8 Matching Results

Search Results

Advanced search parameters have been applied.
in creator/contributor: "Hjelm, R.P. Jr."  
Results: 1 - 8
open access

Solutions for implementing time-of-flight techniques in low-angle neutron scattering, as realized on the Low-Q Diffractometer at Los Alamos

Description: 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 Ala… more
Date: December 1, 1992
Creator: Hjelm, R. P. Jr. & Seeger, P. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Molecular composites from liquid crystalline polymers and liquid crystalline thermosets

Description: We propose a new approach to molecular composites. This approach uses a mixture of a liquid crystalline polymer and a liquid crystalline thermoset to enhance the miscibility. Preliminary neutron scattering data is presented on a system of short and long rod aromatic amides. The data is interpreted using the interpenetrating phase model of Debye and Bueche. The analysis indicates that the scattering is consistent with this model and shows a characteristic length scale in the range of 70 to 80 A.… more
Date: July 1, 1993
Creator: Benicewicz, B. C.; Douglas, E. P. & Hjelm, R. P. Jr.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Small-angle scattering, contrast variation and the study of complex composite materials: A study of the structure of carbon black

Description: Detailed studies are presented on the structure and aggregation of an experimental high surface area carbon black (HSA) using small-angle neutron scattering and the method of contrast variation. We find that the approximately 27 mn HSA particle form small, linear aggregates of average aggregation number 5 when suspended in cyclohexane. There is considerable density fluctuation in the interior of these particles, with the denser regions being toward the outer part of the spherically-averaged str… more
Date: May 1, 1993
Creator: Hjelm, R. P. Jr.; Seeger, P. A. & Wampler, W. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

The microstructure and morphology of carbon black: A study using small angle neutron scattering and contrast variation

Description: This is a study of the microstructure of particles of an experimental high surface area carbon black (HSA) and of the morphology of the particle aggregates using small-angle neutron scattering and the method of contrast variation. Contrast variation was effected by studying suspensions of the carbon black in cyclohexane containing different fractions of deuterocyclohexane. We find that the approximately 29 nm diameter HSA particles are arranged as small, linear aggregates with average aggregati… more
Date: April 1, 1994
Creator: Hjelm, R. P. Jr.; Seeger, P. A.; Wampler, W. A. & Gerspacher, M.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Comparison of SANS instruments at reactors and pulsed sources

Description: Small angle neutron scattering is a general purpose technique to study long range fluctuations and hence has been applied in almost every field of science for material characterization. SANS instruments can be built at steady state reactors and at the pulsed neutron sources where time-of-flight (TOF) techniques are used. The steady state instruments usually give data over small q ranges and in order to cover a large q range these instruments have to be reconfigured several times and SANS measur… more
Date: September 1, 1992
Creator: Thiyagarajan, P.; Epperson, J. E.; Crawford, R. K.; Carpenter, J. M. & Hjelm, R. P. Jr.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Monte Carlo simulation of neutron scattering instruments

Description: 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 h… more
Date: December 1998
Creator: Seeger, P. A.; Daemen, L. L. & Hjelm, R. P., Jr.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

The neutron instrument Monte Carlo library MCLIB: Recent developments

Description: A brief review is given of the developments since the ICANS-XIII meeting made in the neutron instrument design codes using the Monte Carlo library MCLIB. Much of the effort has been to assure that the library and the executing code MC{_}RUN connect efficiently with the World Wide Web application MC-WEB as part of the Los Alamos Neutron Instrument Simulation Package (NISP). Since one of the most important features of MCLIB is its open structure and capability to incorporate any possible neutron … more
Date: June 1998
Creator: Seeger, P. A.; Daemen, L. L.; Hjelm, R. P., Jr. & Thelliez, T. G.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen