Seminars

"Thanks to their efforts, perseverance and talent..."

On 9 February, the first seminar in the series dedicated to the 40th anniversary of the commissioning of the IBR-2 reactor was held in the FLNP Conference Hall. The report "Development of neutron diffraction research at IBR 2" was delivered by the chief researcher of the Laboratory Anatoly Mikhailovich Balagurov.

First, those gathered saw the pages of the historical act on the acceptance of the reactor for operation by the State Committee chaired by A.M.Petrosyants, Chairman of the USSR State Committee for the Use of Atomic Energy: "To be accepted into operation from 10 February..."

The speaker noted that in the history of the development of the IBR 2 spectrometers complex and techniques of implementing experiments on it, there were several key moments, including the development of the world's first high-resolution Fourier diffractometer, the development of techniques for measuring neutron diffraction patterns from microsamples in high-pressure chambers with anvils and the development of analysis techniques irreversible transients in real time. The decisive role in the implementation of these techniques at the IBR 2 reactor was played by V.A.Trunov (PNPI, Gatchina), V.A.Somenkov (NIC KI, Moscow) and G.M.Mironova (FLNP JINR), thanks to their efforts, perseverance and talent from which these techniques originated, were developed to a high degree of perfection and are still successfully used today. "Our colleagues are no longer with us and one of our responsibilities is to remember them," Anatoly Mikhailovich noted.

Vitaly Andreevich Trunov, having graduated from the Leningrad Polytechnic Institute, worked at the Leningrad Nuclear Physics Institute (Gatchina), at the VVR-M reactor and was engaged in the development and construction of neutron spectrometers. His main work related to Dubna was the development of Fourier diffractometry on a pulsed neutron source. It all started with his contacts with physicists from the Technical Research Centre of Finland, with the help of whom, in 1984, the world's first Fourier diffractometer, called mini-SFINKS, was put into operation at the WWR-M reactor. The leaders of this research V.A.Trunov and Professor P.Hiismaki from Finland understood that this technique of measuring neutron diffraction spectra is more efficient on a pulsed neutron source and in 1986, FLNP received a proposal to construct a high-resolution Fourier diffractometer (HRFD) at the IBR-2 reactor. The required funding (about 800 thousand dollars) was found in 1991 and already in June 1992, at a session of the JINR Scientific Council, P.Hiismaki reported on the first results.

The first employees of the FLNP Diffraction Group: B.N.Savenko, A.I.Beskrovny, M.Dlouga (Czech Republic),
A.M.Balagurov, G.M.Mironova. 2005

In a recent article (No.5 of the weekly), V.L.Aksenov that headed construction of HRFD at JINR, wrote: "This diffractometer that allows measurements with a resolution almost limiting for neutron crystallography, destroyed the prejudice that existed in the scientific community regarding the limited capabilities of IBR-2 and brought it to the forefront of pulsed neutron sources in the world."

A similar conclusion was made by A.M.Balagurov based on the results of this part of his report: "Fourier diffractometry is the most efficient technique for obtaining a resolution of interplanar distance in crystals at the level of 0.001 while maintaining high aperture ratio. The decision to develop Fourier diffractometry at the IBR-2 reactor, taken on the initiative of V.A.Trunov and supported by JINR Directorate, was absolutely correct!"

After having graduated from MISiS, Viktor Aleksandrovich Somenkov worked at the Kurchatov Institute, where at the IR-8 reactor in the early 1980s, under his supervision, a specialized DISK diffractometer was developed for experiments at high pressures. For pressure, chambers with anvils made of ruby or diamond single crystals were used, between which a sample of small volume, about 1 mm³, was positioned. This technique allowed to rise to pressures that were tens of times greater than those available in other world neutron centres.

The success of this research prompted V.A.Somenkov to contact FLNP JINR with a proposal to develop a specialized diffractometer at the IBR-2 reactor. The idea was accepted and already in the early 1990s, the first scientific experiments were carried out with high-temperature superconductors, ammonium halides and other compounds with interesting physical properties. Currently, this topic is one of the most successful at IBR-2 and currently develops. In particular, another high-pressure diffractometer with increased aperture ratio was developed that allowed to study the atomic and magnetic structures of crystals at pressures up to 500 kbar.

The speaker noted that Fourier diffractometry and experiments at high pressures were included as the main components of the scientific research that was awarded the State Prize of the Russian Federation in 2000 for "Development and implementation of new techniques of structural time-of-flight neutronography using pulsed and stationary reactors." The team of authors included V.L.Aksenov, A.M.Balagurov, V.V.Nitz and Yu.M.Ostanevich (JINR), V.A.Kudryashev and V.A.Trunov (PNPI RAS), V.P.Glazkov and V.A.Somenkov (RNCCI).

Galina Matveevna Mironova graduated from the Physics Department of Moscow State University and from 1972 to 2022, worked at FLNP JINR. Her main scientific topic was the investigation of irreversible transient processes in real time. Examples of such processes are solid-phase chemical reactions, during which the final product, isotope exchange in hydrides, structural phase transitions in crystals and others are developed, when a mixture of initial components is heated. If some important characteristics of the process can be determined in a time much less than the characteristic time process itself, then their changes can be traced with the necessary degree of detail. Soon, after IBR-2 was put into operation in 1984, G.M.Mironova demonstrated that it is at the IBR-2 reactor, that all the required conditions for this kind of experiments are available if we use diffraction and small-angle scattering of thermal neutrons. Already in her first papers on the hydration of cements, the synthesis of YBa₂Cu₃O_x ceramics, isotope exchange in lipid multilayers, the kinetics of the ε → δ phase transition in TiD and others, minute and often second, measurements of neutron spectra with the required level of statistics were achieved. To do this, G.M.Mironova had to make several inventions and also get electronics engineers to operate in a special fashion for registering equipment. A very important part of her work was the preparation of specialized software for analyzing the accumulated information, in the development of which Galina Matveevna's eldest son, that was still a schoolboy at that time, took an active part. Nowadays, such experiments at IBR 2 have become almost routine, but in the 1980-1990s, their results caused an almost shock reaction in the neutron community.

In conclusion, A.M.Balagurov drew attention to the fact that the activities of V.A.Trunov, V.A.Somenkov and G.M.Mironova to some extent refute the well-known law stating that a neutron experiment should not be carried out if there is an alternative method. The information obtained in a neutron experiment is always useful, especially in cases where some difficult issue is met.

Summing up the seminar, FLNP Director Egor Lychagin emphasized that all three techniques discussed at the meeting will definitely be transferred to a new, higher-flux neutron source, the plan for the development of which is currently discussed in the laboratory.

Olga TARANTINA,
photo from the archive of A.M.Balagurov