Particle Induced X-ray Emission
Description
In the cultural heritage area, the more frequent mode of Ion Beam Analysis is PIXE (Particle Induced X-ray Emission). It is a nondestructive elemental analytical technique. When a material is exposed to an ion beam, ionisation interactions occur that give off X-rays which are characteristic of the encountered elements. PIXE is a powerful yet non-destructive elemental analysis technique now used routinely by geologists, archaeologists, art conservators and others to help answer questions of provenance, dating and authenticity. The technique was first proposed in 1970 by Sven Johansson of Lund University, Sweden. The main characteristics of PIXE are: - Analysis can be performed directly on the object, but restricted to its surface, with an open air beam facility, through a very thin window (for instance 0.1 m Si3N4), and with the help of an helium flux between the window and the surface of the analyses object (no sampling) - Atomic number of the detected elements Z > 9 to 11 (O to Na) - Practical minimum detection limit: approximately 10-9, thus possibilities of trace detection and/or analysis - Approximate beam spot diameter: 10 m to 1 mm on the surface of the object, and step by step scanning device Recent extensions of PIXE using tightly focused beams (down to 1 μm) gives the additional capability of microscopic analysis. This technique, called microPIXE, can be used to determine the distribution of trace elements in a wide range of samples.
Recent applications involved: establishing the geographical origin or various gemstones, mapping of inclusions in gemstones, of pigments in illuminated manuscripts, analysis of metal pin Renaissance drawings by A. Dürer or Pisanello, characterisation of ancient metallurgical processes, study of the glazing technique of Renaissance terracotta statues or lustre ceramics, study of the lixiviation process of buried lead glasses….
PIXE