A compact-rigid multi-analyser for energy and angle filtering of high-resolution X-ray experiments. Part 1. Principles and implementation

Abstract

Diffraction and spectroscopy instruments using a filtering process with several analyser crystals have existed for about 30 years at synchrotron radiation sources, but they are difficult to use on laboratory sources. Several diffraction multi-filtering systems for powder diffraction experiments have been studied and optimized, in order to show the relevance, simplicity and efficiency of their implementation. Optical filter systems containing one or many diffracting elements, precisely positioned in a rigid manner on a logarithmic spiral surface and having a stability that allows high resolution and high sensitivity to powder diffraction experiments, have been developed. After having tested prototypes with various geometries, we present in particular the realization of a small rigid-compact multi-analyser comb that allows 20–50 measurements on synchrotron radiation sources to be filtered in parallel, but also and especially that can be adapted on laboratory X-ray sources (Ag Kα1) to increase by an order of magnitude the intensities and resolutions of the measurements. Such a rigid-compact multi-analyser block can advantageously be associated with `photon-counting' 1D and 2D detectors in order to drastically improve the detection thresholds of powder diffraction measurements to better than 0.1%, which allows the detection/quantification/analysis of minor phases in studies of `real' complex materials.

A compact-rigid multi-analyser for energy and angle filtering of high-resolution X-ray experiments. Part 2. Efficiency of a single-crystal-comb

“…As the number of beams analysed is proportional to the crystal density of such a rigid system, it is important to have a relatively small angular pitch between them. The lower limit of this pitch is given by the manufacturing precision of the system: (i) a simple sandwich-comb of crystals, easily made by 3D printing, allows a pitch of 0.2 to be reached but not a pitch of 0.1 , (ii) a single-crystal-comb block having a rigid LogSpiral curvature, more difficult to build, enables a pitch of 0.1 to be achieved, as it offers higher precision and regularity of the orientations of each single-crystal plate of the block (Prat & Hodeau, 2023).…”

“…The characteristics of such a LogSpiral curve are that any analyser crystal located on it always sees its source/sample at the same Bragg angle  A , as shown for Si(111) analyser crystals in Fig. 1 and in Part 1 of this contribution (Prat & Hodeau, 2023;hereafter 'Part 1'). So it would be best to build a rigid MAD system where, for a different set of experiments, the only parameters that can vary are the analyser angle  A and the detector angle 2 A .…”