Neutron lifetime measurement with the big gravitational trap for ultracold neutrons. Current state and future prospects.

International audienceA new measurement of the neutron lifetime, carried out with the aid of a large gravitational spectrometer made in Petersburg Institute of Nuclear Physics (PNPI) is presented: τn = 881.5 ± 0.7 ± 0.6 s. In our experiment the measurement of neutron lifetime is carried out using the method of storing ultracold neutrons in a material trap with gravitational barrier. Further improvement of the obtained result can be achieved at the helium temperatures. Here we present our neutron lifetime result, modified installation scheme and the first results of cryogenic tests are discussed