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Polycapillary halflenses are widely used to focus X-ray radiation onto a small spot. Additionally they can reduce the field of view of a semiconductor detector when placed in front of one. In 3D micro X-ray fluorescence spectroscopy (3D Micro-XRF) with synchrotron radiation, two polycapillary halflenses are used in a confocal geometry. Up until now, characterization measurements in the focal plane have only been performed in the case of the lens focusing parallel radiation. Assumptions have been made, that in the other case, when isotropic radiation from a spot source is transported to a detector, the acceptance distribution in the focal plane is also Gaussian. We performed measurements with an electron beam as well as a proton beam which confirm this assumption. In addition, a comparison between measurements in collecting and focusing mode show differences in spot size and transmission. These differences exemplify the fact that there is not one global spot size or transmission function of a polycapillary halflens. Illumination and divergence effects can alter both characteristic lens parameters.
3D Micro X-ray fluorescence analysis was used for the investigation of reverse-glass paintings. The material-specific combination used in reverse-glass paintings leads to damage phenomena reinforced by glass corrosion. To elucidate the mechanism of corrosion processes taking place in the glass object depth profiles of mobile elements are of interest. In order to obtain elemental depth profiles of such kind of fragile objects the method of choice should be non-destructive. Our first results demonstrate the usefulness of the 3D Micro-XRF measurements for this kind of investigations. The assumption that certain binding media may initiate corrosion processes beginning at the interface glass/binding material could be confirmed.
The Dead Sea Scrolls belong to the most important cultural assets of mankind. Their long term preservation and study is a challenge that demands an interdisciplinary approach. As early as the 1950s natural scientists assisted the scholars in studying the scrolls. It was at this time that the first extensive study of the scroll material took place. It was found that most fragments were written not on leather but on parchment. In addition, a method for determining the age of the parchment was developed which is still of value today. In the 1990s the AMS-C14 method confirmed the palaeographic determination of the age of the manuscripts. The use of carbon ink throughout the scrolls is also consistent with the known scribal practices of that time. There are, however, manuscripts, and among them the famous Genesis Apocryphon Scroll, which exhibit ink corrosion, normally associated with iron-gall inks.
Today, 60 years after their discovery, a community of scientists from the Jewish National and University Library (JNUL), the Technical University of Berlin (TU Berlin), the Federal Institute for Materials Research and Testing (BAM) and Fritz-Haber-Institute of the MPG (FHI) set out to scientifically investigate the finds of Qumran using the most modern methods. The results of the study will be used to determine the provenance of the texts as well as to contribute to their long-term preservation. A considerable part of the non-destructive investigation is taking place in the Berlin State Library and at the Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung , BESSY II.
Preliminary investigations, performed at the BAM on some fragments, were used to evaluate the extent to which X-ray analytical methods can provide information regarding the geographical origin of the fragments and match the individual pieces. The interpretation of the measurement results is made more difficult by age and storage of the objects. It is believed that ageing processes as well as conservation methods have altered the samples in addition to the changes caused by environmental influences.
In collaboration with the TU Berlin, the samples from the parchments found in the caves near Qumran were tested by means of three-dimensional synchrotron based X-ray fluorescence analysis (3D-SyXRF). The aim of this non-destructive investigation was the identification of the inorganic material used in the manufacture of the parchments.
The XRF experiments are supported by the non-destructive analysis by means of synchrotron based infrared spectroscopy (SyFTIR) in collaboration with BESSY II as well as optical and electron microscopy in collaboration with Fritz-Haber-Institute (FHI).
A sealable ultrathin window sample cell for the study of liquids by means of soft X-ray spectroscopy
(2017)
A new sample cell concept for the analysis of liquids or solid-liquid interfaces using soft X-ray spectroscopy is presented, which enables the complete sealing of the cell as well as the Transport into vacuum via, for example, a load-lock system. The cell uses pressure monitoring and active as well as passive pressure regulation systems, thereby facilitating the full control over the pressure during filling, sealing, evacuation, and measurement. The cell design and sample preparation as well as the crucial sealing procedure are explained in detail. As a first proof-of-principle experiment, successful nitrogen K-edge fluorescence yield near-edge X-ray absorption fine structure experiments of a biomolecular solution are presented. For this purpose, it is shown that the careful evaluation of all involved parameters, such as window type or photon flux, is desirable for optimizing the experimental result.
A new approach for chemical speciation in stratified systems using 3D Micro-XAFS spectroscopy is developed by combining 3D Micro X-ray Fluorescence Spectroscopy (3D Micro-XRF) and conventional X-ray Absorption Fine Structure Spectroscopy (XAFS). A prominent field of application is stratified materials within which depth-resolved chemical speciation is required. Measurements are collected in fluorescence mode which in general lead to distorted spectra due to absorption effects. Developing a reliable reconstruction algorithm for obtaining undistorted spectra for superficial and in-depth layers is proposed and validated. The developed algorithm calculates the attenuation coefficients of the analyte for the successive layers facilitating a new spectroscopic tool for three-dimensionally resolved nondestructive chemical speciation.
A combination of 3D micro X-ray fluorescence spectroscopy (3D micro-XRF) and micro-XRF was utilized for the investigation of a small collection of highly heterogeneous, partly degraded Dead Sea Scroll parchment samples from known excavation sites. The quantitative combination of the two techniques proves to be suitable for the identification of reliable marker elements which may be used for classification and provenance studies. With 3D micro-XRF, the three-dimensional nature, i.e. the depth-resolved elemental composition as well as density variations, of the samples was investigated and bromine could be identified as a suitable marker element. It is shown through a comparison of quantitative and semiquantitative values for the bromine content derived using both techniques that, for elements which are homogeneously distributed in the sample matrix, quantification with micro-XRF using a one-layer model is feasible. Thus, the possibility for routine provenance studies using portable micro-XRF instrumentation on a vast amount of samples, even on site, is obtained through this work.
A new fundamental parameter based calibration procedure for micro X-ray fluorescence spectrometers
(2011)
Fundamental parameter based quantification of X-ray fluorescence (XRF) measurement data requires an accurate knowledge of the spectrometer parameters, including the spectral distribution of the excitation radiation. In case of micro-XRF where a polycapillary optic is utilized in the excitation channel this distribution is changed due to the transmission properties of the lens. A new calibration procedure, based on fluorescence data of thin standard samples, was developed to determine the excitation spectrum, i.e., the product of the X-ray tube spectrum and the transmission of the used X-ray optic of a micro-XRF setup. The calibration result was validated by the quantitative analyses of certified multi-element reference standards and shows uncertainties in the order of 2% for main components, 10% for minor elements and 25% for trace elements. The influence of secondary order effects like Coster–Kronig transitions and cascade effects is analyzed and the accuracy of fundamental parameters in common databases is discussed.