From Event: SPIE Optical Engineering + Applications, 2017
High-resolution position-sensing has been proposed to correct response non-uniformities in Cadmium Zinc Telluride (CZT) gamma ray detectors by virtually subdividing the area into small voxels and equalizing responses from each voxel. 3D pixelated detectors coupled with multichannel readout electronics are the most advanced type of CZT devices offering many options in signal processing and enhancing detector performance. The main hurdle in achieving high sub-pixel position resolution is the relatively low signal induced on the neighboring pixels because of the electrostatic shielding effect caused by the collecting pixel. In addition, to achieve high position sensitivity one should rely on time-correlated transient signals, which means that digitized output signals must be used. Previous results have shown the benefit of using a focused laser beam to study position resolution in 3D pixelated detectors. We present the results of our studies to measure the amplitude of the pixel signals so that these can be used to measure positions of the interaction points. This is done with the processing of digitized correlated time signals measured from several adjacent pixels taking into account rise-time and charge-sharing effects. In these measurements we used a focused pulsed laser to generate a 10-micron beam at one milliwatt (650-nm wavelength) over the detector surface while the collecting pixel was moved in cardinal directions. The results include measurements that present the benefits of combining conventional pixel geometry with digital pulse processing for the best approach in achieving sub-pixel position resolution with different pixel dimensions ranging from 0.5 mm to 1.72 mm.
Luis A. Ocampo Giraldo, Aleksey E. Bolotnikov, Giuseppe S. Camarda, Gianluigi De Geronimo, Rubi Gul, Jack Fried, Anwar Hossain, Kenan Unlu, Emerson Vernon, Ge Yang, and Ralph B. James, "Sub-pixel resolution in pixelated CdZnTe gamma ray detectors with different pixel sizes (0.5 mm to 1.72 mm) using a focused laser beam (Conference Presentation)," Proc. SPIE 10392, Hard X-Ray, Gamma-Ray, and Neutron Detector Physics XIX, 103920V (Presented at SPIE Optical Engineering + Applications: August 08, 2017; Published: 19 September 2017); https://doi.org/10.1117/12.2275429.5581171733001.
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