SAPPHIRE-ANVIL CELLS FOR NEUTRON SCATTERING STUDIES AT HIGH PRESSURES. A.S. Ivanov, Russian Research Center "Kurchatov Institute", Moscow 123182, RUSSIA

Recent progress on instrumentation for neutron scattering investigations of condensed matter at high pressures is reported. A set of high-pressure cells with maximal load up to 25 tons and ancillary equipment was constructed to conduct measurements of crystal structure and lattice dynamics at pressures of few dozens kbar and at different temperatures with sample volumes up to few cubic millimeters. Different size anvils (as a rule sapphire and sometimes diamond) in combination with various metallic gaskets serve to clamp a powder sample or a single crystal in liquid pressure-transmitting medium. A new type time-of-flight neutron scattering instrument with a full Debye-cone analysis was created and installed at the pulsed reactor in collaboration with Joint Institute for Nuclear Research, Dubna, Moscow Region. The instrument is dedicated to studies of microsamples and is adopted to measurements of both elastic and inelastic (using analyser ring) neutron scattering. The working abilities of the equipment are illustrated by examples of neutron scattering spectra registered at a number of fixed pressure values in the studied pressure range. The examples include measurements of pressure changes of crystal structure in ammonium halides and different mercury superconductors. Some data on phonon density of states, phonon dispersion and small-angle scattering are presented.