Calibration method for confocal x-ray microanalysis with polychromatic excitation

PEREZ, R.D.; STOYTSCHEW V.; SOSA, C.; MALZER, W.; SÁNCHEZ H.J.; MANTOUVALOU, I; KANNGIESSER B.

Viena

Conferencia; European Conference on X-Ray Spectrometry; 2012

IAEA

The confocal setup consists of x-ray lenses in the excitation as well as in the detection channel. In this configuration, a probing volume defined by the overlap of the foci of both x-ray lenses is analyzed. Scanning the sample through this micro volume, 1-3 dimensional studies can be performed. For depth profiling studies, only the scan of the probing volume in the normal direction to the sample is required. An elemental analysis is obtained by the detection of the x-ray fluorescence produced in the micro volume. During the last years, experiments with confocally aligned x-ray lenses have been performed at various synchrotron radiation sources. This setup proved to be capable to supply three-dimensional or depth-sensitive information on the elemental composition of a sample with a spatial resolution of around 10 to 20 micrometers. The quantitative reconstruction of the composition of stratified material by means of confocal micro-XRF with monochromatic excitation relies on a three-dimensional model for the probing volume. The model has been implemented into analysis software and recently validated for monochromatic excitation. In contrast to most of the confocal setups at synchrotron sources using monochromatic excitation radiation, a quantification scheme for polychromatic excitation, like with x-ray tubes or polychromatic synchrotron radiation, has not a development accord to the potential of the technique. In this work, the three dimensional model for the probing volume is applied for the calibration of the confocal setup implemented in the Brazilian Synchrotron Radiation Source (LNLS) using white beam. The experimental parameters of the theoretical model were obtained by means of the depth profile analysis of several thin films (MicromattersTM). The calibrated confocal setup was used to quantify reference standards in order to validate the calibration procedure. Our results for elemental concentrations had good match with the nominal values of light matrix reference standards.