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The Investigation of Fundamental Interactions with Cold Neutrons

Description: Abstract: The National Bureau of Standards is establishing a National Cold Neutron Facility at its 20 MW reactor located in Gaithersburg, Maryland. In order to provide guidance in the development of research plans for the Facility, the Department of Energy and NBS sponsored, on November 14-15, 1985, a workshop on the Investigation of Fundamental Interactions with Cold Neutrons. The 25 papers presented at the workshop are printed in the proceedings.
Date: February 1986
Creator: Greene, G. L.
Partner: UNT Libraries Government Documents Department

Spin dynamics of Li Doped La[sub 2]CuO[sub 4]with a disordered ground state

Description: Only 3% hole doping by Li is sufficient to suppress the long-range antiferromagnetic order in LazCu04. Spin dynamics in the disordered state was investigated by measuring the dynamic magnetic structure factor, S(q,w), as a function of temperature, using cold neutron spectroscopy, on La2Cuo.96Lio.0404a nd La{approx}Cuo.gLio.104s ingle crystals. The details of observed spin dynamics of the quantum disordered spin liquid were compared to the theoretical results of the nonlinear u model for a two dimensional Heisenberg antiferromagnet, which predicts a phase crossover upon cooling from a quantum critical regime of a quantum spin liquid to its quantum paramagnetic regime.
Date: January 1, 2002
Creator: Chen, Y.; Bao, W. (Wei); Sarrao, John L.,; Park, S.-H. L. (Park, S.-H. Lee) & Lorenzo, J. E.
Partner: UNT Libraries Government Documents Department

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

Description: An Integrated Circuit (IC) readout chip with four channels arranged so as to receive input charge from the corners of the chip was designed for use with 5- to 7-mm pixel detectors. This Application Specific IC (ASIC) can be used for cold neutron imaging, for study of structural order in materials using cold neutron scattering or for particle physics experiments. The ASIC is fabricated in a 0.5-{micro}m n-well AMI process. The design of the ASIC and the test measurements made is reported. Noise measurements are also reported.
Date: May 19, 2004
Creator: Britton, C.L.; Jagadish, U. & Bryan, W.L.
Partner: UNT Libraries Government Documents Department

NEER/Development of a Large-Field Cold Neutron Source

Description: By comparison with thermal neutrons, cold neutrons are attenuated to a greater extent by elements such as H, O, N, B, Cd, Gd and to a leser extent by metals such as Be, Al, Fe, Zr, Sn, W, Bi, Pb. Such unique nuclear properties to interact with materials enable to provide better non-destructive inspections.
Date: October 9, 2007
Creator: Glocchini, Robert & Bynoe, Deena
Partner: UNT Libraries Government Documents Department

Development of an ultra cold neutron source at MLNSC

Description: Ultra Cold Neutrons (UCN) can be produced at spallation sources using a variety of techniques. To date the technique used has been to Bragg scatter and Doppler shift cold neutrons into UCN from a moving crystal. This is particularly applicable to short-pulse spallation sources. We are presently constructing a UCN source at LANSCE using this method. In addition, large gains in UCN density should be possible using cryogenic UCN sources. Research is under way at Gatchina to demonstrate technical feasibility of a frozen deuterium source. If successful, a source of this type could be implemented at future spallation sources, such as the long pulse source being planned at Los Alamos, with a UCN density that may be two orders of magnitude higher than that presently available at reactors.
Date: September 1, 1996
Creator: Seestrom, S.J.; Bowles, T.J.; Hill, R.; Greene, G.L. & Morris, C.L.
Partner: UNT Libraries Government Documents Department

