Application of a biparametric method using a twin shaping filter on CZT detectors

The performance of high Z solid state detectors has been significantly improved over the last decade. For X and gamma ray spectroscopy applications CdTe/CdZnTe is really appealing combining high detection efficiency, no requirement for cooling to cryogenic temperatures, good spectroscopic performances, good time response and imaging capabilities. The spectroscopic behavior of this type of detector, however, is limited by the trapping of the charge carriers (particularly the holes), which can degrade the detector response, depending on the distance between the charge generation position and the collecting electrodes. To improve the detection efficiency and the energy resolution the optimization of electrode geometry and the correction biparametric methods can be used. We propose a biparametric technique using a double pulse shaping active filter in order to analyze the detector signals: one slow, which is proportional to the energy of the photon and one fast, which depends on the position of the interaction of the incident photon in the detector material with respect to the collecting electrode. The experimental results obtained with the application of this method on CdZnTe detectors are presented for different primary photon energies and switching off the integrator stage of the fast shaping amplifier to achieve a more direct information on electron rise time.