Full-pattern analysis of time-of-flight neutron transmission of mosaic crystals

Abstract

The energy-resolved neutron transmission of mosaic crystals contains a series of dips in intensity, at specific neutron wavelengths defined by the orientation of the specimen in the neutron beam. This article presents a Rietveld type fullpattern analysis of neutron transmission experiments on mosaic crystals performed at spallation pulsed neutron sources. The proposed analysis provides precise and simple determination of lattice parameters, mosaicity, extinction factors and crystal orientation, and is especially suited to investigate the spatial variation of such microstructural information across macroscopic specimens with $1 mm resolution. The effect of extinction on the intensity of Bragg reflections has been successfully accounted for by a parameter measuring the ratio of the beam attenuation due to Bragg reflection to the combined attenuation due to absorption and scattering processes. Experiments were performed at the ENGIN-X beamline, ISIS Facility, UK, on several naturally occurring and man-made mosaic crystals, including a copper monochromator at temperatures between 55 and 300 K, an iron-nickel meteorite, and a natural pyrite crystal. Typical experimental resolutions found for lattice parameters and mosaicity are 0.03 and 7%, respectively. The possibilities of the technique for quantitative phase and/or texture analysis of specimens composed of several grains or phases are discussed.

Deriving Quantitative Crystallographic Information from the Wavelength-Resolved Neutron Transmission Analysis Performed in Imaging Mode

“…Although detailed crystallographic characterization of a single-crystal material can be performed by whole pattern fitting analysis toward Bragg-dip transmission spectrum [29,30], the author considered that the Bragg-dip neutron transmission method also becomes a useful method for grain orientation imaging as well as neutron diffraction imaging techniques [31,32]. Since a fast determination method of the number of grains and their crystal orientations from a Bragg-dip pattern is developed for this aim, the data analysis procedure is briefly presented in this section; the details are reported in [28].…”

Non-contact measurement of partial gas pressure and distribution of elemental composition using energy-resolved neutron imaging

“…4,[7][8][9][10][11][12][13][14] The energy resolved neutron imaging reported in this paper covers a broad range of neutron energies, including the thermal and cold neutrons. Therefore not only elemental mapping can be performed from the data acquired in such experiments, but also some microstructure parameters can be reconstructed at the same time, as demonstrated by all the previous thermal neutron transmission studies.…”

“…Whereas the technique is frequently performed with a white spectrum using a thermal or cold neutron beam [1][2][3] the characterization options are greatly expanded by energy-resolved imaging [4][5][6] in which transmission spectra are measured for each pixel of the image. This allows spatially-resolved imaging of features related to microstructure variation such as texture and mosaicity, [7][8][9][10] residual strain 7,[10][11][12][13] and phase distributions, 14 when thermal and cold neutrons are used. Studies that employ resonances appearing in the epithermal range of energies have been also reported for the investigation of elemental composition [15][16][17][18][19][20][21] and remote measurement of temperature.…”

Inverse pole figure mapping of bulk crystalline grains in a polycrystalline steel plate by pulsed neutron Bragg-dip transmission imaging

“…crystal-lattice parameters, crystal orientation, crystal mosaicity, strain etc.) by Malamud & Santisteban (2016). However, the determination of the orientation of a single crystallite in a material containing overlapping grains is quite difficult for least-squares Bragg-dip pattern fitting/refinement without a rough initial estimation of the crystallographic parameters of each single crystal included in the neutron transmission path.…”

“…The large field of view ($10 Â 10 cm) with a spatial resolution of a few hundred micrometres is one of the features of neutron transmission imaging. Secondly, crystal orientation analysis using a neutron transmission method (such as pulsed neutron Bragg-dip transmission spectroscopy, which is usually applied to single-crystaltype materials; Santisteban, 2005;Kockelmann et al, 2007;Malamud & Santisteban, 2016) is convenient because the neutron wavelengths of Bragg dips can reflect the crystal orientation of the single crystal. This is because the Bragg dip appears at the neutron wavelength = 2d sin , where d is the crystal-lattice plane spacing and is the Bragg angle.…”