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- 2016 (15) (entfernen)
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Eingeladener Vortrag
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An automatic sample changer chamber for total reflection X-ray fluorescence (TXRF) and X-ray absorption near-edge structure (XANES) analysis in TXRF geometry was successfully set up at the BAMline at BESSY II. TXRF and TXRF-XANES are valuable tools for elemental determination and speciation, especially where sample amounts are limited (<1 mg) and concentrations are low (ng ml⁻¹ to μg ml⁻¹). TXRF requires a well defined geometry regarding the reflecting surface of a sample carrier and the synchrotron beam. The newly installed chamber allows for reliable sample positioning, remote sample changing and evacuation of the fluorescence beam path. The chamber was successfully used showing accurate determination of elemental amounts in the certified reference material NISTwater 1640. Low limits of detection of less than 100 fg absolute (10 pg ml⁻¹) for Ni were found. TXRF-XANES on different Re species was applied. An unknown species of Re was found to be Re in the +7 oxidation state.
Die naturwissenschaftliche Analyse historischer Materialen ermöglicht die Beantwortung kulturhistorischer Fragestellungen, die mit kunsthistorischen oder archäologischen Ansätzen allein nicht zu leisten sind. In dieser Studie wurden sechs römische Münzen mit unterschiedlich stark ausgeprägten Korrosionsschichten an unbehandelten und polierten Stellen mit vier zerstörungsfreien analytischen Methoden untersucht: Hoch- und Niederenergie Protonen Induzierter Röntgenemission (HE-/PIXE), Synchrotronstrahlungsinduzierte-Röntgenfluoreszenzanalyse (SY-RFA) und Mikro-Röntgenfluoreszenzanalyse (Mikro-RFA) mit einem mobilen Gerät. Aufgrund von Unterschieden in den Messbedingungen und dem Einfluss der Patina-Schichten auf diese ergaben sich nur für wenige Elemente Übereinstimmungen in den quantitativen Daten. Zur Validierung zukünftiger Messkampagnen mit verschiedenen Methoden sind daher Vergleichstudien unerlässlich.
High Speed, High Resolution imaging spectrometers based on pnCCDs for XRF and XRD applications
(2016)
For many years pnCCDs have been well known as X-ray detectors for spectroscopic imaging in many fields of science: X-Ray Fluorescence analysis (XRF), X-ray Diffraction (XRD) with light sources in large accelerator facilities as well as with laboratory light sources or with X-rays from celestial sources in X-ray astronomy. A brief introduction in GEXRF (Grazing Emission XRF) measurements with a laboratory laser produced plasma source will be given, PIXE (Particle Induced X-ray Emission) measurements and D2XRF (Double Dispersive X-Ray Fluorescence) and Slicing experiments with pnCCDs coupled to polycapillary optics performed at the BESSY synchrotron will be shown. Energy-dispersive Laue diffraction with ultra-hard X-rays for the analysis of defects in metals will conclude the overview of spectroscopic X-ray imaging measurements in the field of structure and dynamics of matter.
The newly developed EXAFS set-up comprises both time- and spatially-resolved EXAFS information simultaneously in a single-shot. This facile, stable and scanningless set-up was tested at the BAMline @ BESSY-II (Berlin, Germany). The primary broadband beam is generated by a filter/X-ray-mirror combination (bandpass). The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by an area sensitive detector based on a CCD camera, in a theta - 2 theta geometry.
The first in situ measurements were successfully carried out and hereby presented. The case-study involved a well known reaction, in which structural changes are induced over time, and continuously measured. We were able to track structural changes within a 1s time resolution.
Gold mosaics, made from gold and glass, are one of the best expressions of Late Antique Byzantine and Early Islamic art. The gold alloys, whose composition seems to indicate that gold coins were re-used to fabricate the tesserae, can be used to provide information on the mosaics chronology. Monetary Byzantine gold is in fact characterized by the presence of Pt, which contents in the gold alloy change over time, but Pt must be measured in 0.2-0.4 µm thickness gold leaves that were beaten to be sandwiched between two glass layers.
To analyze this samples the D²XRF set-up at the BAMline at the BESSY synchrotron in Berlin was used. The combination of a crystal for wavelength dispersion and an energy resolving single photon counting pnCCD allows the realization of this very simple wavelength dispersive detection system. With this system an MDL of 1 μg/g for the determination of Pt in Au under optimal conditions can be reached.
Gold leaf tesserae from nine archaeological sites, covering the period that goes from the 5th c. to the 8th c., were analyzed. The presence of Pt in the majority of the samples confirmed the re-use of coins. The Pt contents separate the samples in three groups, one of which having the same chemical characteristics as the Byzantine gold could be compared to dated coins for chronology. The higher Pt contents for one of other groups suggest
Gold ist eines der sieben schon im Altertum bekannten Metalle und wurde wg. seines Glanzes und seiner Seltenheit von alters her als Tauschmittel und zur Herstellung von Schmuck benutzt. Außerdem ist es einfach bearbeitbar und weitestgehend gegen chemische Einflüsse resistent.
