This work investigates the capabilities of a state-of-the-art photon counting CdZnTe Timepix3 detector by combining sub-pixel resolution and energy weighted imaging to resolve and identify metallic particles (< 35 µm) in contaminated pharmaceutical hard capsules. While previous pixelated photon counting semiconductor detectors such as the Timepix or Medipix3 allowed single event analysis only for low photon fluxes that are rather unsuitable for imaging purposes, the new Timepix3 detector allows for the analysis of single events even at high X-ray fluxes due to its data driven data output. The challenges of the project like sufficient charge collection and processing of larger data sets for sub-pixel imaging, the influence of charge sharing and X-ray fluorescence on the spatial and energy resolution as well as 3 different approaches of the energy weighted identification of the metallic powders will be discussed.
This work presents the characterization and performance of the first 3 mm CdTe sensor connected to a readout chip of the Medipix/Timepix detector family. The integration and parameters of a developed cluster analysis are shown to fully utilize the detector configuration in a gamma camera. Spectroscopic measurements regarding the common radioactive sources 137Caesium, 152Europium and 241Americium are investigated. The absorption efficiency of the 3 mm CdTe sensor is compared to a 0.45 mm CdTe and a 1 mm CdTe detector configuration. The charge sharing effect is successfully reduced with cluster analysis and the thicker sensor profits greatly from the greater absorption efficiency, especially in higher energy ranges (> 100 keV). The information gain of the charge sharing effect regarding cluster size and shape can be further used for identification of the investigated isotopes.
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