neutron density has a particularly important role at neutron capture nucleosynthesis. About these results most of the nuclei can formed at medium neutron capture density environment e.g. in some kind of AGB stars. Besides these observations our model is capable to use educational purpose.

  17. Neutrons in cancer therapy

    Science.gov (United States)

    Allen, Barry J.

    1995-03-01

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

  18. High energy neutron detector

    Energy Technology Data Exchange (ETDEWEB)

    Wiegand, C.

    1948-04-27

    It is the purpose of this paper to describe a neutron detector suitable for monitoring a flux of neutrons whose energy is greater than about 50 MeV. Detection of the neutrons is accomplished by their ability to induce fission in heavy elements. Kelly and Wiegand studied the neutron fission of Bi, Pb, Ti, Hg, Au, and Pt at various neutron energies and the presently described counter is an application of this work.

  19. Imaging with Scattered Neutrons

    CERN Document Server

    Ballhausen, H; Gähler, R; Trapp, M; Van Overberghe, A

    2006-01-01

    We describe a novel experimental technique for neutron imaging with scattered neutrons. These scattered neutrons are of interest for condensed matter physics, because they permit to reveal the local distribution of incoherent and coherent scattering within a sample. In contrast to standard attenuation based imaging, scattered neutron imaging distinguishes between the scattering cross section and the total attenuation cross section including absorption. First successful low-noise millimeter-resolution images by scattered neutron radiography and tomography are presented.

  20. Pulsed neutron sources for epithermal neutrons

    International Nuclear Information System (INIS)

    It is shown how accelerator based neutron sources, giving a fast neutron pulse of short duration compared to the neutron moderation time, promise to open up a new field of epithermal neutron scattering. The three principal methods of fast neutron production: electrons, protons and fission boosters will be compared. Pulsed reactors are less suitable for epithermal neutrons and will only be briefly mentioned. The design principle of the target producing fast neutrons, the moderator and reflector to slow them down to epithermal energies, and the cell with its beam tubes and shielding will all be described with examples taken from the new Harwell electron linac to be commissioned in 1978. A general comparison of pulsed neutron performance with reactors is fraught with difficulties but has been attempted. Calculation of the new pulsed source fluxes and pulse widths is now being performed but we have taken the practical course of basing all comparisons on extrapolations from measurements on the old 1958 Harwell electron linac. Comparisons for time-of-flight and crystal monochromator experiments show reactors to be at their best at long wavelengths, at coarse resolution, and for experiments needing a specific incident wavelength. Even existing pulsed sources are shown to compete with the high flux reactors in experiments where the hot neutron flux and the time-of-flight methods can be best exploited. The sources under construction can open a new field of inelastic neutron scattering based on energy transfer up to an electron volt and beyond

  1. Neutron Scintillators for Downscattered Neutron Imaging

    International Nuclear Information System (INIS)

    Images of neutron emission from Inertial Confinement Fusion (ICF) (D,T) targets reveal the internal structure of the target during the fusion burn. 14-MeV neutrons provide images which show the size and shape of the region where (D,T) fusion is most intense. Images based on ''downscattered'' neutrons with energies from 5 to 10 MeV emphasize the distribution of deuterium and tritium fuel within the compressed target. The downscattered images are difficult to record because the lower energy neutrons are detected with less efficiency than the much more intense pulse of 14-MeV neutrons which precedes them at the detector. The success of downscattered neutron imaging will depend on the scintillation decay times and the sensitivities to lower-energy neutrons of the scintillator materials that are used in the detectors. A time-correlated photon counting system measured the decay of neutron-induced scintillation for times as long as several hundred ns. Accelerators at the University of California, Berkeley, and the Lawrence Livermore National Laboratory provided stable 14-MeV neutron sources for the measurements. Measurements of scintillator decay characteristics indicate that some commercially available scintillators should be suitable for recording both 14-MeV and downscattered neutron images of compressed ICF targets

  2. Weapons Neutron Research Facility (WNR)

    Data.gov (United States)

    Federal Laboratory Consortium — The Weapons Neutron Research Facility (WNR) provides neutron and proton beams for basic, applied, and defense-related research. Neutron beams with energies ranging...

  3. Chopper-stabilized phase detector

    Science.gov (United States)

    Hopkins, P. M.

    1978-01-01

    Phase-detector circuit for binary-tracking loops and other binary-data acquisition systems minimizes effects of drift, gain imbalance, and voltage offset in detector circuitry. Input signal passes simultaneously through two channels where it is mixed with early and late codes that are alternately switched between channels. Code switching is synchronized with polarity switching of detector output of each channel so that each channel uses each detector for half time. Net result is that dc offset errors are canceled, and effect of gain imbalance is simply change in sensitivity.

  4. Neutron scattering in Er2-x Yx Ti2 O7

    Science.gov (United States)

    Gaudet, Jonathan; Hallas, Alannah; Maharaj, Dalini; Kermarrec, Edwin; Butch, Nicholas P.; Dabowska, Hanna; Gaulin, Bruce

    E r2 T i2 O7 (ETO) is a strong candidate for ground state selection via the order by disorder mechanism. A Ψ2 magnetic ground state appears below TN=1.2 K, where Ψ2 and Ψ3 are the two basis states of the irreducible representation Γ5. No sample dependance has been observed in the thermodynamics properties of ETO at low temperature, and in particular on its phase transition to long range magnetic order. ETO's ordered Neel state has been shown to be robust even to a relatively high level of magnetic dilution, as occurs with non-magnetic Y3+ substitution of Er3+ .However, recently two theoretical studies have predicted that ETO's Ψ2 ground state should be unstable to formation of the Ψ3 state, in the presence of such disorder. To explore this possibility,we grew single crystals of Er2 - xYx Ti2O7 (EYTO) with x = 0,0.2 and 0.4 and performed a systematic inelastic neutron scattering studies using the Disk Chopper time-of-flight spectrometer (DCS) at the National Institute of Standards and Technology (NIST). We will show elastic and inelastic neutron scattering at low temperatures and as a a function of applied magnetic field for all three samples and discuss the role of such quenched disorder on the spin dynamics of EYTO.

  5. Momentum density of hcp and liquid helium-4 by inelastic neutron scattering

    International Nuclear Information System (INIS)

    A measurement of the momentum density in hcp and liquid 4He by inelastic neutron scattering is reported. Using the Low Resolution Medium Energy Chopper Spectrometer at the Intense Pulsed Neutron Source at Argonne National Laboratory, momentum transfers in the range 12 to 22.5 A-1 were attained. At these momentum transfers, the momentum density of the sample is related to the dynamic structure factor by the impulse approximation. The measured momentum distribution is Gaussian and the kinetic energy is larger than proposed by existing theories. Data were taken on two solid samples, the first was a 19.45 cm3/mole hcp solid, the second was 18.20 cm3/ mole; both solid samples were maintained at 1.70 K during data collection. Data were also taken on a liquid sample with a molar volume of 18.20 cm3/mole at 4.00 K. At 1.70 K the two solid samples are essentially in their ground states so that the measurement is of the ground state momentum density. The liquid sample was included to see if the difference between the liquid and solid momentum density at the same molar volume was observable

  6. Neutron in biology

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-11-01

    Neutron in biology can provide an experimental method of directly locating relationship of proteins and DNA. However, there are relatively few experimental study of such objects since it takes a lot of time to collect a sufficient number of Bragg reflections and inelastic spectra due to the low flux of neutron illuminating the sample. Since a next generation neutron source of JAERI will be 5MW spallation neutron source and its effective neutron flux will be 10{sup 2} to 10{sup 3} times higher than the one of JRR-3M, neutron in biology will open a completely new world for structural biology. (author)

  7. Layered semiconductor neutron detectors

    Science.gov (United States)

    Mao, Samuel S; Perry, Dale L

    2013-12-10

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

  8. Reactor neutron dosimetry

    International Nuclear Information System (INIS)

    An analysis of requirements and possibilities for experimental neutron spectrum determination during the reactor pressure vessel surveil lance programme is given. Fast neutron spectrum and neutron dose rate were measured in the Fast neutron irradiation facility of our TRIGA reactor. It was shown that the facility can be used for calibration of neutron dosimeters and for irradiation of samples sensitive to neutron radiation. The investigation of the unfolding algorithm ITER was continued. Based on this investigations are two specialized unfolding program packages ITERAD and ITERGS written this year. They are able to unfold data from activation detectors and NaI(T1) gamma spectrometer respectively

  9. Pulsed neutron porosity logging

    International Nuclear Information System (INIS)

    A borehole logging tool employing a pulsed neutron source and a pair of spaced-apart epithermal neutron detectors is lowered into a borehole traversing a subsurface formation. The formation is irradiated with bursts of fast neutrons and the epithermal neutrons returning to the borehole as a result of such irradiation are detected by the pair of epithermal neutrons detectors. These detected epithermal neutrons are both time resolved and time integrated during their epithermal dieaway spectrum to provide indications of lithology independent porosity and lithology dependent porosity respectively. 6 refs

  10. Broadband Neutron Interferometer

    CERN Document Server

    Pushin, Dmitry A; Hussey, Dan; Miao, Houxun; Arif, Muhammad; Cory, David G; Huber, Michael G; Jacobson, David; LaManna, Jacob; Parker, Joseph D; Shinohara, Taken; Ueno, Wakana; Wen, Han

    2016-01-01

    We demonstrate a two phase-grating, multi-beam neutron interferometer by using a modified Ronchi setup in a far-field regime. The functionality of the interferometer is based on the universal \\moire effect that was recently implemented for X-ray phase-contrast imaging in the far-field regime. Interference fringes were achieved with monochromatic, bichromatic, and polychromatic neutron beams; for both continuous and pulsed beams. This far-field neutron interferometry allows for the utilization of the full neutron flux for precise measurements of potential gradients, and expands neutron phase-contrast imaging techniques to more intense polycromatic neutron beams.

  11. Neutron scattering and spallation neutron sources

    International Nuclear Information System (INIS)

    Neutron scattering as a probe of microscopic structure and dynamics is a powerful tool for research in a wide variety of fields, and an accelerator-based spallation neutron source can supply high flux pulses for neutron scattering. The characteristics of neutron scattering, the principle and development of spallation neutron sources, and their advantages in multidisciplinary applications are summarized. In the proposed project of the Chinese Spallation Neutron Source the target station will consist of a piece-stacked tungsten target, a Be/Fe reflector and an Fe/heavy concrete bio-protected shelter. The pulsed neutron flux will be up to 2.4 x 1016 n/cm2/s under a nuclear power of 100 kW. Five neutron scattering instruments--a high flux powder diffractometer, a high resolution powder diffractometer, small angle diffractometer, multi-functional reflectometer and direct geometry inelastic spectrometer, will be constructed as the first step to cover most neutron scattering applications. (authors)

  12. Neutron-antineutron oscillation in neutron stars

    International Nuclear Information System (INIS)

    It is investigated if the neutron-antineutron oscillation might affect the stability of a neutron star. Because of the very high density inside a neutron star the possibility is reduced drastically and it is shown that only a small percentage of the neutrons are capable of becoming antineutrons and thus are annihilated. Fixing the lower limit (referred to the vacuum) of τn,antin as 106 s, it is obtained that only 1021 erg/s are produced by this mechanism, so the thermodynamical equilibrium of the star is unaffected

  13. Magnetic model for Mn2La2 developed from spectroscopic studies with inelastic neutron scattering and frequency-domain Fourier-transform THz EPR

    International Nuclear Information System (INIS)

    Molecular nanomagnets which contain several magnetic centers with a large single-ion magnetic anisotropy are of general interest, because they could lead to interesting phenomena such as single-molecule magnet (SMM) behavior. We performed spectroscopic experiments on Mn2La2 using inelastic neutron scattering at the direct time-of-flight disc chopper spectrometer IN5 at ILL and the newly developed frequency-domain Fourier-transform THz EPR at BESSY. Based on the experimental results a magnetic model has been developed. It is discussed why no SMM behavior was observed, even though Mn2La2 exhibits a remarkably high energy barrier of about 37 K for spin relaxation. Furthermore our results can be applied to analogous clusters, with the diamagnetic LaIII ions replaced by magnetic rare earth ions.

  14. Magnetic model for Mn{sub 2}La{sub 2} developed from spectroscopic studies with inelastic neutron scattering and frequency-domain Fourier-transform THz EPR

    Energy Technology Data Exchange (ETDEWEB)

    Milazzo, R.; Nehrkorn, J.; Stuiber, S.; Waldmann, O. [Physikalisches Institut, Universitaet Freiburg (Germany); Akhtar, M.N.; Lan, Y.; Powell, A.K. [Institut fuer Anorganische Chemie, Universitaet Karlsruhe, KIT (Germany); Mutka, H. [Institut Laue Langevin, Grenoble (France); Dreiser, J. [Swiss Light Source, Paul Scherrer Institut (Switzerland); Schnegg, A. [Helmholtz-Zentrum Berlin, Institut fuer Silizium-Photovoltaik (Germany); Holldack, K. [Helmholtz-Zentrum Berlin, Institut fuer Synchrotonstrahlung (Germany)

    2011-07-01

    Molecular nanomagnets which contain several magnetic centers with a large single-ion magnetic anisotropy are of general interest, because they could lead to interesting phenomena such as single-molecule magnet (SMM) behavior. We performed spectroscopic experiments on Mn{sub 2}La{sub 2} using inelastic neutron scattering at the direct time-of-flight disc chopper spectrometer IN5 at ILL and the newly developed frequency-domain Fourier-transform THz EPR at BESSY. Based on the experimental results a magnetic model has been developed. It is discussed why no SMM behavior was observed, even though Mn{sub 2}La{sub 2} exhibits a remarkably high energy barrier of about 37 K for spin relaxation. Furthermore our results can be applied to analogous clusters, with the diamagnetic La{sup I}II ions replaced by magnetic rare earth ions.

  15. Neutron anatomy

    International Nuclear Information System (INIS)

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

  16. Neutron anatomy

    Energy Technology Data Exchange (ETDEWEB)

    Bacon, G.E. [Univ. of Sheffield (United Kingdom)

    1994-12-31

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

  17. Advances in neutron polarisation analysis capability for material sciences research on OPAL instruments

    International Nuclear Information System (INIS)

    We are opening to the user community a new material sciences research capability of using neutron polarization analysis on the instruments in the OPAL reactor at the Australian Nuclear Science and Technology (ANSTO). Polarised neutron scattering is a powerful technique that can cleanly separates the magnetic scattering of magnetic moments and magnetic excitations from the nuclear scattering of the chemical structure and structural dynamics. We can identify the location, strength, and direction of the magnetic moments to atomic resolution and the strength and polarization of magnetic excitations with this technique. In addition, it allows us to separate the structural signal and the hydrogen background signal in hydrogen-rich materials which has long been a challenge in studying organic materials with neutrons. At ANSTO, polarisation analysis has previously been available on the reflectometer PLATYPUS for thin film and multilayer studies. The operation of a 3He polarising station has now provided this capability for more instruments. We have now measured the magnetic structure of multiferroic single-crystals and giant-magnetocaloric powder samples on the WOMBAT diffractometer and the TAIPAN triple-axis spectrometer. We have also measured the polarization and location of magnon excitation in a multiferroic single-crystal on the TAIPAN triple-axis spectrometer. These capabilities are now opened to users in the research community. Commissioning tests have been done for polarised off-specular scattering capability on PLATYPUS to study lateral magnetic surface structure. It will soon be followed by polarization analysis on the cold neutron chopper spectrometer PELICAN for magnetic excitation measurements and polarised SANS on QUOKKA for magnetic nanostructured material and hydrogen-rich material studies. This presentation will highlight the material sciences measurements done using this new capability and present the main characteristics of this technique.

  18. Determination of efficiencies, loss mechanisms, and performance degradation factors in chopper controlled dc vehical motors. Section 2: The time dependent finite element modeling of the electromagnetic field in electrical machines: Methods and applications. Ph.D. Thesis

    Science.gov (United States)

    Hamilton, H. B.; Strangas, E.

    1980-01-01

    The time dependent solution of the magnetic field is introduced as a method for accounting for the variation, in time, of the machine parameters in predicting and analyzing the performance of the electrical machines. The method of time dependent finite element was used in combination with an also time dependent construction of a grid for the air gap region. The Maxwell stress tensor was used to calculate the airgap torque from the magnetic vector potential distribution. Incremental inductances were defined and calculated as functions of time, depending on eddy currents and saturation. The currents in all the machine circuits were calculated in the time domain based on these inductances, which were continuously updated. The method was applied to a chopper controlled DC series motor used for electric vehicle drive, and to a salient pole sychronous motor with damper bars. Simulation results were compared to experimentally obtained ones.

  19. Sources of ultracold neutrons

    International Nuclear Information System (INIS)

    The results of comparative experimental investigations to study ultracold neutron yields from different neutron moderator-converters are presented. The installation is described which is based on a WWR-K reactor once-through beam hole. The neutron yields were measured using Al, Mg, ZrHsub(1.9), H2O and H2 neutron converters at 80 and 300 K. For H2 converters pressure dependences of the neutron yield were also measured in the 0.1-1.5 atm. pressure range. Among solid neutron converters the ZrHsub(1.9) one possesses the highest ultracold neutron yield, whereas among all the converters tested the best performance was shown by the frozen water one, the ultracold neutron count with the proportional He3 counter being about 500ssup(-1)

  20. Neutron radiation capture

    International Nuclear Information System (INIS)

    For all stable and experimentally studied radionuclides evaluated data are presented on cross sections of thermal neutrons, on resonance integrals and medium neutron cross sections with energy of 30 KeV. Refs, figs and tabs

  1. Neutron color image intensifier

    International Nuclear Information System (INIS)

    Neutron radiography is expanding from the conventional reactor based imaging to the imaging by accelerator based pulsed neutron source. Among them, an expectation for image intensifier technology is increasing especially for video rate dynamic image detection or time dependent imaging in a pulsed neutron source. Based on the X-ray color image intensifier technology, Toshiba has developed neutron color image intensifiers as a powerful imaging tool for dynamic and time dependent neutron radiographics. In this paper, the construction and the feature of the developed neutron color image intensifier and some examples of neutron images are presented. I would be grateful if this paper helps for wide application of neutron color image intensifiers. (author)

  2. Properties of neutron sources

    International Nuclear Information System (INIS)

    The Conference presentations were divided into sessions devoted to the following topics: white neutron sources, primarily pulsed (6 papers); fast neutron fields (5 papers); Californium-252 prompt fission neutron spectra (14 papers); monoenergetic sources and filtered beams (11 papers); 14 MeV neutron sources (10 papers); selected special application (one paper); and a general interest session (4 papers). Individual abstracts were prepared separately for the papers

  3. Imaging with Scattered Neutrons

    OpenAIRE

    Ballhausen, H.; Abele, H.; Gaehler, R.; Trapp, M; Van Overberghe, A.

    2006-01-01

    We describe a novel experimental technique for neutron imaging with scattered neutrons. These scattered neutrons are of interest for condensed matter physics, because they permit to reveal the local distribution of incoherent and coherent scattering within a sample. In contrast to standard attenuation based imaging, scattered neutron imaging distinguishes between the scattering cross section and the total attenuation cross section including absorption. First successful low-noise millimeter-re...

  4. Isotopic neutron sources for neutron activation analysis

    International Nuclear Information System (INIS)

    This User's Manual is an attempt to provide for teaching and training purposes, a series of well thought out demonstrative experiments in neutron activation analysis based on the utilization of an isotopic neutron source. In some cases, these ideas can be applied to solve practical analytical problems. 19 refs, figs and tabs

  5. Fundamental neutron physics

    International Nuclear Information System (INIS)

    Fundamental physics experiments of merit can be conducted at the proposed intense neutron sources. Areas of interest include: neutron particle properties, neutron wave properties, and fundamental physics utilizing reactor produced γ-rays. Such experiments require intense, full-time utilization of a beam station for periods ranging from several months to a year or more

  6. Neutron radiography with cyclotron

    International Nuclear Information System (INIS)

    The technique using thermal neutrons was demanded because of its inspection ability to show hydrogeneous material such as plastics, water, explosives or composite materials and irradiated nuclear fuel capsules. This paper describes some experimental results and applications in neutron radiography by the use of several small cyclotrons producing neutrons by Be(p,n) reaction. (author)

  7. Thermal neutron beamline monitor

    International Nuclear Information System (INIS)

    A detector has been developed which has characteristics that make it suitable for use as a neutron beamline monitor on the Spallation Neutron Source. Efficiency has been reduced to 10-4, pulse pair resolution is 50 nSecs and it presents minimal obstruction to the neutron beam. (author)

  8. International Neutron Radiography Newsletter

    DEFF Research Database (Denmark)

    Domanus, Joseph Czeslaw

    1986-01-01

    At the First World Conference on Neutron Radiography i t was decided to continue the "Neutron Radiography Newsletter", published previously by J.P. Barton, as the "International Neutron Radiography Newsletter" (INRNL), with J.C. Doraanus as editor. The British Journal of Non-Destructive Testing...

  9. Neutrons in medicine

    International Nuclear Information System (INIS)

    The potential advantages for the treatment of solid human tumours with high LET radiation are outlined. Two different kinds of neutron radio-therapy a) boron capture therapy with slow neutrons and b) fast neutron radiotherapy are briefly reviewed together with some clinical results for the latter. Radiotherapy with charged nuclear particles is also mentioned. (UK)

  10. Polarized Neutron Scattering

    OpenAIRE

    Roessli, B.; Böni, P.

    2000-01-01

    The technique of polarized neutron scattering is reviewed with emphasis on applications. Many examples of the usefulness of the method in various fields of physics are given like the determination of spin density maps, measurement of complex magnetic structures with spherical neutron polarimetry, inelastic neutron scattering and separation of coherent and incoherent scattering with help of the generalized XYZ method.

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

    OpenAIRE

    D. Q. Fang; Y. G. Ma; Cai, X. Z.(Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 201800, Shanghai, China); Tian, W.D.; Wang, H. W.

    2010-01-01

    We study the relation between neutron removal cross section ($\\sigma_{-N}$) and neutron skin thickness for finite neutron rich nuclei using the statistical abrasion ablation (SAA) model. Different sizes of neutron skin are obtained by adjusting the diffuseness parameter of neutrons in the Fermi distribution. It is demonstrated that there is a good linear correlation between $\\sigma_{-N}$ and the neutron skin thickness for neutron rich nuclei. Further analysis suggests that the relative increa...

