Improvement and characterisation of pixelated Cadmium-Zinc-Telluride detectors for use in neutrino-less double-beta decay searches

• Main Author: Spencer, Simeon James Matthew
• Published: University of Birmingham 2011
• Subjects: 530.0724; QC Physics
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541543

Cadmium-Zinc-Telluride (CZT) detectors are seen as an ideal material for constructing intrinsic detectors for neutrino-less double-beta decay. However, the poor mobility of the charge carriers (specifically the holes) is known to result in poor resolution and decreased photo-efficiency. Simulations of this effect show that the resolution is a function of the detector width/depth ratio, suggesting pixelation as a solution. Pixelation of the detector also allows background sources, and even single-beta events to be selectively vetoed. However, this technique alone cannot completely remove the effect of the reduced resolution. A technique which combines ‘Gain Matching’ and removal of the low energy tail is outlined and qualified for the resulting improvements in resolution and efficiency. The sharing of events between multiple pixels is also studied and the quality of reconstructed events is established. The pixelated nature of the detector also opens the door to operation of the detectors as a ‘Compton Camera’. Accordingly, Geant4 simulations are compared with real-world measurements, to establish the benefits of pixelation upon the operation of the detectors as a ‘Compton Camera’. Finally, comparisons are performed between Geant4 simulations and real-world measurements of intrinsic photopeak efficiency calculations.