Alexander Ilyich Leipunsky

Alexander Ilyich Leipunsky was a direct participant in the emergence of nuclear physics research in the USSR. He was one of the most respected experts in neutron physics, overcame many scientific and technical difficulties in the implementation of his ideas, devotedly devoted himself to his chosen scientific field. Companions of Alexander Ilyich in the IPPE, OKBM , OKB Gidropress , VNIINM , NIIAR , NIKIET , VNIPIET , SPbAEP and other organizations continue his work.

Alexander Ilyich Leipunsky was born on December 7, 1903 in the village of Dragli of the Sokolsky district of the Grodno province. His father, Ilya Isaakovich, worked as a foreman on the construction of highways. The father’s profession also explains the frequent relocations of the family (Sokolka, Bialystok, Aleksandrov, Rybinsk, Yaroslavl, etc.) During the First World War, the institutions of the Military Road Department where his father served were evacuated to Yaroslavl, where the whole Leipunsky family moved. The financial situation was difficult. My father worked on logging in the Yaroslavl province, a railway junction, and later, as O.I. Leipunsky , brother of the scientist, there was even a "seasonally unemployed." Children studied first at the gymnasium, then at the second-level school.

In 1926 he graduated from the Physics and Mathematics Department of the Leningrad Polytechnic Institute, where he passed a scientific school at A.F. Ioffe . Being already a well-known scientist in the field of atomic physics, he was sent to work in the newly formed Ukrainian Institute of Physics and Technology (Kharkov, 1928). Together with A.F. Ioffe , I.V. Obreimov and other scientists, he participates in scientific and organizational work, forming the main scientific areas of the UFTI.

He attached great importance to the neutron, not subject to the influence of Coulomb forces, as an effective particle for probing the nucleus. Long before the scientific community recognized the possible role of a neutron in a nuclear chain reaction A.I. Leipunsky becomes a leading specialist in the physics of the interaction of neutrons with nuclei. His research covers a wide range of neutron physics problems: scattering and absorption processes at various available neutron energies, the possibility of inelastic scattering, slowing down and thermalization of neutrons in various media and at different temperatures.

The most complete representation of A.I. Leypunsky about possible options for the implementation of the chain reaction are described in his two pre-war (January 1941) works: “Fission of nuclei” and “Fission of uranium”. These articles are among the very first works of Soviet physicists in which the physical characteristics of fission by neutrons and competing processes are comprehensively considered. For the first time, critical mass estimates are given for various embodiments of a chain reaction. A.I. Leipunsky concluded that a chain reaction is possible in a mixture of uranium-235 with hydrogen and a heavy water reactor using natural uranium. In a mixture of ordinary uranium with hydrogen, a chain reaction cannot be carried out. Already at this stage of knowledge, he emphasized the need to take into account considerations in the calculations.G.N. Flerova of the fission of uranium-238 by fast neutrons produced in the fission of uranium-235. He also clearly needed additional work to determine the constants included in the calculation of uranium reactions, to determine the cross sections for the capture of slow neutrons by oxygen, hydrogen and carbon.

With the outbreak of war, the work of Soviet scientists in nuclear physics was discontinued, and the institutes switched over to defense missions. In 1943, A.I. Leipunsky is involved in research and organizational work on the atomic problem. In 1944, he, being the director of the Institute of Physics and Mathematics of the Academy of Sciences of the Ukrainian SSR, created a department of nuclear physics, the main task of which was to obtain data on neutron-nuclear interactions needed to create atomic technology. As a result of the research, a number of new nuclear-physical results were obtained, in particular, the shell structure of nuclei was experimentally proved.

A.I. Leipunsky devoted great attention to creating a base for nuclear physics research. In the late forties, he put forward the idea of creating a ring proton accelerator with an energy of 1.5 GeV, in which the frequency of the accelerating field synchronously changes with increasing magnetic field (UPC-1.5). Further V.I. Wexler gave its name to such an accelerator - the synchrophasotron. In Obninsk, organized in 1946, the Institute (IPPE) under the direction of A.I. Leipunsky conducted a series of experimental and theoretical studies, connected "Electrosila", Institute A.L. Mints, Porcelain Factory named after Lomonosov. However, in the future it was decided to increase the energy of accelerated protons to 10 GeV, to transfer the leadership in the creation of the acceleratorIN AND. Wexler and transfer the construction of the synchrophasotron to Dubna.