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

Description: Funds were received for the first year of a three year DOE Nuclear Engineering Research Grant, ``Study of Neutron Focusing at the Texas Cold Neutron Source`` (FGO2-92ER75711). The purpose of this three year study was to develop a neutron focusing system to be used with the Texas Cold Neutron Source (TCNS) to produce an intense beam of neutrons. A prompt gamma activation analysis (PGAA) facility was also to be designed, setup, and tested under the three year project. During the first year of the DOE grant, a new procedure was developed and used to design a focusing converging guide consisting of truncated rectangular cone sections. Detailed calculations were performed using a 3-D Monte Carlo code which we wrote to trace neutrons through the curved guide of the TCNS into the proposed converging guide. Using realistic reflectivities for Ni-Ti supermirrors, we obtained gains of 3 to 5 for the neutron flux averaged over an area of 1 {times} 1 cm.
Date: March 6, 1995
Creator: Wehring, B.W. & Uenlue, K.
Partner: UNT Libraries Government Documents Department

Status Report on the Spallation Neutron Source

Description: The purpose of the Spallation Neutron Source Project (SNS) is to generate low-energy neutrons (ambient [{approximately}200 meV] and cold [{approximately}50 meV]) which can be used by up to 18 neutron beam lines to study the structure and functionality of materials. The neutrons are generated by the spallation process initiated by the interactions of 1-GeV protons with a Hg target. These neutrons are reflected by a Pb reflector and are moderated by 2 water (ambient) and 2 super critical hydrogen (cryogenic) moderators. The pulse structure for the 1 MW proton beam is 60 Hertz and < 0.7 {micro}s/pulse. The facility must be upgradable to higher power levels (2- and 4- MW) with minimal operational interruptions. Although not included in the current funding or baseline, a second target station and associated support structure which will be designed to utilize cold neutrons is also considered to be an upgrade that must be incorporated with minimal impact on operations.
Date: October 12, 1998
Creator: Gabriel, T.A.
Partner: UNT Libraries Government Documents Department

The High Flux Isotope Reactor (HFIR) cold source project at ORNL

Description: The scope of this project includes the development, design, procurement/fabrication, testing, and installation of all of the components necessary to produce a working cold source within an existing HFIR beam tube hole in the pressure vessel. All aspects of the cold source design will be based on demonstrated technology adapted to the HFIR design and operating conditions.
Date: May 1, 1998
Creator: Selby, D.
Partner: UNT Libraries Government Documents Department

Technology Development for Cold Neutron Spallation Science

Description: This is the final report of a Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National laboratory (LANL). The purpose of the activities supported by this project were the development of new techniques; both experimental and theoretical that will allow more effective exploitation of spallation neutron sources.
Date: July 16, 1999
Creator: Greene, G.
Partner: UNT Libraries Government Documents Department

High Flux Isotope Reactor cold neutron source reference design concept

Description: In February 1995, Oak Ridge National Laboratory`s (ORNL`s) deputy director formed a group to examine the need for upgrades to the High Flux Isotope Reactor (HFIR) system in light of the cancellation of the Advanced neutron Source Project. One of the major findings of this study was that there was an immediate need for the installation of a cold neutron source facility in the HFIR complex. In May 1995, a team was formed to examine the feasibility of retrofitting a liquid hydrogen (LH{sub 2}) cold source facility into an existing HFIR beam tube. The results of this feasibility study indicated that the most practical location for such a cold source was the HB-4 beam tube. This location provides a potential flux environment higher than the Institut Laue-Langevin (ILL) vertical cold source and maximizes the space available for a future cold neutron guide hall expansion. It was determined that this cold neutron beam would be comparable, in cold neutron brightness, to the best facilities in the world, and a decision was made to complete a preconceptual design study with the intention of proceeding with an activity to install a working LH{sub 2} cold source in the HFIR HB-4 beam tube. During the development of the reference design the liquid hydrogen concept was changed to a supercritical hydrogen system for a number of reasons. This report documents the reference supercritical hydrogen design and its performance. The cold source project has been divided into four phases: (1) preconceptual, (2) conceptual design and testing, (3) detailed design and procurement, and (4) installation and operation. This report marks the conclusion of the conceptual design phase and establishes the baseline reference concept.
Date: May 1, 1998
Creator: Selby, D.L.; Lucas, A.T. & Hyman, C.R.
Partner: UNT Libraries Government Documents Department

