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Energy-loss correction in charge sharing events for improved performance of pixellated compound semiconductors

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journal contribution
posted on 21.04.2020, 14:47 by S Bugby, K Koch-Mehrin, M Veale, M Wilson, J Lees

The sharing of charge between multiple pixels can significantly degrade the energy resolution of small pixelated compound semiconductor detectors. This paper describes an energy calibration and reconstruction technique to correct for absorbed energy that is split over two neighbouring pixels, defined as bipixel events. Results were obtained with a 1 mm thick CdTe detector with 250 µm pixel pitch and an inter-pixel spacing of 50 µm, using the STFC HEXITEC ASIC.

The proportion of charge sharing events was found to be 54% for photons at 59.5 keV when applying a noise threshold of 3 keV. Across the energy range investigated, bipixels were the predominant shared event type and the absolute fraction of shared events was found to be dependent on the noise threshold used.

The reconstruction technique described reduces the degradation of energy resolution due to charge sharing in bipixel events compared to simple charge sharing summing techniques. This improved counting efficiency compared to using only isolated events and improved energy resolution compared to pixel addition techniques. When only isolated pixels were included, a FWHM energy resolution of 1.42 keV at 140.5 keV was achievable; inclusion of bipixel events using pixel addition results in an energy resolution of 3.33 keV whereas the reconstruction technique described here results in an energy resolution of 2.14 keV. When bipixel events are combined with single pixel events, the number of counts within the 140.5 keV photopeak of 99mTc increased by over 100%.

Funding

This work was supported by a Science and Technologies Facilities Council (STFC) grant – CLASP ST/M007820/1 – and fellowship – ST/R00501X/1. K.A. Koch-Mehrin is supported by a University of Leicester LISEO studentship. The event analysis code is based on work originally carried out by GM Hansford, University of Leicester. The authors would like to acknowledge the contributions of LK Jambi, King Saud University, and WR McKnight and J Michalowska, University of Leicester, to data collection and analysis. This research used the ALICE High Performance Computing Facility at the University of Leicester.

History

Citation

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 940, pp. 142-142 (151)

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

VoR (Version of Record)

Published in

Nuclear Instruments and Methods in Physics Research Section A: Accelerators

Volume

940

Pagination

142-142 (151)

Publisher

Elsevier

issn

0168-9002

Acceptance date

10/06/2019

Copyright date

2019

Available date

12/06/2019

Publisher version

https://www.sciencedirect.com/science/article/pii/S0168900219308484?via=ihub

Language

en