Estimation of neutron flux in TIFR Low background Experimental Setup (TiLES)

In rare event studies like neutrinoless double beta decay (0υββ), dark matter search etc., minimizing the background is very important. Neutron induced background can be a limiting source of the background in such studies, since neutrons are most difficult to suppress. It is therefore crucial to measure neutron flux in the low background experimental setups. The ambient neutron background at sea level arises from the spontaneous fission of Uranium and Thorium isotopes as well as from (α, n) nuclear reactions. In addition, the cosmic muon interactions in high Z shielding materials, used for reducing γ background, act as a strong neutron source. They can produce neutrons in many ways like spallation reactions, photonuclear reactions, muon capture etc. Subsequently, these neutrons can interact with the detector and shielding materials, giving rise to enhanced γ-ray background. In this work, we estimate the thermal and fast neutron flux incident upon the TiLES HPGe detector from the intensity of spectral lines arising from ⁷⁴ Ge(n, γ)^75mGe and ⁷²Ge(n,n⁰ )⁷²Ge reactions, respectively