ИСТИНА

Ultracold neutrons are neutrons that could be stored in material or magnetic traps. It was discovered in Frank Laboratory of Neutron Physics of Joint Institute for Nuclear Research (Dubna) at 1968 [1]. UCN is unique instrument for quantum mechanics study and fundamental physics. More precise experimental results were obtained for the neutron lifetime and the neutron electric dipole moment with ultracold neutrons [2, 3]. The study of possible systemic effects in these precision experiments requires a clear understanding of the physical processes at the neutron reflection from a surface. Some of the processes can lead to losses of neutrons from the traps. At the same time, experimentally measured losses are strongly exceed the theoretically predicted values for trap walls with small capture at low temperature [4]. The search for a source of additional losses led to the observation of a new (unpredictable) phenomenon. It is inelastic neutron scattering with a small energy transfer (about initial neutron energy). It was cold “small heating” of UCN [5]. The results of investigation of UCN “small heating” at solids and liquids will be presented in the talk. The set of experimental results allow to conclude that reason of UCN “small heating” at solids is neutron scattering by nanoparticles. This particles move permanently along the surfaces due to its thermal energy. At liquids, the phenomenon can be explained by neutron scattering at nanodroplets flying over the surface or viscoelastic capillary waves [6-8]. 1. V.I. Luschikov et al. JETP Lett. 9, 23 (1969) 2. S. Afach; et al.. Phys. Rev. D 92 (9): 092003 (2015) 3. A. P. Serebrov et al. Phys. Rev. C 78, 035505 4. V. P. Alfimenkov et al., JETP Lett. 55, 84 (1992) 5. V. V. Nesvizhevsky et al. Eur. Phys. J. AP 6, 151 (1999) 6. E.V.Lychagin et al. Physics of Atomic Nuclei, 65, (11), 1995 (2002) 7. D.G.Kartashov et al. International Journal of Nanoscience 6 (6) 501 (2007) 8. V. V. Nesvizhevsky et al. Crystallography Reports, 58, (5) 743 (2013)