Coupling a wavelength dispersive spectrometer with a synchrotron-based X-ray microscope: A winning combination for micro-X-ray fluorescence and micro-XANES analyses of complex artistic materials

X-Ray fluorescence (XRF) is one of the most established techniques for the analysis of works of art. It offers several features-such as non-invasiveness, richness of information, in situ analysis with portable instruments and 2D and 3D micro-imaging when performed at synchrotron sources-which are increasingly used in the field of Cultural Heritage science. However, the complexity of artistic materials may lead into complex XRF spectra. Overlapping of fluorescence emission lines can make XRF analyses prone to error. In this article, we discuss the attributes of the polycapillary-based Wavelength Dispersive X-ray Spectrometer (WDS) developed at the X-ray micro-spectroscopy ESRF beamline, ID21. With spectral resolution of a few tens of eV, this system allows better separation of neighbouring emission lines. Its pros and cons for micro-XRF point analysis, micro-XRF mapping and micro-XANES are addressed, with a particular focus on Cultural Heritage applications. Possible extensions towards micro-RIXS are also discussed.