  12. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  13. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2010-07-01

    The following topics are dealt with: The thermal triple axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, neutron polarization analysis with tht time-of-flight spectrometer DNS, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering with the KWS-1 and KWS-2 diffractometers, the very-small-angle neutron scattering diffractrometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  14. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2012-07-01

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, the neutron polarization analyzer DNS, the neutron spin-echo spectrometer J-NSE, the small-angle neutron diffractometers KWS-1/-2, the very-small-angle neutron diffractometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  15. Grazing Incidence Neutron Optics

    Science.gov (United States)

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

    2013-01-01

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

  16. Neutron scatter camera

    Science.gov (United States)

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

    2010-06-22

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

  17. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot single-crystal diffractometer HEiDi for structure analysis with neutrons, the backscattering spectrometer SPHERES, the neutron polarization analyzer DNS, the neutron spin-echo spectrometer J-NSE, the small-angle neutron diffractometers KWS-1/-2, the very-small-angle neutron diffractometer with focusing mirror KWS-3, the resonance spin-echo spectrometer RESEDA, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  18. Neutron techniques in Safeguards

    International Nuclear Information System (INIS)

    An essential part of Safeguards is the ability to quantitatively and nondestructively assay those materials with special neutron-interactive properties involved in nuclear industrial or military technology. Neutron techniques have furnished most of the important ways of assaying such materials, which is no surprise since the neutronic properties are what characterizes them. The techniques employed rely on a wide selection of the many methods of neutron generation, detection, and data analysis that have been developed for neutron physics and nuclear science in general

  19. Advances in neutron tomography

    Indian Academy of Sciences (India)

    W Treimer

    2008-11-01

    In the last decade neutron radiography (NR) and tomography (NCT) have experienced a number of improvements, due to the well-known properties of neutrons interacting with matter, i.e. the low attenuation by many materials, the strong attenuation by hydrogenous constituent in samples, the wavelength-dependent attenuation in the neighbourhood of Bragg edges and due to better 2D neutron detectors. So NR and NCT were improved by sophisticated techniques that are based on the attenuation of neutrons or on phase changes of the associated neutron waves if they pass through structured materials. Up to now the interaction of the neutron spin with magnetic fields in samples has not been applied to imaging techniques despite the fact that it was proposed many years ago. About ten years ago neutron depolarization as imaging signal for neutron radiography or tomography was demonstrated and in principle it works. Now one can present much improved test experiments using polarized neutrons for radiographic imaging. For this purpose the CONRAD instrument of the HMI was equipped with polarizing and analysing benders very similar to conventional scattering experiments using polarized neutrons. Magnetic fields in different coils and in samples (superconductors) at low temperatures could be visualized. In this lecture a summary about standard signals (attenuation) and the more `sophisticated' imaging signals as refraction, small angle scattering and polarized neutrons will be given.

  20. Neutron structural biology

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-03-01

    Neutron diffraction provides an experimental method of directly locating hydrogen atoms in protein which play important roles in physiological functions. However, there are relatively few examples of neutron crystallography in biology since it takes a lot of time to collect a sufficient number of Bragg reflections due to the low flux of neutrons illuminating the sample. In order to overcome the flux problem, we have successfully developed the neutron IP, where the neutron converter, {sup 6}Li or Gd, was mixed with a photostimulated luminescence material on flexible plastic support. Neutron Laue diffraction 2A data from tetragonal lysozyme were collected for 10 days with neutron imaging plates, and 960 hydrogen atoms in the molecule and 157 bound water molecules were identified. These results explain the proposed hydrolysis mechanism of the sugar by the lysozyme molecule and that lysozyme is less active at pH7.0. (author)

  1. Neutron response study

    International Nuclear Information System (INIS)

    Neutron response of the albedo type dosimeter is strongly dependent on the energy of the incident neutrons as well as the moderating material on the backside of the dosimeter. This study characterizes the response of the Hanford dosimeter for a variety of neutron energies for both a water and Rando phantom (a simulated human body consisting of an actual human skeleton with plastic for body muscles and certain organs). The Hanford dosimeter response to neutrons of different energies is typical of albedo type dosimeters. An approximate two orders of magnitude difference in response is observed between neutron energies of 100 keV and 10 MeV. Methods were described to compensate for the difference in dosimeter response between a laboratory neutron spectrum and the different spectra encountered at various facilities in the field. Generally, substantial field support is necessary for accurate neutron dosimetry

  2. Neutron polarisation for ISIS

    International Nuclear Information System (INIS)

    Scattering experiments using polarised thermal and cold neutron beams have made important contributions to condensed matter physics, particularly to the understanding of atomic magnetism. This has been largely due to the vigorous efforts made at reactor institutes to develop polarised beam technology; their success in this enterprise is now paying handsome dividends. Progress in developing comparable techniques for pulsed neutron sources has been slower, largely due to the greater practical difficulties associated with polarising higher energy neutrons. However, there has been some advance, and this has now provided clarification into the best ways of integrating the various polarising devices into pulsed source spectrometers. The status of polarised neutron spectrometers at pulsed neutron sources is reviewed. The paper deals with three main topics, the scientific relevance of polarised neutron scattering experiments, a discussion of the properties of neutron polarisers, emphasising their strengths and limitations, and the integration of polarisers into a range of ISIS pulsed source spectrometers. (author)

  3. The next generation neutron soure ESS: What is new and what is not

    International Nuclear Information System (INIS)

    ESS is on track to start operation in 2019 as the first long pulse spallation source in history, i.e. a bit more than 25 years after the long pulse concept was introduced. In view of the usual long lead times for funding decisions on new facilities, being based on quarter of century old concepts is commonly boasted as novelty. In contrast to most other large scale projects, ESS has in addition the key feature that it requires now new hardware technology. It makes instead radically innovative use of established technologies, offering ESS an unusually high predictability compared to projects that require(d) cutting edge developments (e.g. LHC, ITER,…). Conventional pulsed spallation sources use linear accelerators to create typically ms long proton pulses, which are then compressed by ring accelerators to less than 1 μs length, with or without further acceleration. The higher efficiency and performance of the long pulse source is achieved by suppressing the ring accelerator and related extra complexities. The savings are used to make the linear accelerator deliver more protons for producing more neutrons. Thus even with identical moderators, the ESS neutronic performance in terms of useful thermal and cold neutrons delivered to the samples is close to an order of magnitude higher at identical resolution parameters than that of the about cost equivalent SNS.. The key neutron scattering experimental capability readily achieved at ESS by reactor type mechanical chopper systems is the unrestricted potential of pulse shaping, i.e. cutting out short pulses with a great flexibility of length from the long pulses provided by the accelerator. The way to do this has been established many years ago including implementation using reactor source instruments and is now routinely utilized at one of the very successful spectrometers of J-PARC. The main recent novelty is the development of low dimensional moderators which allow us to increase the extracted cold neutron brightness

  4. Curved neutron guide

    International Nuclear Information System (INIS)

    The principle of the curved neutron guide is to transport neutrons far away from the reactor core with as minimum particle loss as possible. After a series of total reflection,the neutron beam is no longer visible from the reactor core and consequently, gamma radiations and fast neutrons emitted from the core are scattered by the walls of the guide and absorbed by the biological shielding set around the guide. The curved neutron guide provides a high-quality beam of slow neutrons. The first chapter deals with the theoretical concept of curved guide, we have determined the parameters for the setting of such a guide in the EL3 reactor at Saclay (France). The different tolerances on the state the surface, on the alignment of the different parts of the guide, on the waving of the guide wall have been assessed. The second chapter presents the technical solution chosen that complies to all the required specifications. The curved neutron guide has been designed for neutrons with wavelength of 4 Angstroms, it is 29 m long, has a bending radius of 835 m and is composed of 87 rectangular components made of glass plates on which a 1500 angstrom thick layer of nickel has been deposited. Each component is set with a fixed angle of (4±0.25)*10-4 radians from the previous component in order to form the bending radius. The last chapter is dedicated to the neutron flux measurement made at the end of the neutron guide

  5. SENJU: a new time-of-flight single-crystal neutron diffractometer at J-PARC

    Science.gov (United States)

    Ohhara, Takashi; Kiyanagi, Ryoji; Oikawa, Kenichi; Kaneko, Koji; Kawasaki, Takuro; Tamura, Itaru; Nakao, Akiko; Hanashima, Takayasu; Munakata, Koji; Moyoshi, Taketo; Kuroda, Tetsuya; Kimura, Hiroyuki; Sakakura, Terutoshi; Lee, Chang-Hee; Takahashi, Miwako; Ohshima, Ken-ichi; Kiyotani, Tamiko; Noda, Yukio; Arai, Masatoshi

    2016-01-01

    SENJU is a new single-crystal time-of-flight neutron diffractometer installed at BL18 at the Materials and Life Science Experimental Facility of the Japan Accelerator Research Complex (J-PARC). The diffractometer was designed for precise crystal and magnetic structure analyses under multiple extreme sample environments such as low temperature, high pressure and high magnetic field, and for diffraction measurements of small single crystals down to 0.1 mm3 in volume. SENJU comprises three choppers, an elliptical shape straight supermirror guide, a vacuum sample chamber and 37 scintillator area detectors. The moderator-to-sample distance is 34.8 m, and the sample-to-detector distance is 800 mm. The wavelength of incident neutrons is 0.4–4.4 Å (first frame). Because short-wavelength neutrons are available and the large solid angle around the sample position is covered by the area detectors, a large reciprocal space can be simultaneously measured. Furthermore, the vacuum sample chamber and collimator have been designed to produce a very low background level. Thus, the measurement of a small single crystal is possible. As sample environment devices, a newly developed cryostat with a two-axis (ω and φ axes) goniometer and some extreme environment devices, e.g. a vertical-field magnet, high-temperature furnace and high-pressure cell, are available. The structure analysis of a sub-millimetre size (0.1 mm3) single organic crystal, taurine, and a magnetic structure analysis of the antiferromagnetic phase of MnF2 have been performed. These results demonstrate that SENJU can be a powerful tool to promote materials science research. PMID:26937237

  6. Pulsed neutron porosity logging system

    International Nuclear Information System (INIS)

    An improved pulsed neutron porosity logging system is provided in the present invention. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector, and a fast neutron detector is moved through a borehole. Repetitive bursts of neutrons irradiate the earth formations and, during the bursts, the fast neutron population is sampled. During the interval between bursts the epithermal neutron population is sampled along with background gamma radiation due to lingering thermal neutrons. The fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity

  7. Neutron radiography using neutron imaging plate.

    Science.gov (United States)

    Chankow, Nares; Punnachaiya, Suvit; Wonglee, Sarinrat

    2010-01-01

    The aims of this research are to study properties of a neutron imaging plate (NIP) and to test it for use in nondestructive testing (NDT) of materials. The experiments were carried out by using a BAS-ND 2040 Fuji NIP and a neutron beam from the Thai Research Reactor TRR-1/M1. The neutron intensity and Cd ratio at the specimen position were approximately 9x10(5) ns/cm(2) s and 100 respectively. It was found that the photostimulated luminescence (PSL) readout of the imaging plate was directly proportional to the exposure time and approximately 40 times faster than the conventional NR using Gd converter screen/X-ray film technique. The sensitivities of the imaging plate to slow neutron and to Ir-192 gamma-rays were found to be approximately 4.2x10(-3) PSL/mm(2) per neutron and 6.7x10(-5) PSL/mm(2) per gamma-ray photon respectively. Finally, some specimens containing light elements were selected to be radiographed with neutrons using the NIP and the Gd converter screen/X-ray film technique. The image quality obtained from the two recording media was found to be comparable. PMID:19828321

  8. Neutron radiography using neutron imaging plate

    International Nuclear Information System (INIS)

    The aims of this research are to study properties of a neutron imaging plate (NIP) and to test it for use in nondestructive testing (NDT) of materials. The experiments were carried out by using a BAS-ND 2040 Fuji NIP and a neutron beam from the Thai Research Reactor TRR-1/M1. The neutron intensity and Cd ratio at the specimen position were approximately 9x105 ns/cm2 s and 100 respectively. It was found that the photostimulated luminescence (PSL) readout of the imaging plate was directly proportional to the exposure time and approximately 40 times faster than the conventional NR using Gd converter screen/X-ray film technique. The sensitivities of the imaging plate to slow neutron and to Ir-192 gamma-rays were found to be approximately 4.2x10-3 PSL/mm2 per neutron and 6.7x10-5 PSL/mm2 per gamma-ray photon respectively. Finally, some specimens containing light elements were selected to be radiographed with neutrons using the NIP and the Gd converter screen/X-ray film technique. The image quality obtained from the two recording media was found to be comparable.

  9. Status of spallation neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Oyama, Yukio [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-03-01

    Existing and planned facilities using proton accelerator driven spallation neutron source are reviewed. These include new project of neutron science proposed from Japan Atomic Energy Research Institute. The present status of facility requirement and accelerator technology leads us to new era of neutron science such as neutron scattering research and nuclear transmutation study using very intense neutron source. (author)

  10. Neutron sources and applications

    Energy Technology Data Exchange (ETDEWEB)

    Price, D.L. [ed.] [Argonne National Lab., IL (United States); Rush, J.J. [ed.] [National Inst. of Standards and Technology, Gaithersburg, MD (United States)

    1994-01-01

    Review of Neutron Sources and Applications was held at Oak Brook, Illinois, during September 8--10, 1992. This review involved some 70 national and international experts in different areas of neutron research, sources, and applications. Separate working groups were asked to (1) review the current status of advanced research reactors and spallation sources; and (2) provide an update on scientific, technological, and medical applications, including neutron scattering research in a number of disciplines, isotope production, materials irradiation, and other important uses of neutron sources such as materials analysis and fundamental neutron physics. This report summarizes the findings and conclusions of the different working groups involved in the review, and contains some of the best current expertise on neutron sources and applications.

  11. Biological effects of neutrons

    International Nuclear Information System (INIS)

    Although the occasion to be exposed to neutrons is rare in our life, except for nuclear accidents like in the critical accident at Tokai-mura in 1999, countermeasures against accident should be always prepared. In the Tokai-mura accident, residents received less than 21 mSv of neutrons and gamma rays. The cancer risks and fetal effects of low doses of neutrons were matters of concern among residents. The purpose of this program is to investigate the relative biological effectiveness (RBE) for leukemias, and thereby to assess risks of neutrons. Animal experiments are planed to obtain the following RBEs: (1) RBE for the induction of leukemias in mice and (2) RBE for effects on fetuses. Cyclotron fast neutrons (10 MeV) and electrostatic accelerator-derived neutrons (2 MeV) are used for exposure in this program. Furthermore, cytological and cytogenetic analyses will be performed. (author)

  12. Resonance neutron radiography

    International Nuclear Information System (INIS)

    The production of images by the use of neutrons having energies in the resonance region is described. Two-dimensional position-sensitive neutron detectors are used to produce transmission images using neutron time-of-flight techniques at the National Bureau of Standards' electron linac facility. Two types of detectors are described. The first is a crossed-wire proportional counter using 3He as the neutron-sensitive component. The second type utilizes a multichannel plate electron multiplier and a resistive anode readout. A lithium glass scintillator is the neutron-sensitive component in the latter detector. Resonance neutron radiography, using these detectors, has the capability of producing images with isotopic and chemical element discrimination in a complex matrix with a resolution of 1 mm or better. (Auth.)

  13. Active neutron instrumentation

    International Nuclear Information System (INIS)

    An introduction to neutron interactions in tissue and a discussion of pertinent nuetron cross-sections will be given. A brief description of the statistics of energy deposition due to interactions of neutron secondaries in tissue equivalent media is presented. Present and past techniques for measurement of neutron radiation fields are given with advantages and disadvantages in the light of legal limits and proposed changes in those requirements. Neutron dose measuring devices, such as the tissue equivalent proportional counter (TEPC) developed by Rossi, are discussed with emphasis on their response in varying neutron energy spectra. Techniques for determining neutron quality factors from TEPC response functions are discussed along with implications of possible new definitions of quality factor. A brief description of high-resolution spectrometry systems, which use hydrogen, methane and He-3 fill gases, is given with discussion of their limitations. Low resolution systems, such as multisphere spectrometers and activation foils, are also presented

  14. Gravitational neutron monochromator

    International Nuclear Information System (INIS)

    A new type of slow-neutron monochromator is described that is based on the interaction of slow neutrons with the earth's gravitational field. The monochromator is formed by three slit collimators placed along the neutron trajectory. The energy of the neutrons selected by the monochromator is set by vertical movement of any of the slit collimators. This scheme was used to create a gravitational monochromator on the 1000-meter path of the IBR-30 pulsed fast reactor at Dubna. It provides monochromatic neutrons with an energy resolution of 1.8% and measures the free-fall acceleration of neutrons with an error of 0.1% in the energy range of 0.0175-0.4223 eV

  15. Burnable neutron absorber element

    International Nuclear Information System (INIS)

    A burnable thermal neutron absorber element is described comprising: a zirconium alloy elongated tubular container having an inside diameter surface; hydrogen diffusion barrier means for limiting hydrogen diffusion from within the container into the zirconium alloy; a boron-containing burnable thermal neutron absorber material sealed within the zirconium alloy elongated container, the boron-containing burnable absorber material being in a particle form, the particles of absorber material being coated with a diffusion barrier material; zirconium hydride sealed within the zirconium alloy elongated container, the zirconium hydride being in a partially hydrided condition and having a H to Zr ratio on an atomic basis in the range of about 1.0 to about 1.8; the burnable thermal neutron absorber material and the zirconium hydride distributed along the length of the zirconium alloy elongated container; and the zirconium hydride acts as a neutron moderator thereby enhancing the neutron capture efficiency of the burnable thermal neutron absorber

  16. Burnable neutron absorber element

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, H.M.

    1988-06-14

    A burnable thermal neutron absorber element is described comprising: a zirconium alloy elongated tubular container having an inside diameter surface; hydrogen diffusion barrier means for limiting hydrogen diffusion from within the container into the zirconium alloy; a boron-containing burnable thermal neutron absorber material sealed within the zirconium alloy elongated container, the boron-containing burnable absorber material being in a particle form, the particles of absorber material being coated with a diffusion barrier material; zirconium hydride sealed within the zirconium alloy elongated container, the zirconium hydride being in a partially hydrided condition and having a H to Zr ratio on an atomic basis in the range of about 1.0 to about 1.8; the burnable thermal neutron absorber material and the zirconium hydride distributed along the length of the zirconium alloy elongated container; and the zirconium hydride acts as a neutron moderator thereby enhancing the neutron capture efficiency of the burnable thermal neutron absorber.

  17. Neutron sources and applications

    International Nuclear Information System (INIS)

    Review of Neutron Sources and Applications was held at Oak Brook, Illinois, during September 8--10, 1992. This review involved some 70 national and international experts in different areas of neutron research, sources, and applications. Separate working groups were asked to (1) review the current status of advanced research reactors and spallation sources; and (2) provide an update on scientific, technological, and medical applications, including neutron scattering research in a number of disciplines, isotope production, materials irradiation, and other important uses of neutron sources such as materials analysis and fundamental neutron physics. This report summarizes the findings and conclusions of the different working groups involved in the review, and contains some of the best current expertise on neutron sources and applications

  18. Polysiloxane based neutron detectors

    OpenAIRE

    Dalla Palma, Matteo

    2016-01-01

    In the last decade, neutron detection has been attracting the attention of the scientific community for different reasons. On one side, the increase in the price of 3He, employed in the most efficient and the most widely used neutron detectors. On the other side, the harmfulness of traditional xylene based liquid scintillators, used in extremely large volumes for the detection of fast neutrons. Finally, the demand for most compact and rough systems pushed by the increased popularity of neutro...

  19. ATR neutron spectral characterization

    International Nuclear Information System (INIS)

    The Advanced Test Reactor (ATR) at INEL provides intense neutron fields for irradiation-effects testing of reactor material samples, for production of radionuclides used in industrial and medical applications, and for scientific research. Characterization of the neutron environments in the irradiation locations of the ATR has been done by means of neutronics calculations and by means of neutron dosimetry based on the use of neutron activation monitors that are placed in the various irradiation locations. The primary purpose of this report is to present the results of an extensive characterization of several ATR irradiation locations based on neutron dosimetry measurements and on least-squares-adjustment analyses that utilize both neutron dosimetry measurements and neutronics calculations. This report builds upon the previous publications, especially the reference 4 paper. Section 2 provides a brief description of the ATR and it tabulates neutron spectral information for typical irradiation locations, as derived from the more historical neutron dosimetry measurements. Relevant details that pertain to the multigroup neutron spectral characterization are covered in section 3. This discussion includes a presentation on the dosimeter irradiation and analyses and a development of the least-squares adjustment methodology, along with a summary of the results of these analyses. Spectrum-averaged cross sections for neutron monitoring and for displacement-damage prediction in Fe, Cr, and Ni are given in section 4. In addition, section4 includes estimates of damage generation rates for these materials in selected ATR irradiation locations. In section 5, the authors present a brief discussion of the most significant conclusions of this work and comment on its relevance to the present ATR core configuration. Finally, detailed numerical and graphical results for the spectrum-characterization analyses in each irradiation location are provided in the Appendix

  20. Neutrons and Nuclear Engineering

    International Nuclear Information System (INIS)

    Oak Ridge National Laboratory hosted two workshops in April 2007 relevant to nuclear engineering education. In the Neutron Stress, Texture, and Phase Transformation for Industry workshop (http://neutrons.ornl.gov/workshops/nst2/), several invited speakers gave examples of neutron stress mapping for nuclear engineering applications. These included John Root of National Research Council of Canada, Mike Fitzpatrick of the UK's Open University, and Yan Gao of GE Global Research on their experiences with industrial and academic uses of neutron diffraction. Xun-Li Wang and Camden Hubbard described the new instruments at ORNL that can be used for such studies. This was preceded by the Neutrons for Materials Science and Engineering educational symposium (http://neutrons.ornl.gov/workshops/edsym2007). It was directed to the broad materials science and engineering community based in universities, industry and laboratories who wish to learn what the neutron sources in the US can provide for enhancing the understanding of materials behavior, processing and joining. Of particular interest was the presentation of Donald Brown of Los Alamos about using 'Neutron diffraction measurements of strain and texture to study mechanical behavior of structural materials.' At both workshops, the ORNL neutron scattering instruments relevant to nuclear engineering studies were described. The Neutron Residual Stress Mapping Facility (NRSF2) is currently in operation at the High Flux Isotope Reactor; the VULCAN Engineering Materials Diffractometer will begin commissioning in 2008 at the Spallation Neutron Source. For characteristics of these instruments, as well as details of other workshops, meetings, capabilities, and research proposal submissions, please visit http://neutrons.ornl.gov. To submit user proposals for time on NRSF2 contact Hubbard at hubbardcratornl.gov

  1. DEMON: Modular Neutron Detector

    International Nuclear Information System (INIS)

    DEMON is a liquid scintillator neutron multidetector devoted to study particular aspects of the dynamics of heavy-ion reactions. The problems of measuring neutron energy spectra, angular distributions and neutron multiplicities are described. Efficiency measurements, time-of-flight measurements and the experimental programme of the detector are presented. The document consists of transparencies presented at the workshop, text is missing. (K.A.) 12 figs

  2. The DIORAMA Neutron Emitter

    Energy Technology Data Exchange (ETDEWEB)

    Terry, James Russell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-05-05

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

  3. Broadband Neutron Interferometer

    OpenAIRE

    Pushin, Dmitry A.; Sarenac, Dusan; Hussey, Dan; Miao, Houxun; Arif, Muhammad; Cory, David G.; Huber, Michael G.; Jacobson, David; LaManna, Jacob; Parker, Joseph D.; Shinohara, Taken; Ueno, Wakana; Wen, Han

    2016-01-01

    We demonstrate a two phase-grating, multi-beam neutron interferometer by using a modified Ronchi setup in a far-field regime. The functionality of the interferometer is based on the universal \\moire effect that was recently implemented for X-ray phase-contrast imaging in the far-field regime. Interference fringes were achieved with monochromatic, bichromatic, and polychromatic neutron beams; for both continuous and pulsed beams. This far-field neutron interferometry allows for the utilization...

