Improvements in the PIXE system of the CENTA laboratory with application in the contamination studies of tree rings in Slovakia

This study describes the process of calibrating the PIXE system at the CENTA laboratory in the current upgraded geometry. A constant trend of H values was observed in the energy region of 1-15 keV, with a sharp decline below 1 keV. However, bremsstrahlung intensity was significantly affected by the target orientation, causing an improvement in the detection limit by a factor of 1.5-5. Tree rings of Norway spruce (Picea abies), representing a clean air site in Jasn ' a, and of Black poplar (Populus nigra), representing a contaminated site in Bratislava, were analyzed. Bratislava tree ring data showed generally higher concentration levels when compared with Jasn ' a (e. g., for K and Mg), however, there were some exceptions (e.g., for Al, S, Fe), where the Bratislava data showed lower concentrations. Bratislava concentration trends did not show a significant correlation with ambient emissions. A visible effect of the heartwood-sapwood boundary layer was observed.