The impact of high-energy tailing in high-purity germanium gamma-ray spectrometry on the activity determination of 224Ra using the 241.0 keV emission

S M Collins; R Shearman; P Ivanov; P H Regan

doi:10.1016/j.apradiso.2019.109021

The impact of high-energy tailing in high-purity germanium gamma-ray spectrometry on the activity determination of ²²⁴Ra using the 241.0 keV emission

Appl Radiat Isot. 2020 Mar:157:109021. doi: 10.1016/j.apradiso.2019.109021. Epub 2019 Dec 11.

Authors

S M Collins¹, R Shearman², P Ivanov², P H Regan³

Affiliations

¹ National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK; Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK. Electronic address: sean.collins@npl.co.uk.
² National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK.
³ National Physical Laboratory, Hampton Road, Teddington, Middlesex, TW11 0LW, UK; Department of Physics, University of Surrey, Guildford, Surrey, GU2 7XH, UK.

PMID: 31889679
DOI: 10.1016/j.apradiso.2019.109021

Abstract

High-energy tailing is an often-overlooked component in high-purity germanium gamma-ray spectrometry when performing the non-linear least squares fit of a full-energy peak. This component comes from the incomplete restoration of the baseline prior to the next pulse being processed and therefore is an issue of increased count rates. In the current work, the impact of this oversight is shown through the dynamics and decay characteristics of ²²⁴Ra and its radioactive decay progeny. Multiple measurements of two samples, separated from the decay progeny and at differing activities, have been made. The results of full-energy peak fitting of the convoluted 238.6 keV and 241.0 keV full-energy peaks with and without the high energy tailing component are presented. Trends in the observed activity that approximate the ingrowth of ²¹²Pb have been observed where no high-energy tailing component is used, with maximum relative differences of 2% and 5% determined.