At the end of 1949 A.I. Leipunsky proposed the development of fast neutron reactors with expanded fuel reproduction. While information on the cross sections for the interaction of thermal neutrons with nuclei was in many cases available, the interactions of fast neutrons with nuclei were studied much more poorly. A wide field of activity has opened up in the field of fundamental nuclear physics. Experimental and theoretical research began to develop rapidly at the institute. A team of nuclear scientists arose - A.I. School Leipunsky, who quite quickly reached a high level of professional skill.

At the first stage of the development of work, A. I. Leipunsky not only supervised, but was directly involved in nuclear physics research. More than once, he proposed unexpected original ways to solve the tasks, which allowed to significantly accelerate the matter.

An accelerator base has been created at the IPPE, providing the possibility of studying neutron reactions in the entire reactor range of neutron energies. The research program included not only precision measurements of cross sections, but also the physics of nuclear reactions. Much attention was paid to the process of nuclear fission. At the seminars led by A.I. Leipunsky considered the latest achievements in the field of nuclear physics of low and medium energies.

One of the manifestations of attention A.I. Leipunsky's fundamental research in nuclear physics was the creation of a rechargeable electrostatic accelerator EGP-10M at the IPPE. Prior to launch, work was carried out to develop a nuclear physics research program at this accelerator. A.I. Leipunsky directly supervised its formation and demanded review reports for each section. In particular, such new problems for the IPPE as analog states in nuclei, nuclear fission in direct reactions, nucleon pairing, shell effects, etc. were considered. To study theoretical and experimental studies that are linked to studies on a charge exchange accelerator.

Great attention A.I. Leypunsky was given the study of nuclear reactions taking place in nuclear reactors. Work on the physics of nuclear fission, the study of the mechanism of inelastic scattering and radiation capture of neutrons (direct, pre-equilibrium equilibrium reactions), the density of nuclear levels, and other pressing problems of nuclear physics has been widely developed at the IPPE.

Thanks to a deep understanding of the fundamental aspects of the processes of interaction of neutrons with nuclei, physicists of the Physics and Power Institute with the direct participation of A.I. Leipunsky was able to quickly develop the necessary minimum of quantitative information about the constants characterizing these interactions and substantiate the physical concept of fast neutron reactors.

Characteristic for A.I. Leypunsky's style of work - bringing the results of basic research to practical applications - has brilliantly proven itself in such an application of nuclear physics as fast-neutron nuclear power.

During the period of active scientific work (1927-1972) A.I. Leipunsky published more than 120 works in atomic, nuclear, neutron and reactor physics in Soviet and foreign publications.

A.I. Leipunsky conducted intensive scientific and organizational work. Over the years, he was the director of the UFTI, the director of the Institute of Physics and Mathematics of the Academy of Sciences of the Ukrainian SSR, participated in the work on the “Uranium Problem”, was the deputy for science of one of the leaders of the atomic problem, AD Zverev, was in charge of the sector at ITEP, and was dean of MEPhI. At these posts, he made a significant contribution to determining the topics of nuclear physics research, to organizing them, and to creating new experimental equipment.

A.I. Leipunsky was a direct participant in the emergence of nuclear physics research in the USSR. He was one of the most respected experts in neutron physics, overcame many scientific and technical difficulties in the implementation of his ideas, devotedly devoted himself to his chosen scientific field.

For outstanding services and organizational activities for the development of science A.I. Leipunsky was awarded the Lenin Prize, awarded the title Hero of Socialist Labor, he was awarded three orders of Lenin, orders of the October Revolution and the "Badge of Honor", and medals.

A.I. Leipunsky died in 1972 and was buried in Obninsk, Kaluga Region.