High-Resolution Analysis Using Bent Perfect Crystal in Powder Diffraction: Part II

Abstract

As a continuation of our recent studies of α-Fe(211) samples at a scattering angle of 2θS = 88° (Part I), a three-axis setup using bent perfect crystal monochromator and several analyzers was tested in the diffraction study of polycrystalline α-Fe(110) pins with a diameter of 8 and 2 mm at a scattering angle of 2θS = 47.1°. After realizing the focusing conditions in real and momentum space at a neutron wavelength of 0.162 nm, a high angular resolution was achieved up to FWHM(Δd/d) = 1.4 × 10–3 and FWHM(Δd/d) = 2.5 × 10–3 for α-Fe samples with a diameter of 2 and 8 mm, respectively. This resolution was obtained by using open beams, i.e., without Soller collimators within the used range of the curvatures of the analyzers. Such settings can be used in powder diffraction, namely, in studies of high-resolution residual stresses and/or analysis of diffraction profiles with a small difference in the lattice parameters or a small change due to the application of an external load.