We report a direct detection of muon-induced high energy neutrons with a 12-liter neutron detector fabricated with EJ-301 liquid scintillator operating at Soudan Mine for about two years. The detector response to energy from a few MeV up to ∼ 20 MeV has been calibrated using radioactive sources and cosmic-ray muons. Subsequently, we have calculated the scintillation efficiency for nuclear recoils, up to a few hundred MeV, using Birks' law in the Monte Carlo simulation. Data from an exposure of 655.1 days were analyzed and neutron-induced recoil events were observed in the energy region from 4 MeV to 50 MeV, corresponding to fast neutrons with kinetic energy up to a few hundred MeV, depending on the scattering angle. Combining with the Monte Carlo simulation, the muon-induced fast neutron flux is determined to be (2.3±0.52(sta.)±0.99(sys.))×10−9 cm−2s−1 (En> 20 MeV), in a reasonable agreement with the model prediction. The muon flux is found to be (1.65±0.02(sta.)±0.1(sys.))×10−7 cm−2s−1 (Eμ> 1 GeV), consistent with other measurements. As a result, the muon-induced high energy gamma-ray flux is simulated to be 7.08 ×10−7cm−2s−1 (Eγ> 1 MeV) for the depth of Soudan.
@article{arxiv.1407.3246,
title = {Measuring Muon-Induced Neutrons with Liquid Scintillation Detector at Soudan Mine},
author = {C. Zhang and D. -M. Mei},
journal= {arXiv preprint arXiv:1407.3246},
year = {2014}
}