Evaluation of Neutron Storage Time in Closed Chamber of the UCN Source for PIK Reactor

In 2020, a Federal Program for creating experimental facilities for the PIK reactor was started. One of the main facilities to be constructed within this Program is a new superfluid helium-based UCN source for fundamental physics research. The projected UCN density in the closed source vessel is going to be 2.1 × 103 cm–3. Work has been carried out for increasing UCN density in the source vessel by increasing neutron lifetime in superfluid helium. More than 40 m3 of isotopically pure helium-4 with a helium-3 content below 10–11 was produced to virtually eliminate the possibility of neutron absorption. Cryogenic cycle was optimised to obtain minimum helium temperature in the chamber. Work is underway to assemble the entire complex for cryogenic system testing and confirm the operating parameters of the facility.