The mobile micro-XRF scanner (MXRF) consists of a spectrometric head equipped with a low power microfocus X-ray tube (30W) with a Rh anode coupled to a focusing polycapillary optic. The spot of the beam coming out from the primary X-ray source is about 10 microns at 10 keV at a focus distance of 3.5 mm. The detection system is positioned in a 90-degree geometry with respect to the beam direction. It consists of 2 (or 4) SDD detectors (with 50mm2 active area and <130 eV energy resolution at 5.9 keV each) operated in parallel. This experimental set-up improves drastically the chemical sensitivity and the detection limits of the device. A long-range optical microscope (OM) with a 3 microns resolution is installed on the spectrometric head; it is used to guide the MXRF scanning (or the point analysis) and to carry out investigations in OM. A single scan with the XY axes travel system installed on the MXRF instrument can cover an area of 50x50cm2. The system operates with a continuos scanning with a maximum speed up to 100 mm/sec. A Z axis coupled to laser triangulation device is used for a dynamic correction spectrometric head position in order to manatin the source-sample distance uniform during the scanning. Due to the high intensity of the primary X-ray beam and the large solid angle covered by the multi-detectors system, measurements are usually made with a dwell-time per pixel in the range 10ms. Point analyses and/or a 2D elemental mapping (depending on the application) can be performed on the samples in order to better elucidate its elemental composition. Point analyses last typically 10-100s while the MXRF mapping can last several hours. The lateral resolution of the elemental images is in the range of 10-20 microns depending on the chemical element to be investigated. The system is equipped with a central unit (CU) for controlling the operational parameters of the scanner and to operate a dynamic analysis (full deconvolution of the pixel spectra on the fly) providing real-time elemental distribution images to users.
Micro-XRF (MXRF) allows for the investigation of samples in order to better elucidate the elemental distribution images with a high lateral resolution. It provides information on the nature of raw materials, manufacturing technology, provenance, cerative process, presence of retouchings, restorations, conservation treatments and higlight the presence of degradation processes. Micro-XRF allows for both point analyses on a small detail of a large samples and elemental distribution images of large dimension sample as weel. These latter can be obatined with an high lateral resolution (several tens of mega pixel each one down to a 10 micron size). In addtion, the Micro-XRF can be applied for studying in macroscopic context (e.g., paintings). Results are provided on the fly and are immediately available to users already during the scanning.