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Title: Naturally occurring 32 Si and low-background silicon dark matter detectors

Abstract

The naturally occurring radioisotope Si-32 represents a potentially limiting background in future dark matter direct-detection experiments. We investigate sources of Si-32 and the vectors by which it comes to reside in silicon crystals used for fabrication of radiation detectors. We infer that the Si-32 concentration in commercial single-crystal silicon is likely variable, dependent upon the specific geologic and hydrologic history of the source (or sources) of silicon “ore” and the details of the silicon-refinement process. The silicon production industry is large, highly segmented by refining step, and multifaceted in terms of final product type, from which we conclude that production of Si-32-mitigated crystals requires both targeted silicon material selection and a dedicated refinement-through-crystal-production process. We review options for source material selection, including quartz from an underground source and silicon isotopically reduced in Si-32. To quantitatively evaluate the Si-32 content in silicon metal and precursor materials, we propose analytic methods employing chemical processing and radiometric measurements. Ultimately, it appears feasible to produce silicon-based detectors with low levels of Si-32, though significant assay method development is required to validate this claim and thereby enable a quality assurance program during an actual controlled silicon-detector production cycle.

Authors:
; ; ORCiD logo; ORCiD logo;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1422285
Report Number(s):
PNNL-SA-127795
Journal ID: ISSN 0927-6505
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astroparticle Physics; Journal Volume: 99; Journal Issue: C
Country of Publication:
United States
Language:
English
Subject:
dark matter; direct detection; silicon; assay

Citation Formats

Orrell, John L., Arnquist, Isaac J., Bliss, Mary, Bunker, Raymond, and Finch, Zachary S. Naturally occurring 32 Si and low-background silicon dark matter detectors. United States: N. p., 2018. Web. doi:10.1016/j.astropartphys.2018.02.005.
Orrell, John L., Arnquist, Isaac J., Bliss, Mary, Bunker, Raymond, & Finch, Zachary S. Naturally occurring 32 Si and low-background silicon dark matter detectors. United States. doi:10.1016/j.astropartphys.2018.02.005.
Orrell, John L., Arnquist, Isaac J., Bliss, Mary, Bunker, Raymond, and Finch, Zachary S. Tue . "Naturally occurring 32 Si and low-background silicon dark matter detectors". United States. doi:10.1016/j.astropartphys.2018.02.005.
@article{osti_1422285,
title = {Naturally occurring 32 Si and low-background silicon dark matter detectors},
author = {Orrell, John L. and Arnquist, Isaac J. and Bliss, Mary and Bunker, Raymond and Finch, Zachary S.},
abstractNote = {The naturally occurring radioisotope Si-32 represents a potentially limiting background in future dark matter direct-detection experiments. We investigate sources of Si-32 and the vectors by which it comes to reside in silicon crystals used for fabrication of radiation detectors. We infer that the Si-32 concentration in commercial single-crystal silicon is likely variable, dependent upon the specific geologic and hydrologic history of the source (or sources) of silicon “ore” and the details of the silicon-refinement process. The silicon production industry is large, highly segmented by refining step, and multifaceted in terms of final product type, from which we conclude that production of Si-32-mitigated crystals requires both targeted silicon material selection and a dedicated refinement-through-crystal-production process. We review options for source material selection, including quartz from an underground source and silicon isotopically reduced in Si-32. To quantitatively evaluate the Si-32 content in silicon metal and precursor materials, we propose analytic methods employing chemical processing and radiometric measurements. Ultimately, it appears feasible to produce silicon-based detectors with low levels of Si-32, though significant assay method development is required to validate this claim and thereby enable a quality assurance program during an actual controlled silicon-detector production cycle.},
doi = {10.1016/j.astropartphys.2018.02.005},
journal = {Astroparticle Physics},
number = C,
volume = 99,
place = {United States},
year = {Tue May 01 00:00:00 EDT 2018},
month = {Tue May 01 00:00:00 EDT 2018}
}