Synchrotron XRF mapping of large paintings

An Australian team has reported on its study of a historical self-portrait by Sir Arthur Streeton (1867-1943) with fast-scanning X-ray fluorescence microscopy using synchrotron radiation. They employed the event-mode Maia X-ray detector, which has the capability to record elemental maps at megapixels per hour with the full X-ray fluorescence spectrum collected per pixel. The 25 megapixel elemental maps were obtained across the 200 × 300 mm² scan area. The size of the beam used was 10 × 10 μm². As heavy brushstrokes of lead white overpaint conceal the portrait, the excitation energy was chosen as 12.6 keV in order to avoid the influence of extremely strong Pb L fluorescence as well as Raman inelastic scattering. For more information, see the paper, "High-Definition X-ray Fluorescence Elemental Mapping of Paintings", D. L. Howard et al., Anal. Chem. 84, 3278 (2012).