  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 $^{4}\mathrm{He}$ 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 $^{4}\mathrm{He}$ 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 $P_{\mathrm{UCN}}=80\mathrm{UCN}/\mathrm{cc}/\mathrm{sec}$
in the UCN converter could be obtained while maintaining thermal load of on the
superfluid $^{4}\mathrm{He}$ and its container at a level of $22\mathrm{mW}$.
This study shows that the compact UCN source can produce a high enough density
of UCN at a small-scale, low-energy, pulsed-proton beam facility with reduced
efforts on the cooling and radiation protection.
