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Hjelm, R.P.
Los Alamos National Lab., NM (United States). Funding organisation: USDOE Office of Energy Research, Washington, DC (United States)1998
Los Alamos National Lab., NM (United States). Funding organisation: USDOE Office of Energy Research, Washington, DC (United States)1998
AbstractAbstract
[en] The neutron scattering methods, small-angle neutron scattering and neutron reflectometry, provide information on the structure of polymer composite materials that is not available from other structural probes. The unique capabilities of these methods derive from three factors. First, the length scales probed correspond to polymer conformation, molecular and domain scales and to the characteristic sizes of many fillers. Second, neutrons are able to penetrate relatively thick samples, allowing bulk samples to be measured, and enabling buried interfaces to be studied. This characteristic also allows for the construction of special sample containment needed for studying materials under stress, extremes in pressure and temperature, etc. Third, neutrons readily distinguish between different light elements, and between different isotopes of the same element. The ability to distinguish between hydrogen and deuterium is particularly important in this regard. New ways of exploiting the capabilities of neutrons are opening up with the development of improved sources and instruments in the US and elsewhere. In this talk the author will discuss the basic concepts that give rise to the unique capabilities of neutron scattering, giving several examples of the uses of neutron scattering techniques in the study of polymer composites. The examples will include the morphology of fillers, polymer binders and matrices, interfaces and defect structures
Source
1998; 13 p; 153. technical meeting of the American Chemical Society Rubber Division; Indianapolis, IN (United States); 5-8 May 1998; CONF-9805133--; CONTRACT W-7405-ENG-36; ALSO AVAILABLE FROM OSTI AS DE99001135; NTIS; INIS; US GOVT. PRINTING OFFICE DEP
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Report
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Hjelm, R.P.
Los Alamos National Lab., NM (United States). Funding organisation: US Department of Energy (United States)2000
Los Alamos National Lab., NM (United States). Funding organisation: US Department of Energy (United States)2000
AbstractAbstract
No abstract available
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1 Mar 2000; 5 p; American Chemical Society National Meeting; San Francisco, CA (United States); 26-30 Mar 2000; W-7405-ENG-36; Also available from OSTI as DE00763999; PURL: https://www.osti.gov/servlets/purl/763999-dmbPD4/webviewable/
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Report
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Hjelm, R.P.; Seeger, P.A.
International seminar on structural investigations on pulsed neutron sources. Proceedings1993
International seminar on structural investigations on pulsed neutron sources. Proceedings1993
AbstractAbstract
[en] The implementation of small-angle (Low-momentum transfer) neutron scattering instruments at pulsed spallation sources, using time of flight methods, has meant the introduction of some new ideas in instrument design, data acquisition, data reduction and computer management of the experiment and the data. Here we recount some of the salient aspects of solutions for implementing time of flight small-angle neutron scattering instruments at pulsed sources, as realized on the LOW-Q Diffractometer, LQD, at Los Alamos. 10 figs
Source
Aksenov, V.L.; Balagurov, A.M.; Taran, Yu.V. (eds.); Joint Inst. for Nuclear Research, Dubna (Russian Federation); 341 p; 1993; p. 163-175; JINR; Dubna (Russian Federation); ISSI: international seminar on structural investigations on pulsed neutron sources; Dubna (Russian Federation); 1-4 Sep 1992
Record Type
Miscellaneous
Literature Type
Conference
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Mang, J.T.; Hjelm, R.P.
