Performance Comparison of a Large Volume CZT Semiconductor Detector and a LaBr (Ce) Scintillator Detector

The development of portable nuclear instrumentation demands compact high sensitivity detectors operated at room temperature. The sensitivity of these detectors mainly depends on two parameters: absolute efficiency and energy resolution. In order to provide high efficiency, large volumes are needed. For semiconductor detectors able to operate at room temperature, the largest effective volumes with acceptable resolution are achieved with CdZnTe coplanar-grid and pixel detectors. On the other hand, new scintillation materials were recently developed with spectrometric capabilities only reachable some years ago with semiconductors. In this work we compare the performance of two state of the art detectors of different technologies with a relative large volume: a coplanar-grid CdZnTe detector with dimensions 15 mmtimes15 mmtimes10 mm and a LaBr₃(Ce) crystal with volume 18 mmtimes18 mmtimes30 mm. The CdZnTe crystal was made by Yinnel Tech (USA) and the detector was manufactured by BSI (Latvia). The LaBr₃(Ce) scintillator was grown and encapsulated by Saint-Gobain (France). The energy resolution for the CZT detector is 2.05% FWHM at 662 keV. The resolution for the scintillator at this energy was near 3%. The total efficiency was studied in a setup with calibrated point sources. The experimental spectra were compared with Monte-Carlo simulations performed with Geant4. The implications of the results of this comparison are discussed in the context of the practical use of these units