Properties of the dispersive double bent crystal monochromator setting with a multicrystal sandwich at the place of the second axis

Abstract

In this paper, some luminosity, focusing and resolution properties of a double-crystal (n,-m) dispersive setting which contains a bent perfect Si(111) crystal as a first one and a sandwich consisting of four different bent perfect crystals (BPC) Si(220), Si(400), Ge(111) and Ge(311) located at the second axis, is introduced with the aim of possible use in high-resolution diffractometry. The properties were investigated at a neutron wavelength of 0.162 nm. It was shown that a narrow and highly collimated and high-resolution monochromatic beam can be obtained. By using a standard polycrystalline pin of α-Fe, the resolution of the three-axis diffraction performance, namely, in the vicinity of the scattering angle 2 θ S = 90 ∘ was tested in detail. It has been found that the dispersive double-crystal (DC) setting represents a high-resolution monochromator alternative, e.g. in powder diffraction which could be used at high-flux neutron sources.