University of Oulu

Measuring the ¹⁴C content in liquid scintillators

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Author: Aittola, Marko1; Enqvist, Timo1; Bezrukov, L. B.2;
Organizations: 1Oulu Southern Institute and Department of Physics, University of Oulu, Finland
2Russian Academy of Sciences, Institute of Nuclear Research, Moscow, Russia
3Department of Physics, University of Jyväskylä, Finland
Format: abstract
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 0.3 MB)
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Language: English
Published: University of Helsinki, 2015
Publish Date: 2017-01-10


In order to detect low-energy neutrinos, for example the solar neutrinos from the ppchain (with the maximum neutrino energy of approximately 400 keV) requires that the intrinsic ¹⁴C content in a liquid scintillator is at extremely low level. In the Borexino detector, a 300-ton liquid scintillation detector at Gran Sasso, Italy, the ratio of ¹⁴C to ¹²C of approximately 2 × 10⁻¹⁸ has been achieved. It is the lowest value ever measured. The detector situates underground at the depth of 3200 mwe (1200 m).

¹⁴C cannot be removed from liquid scintillators by chemical methods, or by other methods in large quantities (liters). In principle, the older is the oil or gas source that the liquid scintillator is made of and the deeper it situates, the smaller should be the ¹⁴C-to-¹²C ratio. This, however, is not generally the case, and the ratio depends on the activity (U and Th content) in the environment of the source.

We have started a series of measurements where the ¹⁴C-to-¹²C ratio will be measured from liquid scintillator samples. The measurements take place in two underground laboratories: in the Pyhäsalmi mine, Finland, at the depth of 4000 mwe (1400 meters) and at the Baksan Underground Laboratory, Russia at 4800 mwe, for reducing and better understanding systematical uncertainties. There will be about ten samples with the known origin, each of them 2 litres. The liquid scintillator vessel, light quides and low-active PMTs will be shielded with thick layers copper and lead. Nitrogen flow is used to reduce the radon background.

The aim is to measure ratios smaller than 10⁻¹⁸, if such samples exists. One measurement takes several weeks.

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Series: Report series in physics
ISSN: 0355-5801
ISSN-L: 0355-5801
ISBN: 978-951-51-0584-4
Issue: HU-P-268
Pages: 237 - 237
Host publication: Proceedings of the XLIX annual conference of the Finnish physical society
Host publication editor: Tenkanen, Tommi
Conference: Physics days / fysiikan päivät : annual meeting of the Finnish physical society
Field of Science: 215 Chemical engineering
Copyright information: Published in this repository with the kind permission of the publisher.