Sub-Pixel Position Sensing for Pixelated, 3-D Position Sensitive, Wide Band-Gap, Semiconductor, Gamma-Ray Detectors

This article presents a technique to improve the lateral position resolution of pixelated 3-D position sensitive, semiconductor detectors. Improvements in lateral position resolution allow for more precise Compton-imaging calculations, detector-response calibrations, and interaction-based corrections resulting in better spectroscopic and imaging performance. In pixelated detectors, the lateral position resolution of a gamma-ray interaction location is traditionally limited to the dimensions of the individual pixels that constitute an anode array. Sub-pixel position resolution is achieved through algorithms that compare the amount of transient charge induced on pixels that neighbor a charge-collecting pixel. Measurements of the charge induced on the non-collecting pixels are made through analysis of digitized preamplifier pulse waveforms using optimized digital signal processing algorithms. A 2.0 cm × 2.0 cm × 1.5 cm CdZnTe detector with a pixel pitch of 1.72 mm is used to demonstrate the sub-pixel position technique. A 100 μm tungsten collimator is used to verify the accuracy of the method. The measured sub-pixel position resolution is 230 μm at 662 keV. This result is consistent with the predicted value of 180 μm at 662 keV based on a detailed system simulation assuming 4 keV FWHM electronic noise.