Speaker
Description
The control of intrinsic radioactivity, surface contamination and detector-induced backgrounds is an important requirement for rare-event searches and for precision nuclear measurements performed in underground laboratories. GAIAS (GAxIal Analysis with Scintillators) is an experimental programme at the Gran Sasso National Laboratory (LNGS) aimed at exploiting radiopure crystal scintillators as active sources and detectors for high-precision beta-spectral-shape measurements of forbidden non-unique transitions. The same experimental strategy also provides a demanding test bench for low-background scintillator development, material selection and response modelling.
GAIAS focuses on crystals containing beta-emitting isotopes either intrinsically or through controlled incorporation, including CdWO4, CsI-based and NaI-based scintillators, and other candidate materials of interest for low-radioactivity applications. In this approach, the source is embedded in the active detector volume, reducing geometrical uncertainties and enabling high statistics under stable operating conditions. Particular attention is devoted to crystal radiopurity, residual contamination from growth and handling, scintillation non-proportionality at low energy, threshold stability, and the identification and suppression of external gamma, neutron and cosmogenic backgrounds.
The programme combines underground operation at LNGS, dedicated low-background assay, optimised scintillation readout, calibration and stability studies, and Monte Carlo simulations of detector response and background components. These elements are essential for reconstructing beta spectra with controlled systematic uncertainties, especially in the low-energy region where forbidden spectral shapes are most sensitive to nuclear weak-interaction effects. Measurements of isotopes such as 113Cd, 113mCd, 87Rb and 99Tc are being considered as benchmarks for the extraction of information on the effective axial-vector coupling in nuclei and for validating nuclear-structure calculations relevant to neutrinoless double beta decay and neutrino-nucleus interactions.
Within the scope of Low Radioactivity Techniques, GAIAS therefore connects material radiopurity, crystal scintillator performance and background modelling to a broader physics goal: using low-background detectors not only to suppress rare-event backgrounds, but also as precision instruments for nuclear beta spectroscopy. The results are expected to support the development of radiopure scintillating materials, improve response models for crystal detectors and provide new experimental constraints on nuclear weak processes.