Element Identification by K-Edge Imaging Using Spectroscopic Photon Counting Detectors

The reliable identification of multiple elements in a single X-ray exposure is advantageous in various fields of interest like medicine, nondestructive materials research, homeland security, waste management, and the mining industry. Elements of interest can be identified by analyzing how an X-ray transmission spectrum correlates with the element’s K-edge. Timepix3 (TPX3)-based photon-counting detectors offer the possibility of spectroscopic X-ray imaging, allowing to record the changes in the transmission spectrum and, consequently, for element identification. This article presents element identification using a single X-ray image recorded with a 2 mm CdZnTe TPX3 detector. The analysis is based on the K-edge method, analyzing sharp edges in the absorption spectrum of an exposed object. The work describes the follow-up investigation of a material discrimination study utilizing several discrete energy thresholds. Single layers of 200
$\mu \text{m}$
thick foils of different metals have been investigated as elements of interest. No overlaying elements or composites have been used in the absorption phantom. The method shown is limited to a specific absorption ratio inside the element, which means the influence of the absorber on the spectrum measured must result in a recognizable K-edge. Within this work, it is possible to identify eight out of nine different elements of the absorption phantom with K-edges distributed over an energy spectrum from 8 to 70 keV.