Paradoxically, although fossils are mostly mineralized materials only the latter is commonly used to infer their mineral composition, but X-ray diffraction, which specifically provides phase identification, received little attention.
Xpad cooler series#
Nowadays, efforts are largely driven by taphonomic studies, especially those investigating the exceptional preservation of organic molecules or soft tissues, leading to a series of developments towards molecular and elemental imaging. Paleontologists have always tested, used and developed cutting edge imaging techniques to produce the most complete and accurate descriptions of their fossils. We also illustrate that mineralogical contrasts between fossil tissues and/or the encasing sedimentary matrix can be used to visualize hidden anatomies in fossils. Similarly, this approach could potentially provide new knowledge on other (bio)mineralization processes in environmental sciences. Probing such crystallographic information is instrumental in defining mineralization sequences, reconstructing the fossilization environment and constraining preservation biases. It identifies and maps mineral phases and their distribution at the microscale over centimetre-sized areas, benefitting from the elemental information collected synchronously, and further informs on texture (preferential orientation), crystallite size and local strain. This innovative approach was applied to millimetre-thick cross-sections prepared through three-dimensionally preserved fossils, as well as to compressed fossils. Here, we show the use of synchrotron radiation to generate not only X-ray fluorescence elemental maps of a fossil, but also mineralogical maps in transmission geometry using a two-dimensional area detector placed behind the fossil. However, the mineral composition of fossils, particularly where soft tissues are preserved, is often only inferred indirectly from elemental data, while X-ray diffraction that specifically provides phase identification received little attention. Accessing their chemical composition provides unique insight into their past biology and/or the mechanisms by which they preserve, leading to a series of developments in chemical and elemental imaging. The performance of the device was characterize by carrying out several high speed imaging experiments using the PIXSCAN II irradiation setup described in the last chapter of this thesis.įossils, including those that occasionally preserve decay-prone soft tissues, are mostly made of minerals. The camera achieves a readout speed of 240 images/s, with maximum number of images limited by the RAM memory of the acquisition PC. The readout architecture of the camera is based on the PCI Express interface and on programmable FPGA chips. The XPAD3 camera is a large surface X-ray detector composed of eight detection modules of seven XPAD3-S chips each with a high-speed data acquisition system.
Two of them are being operated at the beamline of the ESRF and SOLEIL synchrotron facilities and the third one is embedded in the PIXSCAN II irradiation setup of CPPM. Within a collaboration between CPPM, ESRF and SOLEIL, three XPAD3 cameras were built. In this thesis, high frame rate X-ray imaging based on the XPAD3-S photons counting chip is presented. As a matter of fact the hybrid pixel technology meets the requirements of these two research fields, particularly by providing energy selection and low dose imaging capabilities. The aim of the project, of which the work described in this thesis is part, was to design a high-speed X-ray camera using hybrid pixels applied to biomedical imaging and for material science.
0 kommentar(er)
