Ž. Šmit

The performance of the Ljubljana ion microprobe

In August 2000 the setup of the Ljubljana ion microprobe, based on OM 150 triplet, has been completed. The beam line is installed at the 10° exit port of the 2 MeV Tandetron accelerator. It is equipped with motor driven slits, a precise five-axis goniometer and a spherically shaped measuring chamber with detectors for PIXE, PIGE, PESA, SE and RBS. In order to understand the beam optics along the complete system, consisting of the tandem accelerator and the beam line optical elements, an interactive computer code, based on a linear approximation, has been developed. The program is used both to determine the optimal parameters of the tandem focusing system in its daily use and to develop new beam line configurations. Test measurements performed on a copper grid yielded a spatial resolution of 1.0×1.5 μm2 in the high current mode (30–100 pA) and 0.5×0.9 μm2 in low current mode (104 counts/s). First analytical results confirmed excellent performance of the new Ljubljana ion microprobe.

K-shell ECPSSR cross sections for analytical applications

Abstract Methods for the ECPSSR cross section calculation are examined. Direct integration procedures of the electronic form factor and the methods using the tabulated universal functions are reviewed and compared. A simple yet accurate direct integration procedure is proposed. Different approximations for the energy loss correction are shown to differ up to few percent in the low velocity region.

PIXE/PIGE characterization of medieval glass

Abstract The glasses of Ljubljana, related historically to the spread of glassworks in the Venetian style, were studied by a combined PIXE/PIGE method based on the in-air proton beam. The contribution of PIGE was determination of Na, Mg and Al oxides that provided (1) non-ambiguous characterization of the alkali and limestone component, (2) stable concentration evaluation algorithm relying on the normalization of all metal oxides to 100%. The majority of investigated samples form a compact group with small variations due to the alkalis used; a clear distinction from a few imported objects confirms local production. The raw materials in medieval glassworks differ significantly from those of Late Antiquity.

Analysis of medieval glass by X-ray spectrometric methods

Systematic investigation of the 16th century glasses of Ljubljana is motivated by the spread of Italian glass-working technology into central Europe. The glass was probed using the external beam PIXE technique due to its non-destructiveness. Initial test measurements were performed by the methods of PIGE, XRF, electron probe microanalysis, and LA‐ICP‐MS. The PIXE data were evaluated statistically using the principal component analysis and minimizing the stress function. The manufacturing procedures were indicated by the Rb/Sr content in the glass: the investigated glasses were mainly produced with the ash (not potash) of halophitic plants. ” 2000 Elsevier Science B.V. All rights reserved.

K-MM radiative Auger effect in solid Ca, Ti and Cr targets after ionization with 0.7–1.5 MeV protons

Abstract Radiative Auger (RAE) X-ray spectra were measured for the first time on Ca, Cr, and Ti targets after ionization by 0.7–1.5 MeV protons. The energies of the RAE X-ray transitions were compared with the energies obtained from the Auger transitions. The RAE intensities relative to the diagram K β13 line were deduced and compared with the available data from X-ray fluorescence and electron capture ionization. The relative yields obtained for Ca, Ti, and Cr were (3.14 ± 0.47), (2.44 ± 0.37) and (2.91 ± 0.58)%, respectively.

Microdistribution and composition of usewear polish on prehistoric stone tools

The use of prehistoric stone tools can be classified according to the usewear traces on the tool working edge. The polish resulting from the use of the tool contains minute amounts of the original worked material. Using the micro PIXE mapping technique, a comparative study of a set of experimental tools and a set of mesolithic end-scrapers was performed. For both sets of tools, increased concentrations of elements associated with the worked material were found in small localized regions. The composition of these regions was probed by point measurements and two main groups of P, Ca and S, K compounds were identified. The X-ray attenuation in the polish layer suggests that the deposited elements diffuse into the bulk flint.

Spread of façon-de-Venise glassmaking through central and western Europe

Abstract The major and trace composition of a series of 16th century glass fragments, originating from the ruins of different 15–17th century castle sites in the neighborhood of Ljubljana (Slovenia) was determined. The resulting compositions are compared to those obtained from archaeological glass finds originating from Ljubljana city center, Antwerp (Belgium) and Venice (Italy). In these urban centers, historic documents describe the existence of a flourishing glass making and working industry in the 16th century. Electron probe X-ray microanalysis (EPXMA) combined with microscopic synchrotron induced X-ray fluorescence (μ-SRXRF) was used to analyze the glasses from the Slovenian castles and from Antwerp while ion beam analysis (proton induced X-ray and γ-emission PIXE/PIGE) was used for the Ljubljana samples. A comparison of the major glass compositions of the latter glass samples obtained by means of EPMA and the ion beam methods revealed that the differences between the two sets of data are generally smaller than 10%, except in the case of concentrations smaller than 1% w/w where typical values of 20% of relative deviation are encountered. In contrast to Antwerp, where both local and Venetian glass compositions are encountered, the Ljubljana and Slovenian castle glasses feature a composition that closely resembles that of Venetian vitrum blanchum glass.

Elemental Analysis of Celtic Coins

Abstract Surface compositions of silver Celtic coins discovered in Slovenia were determined by PIXE. Bulk values were measured for some examples cut to half of their thickness. Thick target analysis avoided the use of standards; an iterative procedure was used in order to deduce concentrations.

The analysis of thick target metal alloys

Abstract The application of proton induced X-ray emission (PIXE) for elemental analysis of metal alloys was studied. A simple correction function is introduced, which takes into account thick target effects. Calibration standards are thus avoided and the concentrations are obtained from X-ray production cross sections. The method was tested and good agreement was found between the reference and measured concentrations.

Usewear-induced deposition on prehistoric flint tools

Abstract The use of stone tools on different materials produces different types of polish. Its microscopic appearance and chemical composition vary with the worked material and is an indicator of the tools use. The PIXE method was used to investigate the composition of the polish produced by working bone and specific woods. For a set of experimental tools, the most abundant polish element was Ca, the surface density of which reached several 10 μg/cm2. The deposition of P is correlated to that of Ca and these two elements can be used to distinguish between working bone and wood. For archaeological artefacts, deposits were found which were comparable to those on the experimental tools, thus implying their probable use on wood and bone.