Quantitative PIXE Analysis Research Articles

New approaches for investigating paintings by ion beam techniques

Abstract Up to now, among the IBA techniques, only PIXE has been used for analyzing paintings. However, quantitative PIXE analysis is sometimes difficult to interpret due to the layered structure, the presence of varnish and organic binder and, in some cases, discoloration of the pigments has been observed due to the interaction of the ion beam with the compounds. In order to improve the characterization of paintings, we propose some alternative experimental procedures. First of all, backscattering spectrometry (BS) and PIXE are simultaneously combined in order to collect complementary information such as layer thickness and organic compound quantification. The simultaneous PIXE and BS experiments also have the advantage of being able to analyze the same area in one experiment. This combination, implemented with an external beam, was directly applied on paintings and on painting cross-sections for the study of Italian Renaissance masterpieces. We have obtained valuable results not only on the pigment itself but also, for the first time, on the binder to pigment proportion which is not well documented in the ancient recipes. Moreover, in order to restrain beam damages due to the ion stopping power, we propose to analyze very thin painting cross-sections by a combination of PIXE–RBS and Scanning Transmission Ion Microscopy (STIM).

Analysis of single aerosol particles collected in urban and cave environment by proton microprobe

Quantitative PIXE analysis was performed on several single aerosol particles collected with cascade impactor by the scanning proton microprobe of Debrecen. The cascade impactor samples were collected at an urban location in Debrecen and in a speleotherapeutic cave situated under Budapest during the winter of 1998. The aerosol samples have already been analysed by bulk PIXE technique. Elemental concentrations for 23 elements and also the size of the particles were determined. Cluster analysis was carried out to identify the different particle groups. The contribution of the different types of particles to each size fraction were investigated with special regard to the smaller size fractions which are interesting from the point of view of the speleotherapy. Traces of anthropogenic pollution were also shown in the cave aerosol, and the possible composition of particles containing these pollutants is given. Comparison of the urban and cave aerosol particles is also discussed.

Characterisation of single aerosol particles from Debrecen region, Hungary using microPIXE

Quantitative PIXE analysis was performed on 412 single particles (with 2–12 μm diameter) from urban and rural aerosol samples collected in the Debrecen region, Hungary at the Oxford SPM. Hierarchical cluster analysis was carried out to help in the data interpretation. Using single particle analysis it was possible to discriminate several kinds of soil characteristic to the Debrecen region. Some possible sources of these coarse mode particles are discussed.

Influence of energy straggling on quantitative PIXE analysis

Examples of numerical calculations aimed to estimate the effect of proton energy straggling on quantitative PIXE are presented. Special attention has been taken to low energy PIXE and external beam PIXE. X-ray yield calculations including beam energy straggling for beam energies ranging from 0.3 to 3 MeV were carried out and the X-ray yield variations due to the energy straggling were determined. Proton energy straggling was calculated using the uncorrected Bohr's formula. K-and L-shell ionization cross sections variations were considered for the X-ray yields calculations. Results indicate that in some cases the error induced on the produced X-ray yield may be up to a few percent on low energy PIXE. For external beam PIXE and high energy PIXE the X-ray yield variations are very small (less than 0.5%).

QUANTITATIVE ANALYSIS OF POWDER SAMPLE (SOIL AND CITY ASH)

Quantitative analysis of powder sample, soil, ash and so on, which consists of rich heavy metal elements that are not decomposed easily with acid or alkali was attempted. Usually, powder sample was ground with an agate mortar, mixed with binding material cellulose and pelletized for quantitative PIXE analysis. However, the resulting pellet target is thick. Accordingly, when heavy elements are included in sample, it gives effect on PIXE spectrum. Namely, matrix effect arises on it. So firstly, a fixed quantity of molybdenum was added into sample and mixed as standard material in order to determine the concentration of the most typical element, iron included in sample. Then the mixed powder were pelletized and analyzed to determine the concentration of iron. Next, original powder sample was pushed on a backing film to make thin target, and the thin target was analyzed as internal standard of determined iron by ordinary PIXE analysis method. In the result, concentrations of major elements of powder sample were determined quantitatively.