X-Ray response of CZT ring-drift detector

We present the results of an experimental study of a new type of CdZnTe detector of hard X- and gamma-rays - a ring-drift detector. The device consists of a double ring electrode structure surrounding a central point anode and a guard ring beyond the outer anode ring. The detector is operated in two distinctively different modes of charge collection -pseudo hemispherical and pseudo drift. We study the detector response profiles obtained by scanning the focused X-ray beam over the whole detector area for X-rays from 10 to 100 keV. To interpret the experimental data, we derive an analytical expression for the spatial distribution of the electric field inside the detector and identify carrier collection patterns for both modes of operation within the drift approximation. We show that this model provides a good understanding of measured profiles.