Cosmogenic activation of a natural tellurium target

Abstract

130Te is one of the candidates for the search for neutrinoless double beta decay. It is currently planned to be used in two experiments: CUORE and SNO+. In the CUORE experiment TeO2 crystals cooled at cryogenic temperatures will be used. In the SNO+ experiment natTe will be deployed up to 0.3% loading in the liquid scintillator volume. A possible background for the signal searched for, are the high Q-value, long-lived isotopes, produced by cosmogenic neutron and proton spallation reaction on the target material. A total of 18 isotopes with Q-value larger than 2 MeV and T1/2 >20 days have been identified as potential backgrounds. In addition low Q-value, high rate isotopes can be problematic due to pile-up effects, specially in liquid scintillator based detectors. Production rates have been calculated using the ACTIVIA program, the TENDL library, and the cosmogenic neutron and proton flux parametrization at sea level from Armstrong and Gehrels for both long and short lived isotopes. The obtained values for the cross sections are compared with the existing experimental data and calculations. Good agreement has been generally found. The results have been applied to the SNO+ experiment for one year of exposure at sea level. Two possible cases have been considered: a two years of cooling down period deep underground, or a first purification on surface and 6 months of cooling down deep underground. Deep underground activation at the SNOLAB location has been considered

Cosmogenic activation of materials

“…As shown in the excitation functions plotted in Ref. 81 for 110m Ag and 60 Co, the measured cross sections above 800 MeV agree reasonably well with predictions of ACTIVIA; the origin of the difference can be at lower energies (the region giving the dominant contribution to the production rates). The different cosmic neutron spectra considered in the two works makes difficult also the comparison.…”

“…), was analyzed in Ref. 81. For long-lived isotopes, the underground activation was estimated to be less than 1 event/(y t).…”

“…81, production rates of cosmogenic-induced isotopes on a natural tellurium target were calculated using the ACTIVIA program for energies above 100 MeV, the neutron and proton cross sections from TENDL library in the 10-200 MeV range when available, and the cosmogenic neutron and proton flux parametrization at sea level from Armstrong 39 and Gehrels.…”

Cosmogenic activation of materials

“…Production rates (in µBq kg −1 ) at sea level presented in Ref 79. for isotopes induced in TeO 2 combining measured cross sections at different energies and in Ref 81. for natural tellurium using ACTIVIA and TENDL library.…”

Neutrino Physics with SNO+

“…The purification system for the surfactant and the telluric acid is currently under development. A detailed study of the production of possible backgrounds by cosmogenic activation on Tellurium [3] showed that a purification factor of 10 4 followed by a 3 to 6 months cool-down is needed for the telluric acid. This will be achieved by a 2-stage re-crystallization purification procedure.…”