Synchrotron study of charge transport in a CZT ring-drift detector

We report on experimental and theoretical results obtained with a CdZnTe (CZT) detector with a versatile read-out scheme: the ring detector. This detector has been tested extensively both in our laboratories and at the HASYLAB synchrotron facility and has demonstrated excellent energy resolution of up to 0.73%, over a wide dynamic range covering 6−662 keV. The key feature in this design is carefully managed charge transport, which eliminates the hole contribution, and optimizes the electron collection. We have developed a theoretical model of this detector, to enable the optimization of the read-out structure as a function of detector dimensions. A comparison between X-ray scans across the detector and model calculations shows that the model already captures all the major detector features, but still leaves a few challenging questions related to CZT surface conductivity. A defect in the detector, which breaks the expected cylindrical symmetry of the charge transport, is examined in detail by differential spectrometry, a powerful technique, which exploits differences in X-ray absorption between bulk and defect.