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Register a new userPerformance of hybrid angle-energy dispersive X-ray diffraction and fluorescence portable system for non-invasive surface-mineral identification in Archaeometry
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Added by
Ariadna Mendoza Cuevas
Publication date
2016
fields
Physics
and research's language is
English
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Low power energy dispersive XRD-XRF portable instruments equipped with multiple angle scanning can take advantage of the shorter acquisition time of EDXRD with respect to ADXRD, and bring closer higher accuracy and resolution of inter-planar distance with those obtained by ADXRD. The data produced by this new hybrid configuration is correlated in the sense that a single XRF or XRD specimen appear in multiple spectra (the later shifted in energy for differing angles). Hence, for fully benefit from the richer data released by this configuration, the analysis should not be confined to the independent processing of the spectra, specialized hybrid data processing should be conceived. We previously reported some advances in the processing of the resulting 3D data (intensity, energy and angle). Here the analytical performance of the first hybrid angle-energy dispersive X-ray diffraction and fluorescence portable system is assessed for non-invasive surface mineral analysis of samples relevant for archaeometrical applications. We evaluate the performance on standard reference material and probe applicability of the methods so developed to identify stones (jadeite and omphacite), and pigments (Prussian blue) in the pictorial layer of modeled paintings. Discussion emphasize the improvement in accuracy of interplanar distance with respect to EDXRD taken at a single fixed angles, evaluate the resolution of AD/EDXRD data, and total acquisition time.
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Energy-dispersive X-ray diffraction (EDXRD) is extremely insensitive to sample morphology when implemented in a back-reflection geometry. The capabilities of this non-invasive technique for cultural heritage applications have been explored at high resolution at the Diamond Light Source synchrotron. The results of the XRD analysis of the pigments in 40 paints, commonly used by 20th century artists, are reported here. It was found that synthetic organic pigments yielded weak diffraction patterns at best, and it was not possible to unambiguously identify any of these pigments. In contrast, the majority of the paints containing inorganic pigments yielded good diffraction patterns amenable to crystallographic analysis. The high resolution of the technique enables the extraction of a range of detailed information: phase identification (including solid solutions), highly accurate unit cell parameters, phase quantification, crystallite size and strain parameters and preferred orientation parameters. The implications of these results for application to real paintings are discussed, along with the possibility to transfer the technique away from the synchrotron and into the laboratory and museum through the use of state-of-the-art microcalorimeter detectors. The results presented demonstrate the exciting potential of the technique for art history and authentication studies, based on the non-invasive acquisition of very high quality crystallographic data.
A vacuum-compatible photon-counting hybrid pixel detector has been installed in the ultra-high vacuum (UHV) reflectometer of the four-crystal monochromator (FCM) beamline of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY II in Berlin, Germany. The setup is based on the PILATUS3 100K module. The detector can be used in the entire photon energy range accessible at the beamline from 1.75 to 10 keV. Complementing the already installed vacuum-compatible PILATUS 1M detector used for small-angle scattering (SAXS) and grazing incidence SAXS (GISAXS), it is possible to access larger scattering angles. The water-cooled module is located on the goniometer arm and can be positioned from -90{deg} to 90{deg} with respect to the incoming beam at a distance of about 200 mm from the sample. To perform absolute scattering experiments the linearity, homogeneity and the angular dependence of the quantum efficiency, including their relative uncertainties, have been investigated. In addition, first results of the performance in wide-angle X-ray scattering (WAXS), X-ray diffraction (XRD) and X-ray reflectometry (XRR) are presented.
We present a strip transition-edge sensor microcalorimeter linear array detector developed for energy dispersive X-ray diffraction imaging and Compton scattering applications. The prototype detector is an array of 20 transition-edge-sensors with absorbers in strip geometry arranged in a linear array. We discuss the fabrication steps needed to develop this array including Mo/Cu bilayer, Au electroplating, and proof-of-principle fabrication of long strips of SiNx membranes. We demonstrate minimal unwanted effect of strip geometry on X-ray pulse response, and show linear relationship of 1/pulse height and pulse decay times with absorber length. For the absorber lengths studied, preliminary measurements show energy resolutions of 40 eV to 180 eV near 17 keV. Furthermore, we show that the heat flow to the cold bath is nearly independent of the absorber area and depends on the SiNx membrane geometry.
The color X-ray camera (SLcam) is a full-field single photon imager. As stand-alone camera, it is applicable for energy and space-resolved X-ray detection measurements. The exchangeable poly-capillary optics in front of a beryllium entrance window conducts X-ray photons from the probe to distinguished energy dispersive pixels on a pnCCD. The dedicated software enables the acquisition and the online processing of the spectral data for all 69696 pixels, leading to a real-time visualization of the element distribution in a sample. No scanning system is employed. A first elemental composition image of the sample is visible within minutes while statistics is improving in the course of time. Straight poly-capillary optics allows for 1:1 imaging with a space resolution of 50 um and no limited depth of sharpness, ideal to map uneven objects. Using conically shaped optics, a magnification of 6 times was achieved with a space resolution of 10 um. We present a measurement with a laboratory source showing the camera capability to perform fast full-field X-ray Fluorescence (FF-XRF) imaging with an easy, portable and modular setup.
An experiment measuring the 2S Lamb shift in muonic hydrogen mup is being performed at the Paul Scherrer Institute, Switzerland. It requires small and compact detectors for 1.9 keV x rays (2P-1S transition) with an energy resolution around 25% at 2 keV, a time resolution better than 100 ns, a large solid angle coverage, and insensitivity to a 5 T magnetic field. We have chosen Large Area Avalanche Photodiodes (LAAPDs) from Radiation Monitoring Devices as x-ray detectors, and they were used during the last data taking period in 2003. For x-ray spectroscopy applications, these LAAPDs have to be cooled in order to suppress the dark current noise, hence, a series of tests were performed to choose the optimal operation temperature. Specifically, the temperature dependence of gain, energy resolution, dark current, excess noise factor, and detector response linearity was studied. Finally, details of the LAAPDs application in the muonic hydrogen experiment as well as their response to alpha particles are presented.
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