Characterization of paint layers by simultaneous self-consistent fitting of RBS/PIXE spectra using simulated annealing

Particle induced X-ray emission (PIXE) is now routinely used for analyzing paint layers. Various setups have been developed to investigate the elemental composition of samples or wood/canvas paintings. However, the characterisation of paint layers is difficult due to their layered structure and due to the presence of organic binders. Also, standard PIXE codes do not support the quantitation of depth profiles in the general case. Elastic backscattering (both Rutherford and non-Rutherford) is usually used in ion beam analysis to determine depth profiles. However, traditional data processing using iteration between standard PIXE codes and particle scattering simulation codes is very time consuming and does not always give satisfactory results. Using two PIXE detectors and one particle detector recording simultaneously in an external beam geometry, we have applied a global minimisation code to all three spectra to solve these depth profiles self-consistently. This data treatment was applied to various different cases of paint layers and we demonstrate that the structures can be solved unambiguously, assuming that roughness effects do not introduce ambiguity. (c) 2008 Elsevier B.V. All rights reserved.