Novel mobile 3D confocal X-ray fluorescence (3D CXRF) scanner for the non-invasive characterization of layered cultural heritage artworks

• Novel, vacuum-free, mobile 3D Confocal XRF scanner for non-invasive heritage studies. • Fast 3D volumetric elemental imaging with dwell times down to 200 ms. • Validated on standards, mock-ups, and four heritage objects. • Unlocks in situ non-invasive depth-resolved 3D CXRF in cultural heritage. The study of cultural heritage artworks presenting a complex stratigraphy traditionally relies on invasive cross-sectional analyses involving microsampling. Such destructive approaches, nevertheless, raise conservation concerns, and should be minimized or avoided. Achieving non-invasive, depth-resolved elemental characterization of these heterogeneous strata, however, remains a major analytical challenge. Among the few non-destructive techniques capable of directly providing depth-resolved information in a portable setup, Confocal X-ray Fluorescence (CXRF) stands out as particularly promising. However, most existing CXRF instruments are restricted to 1D dimensional depth (z) scans of a location, lacking the speed required for practical mapping of three-dimensional millimetric volumes, and therefore failing to capture key information. To overcome this, we have developed a mobile, fast (dwell times as low as 0.2 s), vacuum-free 3D CXRF scanner specifically designed for the non-invasive, in situ investigation of layered cultural heritage artworks, with complementary 2D micro-XRF imaging capabilities. We present here the spectrometric figures of merit of the device, measurements of standards and paint layer mock-ups, and demonstrate its powerful analytical capabilities on diverse cultural heritage objects: an Egyptian cartonnage fragment, a Roman coin, an archeological ceramic, and a polychrome majolica.