X-Ray Fluorescence Spectroscopy (XRF) and Monte Carlo characterization of a unique Nuragic artifact (Sardinia, Italy)

The chemical composition of a unique bronze artifact known as the “Cesta” (“Basket”) belonging to the ancient Nuragic civilization of the Island of Sardinia, Italy has been analyzed by combining X-ray Fluorescence Spectroscopy (XRF)withMonte Carlo simulations using the XRMC code. The “Cesta” had been discovered probably in the XVIII centurywith the first graphic representation reported around 1761. In a later draft (dated 1764), the basket has been depicted as being carried upside-down on the shoulder of a large bronze warrior Barthélemy (1761), Pinza (1901),Winckelmann (1776) . The two pictorial representations differed only by the presence of handles in the most recent one. XRF measurements revealed that the handles of the object are composed by brass while the other parts are composed by bronze suggesting the handles as being a later addition to the original object. The artifact is covered at its surface by a fairly thick corrosion patina. In order to determine the bronze bulk composition without the need for removing the outer patina, the artifact has been modeled as a two layer object in Monte Carlo simulations

A combined XRF/Monte Carlo Simulation study of multilayered Peruvian metal artefacts from the tomb of the priestess of Chornancap

An innovative methodological approach based on XRF measurements using a polychromatic X-ray beam combined with simulation tests based on an ultra-fast custom-made Monte Carlo code has been used to characterize the bulk chemical composition of restored (i.e., cleaned) and unrestored multilayered Peruvian metallic artifacts belonging to the twelfth- and thirteenth-century AD funerary complex of Chornancap–Chotuna in northern Peru. The multilayered structure was represented by a metal substrate covered by surface corrosion patinas and/or a layer from past protective treatments. The aim of the study was to assess whether this new approach could be used to overcome some of the limitations highlighted in previous research performed using monochromatic X-ray beam on patina-free and protective treatment-free metal artifacts in obtaining reliable data both on the composition on the bulk metals and on surface layers thickness. Results from the analytical campaign have led to a reformulation of previous hypotheses about the structure and composition of the metal used to create the Peruvian artifacts under investigation

Age of Cosmic-Ray Protons Computed Using Simple Configurations of the Galactic Magnetic Field

The influence of various magnetic field structures of the Galactic disk on some fundamental properties of cosmic-ray protons has been investigated with a simulation program, which generates cosmic-ray trajectories in the disk volume. The regular component of the Galactic magnetic field has been approximated by three different geometrical configurations (circular, elliptical, and spiral). Ages, residence times, and grammages of cosmic protons in various conditions are calculated and discussed. These calculations indicate that the proton age is strongly influenced by the magnetic field configuration but weakly affected by the field strength. The age of cosmic-ray protons in the spiral field turns out to be 6.7 × 106 yr, and the corresponding matter thickness 12 g cm-2

First results on the use of a EDXRF scanner for 3D imaging of paintings

A 3D map of chemical elements distribution from energy-dispersive X-ray fluorescence (EDXRF) analysis would be a perfect conclusion in a detailed study of any type of artifact. This map can be easily achieved by using synchrotron light as source of radiation, and microoptics both at the source and at the detector. In such a manner a micro-voxel is irradiated and detected, which can be at any depth with respect to the surface of the artifact. This method is effective but needs a high-intensity X-ray source; therefore, its use in archaeometry is limited. An alternative method is proposed in the present paper, which uses a portable EDXRF-device to measure the altered Kα/Kβ or Lα/Lβ-ratios, which allow to locate the chemical elements. Several examples are described

Synchrotron-based crystal structure, associated morphology of snail and bivalve shells by X-ray diffraction

Synchrotron-basedhigh-resolutionX-raypowderdiffractionspectrafromthebodypartsofasnailand bivalve(CaCO3), havebeenrecordedwithPilatusareadetector.ExperimentswereperformedatDesy, Hamburg, Germany,utilizingtheResonantandDiffractionbeamline(P9),with15keVX-rays (λ¼0.82666Å).Theexternalshelloftheselivingorganisms,iscomposedofcalciumcarbonate,which carries strongbiologicalsignal.Itconsistsofsomelightelements,suchas,Ca,CandO,whichconstitute part ofthesofttissueandothertraceelements.Theknowledgeofthesediffractionpatternsandhence the understandingofstructuresatmolecularlevelareenormous.Theapplicationofsynchrotronra- diation topowderdiffractioniswellsuitedforsamplesofbiologicalnatureviachangesintheirpatterns and alsotoinvestigatecrystallographicphasecomposition.WiththeuseofRietveldrefinement proce- dure, tothehigh-resolutiondiffractionspectra,wewereabletoextractthelatticeparametersofor- thorhombic polymorphofCaCO3, themostabundantmineralproducedbytheselivingorganisms.The small sizeofthecrystalliteisaveryimportantfactorrelatedtothebiologicalstructure.Thenatural model presentsacombinationoforganicandinorganicphaseswithnanometersize.Forthepresent study,wealsousedthescanningelectronmicroscopy(SEM)toexploretheassociatedmorphologyofthe snail andbivalve

