The mechanism of edge effect in CdZnTe pixel detector and an improved design of pixel sizes of anode

In this paper, the mechanism of the edge effect in Cadmium Zinc Telluride (CZT) pixel detectors is studied, and the energy spectrum performance and the charge collection efficiency of peripheral pixels with reduced sizes are analysed by computer-aided simulation and measurement. The results show that the distribution of the weighting potential, which is determined by the electrode structure, has significant influence on the edge effect. Reducing the sizes of peripheral pixels can optimize the weighting potential and improve the detection performance. A detector with reduced peripheral pixel sizes is prepared. We build a gamma imaging system using this kind of detector, test the spectrum response to ¹³⁷Cs@662 keV and image a M10 nut under the collimated ²⁴¹Am@59.5 keV. The measured spectrum of the edge/corner/intermediate pixels is consistent with the simulated spectrum and the obtained countingtype gray-scale image of the nut clearly shows its shape and sizes. These results prove that reducing peripheral pixel sizes has practical value in gamma imaging technology.