Speaker
Description
The precise characterization of environmental gamma-ray radiation in underground laboratories, and of its dependence on radon activity, is fundamental for the next generation of rare-event search experiments. In this contribution, we present a measurement campaign performed in Hall C of the Gran Sasso National Laboratory using a portable setup in which a high-purity germanium detector and a radon monitor were mounted on a movable cart, together with the electronics and data acquisition system needed for field operation. The setup was deployed at several locations in the hall to map the gamma-ray radiation field and study its correlation with the radon concentration in air. The detector response and full-energy-peak efficiencies were determined through Geant4 simulations validated with calibrated gamma-ray sources, allowing an efficiency-corrected evaluation of the gamma-ray flux. A clear correlation is observed between the gamma-ray rate and the radon activity, consistent with the contribution of short-lived radon progeny. This work provides insight into time-dependent environmental backgrounds at LNGS and represents a first step toward a systematic mapping of gamma-ray flux and radon-induced variations throughout the underground laboratory.