Monte Carlo simulation of the nonstationary transport of very cold and ultracold neutrons in vertical neutron guides and the storage of ultracold neutrons

The results are presented of Monte Carlo simulation of the transport of very cold (VCN) and ultracold neutrons (UCN) in straight and curved vertical neutron guides with a rectangular cross section in the presence of neutron losses due to neutron capture and diffuse scattering on imperfectly smooth reflecting surface of the guides wall. The gravitational neutron deceleration and bending of neutron trajectories are rigorously taken into account. The nonstationary storage of UCN in experimental chambers is modelled for a low periodic or a periodic pulse neutron source.