Laboratory versus synchrotron XRF scanners for the elemental mapping of large museum specimens

Résumé En

Large area micro-X-ray fluorescence (XRF) mapping, being non-destructive and non-invasive, has become an established analytical technique to obtain spatially resolved information about the elemental composition and distribution of cultural heritage objects. It is particularly applied to flat work of art, but also a wide range of other heterogeneous museum specimens such as fossils. Two main categories of XRF scanners are currently being used: mobile laboratory scanners that allow for the measurement of samples placed horizontally (i.e. laid on a table) and/or vertically (i.e. hung on a wall) [1], and fixed synchrotron set-ups that provide high sensitivity and speciation information for trace elements [2]. With the increased availability of both types of equipment and increased demand from researchers for their use, it can be complicated for the beginner to know which one to choose. In this contribution, we present a multiscale comparison of the possibilities offered by the Bruker M6 Jetstream scanner available at the CRC laboratory (Paris, France) and the PUMA beamline dedicated to ancient materials at the SOLEIL synchrotron (Gif-sur-Yvette, France). The Jetstream allows for the fast mapping (up to 100 mm/s) of large pieces, up to 60 × 80 cm2, with a 100–500 µm adjustable spot size offering a good resolution in the majority of studies. Synchrotron XRF mapping becomes necessary when a smaller beam size, and therefore a higher lateral resolution, is needed, but also to detect elements confine to very small areas and/or present at trace concentrations (up to few ppm). The differences and complementary of both techniques will be illustrated on different cultural and natural heritage applications.