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Title: Delayed charge recovery discrimination of passivated surface alpha events in P-type point-contact detectors

Abstract

The Majorana Demonstrator searches for neutrinoless double-beta decay of 76Ge using arrays of high-purity germanium detectors. If observed, this process would demonstrate that lepton number is not a conserved quantity in nature, with implications for grand-unification and for explaining the predominance of matter over antimatter in the universe. A problematic background in such large granular detector arrays is posed by alpha particles. In the Majorana Demonstrator, events have been observed that are consistent with energy- degraded alphas originating on the passivated surface, leading to a potential background contribution in the region-of-interest for neutrinoless double-beta decay. However, it is also observed that when energy deposition occurs very close to the passivated surface, charges drift through the bulk onto that surface, and then drift along it with greatly reduced mobility. This leads to both a reduced prompt signal and a measurable change in slope of the tail of a recorded pulse. In this contribution we discuss the characteristics of these events and the development of a filter that can identify the occurrence of this delayed charge recovery, allowing for the efficient rejection of passivated surface alpha events in analysis.

Authors:
 [1]
  1. Univ. of Washington, Seattle, WA (United States). Center for Experimental Nuclear Physics and Astrophysics, and Dept. of Physics
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Org.:
Majorana Collaboration
OSTI Identifier:
1460330
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physics. Conference Series
Additional Journal Information:
Journal Volume: 888; Journal Issue: 1; Journal ID: ISSN 1742-6588
Publisher:
IOP Publishing
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Gruszko, J. Delayed charge recovery discrimination of passivated surface alpha events in P-type point-contact detectors. United States: N. p., 2017. Web. doi:10.1088/1742-6596/888/1/012079.
Gruszko, J. Delayed charge recovery discrimination of passivated surface alpha events in P-type point-contact detectors. United States. doi:10.1088/1742-6596/888/1/012079.
Gruszko, J. Fri . "Delayed charge recovery discrimination of passivated surface alpha events in P-type point-contact detectors". United States. doi:10.1088/1742-6596/888/1/012079. https://www.osti.gov/servlets/purl/1460330.
@article{osti_1460330,
title = {Delayed charge recovery discrimination of passivated surface alpha events in P-type point-contact detectors},
author = {Gruszko, J.},
abstractNote = {The Majorana Demonstrator searches for neutrinoless double-beta decay of 76Ge using arrays of high-purity germanium detectors. If observed, this process would demonstrate that lepton number is not a conserved quantity in nature, with implications for grand-unification and for explaining the predominance of matter over antimatter in the universe. A problematic background in such large granular detector arrays is posed by alpha particles. In the Majorana Demonstrator, events have been observed that are consistent with energy- degraded alphas originating on the passivated surface, leading to a potential background contribution in the region-of-interest for neutrinoless double-beta decay. However, it is also observed that when energy deposition occurs very close to the passivated surface, charges drift through the bulk onto that surface, and then drift along it with greatly reduced mobility. This leads to both a reduced prompt signal and a measurable change in slope of the tail of a recorded pulse. In this contribution we discuss the characteristics of these events and the development of a filter that can identify the occurrence of this delayed charge recovery, allowing for the efficient rejection of passivated surface alpha events in analysis.},
doi = {10.1088/1742-6596/888/1/012079},
journal = {Journal of Physics. Conference Series},
number = 1,
volume = 888,
place = {United States},
year = {2017},
month = {9}
}

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Works referenced in this record:

The MAJORANA DEMONSTRATOR Neutrinoless Double-Beta Decay Experiment
journal, January 2014

  • Abgrall, N.; Aguayo, E.; Avignone, F. T.
  • Advances in High Energy Physics, Vol. 2014
  • DOI: 10.1155/2014/365432

Computational models of germanium point contact detectors
journal, January 2012

  • Mullowney, Paul; Lin, Ming-Chieh; Paul, Kevin
  • Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 662, Issue 1
  • DOI: 10.1016/j.nima.2011.09.061