  4. Neutron scattering. Experiment manuals

    International Nuclear Information System (INIS)

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot-single-crystal diffractometer HEiDi, the three-axis spectrometer PANDA, the backscattering spectrometer SPHERES, the DNS neutron-polarization analysis, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering at KWS-1 and KWS-2, a very-small-angle neutron scattering diffractometer with focusing mirror, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  5. Neutron powder diffraction

    International Nuclear Information System (INIS)

    Neutron powder diffraction is a powerful technique that provides a detailed description of moderately complex crystal structures. This is nowhere more apparent than in the area of high temperature superconductors where neutron powder diffraction has provided precise structural and magnetic information, not only under ambient conditions but also at high and low temperatures and high pressures. Outside superconductor research, the variety of materials studied by neutron powder diffraction is equally impressive including zeolites, fast ionic conductors, permanent magnets and materials undergoing phase transitions. Recent advances that include high resolution studies and real-time crystallography are presented. Future possibilities of neutron powder diffraction are discussed

  6. A neutron prism

    International Nuclear Information System (INIS)

    A neutron detector with an energy and time resolution makes it possible to realize a new type of a scattering instrument. Such kind of detector can be developed by combining the neutron refractive device (neutron prism) and position-sensitive-detector (PSD) with a time resolution. As the neutron refractive device, two candidates are considered; a compound refractive device and magnetic field gradient. In former case, suitable choice of material and design of the refractive device overcomes a problem of neutron absorption and weak refraction due to material. On the other hand, the magnetic field gradient has an advantage that it has a large refraction and zero neutron absorption comparing with the compound refractive device. A refractive device has been developed with suitable material and design for neutron optics and a quadrupole magnet with permanent magnets in which a constant field gradient is realized. In this paper, the construction and performance of the energy and time resoluble detectors using the neutron refractive devices are described and their application to a neutron scattering experiment is discussed. (author)

  7. Neutron scattering. Experiment manuals

    Energy Technology Data Exchange (ETDEWEB)

    Brueckel, Thomas; Heger, Gernot; Richter, Dieter; Roth, Georg; Zorn, Reiner (eds.)

    2014-07-01

    The following topics are dealt with: The thermal triple-axis spectrometer PUMA, the high-resolution powder diffractometer SPODI, the hot-single-crystal diffractometer HEiDi, the three-axis spectrometer PANDA, the backscattering spectrometer SPHERES, the DNS neutron-polarization analysis, the neutron spin-echo spectrometer J-NSE, small-angle neutron scattering at KWS-1 and KWS-2, a very-small-angle neutron scattering diffractometer with focusing mirror, the reflectometer TREFF, the time-of-flight spectrometer TOFTOF. (HSI)

  8. Effective neutron targets

    International Nuclear Information System (INIS)

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

  9. Neutron structural biology

    International Nuclear Information System (INIS)

    Neutron structural biology will be one of the most important fields in the life sciences which will interest human beings in the 21st century because neutrons can provide not only the position of hydrogen atoms in biological macromolecules but also the dynamic molecular motion of hydrogen atoms and water molecules. However, there are only a few examples experimentally determined at present because of the lack of neutron source intensity. Next generation neutron source scheduled in JAERI (Performance of which is 100 times better than that of JRR-3M) opens the life science of the 21st century. (author)

  10. Neutrons in biology

    International Nuclear Information System (INIS)

    The start of JRR-3M in 1990 was a great epoch to the neutron scattering research in Japan. Abundant neutron beam generated by the JRR-3M made it possible to widen the research field of neutron scattering in Japan. In the early days of neutron scattering, biological materials were too difficult object to be studied by neutrons not only because of their complexity but also because of the strong incoherent scattering by hydrogen. However, the remarkable development of the recent neutron scattering and its related sciences, as well as the availability of higher flux, has made the biological materials one of the most attractive subjects to be studied by neutrons. In early September 1992, an intensive workshop titled 'Neutrons in Biology' was held in Hitachi City by making use of the opportunity of the 4th International Conference on Biophysics and Synchrotron Radiation (BSR92) held in Tsukuba. The workshop was organized by volunteers who are eager to develop the researches in this field in Japan. Numbers of outstanding neutron scattering biologists from U.S., Europe and Asian countries met together and enthusiastic discussions were held all day long. The editors believe that the presentations at the workshop were so invaluable that it is absolutely adequate to put them on record as an issue of JAERI-M and to make them available for scientists to refer to in order to further promote the research in the future. (author)

  11. CIT: Neutron Generator Systems

    International Nuclear Information System (INIS)

    Neutron generator systems, including neutron tubes: (1) Controls - HS: 8543.19, 8479.89, 9015.80, 9027.80 - NSG DUL: 6.A.5. - EU: 3A231; (2) Nuclear uses - initiate nuclear fission chain reaction in a nuclear explosive device - to analyze the state of reactors or other critical assemblies; and (3) Other uses - Downhole oil well logging - plutonium and effluent flow analysis - examination of sealed packages (to detect explosives, etc.) - detection or assay of fissionable materials - neutron radiography, physics research, radiation therapy for cancer. Neutron generator systems include a neutron tube, control unit, and a high-voltage power supply. The neutron tube is the fundamental element. Neutron generator tubes are usually cylindrical. The tube housing can be glass, ceramic, or metal, with sizes between 3.8-6.4 cm in diameter and 10-30 cm in length. Neutron generator assemblies contain the neutron tube, magnet, and high-voltage transformer. It may be enclosed in a glass, ceramic, or steel cylinder 10-25 cm in diameter, 43-61 cm in length. Assemblies are typically filled with a dielectric gas or liquid to insulate and cool the high-voltage circuitry.

  12. Neutron visual sensing technique

    International Nuclear Information System (INIS)

    The neutron visual sensing technique is a technology to extract physical quantities from the information on inner structures of complex materials or machineries which have been visualized and recorded by using neutron beams. Research and utilization of this technique is now under worldwide development since it can provide the information that is not possible by X-ray radiography. We show how to use stationary neutron sources (Research reactors) in chapter 2, and how to utilize pulsed neutron source (Japan Proton Accelerator Complex, J-PARC). Also the production of micro-element analyzer by an enterprise using the knowledge on radiological equipment is described as an example. (author)

  13. In-beam test of the Boron-10 Multi-Grid neutron detector at the IN6 time-of-flight spectrometer at the ILL

    International Nuclear Information System (INIS)

    A neutron detector concept based on solid layers of boron carbide enriched in 10B has been in development for the last few years as an alternative for 3He by collaboration between the ILL, ESS and Linköping University. This Multi-Grid detector uses layers of aluminum substrates coated with 10B4C on both sides that are traversed by the incoming neutrons. Detection is achieved using a gas counter readout principle. By segmenting the substrate and using multiple anode wires, the detector is made inherently position sensitive. This development is aimed primarily at neutron scattering instruments with large detector areas, such as time-of-flight chopper spectrometers. The most recent prototype has been built to be interchangeable with the 3He detectors of IN6 at ILL. The 10B detector has an active area of 32 x 48cm2. It was installed at the IN6 instrument and operated for several weeks, collecting data in parallel with the regularly scheduled experiments, thus providing the first side-by-side comparison with the conventional 3He detectors. Results include an efficiency comparison, assessment of the in-detector scattering contribution, sensitivity to gamma-rays and the signal-to-noise ratio in time-of-flight spectra. The good expected performance has been confirmed with the exception of an unexpected background count rate. This has been identified as natural alpha activity in aluminum. New convertor substrates are under study to eliminate this source of background.

  14. Neutron-emission measurements at a white neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Haight, Robert C [Los Alamos National Laboratory

    2010-01-01

    Data on the spectrum of neutrons emittcd from neutron-induced reactions are important in basic nuclear physics and in applications. Our program studies neutron emission from inelastic scattering as well as fission neutron spectra. A ''white'' neutron source (continuous in energy) allows measurements over a wide range of neutron energies all in one experiment. We use the tast neutron source at the Los Alamos Neutron Science Center for incident neutron energies from 0.5 MeV to 200 MeV These experiments are based on double time-of-flight techniques to determine the energies of the incident and emitted neutrons. For the fission neutron measurements, parallel-plate ionization or avalanche detectors identify fission in actinide samples and give the required fast timing pulse. For inelastic scattering, gamma-ray detectors provide the timing and energy spectroscopy. A large neutron-detector array detects the emitted neutrons. Time-of-flight techniques are used to measure the energies of both the incident and emitted neutrons. Design considerations for the array include neutron-gamma discrimination, neutron energy resolution, angular coverage, segmentation, detector efficiency calibration and data acquisition. We have made preliminary measurements of the fission neutron spectra from {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. Neutron emission spectra from inelastic scattering on iron and nickel have also been investigated. The results obtained will be compared with evaluated data.

  15. Development of methods for measuring materials nuclear characteristics, Phases, I, II, II and IV

    International Nuclear Information System (INIS)

    This report contains the following phases of the project 'measurement of nuclear characteristics of reactor materials': nuclear performances of the neutron chopper; method for measuring total effective cross sections by transmission method on the chopper; review of methods for measuring activation cross sections; measurement of neutron spectra of the RA reactor and measurement of total effective cross section of gold by using the chopper

  16. Neutron Stars: Formation and Structure

    OpenAIRE

    Kutschera, Marek

    1998-01-01

    A short introduction is given to astrophysics of neutron stars and to physics of dense matter in neutron stars. Observed properties of astrophysical objects containing neutron stars are discussed. Current scenarios regarding formation and evolution of neutron stars in those objects are presented. Physical principles governing the internal structure of neutron stars are considered with special emphasis on the possible spin ordering in the neutron star matter.

  17. Neutron optics requirements for neutron imaging techniques

    International Nuclear Information System (INIS)

    The utilization of X-rays for material research is common in many respects since their discovery at the end of the 19th century. New sources as electron synchrotrons or free-electron lasers push the methodology and the application ranges further. A similar approach started 50 years later with neutrons when sources with reasonable high intensity became available. Today, there are many similarities and complementarities visible between X-ray and neutron studies and the involved techniques. Therefore, it is worth to compare and to adapt from the advanced X-ray techniques and to translate it into the neutron world. Despite of the lack of neutron intensities compared to the most brilliant X-ray beams, the specific properties of neutrons (contrast, spin, magnetic moment, penetration power) are utilized and they will further play an important role in non-invasive studies on the micro- and macro scale. This paper wants to encourage to 'look over the fence' into activities of the X-ray community as currently running in the COST action MP-1203.

  18. Lattice design of medium energy beam transport line for n spallation neutron source

    International Nuclear Information System (INIS)

    A 1 GeV H- injector linac is being designed at RRCAT for the proposed Indian Spallation Neutron Source (ISNS). The front-end of the injector linac will consist of Radiofrequency Quadrupole (RFQ) linac, which will accelerate the H- beam from 50 keV to 3 MeV. The beam will be further accelerated in superconducting Single Spoke Resonators (SSRs). A Medium Energy Beam Transport (MEBT) line will be used to transport the beam from the exit of RFQ to the input of SSR. The main purpose of MEBT is to carry out beam matching from RFQ to SSR, and beam chopping. In this paper, we describe the optimization criteria for the lattice design of MEBT. The optimized lattice element parameters are presented for zero and full (15 mA) current case. Beam dynamics studies have been carried out using an envelope tracing code Trace-3D. Required beam deflection angle due to the chopper housed inside the MEBT for beam chopping has also been estimated. (author)

  19. Recently commissioned time-of-flight small angle neutron scattering machine at ANSTO: Capabilities and performance

    International Nuclear Information System (INIS)

    Australian Nuclear Science and technology Organization (ANSTO) successfully operates one SANS instrument Quokka and recently commenced commissioning of the second SANS instrument, Bilby. The Bilby is Time-of-Flight instrument built on reactor neutron source. The instrument is scheduled to be in user operation in the second half of the year 2015. The design (in particular, set-up of four choppers which similar to that design for D33 instrument at ILL) opens possibility to vary wavelength resolution in the wide range (from 4% to 30%) satisfying various scientists’ requirements. Two arrays of position sensitive detectors in combination with utilizing of wide wavelength range (from ~3Å to ~20Å) provide capability to collect scattering data of wide angular range without changing experimental set-up. Offered instrument design opens possibility to collect scattering from a wide range of samples, with a unique capability to record fast kinetics data. Additional hardware add-on will allow to use instrument in slit mode and therefore get data at very low Q (~2·10-4Å-1). The presentation will be focused on general concept and unique features of the new SANS instrument, as well as first results of instrument commissioning.

  20. Neutron monitoring for radiological protection

    International Nuclear Information System (INIS)

    Neutron monitoring is a subject of increasing general interest and considerable attention is being paid to the development of improved techniques and methods for neutron monitoring. The Agency, therefore, considered it important to prepare a guide on the subject of neutron monitoring for radiation protection purposes. The present Manual is intended for those persons or authorities in Member States, particularly developing countries, who are responsible for the organization of neutron monitoring programmes and practical neutron monitoring. This Manual consequently, deals with topics such as neutron dosimetry, sources of neutrons and neutron detection as well as field instruments and operational systems used in this context

  1. Neutron spectroscopy, nuclear structure, related topics. Abstracts

    International Nuclear Information System (INIS)

    Neutron spectroscopy, nuclear structure and related topics are considered. P, T-breaking, neutron beta decay, neutron radiative capture and neutron polarizability are discussed. Reaction with fast neutrons, methodical aspect low-energy fission are considered too

  2. Neutron resonance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Gunsing, F

    2005-06-15

    The present document has been written in order to obtain the diploma 'Habilitation a Diriger des Recherches'. Since this diploma is indispensable to supervise thesis students, I had the intention to write a document that can be useful for someone starting in the field of neutron resonance spectroscopy. Although the here described topics are already described elsewhere, and often in more detail, it seemed useful to have most of the relevant information in a single document. A general introduction places the topic of neutron-nucleus interaction in a nuclear physics context. The large variations of several orders of magnitude in neutron-induced reaction cross sections are explained in terms of nuclear level excitations. The random character of the resonances make nuclear model calculation predictions impossible. Then several fields in physics where neutron-induced reactions are important and to which I have contributed in some way or another, are mentioned in a first synthetic chapter. They concern topics like parity nonconservation in certain neutron resonances, stellar nucleosynthesis by neutron capture, and data for nuclear energy applications. The latter item is especially important for the transmutation of nuclear waste and for alternative fuel cycles. Nuclear data libraries are also briefly mentioned. A second chapter details the R-matrix theory. This formalism is the foundation of the description of the neutron-nucleus interaction and is present in all fields of neutron resonance spectroscopy. (author)

  3. Neutron scattering by ferroelectrics

    CERN Document Server

    Aksenov, V; Stamenkovic, S

    1989-01-01

    This book presents the recent theoretical and experimental developments of neutron scattering by ferroelectrics. A Model description of lattice dynamics of structurally unstable crystals (self-consistent phonon approximation, pseudo-spin formalism, coherent potential approximation etc.) is formulated. The effects of nonlinear excitations and lattice defects in neutron scattering are also discussed.

  4. Synovectomy by Neutron capture

    International Nuclear Information System (INIS)

    The Synovectomy by Neutron capture has as purpose the treatment of the rheumatoid arthritis, illness which at present does not have a definitive curing. This therapy requires a neutron source for irradiating the articulation affected. The energy spectra and the intensity of these neutrons are fundamental since these neutrons induce nuclear reactions of capture with Boron-10 inside the articulation and the freely energy of these reactions is transferred at the productive tissue of synovial liquid, annihilating it. In this work it is presented the neutron spectra results obtained with moderator packings of spherical geometry which contains in its center a Pu239 Be source. The calculations were realized through Monte Carlo method. The moderators assayed were light water, heavy water base and the both combination of them. The spectra obtained, the average energy, the neutron total number by neutron emitted by source, the thermal neutron percentage and the dose equivalent allow us to suggest that the moderator packing more adequate is what has a light water thickness 0.5 cm (radius 2 cm) and 24.5 cm heavy water (radius 26.5 cm). (Author)

  5. Multidisc neutron velocity selector

    International Nuclear Information System (INIS)

    The prototype of a velocity selector for neutron monochromatization in the 4-20 A wavelength range is presented. The theoretical background of the multidisc rotor system is given together with a description of the mechanical construction and electronic driving system. The first tests and neutron measurements prove easy handling and excellent parameters. (author) 6 refs.; 7 figs.; 2 tabs

  6. Neutron resonance spectroscopy

    International Nuclear Information System (INIS)

    The present document has been written in order to obtain the diploma 'Habilitation a Diriger des Recherches'. Since this diploma is indispensable to supervise thesis students, I had the intention to write a document that can be useful for someone starting in the field of neutron resonance spectroscopy. Although the here described topics are already described elsewhere, and often in more detail, it seemed useful to have most of the relevant information in a single document. A general introduction places the topic of neutron-nucleus interaction in a nuclear physics context. The large variations of several orders of magnitude in neutron-induced reaction cross sections are explained in terms of nuclear level excitations. The random character of the resonances make nuclear model calculation predictions impossible. Then several fields in physics where neutron-induced reactions are important and to which I have contributed in some way or another, are mentioned in a first synthetic chapter. They concern topics like parity nonconservation in certain neutron resonances, stellar nucleosynthesis by neutron capture, and data for nuclear energy applications. The latter item is especially important for the transmutation of nuclear waste and for alternative fuel cycles. Nuclear data libraries are also briefly mentioned. A second chapter details the R-matrix theory. This formalism is the foundation of the description of the neutron-nucleus interaction and is present in all fields of neutron resonance spectroscopy. (author)

  7. Neutron Star Matter

    CERN Document Server

    Wambach, Jochen

    2013-01-01

    In this presentation I discuss two aspects of the neutron-matter equation of state. One relates to the symmetry energy of nuclear matter and empirical constraints on its slope parameter at saturation density. The second deals with spatially inhomogeneous chiral phases of deconfined quark matter in the inner core of a neutron star.

  8. Prompt Neutrons from Fission

    International Nuclear Information System (INIS)

    A survey is given of the present state of knowledge of the spectrum, angular distribution and number of prompt fission neutrons, as functions of incident neutron energy and individual fragment mass, for low-energy fission. The energy spectrum of prompt neutrons has been found to be of the same form (nearly Maxwellian) for many different types of fission. It has been shown that this type of spectrum is to be expected on the basis of evaporation from moving fragments, and theoretical predictions of the spectrum agree very accurately with experimental data. Some data are now available on the variation of the neutron spectrum with fragment mass and angle of emission. Only recently has it become possible to take accurate data on the angular distribution of the neutrons. It appears that the neutrons have the angular distribution to be expected if emitted almost isotropically from the moving fragments, with a possibility that some small fraction are not emitted in this way, but directly from the fissioning nuclide. Much work has been done on the variation of fission neutron number v with incident neutron energy for neutron-induced fission. The neutron number increases roughly linearly with energy, with a slope of about 0.15 n/MeV. There is now evidence that this slope changes somewhat with energy. This change must be associated with other changes in the-fission process. The most interesting recent discovery concerning fission neutrons is the strong dependence of neutron number on individual fragment mass. The data are being rapidly improved by means of the newer techniques of determining fragment mass yields from velocity and pulse-height data, and of determining neutron yields from cumulative mass yields. There is evidence of similar dependence of neutron yield on fragment mass in a number of cases. It has been suggested that this property is directly connected with the deformability of the fragments, and in particular with the near-spherical shapes of magic

  9. Dosimetry of neutron irradiations

    International Nuclear Information System (INIS)

    Biological dosimetry of neutron irradiation appears to be of great difficulty due to the multiparametric aspect of the relative biological effectiveness and the heterogeneity of the neutron dose distribution. Dosimetry by sodium 24 activation which can be performed by means of portable radiameters appears to be very useful for early triage within the 3 h following neutron irradiation, whereas hematological dosimetry by slope and level analysis of the lymphocyte drop cannot be used in this case. Chromosomic aberration analysis allows to evaluate the neutron dose heterogeneity by the frequency measurement of acentric fragments not originating from the formation of dicentrics or rings. Finally, recent experimental data on large primate models (baboons) have shown that some plasma hemostasia factors appear to be reliable biological indicators and noticeable markers of the prognosis of neutron irradiation

  10. Canada's Neutron Beam Laboratory

    International Nuclear Information System (INIS)

    This paper describes the current and planned activities of Canada's Neutron Beam Laboratory which is managed by the National Research Council of Canada. In 1994, Professor Bertram Brockhouse shared the Nobel Prize in Physics for his pioneering work carried out in this laboratory. He developed neutron scattering as a powerful and versatile tool for investigating materials at the level of molecules and nano structures. The neutron source for this work is Canada's NRU reactor located at the Chalk River Nuclear Laboratories of the Atomic Energy of Canada Limited. This neutron source is also used for the production of medical isotopes, testing of components for the nuclear power stations and neutron scattering experiments on materials

  11. Neutrons against cancer

    Science.gov (United States)

    Dovbnya, A. N.; Kuplennikov, E. L.; Kandybey, S. S.; Krasiljnikov, V. V.

    2014-09-01

    The review is devoted to the analysis and generalization of the research carried out during recent years in industrially advanced countries on the use of fast, epithermal, and thermal neutrons for therapy of malignant tumors. Basic facilities for neutron production used for cancer treatment are presented. Optimal parameters of therapeutic beams are described. Techniques using neutrons of different energy regions are discussed. Results and medical treatment efficiency are given. Comparison of the current state of neutron therapy of tumors and alternative treatments with beams of protons and carbon ions has been conducted. Main attention is given to the possibility of the practical use of accumulated experience of application of neutron beams for cancer therapy.

