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Limits on uranium and thorium bulk content in Gerda Phase I detectors


Baudis, Laura; Hiller, Roman; Kish, Alexander; Miloradovic, Michael; Mingazheva, Rizalina; Ransom, Chloe; et al (2017). Limits on uranium and thorium bulk content in Gerda Phase I detectors. Astroparticle Physics, 91:15-21.

Abstract

Internal contaminations of $^{238}$U, $^{235}$U and $^{232}$Th in the bulk of high purity germanium detectors are potential backgrounds for experiments searching for neutrinoless double beta decay of $^{76}$Ge. The data from Gerda Phase I have been analyzed for alpha events from the decay chain of these contaminations by looking for full decay chains and for time correlations between successive decays in the same detector. No candidate events for a full chain have been found. Upper limits on the activities in the range of a few nBq/kg for $^{226}$Ra, $^{227}$Ac and $^{228}$Th, the long-lived daughter nuclides of $^{238}$U, $^{235}$U and $^{232}$Th, respectively, have been derived. With these upper limits a background index in the energy region of interest from $^{226}$Ra and $^{228}$Th contamination is estimated which satisfies the prerequisites of a future ton scale germanium double beta decay experiment.

Abstract

Internal contaminations of $^{238}$U, $^{235}$U and $^{232}$Th in the bulk of high purity germanium detectors are potential backgrounds for experiments searching for neutrinoless double beta decay of $^{76}$Ge. The data from Gerda Phase I have been analyzed for alpha events from the decay chain of these contaminations by looking for full decay chains and for time correlations between successive decays in the same detector. No candidate events for a full chain have been found. Upper limits on the activities in the range of a few nBq/kg for $^{226}$Ra, $^{227}$Ac and $^{228}$Th, the long-lived daughter nuclides of $^{238}$U, $^{235}$U and $^{232}$Th, respectively, have been derived. With these upper limits a background index in the energy region of interest from $^{226}$Ra and $^{228}$Th contamination is estimated which satisfies the prerequisites of a future ton scale germanium double beta decay experiment.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:2017
Deposited On:15 Feb 2018 14:26
Last Modified:19 Feb 2018 11:14
Publisher:Elsevier
ISSN:0927-6505
OA Status:Hybrid
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1016/j.astropartphys.2017.03.003

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