Investigations on the Performance of a 5 mm CdTe Timepix3 Detector for Compton Imaging Applications

Nuclear power plant decommissioning requires the rapid and accurate classification of radioactive waste in narrow spaces and under time constraints. Photon-counting detector technology offers an effective solution for the quick classification and detection of radioactive hotspots in a decommissioning environment. This paper characterizes a 5 mm CdTe Timepix3 detector and evaluates its feasibility as a single-layer Compton camera. The sensor's electron mobility-lifetime product and resistivity are studied across bias voltages ranging from -100 V to -3000 V, obtaining values of μeτe = (1.2 ± 0.1) × 10^-3 cm²V^-1, and two linear regions with resistivities of ρI=(5.8±0.2) GΩ cm and ρII=(4.1±0.1) GΩ cm. Additionally, two calibration methodologies are assessed to determine the most suitable for Compton applications, achieving an energy resolution of 16.3 keV for the ¹³⁷Cs photopeak. The electron's drift time in the sensor is estimated to be (122.3 ± 7.4) ns using cosmic muons. Finally, a Compton reconstruction of two simultaneous point-like sources is performed, demonstrating the detector's capability to accurately locate radiation hotspots with a ∼51 cm resolution.