NSLS-II Seminar

The ID21 beamline at the ESRF is dedicated to X-ray micro-spectroscopy. The scanning X-ray microscope has a tunable energy ranging from 2.1 to 7.2 keV and is optimized for very low background and low detection limit. It has been recently refurbished to give enhanced functionalities. As an example, the microscope can now host two different optical focusing configurations: either zone plates (ZP) or a Kirkpatrick-Baez mirror system (KB). A compact X-ray wavelength dispersive spectrometer achieving a few tens of eV energy resolution has also been implemented for highly selective fluorescence detection. A load-lock system allows fast exchange of samples under vacuum, and greatly facilitates operation under cryogenic conditions.

The microscope enables identification down to few ppm and localization with a submicron beam of various elements. These elemental mappings can be completed with spectroscopic analyses, performed on single points or as 2D images as well. Typical scientific questions concern the co-localization and/or speciation of trace elements in heterogeneous matrices at the micron scale. Therefore, the submitted proposals are mainly in the field of Environmental Science and Biology. Besides, since a few years, applications in the field of Cultural Heritage are increasing.
Generally speaking, the non-invasive character, low detection limit, high lateral resolution and high chemical sensitivity of SR-based X-ray techniques are highly relevant properties for the chemical characterization of art materials, which are usually precious, heterogeneous and complex. The chemistry involved in both the past history of the objects, i.e. during their fabrication, and in their future life, i.e. during preservation and restoration treatments, can be addressed by such techniques. A particular focus will be made on recent applications of XAS (at the ESRF, but more generally on synchrotron facilities) in art conservation.