Application of a pnCCD for energy-dispersive Laue diffraction with ultra-hard X-rays

Abstract

In this work the spectroscopic performance of a pnCCD detector in the ultra‐hard energy range between 40 and 140 keV is tested by means of an energy‐dispersive Laue diffraction experiment on a GaAs crystal. About 100 Bragg peaks were collected in a single‐shot exposure of the arbitrarily oriented sample to white synchrotron radiation provided by a wiggler at BESSY II and resolved in a large reciprocal‐space volume. The positions and energies of individual Laue spots could be determined with a spatial accuracy of less than one pixel and a relative energy resolution better than 1%. In this way the unit‐cell parameters of GaAs were extracted with an accuracy of 0.5%, allowing for a complete indexing of the recorded Laue pattern. Despite the low quantum efficiency of the pnCCD (below 7%), experimental structure factors could be obtained from the three‐dimensional data sets, taking into account photoelectric absorption as well as Compton scattering processes inside the detector. The agreement between measured and theoretical kinematical structure factors calculated from the known crystal structure is of the order of 10%. The results of this experiment demonstrate the potential of pnCCD detectors for applications in X‐ray structure analysis using the complete energy spectrum of synchrotron radiation.

Photonenenergie als dritte Dimension bei der Analyse der kristallographischen Textur

“…[7] Auch tiefenaufgelçste Messungen sind mit 3DXRD-Ansätzen wie Differential-Aperture X-ray Microscopy [1b] mçglich, jedoch muss hierbei zeitintensiv eine Blende durch den Strahl gerastert werden. Trotz seiner sehr geringen Grçße wurde er erfolgreich zur Bestimmung von Zwillingsbildung in Lysozymkristallen [10] ,d er Gitterverzerrung in Kupfer-Einkristallen [11] oder der Indizierung von GaAs-Einkristallen mit harten Rçntgenstrahlen verwendet, [12] wobei die Experimente nur einen kleinen Winkelausschnitt des reziproken Raums erforderten. Einige Ansätze wurden durch die Verwendung von energieauflçsenden Punktdetektoren bereits realisiert.…”

“…[8] Ein großer Fortschritt in dieser Hinsicht war die Entwicklung eines energieauflçsenden Flächendetektors (Rçntgenfarbkamera, pnCCD), [8,9] der im Prinzip energieauflçsende Laue-Beugung (EDLD) ermçglicht. Trotz seiner sehr geringen Grçße wurde er erfolgreich zur Bestimmung von Zwillingsbildung in Lysozymkristallen [10] ,d er Gitterverzerrung in Kupfer-Einkristallen [11] oder der Indizierung von GaAs-Einkristallen mit harten Rçntgenstrahlen verwendet, [12] wobei die Experimente nur einen kleinen Winkelausschnitt des reziproken Raums erforderten.…”

Photon Energy Becomes the Third Dimension in Crystallographic Texture Analysis

“…A technological leap forward was the development of an energy‐dispersive area detector (X‐ray color camera, pnCCD) which, in principle, allows energy‐dispersive Laue diffraction (EDLD). Despite it being a very small detector, it was successfully used, for example, for XRD of twinned lysozyme crystals, strain measurements in a Cu single crystal, and the indexing of a GaAs single crystal with hard X‐rays, where the experiment required only a small angular coverage of reciprocal space.…”

EDLD-Tool: A real-time GPU-based tool to stream and analyze energy-dispersive Laue diffraction of BIG Data sets collected by a pnCCD

“…Parallel processor technology and multi-core Graphic Processing Units (GPUs) have already been used for many applications in the field of detector technology, including real-time processing of pnCCD images [7][8][9]. Examples taken from singlecrystalline materials have demonstrated the reliability of this approach for in-situ visualization and data analysis [10][11][12]. Extension of the approach towards a compact tool which performs a fully automated data analysis and real-time visualization is challenging because of implementation complexities, memory issues and high latency execution time.…”