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arXiv · 2302.03869

A portable and high intensity 24 keV neutron source based on $^{124}$Sb-$^{9}$Be photoneutrons and an iron filter

A. Biekert·C. Chang·L. Chaplinsky·C. W. Fink·W. D. Frey·M. Garcia-Sciveres·W. Guo·S. A. Hertel·X. Li·J. Lin·M. Lisovenko·R. Mahapatra·D. N. McKinsey·S. Mehrotra·N. Mirabolfathi·P. K. Patel·B. Penning·H. D. Pinckney·M. Reed·R. K. Romani·B. Sadoulet·R. J. Smith·P. Sorensen·B. Suerfu·A. Suzuki·V. Velan·G. Wang·Y. Wang·S. L. Watkins·M. R. Williams
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Abstract

A portable monoenergetic 24 keV neutron source based on the $^{124}$Sb-$^9$Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron energy from SbBe and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from $^{124}$Sb decays while letting through the neutrons. To increase the $^{124}$Sb activity and thus the neutron flux, a $>$1 GBq $^{124}$Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20-25 keV to be 5.36$\pm$0.20 neutrons per cm$^2$ per second and the total gamma flux to be 213$\pm$6 gammas per cm$^2$ per second (numbers scaled to 1 GBq activity of the $^{124}$Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.

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A. Biekert, C. Chang, L. Chaplinsky, C. W. Fink, W. D. Frey, M. Garcia-Sciveres, W. Guo, S. A. Hertel, X. Li, J. Lin, M. Lisovenko, R. Mahapatra, D. N. McKinsey, S. Mehrotra, N. Mirabolfathi, P. K. Patel, B. Penning, H. D. Pinckney, M. Reed, R. K. Romani, B. Sadoulet, R. J. Smith, P. Sorensen, B. Suerfu, A. Suzuki, V. Velan, G. Wang, Y. Wang, S. L. Watkins, M. R. Williams. 2023-02-08. A portable and high intensity 24 keV neutron source based on $^{124}$Sb-$^{9}$Be photoneutrons and an iron filter. https://doi.org/10.1088/1748-0221/18/07/p07018

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