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Macrostrain measurement using radial collimators at LANSCE

Description: A series of `short` radial collimators have been implemented in the 90{degrees} scattering geometries on the neutron powder diffractometer at Los Alamos. The capability to perform macrostrain measurements has been improved by the commensurate ability to rapidly select a sampling volume appropriate to the specimen. The compact design of the collimators was dictated by the need to fit them in a cylindrical vacuum chamber as well as providing space in which to manipulate a specimen in three dimensions. Collimators of different vane lengths were fabricated to give 4 different resolutions for which 2/3 of the diffracted intensity comes form distances of 0.75, 1. 25, 2.5, and 4.0 mm along the incident beam. Qualifying scans and a demonstration of a cracked ring, containing a steep stress gradient, are included.
Date: June 1, 1996
Creator: Bourke, M.A.M.; Roberts, J.A. & Davis, D.
Partner: UNT Libraries Government Documents Department

Upgrade of the wide-angle neutron diffractometer at the high flux isotope reactor

Description: The Wide-Angle Neutron Diffractometer (WAND) is a flat-cone geometry diffractometer located at the High Flux Reactor (HFIR). This instrument is currently being upgraded. The central part of this upgrade is the development of a new curved one-dimensional position sensitive detector which covers a 125 degree angular range with an effective radius of 71 cm. This detector will be a multi-anode (624 anodes on a 0.2 degree pitch) {sup 3}He gas-filled proportional counter. This totally new system will give high resolution, good uniformity and high counting range - a maximum capability of 10{sup 5} cps/pixel and a 10{sup 7} cps overall. A prototype of this detector has shown that these design targets can be met. The new WAND will greatly broaden its capabilities for single-crystal diffraction experiments and for time-resolved measurements.
Date: July 15, 1997
Creator: Katano, S.; Morii, Y. & Child, H.R.
Partner: UNT Libraries Government Documents Department

POW3-workhorse powder diffractometer-reference instrument WBS 1.7.3.

Description: POW3 provides rapid data collection while maintaining reasonably good resolution. Figure 1 provides a schematic representation of POW3, and Table 1 gives the parameters for this instrument. This is a workhorse refinement instrument for structures of modest complexity. In addition, this instrument views a cold moderator to enable long-wavelength neutrons to be used to measure long d-spacings.
Date: January 20, 1999
Creator: Crawford, R.K.
Partner: UNT Libraries Government Documents Department

The new small-angle diffractometer SAND at IPNS

Description: A new small-angle neutron diffractometer SAND is undergoing commissioning at IPNS pulsed source. This paper provides details of the design and expected performance of this instrument.
Date: December 31, 1995
Creator: Crawford, R.K.; Thiyagarajan, P.; Epperson, J.E.; Trouw, F.; Kleb, R.; Wozniak, D. et al.
Partner: UNT Libraries Government Documents Department

Neutronic simulations for source-instrument matching at the Lujan Center

Description: The neutronics design of pulsed spallation neutron sources can be difficult when considering the fact that multiple instruments view the same moderator. Typically, the moderator design is a compromise between the required resolution for one instrument and the maximum intensity desires of another instrument. At the Manuel Lujan, Jr., Neutron Scattering Center (MLNSC), a recent target redesign has offered the opportunity to design a moderator for a Laue diffractometer with few other requirements. Detailed time and energy spectra were calculated for a variety of moderator decoupling options. The purpose of this summary is to document the neutronics calculations required for this source-instrument matching process.
Date: December 31, 1998
Creator: Court, J.D.; Ferguson, P.D. & Schoenborn, B.P.
Partner: UNT Libraries Government Documents Department

Upgrade of the Wide-Angle Neutron Diffractometer at the High-Flux Isotope Reactor

Description: The Wide-Angle Neutron Diffractometer (WAND) installed at the High-Flux Isotope Reactor (HFIR) has been upgraded for new experiments. The main feature of this upgrade is the replacement of its detector with a newly developed curved one-dimensional 3He position-sensitive counter composed of 624 individual anodes. From the results of test-measurements of the detector performance, it is found that the intrinsic angular resolution and the maximum neutron-counting rate per anode are 0.25 degrees and 2.0 x 10 counts/second, respectively.
Date: August 14, 2001
Creator: Ishii, Y.
Partner: UNT Libraries Government Documents Department

A design for a high resolution very-low-Q time-of flight diffractometer.

