The team and its activities

New life of the EG-5 accelerator

The EG-5 electrostatic accelerator is a long-liver of the Frank Laboratory of Neutron Physics that has been operating properly since 1965. This is a reliable instrument for meeting a wide range of issues in the field of nuclear physics, solid-state physics and radiation technologies. The ion beam of the accelerator at a relatively high current (up to 100 ?A) has a very high energy stability, due to which the EG-5 facility can operate both as a neutron generator and as an ion source for ion beam analysis.
Today, using EG-5, research on nuclear reactions of neutrons with a solid state, involving the emission of charged particles, on elemental depth profiles of multilayer semiconductor architectures, as well as irradiation of materials is carried out. On 21 September the responsible for the facility Aleksandr Doroshkevich delivered a report on the latest results of the work of the EG-5 group at the seminar of the Department of Nuclear Physics of FLNP. And for our weekly, he spoke in more detail about the group, current and further research, as well as on the progress of the modernization of the facility.

Unique facility

Our group, as a separate division in FLNP, has been developed recently. It started developing in 2019 and by now, in my opinion and according to certain objective indicators, it has almost developed. Today, the group consists of 23 employees, they are completely involved in the maintenance and modernization of a relatively large amount of technological equipment of the accelerator complex and in scientific research using the appropriate instrument infrastructure.

Let me remind you that an electrostatic accelerator is a compound hardware complex that includes technological systems rather complicated in maintenance, in particular, a high-voltage (up to 4 MeV) high-pressure gas balloon system, a vacuum, an electromagnetic ion beam control system and an electronic system for monitoring and automation of technological processes. The equipment of the complex is installed in the accelerator "tower" of building No.42 and in the rooms of two adjacent experimental halls. The accelerated ion beam is distributed through ion guides to one of six beamlines (three for each experimental hall) equipped with terminal devices. Terminal devices are separate nuclear physics facilities, each of them is unique in its own way both within JINR and in Member States. Unfortunately, EG-5 is currently the only single-stage electrostatic accelerator at JINR.

Obviously, among the accelerator facilities of the Joint Institute, EG-5 occupies its own unique niche, since it allows to obtain sufficiently intense (10¹²particles/cm²) fluxes of quasi-monoenergetic accelerated (up to 1-2.5 MeV) charged particles (singly charged hydrogen, helium or deuterium ions) and fast neutrons (4.1±0.1 MeV). It should be noted that such small energy dispersion cannot be obtained using relatively inexpensive charge-exchange (tandem) electrostatic accelerators, not to mention accelerators manufactured on other physical principles.

At the current stage of the scientific and technological revolution, particle energies up to 4-5 MeV are no longer of great significance for fundamental nuclear physics, yet the range of various applied tasks, where our beams are required, rapidly expands with the development of bionanotechnologies and interdisciplinary scientific areas. These investigations are in demand, as evidenced by the demand for our results in international highly rated journals. Obviously, the "centre of mass" of the spectrum of topical scientific problems for EG-5 has shifted to the applied research area since its development (1965). Currently, seven research scientific areas for development have been outlined in the group that cover a wide range of the most urgent challenges of our time: from the development of advanced electronics devices (homogeneous nanoelectronics) and the breeding of drought-resistant rice varieties to the research of astrophysical processes of stellar nucleosynthesis.

Source, instrument, device

The accelerator complex based on the electrostatic accelerator EG-5 is multifunctional. In appropriate modes, it can be used as a source for ionizing radiation, as an instrument for physical and chemical modification of materials and of course, as a spectrometric research device. For instance, using fast neutrons with a narrow energy dispersion obtained at (d-d) reaction on the EG-5 accelerator, relatively high doses of radiation can be imparted to the tested materials without inducing artificial radioactivity in them. By implanting helium inert gas ions, it is possible to significantly change the mechanical stress fields in localized volumes of materials (subsurface layers), rather than to induce structural-phase transformations or to produce the so-called "helium porosity". In the latter case, the microstructure changes. Helium porosity, like other radiation-induced defects, is still a major radiation technology challenge and has always been a topical object of research. It should be noted that at present, EG-5 is the only accelerator at JINR that allows to carry out such research on helium in the energy range of 1-2.5 MeV. The implantation of hydrogen ions allows to implement partial chemical reduction of metal oxides in highly localized areas of the material, thereby changing the stoichiometric ratio of elements, that is, to carry out chemical modification of materials. The implantation of ions into the crystal lattice of materials also allows to change their electronic structure and electrical properties that is widely used in the electronics industry. An essential advantage of accelerator implantation technologies is the precise spatial localization of implanted ions, wherein the occurrence of intermediate layers of material in the path of the ion beam is not a significant obstacle for this.

