Rotating Magnetic Gravitational Trap for Storing Ultracold Neutrons

The paper proposes an experiment to measure the neutron lifetime by storing ultracold neutrons in a rotating magnetic trap. The magnetic trap is a set of NdFeB permanent magnets. By rotating the trap around a horizontal axis, it is possible to carry out the gravitational capture of ultracold neutrons and their holding. A design option is presented when two traps are located in one installation on the same axis: material and magnetic. The sensitivity of the magnetic trap is assessed in comparison with the material one under equal measurement conditions. One of the factors influencing the systematic error of the experiment will be the process of neutron depolarization in a magnetic field. Therefore, the paper considers the issue of developing a magnetic system that minimizes the probability of neutron depolarization. The so-called turbine effect is also considered, which can manifest itself in a change in the energy of ultracold neutrons during rotation due to interaction with the flat faces of the trap. The proposed gravitational capture of ultracold neutrons in a magnetic trap is a fundamentally new approach that has never been implemented before. The experiment can be carried out on the ultracold neutron source under construction at the PIK reactor.