Collection of Bragg data with a neutron flat-cone diffractometer

Abstract

The design and operational principles are presented of a novel neutron diffractometer based on the flat-cone technique which uses a 400-cell one-dimensional multidetector. Setting angles and measuring conditions are given for a generalized flat-cone geometry. Test data were collected from an Ni(NH3)6(NO3) 2 crystal. They are compared with Bragg intensities measured from the same crystal with a conventional four-circle diffractometer. A test for consistency between the two data sets gives R values of 0.019 and 0-031 depending on the weighting scheme. The results of independent structure refinements are in good agreement.

Diffuse Scattering Investigations with a Graphite Double Monochromator for X-ray Synchrotron Radiation: YBa2Cu3O6.5 and KNbO3

“…To understand the anisotropic divergence of the graphite monochromator, we have to consider that the first graphite crystal increases the divergence whereas the second crystal restores it in a vertical direction. The divergence thus increases in a vertical direction only from 10 -5 to 3 × 10 -4 rad and in a horizontal direction to 3 × 10 -3 rad (Hohlwein et al, 1986).…”

“…In this case, a monochromator crystal with a sufficiently large mosaic spread is necessary to obtain a lower energy resolution AE/E of a few percent and therefore higher intensity, which is intermediate between unmonochromatized white radiation and the sharp resolution of perfect single-crystal monochromators. Such a monochromator, as described by Hohlwein et al (1986), consists of two pyrolytic graphite single crystals in a double-crystal monochromator, in parallel geometry, and produces a nearly parallel reflected beam with high intensity. The graphite monochromator gives an intensity gain of ~ 1998 International Union of Crystallography Printed in Great Britain -all rights reserved about 70 in comparison with silicon(1 l l) crystals in the same geometry.…”

Orientational disorder in ammonium chloride: elastic diffuse neutron scattering with a new technique

“…We used the flat-cone technique for the systematic collection of three-dimensional diffraction data with the one-dimensional multicounter (Hohlwein, Hoser & Prandl, 1986). The intensity distribution was measured in layers parallel to a (110) plane.…”

“…So we have to collect a complete set of diffuse scattering intensity in a reasonable time. We have solved this problem by combining the method of vertical energy analysis (Born & Hohlwein, 1989) with the fiat-cone technique (Hohlwein, Hoser & Prandl, 1986).…”

The upgraded cold neutron triple-axis spectrometer FLEXX – enhanced capabilities by new instrumental options

“…The Flat-Cone diffractometer E2 at HZB [10] has been recently upgraded with an array of position sensitive detectors which can be tilted out of the horizontal plane. This instrument allows to detect elastic scattering over a continuous Q-range without energy analysis.…”