Increasing the sensitivity of micro X-ray fluorescence spectroscopy through an optimized adaptation of polycapillary lenses to a liquid metal jet source

Abstract

The combination of brilliant liquid metal jet sources (LMJS) and polycapillary lenses yields substantial advantages in the excitation efficiency of traces of transition metals by micro-X-ray fluorescence spectroscopy (μXRF) and confocal μXRF in the laboratory. We show, that it is possible to especially adapt the parameters of polycapillary lenses to achieve an optimized performance in transmission and exit focal spot size. Furthermore, we demonstrate an energy dependent influence of the source spot size on the effective transmission of the lenses, which increases with decreasing field of view of the polycapillary lenses. A measurement on a mussel foot cross section using a μXRF setup with a specially designed polycapillary lens in combination with the LMJS shows a significant increase of the excitation efficiency for vanadium. A 24 times higher net peak fluorescence intensity for V K radiation is achieved resulting in well-defined and detailed vanadium structures compared to measurements performed with a state-of-the-art μXRF setup.