  12. A Neutron Rem Counter

    International Nuclear Information System (INIS)

    A neutron detector is described which measures the neutron dose rate in rem/h independently of the energy of the neutrons from thermal to 15 MeV. The detector consists of a BF3 proportional counter surrounded by a shield made of polyethylene and boron plastic that gives the appropriate amount of moderation and absorption to the impinging neutrons to obtain rem response. Two different versions have been developed. One model can utilize standard BF3 counters and is suitable for use in installed monitors around reactors and accelerators and the other model is specially designed for use in a portable survey instrument. The neutron rem counter for portable instruments has a sensitivity of 2.4 cps/mrem/h and is essentially nondirectional in response. With correct bias setting the counter is insensitive to gamma exposure up to 200 r/h from Co-60

  13. Neutron production during thunderstorms

    International Nuclear Information System (INIS)

    We have analyzed the neutron fluxes correlated with thunderstorm activity recently measured at mountain altitudes by Tien-Shan, Tibet and Aragats groups. We perform simulations of the photonuclear reactions of gamma rays born in the electron-gamma ray avalanches in the thunderstorm atmosphere and calculate expected count rates of the neutron counters used by 3 groups. Our analysis supported the Tibet group conclusion on the photonuclear nature of thunderstorm-correlated neutrons. The photonuclear reactions of the gamma rays born in the electron-photon avalanches in the thunderstorm atmospheres interacting in the lead producer of a Neutron monitor can provide neutron yield compatible with additional count of NM at least for the largest Thunderstorm Ground Enhancements (TGEs).

  14. THERMAL NEUTRON BACKSCATTER IMAGING.

    Energy Technology Data Exchange (ETDEWEB)

    VANIER,P.; FORMAN,L.; HUNTER,S.; HARRIS,E.; SMITH,G.

    2004-10-16

    Objects of various shapes, with some appreciable hydrogen content, were exposed to fast neutrons from a pulsed D-T generator, resulting in a partially-moderated spectrum of backscattered neutrons. The thermal component of the backscatter was used to form images of the objects by means of a coded aperture thermal neutron imaging system. Timing signals from the neutron generator were used to gate the detection system so as to record only events consistent with thermal neutrons traveling the distance between the target and the detector. It was shown that this time-of-flight method provided a significant improvement in image contrast compared to counting all events detected by the position-sensitive {sup 3}He proportional chamber used in the imager. The technique may have application in the detection and shape-determination of land mines, particularly non-metallic types.

  15. Fission neutron statistical emission

    International Nuclear Information System (INIS)

    The statistical model approach FINESSE (FIssion NEutronS' Statistical Emission) for the description of fission neutron multiplicities, energy spectra and angular distributions is described. Based on an extended Weisskopf ansatz and on a realistic temperature distribution it provides a fragment mass number dependent description of fission neutron data. Model parameters (optical potential, n/γ competition) were fixed on the basis of the 252Cf(sf) (nuclear data standard). Combined with a phenomenological fission model for predicting relevant fragment data as function of asymmetry. FINESSE can be applied to any fission reaction of actinides in the Th-Cf region without further parameter adjustment. Results are presented for 252Cf(sf) and neutron induced fission of 235U, 239Pu, 232Th. Effects of multiple-chance fission are discussed for 232Th(n,xnf) reacation. (author). 46 refs, 11 figs

  16. Fast neutrons dosimetry

    International Nuclear Information System (INIS)

    A proton recoil technique has been developed for inducing thermoluminescence with incident fast neutrons. CaF2 was used as the TL phosphor, and cane sugar and polyethylene were used as proton radiators. The phosphor and the hydrogeneous material powders were well mixed, encapsulated in glass tubes and exposed to Am-Be sources, resulting in recoils from incident fast neutrons of energy between 0,25 and 11,25 MeV. The intrinsic response of pure CaF2 to fast neutrons without a hydrogeneous radiator was checked by using LiF (TLD-700). Glow curves were recorded from room temperature up to 3500C after different doses of neutrons and gamma rays of 60Co. First collision dose due to fast neutrons in tissue like materials such as cane sugar and polyethylene was also calculated

  17. Neutron Stars and Pulsars

    CERN Document Server

    Becker, Werner

    2009-01-01

    Neutron stars are the most compact astronomical objects in the universe which are accessible by direct observation. Studying neutron stars means studying physics in regimes unattainable in any terrestrial laboratory. Understanding their observed complex phenomena requires a wide range of scientific disciplines, including the nuclear and condensed matter physics of very dense matter in neutron star interiors, plasma physics and quantum electrodynamics of magnetospheres, and the relativistic magneto-hydrodynamics of electron-positron pulsar winds interacting with some ambient medium. Not to mention the test bed neutron stars provide for general relativity theories, and their importance as potential sources of gravitational waves. It is this variety of disciplines which, among others, makes neutron star research so fascinating, not only for those who have been working in the field for many years but also for students and young scientists. The aim of this book is to serve as a reference work which not only review...

  18. Optical polarizing neutron devices designed for pulsed neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, M.; Kurahashi, K.; Endoh, Y. [Tohoku Univ, Sendai (Japan); Itoh, S. [National Lab. for High Energy Physics, Tsukuba (Japan)

    1997-09-01

    We have designed two polarizing neutron devices for pulsed cold neutrons. The devices have been tested at the pulsed neutron source at the Booster Synchrotron Utilization Facility of the National Laboratory for High Energy Physics. These two devices proved to have a practical use for experiments to investigate condensed matter physics using pulsed cold polarized neutrons.

  19. NEUTRON WAVE OPTICS STUDIED WITH ULTRACOLD NEUTRONS

    OpenAIRE

    Steyerl, A.

    1984-01-01

    The paper reports experiments demonstrating or utilizing the wave properties of neutrons with wavelengths of about 100 nm. The significant effects of gravity are discussed, and special features of the flight parabola have been used in designing high-resolution instruments and image-forming systems.

  20. Tracking fast neutrons

    International Nuclear Information System (INIS)

    Both neutron absorption and elastic scattering can be used to measure neutron momentum. Based on elastic collisions, the linear momentum of a fast neutron can be measured from as few as two consecutive recoil ion tracks plus the vertex position of the third collision, or ‘two and half’ ion tracks. If the time delay between the first two consecutive ion tracks is also measured, the number of ion tracks can be reduced to one and a half. The angular and magnitude resolutions are limited by ion range straggling to about 10%. Multi-wire proportional chambers and light-field imaging can be used for fast neutron tracking. Light-field imaging is free of charge-diffusion-induced image blur, but the limited number of photons available can be a challenge. 1H, 2H and 3He could be used for the initial development of fast neutron trackers based on light-field imaging. -- Highlights: • We describe the basic principle of fast neutron tracking through elastic collisions and absorption; • We calculate tracking errors, which are limited by ion range straggling. • Multi-wire proportional chamber and light field imaging are discussed for fast neutron tracking; • Time projection of ion tracks can be achieved by detecting photons

  1. Versatile neutron NDA

    Energy Technology Data Exchange (ETDEWEB)

    DeVolpi, A.

    1995-07-01

    Non-destructive analysis (NDA) of bulk samples is a major tool in international safeguards and domestic MC&A. Yet, enhancements are needed to reduce inspection time, financial cost, and radiation exposure-while improving reliability and accuracy-particularly for mixtures of fissile and fertile isotopes. Perhaps the greatest remaining direction for NDA improvement is the development of a single controllable neutron source that would add versatility and capability. One of the primary prospects is a switchable radioactive neutron source (SRNS) that has been under advanced-concept development at Argonne with DOE funding. The SRNS would be in a sealed capsule that can be remotely switched on and off, or pulsed at a controllable rate. Li({alpha}, n) or Be({alpha}, n) reactions could give a choice of sub-threshold or hard-spectrum neutrons at yields ranging from 10{sup 4}/s to more than 10{sup 8}s. The SRNS would provide improved capabilities for (1) simultaneous or alternating interrogation with fast and slow neutrons, (2) detection of the first few seconds of delayed neutrons, (3) measurements in the presence of high neutron and/or gamma background, and (4) inspection of heterogeneous materials. When the neutrons are switched off, the source would be portable with vastly reduced shielding. Proof-of-concept with a single switchable plate has been established under laboratory conditions.

  2. Neutron dosimetry in mixed fields with monoblock neutron spectrometer

    International Nuclear Information System (INIS)

    Full text: The multi-sphere method of neutron spectrometry or namely Bonner spheres neutron spectrometry is currently playing an increasing role in the mixed radiation field measurements. The growing popularity of this methodology is caused by its relative availability, simplicity of measurement in a wide energy range, high sensitivity and satisfactory gamma-ray suppression. These qualities allow the usage of multi-sphere neutron spectrometers for adequate characterization of neutron field, particularly reliable measurements of neutron dose rate. However, the main difficulties in the application of this kind of neutron detector are the perturbation of the neutron field, caused by the detector itself, and the complex procedure required for unfolding the neutron spectrum. Furthermore, it is necessary to perform a relatively high number of measurements, one for each spherical moderator (as a rule, 5-7 pieces). This in turn may require a dedicated source monitoring system, otherwise significant errors may occur. These requirements hamper the application of the multi-sphere spectrometry method to pulsed neutron sources, for example. Other difficulties occur in the characterization of reactor neutron beams, in case the beam diameter is smaller than those of the spherical moderators. In this situation it is necessary to carry out a beam scanning and integrate the acquired data. To improve the methodology of neutron field parameter measurement the Monoblock Neutron Spectrometer (MNS) has been developed recently. The basic idea of the novel detector is to determine the neutron energy spectrum by unfolding a set of count rates from thermal neutron detectors located at different depths in the common polyethylene moderator. The unfolding algorithms for neutron spectrum and neutron dose rates have been specifically improved for operation with MNS. The testing results with well-know neutron reference fields and reactor neutron beam are presented. The application of MNS for

  3. Neutron-Phonon Interaction in Neutron Star Crusts

    OpenAIRE

    Sedrakian, Armen

    1998-01-01

    The phonon spectrum of Coulomb lattice in neutron star crusts above the neutron drip density is affected by the interaction with the ambient neutron Fermi-liquid. For the values of the neutron-phonon coupling constant in the range $0.1 \\le \\lambda \\le 1$ an appreciable renormalization of the phonon spectrum occurs which can lead to a lattice instability manifested in an exponential growth of the density fluctuations. The BCS phonon exchange mechanism of superconductivity leads to neutron pair...

  4. ${}^3$H production via neutron-neutron-deuteron recombination

    OpenAIRE

    Deltuva, A; Fonseca, A.C.

    2013-01-01

    We study the recombination of two neutrons and deuteron into neutron and ${}^3$H using realistic nucleon-nucleon potential models. Exact Alt, Grassberger, and Sandhas equations for the four-nucleon transition operators are solved in the momentum-space framework using the complex-energy method with special integration weights. We find that at astrophysical or laboratory neutron densities the production of ${}^3$H via the neutron-neutron-deuteron recombination is much slower as compared to the ...

  5. The neutron radii of Lead and neutron stars

    OpenAIRE

    Horowitz, Charles J.; Piekarewicz, Jorge

    2001-01-01

    A new relation between the neutron skin of a heavy nucleus and the radius of a neutron star is proposed: the larger the neutron skin of the nucleus the larger the radius of the star. Relativistic models that reproduce a variety of ground-state observables can not determine uniquely the neutron skin of a heavy nucleus. Thus, a large range of neutron skins is generated by supplementing the models with nonlinear couplings between isoscalar and isovector mesons. We illustrate how the correlation ...

  6. Fusion Based Neutron Sources for Security Applications: Neutron Techniques

    OpenAIRE

    Albright, S.; Seviour, Rebecca

    2014-01-01

    The current reliance on X-Rays and intelligence for na- tional security is insufficient to combat the current risks of smuggling and terrorism seen on an international level. There are a range of neutron based security techniques which have the potential to dramatically improve national security. Neutron techniques can be broadly grouped into neutron in/neutron out and neutron in/photon out tech- niques. The use of accelerator based fusion devices will potentially enable to wide spread applic...

  7. Neutron - Mirror Neutron Oscillations: How Fast Might They Be?

    OpenAIRE

    Berezhiani, Zurab; Bento, Luis

    2005-01-01

    We discuss the phenomenological implications of the neutron (n) oscillation into the mirror neutron (n'), a hypothetical particle exactly degenerate in mass with the neutron but sterile to normal matter. We show that the present experimental data allow a maximal n-n' oscillation in vacuum with a characteristic time $\\tau$ much shorter than the neutron lifetime, in fact as small as 1 sec. This phenomenon may manifest in neutron disappearance and regeneration experiments perfectly accessible to...

  8. Los Alamos National Laboratory neutron-neutron scattering program

    International Nuclear Information System (INIS)

    A theoretical and experimental program is underway to determine the feasibility of a measurement of the neutron-neutron scattering cross section of 10 to 12% uncertainty using small-angle, low center-of-mass energy, colliding neutron beams derived from a fusion-fission nuclear source. The neutron-neutron scattering length would be inferred from the measured cross sections. The general concept of the experiments and progress are discussed

  9. Influence of neutron scattering on fission neutron spectrum measurement

    International Nuclear Information System (INIS)

    The study of the influence of neutron scattering by the surrounding medium and fragment detector on fission neutron spectrum measurement with time-of-flight (TOF) method has been carried out. The scattering by air and the walls of the measuring room was determined by both experiment and Monte Carlo simulation. It was found that the neutron scattering influence on the fission neutron spectrum is rather essential and can noticeably change the shape of the fission neutron spectra. (4 figs.)

  10. Neutron production, shielding and activation

    International Nuclear Information System (INIS)

    This chapter contains information on neutron cross-sections, production, spectra and yields; detection and detectors; shielding with various materials, particularly with ordinary concrete; and neutron activation products of interest to health physicists. Neutron energy terminology as well as neutron energy spectrum calculations are included

  11. The neutron channeling phenomenon.

    Science.gov (United States)

    Khanouchi, A; Sabir, A; Boulkheir, M; Ichaoui, R; Ghassoun, J; Jehouani, A

    1997-01-01

    Shields, used for protection against radiation, are often pierced with vacuum channels for passing cables and other instruments for measurements. The neutron transmission through these shields is an unavoidable phenomenon. In this work we study and discuss the effect of channels on neutron transmission through shields. We consider an infinite homogeneous slab, with a fixed thickness (20 lambda, with lambda the mean free path of the neutron in the slab), which contains a vacuum channel. This slab is irradiated with an infinite source of neutrons on the left side and on the other side (right side) many detectors with windows equal to 2 lambda are placed in order to evaluate the neutron transmission probabilities (Khanouchi, A., Aboubekr, A., Ghassoun, J. and Jehouani, A. (1994) Rencontre Nationale des Jeunes Chercheurs en Physique. Casa Blanca Maroc; Khanouchi, A., Sabir, A., Ghassoun, J. and Jehouani, A. (1995) Premier Congré International des Intéractions Rayonnements Matière. Eljadida Maroc). The neutron history within the slab is simulated by the Monte Carlo method (Booth, T. E. and Hendricks, J. S. (1994) Nuclear Technology 5) and using the exponential biasing technique in order to improve the Monte Carlo calculation (Levitt, L. B. (1968) Nuclear Science and Engineering 31, 500-504; Jehouani, A., Ghassoun, J. and Aboubker, A. (1994) In Proceedings of the 6th International Symposium on Radiation Physics, Rabat, Morocco). Then different geometries of the vacuum channel have been studied. For each geometry we have determined the detector response and calculated the neutron transmission probability for different detector positions. This neutron transmission probability presents a peak for the detectors placed in front of the vacuum channel. This study allowed us to clearly identify the neutron channeling phenomenon. One application of our study is to detect vacuum defects in materials. PMID:9463884

  12. Fruits of neutron research

    International Nuclear Information System (INIS)

    Car windshields that don't break during accidents and jets that fly longer without making a refueling stop. Compact discs, credit cards, and pocket calculators. Refrigerator magnets and automatic car window openers. Beach shoes, food packaging, and bulletproof vests made of tough plastics. The quality and range of consumer products have improved steadily since the 1970s. One of the reasons: neutron research. Industries, employing neutron scattering techniques, to study materials properties, to act as diagnostics in tracing system performance, or as sources for radioactive isotopes used in medical fields for diagnostics or treatment, have all benefited from the fruits of advanced work with neutron sources

  13. METHOD OF PRODUCING NEUTRONS

    Science.gov (United States)

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

    1964-01-14

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

  14. International Neutron Radiography Newsletter

    OpenAIRE

    Domanus, Joseph Czeslaw

    1986-01-01

    At the First World Conference on Neutron Radiography i t was decided to continue the "Neutron Radiography Newsletter", published previously by J.P. Barton, as the "International Neutron Radiography Newsletter" (INRNL), with J.C. Doraanus as editor. The British Journal of Non-Destructive Testing (BJNDT) has agreed to publish the INRNL in i t s column "NDT Bookcase". The Revue Practique de Control Industriel has also agreed to publish the French version of the INRNL. Up t i l l now 12 issues of...

  15. Coupled moderator neutronics

    International Nuclear Information System (INIS)

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

  16. Neutron scattering in liquids

    Energy Technology Data Exchange (ETDEWEB)

    Barocchi, F. [Florence Univ. (Italy). Ist. di Fisica

    1996-12-31

    Together with X-rays, thermal neutrons are the ideal probe to study the microscopic structure of condensed matter, however the precision attainable usually with neutrons for the measurement of atomic position correlation functions in liquids is, at least, one order of magnitude better than for X-rays. In order to measure properly the microscopic dynamics a wide range of momentum transfer with corresponding energy transfer must be available in the range of liquid state excitations. This again is only attainable, with good resolution, with neutrons. (author) 7 figs., 3 refs.

  17. Neutrons in soft matter

    CERN Document Server

    Imae, Toyoko; Furusaka, Michihiro; Torikai, Naoya

    2011-01-01

    Neutron and synchrotron facilities, which are beyond the scale of the laboratory, and supported on a national level in countries throughout the world.  These tools for probing micro- and nano-structure research and on fast dynamics research of atomic location in materials have been key in the development of new polymer-based materials. Different from several existing professional books on neutron science, this book focuses on theory, instrumentation, an applications. The book is divided into five parts: Part 1 describes the underlying theory of neutron scattering. Part 2 desc

  18. Hyperons in neutron stars

    Directory of Open Access Journals (Sweden)

    Tetsuya Katayama

    2015-07-01

    Full Text Available Using the Dirac–Brueckner–Hartree–Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of 2.08M⊙, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

  19. Hyperons in neutron stars

    CERN Document Server

    Katayama, Tetsuya

    2015-01-01

    Using the Dirac-Brueckner-Hartree-Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of $2.08\\,M_{\\odot}$, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

  20. Magnetic trapping of ultracold neutrons

    OpenAIRE

    Brome, C. R.; Butterworth, J. S.; Dzhosyuk, S. N.; Mattoni, C. E. H.; McKinsey, D. N.; Doyle, J. M.; Huffman, P. R.; Dewey, M. S.; Wietfeldt, F. E.; Golub, R.; Habicht, K.; Greene, G. L.; Lamoreaux, S. K.; Coakley, K. J.

    2001-01-01

    Three-dimensional magnetic confinement of neutrons is reported. Neutrons are loaded into an Ioffe-type superconducting magnetic trap through inelastic scattering of cold neutrons with 4He. Scattered neutrons with sufficiently low energy and in the appropriate spin state are confined by the magnetic field until they decay. The electron resulting from neutron decay produces scintillations in the liquid helium bath that results in a pulse of extreme ultraviolet light. This light is frequency dow...

  1. Euratom Neutron Radiography Working Group

    OpenAIRE

    Domanus, Joseph Czeslaw

    1986-01-01

    In 1979 a Neutron Radiography Working Group (NRWG) was constituted within Buratom with the participation of all centers within the European Community at which neutron facilities were available. The main purpose of NRWG was to standardize methods and procedures used in neutron radiography of nuclear reactor fuel as well as establish standards for radiographic image quality of neutron radiographs. The NRWG meets once a year in each of the neutron radiography centers to review the progress made ...

  2. Neutron spectra produced by moderating an isotopic neutron source

    International Nuclear Information System (INIS)

    A Monte Carlo study has been carried out to determine the neutron spectra produced by an isotopic neutron source inserted in moderating media. Most devices used for radiation protection have a response strongly dependent on neutron energy. ISO recommends several neutron sources and monoenergetic neutron radiations, but actual working situations have broad spectral neutron distributions extending from thermal to MeV energies, for instance, near nuclear power plants, medical applications accelerators and cosmic neutrons. To improve the evaluation of the dosimetric quantities, is recommended to calibrate the radiation protection devices in neutron spectra which are nearly like those met in practice. In order to complete the range of neutron calibrating sources, it seems useful to develop several wide spectral distributions representative of typical spectra down to thermal energies. The aim of this investigation was to use an isotopic neutron source in different moderating media to reproduce some of the neutron fields found in practice. MCNP code has been used during calculations, in these a 239PuBe neutron source was inserted in H2O, D2O and polyethylene moderators. Moderators were modeled as spheres and cylinders of different sizes. In the case of cylindrical geometry the anisotropy of resulting neutron spectra was calculated from 0 to 2. From neutron spectra dosimetric features were calculated. MCNP calculations were validated by measuring the neutron spectra of a 239PuBe neutron source inserted in a H2O cylindrical moderator. The measurements were carried out with a multisphere neutron spectrometer with a 6LiI(Eu) scintillator. From the measurements the neutron spectrum was unfolded using the BUNKIUT code and the UTA4 response matrix. Some of the moderators with the source produce a neutron spectrum close to spectra found in actual applications, then can be used during the calibration of radiation protection devices

  3. Astrophysical problems of neutron stars

    International Nuclear Information System (INIS)

    Full text: Due to the recent discovery of 2 solar mass neutron stars in a neutron star - white dwarf binary, many soft neutron star equations of states are ruled out. On the other hand, all well-measured neutron star masses in double neutron star binaries are still below 1.5 solar mass. In this review talk, we would like to summarize the current status of neutron star mass observations and discuss the possibility of supercritical accretion during the neutron star binary evolution. We argue that the fate of the supercritical accretion strongly depends on the type of neutron star companion. The first-born neutron star in neutron star-white dwarf binaries can accrete significant amount of matter after its formation. Consequently, neutron star masses in neutron star-white dwarf binaries can be significantly higher than those of fresh neutron stars. On the other hand, neutron stars in double neutron star binaries that are observed don't have enough time to accrete and remain more or less the same as they are born. (author)

  4. Neutrons for industry

    International Nuclear Information System (INIS)

    Neutrons are a unique tool for materials science, from hard to soft matter. This uniqueness relies on the privileged penetration of neutrons in any kind of matter, their particular contrast for different elements/isotopes, their capability to characterize in situ, in operation and in real time. Often enough neutron research explains the functionality of materials and work pieces by their atomistic foundation and opens the way for optimization of the functionality. In this paper the author reviews some new applications of neutron irradiation in industry: homogenous doping for power electronics; the selection of the right candidates for hydrogen storage materials; the optimization of Li-ion batteries and organic solar cells; the 3-dimensional determination of residual stresses without damaging the specimen. Concerning medicine there were some advances for the production of some isotopes like Lu177 or Mo99-Tc99m

  5. Instruments for neutron scattering

    International Nuclear Information System (INIS)

    The wide variety of science that can be presented with neutron scattering essentially boils down to determine two vectors, the momentum k of the neutron before it hits the sample and after it leaves the sample. All experimentally obtainable information is contained in the probability distribution W(k,k') of a neutron to undergo scattering takes it from k to k'. In this paper we will introduce the principles and concepts to understand what one is doing if one perform an experiment on a certain instrument We will describe the components of which almost all neutron scattering instruments are made up and their functions and show how these components can be combined to contribute in the best possible way to the solution of questions in a large number of scientific areas

  6. Neutron personnel dosimetry

    International Nuclear Information System (INIS)

    The current state-of-the-art in neutron personnel dosimetry is reviewed. Topics covered include dosimetry needs and alternatives, current dosimetry approaches, personnel monitoring devices, calibration strategies, and future developments

  7. The intense neutron generator

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, W.B

    1966-07-01

    The presentation discusses both the economic and research contexts that would be served by producing neutrons in gram quantities at high intensities by electrical means without uranium-235. The revenue from producing radioisotopes is attractive. The array of techniques introduced by the multipurpose 65 megawatt Intense Neutron Generator project includes liquid metal cooling, superconducting magnets for beam bending and focussing, super-conductors for low-loss high-power radiofrequency systems, efficient devices for producing radiofrequency power, plasma physics developments for producing and accelerating hydrogen, ions at high intensity that are still far out from established practice, a multimegawatt high voltage D.C. generating machine that could have several applications. The research fields served relate principally to materials science through neutron-phonon and other quantum interactions as well as through neutron diffraction. Nuclear physics is served through {mu}-, {pi}- and K-meson production. Isotope production enters many fields of applied research. (author)

  8. Neutron resonance averaging

    International Nuclear Information System (INIS)

    The principles of resonance averaging as applied to neutron capture reactions are described. Several illustrations of resonance averaging to problems of nuclear structure and the distribution of radiative strength in nuclei are provided. 30 refs., 12 figs

  9. Cylindrical neutron generator

    Science.gov (United States)

    Leung, Ka-Ngo

    2008-04-22

    A cylindrical neutron generator is formed with a coaxial RF-driven plasma ion source and target. A deuterium (or deuterium and tritium) plasma is produced by RF excitation in a cylindrical plasma ion generator using an RF antenna. A cylindrical neutron generating target is coaxial with the ion generator, separated by plasma and extraction electrodes which contain many slots. The plasma generator emanates ions radially over 360.degree. and the cylindrical target is thus irradiated by ions over its entire circumference. The plasma generator and target may be as long as desired. The plasma generator may be in the center and the neutron target on the outside, or the plasma generator may be on the outside and the target on the inside. In a nested configuration, several concentric targets and plasma generating regions are nested to increase the neutron flux.

