It is known that ultracold neutrons (UCN) were first observed by Shapiro’s group in an experiment performed on an IBR reactor with an average power of 6 kW. Currently, UCN sources are available or are being constructed in a large number of scientific centers in Europe and America. Unfortunately, Dubna is not among them. The reason for this is clear. A pulse reactor with a megawatt average power at a repetition rate of several pulsed per second does not seem very suitable for this purpose. Its average power is relatively small to create a stationary source, and the repetition rate is too high to accumulate in the trap all the neutrons born in a single pulse. A possible solution to the problem may be to use a combination of a storage trap with a pulse valve, and a time lens that forms a time image of the neutron pulse of the source at the entrance to the trap.

The results of our analysis indicate that a UCN source based on this principle can be created both at the IBR2 M reactor and at the DNS IV reactor under design. The parameters of such a source allow it to take a very worthy place among the world’s sources of UCN.