The macro-XRF scanning system from XGLab is equipped with a compact measuring head composed by a high efficiency X-ray generator source with an Rh anode (50kV and 200µA) and by a large area Silicon Drift Detector (SDD) (50 mm2, energy resolution of 130eV at MnKα) which allows for fast and sensitive multi-elemental analysis. An integrated video microscope camera is used to control and select the area under investigation while two point lasers allow for exact point positioning at a measuring distance of 10 mm. The measuring head is mounted on a motorised frame with an X-Y-Z stage (largest scanned area 45×60cm2) with continuous movement for mapping application.The X-ray beam can be collimated on the sample surface with spot diameter of 0.5, 1 or 2 mm. A fast digital electronics has been specifically developed for mapping application acquiring spectra for each pixel. A dedicated software is used for multi-element map reconstruction. Definite security procedures must be followed: only trained users can work with the instrument, they must stay behind the probe head at a distance ≥ 2.7m. The object to be investigated (and thus the direction of the X-ray beam) must be positioned in front of a concrete wall of thickness ≥ 5 cm.
X-rays are highly penetrating and generally allow to non-destructively probe the entire painting stratigraphy. Hence the registration of elemental maps in a wide atomic number range (Z>12) allows for the investigation of the pigment use by the artist and for studying the historical evolution of the paint, also revealing hidden paint layersin the case of pentimenti, retouchings and over-paintings etc