Neutron physics investigations of fundamental processes of statistical mechanics

Abstract

Studies in spin dynamics of disordered media and multiple ultra-small angle neutron scattering are considered. The experiments were carried out on unique installations designed in ITEP laboratory of neutron physics: beta-NMR spectrometer and universal neutron diffractometer. The main attention is paid to random walks in disordered systems and ultra-small angle neutron scattering (USANS) on objects with space correlations in positions of scatterers. Synthesis of concentration expansion, semi-phenomenological theory and numerical simulations produced satisfactory description of the nuclear polarization transfer within disordered 8Li–6Li spin subsystem in LiF single crystal. The theory of USANS starts from eikonal approximation for the scattering amplitude, which (a) reproduces the phenomenological Moliere–Bethe theory for the observable neutron angular distributions for uncorrelated random positions of scatterers, and (b) gives a possibility to take into account their spatial correlations.