Materials Selection for the HFIR Cold Neutron Source

Description: In year 2002 the High Flux Isotope Reactor (HFIR) will be fitted with a source of cold neutrons to upgrade and expand its existing neutron scattering facilities. The in-reactor components of the new source consist of a moderator vessel containing supercritical hydrogen gas moderator at a temperature of 20K and pressure of 15 bar, and a surrounding vacuum vessel. They will be installed in an enlarged beam tube located at the site of the present horizontal beam tube, HB-4; which terminates within the reactor's beryllium reflector. These components must withstand exceptional service conditions. This report describes the reasons and factors underlying the choice of 6061-T6 aluminum alloy for construction of the in-reactor components. The overwhelming considerations are the need to minimize generation of nuclear heat and to remove that heat through the flowing moderator, and to achieve a minimum service life of about 8 years coincident with the replacement schedule for the beryllium reflector. 6061-T6 aluminum alloy offers the best combination of low nuclear heating, high thermal conductivity, good fabricability, compatibility with hydrogen, superior cryogenic properties, and a well-established history of satisfactory performance in nuclear environments. These features are documented herein. An assessment is given of the expected performance of each component of the cold source.
Date: August 24, 2001
Creator: Farrell, K.
Partner: UNT Libraries Government Documents Department

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

Description: One area in which the Standard Model can be probed is neutron beta decay. In particular, measurements of angular correlations in neutron beta decay can place constraints on the existence of right-handed currents, the presence of scalar and tensor terms in the weak interaction, and for evidence of Time Reversal Violation, which is expected from the observed violation of CP invariance in kaon decay. A measurement of A, the correlation between the neutron spin and the direction of emission of the electron in neutron decay, can be combined with the neutron lifetime to determine the fundamental vector and axial vector weak coupling constants G{sub A} and G{sub V}. The authors have presented the essential elements of their plans to carry out an A correlation measurement using the UCN source they have constructed at the Manuel Lujan Neutron Scattering Center (MLNSC). Their goal is an initial measurement with an accuracy of about 0.2% of A (which has a value of about {minus}0.114). The count rate expected in the experiment will allow a determination at this statistical accuracy level in a running time of about four months.
Date: December 1, 1998
Creator: Seestrom, S.J. & Collaboration, UCN A
Partner: UNT Libraries Government Documents Department

Small angle neutron scattering analysis of novel carbons for lithium secondary batteries.

Description: Small angle neutron scattering analyses of carbonaceous materials used as anodes in lithium ion cells have been performed. The carbons have been synthesized using pillared clays (PILCs) as inorganic templates. Pillared clays are layered silicates whose sheets have been permanently propped open by sets of thermally stable molecular props. The calcined PILC was loaded with five different organic precursors and heated at 700 C under nitrogen. When the inorganic pillars were removed by acid treatment, carbon sheets are produced with holes. The fitting of the data in the high q region suggested that the carbon sheets have voids with radii ranging from 4 to 8 {angstrom}. Similar radii were obtained for the PILC and PILC/organic precursor, which suggests that the carbon was well distributed in the clay prior to pyrolysis.
Date: January 14, 1998
Creator: Sandi, G.; Thiyagarajan, P.; Winans, R. & Carrado, K.
Partner: UNT Libraries Government Documents Department

Spin-echo resolved grazing incidence scattering (ESRGIS) of cold neutrons.

