# External Beam IBA Measurements for Cultural Heritage
## 1 Introduction  
Nuclear physics has contributed for several decades to the cultural heritage field via a wide range of analytical methods to determine the composition or the age of an artifact, and it played a role in the conservation of art and archaeological objects. The availability of small and medium energy accelerator facilities has enabled an extensive use of analytical ion beam techniques to obtain information about archaeological and art objects: ion beam analysis (IBA) methods for compositional studies and accelerator mass spectrometry (AMS) for radiocarbon dating.  
IBA are, generally, a suite of analytical techniques that exploit the interactions of rapid (\(\sim\)MeV energy) charged particles with matter to determine the elemental composition and structure of the surface regions of solids inferred from measured quantities such as the X-ray, gamma-ray, and charged particle spectra [1]. IBA are based on the interactions, at both the atomic and the nuclear level, between accelerated charged particles (ion beam) and the bombarded material. When a charged particle moving at high speed strikes a material, it interacts with the electrons and nuclei of the material atoms, gradually losing energy and slowing down. This interaction can lead to the emission of particles or radiation whose energy is characteristic of the elements that constitute the sample material. Moreover, the emission rates of those particles and radiation are proportional to the concentration of the emitting elements.  
IBA share some common features: they are multi-elemental (all elements from H to U can be determined simultaneously), they allow quantitative analysis with high sensitivity (down to 1-100 ppm with experimental uncertainties in the few percent range), they arenon-destructive, and, in principle, do not require any sample extraction, preparation, or pre-treatment (thus, further measurements with other complementary techniques can be carried out). Although they probe only the surface of the material--the first tens of microns, depending on the range of the bombarding charged particles, that, in turn, depends on the type of matrix--they allow to obtain the depth profile of the elements. Ion beams can be focused using a system of magnetic quadrupole lenses (depending on the application it could be a doublet, a triplet or a quintuplet) to dimensions with sub-micron lateral resolution (nuclear microprobe) and microanalysis at some particular point or region can be performed. If the focused microbeam is scanned over the sample, or, conversely, the sample is moved in micrometric steps in the plane perpendicular to the microbeam direction, it is possible to obtain an imaging of the elemental spatial distribution.  
IBA can contribute to cultural heritage studies [2], mainly by identifying the materials through the analysis of major elements, by helping in understanding the provenance of materials (sources of raw materials and trade routes) with the analysis of trace elements and by determining the manufacture technology thanks to the high spatial and depth resolutions achievable with these analytical techniques.