University of Oulu

Concentration of 14C in liquid scintillator

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Author: Enqvist, Timo1; Barabanov, I. R.2; 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: Oulu : University of Oulu, 2016
Publish Date: 2017-01-09


The main background hindering low-energy (≲ 200 keV) neutrino measurements with liquid scintillators comes from the minute remanence of the cosmogenic 14C (T1/2 ≃ 5700 a) present in the organic oil constituting the bulk of the scintillator. The β-decay endpoint energy of 14C is quite low, Q = 156 keV, and the counting rate from 14C is often reduced by threshold settings. However, too high concentration of 14C may results in pile-up pulses. For example, in the Borexino detector at Gran Sasso, Italy, being the most sensitive neutrino detector, the trigger rate is largely dominated by the 14C isotope [1] with the concentration of 2 × 10-18 [2]

It is the lowest 14C concentration value ever measured. There are only a few results available on the 14C concentration. In addition to the one in Ref. [2] there are three other measurements reported in Refs. [3, 4, 5].

Obviously 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 the 14C concentration should be. This, however, is not generally the case and it is believed that the ratio depends on the activity (U and Th content) in the environment of the source.

We are performing a series of measurements where the 14C concentration will be measured from several liquid scintillator samples. They need low-background environment and are taking place in two deep underground laboratories: in the new CallioLab laboratory in the Pyhäsalmi mine, Finland, and at the Baksan Neutrino Observatory, Russia, in order to reduce and better understand the systematical uncertainties. Preliminary results will be presented.

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Series: Report series in physical sciences
ISSN: 1239-4327
ISSN-L: 1239-4327
ISBN: 978-952-62-1145-9
Pages: 230 - 230
Licence condition: Published in this repository with the kind permission of the publisher.