Los Alamos National Lab., NM (United States). Funding organisation: USDOE Assistant Secretary for Human Resources and Administration, Washington, DC (United States)1997
Los Alamos National Lab., NM (United States). Funding organisation: USDOE Assistant Secretary for Human Resources and Administration, Washington, DC (United States)1997
AbstractAbstract
[en] Small angle neutron scattering (SANS) was used to investigate the structure of mixed colloids of egg yolk phosphatidylcholine (EYPC) with the bile salt, cholylglycine (CG), in D2O as a function of pressure (P) and temperature (T). At atmospheric pressure, the system forms an isotropic phase of mixed, single bilayer vesicles (SLV's). Increasing the external hydrostatic pressure brought about significant changes in particle morphology. At T = 25 C, application of a pressure of 3.5 MPa resulted in the collapse of the SLV's. Further increase of P, up to 51.8 MPa, resulted in a transition from a phase of ordered (stacked), collapsed vesicles to one of stacked, ribbon-like particles. A similar collapse of the vesicles was observed at higher temperature (T = 37 C) with increasing P, but at this temperature, no ribbon phase was found at the highest pressure explored
Source
1997; 18 p; 13. symposium on thermophysical properties; Boulder, CO (United States); 22-27 Jun 1997; CONF-970629--1; CONTRACT W-7405-ENG-36; Also available from OSTI as DE97008153; NTIS; US Govt. Printing Office Dep
Record Type
Report
Literature Type
Conference; Numerical Data
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Reference NumberReference Number
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INIS IssueINIS Issue
Seeger, P.A.; Hjelm, R.P.
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1993
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1993
AbstractAbstract
[en] Low-Q diffractometers at spallation sources that use time of flight methods have been successfully implemented at several facilities, including the Los Alamos Neutron Scattering Center. The proposal to build new, more powerful, advanced spallation sources using advanced moderator concepts will provide luminosity greater than 20 times the brightest spallation source available today. These developments provide opportunity and challenge to expand the capabilities of present instruments with new designs. The authors review the use of time of flight for low-Q measurements and introduce new designs to extend the capabilities of present-day instruments. They introduce Monte Carlo methods to optimize design and simulate the performance of these instruments. The expected performance of the new instruments are compared to present day pulsed source- and reactor-based small-angle neutron scattering instruments. They review some of the new developments that will be needed to use the power of brighter sources effectively
Source
1993; 24 p; 1993 annual meeting of the American Crystallographic Association (ACA); Albuquerque, NM (United States); 24-28 May 1993; CONF-9305188--2; CONTRACT W-7405-ENG-36; OSTI as DE93016600; NTIS; INIS; US Govt. Printing Office Dep.
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Report
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Conference
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INIS IssueINIS Issue
Time-of-flight small-angle neutron scattering data reduction and analysis at LANSCE with program SMR
Hjelm, R.P. Jr.; Seeger, P.A.
Los Alamos National Lab., NM (USA)1988
Los Alamos National Lab., NM (USA)1988
AbstractAbstract
[en] A user-friendly integrated system, SMR, for the display, reduction and analysis of data from time-of-flight small-angle neutron diffractometers is described. Its purpose is to provide facilities for data display and assessment, and to provide these facilities in near real time. This allows the results of each scattering measurement to be available almost immediately, and enables the user to use the results of a measurement as a basis for other measurements in the same time allocation of the instrument. 8 refs., 10 figs
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Source
1988; 39 p; International collaboration on advanced neutron sources (ICANS); Los Alamos, NM (USA); 3-7 Oct 1988; CONF-8810182--13; Available from NTIS, PC A03/MF A01 - OSTI; 1 as DE89006520; Portions of this document are illegible in microfiche products.
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Report
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Conference
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INIS IssueINIS Issue
Hjelm, R.P. Jr.; Seeger, P.A.
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1992
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1992
AbstractAbstract
[en] The implementation of small-angle (Low-momentum transfer) neutron scattering at pulsed spallation sources, using time of flight methods, has meant the introduction of some new ideas in instrument design, data acquisition, data reduction and computer management of the experiment and the data. Here we recount some of the salient aspects of solutions for implementing time of fight small-angle neutron scattering instruments at pulsed sources, as realized on the Low-Q Diffractometer, LQD, at Los Alamos. We consider, fortlier, some of the problems that are yet to be solved, and take a short excursion into the future of SANS instrumentation at pulsed sources
Secondary Subject
Source
1992; 13 p; International seminar on structural investigation at pulsed neutron sources; Dubna (Russian Federation); 1-4 Sep 1992; CONF-9209225--2; CONTRACT W-7405-ENG-36; OSTI as DE93003702; NTIS; INIS; US Govt. Printing Office Dep
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Report
Literature Type
Conference
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INIS IssueINIS Issue
Seeger, P.A.; Hjelm, R.P. Jr.