Description: The conceptual design of a new instrument is presented, which makes use of the spin echo technique to analyze the scattering angle of neutrons impinging upon a rough or corrugated surface at grazing incidence. In a grazing incidence geometry the roughness of the surface and of submersed interfaces give rise to a neutron scattering pattern at angles well resolved from that of specular reflection for corrugation lengths up to several microns, but only in the plane of specular reflection. In contrast, scattering caused by corrugations of comparable length perpendicular to the reflection plane is limited to angles that can be separated only with an extreme tightening of the instrumental resolution. However this scattering can be well resolved by spin-echo methods for polarized neutrons. Results from scattering in and out of the reflection plane provide complementary information on the structure of the roughness and its location in a system with complex layering. This spin-echo technique may also distinguish static from time-dependent roughness.
Date: August 12, 2002
Creator: Felcher, G. P.; te Velthuis, S. G. E.; Major, J.; Dosch, H.; Anderson, C.; Habicht, K. et al.
Partner: UNT Libraries Government Documents Department

A measurement of the parity-violating gamma-ray asymmetry in the neutron-proton capture

Description: The {rvec n} + p {yields} d + {gamma} experiment under construction at LANSCE studies the weak interaction between neutrons and protons. The experiments will measure the directional dependence of the parity-violating {gamma}-ray asymmetry, A{sub {gamma}}, in the polarized cold neutron capture by para-hydrogen. The goal is to measure A{sub {gamma}} with uncertainty of 0.5 x 10{sup -8}, 10% of its predicted value. A{sub {gamma}} primarily isolates the {Delta}I = 1 component of the hadronic weak interaction and thus will determine the long-range weak pion-nucleon coupling constant H{sub {pi}}{sup 1}. The experiment is carefully designed for the LANSCE pulsed spallation neutron source to achieve the proposed statistical precision and to control systematic errors. We discuss the experiment and its status.
Date: January 1, 2002
Creator: Penttila, S. I. (Seppo I.); Bowman, J. D. (J. David); Carlini, R. D. (Roger D.); Case, T.; Chupp, T. E.; Coulter, K. P. et al.
Partner: UNT Libraries Government Documents Department

Source Terms for HFIR Beam Tube Shielding Analyses, and a Complete Shielding Analysis of the HB-3 Tube

Description: The High Flux Isotope Reactor (HFIR) at the Oak Ridge National Laboratory is in the midst of a massive upgrade program to enhance experimental facilities. The reactor presently has four horizontal experimental beam tubes, all of which will be replaced or redesigned. The HB-2 beam tube will be enlarged to support more guide tubes, while the HB-4 beam tube will soon include a cold neutron source.
Date: July 1, 2000
Creator: Bucholz, J.A.
Partner: UNT Libraries Government Documents Department

A Drabkin energy filter for experiments at a spallation neutron source.

Description: We present a new approach for dynamic monochromatization of neutrons suitable for time-of-flight experiments at spallation neutron sources. The method requires polarized neutrons and is based on the Drabkin energy filter. In its initial application, this magnetic resonator device, consisting of a polarizer/analyzer system and a wavelength-dependent spin flipper, was proposed for extracting a narrow bandwidth from a broad bandwidth polarized neutron beam. At a spallation neutron source, wavelength is determined by time-of-flight (TOF) from the source to the detector. However, at each instant a spread of wavelengths is recorded due to the non-zero emission time of the source/moderator system. Particularly, high-intensity moderators for cold neutrons produce long ''tails'' in the intensity/time distribution for all wavelengths, degrading the resolution of the experiments. The Drabkin energy filter can be used to cut the neutron tails for all wavelengths, by drifting the resonance condition in synchronization with the TOF. Calculations show that the method is viable, and that substantial resolution gains are obtained by application to a TOF neutron reflectometer.
Date: November 21, 2000
Creator: Parizzi, A. A.; Felcher, G. P. & Klose, F.
Partner: UNT Libraries Government Documents Department