Die Untersuchungen von Gold mit synchrotronstrahlungsangeregter Röntgenfluoreszenzanalyse sind zerstörungsfrei und geben Auskunft über die in der untersuchten Probe vorhandenen chemischen Elemente.
Bei den hier vorgestellten Untersuchungen an der BAMline stehen Fragestellungen wie Herkunft, Herstellungsverfahren und Zusammengehörigkeit von Goldfunden im Vordergrund. Die verschiedenen Fragestellungen werden an einer Reihe von Beispielen erläutert die vom Wikingerschatz aus Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten langen. Zusätzlich werden die modernen Messmethoden vorgestellt, die am Synchrotron heutzutage zur Verfügung stehen.
Gold ist eines der sieben schon im Altertum bekannten Metalle und wurde wg. seines Glanzes und seiner Seltenheit von alters her als Tauschmittel und zur Herstellung von Schmuck benutzt. Außerdem ist es einfach bearbeitbar und weitestgehend gegen chemische Einflüsse resistent.
Die Untersuchungen von Gold mit synchrotronstrahlungsangeregter Röntgenfluoreszenzanalyse sind zerstörungsfrei und geben Auskunft über die in der untersuchten Probe vorhandenen chemischen Elemente.
Bei den hier vorgestellten Untersuchungen an der BAMline stehen Fragestellungen wie Herkunft, Herstellungsverfahren und Zusammengehörigkeit von Goldfunden im Vordergrund. Die verschiedenen Fragestellungen werden an einer Reihe von Beispielen erläutert die vom Wikingerschatz aus Hiddensee über die Himmelsscheibe von Nebra bis hin zu Funden aus Ägypten langen. Zusätzlich werden die modernen Messmethoden vorgestellt, die am Synchrotron heutzutage zur Verfügung stehen.
The Color X-ray Camera CXC or SLcam® is an energy-resolving X-ray camera capable of energy- and space-resolved measurements. It consists of a high-speed CCD detector coupled to a polycapil-lary optic that conducts the X-ray photons from the probe to distinct pixels onto the detector.
The camera is capable of fast acquisition of spatially and energy resolved fluorescence images. A 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 elements distribution in a sample. It was developed in a joint project with BAM, IFG Berlin and PN Sensors.
In this contribution we will mainly discuss the use of the CXC at our beamline, the BAMline at BESSY II and imaging applications of the CXC from different areas, like biology and archaeometry. Additionally new developments for the use of the detector without optics, like wavelength dispersive detection or 1shot-XANES, will be presented.
Fire-gilding or amalgam gilding is a historical technique for the gilding of objects. The object to be gilded is coated with an amalgam (a solution of gold (Au) in mercury (Hg)). By heating, the largest part of the Hg is subsequently evaporated and there remains a gold layer, containing still detectable amounts of Hg.
The information on the used gilding technique might be crucial for the conservation and preservation of archaeological objects. Therefore, the main objective of this work is the detailed understanding of the behaviour of Hg under conditions of fire gilding. I.e. the understanding of the diffusion and evaporating behaviour of Hg, depending on parameters like substrate material (silver, copper, bronze, brass...), heating temperature and duration, and the resulting Hg depth profiles under these conditions. Secondary objective is the establishment of a measurement protocol for the unambiguous identification of different types of gilding, based solely on non-destructive methods, which can be applied to historical samples.
In a first step, fire-gilded samples have been prepared on Cu and Ag sheet metal, respectively. Some of the gildings were produced by a professional goldsmith; another set of samples was produced under laboratory conditions. These samples have been examined with NAA (neutron activation analysis) and SR-XRF (synchrotron radiation induced X-ray fluorescence). First results of these measurements will be presented and discussed.
A new concept that comprises both time- and lateral-resolved X-ray absorption fine-structure information simultaneously in a single shot is presented. This uncomplicated set-up was tested at the BAMline at BESSY-II (Berlin, Germany). The primary broadband beam was generated by a double multilayer monochromator. The transmitted beam through the sample is diffracted by a convexly bent Si (111) crystal, producing a divergent beam. This, in turn, is collected by either an energy-sensitive area detector, the so-called color X-ray camera, or by an area-sensitive detector based on a CCD camera, in θ-2θ geometry. The first tests were performed with thin metal foils and some iron oxide mixtures. A time resolution of lower than 1 s together with a spatial resolution in one dimension of at least 50 µm is achieved.