CartiX: Full‐field XRF instrument for cultural heritage

Cartix_header_2

Full-Field XRF for Cultural Heritage

CartiX is a portable, light‐weight, full‐field X-ray fluorescence (XRF) spectrometer developed for cultural heritage applications. CartiX was designed for routine deployment in the field (museum, archaeological site), by placing the instrument at a safe distance (25mm) of the painting or object analyzed using a tripod or similar photographic mount.

Technical details

CartiX is a portable, light‐weight, full‐field X-ray fluorescence (XRF) spectrometer developed for cultural heritage applications. CartiX was designed for routine deployment in the field (museum, archaeological site), by placing the instrument at a safe distance (25mm) of the painting or object analyzed using a tripod or similar photographic mount.

Cartix and the second generation NASA MapX instrument (Sarrazin et al., 2016a) were developed concurrently, sharing most of their design. In operation, fluoresced X‐rays emitted by the sample pass through an X‐ray 1:1 focusing optic that projects a spatially resolved image on a direct‐detection energy‐discriminating CCD. CartiX covers an area of 13mm x 13mm of the surface analyzed without any moving parts. Covering a larger area requires tiling multiple analyses.

The assembly was designed for compactness to allow easy transport to the field and positioning using common photographic equipment (tripod, tripod head, manual slides, etc.).

Walter et al (2019)
  • Detector: CCD back‐illuminated deep‐depletion 1,024 × 1,024 cooled to -60 to -80 °C under sealed vacuum. It is sensitive to photons in the energy range of 3 to 17 keV, limited at low energy by a 200‐μm‐thick beryllium window, and at high energy by the thickness of the charge‐sensitive layer of the CCD (~40 μm). The practical energy resolution during an analysis is 180–200 eV (Mn Kα) depending on the readout speed chosen. 
  • Optic: Micro Pore Optic (MPO), 20μm × 20μm channels metalized with iridium by atomic layer deposition. The optic is placed at 50 mm from the CCD. 
  • X-ray source: Two transmission target Pd X-ray tubes operated at 30 kV and 3 W, placed on opposite sides of the camera to limit topographic contrast and illumination gradients.

During an analysis, the analytical head is positioned at 25 mm from the artwork surface using a slide and either a laser distance meter, or two lasers crossing at the focal plane. In this position, the MPO is equidistant to the artwork surface and the CCD, providing the geometry required for 1:1 focusing.

The camera is driven at up to 3 fps (frames per second). A large number of short acquisitions are collected and processed with dedicated software to extract hyperspectral X‐ray data. Resulting X‐Y‐energy data cubes are saved in HDF5 format and can be analyzed using PyMca (Sole et al., 2007).

Without any post-processing of the data for deconvolution of the optic PSF, the instrument achieves a resolution of ~200 μm. Deconvolution algorithms under development have been shown to substantially improve the spatial resolution of the instrument (Sarrazin et al., 2016b).

CartiX Applications

  • Study of a Caillebotte painting

CartiX was used to study Gustave Caillebotte’s painting Portraits in the Country directly in the exhibition room of the Museum of Art and History Baron Gérard (Bayeux, France). The high spatial resolution chemical data measured with CartiX was used to reveal the artist’s complex use of pigments and the formation of alteration products. (Walter et al., 2019).

Walter et al. (2019)
  • Study of the Pachacamac Idol (Peru)

CartiX was applied to study the polychromy of the Pachamac Idol, with in-situ analysis in the Museum of Pachacamac, Peru. CartiX revealed the distribution of traces of cinnabar and iron based pigments on the Idol, showing that much like with the European antiquity, statues long thought to be originally in the natural color of their material were in fact painted in rich colors. (Sepulveda et al., 2020). 

Sepulveda et al. (2020)

Is CartiX an eXaminArt product?

eXaminArt does not currently offer CartiX as a standard product because it remains an advanced R&D prototype. While it is fully functional and robust, the hardware and software integration does not meet our production standards quite yet.
However, if you are interested in getting a CartiX for your research, or an evolution of this instrument, we can manufacture one for you. Please contact us to discuss your options.

Primary partners

  • CNRS – Centre National de la Recherche Scientifique (France)
  • LAMS – Laboratoire d’Archéologie Moléculaire et Structurale (France)
  • NASA (USA)
  • SETI Institute (USA, CA)
  • Baja Technology LLC (USA, AZ)
  • Photonis (France)

References

  • Sarrazin, P., D. Blake, K. Thompson, M. Gailhanou, J. Chen, T. Bristow (2016a) The MAP‐X μ‐XRF imaging spectrometer. LPSC XLVII #2883, http://www.hou.usra.edu/meetings/lpsc2016/pdf/2883.pdf
  • Sarrazin, P., D. F. Blake, M. Gailhanou, P. Walter, E. Schyns, F. Marchis, K. Thompson, T. Bristow (2016b) Full field x‐ray fluorescence imaging using micro pore optics for planetary surface exploration International, Conference on Space Optics 2016, Proc. of SPIE Vol. 10562, 105622G
  • Sepúlveda, M., Pozzi-Escot, D., Angeles Falcón, R., Bermeo, N., Lebon, M., Moulhérat, C., Sarrazin, P., Walter, P. (2020) Unraveling the polychromy and antiquity of the Pachacamac Idol, Pacific coast, Peru. PLOS ONE 15(1): e0226244. https://doi.org/10.1371/journal.pone.0226244.
  • Solé, V. A., E. Papillon, M. Cotte, P. Walter, J. Susini (2007) Spectrochim. Acta Part B 2007, 62, 63.
  • Walter, P., Sarrazin, P., Gailhanou, M., Hérouard, D., Verney, A., Blake, D. (2019). Full‐field XRF instrument for cultural heritage: Application to the study of a Caillebotte painting. X‐Ray Spectrometry, 48, 274-281. https://doi.org/10.1002/xrs.2841.