A diffraction effect in X-ray area detectors

TL;DR

This paper investigates a diffraction pattern caused by Bragg reflection in X-ray area detectors, affecting image quality but also offering potential for calibration and alignment purposes.

Contribution

It provides the first detailed analysis of the diffraction pattern in crystalline X-ray detectors and demonstrates its practical applications in calibration and alignment.

Findings

Diffraction pattern intensity up to 20% affects image analysis.

Pattern can be used for detector alignment and energy calibration.

Experimental results cover photon energies from 3.4 keV to 10 keV.

Abstract

When an X-ray area detector based on a single crystalline material, for instance, a state of the art hybrid pixel detector, is illuminated from a point source by monochromatic radiation, a pattern of lines appears which overlays the detected image. These lines can be easily found by scattering experiments with smooth patterns, such as small-angle X-ray scattering. The origin of this effect is the Bragg reflection in the sensor layer of the detector. Experimental images are presented over a photon energy range from 3.4 keV to 10 keV, together with a theoretical analysis. The intensity of this pattern is up to 20%, which can disturb the evaluation of scattering and diffraction experiments. The patterns can be exploited to check the alignment of the detector surface with the direct beam, and the alignment of individual detector modules with each other in the case of modular detectors, as well as for the energy calibration of the radiation.