Cosmogenic activation of TeO2 in the neutrinoless double-beta decay experiment CUORE

by Barbara Wang

Thursday 14 Nov 2013, 12:30 → 13:30 US/Pacific

SLAC

The Cryogenic Underground Observatory for Rare Events (CUORE) is an experiment that will search for the neutrinoless double-beta (0nubb) decay of ¹³⁰Te. The CUORE detector, currently being constructed underground at the Gran Sasso National Laboratory in Italy, is an array of 988 high-resolution, low-background cryogenic bolometers. Each bolometer is comprised of a thermal sensor and a TeO₂ crystal that serves as both a source and a detector of 0nubb decay. The 0nubb decay signature for ¹³⁰Te is a peak at the Q-value 2528 keV. Observation of 0nubb decay requires that the background rate at the peak be ultra-low; CUORE is aiming for a rate less than 0.01 counts/keV/kg/y. Background-source identification and characterization are therefore extremely important.

One source of background that is poorly characterized is activation of the TeO₂ crystals by sea-level cosmic-ray neutrons. This process, known as cosmogenic activation, produces long-lived radioisotopes that can obscure the 0nubb decay peak.  Existing cross-section data is insufficient to estimate this background; therefore an additional cross-section measurement has been performed in which a TeO₂ target is irradiated with a neutron spectrum similar to that of cosmic-ray neutrons at sea-level. The cross-sections obtained have been combined with Monte Carlo simulations of the CUORE detector to estimate the cosmogenic activation background that will be present in CUORE.