Equipment design and performance characterization of full field x-ray fluorescence (FF-XRF) element distribution imaging system with combined collimating lens (CCL).

This work describes a full field x-ray fluorescence element distribution imaging system with a combined collimating lens (CCL), which is more suitable for a higher x-ray energy range (12 keV-30 keV). The system consists of an optical-use charge-coupled device (CCD) camera coupled to a combined collimating lens (CCL), which includes pinhole collimator and x-ray window, x-ray tube, and sample room. The continuously variable magnification of 0.5-2 is achieved under a compact structure. The x-ray spectrum and two-dimensional element distribution mapping of the irradiated sample are obtained by processing a series of images acquired by using the CCD camera in a single photon counting mode. The energy resolution is 275 eV at the reference energy of 14.957 keV (yttrium Kα, Z = 39). The limit of detection is 46.41 ppm by measuring yttrium standard solution. The spatial resolution is 135 μm when using a 100 μm pinhole at the magnification of 1. Samples made by metal foils and mineral pigments are tested, and the results proved that the system was reliable when detecting elements of a high atomic number.