Powder diffraction in Bragg-Brentano geometry with straight linear detectors

TL;DR

This paper investigates how straight linear detectors affect resolution in powder diffraction within Bragg-Brentano geometry and proposes an adaptive channel selection algorithm to improve resolution without sacrificing speed.

Contribution

It introduces an adaptive algorithm for channel selection in linear detectors that enhances resolution at low angles in powder diffraction measurements.

Findings

Improved resolution function across all angles using the adaptive algorithm.

Maintained fast data collection by using the full detector at higher angles.

Reduced resolution degradation caused by geometrical defocusing.

Abstract

A common way of speeding up powder diffraction measurements is the use of one or two dimensional detectors. This usually goes along with worse resolution and asymmetric peak profiles. In this work the influence of a straight linear detector on the resolution function in the Bragg-Brentano focusing geometry is discussed. Due to the straight nature of most modern detectors geometrical defocusing occurs which heavily influences the line shape of diffraction lines at low angles. An easy approach to limit the resolution degrading effects is presented. The presented algorithm selects an adaptive range of channels of the linear detector at low angles, resulting in increased resolution. At higher angles still the whole linear detector is used and the data collection remains fast. Using this algorithm a well-behaved resolution function is obtained in the full angular range, whereas using the full linear detector the resolution function varies within one pattern which hinders line shape and Rietveld analysis.