Using pulsed neutron transmission for crystalline phase imaging and analysis

Abstract

The total scattering cross section of polycrystalline materials in the thermal neutron region contains valuable information about the scattering processes that neutrons undergo as they pass through the sample. In particular, it displays characteristic discontinuities or Bragg edges of selected families of lattice planes. We have developed a pixelated time-of-flight transmission detector able to record these features and in this paper we examine the potential for quantitative phase analysis and crystalline phase imaging through the examination of a simple two-phase test object. Two strategies for evaluation of the absolute phase volumes (path lengths) are examined. The first approach is based on the evaluation of the Bragg edge amplitude using basic profile information. The second approach focuses on the information content of certain regions of the spectrum using a Rietveld-type fit after first identifying the phases via the characteristic edges. The phase distribution is determined and the coarse chemical species radiographic image reconstructed. The accuracy of this method is assessed.