Elemental Analysis of Artefacts in Air

Abstract

Quantitative analyses of elemental content in historical and cultural artefacts using ion beam analysis (lBA) have been widely used, however, many artefacts are too large or sensitive to be placed in a vacuum which is required by most non-destructive physical analytical procedures. Ion beams can be safely brought from vacuum into air or other atmospheres (eg. helium) to strike the sample. Such a technique allows non-destructive analysis with the capability of measuring all elements heavier than aluminium, with sensitivities down to parts per million. During 1996, the Department of Applied Physics at Royal Melbourne Institute of Technology in consultation with the Conservation Department of the Museum of Victoria developed an external beam particle induced X-ray emission (PIXE) analysis system. This system allows a beam of ions to fall on an artefact in air generating characteristic X-rays in a similar way to energy dispersive X-ray spectrometry on a scanning electron microscope (SEM). The X-rays are detected allowing quantitative assay of the elements heavier than aluminium in artefacts. Sensitivity of the technique is dependent on the elemental composition of the artefact, but it can be as low as 10 ppm. As the beam is extracted into air, very large objects can be analysed. Other atmospheres can also be used including helium, nitrogen and vacuum. The technique is non-destructive with the vast majority of samples. Studies so far have concentrated on the origin of paint pigments and glasses from an ancient temple in the Egyptian Western Desert, historically important processes for protecting steel from corrosion, and the content of ancient bullets.