Neutron diffraction studies of a double-crystal (+n,-m) setting containing a fully asymmetric diffraction geometry (FAD) of a bent perfect crystal (BPC)

Abstract

In this paper, some results of neutron diffraction properties of the double-crystal Si(111) + Si(311) setting containing two bent perfect crystals, but with the second one – analyzer in the fully asymmetric diffraction geometry are presented. Both fully asymmetric diffraction geometries, with the output beam compression as well as the output beam expansion, were tested for the sake of possible applications.

Dispersive double bent crystal monochromators Si(111) + Si(311) and Si(111) + Si(400) with a strongly asymmetric diffraction geometry of the analyzer for powder diffractometry

“…First, DBC settings have been used in high or medium resolution SANS diffractometers with a variable resolution (Kulda and Mikula, 1983; Mikula et al ., 1988; Šaroun et al ., 1994; Hempel et al ., 1996). Recently, several experimental studies into properties of dispersive DBC settings have been carried out, with the goal of their possible employment in high resolution diffractometry (Mikula et al ., 2014, 2015; Mikula and Vrána, 2015). The tested DBC settings demonstrated the possibility of obtaining a high-resolution monochromatic beam with a very low collimation (2 Δ θ Μ) and Δ θ spread without using any Soller collimators.…”

Observation of multiple Bragg reflections accompanying forbidden Si(002) reflection in bent-perfect Si crystal

“…Even though the neutron sources provide currents several orders of magnitude lower than X-ray sources, there is a permanent attention paid to find the ways or methods and techniques helping in increasing the luminosity, and/or resolution of neutron scattering instruments. In addition to construction of high-flux neutron sources, a broad range of efficient neutron techniques, namely based on Bragg diffraction optics, have been recently developed (see, e.g., Yelon, 1994, 1995;Vogt et al, 1994;Mikula et al, 2008aMikula et al, , 2014cMikula and Vrána, 2015;Seong et al, 2010). This effort is strengthened not only by a necessity of investigations of samples of smaller dimensions but also by a necessity of using significantly better measurement resolution for investigation of finer effects, e.g., distinguishing and identifying powder diffraction lines corresponding to very close values of lattice spacings, for studies of plastic deformation by means of diffraction profile analysis and for studies of mosaic distribution of mosaic single crystals.…”

“…In this way, the so-called dispersive monochromators based on a dispersive double-diffraction process appear as candidates of monochromators for (very) high-resolution neutron diffractometers and spectrometers. It can be realized either by means of two independent crystals (Mikula et al, 2014a(Mikula et al, , 2014b(Mikula et al, , 2014cMikula and Vrána, 2015) or by means of strong multiple Bragg reflections (MBRs) realized inside one crystal (Mikula et al, 2006a(Mikula et al, , 2008a(Mikula et al, , 2011a(Mikula et al, , 2013. First, high-resolution MBR monochromators have been tested using neutron radiography for investigation of edge refraction effects (Mikula et al, 2008b(Mikula et al, , 2013.…”