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arXiv · 2209.14898

Cosmogenic activation of sodium iodide

R. Saldanha·W. G. Thompson·Y. Y. Zhong·L. J. Bignell·R. H. M. Tsang·S. J. Hollick·S. R. Elliott·G. J. Lane·R. H. Maruyama·L. Yang
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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.

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R. Saldanha, W. G. Thompson, Y. Y. Zhong, L. J. Bignell, R. H. M. Tsang, S. J. Hollick, S. R. Elliott, G. J. Lane, R. H. Maruyama, L. Yang. 2022-09-29. Cosmogenic activation of sodium iodide. https://doi.org/10.1103/physrevd.107.022006

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