PIXE in an external microbeam arrangement for the study of finely decorated tartesic gold jewellery items

Narrow regions on Tartesic (Spain, 6th century B.C.) gold jewellery items have been studied by PIXE. An external microbeam (250 μm) of 2.3 MeV protons has been used in order to determine the elemental concentrations in the various tiny elements and specially at places of solders. The comparison with results on jewellery items of Etruscan origin (same period as Tartesic but coming from the North of Italy) allows us to identify the differences in the workmanship of goldsmiths of these geographic regions. The details on the surface topography of wires, granulations, filigrees were observed with an electron microbeam in order to complement the micro-PIXE results.

Accurate quantitative elemental analyses have been obtained from PIXE spectra by a comparison with reference samples and an extensive calculation of thick target parameters. The background has been carefully calculated by using a physical approach and not only computer adjustment. The necessary corrections to take the topography of these very irregular surfaces into account were calculated. They include the secondary fluorescence effects and the variation of Kα/Kβ (for Cu and Ag) or Lα/Lβ (for Au) X-ray intensity ratios as a function of the surface orientation relative to the incident beam and the detector positions.