Non-destructive characterization of archeological Cu-based artifacts from the early metallurgy of southern Portugal

In this study, Monte Carlo (MC) simulations combined with energy dispersive X-ray fluorescence (EDXRF) spectroscopy have been used to characterize non-destructively a collection of Cu-based artifacts recovered from two archeological sites in southern Portugal: (a) the Chalcolithic E.T.A.R. site of Vila Nova de Mil Fontes and (b) the Middle Bronze Age site of Quinta do Estácio 6. The metal artifacts show a multilayered structure made up of three distinct layers: (a) brownish carbonate soil-derived crust, (b) green oxidized corrosion patina, and (c) bulk metal. In order to assess the reliability of the EDXRF-based Monte Carlo simulations to reproduce the composition of the alloy substrate in archeological bronze artifacts without the need to previously remove the superficial corrosion and soil derived patinas, EDXRF analysis together with scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS) was also performed on cleaned and patina-/crust-coated areas of the artifacts. Characterization of the mineralogical composition of the corrosion products in the surface patinas was further determined by means of X-ray diffraction (XRD). Results suggest that the adopted EDXRF/Monte Carlo protocol may represent a safe and fast analytical approach in the quantitative characterization of the bulk chemical composition of Cu-based metal artifacts even in the presence of fairly thick corrosion patinas and/or soil-derived encrustations at the surface of the archeological objects

Removal of the continuum of X-ray spectra using morphological operators

In energy dispersive X-ray fluorescence analysis, the estimation and removal of the continuum on which the X-ray spectrum is superimposed is a primary requirement. The algorithms commonly used are either complex, or in the case of, e.g., neural network algorithms, computation-intensive. They usually require strong constraints and/or hypotheses on the data or the shape of the continuum. Moreover, if the continuum amplitude is comparable to or bigger than the peak amplitudes, some of these algorithms can lose peaks. A new approach to continuum removal based on mathematical morphology is proposed here. The new algorithm permits fast continuum elimination without peak deterioration. Other than a rough estimate on the widths of the peaks, the new method does not require additional information about the spectrum. The method can also be applied without modification to background elimination from gamma ray spectra. This new method is described and results obtained from real and simulated spectra are discussed and evaluated

Spectroscopic characterization of Phoenician-Punic coins

Sardinia hosted many Phoenician and Punic communities, as integrated forms of pacific cohabitation with the Lebanese merchants or actual colonies for the exploitation of the rich mines and wealthy coastal emporia under the Carthaginians (750-250 B.C.). One of their most important settlements is that of Mount Sirai, in the south west of the island, whose excavation revealed a complex structure of the site and allowed the discovery of excellent finds, as steles, everyday-life objects and tools, grave goods, amulets and coins. Punic coins were made by gold, electrum or, more commonly, by bronze. The first coin mintage from Carthage dates back to the IV century B.C. Whether the mintage was exclusive to Carthage or permitted outside the city too is still a matter of debate. There is the possibility that mintages were allowed in Sardinia (320-238 B.C. as well as in 216), in Spain (237-209 B.C.) and Southern Italy (216-203 B.C.). We have analyzed ten of these bronze coins (Fig. 1) to unveil the secrets of their mintage, origins and inner structure. Some traditional spectroscopic techniques such as X-ray diffraction (XRD) and fluorescence (XRF) have been used for this purpose, allowing us to learn about their mineral content (XRD) and elemental composition (XRF) [1,2]. Here we report about these findings

New Techniques in Diagnostic X-ray Imaging: A Simulation Tool and Experimental Findings

Abstract Absorption X-ray imaging is a well-established technique. However it is still a challenging task in its search for a compromise between the need for high spatial resolution and high contrast and the request to keep the dose delivered to the patient within acceptable values. New imaging techniques are under investigation, like the use of new X-ray sources, phase contrast imaging or K-edge imaging. Monte Carlo or analytic simulations are often the best way to test and predict the effectiveness of these techniques. A new simulation tool for X-ray imaging will be presented together with some applications to the characterization of new X-ray sources, in-line phase contrast effect and angiographic K-edge imaging. Simulation results will be compared also with experimental dat

Selection of Interface DoFs in Hub-blade(s) Coupling of Ampair Wind Turbine Test Bed

International audienceSubstructure coupling is an important tool in several applications ofmodal analysis. It is particularly relevant in virtual prototyping of complex systems and responds to actual industrial needs, especially in an experimental context. Furthermore, the reverse problem, the decoupling of a substructure from an assembled system, arises when a substructure cannot be tested separately but only when coupled to neighboring substructures, a situation often encountered in practice. In this paper, the dynamic behavior of the Ampair test bed wind turbine rotor, made by three blades - each one bolted to the hub at three points - is analyzed. The aim is both to identify the dynamic behavior of the rotor starting from the frequency response functions (FRFs) of blades and hub, and to select a reduced set of relevant DoFs to represent the interface between blades and hub. FRFs to be used in the coupling procedure are obtained starting from FE model of each substructure, by using a super-element based computational approach. The decoupling problem, with the aim of identifying the dynamic behavior of each blade from the FRFs of the assembled rotor and of the hub, is also considered