Comparison of benchtop devices for X-ray fluorescence imaging based on scanning and full-field techniques

Abstract

In this paper, several benchtop XRF imaging techniques and setups were compared, most of which are found in laboratories for rapid, preliminary composition determination and elemental distributions. The advantages and disadvantages of individual XRF techniques are introduced. The techniques tested in the comparison include macro-XRF scanning with a miniature X-ray tube, micro-XRF scanning with a focused X-ray beam of an X-ray tube with polycapillary optics, and full-field XRF with a spectrometric pixel detector. Nevertheless, synchrotron-based XRF techniques are not considered. The experiments were performed on glass samples which correspond to materials with an intermediate effective atomic number, along with, containing an abundance of elements whose X-ray lines span nearly the whole energy range of XRF. The standard reference material NIST 1412 was used to determine the sensitivities of the XRF setups. A glass pendant with an enameled decoration served as a representative artifact for the demonstration of the individual XRF imaging techniques. A simple Monte Carlo simulation was introduced for calculating expected XRF images for short acquisition times. This method was applied to obtain simulated on-the-fly XRF images. Macro-XRF scanning with small X-ray tubes is efficient with collimators down to approximately 0.5 mm. In order to achieve sufficient sensitivity even for narrower beams, X-ray tubes with polycapillary optics must be used. The sensitivities for micro-XRF scanning and full-field XRF imaging with parallel optics are quite similar when the X-ray sources have the same power.