Background Measurements in the Gran Sasso Underground Laboratory

TL;DR

This study measures gamma and neutron background fluxes at various locations in the Gran Sasso underground laboratory, providing data crucial for low-background experiments and understanding underground radiation sources.

Contribution

It offers detailed measurements of gamma and neutron backgrounds at multiple underground sites and uses Monte Carlo simulations to identify isotope contributions, enhancing background modeling.

Findings

Gamma flux is 0.3-0.4 s$^{-1}$cm$^{-2}$ in halls, much lower inside LVD.

Neutron flux measurements agree with other underground neutron data.

Monte Carlo simulations help identify isotope contributions to background.

Abstract

The gamma background flux below 3000 keV in the Laboratori Nazionali del Gran Sasso (LNGS), Italy, has been measured using a 3" diameter NaI(Tl) detector at different underground positions: In hall A, hall B, the interferometer tunnel, and inside the Large Volume Detector (LVD). The integrated flux is 0.3--0.4 s$^{-1}$cm$^{-2}$ at the first three locations, and is lower by two orders of magnitude inside LVD. With the help of Monte Carlo simulations for every location, the contribution of the individual primordial isotopes to the background has been determined. Using an 11" diameter NaI(Tl) detector, the background neutron flux in the LNGS interferometer tunnel has been estimated. Within the uncertainties, the result agrees with those from other neutron measurements in the main halls.