Element-selective three-dimensional imaging of microparticles with a confocal micro-PIXE arrangement

A detailed report about the confocal experiment and the corresponding data analysis is presented to determine local atomic concentrations in a thick sample with a micrometer resolution. X-ray emission from a quartz substrate, loaded by aerosol particles, was induced by a scanning proton microbeam and observed by an Si(Li) spectrometer whose field of view was narrowed by a polycapillary lens. A series of X-ray images were recorded at different positions of the sample along the microbeam axis when the particles were driven through the sensitive microvolume. The concentrations reconstructed in three dimensions were used to extract penetration profiles of the strongest X-ray emitters (Fe, Ca, S) in an aerosol sample together with the surface profile of the matrix (Si). The results show exponentially dumped depth profiles with characteristic length depending on particle size. Copyright © 2009 John Wiley & Sons, Ltd.