Eur. Phys. J. Plus (2021) 136: 882
https://doi.org/10.1140/epjp/s13360-021-01740-1

Regular Article

Compact ultracold neutron source concept for low-energy accelerator-driven neutron sources

¹ Center for Axion and Precision Physics Research, IBS, 193 Munji-Ro, 34051, Daejeon, South Korea
² Department of Physics, Indiana University, 727 E. Third St., 47405, Bloomington, IN, USA
³ Center for Exploration of Energy and Matter, 2401 Milo B. Samson Lane, 47408, Bloomington, IN, USA
⁴ Department of Physics, KAIST, 291 Daehak-Ro, 34141, Daejeon, South Korea

^a yunshin@ibs.re.kr

Received: 17 February 2021
Accepted: 9 July 2021
Published online: 26 August 2021

Abstract

The concept of a small-scale, pulsed-proton accelerator-based compact ultracold neutron (UCN) source is presented. The essential idea of the compact UCN source is to enclose a volume of superfluid ${}^4\text{He}$ converter with a supercold moderator in the vicinity of a low-radiation neutron production target from (p, n) reactions. The supercold moderator should possess an ability to produce cold neutron flux with a peak brightness near the single-phonon excitation band of the superfluid ${}^4\text{He}$ converter, thereby augmenting the UCN production in the compact UCN source even with very low intensity of neutron brightness. The performance of the compact UCN source is studied in terms of the UCN production and thermal load in the UCN converter. With the proposed concept of the compact UCN source, a UCN production rate of $P_{\mathrm{UCN}}=80{\text{UCN/cm}}^3/\text{s}$ in the UCN converter could be obtained while maintaining thermal load of the superfluid ${}^4\text{He}$ and its container at a level of $22\text{mW}$. This study shows that the compact UCN source can produce a high enough density of UCNs at a small-scale, low-energy, pulsed-proton beam facility with reduced efforts on the cooling and radiation protection.