Development of an underground low background instrument for high sensitivity measurements

Abstract

The Center for Underground Physics has developed in collaboration with CANBERRA a low background instrument composed of 14 HPGe detectors divided in two arrays facing each other. The performance and the background of a single detector of the array have been studied in order to improve the array final configuration. An accurate material selection, through the measurements of building material samples and Monte Carlo simulations based on Geant4, has been performed to reach the lowest possible intrinsic background. Alternative materials and configurations have been considered for the final design of the array simulating the expected intrinsic background of the instrument considering the needed changes. The expected sensitivity of the improved array configuration, concerning the low background material selection for rare events physics experiments, has been evaluated through Monte Carlo simulations considering 232Th concentration in a Copper sample. Since the array can also be used for rare decays searches, the expected sensitivity on the 156Dy resonant double electron capture has thus been calculated.