It is known that neutron background is a big problem for low-background experiments in underground Laboratories. Our global net of en-detectors sensitive to thermal neutrons includes the detectors running both on the surface and at different depths underground. We present here results obtained with the en-detector of 0.75 m^2 which is running more than 3 years in underground room at a depth of 25 m of water equivalent in Skobeltsyn Institute of Nuclear Physics, Moscow. Spontaneous increases in thermal neutron flux up to a factor of 3 were observed in delayed anti-correlation with barometric pressure. The phenomenon can be explained by a radon barometric pumping effect resulting in similar effect in neutron flux produced in (alpha,n)-reactions by alpha-decays of radon and its daughters in surrounding rock
@article{arxiv.1605.01283,
title = {Barometric pumping effect for radon-due neutron flux in underground laboratories},
author = {Yu. V. Stenkin and V. V. Alekseenko and D. M. Gromushkin and O. B. Shchegolev and V. P. Sulakov},
journal= {arXiv preprint arXiv:1605.01283},
year = {2016}
}