PIXE (Particle Induced X-ray Emission) Y (a,a'X) Y

The principle of PIXE method consists in an ionization of the levels near the atomic nucleus. This ionization is followed by a rearrangement of the electronic architecture with emission of characteristic X-ray. The detection of this radiation is realized by Si(Li) or intrinsic Ge semi-conductor detectors. A typical spectrum is shown in the following picture. It is the elementary analysis of vegetals that were contamined by water from a forbidden stocking of industrial wastes.

The computing treatment of this spectrum gives the elementary concentration of more than 20 elements with a detection limit near the ppm. The reality or the confidence in these absolute values given by the PIXE method depends on many factors as the counting statistics, the importance of the background and the spectrum interpretation. When analysing a spectrum, secondary fluorescence, auto-absorption of X-rays by the target and filters, escape peaks and electronic pile-up have to be taken into account. By the way, it is extraordinary that although all these possible errors, the confidence in the results is near 5% in the case of thick targets for which the slowdown of incident particles when they penetrate the target is another error source. Indeed, the probability of X-ray production depends on the incident particle energy and it is not always evident to precisely know the energy lost per unity of charged particle penetration in the analysed matter.

The characteristics of the method are the following:

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Last Update: August 97
Henri-Pierre GARNIR <hpgarnir@ulg.ac.be>
David STRIVAY<dstrivay@ulg.ac.be>