  10. Neutron irradiation of seeds

    International Nuclear Information System (INIS)

    Neutrons are a valuable type of ionizing radiation for seed irradiation and radiobiological studies and for inducing mutations in crop plants. In experiments where neutrons are used in research reactors for seed irradiation it is difficult to measure the dose accurately and therefore to establish significant comparisons between experimental results obtained in various reactors and between repeated experiments in the same reactor. A further obstacle lies in the nature and response of the seeds themselves and the variety of ways in which they are exposed in reactors. The International Atomic Energy Agency decided to initiate international efforts to improve and standardize methods of exposing seeds in research reactors and of measuring and reporting the neutron dose. For this purpose, an International Neutron Seed Irradiation Programme has been established. The present report aims to give a brief but comprehensive picture of the work so far done in this programme. Refs, figs and tabs

  11. Intense pulsed neutron sources

    Energy Technology Data Exchange (ETDEWEB)

    Kustom, R.L.

    1981-01-01

    Accelerator requirements for pulsed spallation neutron sources are stated. Brief descriptions of the Argonne IPNS-I, the Japanese KENS, Los Alamos Scientific Laboratory WNR/PSR, the Rutherford Laboratory SNS, and the West German SNQ facilities are presented.

  12. Neutron signal transfer analysis

    CERN Document Server

    Pleinert, H; Lehmann, E

    1999-01-01

    A new method called neutron signal transfer analysis has been developed for quantitative determination of hydrogenous distributions from neutron radiographic measurements. The technique is based on a model which describes the detector signal obtained in the measurement as a result of the action of three different mechanisms expressed by signal transfer functions. The explicit forms of the signal transfer functions are determined by Monte Carlo computer simulations and contain only the distribution as a variable. Therefore an unknown distribution can be determined from the detector signal by recursive iteration. This technique provides a simple and efficient tool for analysis of this type while also taking into account complex effects due to the energy dependency of neutron interaction and single and multiple scattering. Therefore this method provides an efficient tool for precise quantitative analysis using neutron radiography, as for example quantitative determination of moisture distributions in porous buil...

  13. Neutrons from Piezonuclear Reactions

    CERN Document Server

    Cardone, F; Mignani, R; Perconti, W; Petrucci, A; Rosetto, F; Spera, G

    2007-01-01

    We report the results obtained by cavitating water solutions of iron salts (iron chloride and iron nitrate) with different concentrations at different ultrasound powers. In all cases we detected a neutron radiation well higher than the background level. The neutron production is perfectly reproducible and can at some extent be controlled. These evidences for neutron emission generated by cavitation support some preliminary clues for the possibility of piezonuclear reactions (namely nuclear reactions induced by pressure and shock waves) obtained in the last ten years. We have been able for the first time to state some basic features of such a neutron emission induced by cavitation, namely: 1) a marked threshold behavior in power, energy and time; 2) its occurring without a concomitant production of gamma radiation.

  14. Directionally positionable neutron beam

    International Nuclear Information System (INIS)

    Disclosed is apparatus for forming and directionally positioning a neutron beam. The apparatus includes an enclosed housing rotatable about a first axis with a neutron source axially positioned on the axis of rotation of the enclosed housing but not rotating with the housing. The rotatable housing is carried by a vertically positionable arm carried on a mobile transport. A collimator is supported by the rotatable housing and projects into the housing to orientationally position its inlet window at an adjustably fixed axial and radial spacing from the neutron source so that rotation of the enclosed housing causes the inlet window to rotate about a circle which is a fixed axial distance from the neutron source and has the axis of rotation of the housing as its center. (author)

  15. Neutron phase spin echo

    Science.gov (United States)

    Piegsa, Florian M.; Hautle, Patrick; Schanzer, Christian

    2016-04-01

    A novel neutron spin resonance technique is presented based on the well-known neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of 4 ×10-7 can be resolved, corresponding to an energy resolution of better than 3 neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing energy resolutions in the 10 peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  16. Neutron phase spin echo

    CERN Document Server

    Piegsa, Florian M; Schanzer, Christian

    2016-01-01

    A novel neutron spin resonance technique is presented based on the well-know neutron spin echo method. In a first proof-of-principle measurement using a monochromatic neutron beam, it is demonstrated that relative velocity changes of down to a precision of $4 \\times 10^{-7}$ can be resolved, corresponding to an energy resolution of better than 3~neV. Currently, the sensitivity is only limited by counting statistics and not by systematic effects. An improvement by another two orders of magnitude can be achieved with a dedicated setup, allowing for energy resolutions in the 10~peV regime. The new technique is ideally suited for investigations in the field of precision fundamental neutron physics, but will also be beneficial in scattering applications.

  17. Neutron scattering in dimers

    DEFF Research Database (Denmark)

    Gudel, H. U.; Furrer, A.; Kjems, Jørgen

    1986-01-01

    Insulating compounds containing dimers of transition metal and rare earth ions have been studied by inelastic neutron scattering (INS). Energy splittings can be directly determined, and the corresponding parameters are easily extracted from the experimental data. The intensities of dimer...

  18. Decoherence Free Neutron Interferometry

    CERN Document Server

    Pushin, Dmitry A; Cory, David G

    2016-01-01

    Perfect single-crystal neutron interferometers are adversely sensitive to environmental disturbances, particularly mechanical vibrations. The sensitivity to vibrations results from the slow velocity of thermal neutrons and the long measurement time that are encountered in a typical experiment. Consequently, to achieve a good interference solutions for reducing vibration other than those normally used in optical experiments must be explored. Here we introduce a geometry for a neutron interferometer that is less sensitive to low-frequency vibrations. This design may be compared with both dynamical decoupling methods and decoherence-free subspaces that are described in quantum information processing. By removing the need for bulky vibration isolation setups, this design will make it easier to adopt neutron interferometry to a wide range of applications and increase its sensitivity.

  19. Neutrons in natural environment

    International Nuclear Information System (INIS)

    A detecting system for environmental neutrons has to be characterized by a very low inherent background. The details are reported of measuring the background of a 3He proportional counter in a polythene sphere in the Asse salt mine. A spherical counter with 40 mm ext. diameter, filled with 100 kPa 3He and 53 kPa Xe was used. The inherent background of the counter was found to be less then 1 nSv per 24 hours, being less than 1% of the natural neutron radiation level at the ground level. The ambient dose equivalent due to environmental neutrons was estimated at 100-200 nSv per 24 hours. A 3He proportional counter in a polythene sphere was thus found to be sufficiently sensitive to estimate the neutron component at environmental levels. (A.K.)

  20. The intense neutron generator

    International Nuclear Information System (INIS)

    The presentation discusses both the economic and research contexts that would be served by producing neutrons in gram quantities at high intensities by electrical means without uranium-235. The revenue from producing radioisotopes is attractive. The array of techniques introduced by the multipurpose 65 megawatt Intense Neutron Generator project includes liquid metal cooling, superconducting magnets for beam bending and focussing, super-conductors for low-loss high-power radiofrequency systems, efficient devices for producing radiofrequency power, plasma physics developments for producing and accelerating hydrogen, ions at high intensity that are still far out from established practice, a multimegawatt high voltage D.C. generating machine that could have several applications. The research fields served relate principally to materials science through neutron-phonon and other quantum interactions as well as through neutron diffraction. Nuclear physics is served through μ-, π- and K-meson production. Isotope production enters many fields of applied research. (author)

  1. Pulsed spallation Neutron Sources

    International Nuclear Information System (INIS)

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology

  2. Pulsed spallation neutron sources

    International Nuclear Information System (INIS)

    This paper reviews the early history of pulsed spallation neutron source development ar Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provide a few examples of applications in fundamental condensed matter physics, materials science and technology

  3. Neutrons and fusion

    International Nuclear Information System (INIS)

    The production of energy from fusion reactions does not require neutrons in the fundamental sense that they are required in a fission reactor. Nevertheless, the dominant fusion reaction, that between deuterium and tritium, yields a 14 MeV neutron. To contrast a fusion reactor based on this reaction with the fission case, 3 x 1020 such neutrons produced per gigawatt of power. This is four times as many neutrons as in an equivalent fission reactor and they carry seven times the energy of the fission neutrons. Thus, they dominate the energy recovery problem and create technological problems comparable to the original plasma confinement problem as far as a practical power producing device is concerned. Further contrasts of the fusion and fission cases are presented to establish the general role of neutrons in fusion devices. Details of the energy deposition processes are discussed and those reactions necessary for producing additional tritium are outlined. The relatively high energy flux with its large intensity will activate almost any materials of which the reactor may be composed. This activation is examined from the point of view of decay heat, radiological safety, and long-term storage. In addition, a discussion of the deleterious effects of neutron interactions on materials is given in some detail; this includes the helium and hydrogen producing reactions and displacement rate of the lattice atoms. The various materials that have been proposed for structural purposes, for breeding, reflecting, and moderating neutrons, and for radiation shielding are reviewed from the nuclear standpoint. The specific reactions of interest are taken up for various materials and finally a report is given on the status and prospects of data for fusion studies

  4. Teaching neutron diffusion theory

    International Nuclear Information System (INIS)

    A method has been developed of introducing to, in particular, engineering students, neutron diffusion theory and the relevant one-group neutron equations. This new approach to Fick's law suggests a concise, speedy and physically-based method of introducing the subject which is seen to encompass a wider class of spatially dependent problems and which offers an alternative method of introducing boundary continuity conditions. (U.K.)

  5. Neutron Compton Scattering

    OpenAIRE

    Watson, Greg

    1996-01-01

    Neutron Compton scattering measurements have the potential to provide direct information about atomic momentum distributions and adiabatic energy surfaces in condensed matter. First applied to measuring the condensate fraction in superfluid helium, the technique has recently been extended to study a variety of classical and quantum liquids and solids. This article reviews the theoretical background for the interpretation of neutron Compton scattering, with emphasis on studies of solids.

  6. Neutron-Proton Collisions

    OpenAIRE

    Di Grezia, E.

    2011-01-01

    A theoretical model describing neutron-proton scattering developed by Majorana as early as in 1932, is discussed in detail with the experiments that motivated it. Majorana using collisions' theory, obtained the explicit expression of solutions of wave equation of the neutron-proton system. In this work two different models, the unpublished one of Majorana and the contemporary work of Massey, are studied and compared.

  7. Pulsed spallation Neutron Sources

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, J.M. [Argonne National Lab., IL (United States)

    1994-12-31

    This paper reviews the early history of pulsed spallation neutron source development at Argonne and provides an overview of existing sources world wide. A number of proposals for machines more powerful than currently exist are under development, which are briefly described. The author reviews the status of the Intense Pulsed Neutron Source, its instrumentation, and its user program, and provides a few examples of applications in fundamental condensed matter physics, materials science and technology.

  8. Neutron scattering in dimers

    DEFF Research Database (Denmark)

    Gudel, H. U.; Furrer, A.; Kjems, Jørgen

    Insulating compounds containing dimers of transition metal and rare earth ions have been studied by inelastic neutron scattering (INS). Energy splittings can be directly determined, and the corresponding parameters are easily extracted from the experimental data. The intensities of dimer excitati......Insulating compounds containing dimers of transition metal and rare earth ions have been studied by inelastic neutron scattering (INS). Energy splittings can be directly determined, and the corresponding parameters are easily extracted from the experimental data. The intensities of dimer...

  9. Introduction to neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, W.E. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

    1996-11-01

    We give here an introduction to the theoretical principles of neutron scattering. The relationship between scattering- and correlation-functions is particularly emphasized. Within the framework of linear response theory (justified by the weakness of the basic interaction) the relation between fluctuation and dissipation is discussed. This general framework explains the particular power of neutron scattering as an experimental method. (author) 4 figs., 4 refs.

  10. Neutron measuring device

    International Nuclear Information System (INIS)

    The device of the present invention concerns measurement for neutrons in a tokamak type thermonuclear device and it can measure total amount of generated neutrons accurately throughout the operation period even if an error is caused in counted values by plasma disruption. That is, the device comprises (1) a means for detecting presence or absence of occurrence of plasma disruption and the time for the initiation of the occurrence, (2) a first data processing means for processing detection signals, (3) a means for detecting neutrons generated in plasmas and (4) a second data processing means for calculating integrated values for the number of neutrons generated from the start to the completion of electric discharge when no disruption occurs and calculating integrated values for the number of generated neutrons from the start of electric discharge to the time at the initiation of occurrence of the disruption when disruption is present. In the thus constituted device, even if an error is caused by frequent occurrence of plasma disruption, total time integrated amount of neutrons generated in the plasmas can be measured accurately. (I.S.)

  11. Opal neutron beams shutters

    International Nuclear Information System (INIS)

    Full text: The Opal Reactor has five beam tubes for neutron beams. Of these 5 tubes, two come from a cold neutron source, another two from thermal sources, and a fifth is ready for a future hot neutron source. Neutron guides come from the cold and thermal beam tubes. Neutron beams are enabled/disabled through shutters located inside the reactor pool's radial shield. These shutters were specially designed by INVAP for the OPAL reactor. They comprise fixed and movable shields. The movable part allows neutron beam enabling or disabling. The design of these shutters demanded the construction of prototypes that were further submitted to comprehensive tests to be qualified in light of the strict movement precision and high reliability requirements involved. The shielding material - a plastic and steel mix - was also specifically designed for this facility. The design required great efforts as to shield calculation and energy deposition. A heat removal system was designed to dissipate the energy absorbed by the shields. The cold and thermal beam shutters are built following a single vertical axis design. The hot shutter, due to different requirements, was designed with a horizontal axis

  12. Neutron scattering in Australia

    International Nuclear Information System (INIS)

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains

  13. Neutron beam applications

    International Nuclear Information System (INIS)

    For the materials science by neutron technique, the development of the various complementary neutron beam facilities at horizontal beam port of HANARO and the techniques for measurement and analysis has been performed. High resolution powder diffractometer, after the installation and performance test, has been opened and used actively for crystal structure analysis, magnetic structure analysis, phase transition study, etc., since January 1998. The main components for four circle diffractometer were developed and, after performance test, it has been opened for crystal structure analysis and texture measurement since the end of 1999. For the small angle neutron spectrometer, the main component development and test, beam characterization, and the preliminary experiment for the structure study of polymer have been carried out. Neutron radiography facility, after the precise performance test, has been used for the non-destructive test of industrial component. Addition to the development of main instruments, for the effective utilization of those facilities, the scattering techniques relating to quantitative phase analysis, magnetic structure analysis, texture measurement, residual stress measurement, polymer study, etc, were developed. For the neutron radiography, photographing and printing technique on direct and indirect method was stabilized and the development for the real time image processing technique by neutron TV was carried out. The sample environment facilities for low and high temperature, magnetic field were also developed

  14. Neutrons for materials science

    International Nuclear Information System (INIS)

    The discussion will be limited to applied materials research performed on a customer/contractor basis. The information obtained using neutrons must therefore compete both scientifically and financially with information obtained using other techniques, particularly electron microscopy, X-ray, NMR, infra-red and Raman spectroscopy. It will be argued that the unique nature of the information gained from neutrons often outweighs the undoubted difficulties of access to neutron beams. Examples are given. Small angle scattering has emerged as the neutron technique of widest application in applied materials research. The penetration of neutron beams through containment vessels, as well as through the sample, allows the measurement of 'in situ' time dependent experiments within a furnace, cryostat, pressure vessel or chemical reactor vessel. High resolution powder diffraction is another technique with wide applications. Structural studies are possible on increasing complex phases. The structure and volume fraction of minority phases can be measured at levels appreciably below that possible by X-ray diffraction. A rapidly growing field at present is the measurement of internal strains through the small shifts in lattice spacing. Inelastic scattering measurements exploit the unique property of neutrons to measure the orientations of vibrating molecules. (author)

  15. Neutron scattering in Australia

    Energy Technology Data Exchange (ETDEWEB)

    Knott, R.B. [Australian Nuclear Science and Technology Organisation, Menai (Australia)

    1994-12-31

    Neutron scattering techniques have been part of the Australian scientific research community for the past three decades. The High Flux Australian Reactor (HIFAR) is a multi-use facility of modest performance that provides the only neutron source in the country suitable for neutron scattering. The limitations of HIFAR have been recognized and recently a Government initiated inquiry sought to evaluate the future needs of a neutron source. In essence, the inquiry suggested that a delay of several years would enable a number of key issues to be resolved, and therefore a more appropriate decision made. In the meantime, use of the present source is being optimized, and where necessary research is being undertaken at major overseas neutron facilities either on a formal or informal basis. Australia has, at present, a formal agreement with the Rutherford Appleton Laboratory (UK) for access to the spallation source ISIS. Various aspects of neutron scattering have been implemented on HIFAR, including investigations of the structure of biological relevant molecules. One aspect of these investigations will be presented. Preliminary results from a study of the interaction of the immunosuppressant drug, cyclosporin-A, with reconstituted membranes suggest that the hydrophobic drug interdigitated with lipid chains.

  16. Neutron Nucleic Acid Crystallography.

    Science.gov (United States)

    Chatake, Toshiyuki

    2016-01-01

    The hydration shells surrounding nucleic acids and hydrogen-bonding networks involving water molecules and nucleic acids are essential interactions for the structural stability and function of nucleic acids. Water molecules in the hydration shells influence various conformations of DNA and RNA by specific hydrogen-bonding networks, which often contribute to the chemical reactivity and molecular recognition of nucleic acids. However, X-ray crystallography could not provide a complete description of structural information with respect to hydrogen bonds. Indeed, X-ray crystallography is a powerful tool for determining the locations of water molecules, i.e., the location of the oxygen atom of H2O; however, it is very difficult to determine the orientation of the water molecules, i.e., the orientation of the two hydrogen atoms of H2O, because X-ray scattering from the hydrogen atom is very small.Neutron crystallography is a specialized tool for determining the positions of hydrogen atoms. Neutrons are not diffracted by electrons, but are diffracted by atomic nuclei; accordingly, neutron scattering lengths of hydrogen and its isotopes are comparable to those of non-hydrogen atoms. Therefore, neutron crystallography can determine both of the locations and orientations of water molecules. This chapter describes the current status of neutron nucleic acid crystallographic research as well as the basic principles of neutron diffraction experiments performed on nucleic acid crystals: materials, crystallization, diffraction experiments, and structure determination. PMID:26227050

  17. High quality neutron radiography

    International Nuclear Information System (INIS)

    By the neutron radiography which is reported in this paper, the radiographs which cannot be obtained by X-ray radiography such as the distribution of water flow in a metal vessel or high radioactive substances can be obtained. As the imaging methods of neutron radiography, there are TV method, film method, track etching method and so on. As for these devices, the dynamic range is small, and there is the limit in quantitative evaluation. Consequently, the semiconductor light-receiving element made by Hamamatsu Photonics K.K. developed for measuring weak light was used as a new device. It is called PCD linear image sensor as a plasma coupled device (PCD) is used as the shift register. The basic research on imaging neutron flux distribution by using a cooled type PCD linear image sensor and a honeycomb collimator and analyzing it quantitatively was carried out. The principle of neutron radiography, the PCD linear image sensor system and its cooling unit, the principle and the method of quantitative neutron radiography, the experiment on neutron radiography and its results, and the example of the application to CT are reported. (K.I.)

  18. Coded source neutron imaging

    Energy Technology Data Exchange (ETDEWEB)

    Bingham, Philip R [ORNL; Santos-Villalobos, Hector J [ORNL

    2011-01-01

    Coded aperture techniques have been applied to neutron radiography to address limitations in neutron flux and resolution of neutron detectors in a system labeled coded source imaging (CSI). By coding the neutron source, a magnified imaging system is designed with small spot size aperture holes (10 and 100 m) for improved resolution beyond the detector limits and with many holes in the aperture (50% open) to account for flux losses due to the small pinhole size. An introduction to neutron radiography and coded aperture imaging is presented. A system design is developed for a CSI system with a development of equations for limitations on the system based on the coded image requirements and the neutron source characteristics of size and divergence. Simulation has been applied to the design using McStas to provide qualitative measures of performance with simulations of pinhole array objects followed by a quantitative measure through simulation of a tilted edge and calculation of the modulation transfer function (MTF) from the line spread function. MTF results for both 100um and 10um aperture hole diameters show resolutions matching the hole diameters.