Description: The design of a high resolution view low-Q time of flight diffractometer was motivated by the anticipated need to perform small-angle neutron scattering measurements at far lower momentum transfer and higher precision than currently available at either pulsed or steady state sources. In addition, it was recognized that flexibility in the configuration of the instrument and ease in which data is acquired are important. The design offers two configurations, a high intensity/very low Q geometry employing a focusing mirror and a medium to high Q-precision/low Q configuration using standard pinhole collimation geometry. The quality of the mirror optics is very important to the performance of the high intensity/very low Q configuration. We believe that the necessary technology exists to fabricate the high quality mirror optics required for the instrument.
Date: September 29, 1998
Creator: Hjelm, R. P.
Partner: UNT Libraries Government Documents Department

Report on the workshop on Monte Carlo simulation of neutron scattering instruments

Description: The main purpose of this workshop was to reach a consensus concerning the desired features of a general computer program for source-to-detector Monte Carlo simulation of neutron scattering instruments. A second goal was to decide on a strategy for achieving this and to begin to portion out the tasks involved to avoid duplication of efforts among the various groups. The meeting was organized by Kent Crawford (Argonne National Laboratory) and attended by representatives of all the major US neutron scattering facilities and several of the European neutron scattering facilities. This document is a summary of the discussions that took place during the workshop. A copy of the meeting schedule is attached, as well as a list of participants.
Date: January 9, 1998
Creator: Crawford, R.K.
Partner: UNT Libraries Government Documents Department

Multi-purpose neutron radiography system

Description: A conceptual design is given for a low cost, multipurpose radiography system suited for the needs of the Los Alamos National Laboratory (LANL). The proposed neutron source is californium-252. One purpose is to provide an in-house capability for occasional, reactor quality, neutron radiography thus replacing the recently closed Omega-West Reactor. A second purpose is to provide a highly reliable standby transportable neutron radiography system. A third purpose is to provide for transportable neutron probe gamma spectroscopy techniques. The cost is minimized by shared use of an existing x-ray facility, and by use of an existing transport cask. The achievable neutron radiography and radioscopy performance characteristics have been verified. The demonstrated image qualities range from high resolution gadolinium - SR film, with L:D = 100:1, to radioscopy using a LIXI image with L:D = 30:1 and neutron fluence 3.4 x 10{sup 5} n/cm{sup 2}.
Date: July 1, 1996
Creator: Barton, J.P.; Bryant, L.E. & Berry, P.
Partner: UNT Libraries Government Documents Department

Instrumentation using cold neutrons at pulsed neutron sources

Description: This paper discusses some basic aspects of instrumentation for cold neutrons, with emphasis on conditions peculiar to pulsed sources. It also indicates the conditions under which pulsed source instruments can be most effective for cold neutron research, and presents a brief report on the status of cold neutron instrumentation at pulsed sources.
Date: September 1, 1997
Creator: Crawford, R.K.
Partner: UNT Libraries Government Documents Department

Design of a TOF-SANS instrument for the proposed Long Wavelength Target Station at the Spallation Neutron Source.

