Design of high-performance CdZnTe quasi-hemispherical gamma-ray CAPture plus detectors

In this paper we report on the simulation, design, and testing of high performance CdZnTe quasi-hemispherical CAPtureTM Plus radiation detectors. Quasi-hemispherical CdZnTe detectors offer a cost effective alternative to other single-polarity (electron-only) detector configurations such as co-planar grid, pixilated or Frish ring CdZnTe detectors with comparable energy resolution both in the high (>500 keV) and low energy range (<500 keV). We have used the device simulation package eVDSIM to design optimal electrode geometry together with the necessary material selection criteria for charge transport properties of the CdZnTe crystals. A test set of 10x10x5mm3 CAPtureTM Plus detectors has been built using state-of-the art fabrication technology. The measured spectral and efficiency performance of these detectors is compared to the theoretical predictions of simulation. Our results demonstrate that with careful selection of uniform material and high-quality fabrication, this design of CAPtureTM Plus detectors is capable of regularly achieving FWHM @ 81keV of 5%, FWHM @ 122keV of <3%, and FWHM @ 662keV of <2%.