Targeting Ion Beam Analysis techniques for gold artefacts

2009

Une nouvelle approche pour l'authentification des objets en or en couplant la microscopie électronique à balayage et le PIXE en faisceau extrait

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms

Particle induced X-ray emission has been used successfully to analyse a black pendant, twelve Etruscan bronze mirrors and several stamps. Using one simple irradiation the pendant was unexpectedly found to be composed of silver halogenides. The Etruscan bronze mirrors were analysed with both PIXE and atomic absorption spectrophotometry. The results show rather good agreement except in a few cases. The deviations are probably mostly due to inhomogeneities in the mirrors. Old stamps were analysed for several elements to determine the composition of the ink used for printing. The contribution from the paper was subtracted after separate analysis of the edge of the stamp. For one group of stamps clustering of the visually determined nuances occurred in a two-dimensional plot of lead versus zinc, while for another group a plot of mercury versus zinc showed no such clustering.

Applied Physics A, 2016

Noninvasive techniques have become widespread in the cultural heritage analytical domain. The popular handheld X-ray fluorescence (XRF) devices give the elemental composition of all the layers that X-rays can penetrate, but no information on how atoms are bound together or at which depth they are located. A noninvasive portable X-ray powder diffraction/X-ray fluorescence (XRD/XRF) device may offer a solution to these limitations, since it can provide information on the composition of crystalline materials. This paper introduces applications of XRD beyond simple phase recognition. The two fundamental principles for XRD are: (1) the crystallites should be randomly oriented, to ensure proper intensity to all the diffraction peaks, and (2) the material should be positioned exactly in the focal plane of the instrument, respecting its geometry, as any displacement of the sample would results in 2h shifts of the diffraction peaks. In conventional XRD, the sample is ground and set on the properly positioned sample holder. Using a noninvasive portable instrument, these two requirements are seldom fulfilled. The position, size and orientation of a given crystallite within a layered structure depend on the object itself. Equation correlating the displacement (distance from the focal plane) versus peak shift (angular difference in 2h from the standard value) is derived and used to determine the depth at which a given substance is located. The quantitative composition of two binary Cu/Zn alloys, simultaneously present, was determined measuring the cell volume and using Vegard's law. The analysis of the whole object gives information on the texture and possible preferred orientations of the crystallites, which influences the peak intensity. This allows for the distinction between clad and electroplated daguerreotypes in the case of silver and between ancient and modern gilding for gold. Analyses of cross sections can be carried out successfully. Finally, beeswax, used in Roman-Egyptian paintings as ''encaustic'' and in form of emulsion (modified wax), can be detected and, based on the shape of the peaks, these two ways of applying the wax can be distinguished from one another.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1993

The preservation and conservation of mankind cultural heritage has become an important issue worldwide. Non-destructive analytical techniques are suitable, for example, to analyze precious and unique objects of art and archeology. Among those techniques Particle Induced X-Ray Emission (PIXE) has good advantage to identify elemental composition present in these kinds of objects. The Laboratório de Análise de Materiais por Feixes Iônicos-LAMFI of the Institute of Physics of the University of São Paulo has been installed an external beam facility for PIXE analysis. This new setup is being used for the analysis of archeological pottery artifacts, paintings and biological tissues (teeth and bones), which are not compatible with the high vacuum of the regular PIXE target chamber. In addition most art and archeological objects are too large for the evacuated analysis chamber. Applications of this facility will be presented in the analysis of one painting of the beginning of the last century. The chemical elements identified in the painting were Ca, Ti, Cr, Cu, Fe, Zn, Pb and Ba. The PIXE measurements were done non-destructively and no visible damage was observed on the irradiated object.

Journal of Radioanalytical Chemistry, 1982

By using strictly non destructive and non radioactive methods of elemental analysis (PIXE and PIGE), using a 3 MeV proton beam to induce prompt emission of characteristic X-rays or gammarays of the elements and simultaneous photon-spectroscopy with energy dispersive solid state detectors [Si(Li) and Ge(Li)] followed by a computer assisted data handing system, we have determined the relative amounts of copper, silver, cadmium and gold at the surface of more than 30 ancient gold objects. Results on only two items are discussed here. Traces or significant concentrations of cadmium have been detected at nearly all points on or in the neighbourhood of solders on many objects dating from Roman to early Byzantine times. Cadmium concentrations range betwecn 2 to 75 parts per thousand. This range of variation and the relative concentrations of Au, Ag, Cu and Cd at the surface of the objects studied are very different from the figures obtained during analyses of modern soldering alloys. New approaches to solve the problem of Cadmium in ancient jewelry are indicated.

Archaeometry, 1982

a n d M. MARABELLI istituto Centrale del Restauro, R o m , Ital) I N T R O D U C T I O N

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1990

X-ray Spectrometry, 2005

For several years, the specific features of PIXE and PIGE have made them very attractive in the field of archaeometry. Among them, non-destructivity is one of the most important. The possibility of working under atmospheric pressure is also important because of the very different shapes and sizes of the artefacts concerned. However, these ion beam techniques suffer from the same disadvantage: the information coming from x-rays or g-rays produced at different places along the charged particle path is integrated. That prevents one from taking into account the possible element concentration gradients due to multilayered systems or diffusion processes. This paper presents several applications of PIXE and PIGE applied under variable ion beam incident angle. PIGE has been mainly used for studying ancient glass items or glass windows in order to detect or evaluate the glass corrosion process. The examples given for PIGE deal with Roman and Merovingian glass objects and cathedral glass windows and PIXE applications concern studies for resolving the multilayered structure of easel paintings. The set-up allowing one to perform the measurements should be very stable, the rotation axis should pass through the beam axis and the detector should follow the sample movement.

X-Ray Spectrometry, 2000

X-ray fluorescence (XRF) analysis is a non-destructive technique widely used in the study of works of art. It can detect elements having atomic number >15 (phosphorus) and supplies only semiquatitative results, yet it can be helpful in a very wide range of applications. The ENEA Unit for the Safeguard of Cultural Heritage has acquired considerable experience in XRF analysis, investigating more than 500 works of art including easel and mural paintings, mosaics, glasses, ceramics and bronzes. Using XRF analysis sometimes it is possible to detect undocumented pigments or to characterize traditional materials better. This technique of analysis also allows the investigation of impurities of elements having medium or high atomic number, in some cases such impurities can help to establish the provenance of the materials or to characterize differences in the same work due to restoration or to the presence of unoriginal parts. On glass, XRF can identify the nature of the colouring substances and opacifiers. A large number of measurements can be collected for statistical processing and comparison, which is very important, in particular, in the case of mosaics, and yields information which may not be evident if only a single measurement is considered.