  19. Biology with neutron radiation

    International Nuclear Information System (INIS)

    Neutron diffraction, elastic and inelastic neutron scattering experiments provide important information on the structure, interactions and dynamics of biological molecules. This arises from the unique properties of the neutron and of its interaction with matter. Coherent and incoherent neutron scattering amplitudes and cross-sections are very different for H and 2H (deuterium). Deuterium labelling by chemical or biochemical methods and H2O:2H2O exchange is the basis of high resolution crystallography experiments to locate functionally important H-atoms in protein molecules. It is also very important in low resolution crystallography and small angle scattering experiments to solve large complex structures, such as protein-nucleic acid complexes or biological membrane systems, by using contrast variation techniques. The energies of neutrons with a wavelength of the order of 1 - 10 A are similar to thermal energies and inelastic neutron scattering experiments have been done with different energy resolutions (≥∼ 1 μeV) to characterise the functional dynamics of proteins in solution and in membranes. (author)

  20. Passive neutron dosemeter design

    International Nuclear Information System (INIS)

    A passive neutron dosemeter was designed to be used in mixed radiation fields. The design was carried out using Monte Carlo method. The dosemeter model was a 25.4 cm-diameter polyethylene sphere with a thermoluminescent dosemeter, TLD600, located at the sphere center. This model was irradiated with 50 monoenergetic neutron sources with energies from 10-8 to 20 MeV. A 506.71 cm2-area disk was used to model the source term whose center was located at 100 cm from polyethylene sphere's center. The dosemeter response was compared with the responses of SNOOPY, Harwell 95/0075 and PNR-4. With these responses it was calculated the dosemeter responses for 252Cf, 252Cf/D2O and 239PuBe neutron sources. The passive dosemeter relative response has the same shape of SNOOPY, Harwell 95/0075 and PNR-4 dosemeters. Due to the type of thermal neutron detector used in the passive dosemeter the absolute response per unit fluence, is lower than the absolute response of SNOOPY, Harwell 95/0075 and PNR-4 dosemeters. However the passive dosemeter response in function of the average neutron energy of the 252Cf, 252Cf/D2O and 239PuBe neutron energy was more linear

  1. Determination of Neutron Flux at the HANARO Cold Neutron Guides

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Min Young; Sun, Gwang Min; Lee, Yuna; Yoo, Sang Ho; Lee, Chang Hee; Park, Byung Gun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    A Cold neutron source (CNS) has been installed at the HANARO research reactor. After the completion of the CNS, it was most important to characterize the neutron beam from the CNS and along the neutron guides. Time-of-Flight (TOF) and gold activation methods were utilized to measure the neutron speed distribution and neutron flux, respectively. In this study, we described the neutron flux monitoring at several positions such as a primary shutter, secondary shutters, and sample or monochromator of the experimental instruments and so on

  2. Neutron Star Structure and the Neutron Radius of 208Pb

    CERN Document Server

    Horowitz, C J

    2001-01-01

    We study relationships between the neutron-rich skin of a heavy nucleus and the properties of neutron-star crusts. Relativistic effective field theories with a thicker neutron skin in $^{208}$Pb have a larger electron fraction and a lower liquid-to-solid transition density for neutron-rich matter. These properties are determined by the density dependence of the symmetry energy which we vary by adding nonlinear couplings between isoscalar and isovector mesons. An accurate measurement of the neutron radius in $^{208}$Pb---via parity violating electron scattering---may have important implications for the structure of neutron stars.

  3. Neutron scattering on neutron irradiated steel

    International Nuclear Information System (INIS)

    Three pressure vessel steel systems (two base material and one weld material) with a 50% irradiation induced hardness enhancement were investigated by small angle neutron scattering. All three steel systems were irradiated in the light water moderated research reactor FRJ-1 at a temperature of 1500C. The strongest scattering effect was found for steel A; a pressure vessel containment steel ASTM a 533 B. This system was irradiated with a fluence of 7 1019 n/cm2 (E > 1 MeV). The annealing behaviour was then investigated after isochronal anneals of 300, 350, 400 and 4500C. Viker's hardness measurements were made parallel to the neutron scattering experiments. The hardness enhancement of 50% decreased after the first anneal to 30% and after the second to 18%. The neutron scattering patterns show a decrease in the number of very small voids having a Guinier radius less than 5 A. These voids have annealed, or coagulated into larger voids (Rg = 20-25 A) with a density of n = 1015 cm-3. After the third anneal at 4000C, the scattering patterns became, within statistical errors, identical to the scattering pattern of the unirradiated specimen; but a hardness enhancement of 13% was measured. (orig./WBU)

  4. Fundamental neutron physics at LANSCE

    Energy Technology Data Exchange (ETDEWEB)

    Greene, G.

    1995-10-01

    Modern neutron sources and science share a common origin in mid-20th-century scientific investigations concerned with the study of the fundamental interactions between elementary particles. Since the time of that common origin, neutron science and the study of elementary particles have evolved into quite disparate disciplines. The neutron became recognized as a powerful tool for studying condensed matter with modern neutron sources being primarily used (and justified) as tools for neutron scattering and materials science research. The study of elementary particles has, of course, led to the development of rather different tools and is now dominated by activities performed at extremely high energies. Notwithstanding this trend, the study of fundamental interactions using neutrons has continued and remains a vigorous activity at many contemporary neutron sources. This research, like neutron scattering research, has benefited enormously by the development of modern high-flux neutron facilities. Future sources, particularly high-power spallation sources, offer exciting possibilities for continuing this research.

  5. Radiography with polarised neutrons

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, Michael L.

    2010-08-20

    In this thesis I present a new technique for the spatially resolved investigation of the magnetic properties of bulk samples. Standard one dimensional neutron depolarisation analysis is combined with neutron radiography to a method we call Neutron Depolarisation Imaging (NDI). The experimental setup which was installed at the neutron radiography beam line ANTARES at FRM II consists of a double crystal monochromator, neutron polariser, spin flipper, polarisation analyser and a position sensitive CCD detector. A comprehensive discussion of the requirements for these components is given and the limitations of the method are shown. The maximum spatial resolution which can be achieved with a neutron radiography setup is determined by the collimation of the neutron beam and the distance between sample and detector. Different types of polarisers have been tested and their advantages and disadvantages are discussed. A double crystal monochromator and a new type of polariser employing polarising neutron supermirrors based on the principle of an optical periscope were developed and tested during this work. Furthermore, NDI measurements on various samples of the weakly ferromagnetic materials Pd{sub 1-x}Ni{sub x} and Ni{sub 3}Al are presented. Neutron depolarisation radiography and tomography measurements were conducted with a spatial resolution as high as 0.3 mm on Pd{sub 1-x}Ni{sub x} and Ni{sub 3}Al samples. The feasibility of NDI experiments under hydrostatic pressures up to 10 kbar was shown on a sample of Ni{sub 3}Al using a modified Cu:Be clamp cell. A decrease of the ordering temperature by 2 K under hydrostatic pressure was determined from the NDI measurements and shows the potential of the method for further high pressure experiments. Additionally a method was developed which in principle allows to obtain the intrinsic dependence of the ordering temperature T{sub C} on the ordered moment Ms from NDI measurements on inhomogeneous samples containing regions with

  6. Radiography with polarised neutrons

    International Nuclear Information System (INIS)

    In this thesis I present a new technique for the spatially resolved investigation of the magnetic properties of bulk samples. Standard one dimensional neutron depolarisation analysis is combined with neutron radiography to a method we call Neutron Depolarisation Imaging (NDI). The experimental setup which was installed at the neutron radiography beam line ANTARES at FRM II consists of a double crystal monochromator, neutron polariser, spin flipper, polarisation analyser and a position sensitive CCD detector. A comprehensive discussion of the requirements for these components is given and the limitations of the method are shown. The maximum spatial resolution which can be achieved with a neutron radiography setup is determined by the collimation of the neutron beam and the distance between sample and detector. Different types of polarisers have been tested and their advantages and disadvantages are discussed. A double crystal monochromator and a new type of polariser employing polarising neutron supermirrors based on the principle of an optical periscope were developed and tested during this work. Furthermore, NDI measurements on various samples of the weakly ferromagnetic materials Pd1-xNix and Ni3Al are presented. Neutron depolarisation radiography and tomography measurements were conducted with a spatial resolution as high as 0.3 mm on Pd1-xNix and Ni3Al samples. The feasibility of NDI experiments under hydrostatic pressures up to 10 kbar was shown on a sample of Ni3Al using a modified Cu:Be clamp cell. A decrease of the ordering temperature by 2 K under hydrostatic pressure was determined from the NDI measurements and shows the potential of the method for further high pressure experiments. Additionally a method was developed which in principle allows to obtain the intrinsic dependence of the ordering temperature TC on the ordered moment Ms from NDI measurements on inhomogeneous samples containing regions with different ordering temperatures. This procedure was

  7. Neutrons for materials science

    International Nuclear Information System (INIS)

    The discussion will be limited to applied materials research performed on a customer/contractor basis. The information obtained using neutrons must therefore compete both scientifically and financially with information obtained using other techniques, particular electron microscopy, X-ray, NMR, infra-red and Raman spectroscopy. It will be argued that the unique nature of the information gained from neutrons often outweighs the undoubted difficulties of access to neutron beams. Small-angle scattering has emerged as the neutron technique of widest application in applied materials research. The penetration of neutron beams through containment vessels, as well as through the sample, allows the measurement of in situ time-dependent experiments within a furnace, cryostat, pressure vessel or chemical reactor vessel. Examples will be given of small-angle scattering projects from the nuclear metallurgy, coal, oil, cement, detergent and plastics industries. High-resolution powder diffraction is another technique with wide applications. Structural studies are possible on increasingly complex phases. The structure and volume fraction of minority phase can be measured at levels appreciably below that possible by X-ray diffraction. A rapidly growing field at present is the measurement of internal strains through the small shifts in lattice spacing. Neutron diffraction is unique in being able to measure the full strain tensor from a specified volume within a bulk specimen. Inelastic scattering measurements exploit the unique property of neutrons to measure the orientations of vibrating molecules. Examples will be chosen from the field of catalysis where inelastic spectroscopy has revealed the nature of the bonding of hydrocarbon molecules. (author)

  8. Support for cold neutron utilization

    International Nuclear Information System (INIS)

    - Support for experiments by users of cold neutron scattering instrument - Short-term training of current and potential users of cold neutron scattering instrument for their effective use of the instrument - International collaboration for advanced utilization of cold neutron scattering instruments - Selection and training of qualified instrument scientists for vigorous research endeavors and outstanding achievements in experiments with cold neutron - Research on nano/bio materials using cold neutron scattering instruments - Bulk nano structure measurement using small angle neutron scattering and development of analysis technique

  9. Neutron radiography, techniques and applications

    International Nuclear Information System (INIS)

    After describing the principles of the ''in pool'' and ''dry'' installations, techniques used in neutron radiography are reviewed. Use of converter foils with silver halide films for the direct and transfer methods is described. Advantages of the use of nitrocellulose film for radiographying radioactive objects are discussed. Dynamic imaging is shortly reviewed. Standardization in the field of neutron radiography (ASTM and Euratom Neutron Radiography Working Group) is described. The paper reviews main fields of use of neutron radiography. Possibilities of use of neutron radiography at research reactors in various scientific, industrial and other fields are mentioned. Examples are given of application of neutron radiography in industry and the nuclear field. (author)

  10. Neutron drip transition in accreting and nonaccreting neutron star crusts

    CERN Document Server

    Chamel, N; Zdunik, J L; Haensel, P

    2015-01-01

    The neutron-drip transition in the dense matter constituting the interior of neutron stars generally refers to the appearance of unbound neutrons as the matter density reaches some threshold density $\\rho_\\textrm{drip}$. This transition has been mainly studied under the cold catalyzed matter hypothesis. However, this assumption is unrealistic for accreting neutron stars. After examining the physical processes that are thought to be allowed in both accreting and nonaccreting neutron stars, suitable conditions for the onset of neutron drip are derived and general analytical expressions for the neutron drip density and pressure are obtained. Moreover, we show that the neutron-drip transition occurs at lower density and pressure than those predicted within the mean-nucleus approximation. This transition is studied numerically for various initial composition of the ashes from X-ray bursts and superbursts using microscopic nuclear mass models.

  11. Development of highly effective neutron shields and neutron absorbing materials

    International Nuclear Information System (INIS)

    A wide range of materials, including polymers and hydrogen-occluded alloys that might be usable as the neutron shielding material were examined. And a wide range of materials, including aluminum alloys that might be usable as the neutron-absorbing material were examined. After screening, the candidate material was determined on the basis of evaluation regarding its adaptabilities as a high-performance neutron-shielding and neutron-absorbing material. This candidate material was manufactured for trial, after which material properties tests, neutron-shielding tests and neutron-absorbing tests were carried out on it. The specifications of this material were thus determined. This research has resulted in materials of good performance; a neutron-shielding material based on ethylene propylene rubber and titanium hydride, and a neutron-absorbing material based on aluminum and titanium hydride. (author)

  12. Extracting the neutron-neutron scattering length -- recent developments

    OpenAIRE

    Gardestig, Anders

    2009-01-01

    The experimental and theoretical issues and challenges for extracting the neutron-neutron scattering length are discussed. Particular emphasis is placed on recent results and their impact on the field. Comments are made regarding current experimental and theoretical possibilities.

  13. Neutron imaging system for neutron tomography, radiography, and beam diagnostics

    International Nuclear Information System (INIS)

    A neutron imaging system (NIS) has been recently installed at the University of Texas TRIGA reactor facility. The imaging system establishes new capabilities for beam diagnostics at the Texas Cold Neutron Source (TCNS) for real-time neutron radiography (RTNR) and for neutron computed tomography (NCT) research. The NIS will also be used for other research projects. The system consists of two subsystems as follows: (1) Thomson 9-in. neutron image intensifier (NII) tube sensitive to cold, thermal, and epithermal neutrons, (2) image-processing unit consisting of vidicon camera, two high-resolution monitors, image enhancement and measurement processor, and video printer. The NIS is installed at the cold neutron beam of the TCNS for testing and cold neutron beam diagnostics

  14. Neutron-Induced Failures in Semiconductor Devices

    Energy Technology Data Exchange (ETDEWEB)

    Wender, Stephen Arthur [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-04-06

    This slide presentation explores single event effect, environmental neutron flux, system response, the Los Alamos Neutron Science Center (LANSCE) neutron testing facility, examples of SEE measurements, and recent interest in thermal neutrons.

  15. Imaging with cold neutrons

    International Nuclear Information System (INIS)

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

  16. Imaging with cold neutrons

    Science.gov (United States)

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

    2011-09-01

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

  17. SAD: Neutronics researches - Russia

    International Nuclear Information System (INIS)

    Planned programme of neutronics researches at the SAD facility Research programme for SAD facility is forming in collaboration between scientific teams and design organizations. Main points of the SAD experimental programme are: – Qualification of subcriticality monitoring, experiments with Pulsed Neutron Generator (PNG), precise on-line monitoring of HII; – Validation of the core power-beam current ratio, precise measurements; – Measurements of the spallation neutrons spectral and angular distributions with actual targets; – Measurements of the high energy neutrons spectral and angular distributions behind thick concrete shielding; – Post-irradiation and on-line spallation products yields investigation; – Measurements of spectral dependencies of neutron flux density and power density in different places of the installation, neutron lifetime and effective fraction of delayed neutrons; – Transmutation reactions rates, integral cross-sections and spectral indices measurements; – Interpretation and validation of experimental data, codes validation, benchmarking. One of the main points of experimental research programme is development of experimental techniques for deep subcriticality measurements and monitoring. This question is vitally important for safety assessment of the subcritical systems of high power driven by external sources. Such investigations were performed at subcritical assemblies of zero power with fast and thermal neutron spectra. At the SAD facility these researches will be continued making important step towards construction of industrial scale ADS, where reactivity trips caused by beam and coolant fluctuations will determine the safety margins. Within SAD research programme it is planned to pay special attention to the experiments on HII measurements and monitoring by inverse multiplication, asymptotic period and other methods. The time structure of the proton beam will give ample opportunities for application the pulsed techniques

  18. Twisting Neutron Waves

    Science.gov (United States)

    Pushin, Dmitry

    Most waves encountered in nature can be given a ``twist'', so that their phase winds around an axis parallel to the direction of wave propagation. Such waves are said to possess orbital angular momentum (OAM). For quantum particles such as photons, atoms, and electrons, this corresponds to the particle wavefunction having angular momentum of Lℏ along its propagation axis. Controlled generation and detection of OAM states of photons began in the 1990s, sparking considerable interest in applications of OAM in light and matter waves. OAM states of photons have found diverse applications such as broadband data multiplexing, massive quantum entanglement, optical trapping, microscopy, quantum state determination and teleportation, and interferometry. OAM states of electron beams have been used to rotate nanoparticles, determine the chirality of crystals and for magnetic microscopy. Here I discuss the first demonstration of OAM control of neutrons. Using neutron interferometry with a spatially incoherent input beam, we show the addition and conservation of quantum angular momenta, entanglement between quantum path and OAM degrees of freedom. Neutron-based quantum information science heretofore limited to spin, path, and energy degrees of freedom, now has access to another quantized variable, and OAM modalities of light, x-ray, and electron beams are extended to a massive, penetrating neutral particle. The methods of neutron phase imprinting demonstrated here expand the toolbox available for development of phase-sensitive techniques of neutron imaging. Financial support provided by the NSERC Create and Discovery programs, CERC and the NIST Quantum Information Program is acknowledged.

  19. Apollo 16 neutron stratigraphy.

    Science.gov (United States)

    Russ, G. P., III

    1973-01-01

    The Apollo 16 soils have the largest low-energy neutron fluences yet observed in lunar samples. Variations in the isotopic ratios Gd-158/Gd-157 and Sm-150/Sm-149 (up to 1.9 and 2.0%, respectively) indicate that the low-energy neutron fluence in the Apollo 16 drill stem increases with depth throughout the section sampled. Such a variation implies that accretion has been the dominant regolith 'gardening' process at this location. The data may be fit by a model of continuous accretion of pre-irradiated material or by models involving as few as two slabs of material in which the first slab could have been deposited as long as 1 b.y. ago. The ratio of the number of neutrons captured per atom by Sm to the number captured per atom by Gd is lower than in previously measured lunar samples, which implies a lower energy neutron spectrum at this site. The variation of this ratio with chemical composition is qualitatively similar to that predicted by Lingenfelter et al. (1972). Variations are observed in the ratio Gd-152/Gd-160 which are fluence-correlated and probably result from neutron capture by Eu-151.

  20. Neutrons and art

    International Nuclear Information System (INIS)

    Following modern trends in art objects connoisseurship, through examination of the structure of art objects supports traditional studies conducted by art historians based on composition, iconographic and stylistic comparisons. It must be emphasized that complete technological examinations are carried out by means of comprehensive physical and chemical studies. Among various methods used for the examination of art objects, methods which apply neutrons such as instrumental neutron activation analysis (INAA), prompt gamma activation analysis (PGAA) and neutron-induced autoradiography are crucial due to their high sensitivity, reproducibility and capability of simultaneous determination of several tens of elements. Systematic studies on art objects using instrumental neutron activation analysis and neutron autoradiography have been carried out in the institute of Nuclear Chemistry and Technology. It was possible to accumulate a number of essential data on the concentration of trace elements particularly in chalk grounds and pigments (such as lead white, lead-tin yellow, smalt), Chinese porcelain, Thai ceramics, silver denarius, jewellery made of copper alloys, as well as in the clay fillings of Egyptian mummies. The above mentioned examination of art objects prior to their conservation helps to determine precisely the materials used in the process of creating art objects, as well as to identify the appropriate place of origin of particular materials. (author)

  1. Neutron source multiplication method

    International Nuclear Information System (INIS)

    Extensive use has been made of neutron source multiplication in thousands of measurements of critical masses and configurations and in subcritical neutron-multiplication measurements in situ that provide data for criticality prevention and control in nuclear materials operations. There is continuing interest in developing reliable methods for monitoring the reactivity, or k/sub eff/, of plant operations, but the required measurements are difficult to carry out and interpret on the far subcritical configurations usually encountered. The relationship between neutron multiplication and reactivity is briefly discussed and data presented to illustrate problems associated with the absolute measurement of neutron multiplication and reactivity in subcritical systems. A number of curves of inverse multiplication have been selected from a variety of experiments showing variations observed in multiplication during the course of critical and subcritical experiments where different methods of reactivity addition were used, with different neutron source detector position locations. Concern is raised regarding the meaning and interpretation of k/sub eff/ as might be measured in a far subcritical system because of the modal effects and spectrum differences that exist between the subcritical and critical systems. Because of this, the calculation of k/sub eff/ identical with unity for the critical assembly, although necessary, may not be sufficient to assure safety margins in calculations pertaining to far subcritical systems. Further study is needed on the interpretation and meaning of k/sub eff/ in the far subcritical system

  2. Fast neutron dosimetry

    International Nuclear Information System (INIS)

    During 1988--1990 the magnetic resonance dosimetry project was completed, as were the 250 MeV proton shielding measurements. The first cellular experiment using human cells in vitro at the 1 GeV electron storage ring was also accomplished. More detail may be found in DOE Report number-sign DOE/EV/60417-002 and the open literature cited in the individual progress subsections. We report Kinetic Energy Released in Matter (KERMA), factor measurements in several elements of critical importance to neutron radiation therapy and radiation protection for space habitation and exploration for neutron energies below 30 MeV. The results of this effort provide the only direct measurements of the oxygen and magnesium kerma factors above 20 MeV neutron energy, and the only measurements of the iron kerma factor above 15 MeV. They provide data of immediate relevance to neutron radiotherapy and impose strict criteria for normalizing and testing nuclear models used to calculate kerma factors at higher neutron energies

  3. Neutron shielding material

    International Nuclear Information System (INIS)

    From among the neutron shielding materials of the 'kobesh' series developed by Kobe Steel, Ltd. for transport and storage packagings, silicon rubber base type material has been tested for several items with a view to practical application and official authorization, and in order to determine its adaptability to actual vessels. Silicon rubber base type 'kobesh SR-T01' is a material in which, from among the silicone rubber based neutron shielding materials, the hydrogen content is highest and the boron content is most optimized. Its neutron shielding capability has been already described in the previous report (Taniuchi, 1986). The following tests were carried out to determine suitability for practical application; 1) Long-term thermal stability test 2) Pouring test on an actual-scale model 3) Fire test The experimental results showed that the silicone rubber based neutron shielding material has good neutron shielding capability and high long-term fire resistance, and that it can be applied to the advanced transport packaging. (author)

  4. Hybrid superconducting neutron detectors

    Energy Technology Data Exchange (ETDEWEB)

    Merlo, V.; Lucci, M.; Ottaviani, I. [Dipartimento di Fisica, Università Tor Vergata, Via della Ricerca Scientifica, I-00133 Roma (Italy); Salvato, M.; Cirillo, M. [Dipartimento di Fisica, Università Tor Vergata, Via della Ricerca Scientifica, I-00133 Roma (Italy); CNR SPIN Salerno, Università di Salerno, Via Giovanni Paolo II, n.132, 84084 Fisciano (Italy); Scherillo, A. [Science and Technology Facility Council, ISIS Facility Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Celentano, G. [ENEA Frascati Research Centre, Via. E. Fermi 45, 00044 Frascati (Italy); Pietropaolo, A., E-mail: antonino.pietropaolo@enea.it [ENEA Frascati Research Centre, Via. E. Fermi 45, 00044 Frascati (Italy); Mediterranean Institute of Fundamental Physics, Via Appia Nuova 31, 00040 Marino, Roma (Italy)

    2015-03-16

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

  5. Hybrid superconducting neutron detectors

    International Nuclear Information System (INIS)

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

  6. SUSANS With Polarized Neutrons

    Science.gov (United States)

    Wagh, Apoorva G.; Rakhecha, Veer Chand; Strobl, Makus; Treimer, Wolfgang

    2005-01-01

    Super Ultra-Small Angle Neutron Scattering (SUSANS) studies over wave vector transfers of 10–4 nm–1 to 10–3 nm–1 afford information on micrometer-size agglomerates in samples. Using a right-angled magnetic air prism, we have achieved a separation of ≈10 arcsec between ≈2 arcsec wide up- and down-spin peaks of 0.54 nm neutrons. The SUSANS instrument has thus been equipped with the polarized neutron option. The samples are placed in a uniform vertical field of 8.8 × 104 A/m (1.1 kOe). Several magnetic alloy ribbon samples broaden the up-spin neutron peak significantly over the ±1.3 × 10–3 nm–1 range, while leaving the down-spin peak essentially unaltered. Fourier transforms of these SUSANS spectra corrected for the instrument resolution, yield micrometer-range pair distribution functions for up- and down-spin neutrons as well as the nuclear and magnetic scattering length density distributions in the samples.