Description: We have designed a versatile high-throughput SANS instrument [Broad Range Intense Multipurpose SANS (BRIMS)] for the proposed Long Wavelength Target Station at the SNS by using acceptance diagrams and the Los Alamos NISP Monte Carlo simulation package. This instrument has been fully optimized to take advantage of the 10 Hz source frequency (broad wavelength bandwidth) and the cold neutron spectrum from a tall coupled solid methane moderator (12 cm x 20 cm). BRIMS has been designed to produce data in a Q range spanning from 0.001 to 0.7 {angstrom}{sup {minus}1} in a single measurement by simultaneously using neutrons with wavelengths ranging from 1 to 14.5 {angstrom} in a time of flight mode. A supermirror guide and bender assembly is employed to separate and redirect the useful portion of the neutron spectrum with {lambda} > 1 {angstrom}, by 2.3{degree} away from the direct beam containing high energy neutrons and {gamma} rays. The effects of the supermirror coating of the guide, the location of the bender assembly with respect to the source, the bend angle, and various collimation choices on the flux, resolution and Q{sub min} have been characterized using spherical particle and delta function scatterers. The overall performance of BRIMS has been compared with that of the best existing reactor-based SANS instrument D22 at ILL.
Date: November 28, 2000
Creator: Thiyagarajan, P.; Littrell, K. & Seeger, P. A.
Partner: UNT Libraries Government Documents Department

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

Description: Since superconductivity fever spread around the world, neutron powder diffraction has become very popular and been widely used by crystallographers, physicists, chemists, mineralogists, and materials scientists. The purpose of present paper is to show, firstly, important characteristics of time-of-flight TOF powder diffraction using cold-neutron source in the study of materials science, and, secondly, recent studies on the structure and function of batteries at the Neutron Science Laboratory (KENS) in the High Energy Accelerator Research Organization (KEK).
Date: December 1, 1997
Creator: Kamiyama, T.; Oikawa, K. & Akiba, E.
Partner: UNT Libraries Government Documents Department

SANS2-high-resolution small-angle diffractometer-reference instrument WBS 1.7.9.

Description: SANS2 is a general-purpose small-angle neutron scattering spectrometer providing relatively high resolution and relatively low minimum Q values. Figure 1 provides a schematic representation of SANS2, and Table 1 gives the parameters for this instrument. Because of the broad Q range sampled in a single measurement, this instrument will be particularly useful in the study of time-dependent phenomena, such as deformation/orientation and phase transformations in complex fluids and polymers.
Date: January 18, 1999
Creator: Crawford, R.K.
Partner: UNT Libraries Government Documents Department

Small-angle scattering instruments on a 1 MW long pulse spallation source

Description: Two small-angle neutron scattering instruments have been designed and optimized for installation at a 1 MW long pulse spallation source. The first of these instruments allows access to length scales in materials from 10 to 400 {angstrom}, and the second instrument from 40 to 1200 {angstrom}. Design characteristics were determined and optimization was done using the MCLIB Monte Carlo instrument simulation package. The code has been {open_quote}benchmarked{close_quote} by simulating the {open_quote}as-built{close_quote} D11 spectrometer at ILL and a performance comparison of the three instruments was made. Comparisons were made by evaluating the scattered intensity for {delta} scatterers at different Q values for various instrument configurations needed to span a Q-range of 0.0007 - 0.44 {angstrom}{sup {minus}1}.
Date: December 1, 1995
Creator: Olah, G.A.; Hjelm, R.P. & Seeger, P.A.
Partner: UNT Libraries Government Documents Department

The performance of the small-angle diffractometer, SAND at IPNS.

Description: The time-of-flight small-angle diffractometer SAND has been serving the scientific user community since 1996. One notable feature of SAND is its capability to measure the scattered intensity in a wide Q (4{pi}sin{theta}/{lambda}, where 2{theta} is the scattering angle and {lambda} is the wavelength of the neutrons) range of 0.0035 to 0.5 {angstrom}{sup {minus}1} in a single measurement. The optical alignment system makes it easy to set up the instrument and the sample. The cryogenically cooled MgO filter reduces the fast neutrons over two orders of magnitude, while still transmitting over 70% of the cold neutrons. A drum chopper running at 15 Hz suppresses the delayed neutron background. SAND has a variety of ancillary equipment to control the sample environment. In this paper we describe the features of the SAND instrument, compare its data on a few standard samples with those measured at well established centers in the world, and display two scientific examples which take advantage of measuring data in a wide Q-range in a single measurement. With a new set of tight collimators the Q{sub min} can be lowered to 0.002 {angstrom}{sup {minus}1} and the presently installed high-angle bank of detectors will extend the Q{sub max} to 2 {angstrom}{sup {minus}1}.
Date: July 17, 1998
Creator: Thiyagarajan, P.
Partner: UNT Libraries Government Documents Department

