Research on a laboratory monochromatic micro X-ray fluorescence spectrometer based on polycapillary X-ray lenses and flat crystal

Abstract

Monochromatic micro X-ray fluorescence (Mμ-XRF) analysis has the advantages of high resolution and low detection limit and is a powerful tool to obtain information on element distribution and concentration in materials. An Mμ-XRF spectrometer for laboratory X-ray tubes is developed in this paper, which mainly composed of an X-ray tube, two polycapillary X-ray lenses and a flat crystal. The polycapillary parallel X-ray lens converts the divergent broadband X-rays emitted by the X-ray tube into quasi-parallel X-rays and projects them onto a flat crystal, where monochromatic X-rays are obtained by crystal diffraction. The monochromatic X-rays are then focused by a polycapillary half-focusing X-ray lens to provide spatial resolution for fluorescence analysis. The combination of the two makes it possible to perform Mμ-XRF under laboratory low-power X-ray tube conditions (5.3 W molybdenum tube). By selecting polycapillary half-focusing X-ray lenses with different parameters, the spectrometer can provide a spatial resolution of tens to hundreds of microns to suit various application requirements. The detection limits of the Mμ-XRF spectrometer are also measured using standard solutions. Experimental results show that the detection limit of Se is 52 μg/L and that the detection limit for light elements such as Mn is 970 μg/L.