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Register a new userWarren-Averbach line broadening analysis from a time of flight neutron diffractometer
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The well known Warren-Averbach theory of diffraction line profile broadening is shown to be applicable to time of flight data obtained from a neutron spallation source. Without modification, the method is applied to two very different examples; a cold worked ferritic steel and a thermally stressed alumina-30% SiC composite. Values of root mean square strains averaged over a range of lengths for the ferritic steel were used to estimate dislocation densities; values were found to be in good agreement with geometrically necessary dislocation densities independently measured from similarly orientated grains measured from electron backscatter diffraction analysis. An analytical model for the ceramic is described to validate the estimate of root mean square strain.
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NeXus is an international standard data format intended to reduce the need for redundant software development efforts in the neutron and x-ray scattering communities. As the NeXus standard matures it is starting to be used at laboratories for storing raw data. The Manuel Lujan Jr. Neutron Scattering Center (MLNSC) at Los Alamos National Laboratory and the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory have been working with NeXus in an effort to share data and software. MLNSC is now writing files compliant with NeXus and the Integrated Spectral Analysis Workbench (ISAW) software from IPNS is being used with this data. Problems can arise if the standard is interpreted in different ways and information that belongs in the file is not accounted for in the standard. This paper will discuss an inter-laboratory collaboration in relation to a maturing data standard.
This article introduces software called Phonon Explorer that implements a data mining workflow for large datasets of the neutron scattering function, S(Q, {omega}), measured on time-of-flight neutron spectrometers. This systematic approach takes advantage of all useful data contained in the dataset. It includes finding Brillouin zones where specific phonons have the highest scattering intensity, background subtraction, combining statistics in multiple Brillouin zones, and separating closely spaced phonon peaks. Using the software reduces the time needed to determine phonon dispersions, linewidths, and eigenvectors by more than an order of magnitude.
The first neutron texture diffractometer in China has been built at China Advanced Research Reactor due to the strong demands of texture measurement with neutrons from domestic user community. This neutron texture diffractometer has high neutron intensity, moderate resolution and is mainly applied to study the texture in the commonly used industrial materials and engineering components. In this paper, the design and characteristics of this instrument are described. The results for calibration with neutrons and quantitative texture analysis of Zr alloy plate are presented. The comparison of texture measurement among different neutron texture diffractometer of HIPPO at LANSCE, Kowari at ANSTO and neutron texture diffractometer at CARR illustrates the reliable performance of this texture diffractometer.
An instrument and software algorithm is described for the purpose of characterization of large single crystals at the Alignment Facility (ALF) of the ISIS spallation neutron source. We describe a method for both characterizing the quality of the sample and also aligning it in a particular scattering plane. We present a software package written for this instrument and demonstrate its utility by way of an example of the structural characterization of large singles crystals of Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$. We suggest extensions and modifications of characterization instruments for future improved beamlines. It is hoped that this software will be used by the neutron user community for pre characterizing large single crystals for spectroscopy experiments and that future facilities will include such a facility as part of the spectroscopy suite at spallation neutron sources.
We report the results of inelastic neutron scattering investigation on the model antiferromagnet CoF$_2$ by time-of-flight neutron spectroscopy. We measured the details of the scattering function $S(Q,omega)$ as a function of temperature with two different incident neutron wavelengths. The temperature and Q dependence of the measured scattering function suggests the presence of magnon-phonon coupling in almost all branches. The present results are in agreement with the strong magnetoelastic effects observed previously.
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