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Laboratory for X-ray spectrometry
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Head: dr.Peter Kump
Collaborators: dr. Marijan Nečemer, Mag. Zdravko Rupnik, dr. Dušan Ponikvar

Activities in the laboratory are as follows:

  • software development for quantitative elemental analysis using X-ray fluorescence spectrometry (XRF)
  • development and construction of portable and laboratory XRF analyzers
  • development , construction, and application of total reflection X-ray spectrometry for the analyses of trace elements in very small samples (of mass of few 10 µg)
  • application of X-ray analytical techniques in different applied projects on environmental samples (air, soil, water,..), in analyses of mineral content in different parts of plants for the purposes of plant physiology research, for the analysis of metals and alloys in industrz applications, and in analyses of different archaeological object and paintings.

The X-ray analyzer constructed from an X-ray tube with Ag anode (3 W power and 30 kV) and a Si PIN detector of 200 eV resolution at 5.9 keV was developed in our laboratory for the LUCKY d.o.o. company!

All analyzers developed in our laboratory utilize the software for adjustment of the excitation conditions on the tube, for spectrum acquisition and analysis, and for the respective quantitative and qualitative elemental analyses. The software is unified in a single window in LABVIEW environment, and different programs are activated just by clicking the mouse on appropriate commands. This window is shown on Fig. 2.

The software for quantitative elemental analysis includes few different models adapted to different kinds of samples. In principle the models require the use of an additional measurement of the absorption in the sample, or an application of the internal standard. Beside the resulting concentrations of the measured elements also the data for that part of the sample matrix, which does not give measurable information in the spectrum is obtained (so called residual matrix usually composed of very low-Z elements, which do not respond in fluorescent spectrum due to their low energies). An example of a residual matrix obtained after the analysis of a sample of organic origin is shown on Fig. 3!

The module for the Total Reflection X-ray Fluorescence spectrometry (TXRF), developed in our laboratory is shown on Fig. 4. The source of the monochromatized focused excitation beam is the fine focus Mo anode X-ray tube (2 kW, 50kV, 40 mA). With such a TXRF system the absolute sensitivity for elemental analysis is just few pg, but the weight of the whole sample is few 10 µg. The sample is deposited on an optically flat quartz substrate and the excitation beam of 17.4 keV hits the substrate and the sample as well at an angle smaller than the angle of total reflection for the substrate material ( ≈ 1.8 mrad). The fluorescent X-rays are measured by an X-ray detector positioned very close to the substrate (around 1 mm). Very much reduced scattering of the incident radiation due to the total reflection of almost all the beam, and a detector positioned very close to the sample, cause a strong increase of the sensitivity for elemental analysis.