Cosmogenic activation of sodium iodide

Abstract

The production of radioactive isotopes by interactions of cosmic-ray particles with sodium iodide (NaI) crystals can produce radioactive backgrounds in detectors used to search for rare events. Through controlled irradiation of NaI crystals with a neutron beam that matches the cosmic-ray neutron spectrum, followed by direct counting and fitting the resulting spectrum across a broad range of energies, we determined the integrated production rate of several long-lived radioisotopes. The measurements were then extrapolated to determine the sea-level cosmogenic neutron activation rate, including the first experimental determination of the tritium production rate: $(80\pm 21)$ atoms/kg/day. These results will help constrain background estimates and determine the maximum time that NaI-based detectors can remain unshielded above ground before cosmogenic backgrounds impact the sensitivity of next-generation experiments.

arXiv comment20 pages, 15 figures, 7 tables

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Cited by in corpus (3)

• Simulation and background characterisation of the SABRE South experiment
• Study of cosmogenic activation above ground for the DarkSide-20k experiment
• Removal of spallation-induced tritium from silicon through diffusion