   |
|||||||||||
|
|
|
 Main Scientific Directions developed in the Frank Laboratory of Neutron Physics. By getting control over nuclear energy, neutron physics has seemingly accomplished the main task of its evolution. In reality, scientific foundation for nuclear power engineering is only one of the directions of neutron physics. Simultaneously with the development of reactor technology, thorough investigations of neutron properties, applications of neutrons to study properties of nuclei ?{ neutron resonances, properties of nuclear matter at high excitation energies have become possible. There is no other way to excite nuclei having width of a fraction of electronvolt and lying in the range of excitation energies of several million electronvolts. The development of pulsed neutron sources has given rise to a new field in nuclear physics ?{ neutron nuclear spectroscopy. The use of pulsed reactors of the IBR type has proved to be very promising for work with slow neutrons in studying rare reactions. The use of a booster mode (coupling of the IBR reactor with an electron accelerator) has made it possible to advance in spectroscopic research up to the neutron energies of tens of keV and to carry out important investigations of properties of atomic nuclei. In FLNP for the first time in the world the neutron polarization method consisting in passing neutrons through a polarized proton target has been developed, allowing polarized neutrons to be obtained in a wide energy interval up to several tens of kiloelectronvolts. A series of extensive studies of the dependence of properties of neutron resonances on their spin have been conducted on a polarized neutron beam. The neutron spectroscopy methods have been used to detect extraordinary fine effects in the properties of nuclei and in the peculiarities of their interactions with neutrons: determination of magnetic moments of highly excited states of nuclei, determination of values of chemical shifts of neutron resonances and of spatial parity violation effects in neutron resonances, ?{ it has been the specialists of the Laboratory of Neutron Physics who carried out these pioneer investigations. The discovery of ultracold neutrons (UCN) by FLNP scientists has led not only to the creation of a scientific direction for studying their properties, which is now being actively developed all over the world, but also has resulted in setting up unique experiments to measure neutron lifetime and to estimate its electric dipole moment. On the IBR reactors condensed matter investigations have been successfully developing. The observation of inelastic neutron scattering is an effective method to study properties of liquids and solids. The inverted geometry method (in fact, applied for the first time in FLNP) in combination with the pulsed neutron sources proved to be especially efficient. Neutronography methods of studying properties of matter lean upon properties of the neutron as an elementary particle, of which the most important are zero electric charge, rest mass, rather strong interaction with atomic nuclei and its dependence on the type of isotope of the same element and large magnetic moment. The combination of these properties makes neutrons a deeply penetrating kind of radiation, whose wave properties can be chosen adequate to the sizes of objects under study. Throughout the past years the investigations on neutron-structural analysis using the neutron diffraction method have been developing. Much consideration has been given to the studies of magnetic properties of different materials, and the investigations of high-temperature and other systems with strong electron correlations are continued intensively. In FLNP pioneer investigations by the small-angle neutron scattering method especially of biological objects, self-organizing systems and microscopic thermodynamic characteristics have been successfully evolving. Neutronography methods make it possible to study dynamic processes in biological systems (diffusion of molecules, segment mobility, longitudinal and lateral vibrations of polypeptide chains, etc.). On the pulsed neutron sources in FLNP the research activities are focused on the following topics:
• Neutron spectroscopy
• Thermal neutron spectroscopy
• Nuclear reactions
• Activation analysis and ecological studies |
