Neutron transport analysis of ultracold neutron production in superfluid helium

A preliminary analysis is made of ultracold neutron (UCN) production in liquid 4He for incident neutrons with an energy of about 1 meV. By the use of a cross-section model developed for the cold-neutron scattering in liquid 4He, a set of multigroup constants for several different temperatures is generated. A multigroup neutron transport analysis is applied to a one-dimensional slab model for a UCN source. The enhancement of UCN production for superfluid 4He at lower temperatures below 2.172 K is shown, which enables us to proceed to further neutron transport analysis of UCN production and storage.