The gamma ray interaction depth in 3-D position scnsitive CdZnTe dctectors is currently determined by the pulse height ratio ofthe cathode signal to the anode pixel signal (CIA ratio). In expcriments with our 3-D CdZnTe dctectors, thc photopeak area as a fuuction of the CIA ratio deviates from the expected exponential attcnuation with depth. This indicatcs that the CIA ratio is not proportional to thc true interaction depth. This paper proposes a method to calibrate the measured CIA ratio to thc intcraction depth by modeling the,signals from thc cathode and anode pixels. Knowing the detector's mobility-lifctime products of thc electrons and holes from measurements, the expccted pulsc heights of the signals from thc cathode and anode pixels can bc calculated for differcnt intcraction depths. The rclationship belwcen thc CIA ralios and the interaction depths can then bc determined and used as thc calibration. Thc calculation for our 3-D CdZnTe detectors shows that an 8% crror in depth detcrmination is incurred without the calibration.
Charge sharing effects in a 3-D position sensitive CdZnTe detector have been investigated by Monte Carlo simulations and experimental measurements. The charge sharing is mainly caused by the range of electrons, x-ray emission following by photoelectric interactions, and the diffusion of charge carrier electrons during their drift towards the anodes. A simple model has been developed to include the diffusion effect in the Monte Carlo simulation. Good agreement has been achieved for various irradiation and bias conditions. Based on our model simulations, a 1 mm optimal pixel size is recommended for future 1 cm thick CZT detectors for 662 keV gamma rays.the charge sharing between neighboring pixels.To identify the factors which contribute to charge sharing, we first analyze the measurement multi-pixel fractions using Monte Carlo simulations under various conditions. A simple model based on EGS4 is then developed to investigate the charge sharing effects for our 3-D CdZnTe detectors. Finally, charge sharing effects at various pixel sizes are simulated using our model,and will yield an optimal pixel size for 662 keV gamma rays.
CHARGE SHARING EFFECT
-The energy spectra from 662 keV gamma rays incident from the detector's cathode side were sorted by the number of anode
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.