Experimental determination of residual stress by neutron diffraction in a boiling water reactor core shroud

Description: Residual strains in a 51 mm (2-inch) thick 304L stainless steel plate have been measured by neutron diffraction and interpreted in terms of residual stress. The plate, measuring (300 mm) in area, was removed from a 6m (20-ft.) diameter unirradiated boiling water reactor core shroud, and included a multiple-pass horizontal weld which joined two of the cylindrical shells which comprise the core shroud. Residual stress mapping was undertaken in the heat affected zone, concentrating on the outside half of the plate thickness. Variations in residual stresses with location appeared consistent with trends expected from finite element calculations, considering that a large fraction of the residual hoop stress was released upon removal of the plate from the core shroud cylinder.
Date: June 1, 1996
Creator: Payzant, A.; Spooner, S.; Zhu, Xiaojing & Hubbard, C.R.
Partner: UNT Libraries Government Documents Department

Intense Pulsed Neutron Source: Progress report 1991--1996. 15. Anniversary edition -- Volume 2

Description: The 15th Anniversary Edition of the IPNS Progress Report is being published in recognition of the Intense Pulsed Neutron Source`s first 15 years of successful operation as a user facility. To emphasize the importance of this milestone, the author shave made the design and organization of the report significantly different from previous IPNS Progress Reports. This report consists of two volumes. For Volume 1, authors were asked to prepare articles that highlighted recent scientific accomplishments at IPNS, from 1991 to present; to focus on and illustrate the scientific advances achieved through the unique capabilities of neutron studies performed by IPNS users; to report on specific activities or results from an instrument; or to focus on a body of work encompassing different neutron-scattering techniques. Articles were also included on the accelerator system, instrumentation, computing, target, and moderators. A list of published and ``in press` articles in journals, books, and conference proceedings, resulting from work done at IPNS since 1991, was compiled. This list is arranged alphabetically according to first author. Publication references in the articles are listed by last name of first author and year of publication. The IPNS experimental reports received since 1991 are compiled in Volume 2. Experimental reports referenced in the articles are listed by last name of first author, instrument designation, and experiment number.
Date: May 1, 1996
Partner: UNT Libraries Government Documents Department

Proceedings of a workshop on methods for neutron scattering instrumentation design

Description: The future of neutron and x-ray scattering instrument development and international cooperation was the focus of the workshop. The international gathering of about 50 participants representing 15 national facilities, universities and corporations featured oral presentations, posters, discussions and demonstrations. Participants looked at a number of issues concerning neutron scattering instruments and the tools used in instrument design. Objectives included: (1) determining the needs of the neutron scattering community in instrument design computer code and information sharing to aid future instrument development, (2) providing for a means of training scientists in neutron scattering and neutron instrument techniques, and (3) facilitating the involvement of other scientists in determining the characteristics of new instruments that meet future scientific objectives, and (4) fostering international cooperation in meeting these needs. The scope of the meeting included: (1) a review of x-ray scattering instrument design tools, (2) a look at the present status of neutron scattering instrument design tools and models of neutron optical elements, and (3) discussions of the present and future needs of the neutron scattering community. Selected papers were abstracted separately for inclusion to the Energy Science and Technology Database.
Date: September 1, 1997
Creator: Hjelm, R.P.
Partner: UNT Libraries Government Documents Department

Calculation of thermal diffuse scattering

Description: The authors developed a computer program to calculate the thermal diffuse scattering (TDS) intensity distribution for single crystal specimens in a diffractometer with no energy analysis. They assumed that the phonon frequencies are approximated by those of elastic waves and that the elastic constants, density and lattice parameters of the system under study are known. The results of the calculations were compared to experimental data obtained for single crystals of Si, diamond and NiAl at the Wide Angle neutron Diffractometer at the HFIR at Oak Ridge National Laboratory. Excellent agreement was found between the calculations and the experimental observations.
Date: July 14, 1997
Creator: Wakabayashi, N.; Nicklow, R.M.; Child, H.R.; Smith, H.G.; Fernandez-Baca, J.A.; Katano, S. et al.
Partner: UNT Libraries Government Documents Department

