A.E. Bolotnikov a, C.A. Brown b, G.A. Carini a, J. Christian b, L. Cirignano b, C.R. Deane a, A. Dellapenna a, G. Deptuch a, J. Fried a, S. Herrmann a, A. Kargar b, H. Kim b, M.R. Koslowsky c, P. Maj a, S.V. Manthena a, A.L. Miller c, S. Miryala a, A.M. Norris c, Y. Ogorodnik b, G. Pinaroli a, K.S. Shah b 1
a Brookhaven National Laboratory, Upton, NY, 11793, USA
b Radiation Monitoring Devices, Watertown, MA, 02472, USA
c Bubble Technology Industries, Chalk River, ON, K0J 1J0, Canada
## Abstract
Position sensitivity enables the correction of response non-uniformities in room-temperature semiconductor detectors caused by crystal defects and other factors. It can also be used to pinpoint the exact location of crystal defects responsible for the response variations. This work describes a technique for revealing and visualizing the detector regions affecting the charge collection efficiency in CdZnTe (CZT), TlBr, and CsPbBr3 detectors configured as position-sensitive virtual Frisch-grid (VFG) devices. The technique correlates the photopeak events in energy spectra with their spatial distributions inside the detectors using the position information. By selecting the events from narrow energy intervals within a photopeak, we can visualize the detector volumes with particular charge collection efficiencies, which, in turn, correlate with the locations of electrode and crystal defects. We demonstrate this technique in several examples. Columnar structures in the volume plots (position distribution maps) are consistent with signal losses near or at the anode in selected samples of CZT and TlBr. Structures exhibiting a distinct depth dependence are consistent with grain boundaries or other crystal defects.
## Introduction
Response non-uniformities, or the dependence of signal amplitudes on the location of the interaction points, are common in compound semiconductor detectors. There are multiple causes of the response non-uniformities: detector geometry, material inhomogeneities, and readout electronics – all of them, if uncorrected, decrease the energy resolution of the collective gamma spectrum. Because the response non-uniformities correlate with the locations of interaction points, they could be corrected in position-sensitive detectors using correction matrices, generated during the detector calibration, in real time.
In the same way as position sensitivity allows for correcting response non-uniformities, it can also be used to reveal the location of crystal defects and other areas inside the detectors causing the response variations. Here we describe a technique for revealing the crystal defects and demonstrate it in several examples of CdZnTe (CZT), TlBr, and CsPbBr3 detectors configured as position-sensitive virtual Frisch-grid (VFG) devices [[1], [2], [3]].
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/using-3d-position-sensitivity-to-reveal-response-non-uniformities-in-cdznte-tlbr-and-cspbbr3-detectors.html