  7. Hybrid superconducting neutron detectors

    Science.gov (United States)

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

    2015-03-01

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

  8. Hybrid Superconducting Neutron Detectors

    CERN Document Server

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

    2014-01-01

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

  9. Neutron nuclear physics under the neutron science project

    Energy Technology Data Exchange (ETDEWEB)

    Chiba, Satoshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-11-01

    The concept of fast neutron physics facility in the Neutron Science Research project is described. This facility makes use of an ultra-short proton pulse (width < 1 ns) for fast neutron time-of-flight works. The current design is based on an assumption of the maximum proton current of 100 {mu}A. Available neutron fluence and energy resolution are explained. Some of the research subjects to be performed at this facility are discussed. (author)

  10. Neutron spectra and dosimetric assessment around a neutron Howitzer container

    OpenAIRE

    Barros, Silvia; Gallego Díaz, Eduardo F.; Lorente Fillol, Alfredo; Gonçalves, Isabel F.; Vaz, Pedro; Vega-Carrillo, Héctor René; Zankl, María

    2014-01-01

    The neutron Howitzer container at the Neutron Measurements Laboratory of the Nuclear Engineering Department of the Polytechnic University of Madrid (UPM), is equipped with a 241Am-Be neutron source of 74 GBq in its center. The container allows the source to be in either the irradiation or the storage position. To measure the neutron fluence rate spectra around the Howitzer container, measurements were performed using a Bonner spheres spectrometer and the spectra were unfolded using the NSDann...

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

    OpenAIRE

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

    2015-01-01

    In non-destructive evaluation with X-rays light elements embedded in dense, heavy (or high-Z) matrices show little contrast and their structural details can hardly be revealed. Neutron radiography, on the other hand, provides a solution for those cases, in particular for hydrogenous materials, owing to the large neutron scattering cross section of hydrogen and uncorrelated dependency of neutron cross section on the atomic number. The majority of neutron imaging experiments at the present time...

  12. Inelastic neutron scattering studies on the 3d-4f heterometallic single-molecule magnet Mn2Nd2

    International Nuclear Information System (INIS)

    The discovery of slow relaxation and quantum tunneling of the magnetization in Mn12ac more than 15 years ago has inspired both physicists and chemists alike. This class of molecules, now called single-molecule magnets (SMMs), has very recently been expanded to heterometallic clusters incorporating transition metal and rare earth ions. The 4f ions were chosen because of their large angular momentum and magnetic anisotropy. Inelastic neutron scattering experiments were performed on the time-of-flight disk-chopper spectrometer IN5 at ILL on the SMM Mn2Nd2. A magnetic model was developed which perfectly describes all data, including the magnetic data. It was found that neither the large anisotropy nor the large angular momentum of the NdIII ions is the main reason for the SMM behavior in this molecule. Our analysis of the data indicates that it is the weak coupling of the NdIII ions to the MnIII ions, usually considered as a drawback of rare earth ions, which enhances the relaxation time and therefore leads to SMM behavior.

  13. Cooling of Neutron Stars and 3P_2 neutron gap

    OpenAIRE

    Grigorian, H.; Voskresensky, D.N.(National Research Nuclear University (MEPhI), Moscow, 115409, Russia)

    2005-01-01

    We study the dependence of the cooling of isolated neutron stars on the magnitude of the $3P_2$ neutron gap. It is demonstrated that our ``Nuclear medium cooling scenario'' is in favor of a suppressed value of the $3P_2$ neutron gap.

  14. Neutron imaging and small angle neutron scattering instruments at KUR

    International Nuclear Information System (INIS)

    We review the neutron imaging (NI) and small-angle neutron scattering (SANS) instruments at KUR, Kumatori, Osaka, Japan. There are two NI and one SANS instruments. The both instruments are compact and used flexibly. Some challenging experiments taking advantage of low neutron fluence are described. The feature of KUR is also described briefly. (author)

  15. Uniformly rotating neutron stars

    CERN Document Server

    Boshkayev, Kuantay

    2016-01-01

    In this chapter we review the recent results on the equilibrium configurations of static and uniformly rotating neutron stars within the Hartle formalism. We start from the Einstein-Maxwell-Thomas-Fermi equations formulated and extended by Belvedere et al. (2012, 2014). We demonstrate how to conduct numerical integration of these equations for different central densities ${\\it \\rho}_c$ and angular velocities $\\Omega$ and compute the static $M^{stat}$ and rotating $M^{rot}$ masses, polar $R_p$ and equatorial $R_{\\rm eq}$ radii, eccentricity $\\epsilon$, moment of inertia $I$, angular momentum $J$, as well as the quadrupole moment $Q$ of the rotating configurations. In order to fulfill the stability criteria of rotating neutron stars we take into considerations the Keplerian mass-shedding limit and the axisymmetric secular instability. Furthermore, we construct the novel mass-radius relations, calculate the maximum mass and minimum rotation periods (maximum frequencies) of neutron stars. Eventually, we compare a...

  16. Neutron beam characterization

    International Nuclear Information System (INIS)

    At the first Research Coordination Meeting in November 1999 it was agreed that each experimental participant would characterize his own neutron beam and detector system, and then use it to analyze an unknown sample. A set of five materials was prepared and distributed to aid this effort: titanium foil, gold foil, borophosphosilicate glass on silicon, boron 10-aluminum alloy sheet, and a mixture of a complex aluminosilicate and graphite. Neutron flux can be measured by the conventional foil activation method using the gold foil. The titanium foil is to be used to measure the sensitivity of the system, the product of the neutron flux and the detector efficiency. The effective velocity or wavelength of the beam can be measured with the boron samples using a prescribed procedure. Excel spreadsheets for the flux and velocity calculations were placed on the IAEA server ndsalpha.iaea.org

  17. Hyperons and neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Vidaña, Isaac [Centro de Física Computacional, Department of Physics, University of Coimbra, PT-3004-516 Coimbra (Portugal)

    2015-02-24

    In this lecture I will briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I will revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667±0.021M{sub ⊙}), PSR J1614–2230 (1.97±0.04M{sub ⊙}), and PSR J0348+0432 (2.01±0.04M{sub ⊙}). Finally, I will also examine the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  18. Hyperons and neutron stars

    International Nuclear Information System (INIS)

    In this work we briefly review some of the effects of hyperons on neutron and proto-neutron star properties. We revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, due to the presence of hyperons, a puzzle which has become more intriguing due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1614-2230 (1.97±0.04M⊙) and PSR J1903+0327 (1.667±0.021M⊙). We examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability

  19. Hyperons and neutron stars

    International Nuclear Information System (INIS)

    In this lecture I will briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I will revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667±0.021M⊙), PSR J1614–2230 (1.97±0.04M⊙), and PSR J0348+0432 (2.01±0.04M⊙). Finally, I will also examine the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability

  20. Hyperons in Neutron Stars

    Science.gov (United States)

    Vidaña, Isaac

    2016-01-01

    In this work I briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve because of the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667 ± 0.021M⊙), PSR J1614-2230 (1.97 ± 0.04M⊙), and PSR J0348+0432 (2.01 ± 0.04M⊙). Some of the solutions proposed to tackle this problem are discussed. Finally, I re-examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  1. Hyperons in Neutron Stars

    CERN Document Server

    Vidana, Isaac

    2015-01-01

    In this work I briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 ($1.667\\pm 0.021 M_\\odot$), PSR J1614-2230 ($1.97 \\pm 0.04 M_\\odot$), and PSR J0348+0432 ($2.01 \\pm 0.04 M_\\odot$). Some of the solutions proposed to tackle this problem are discussed. Finally, I re-examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  2. Ultrafast neutron detector

    Science.gov (United States)

    Wang, Ching L.

    1987-01-01

    The invention comprises a neutron detector (50) of very high temporal resolution that is particularly well suited for measuring the fusion reaction neutrons produced by laser-driven inertial confinement fusion targets. The detector comprises a biased two-conductor traveling-wave transmission line (54, 56, 58, 68) having a uranium cathode (60) and a phosphor anode (62) as respective parts of the two conductors. A charge line and Auston switch assembly (70, 72, 74) launch an electric field pulse along the transmission line. Neutrons striking the uranium cathode at a location where the field pulse is passing, are enabled to strike the phosphor anode and produce light that is recorded on photographic film (64). The transmission line may be variously configured to achieve specific experimental goals.

  3. Carbon neutron star atmospheres

    CERN Document Server

    Suleimanov, V F; Pavlov, G G; Werner, K

    2013-01-01

    The accuracy of measuring the basic parameters of neutron stars is limited in particular by uncertainties in chemical composition of their atmospheres. For example, atmospheres of thermally - emitting neutron stars in supernova remnants might have exotic chemical compositions, and for one of them, the neutron star in CasA, a pure carbon atmosphere has recently been suggested by Ho & Heinke (2009). To test such a composition for other similar sources, a publicly available detailed grid of carbon model atmosphere spectra is needed. We have computed such a grid using the standard LTE approximation and assuming that the magnetic field does not exceed 10^8 G. The opacities and pressure ionization effects are calculated using the Opacity Project approach. We describe the properties of our models and investigate the impact of the adopted assumptions and approximations on the emergent spectra.

  4. Multidisk neutron velocity selectors

    International Nuclear Information System (INIS)

    Helical multidisk velocity selectors used for neutron scattering applications have been analyzed and tested experimentally. Design and performance considerations are discussed along with simple explanation of the basic concept. A simple progression is used for the inter-disk spacing in the 'Rosta' design. Ray tracing computer investigations are presented in order to assess the 'coverage' (how many absorbing layers are stacked along the path of 'wrong' wavelength neutrons) and the relative number of neutrons absorbed in each disk (and therefore the relative amount of gamma radiation emitted from each disk). We discuss whether a multidisk velocity selector can be operated in the 'reverse' configuration (i.e. the selector is turned by 1800 around a vertical axis with the rotor spun in the reverse direction). Experimental tests and calibration of a multidisk selector are reported together with evidence that a multidisk selector can be operated in the 'reverse' configuration. (orig.)

  5. Gadolinium neutron capture therapy

    International Nuclear Information System (INIS)

    Gadolinium neutron capture therapy makes use of photons and electrons produced by nuclear reactions between gadolinium and lower-energy neutrons which occur within the tumor. The results of our studies have shown that its radiation effect is mostly of low LET and that the electrons are the significant component in the over-all dose. The dose from gadolinium neutron capture reactions does not seem to increase in proportion to the gadolinium concentration, and the Gd-157 concentration of about 100 μg/ml appears most optimal for therapy. Close contact between gadolinium and the cell is not necessarily required for cell inactivation, however, the effect of electrons released from intracellular gadolinium may be significant. Experimental studies on tumor-bearing mice and rabbits have shown that this is a very promising modality though further improvements in gadolinium delivery to tumors are needed. (author)

  6. Personal neutron dosimeter

    International Nuclear Information System (INIS)

    Objective: To introduce the principle, structure and character of a new personal neutron dosimeter. Methods: In combination with relative documents, the dosimeter datum measured on neutron and γ rays emitted by 241Am-Be source, when 6LiF (Mg, Cu, P) and 7LiF(Mg, Cu, P) are disposed, are evaluated. Results: Its measurement results showed good linear relationship and can be repeated. The sensitivity of neutron detection is 0.72 times of 60Co γ rays and this result is similar to that to be reported previously. Conclusion: The measurement results of this dosimeter has been satisfied with the requirement of personal dose measurement in n or n-γ radiation field under 4.4 MeV energy

  7. Plasma focus neutron source

    International Nuclear Information System (INIS)

    A neutron source not permanently active is obtained from an electric discharge plasma focus (PF) device. A small PF device, a Mather model device, works in the limit of low energy, 100 to 200 J at charging voltage of 20 to 30 kV with a capacitor bank of 160 nF, and a characteristic inductance of 25 to 50 nH. A theoretical model leads us to estimate the optimum values of capacitance, inductance, initial charging voltage and electrode geometry. In this work is presented the design evolution and construction of a first PF neutron source prototype, preliminary measures of current, voltage and temporal evolution of the current with the end of have an electric characterization. This parameters must be optimized with the objective of geeting an emission of 104 to 105 neutrons per pulse when Deuterium is used like filled gas (C.W)

  8. Quaking Neutron Stars

    CERN Document Server

    Franco, L M; Epstein, R I; Franco, Lucia M.; Link, Bennett; Epstein, Richard I.

    1999-01-01

    Gravitational, magnetic and superfluid forces can stress the crust of an evolving neutron star. Fracture of the crust under these stresses could affect the star's spin evolution and generate high-energy emission. We study the growth of strain in the crust of a spinning down, magnetized neutron star and examine the initiation of crust cracking (a {\\em starquake}). In preliminary work (Link, Franco & Epstein 1998), we studied a homogeneous model of a neutron star. Here we extend this work by considering a more realistic model of a solid, homogeneous crust afloat on a liquid core. In the limits of astrophysical interest, our new results qualitatively agree with those from the simpler model: the stellar crust fractures under shear stress at the rotational equator, matter moves to higher latitudes and the star's oblateness is reduced. Magnetic stresses favor faults directed toward the magnetic poles. Thus our previous conclusions concerning the star's spin response still hold; namely, asymmetric redistribution...

  9. Neutron star at finite temperature

    International Nuclear Information System (INIS)

    It is well known that neutron star is remanent of supernova explosion. At the time of birth, hot neutron stars are composed of supernova matter and it is at temperature about 20 MeV. Afterwards this new born neutron star is cooled down by neutron diffusion process and within a time scale also of 10-20 seconds, it almost evolves into a usual cold neutron star where the temperature is about 0.01 MeV, which contains neutron star matter. Since the finite temperature neutron star calculation is very rare much interest is taken for the calculation at finite temperature. In this abstracts some of the static and rotational properties of hot neutron star at temperature T= 5 MeV, 10 MeV and 15 MeV are given

  10. Nuclear fusion and neutron processes

    International Nuclear Information System (INIS)

    Problems of providing development of the design of an experimental fusion reactor with necessary neutron-physical data are discussed. Isotope composition of spent fuel in the blanket of a hybride fusion reactor (HFR) is given. Neutron balance of the reactor with Li-blanket and neutron balance of the reactor with Pb-multiplier are disclosed. A simplified scheme of neutron and energy balance in the HFR blanket is given. Development and construction of the experimental power reactor is shown to become the nearest problem of the UTS program. Alongside with other complex physical and technical problems solution of this problem requires realization of a wide program of neutron-physical investigations including measurements with required accuracy of neutron cross sections, development of methodical, program and constant basis of neutron calculations and macroscopic experiments on neutron sources

  11. Recent advances in neutron tomography

    International Nuclear Information System (INIS)

    Neutron imaging has been shown to be an excellent imaging tool for many nondestructive evaluation applications. Significantly improved contrast over X-ray images is possible for materials commonly found in engineering assemblies. The major limitations have been the neutron source and detection. A low cost, position sensitive neutron tomography detector system has been designed and built based on an electro-optical detector system using a LiF-ZnS scintillator screen and a cooled charge coupled device. This detector system can be used for neutron radiography as well as two and three-dimensional neutron tomography. Calculated performance of the system predicted near-quantum efficiency for position sensitive neutron detection. Experimental data was recently taken using this system at McClellan Air Force Base, Air Logistics Center, Sacramento, CA. With increased availability of low cost neutron sources and advanced image processing, neutron tomography will become an increasingly important nondestructive imaging method

  12. Neutron star crusts

    International Nuclear Information System (INIS)

    The formation, structure, composition, and the equation of state of neutron star crusts are described. A scenario of formation of the crust in a newly born neutron star is considered and a model of evolution of the crust composition during the early neutron star cooling is presented. Structure of the ground state of the crust is studied. In the case of the outer crust, recent nuclear data on masses of neutron rich nuclei are used. For the inner crust, results of different many-body calculations are presented, and dependence on the assumed effective nucleon-nucleon interaction is discussed. Uncertainties concerning the bottom layers of the crust and crust-liquid interface are illustrated using results of various many-body calculations based on different effective nucleon-nucleon interactions. A scenario of formation of a crust of matter-accreting neutron star is presented, and evolution of the crust-matter element under the increasing pressure of accreted layer is studied. Within a specific dense matter model, composition of accreted crust is calculated, and is shown to be vastly different from the ground-state one. Non-equilibrium processes in the crust of mass-accreting neutron star are studied, heat release due to them is estimated, and their relevance to the properties of X-ray sources is briefly discussed. Equation of state of the ground-state crust is presented, and compared with that for accreted crust. Elastic properties of the crust are reviewed. Possible deviations from idealized models of one-component plasmas are briefly discussed. (orig.)

  13. Neutron skin in Osmium isotopes

    International Nuclear Information System (INIS)

    Here we have made an attempt to calculate neutron skin thickness in rare earth even-even osmium isotopes. The selected isotopes ranges from 2-p to 2-n drip line. Neutron skin is an important feature of neutron rich nuclei. The ground state proton and neutron rms radii have been calculated using HFB approximation. A comparison of calculated radii have been done by using two different Skyrme parameterizations and two different basis

  14. Corrosion resistant neutron absorbing coatings

    Science.gov (United States)

    Choi, Jor-Shan; Farmer, Joseph C.; Lee, Chuck K.; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2012-05-29

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  15. Corrosion resistant neutron absorbing coatings

    Science.gov (United States)

    Choi, Jor-Shan; Farmer, Joseph C; Lee, Chuck K; Walker, Jeffrey; Russell, Paige; Kirkwood, Jon; Yang, Nancy; Champagne, Victor

    2013-11-12

    A method of forming a corrosion resistant neutron absorbing coating comprising the steps of spray or deposition or sputtering or welding processing to form a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material. Also a corrosion resistant neutron absorbing coating comprising a composite material made of a spray or deposition or sputtering or welding material, and a neutron absorbing material.

  16. Neutron imaging in materials science

    OpenAIRE

    Nikolay Kardjilov; Ingo Manke; André Hilger; Markus Strobl; John Banhart

    2011-01-01

    Neutron imaging is a non-destructive technique that can reveal the interior of many materials and engineering components and also probe magnetic fields. Within the past few years, several new imaging modes have been introduced that extend the scope of neutron imaging beyond conventional neutron attenuation imaging, yielding both 2- and 3D information about properties and phenomena inaccessible until now. We present an overview of the most important advances in the application of neutron imagi...

  17. Simplified fast neutron dosimeter

    Science.gov (United States)

    Sohrabi, Mehdi

    1979-01-01

    Direct fast-neutron-induced recoil and alpha particle tracks in polycarbonate films may be enlarged for direct visual observation and automated counting procedures employing electrochemical etching techniques. Electrochemical etching is, for example, carried out in a 28% KOH solution at room temperature by applying a 2000 V peak-to-peak voltage at 1 kHz frequency. Such recoil particle amplification can be used for the detection of wide neutron dose ranges from 1 mrad. to 1000 rads. or higher, if desired.

  18. GUIDE FOR POLARIZED NEUTRONS

    Science.gov (United States)

    Sailor, V.L.; Aichroth, R.W.

    1962-12-01

    The plane of polarization of a beam of polarized neutrons is changed by this invention, and the plane can be flipped back and forth quicitly in two directions in a trouble-free manner. The invention comprises a guide having a plurality of oppositely directed magnets forming a gap for the neutron beam and the gaps are spaced longitudinally in a spiral along the beam at small stepped angles. When it is desired to flip the plane of polarization the magnets are suitably rotated to change the direction of the spiral of the gaps. (AEC)

  19. Hybrid Superconducting Neutron Detectors

    OpenAIRE

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

    2014-01-01

    A new neutron detection concept is presented that is based on superconductive niobium (Nb) strips coated by a boron (B) layer. The working principle of the detector relies on the nuclear reaction 10B+n $\\rightarrow$ $\\alpha$+ 7Li , with $\\alpha$ and Li ions generating a hot spot on the current-biased Nb strip which in turn induces a superconducting-normal state transition. The latter is recognized as a voltage signal which is the evidence of the incident neutron. The above described detection...

  20. Fast neutron dosimetry

    International Nuclear Information System (INIS)

    Research concentrated on three major areas during the last twelve months: (1) investigations of energy fluence and absorbed dose measurements using crystalline and hot pressed TLD materials exposes to ultrasoft beams of photons, (2) fast neutron kerma factor measurements for several important elements as well as NE-213 scintillation material response function determinations at the intense ''white'' source available at the WNR facility at LAMPF, and (3) kerma factor ratio determinations for carbon and oxygen to A-150 tissue equivalent plastic at the clinical fast neutron radiation facility at Harper Hospital, Detroit, MI. Progress summary reports of these efforts are given in this report

  1. The neutron star zoo

    Science.gov (United States)

    Harding, Alice K.

