Spectrometric Response of Large Volume CdZnTe Coplanar Detectors

Abstract

In this paper, the spectroscopic performance of a new large volume coplanar detector is studied. Spectrometric results using classical techniques are presented. The new unit confirmed that this design of coplanar-grid anodes provided an acceptable balance between anode weighting potentials. The material of this detector is not as homogeneous as desirable. Nonetheless, the detector demonstrated a resolution of the order of 2.7% FWHM for 662 keV. The spectroscopic properties at different interaction depths were studied by making use of a multiparametric digital system. Depth sensing achievable resolution is quantified by making use of this setup. The interaction profile at different depths of the detector was compared with that expected in ideal detectors.

An adaptation of the multiparametric digital system was applied to the study of the waveforms generated in the preamplifiers connected to the electrodes. Induced charge waveforms at selected interaction depths were analyzed in order to study the deviations in the interaction depth profiles found between simulation and theory. The causes are attributed to trapping effects in the detector bulk. Unexpected pulses are explained by modeling the charge drift in the detector. The mobility of electrons in these detectors was studied by digital signal analysis, which gave a value close to 950 cm2/V/s at room temperature. Results of the dependence of mobility of electrons with temperature are presented in the operation temperature range of these detectors.