ACCESS · Array of Cryogenic Calorimeters to Evaluate Spectral Shapes

ACCESS aims to establish a new technique to perform precision measurements of forbidden beta-decays, whose spectral shape is a crucial benchmark for Nuclear Physics calculations and plays a pivotal role in Astroparticle Physics experiments. When fundamental conservation laws strongly suppress a beta decay, it features a high transferred momentum, as in the case of neutrinoless double-beta decay (NLDBD). Relying on this similarity, ACCESS will provide groundbreaking insights to evaluate Nuclear Matrix Elements for NLDBD. ACCESS will operate a pilot array of four tellurium dioxide crystals as cryogenic calorimeters. Three of them will be doped with different beta emitters, while the last natural one will be used for effective background subtraction. My experience with cryogenic calorimeters based on semiconductor sensors (i.e. NTD) will be a solid basement for the project, but an essential piece of the puzzle is still missing. ACCESS requires high statistical measurements in an ultra-clean underground cryostat, available for limited time slots. A fast detector is mandatory to collect the required number of signals, keeping the background low, and avoiding the pileup due to the high counting rate. To fulfill this requirement, I will complete my training during the first two years of the action at Queen’s University. Here I will learn to build and operate bolometers based on superconductive sensors (i.e. TES), among the faster sensors used in Astroparticle Physics. I will transfer my NTD-oriented expertise to the local group, and together we will integrate these two sensors for a novel application. In the last year, I will move to GSSI, a research center of excellence recently established in Italy. Here I will perform the final measurements at LNGS (Gran Sasso National Laboratory), a world-leading underground research infrastructure of INFN. My new skills and research network will enrich the local astroparticle group, extending its research field also to Nuclear Physics.