Cold-moderator scattering kernel methods

Description: An accurate representation of the scattering of neutrons by the materials used to build cold sources at neutron scattering facilities is important for the initial design and optimization of a cold source, and for the analysis of experimental results obtained using the cold source. In practice, this requires a good representation of the physics of scattering from the material, a method to convert this into observable quantities (such as scattering cross sections), and a method to use the results in a neutron transport code (such as the MCNP Monte Carlo code). At Los Alamos, the authors have been developing these capabilities over the last ten years. The final set of cold-moderator evaluations, together with evaluations for conventional moderator materials, was released in 1994. These materials have been processed into MCNP data files using the NJOY Nuclear Data Processing System. Over the course of this work, they were able to develop a new module for NJOY called LEAPR based on the LEAP + ADDELT code from the UK as modified by D.J. Picton for cold-moderator calculations. Much of the physics for methane came from Picton`s work. The liquid hydrogen work was originally based on a code using the Young-Koppel approach that went through a number of hands in Europe (including Rolf Neef and Guy Robert). It was generalized and extended for LEAPR, and depends strongly on work by Keinert and Sax of the University of Stuttgart. Thus, their collection of cold-moderator scattering kernels is truly an international effort, and they are glad to be able to return the enhanced evaluations and processing techniques to the international community. In this paper, they give sections on the major cold moderator materials (namely, solid methane, liquid methane, and liquid hydrogen) using each section to introduce the relevant physics for that material and to show ...
Date: August 1, 1998
Creator: MacFarlane, R.E.
Partner: UNT Libraries Government Documents Department

Neutron beam characterization at the Intense Pulsed Neutron Source.

Description: The Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory is a spallation neutron source dedicated to materials research. Its three cryogenic methane moderators provide twelve neutron beams to fourteen neutron scattering instruments and test facilities. The moderators at IPNS are of cryogenic methane (CH{sub 4}); one of liquid methane at 100 K, and two of solid methane at 30 K. These moderators produce intense beams of both cold and thermal neutrons. The moderators are each of a different physical configuration in order to tailor their performance for the instruments and facilities that operate on the neutron beams. As part of the ongoing operation of IPNS, as well as new enhancements to the target, moderator, and reflector systems, we have performed experiments characterizing the energy and time distribution of neutrons in the various beams. These measurements provide absolutely normalized energy spectra using foil activation techniques joined with time-of-flight measurements, and energy-dependent time distributions using a time-focused crystal analyzer. The IPNS accelerator system delivers 14 {micro}A of 450 MeV protons, in 100 ns pulses at 30 Hz, to a target composed of water-cooled depleted uranium disks. The solid methane ''H'' moderator is 100 by 100 by 45 mm in size, centerline poisoned with 0.25 mg/mm{sup 2} gadolinium, and decoupled from the graphite reflector with 0.5 mm of cadmium. The liquid methane ''F'' moderator, which is viewed from both faces, is also 100 by 100 by 45 mm in size, gadolinium poisoned 16 mm below each of the two viewed surfaces, and decoupled from the graphite reflector with cadmium. The solid methane ''C'' moderator has a re-entrant ''grooved'' geometry. The moderator is 100 by 100 by 80 mm overall, with 40 mm deep 12 mm wide horizontal grooves in the viewed surface. These grooves cover 50% of the viewed surface area. The ...
Date: May 18, 1998
Creator: Iverson, E. B.
Partner: UNT Libraries Government Documents Department

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

Description: The presence of trace amounts of hydrogen in niobium is believed to have a detrimental effect on the mechanical and superconducting properties. Unfortunately, few techniques are capable of measuring hydrogen at these levels. We have developed two techniques for measuring hydrogen in materials. Cold neutron prompt gamma-ray activation analysis (PGAA) has proven useful for the determination of hydrogen and other elements in a wide variety of materials. Neutron incoherent scattering (NIS), a complementary tool to PGAA, has been used to measure trace hydrogen in titanium. Both techniques were used to study the effects of vacuum heating and chemical polishing on the hydrogen content of superconducting niobium.
Date: November 1, 2002
Creator: Paul, R.L.; Cheu-Maya, H.H. & Myneni, G.R.
Partner: UNT Libraries Government Documents Department