UCN sources at external beams of thermal neutrons. An example of PIK reactor

We estimate parameters of 4He source with solid methane (CH4) or/and liquid deuterium (D2) moderator-reflector. We show that such a source with CH4 moderator-reflector at the PIK reactor would provide the UCN density of ~1·105 cm−3, and the UCN production rate of ~2·107 s−1. These values are respectively 1000 and 20 times larger than those for the most intense UCN user source. The UCN density in a source with D2 moderator-reflector would reach the value of ~2·105 cm−3, and the UCN production rate would be equal ~8·107 s−1. Installation of such a source in a beam of CNs would slightly increase the density and production rate.