Neutron flux measurement at the Baksan Underground Scintillation Telescope

Abstract

The characteristics of fast neutrons produced by cosmic-ray muons at the Baksan Underground Scintillation Telescope (BUST) are investigated. A novel approach to the problem consists in estimating the neutron flux by the production rate of the unstable radioactive nuclide 12B in the (n, p) reaction on carbon nuclei of the BUST organic scintillator. The processing of the data collected in 2002–2015 yielded $${N_{{{12}_B}}} = 337 \pm 2.5$$ events consistent with those of the reaction 12C(n, p)12B. For the BUST internal planes, the background of fast neutrons with E > 28.6 MeV is experimentally estimated as Φ ∝ 10−11cm–2 s–1. This is lower than the theoretically predicted total neutron flux by nearly two orders of magnitude. The disagreement with predictions is attributed to the suppression of neutron flux in the external scintillator planes of the detector.