Los Alamos National Lab., NM (USA)1990
Los Alamos National Lab., NM (USA)1990
AbstractAbstract
[en] The importance of small-angle neutron scattering (SANS) in biological, chemical, physical, and engineering research mandates that all intense neutron sources be equipped with SANS instruments. Four existing instruments are described, and the general differences between pulsed-source and reactor-based instrument designs are discussed. The basic geometries are identical, but dynamic range is achieved by using a broad band of wavelengths (with time-of-flight analysis) rather than by moving the detector. This allows a more optimized collimation system. Data acquisition requirements at a pulsed source are more severe, requiring large, fast histogramming memories. Data reduction is also more complex, as all wave length-dependent and angle-dependent backgrounds and non-linearities must be accounted for before data can be transformed to intensity vs Q. A comparison is shown between the Los Alamos pulsed instrument and D-11 (Institute Laue-Langevin), and examples from the four major topics of the conference are shown. The general conclusion is that reactor-based instruments remain superior at very low Q or if only a narrow range of Q is required, but that the current generation of pulsed-source instruments is competitive at moderate Q and may be faster when a wide range of Q is required. In principle, a user should choose which facility to use on the basis of optimizing the experiment; in practice the tradeoffs are not severe and the choice is usually made on the basis of availability
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Secondary Subject
Source
1990; 22 p; 8. international conference on small-angle scattering; Leuven (Belgium); 6-10 Aug 1990; CONF-9008173--1; CONTRACT W-7405-ENG-36; OSTI as DE91004870; NTIS; INIS; US Govt. Printing Office Dep
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Report
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Olah, G.A.; Hjelm, R.P.; Seeger, P.A.
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1995
Los Alamos National Lab., NM (United States). Funding organisation: USDOE, Washington, DC (United States)1995
AbstractAbstract
[en] 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 δ scatterers at different Q values for various instrument configurations needed to span a Q-range of 0.0007 - 0.44 angstrom -1
Primary Subject
Source
1995; 14 p; 13. International collaboration on advanced neutron sources; Villigen (Switzerland); 11-14 Oct 1995; CONF-9510212--4; CONTRACT W-7405-ENG-36; Also available from OSTI as DE96002592; NTIS; US Govt. Printing Office Dep
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Seeger, P.A.; Daemen, L.L.; Hjelm, R.P. Jr.
Los Alamos National Lab., Manuel Lujan Jr. Neutron Scattering Center, NM (United States). Funding organisation: USDOE Assistant Secretary for Management and Administration, Washington, DC (United States)1998
Los Alamos National Lab., Manuel Lujan Jr. Neutron Scattering Center, NM (United States). Funding organisation: USDOE Assistant Secretary for Management and Administration, Washington, DC (United States)1998
AbstractAbstract
[en] A code package consisting of the Monte Carlo Library MCLIB, the executing code MC RUN, the web application MC Web, and various ancillary codes is proposed as an open standard for simulation of neutron scattering instruments. The architecture of the package includes structures to define surfaces, regions, and optical elements contained in regions. A particle is defined by its vector position and velocity, its time of flight, its mass and charge, and a polarization vector. The MC RUN code handles neutron transport and bookkeeping, while the action on the neutron within any region is computed using algorithms that may be deterministic, probabilistic, or a combination. Complete versatility is possible because the existing library may be supplemented by any procedures a user is able to code. Some examples are shown
Secondary Subject
Source
1998; 11 p; International workshop on new opportunities for better user group software (NOBUGS '97); Argonne, IL (United States); 10-12 Dec 1997; CONF-971265--; CONTRACT W-7405-ENG-36; ALSO AVAILABLE FROM OSTI AS DE99000642; NTIS; US GOVT. PRINTING OFFICE DEP
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