M.Á. Ontalba Salamanca

External microbeam set-up at the CNA (Sevilla) and its application to the study of Tartesic jewellery

Abstract A new external microbeam system has been installed recently at the +45° beam line of the 3 MV Pelletron accelerator at the Centro Nacional de Aceleradores (Sevilla, Spain). The facility, based on the system from Oxford Microbeams (OM), includes two sets of slits, a doublet of magnetic quadrupole focusing lenses, a Faraday cup and an accurate positioning device. In addition, a beam profile monitor (BPM) and a quartz viewer have been installed in the line to facilitate the microbeam production. The first PIXE application of the new facility was made in the field of Archaeometry, on the study of Tartesic gold artefacts (700–500 BC, SW of Spain) from Ebora and other archaeological sites. The aim of the analysis was to perform an exhaustive and systematic study about the soldering procedures that were employed by the goldsmiths along the Valley of Guadalquivir River after the Phoenician colonisation.

PIXE and SEM studies of Tartesic gold artefacts

Abstract Gold jewellery artefacts of Tartesic origin (700-500 B.C.) have been studied using external beams for quantitative PIXE. Collimators along the incident proton beam (2.7 MeV) allowed the artefacts to be irradiated in narrow regions down to 350 μm in diameter. Special attention has been paid to the procedure of soldering in various narrow regions of the bindings of filigrees, twisted wires, narrow strips and granulations on finely decorated items. By using reference materials and thick target PIXE programs including all matrix effects (X-ray cross sections, attenuation coefficients, secondary fluorescence), relative concentrations of Au, Ag and Cu in various regions have been determined. The results seem to indicate that solderings were made by local fusion and brazing. No procedure of solid state diffusion bonding like in Etruscan jewellery has been identified. Qualitative results using imaging and EDX induced by a very narrow electron beam (SEM) give complementary information to the quantitative determinations obtained from the PIXE measurements.

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.

Characterization of pre-Hispanic pottery from Teotihuacan, Mexico, by a combined PIXE–RBS and XRD analysis

Abstract A combined analysis of IBA techniques (Proton Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectroscopy (RBS)) and a complementary study by X-ray Diffraction (XRD) were performed to characterize pottery corresponding to the Epiclassic period (A.D. 700–900) from Teotihuacan, Mexico. Elemental compositions of pottery samples were measured by simultaneous PIXE and RBS using 2.6 MeV protons. Red, white and brown pottery pigments were studied by non-vacuum PIXE and a proton beam of 3 MeV. The various mineralogical phases of the pottery were identified by XRD. From pottery elemental compositions and its mineralogical phases, some differences among the pottery samples and groups were established.

Radiological and multi-element analysis of sediments from the Proserpina reservoir (Spain) dating from Roman times

The Proserpina dam was built in Roman times to provide drinking water to Emerita Augusta (todays Mérida in SW Spain). During maintenance work, a sediment core was extracted, offering an excellent opportunity to analyze the historical environmental impacts of the dam and its reservoir over the 2000 years since Roman times. In order to establish an accurate chronology, (14)C ages were determined by accelerator mass spectrometry (AMS). Core samples were assayed for their content in uranium and thorium series isotopes, (40)K, and the anthropogenic radionuclides (137)Cs, (90)Sr, and (239+240)Pu. Potassium-40 presented the highest activity level and was not constant with depth. The uranium and thorium series were generally in equilibrium, suggesting there had been no additional input of natural radionuclides. The presence of (137)Cs was only found in relation with the global fallout in the early 1960s. Multi-element assays were performed using the PIXE and PIGE techniques. Some variations in the multi-element concentrations were observed with depth, but the sediment core could be considered as clean, and no presumptive anthropogenic pollutants were found. Nevertheless, an unusually high Zn content was detected at depths corresponding to pre-Roman times, due to geological anomalies in the area.

Ion beam analysis of pottery from Teotihuacan, Mexico

This work presents the characterization of sherds and pottery paints from Teotihuacan, Mexico, belonging to the Mesoamerican Epiclassic (700‐900 AD) and Postclassic (900‐1521 AD) periods. A simultaneous analysis by Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectroscopy (RBS) was carried out to measure the elemental composition of pottery and clays sources of the Teotihuacan region. Also, a semiquantitative X-Ray Diffraction study (XRD) was performed to determine the mineralogical phases. From elemental and mineralogical composition, groups of local and foreign sherds were established. Results showed that the PIXE‐RBS method combined with XRD proved to be a very powerful and general procedure for archaeological characterization. Moreover, non-vacuum diAerential PIXE analysis was carried out on colored regions of some representative vessels to study the layered structure of the paints‐clay system. ” 2000 Elsevier Science B.V. All rights reserved.

Pollution effects on stone benches of the Eagle Warriors Precinct at the Major Temple, Mexico City

Abstract During Major Temple archaeological site excavations in Downtown Mexico City, the precinct of one of the most important Mexica military caste, the Eagle Warriors, was discovered. The ceremonial enclosure is composed of three rooms surrounded by paintings on 11 stone benches placed against the walls. Nowadays, these paintings and the stones present the effects of different deterioration processes produced by the underground water level, high humidity, and the presence of soil, water, and air pollutants. Ion beam analysis of samples from the benches and wall paintings was performed using PIXE and RBS techniques. Using enrichment factors of elements relative to iron concentrations, possible contamination by sulfur and chlorine salts was found, as well as airborne zinc scavenged by rain.