Background Measurements in the Gran Sasso Underground Laboratory

Understand

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.