    2013-12-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission.

  2. The Neutron Star Zoo

    CERN Document Server

    Harding, Alice K

    2013-01-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission.

  3. Neutron-antineutron oscillations

    International Nuclear Information System (INIS)

    The n anti n-oscillations in various media and systems were considered fenomenologically. The low limit of oscillation period was estimated. The requirements to experiment conditions for discovering the (n reversible anti n)-transition in free state were determined. The ways o+ search of transition of free neutron into antineutron are discussed. An experiment using a neutron source of the meson factory of the AN USSR IJI is proposed. It is shown that the realization of this proposal will allow to advance the n anti n-oscillation period measurement up to the value (0.5-1)x1010 s

  4. The neutron bomb

    International Nuclear Information System (INIS)

    The 'weapon with increased radiation', as the neutron bomb is officially called, has become the subject of fervent discussions. As a substitute for nuclear bombs it is said to reduce the damage to the non-combatant population when tactically deployed, having a greatly reduced radius of action - that at least is what the military say, who are in favour of it. The article describes the radiation effect of the atomic bomb from the examples of Hiroshima and Nagasaki. The report on the military concept and development of the neutron bomb is followed by a description of how might be constructed. (orig.)

  5. Fast neutron dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    DeLuca, P.M. Jr.; Pearson, D.W.

    1992-01-01

    This progress report concentrates on two major areas of dosimetry research: measurement of fast neutron kerma factors for several elements for monochromatic and white spectrum neutron fields and determination of the response of thermoluminescent phosphors to various ultra-soft X-ray energies and beta-rays. Dr. Zhixin Zhou from the Shanghai Institute of Radiation Medicine, People's Republic of China brought with him special expertise in the fabrication and use of ultra-thin TLD materials. Such materials are not available in the USA. The rather unique properties of these materials were investigated during this grant period.

  6. Spallation neutron production measurements

    International Nuclear Information System (INIS)

    Measurements of neutron production by the proton bombardment of range-thick targets of lead (Pb) and of tungsten (W) at energies of 0.8, 1.0, 1.2, and 1.4 GeV were made for comparison with calculations based on the computer codes LAHET for neutrons with Eη > 20 MeV and MCNP for Eη ≤ 20 MeV and also to compare with each of two prior experiments dating from about 1965. 2 refs., 7 figs., 4 tabs

  7. MCNP neutron benchmarks

    International Nuclear Information System (INIS)

    Over 50 neutron benchmark calculations have recently been completed as part of an ongoing program to validate the MCNP Monte Carlo radiation transport code. The new and significant aspects of this work are as follows: These calculations are the first attempt at a validation program for MCNP and the first official benchmarking of version 4 of the code. We believe the chosen set of benchmarks is a comprehensive set that may be useful for benchmarking other radiation transport codes and data libraries. These calculations provide insight into how well neutron transport calculations can be expected to model a wide variety of problems

  8. Neutron irradiation effect of silicon

    International Nuclear Information System (INIS)

    Several kinds of silicon wafers were irradiated at four neutron fields with different energy spectra. Electrical resistivity and deep level defect concentrations after the neutron irradiation, and their changes against number of displacement atoms (DPA's) for different neutron fields were compared. The number of DPA's was calculated by N. Yamano's data. (author)

  9. Neutronic measurements of radioactive waste

    International Nuclear Information System (INIS)

    This document presents the general matters involved in the radioactive waste management and the different non destructive assays of radioactivity. The neutronic measurements used in the characterization of waste drums containing emitters are described with more details, especially the active neutronic interrogation assays with prompt or delayed neutron detection: physical principle, signal processing and evaluation of the detection limit. (author)

  10. Capture-gated neutron spectrometry

    CERN Document Server

    Czirr, J B; Buehler, D; McKnight, T K; Carroll, J L; Abbott, T; Wilcox, E

    2002-01-01

    The applications of a new inorganic scintillator, lithium gadolinium borate, to neutron dosimetry and spectroscopy, are described. A dosimeter using this material registers, in separate energy bins, thermal, epithermal and MeV neutrons. A spectrometer for MeV neutrons has a calculated energy resolution of 10% FWHM.

  11. Rotational Deformation of Neutron Stars

    Institute of Scientific and Technical Information of China (English)

    WEN De-Hua; CHEN Wei; LIU Liang-Gang

    2005-01-01

    @@ The rotational deformations of two kinds of neutron stars are calculated by using Hartle's slow-rotation formulism.The results show that only the faster rotating neutron star gives an obvious deformation. For the slow rotating neutron star with a period larger than hundreds of millisecond, the rotating deformation is very weak.

  12. Educational activities for neutron sciences

    International Nuclear Information System (INIS)

    Since now we have several world-leading neutron science facilities in Japan, enlightenment activities for introducing neutron sciences, for example, to young people is an indispensable issue. Hereafter, we will report present status of the activities based on collaborations between universities and neutron facilities. A few suggestions for future educational activity of JSNS are also shown. (author)

  13. Introductory theory of neutron scattering

    International Nuclear Information System (INIS)

    The paper comprises a set of six lecture notes which were delivered to the summer school on 'Neutron Scattering at a pulsed source', Rutherford Laboratory, United Kingdom, 1986. The lectures concern the physical principles of neutron scattering. The topics of the lectures include: diffraction, incoherent inelastic scattering, connection with the Schroedinger equation, magnetic scattering, coherent inelastic scattering, and surfaces and neutron optics. (UK)

  14. New electronically black neutron detectors

    International Nuclear Information System (INIS)

    Two neutron detectors are described that can function in a continuous radiation background. Both detectors identify neutrons by recording a proton recoil pulse followed by a characteristic capture pulse. This peculiar signature indicates that the neutron has lost all its energy in the scintillator. Resolutions and efficiencies have been measured for both detectors

  15. Neutron recognition in LAND detector for large neutron multiplicity

    CERN Document Server

    Pawłowski, P; Leifels, Y; Trautmann, W; Adrich, P; Aumann, T; Bacri, C O; Barczyk, T; Bassini, R; Bianchin, S; Boiano, C; Boretzky, K; Boudard, A; Chbihi, A; Cibor, J; Czech, B; De Napoli, M; Ducret, J -E; Emling, H; Frankland, J D; Gorbinet, T; Hellström, M; Henzlova, D; Hlavac, S; Immè, J; Iori, I; Johansson, H; Kezzar, K; Kupny, S; Lafriakh, A; Fèvre, A Le; Gentil, E Le; Leray, S; Łukasik, J; Lühning, J; Lynch, W G; Lynen, U; Majka, Z; Mocko, M; Müller, W F J; Mykulyak, A; Orth, H; Otte, A N; Palit, R; Panebianco, S; Pullia, A; Raciti, G; Rapisarda, E; Rossi, D; Salsac, M -D; Sann, H; Schwarz, C; Simon, H; Sfienti, C; Sümmerer, K; Tsang, M B; Verde, G; Veselsky, M; Volant, C; Wallace, M; Weick, H; Wiechula, J; Wieloch, A; Zwiegliński, B

    2012-01-01

    The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment.

  16. Neutronic conceptual design of the ETRR-2 cold neutron source

    International Nuclear Information System (INIS)

    The conceptual neutronic design of the cold neutron source (CNS) for the Egyptian second research reactor (ETRR-2) was carried out using the MCNP code. A parametric analysis was also performed to choose the type and geometry of the moderator and the required CNS dimensions to maximize the cold neutron production. The moderator cell is a spherical annulus containing liquid hydrogen. The cold neutron gain and brightness are calculated together with the nuclear heat load of the CNS. The effects of void fraction in the moderator cell and the ortho:para ratios on cold neutron gain were calculated. (orig.)

  17. Neutron recognition in the LAND detector for large neutron multiplicity

    International Nuclear Information System (INIS)

    The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment.

  18. Scission neutron emission and prompt fission neutron spectrum

    International Nuclear Information System (INIS)

    The mass, energy and angular integrated spectra of prompt fission neutrons for 235U induced fission in the energy range from thermal to 5 MeV were analyzed. It allows assume that about 0.362±0.025 neutrons per fission are emitted due to another mechanism then neutron emission from excited fragments after full acceleration. The spectrum of scission neutrons consists of two components with average energy 0.98 MeV and 2.74 MeV. The share of scission neutrons and their spectrum shape estimated in this work does not contradict to results of differential experiments analyzed in previous papers. (author)

  19. Neutron guides and scientific neutron equipment at CILAS/GMI

    International Nuclear Information System (INIS)

    CILAS company is the world's leading supplier of complete neutron guides systems. The neutron optics with multilayer coatings produced by CILAS have become an international standard for neutron beam transportation in the modern research institutes. During the last 30 years, CILAS designed, produced and installed more than 5000 meters of guides in many European, American and Asian countries. To reinforce its leadership and presence in neutron research, CILAS acquired the company Grenoble Modular Instruments (GMI), a leading company in high precision mechanics, engineering and manufacturing of spectrometers and scientific equipment for neutron and synchrotron research. (author)

  20. Neutronic studies of the coupled moderators for spallation neutron sources

    Institute of Scientific and Technical Information of China (English)

    Yin Wen; Liang Jiu-Qing

    2005-01-01

    We investigate the neutronic performance of coupled moderators to be implemented in spallation neutron sources by Monte-Carlo simulation and give the slow neutron spectra for the cold and thermal moderators. CH4 moderator can provide slow neutrons with highly desirable characteristics and will be used in low-power spallation neutron soureces. The slow neutron intensity extracted from different angles has been calculated. The capability of moderation of liquid H2 is lower than H2O and liquid CH4 due to lower atomic number density of hydrogen but we can compensate for this disadvantage by using a premoderator. The H2O premoderator of 2cm thickness can reduce the heat deposition in the cold moderator by about 33% without spoiling the neutron pulse.

  1. The tokamak as a neutron source

    International Nuclear Information System (INIS)

    This paper describes the tokamak in its role as a neutron source, with emphasis on experimental results for D-D neutron production. The sections summarize tokamak operation, sources of fusion and non-fusion neutrons, principal neutron detection methods and their calibration, neutron energy spectra and fluxes outside the tokamak plasma chamber, history of neutron production in tokamaks, neutron emission and fusion power gain from JET and TFTR (the largest present-day tokamaks), and D-T neutron production from burnup of D-D tritons. This paper also discusses the prospects for future tokamak neutron production and potential applications of tokamak neutron sources. 100 refs., 16 figs., 4 tabs

  2. New Neutron Dosimeter

    CERN Multimedia

    2001-01-01

    CERN has been operating an Individual Dosimetry Service for neutrons for about 35 years. The service was based on nuclear emulsions in the form of film packages which were developed and scanned in the Service. In 1999, the supplier of theses packages informed CERN that they will discontinue production of this material. TIS-RP decided to look for an external service provider for individual neutron dosimetry. After an extensive market survey and an invitation for tender, a supplier that met the stringent technical requirements set up by CERN's host states for personal dosimeters was identified. The new dosimeter is based on a track-etching technique. Neutrons have the capability of damaging plastic material. The microscopic damage centres are revealed by etching them in a strong acid. The resulting etch pits can be automatically counted and their density is proportional to dose equivalent from neutrons. On the technical side, the new dosimeter provides an improved independence of its response from energy and th...

  3. Californium-252 neutron sources

    International Nuclear Information System (INIS)

    Major production programs for the Savannah River reactors and the High Flux Isotopes Reactor at Oak Ridge have made 252Cf one of the most available and, at the USAEC's sales price of $10/μg, one of the least-expensive isotopic neutron sources. Reactor production has totaled approximately 2 g, and, based on expected demand, an additional 10 g will be produced in the next decade. The approximately 800 mg chemically separated to date has been used to prepare over 600 neutron sources. Most, about 500, have been medical sources containing 1 to 5 μg of 252Cf plated in needles for experimental cancer therapy studies. The remainder have generally been point sources containing 10 μg to 12 mg of oxide for activation, well logging, or radiography uses. Bulk sources have also been supplied to the commercial encapsulators. The latest development has been the production of 252Cf cermet wire which can be cut into almost contamination-free lengths of the desired 252Cf content. Casks are available for transport of sources up to 50 mg. Subcritical assemblies have been developed to multiply the source neutrons by a factor of 10 to 40, and collimators and thermalizers have also been extensively developed to shape the neutron flux and energy distributions for special applications. (U.S.)

  4. Neutron scattering from fractals

    DEFF Research Database (Denmark)

    Kjems, Jørgen; Freltoft, T.; Richter, D.;

    1986-01-01

    -angle neutron scattering studies of the variation with aggregation rate are presented. These results allow a very detailed comparison to be made with the theoretical scattering curves. Preliminary incoherent inelastic data on the low-frequency dynamics of hydroxylated silica particle aggregates show a clear...

  5. Reactivity and neutron dynamics

    International Nuclear Information System (INIS)

    Basing on the results of experiments mad with the full-scale WWER-1000 reactor core the problems of simulating neutron distributed transients, reactivity role in their description and uncertainties connected with reactivity value determination are discussed. Adiabatic approximation application and reactivity insertions lead to multiplicative representation of the solution kinetics equation including amplitude multiplier and form function

  6. Neutron rich nuclei

    International Nuclear Information System (INIS)

    If some β- emitters are particularly interesting to study in light, medium, and heavy nuclei, another (and also) difficult problem is to know systematically the properties of these neutron rich nuclei far from the stability line. A review of some of their characteristics is presented. How far is it possible to be objective in the interpretation of data is questioned and implications are discussed

  7. Applied neutron resonance theory

    International Nuclear Information System (INIS)

    Utilisation of resonance theory in basic and applications-oriented neutron cross section work is reviewed. The technically important resonance formalisms, principal concepts and methods as well as representative computer programs for resonance parameter extraction from measured data, evaluation of resonance data, calculation of Doppler-broadened cross sections and estimation of level-statistical quantities from resonance parameters are described. (orig.)

  8. Neutron scattering from fractals

    DEFF Research Database (Denmark)

    Kjems, Jørgen; Freltoft, T.; Richter, D.; Sinha, S. K.

    -angle neutron scattering studies of the variation with aggregation rate are presented. These results allow a very detailed comparison to be made with the theoretical scattering curves. Preliminary incoherent inelastic data on the low-frequency dynamics of hydroxylated silica particle aggregates show a clear...

  9. Neutron protein crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Niimura, Nobuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-10-01

    X-ray diffraction of single crystal has enriched the knowledge of various biological molecules such as proteins, DNA, t-RNA, viruses, etc. It is difficult to make structural analysis of hydrogen atoms in a protein using X-ray crystallography, whereas neutron diffraction seems usable to directly determine the location of those hydrogen atoms. Here, neutron diffraction method was applied to structural analysis of hen egg-white lysozyme. Since the crystal size of a protein to analyze is generally small (5 mm{sup 3} at most), the neutron beam at the sample position in monochromator system was set to less than 5 x 5 mm{sup 2} and beam divergence to 0.4 degree or less. Neutron imaging plate with {sup 6}Li or Gd mixed with photostimulated luminescence material was used and about 2500 Bragg reflections were recorded in one crystal setting. A total of 38278 reflections for 2.0 A resolution were collected in less than 10 days. Thus, stereo views of Trp-111 omit map around the indol ring of Trp-111 was presented and the three-dimensional arrangement of 696H and 264D atoms in the lysozyme molecules was determined using the omit map. (M.N.)

  10. The violent neutron star

    OpenAIRE

    Watts, Anna L.

    2012-01-01

    Neutron stars enable us to study both the highest densities and the highest magnetic fields in the known Universe. In this article I review what can be learned about such fundamental physics using magnetar bursts. Both the instability mechanisms that trigger the bursts, and the subsequent dynamical and radiative response of the star, can be used to explore stellar and magnetospheric structure and composition.

  11. SLOWPOKE: neutron activation analysis

    International Nuclear Information System (INIS)

    Neutron activation analysis permits the non-destructive determination of trace elements in crude oil and its derivatives at high sensitivity (up to 10-9 g/g) and good precision. This article consists of a quick survey of the method followed by an illustration based on the results of recent work at the SLOWPOKE reactor laboratory at the Ecole Polytechnique

  12. Tomography with thermal neutrons

    International Nuclear Information System (INIS)

    This paper describes some tomographic measurements performed with thermal neutrons at the Instituto de Engenharia Nuclear - IEN/CNEN. The Argonauta Reactor at this Institute was used as neutron source. During the measurements this reactor produced a 36 x 105 n.cm-1.s-1 thermal neutron flux at end of the irradiation channel, wherein the tomographic system was installed. An homogeneous aluminum cylindrical rod was used to calibrate the system and to determine parameters governing the quality of the images. The aluminum cross section emerging from the image reconstruction process, was then compared with the values found in the literature. To evaluate the capability of this technique as a complementary tool, to the X-ray tomography, images of a solid aluminum cylinder, wherein, several thin rods of different materials were inserted, were taken. These materials were chosen among elements with high atomic numbers, as well as, among elements having a Z close to each other. A tomographic image of a small electric motor, displayed several elements of its internal structure. The overall results have demonstrated the capability of the thermal neutron tomography to complement the X-ray tomography, specially for samples containing elements of high atomic numbers such as lead (Z=82), or elements having atomic numbers close to each other such as iron (Z=26) and copper (Z=29). (author)

  13. Neutron multiplicity analysis tool

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Scott L [Los Alamos National Laboratory

    2010-01-01

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

  14. Air Force neutron dosimetry program

    International Nuclear Information System (INIS)

    Approximately 1000 Air Force personnel are monitored for neutron radiation resulting from various sources at more than thirty worldwide locations. Neutron radiation spanning several orders of magnitude in energy is encountered. The Air Force currently uses albedo thermoluminescent neutron dosimeters for personnel monitoring. The energy dependence of the albedo neutron dosimeter is a current problem and the development of site specific correction factors is ongoing. A summary of data on the energy dependence is presented as well as efforts to develop algorithms for the dosimeter. An overview of current Air Force neutron dosimetry users and needs is also presented

  15. A review on neutron reflectometry

    International Nuclear Information System (INIS)

    This report contains principle and characteristic of neutron reflectometry. Therefore, in case of operating neutron reflectometer at HANARO in future, it will be a reference to the user who wishes to use the instrument effectively. Also, the current situation of neutron reflectometer operating in the world was examined. The detail of neutron reflectometer such as GANS(MURR), ADAM(ILL), POSY II(ANL), ROG(IRI) was described. The recent research situation on neutron reflectometry was also examined and it helps us to determine research field. (author)

  16. The magnetic diffusion of neutrons

    International Nuclear Information System (INIS)

    The purpose of this report is to examine briefly the diffusion of neutrons by substances, particularly by crystals containing permanent atomic or ionic magnetic moments. In other words we shall deal with ferromagnetic, antiferromagnetic, ferrimagnetic or paramagnetic crystals, but first it is necessary to touch on nuclear diffusion of neutrons. We shall start with the interaction of the neutron with a single diffusion centre; the results will then be applied to the magnetic interactions of the neutron with the satellite electrons of the atom; finally we shall discuss the diffusion of neutrons by crystals. (author)

  17. The stationary neutron radiography system

    International Nuclear Information System (INIS)

    To provide the high intensity neutron beam and support systems necessary for radiography, the Stationary Neutron Radiography System was constructed at McClellan Air Force Base. The Stationary Neutron Radiography System utilizes a one megawatt TRIGA reactor contained in an Aluminium tank surrounded by eight foot thick concrete walls. There are four neutron beam tubes at inclined angles from the reactor core to separate radiography bays. In three of the bays, robotic systems manipulate aircraft components in the neutron beam, while real-time imaging systems provide images concurrent with the irradiation. Film radiography of smaller components is performed in the remaining bay

  18. Scintillating fibre tracking neutron detector

    International Nuclear Information System (INIS)

    A detector for measurements of collimated fluxes of neutrons in the energy range 2-20 MeV is proposed. It utilizes (n.p) elastic scattering in scintillating optical fibres placed in successive orthogonal layers perpendicular to the neutron flux. A test module has been designed, constructed and tested with respect to separation of neutron and gamma events. The pulse height measurements show the feasibility to discriminate between neutron, gamma and background events. Application to measurements of fusion neutrons is considered. 18 refs, 22 figs, 4 tabs

  19. BR2 reactor neutron beams

    International Nuclear Information System (INIS)

    The use of reactor neutron beams is becoming increasingly more widespread for the study of some properties of condensed matter. It is mainly due to the unique properties of the ''thermal'' neutrons as regards wavelength, energy, magnetic moment and overall favorable ratio of scattering to absorption cross-sections. Besides these fundamental reasons, the impetus for using neutrons is also due to the existence of powerful research reactors (such as BR2) built mainly for nuclear engineering programs, but where a number of intense neutron beams are available at marginal cost. A brief introduction to the production of suitable neutron beams from a reactor is given. (author)

  20. An optimized SVPWM switching strategy for three-level NPC VSI and a novel switching strategy for three-level two-quadrant chopper to stabilize the voltage of capacitors

    International Nuclear Information System (INIS)

    Voltage source inverter (VSI) can produce single and three-phase (3P) AC voltages from a constant or variable DC voltage. There are many ways to control the VSI output voltage. Each control way produces some harmonics at the VSI output voltage. The space vector pulse width modulation (SVPWM) may be more effective than other modulation methods, e.g. harmonic injection, phase shifting, multi career pulse width modulation, in decreasing the low order harmonics (LOH). Different switching strategies (SSs) of power electronic devices in SVPWM have some specific advantages and disadvantages with regard to one another. In this paper, a comparative study between different SVPWM SSs is carried out by considering some objective functions such as total harmonic distortion (THD), power and switching losses, the ratio of the harmonic components to the fundamental component, distortion factor (DF). It is also shown that by selecting an optimized and appropriate SS for SVPWM, the harmonic orders, which are the multiples of the frequency index (FI), are eliminated. Then, to investigate the impact of variations of the capacitors voltage and switching frequency on power quality criteria, the most appropriate and optimized SS is applied to a 3P three-level (3L) neutral-point-clamped (NPC) VSI to supply a 3P load. This paper also presents a novel and optimized SS and control approach for a 3L two-quadrant (2Q) chopper in NPC VSI superconducting magnetic energy storage (SMES). Using the proposed SS, the voltage of the VSI capacitors in SMES can be independently controlled; also, the minimum power and switching losses - as well as the proper convection - can be achieved using this same strategy. The simulation results indicate that when combined with a proportional-integral (PI) control approach the proposed SS can be easily implemented in the power networks and can balance and stabilize the multi-level VSIs' capacitor voltage level. The voltage variation of the capacitors in the steady