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Measurement of the ionization response of amorphous selenium with 122 keV γ rays

Author(s): Li, X; Chavarria, AE; Bogdanovich, S; Galbiati, Cristiano; Piers, A; et al

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Abstract: <jats:title>Abstract</jats:title> <jats:p>We performed a measurement of the ionization response of 200 μm-thick amorphous selenium (aSe) layers under drift electric fields of up to 50 V/μm. The aSe target was exposed to ionizing radiation from a <jats:sup>57</jats:sup>Co radioactive source and the ionization pulses were recorded with high resolution. Using the spectral line from the photoabsorption of 122 keV γ rays, we measured the charge yield in aSe and the line width as a function of drift electric field. From a detailed microphysics simulation of charge generation and recombination in aSe, we conclude that the strong dependence of recombination on the ionization track density provides the dominant contribution to the energy resolution in aSe. These results provide valuable input to estimate the sensitivity of a proposed next-generation search for the neutrinoless ββ decay of <jats:sup>82</jats:sup>Se that aims to employ imaging sensors with an active layer of aSe. We estimate the RMS line width of the integrated ionization signal from neutrinoless ββ decay events (of deposited energy 3.0 MeV) to be 2.0% for a drift field of 50 V/μm. The energy resolution can be improved to 1% by correcting for the charge yield as a function of ionization density along the imaged electron tracks.</jats:p>
Publication Date: 21-Jun-2021
Electronic Publication Date: 21-Jun-2021
Citation: Li, X, Chavarria, AE, Bogdanovich, S, Galbiati, C, Piers, A, Polischuk, B. (2021). Measurement of the ionization response of amorphous selenium with 122 keV γ rays. Journal of Instrumentation, 16 (06), P06018 - P06018. doi:10.1088/1748-0221/16/06/p06018
DOI: doi:10.1088/1748-0221/16/06/p06018
EISSN: 1748-0221
Keywords: Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc); Double-beta decay detectors; Gamma detectors (scintillators, CZT, HPGe, HgI etc); Solid state detectors
Pages: P06018 - P06018
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Instrumentation
Version: Author's manuscript

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