Estimation of low energy neutron flux ($E_n\leq15$ MeV) in India-based Neutrino Observatory cavern using Monte Carlo techniques

TL;DR

This study estimates the low-energy neutron flux in the India-based Neutrino Observatory cavern using Monte Carlo simulations, considering rock radioactivity, and finds flux levels comparable to other underground labs.

Contribution

It provides a detailed Monte Carlo based estimation of neutron flux from rock radioactivity specific to the India-based Neutrino Observatory.

Findings

Neutron flux at the center of the tunnel is approximately 2.76 x 10^{-6} n/cm^2/s.

Neutron flux levels are similar to those observed in other underground laboratories.

The flux is modeled considering a finite cylindrical rock volume of 140 cm dimensions.

Abstract

The neutron flux at low energy ($E_n\leq15$ MeV) resulting from the radioactivity of the rock in the underground cavern of the India-based Neutrino Observatory is estimated using Geant4-based Monte Carlo simulations. The neutron production rate due to the spontaneous fission of $^{235, 238}$U, $^{232}$Th and ($\alpha, n$) interactions in the rock is determined employing the actual rock composition. It is been shown that the total flux is equivalent to a finite size cylindrical rock ($D=L=140$ cm) element. The energy integrated neutron flux thus obtained at the centre of the underground tunnel is 2.76 (0.47) $\times 10^{-6}\rm~n ~cm^{-2}~s^{-1}$. The estimated neutron flux is of the same order ($\sim10^{-6}\rm~n ~cm^{-2}~s^{-1}$)~as measured in other underground laboratories.