MLNSC instrument design and simulation package, task order 57 (modified). Final report, September 30, 1997

Description: The objectives of this task as described in Statement of Work have been met and the documents required as Deliverables have been prepared and submitted to the requester. Specifically, a document titled ``The MCLIB Library: Monte Carlo Simulation of Neutron Scattering Instruments,`` revised September 23, 1997, includes documentation of new standards, code revisions and additions, and some improved efficiency due to improved optimization strategies. The procedures for user implementation of new optical devices, and information on using the package and reading and viewing the output have also been included. Second, a new document entitled ``MCLIB Element Definitions and Help`` was written and revised through the duration of the task, to supply the needed input to group CIC-15 for the purpose of integrating the MCLIB package with a web-based user interface. Finally, an application of the package was presented and a (successful) demonstration of the new user interface was given at a workshop at Argonne National Laboratory, August 24--26, 1997, as described in the modification to the Statement of Work.
Date: October 3, 1997
Creator: Seeger, P.A.
Partner: UNT Libraries Government Documents Department

Neutron scattering instruments for the Spallation Neutron Source (SNS)

Description: The Spallation Neutron Source (SNS) is a 1 MW pulsed spallation source for neutron scattering planned for construction at Oak Ridge National Laboratory. This facility is being designed as a 5-laboratory collaboration project. This paper addresses the proposed facility layout, the process for selection and construction of neutron scattering instruments at the SNS, the initial planning done on the basis of a reference set of ten instruments, and the plans for research and development (R and D) to support construction of the first ten instruments and to establish the infrastructure to support later development and construction of additional instruments.
Date: July 1, 1998
Creator: Crawford, R.K.; Fornek, T. & Herwig, K.W.
Partner: UNT Libraries Government Documents Department

Towards 0.1 MM Spatial Resolution

Description: A design goal for VULCAN, the SNS engineering diffractometer, is to enable spatial mapping with 0.1 mm resolution. Because the targeted applications often involve the use of large samples or special environment, slits cannot be used for this purpose. In this paper, methods to achieve 0.1 mm spatial resolution are outlined. For the incident beam, a new compact focusing device is proposed. The device is made of a stack of bent silicon wafers, each having a reflective multilayer (supermirror) deposited on one side and a neutron-absorbing layer on the other side. The optimal design to minimize the optical spatial aberrations is discussed and Monte-Carlo simulation results are presented. For the diffracted beam, imaging devices made from thick packets of diffracting bent silicon wafers (known as the Bragg Mirrors) could be used. The requirements to achieve a sharp imaging together with a large phase-space acceptance window are discussed and preliminary testing results are presented.
Date: July 26, 2001
Creator: Stoica, A.D.
Partner: UNT Libraries Government Documents Department

Flux Gain for Next-Generation Neutron-Scattering Instruments Resulting From Improved Supermirror Performance

Description: Next-generation spallation neutron source facilities will offer instruments with unprecedented capabilities through simultaneous enhancement of source power and usage of advanced optical components. The Spallation Neutron Source (SNS), already under construction at Oak Ridge National Laboratory and scheduled to be completed by 2006, will provide greater than an order of magnitude more effective source flux than current state-of-the-art facilities, including the most advanced research reactors. An additional order of magnitude gain is expected through the use of new optical devices and instrumentation concepts. Many instrument designs require supermirror (SM) neutron guides with very high critical angles for total reflection. In this contribution, they discuss how the performance of modern neutron scattering instruments depends on the efficiency of these supermirrors. They outline ideas for enhancing the performance of the SM coatings, particularly for improving the reflectivity at the position of the critical wave vector transfer. A simulation program has been developed which allows different approaches for SM designs to be studied. Possible instrument performance gains are calculated for the example of the SNS reflectometer.
Date: July 11, 2001
Creator: Rehm, C.
Partner: UNT Libraries Government Documents Department