Efficiency measurement on 6.0 cm3 3-D CdZnTe detectors

This work investigate the full energy and total efficiencies of large volume CdZnTe detectors. The efficiencies of three 20 mm × 20 mm × 15 mm pixelated CdZnTPe detectors were measured using the H3Dv2 Application Specific Integrated Circuit (ASIC) readout system developed by Brookhaven National Laboratory with un-collimated ²⁴¹Am, ¹³⁷Cs, and ⁶⁰Co sources. One detector was made by eV-Products while the other two were manufactured by Redlen Technologies. Geant4 simulation results are used as the benchmark. The relative efficiency, defined as the ratio between the measured efficiency and the simulated efficiency, is an indicator of the active volume in the detector. The total relative efficiency is close to 100% for all three sources. However, there are deficits on full energy efficiency at higher energies, especially for ⁶⁰Co. This loss of full energy efficiency could be due to distorted electric field near the detector side surfaces. Our measurements showed that Redlen detectors have similar efficiency with that of eV-Products detector. The active volume of each detector is more than 90%.