Irradiation of biological objects allows to induce beneficial mutations for new varieties of agricultural products. Irradiation with fast neutrons of certain substances causes nuclear reactions with the emission of charged particles. The subject matter of the group of Professor Yu.M.Gledenov (FLNP) consists of nuclear constants of corresponding reactions. The physics of scattering of monoenergetic alpha particles using atoms of subsurface layers of matter is the basis for the methods of ion-beam spectrometry that historically constitute the main area of our group's activity. The uniqueness of these methods is due to the possibility of studying multilayer planar structures without their destruction using layer-by-layer thinning, as for instance, when using the XPS method. At the same time, the sensitivity limit of ion-beam analysis is at least two orders higher than using XPS and is about 10^-3-10^-4 atmospheric %. It should be noted that ion-beam methods of analysis allow to carry out a quantitative elemental analysis of light atoms, as well as isotopes.

In addition to ion-beam spectrometry, the group widely uses complementary methods for the research of the physical properties of surfaces, in particular, spectroscopic ellipsometry, impedancemetry and voltammetry. These methods allow to characterize the electrical, electronic and optical properties of the objects under study.

Results of the group's work in 2022

At the seminar, I introduced to my colleagues the latest results of our work in this year.

On semiconductor materials, together with P.B.Lagov, Professor of the Department of Semiconductor Electronics and Semiconductor Physics (National University of Science and Technology MISiS, Moscow), a range of successful experiments were carried out with the irradiation of semiconductor crystals with hydrogen, he also joined us with the largest electronics manufacturer in Russia - JSC Mikron. An agreement on preparation of equipment and the future technological operation of hydrogen ion implantation in the production of high-power high-voltage diodes has already been reached with them.

In my opinion, the results obtained by our group in powder nanotechnologies are no less significant. We are talking about the development of new devices for advanced electronics and alternative energy. In competitive work with the Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine, for the first time, we managed to fix a clear effect of the "rectifying" contact of two nanoparticles of different sizes. This is a completely new word in the development of electronics, since this phenomenon allows one to move on to the so-called homogeneous electronics. Such electronics will be devoid of the basic drawback of doped semiconductors - diffusion instability, due to which any semiconductor device fails sooner or later. It greatly interferes with the development of devices and systems of critical technologies, since diffusion processes exponentially accelerate with an increase in temperature and the probability of failure of such devices and equipment as a whole increases many times over. Homogeneous electronics will be devoid of this drawback, obviously, both the common type of devices and their operation modes will change. In my opinion, this is a very interesting area that should be developed. The situation is the same in renewable energy: together with other international research groups, we try to develop devices based on zirconium oxide nanopowders that convert moisture adsorption energy into an electric type. Moisture adsorption energy is a rather serious promising source of energy. For instance, a building weighing 1000 tons (6-storey house) during adsorption from the atmosphere (for example, when the day-night cycle changes), only 5 wt% of moisture releases 15 MJ of heat. This is quite a tangible energy that can be used in the active energy infrastructure of new generation buildings. The main issue at this stage is the extremely low efficiency of adsorption hydroelectric converters or chemoconverters. Six months earlier, we worked on this topic as part of the international project under the HORIZON 2020 programme. Today, work in the field of powder technologies for alternative energy and advanced electronics is carried out mainly by students, just outside the project. There are many other equally interesting topics, for instance, in the field of nuclear physics, biology, radiation materials science and others. I will definitely tell you about the work on various topics as soon as possible.

A few words about the group

Just this year, we formed as a group: its structure, internal regulations and in fact, the system for obtaining scientific data, were developed. The team is friendly and efficient. Many of the group members are involved in science on our accelerator. The staff members of the group represent seven countries: Azerbaijan, Belarus, Bulgaria, Vietnam, Cuba, Russia, Ukraine. We work both in collaboration with the JINR Member States and with research teams from Spain, Portugal and other countries. The group is mostly youth. All employees strive to improve their qualifications: they master not only scientific specialties, but also technical ones. This year, Konstantin Studnev was trained at JINR University Centre, confirmed his qualifications as a scaffolder and a milling machine operator, as well as masters a design profession. Ilya Chepurchenko entered the magistracy of the Moscow Polytechnic Institute for a design specialty. Five young members of the group currently prepare Ph.D. dissertations. Engineer Rafael Isaev, a part-time postgraduate student at MEPhI, develops an area in radiation materials science in the group. As soon as the senior researcher Zdravka Slavkova (Bulgaria) comes to the group, we are going to develop investigations with lipid membranes and use our beams to modify these membranes. The investigation of mutagenesis of cells and biological objects is carried out, the urgent task of studying the impact of cosmic radiation on the development of wildlife objects and their evolution is met, headed by the researcher Yulia Aleksiayenak. The energy of our accelerator allows to simulate the secondary cosmic radiation to some extent. Within the framework of cooperation with the Pskov University, we will participate in the work on the mutagenesis of the oyster mushroom. We are going to cooperate with LRB JINR after modernization of the accelerator.

Currently, a new chamber is developed for research of nuclear reactions, where targets produced from heavy elements will be irradiated with an ion beam aimed at studying nuclear constants. Our colleague student Anna Zakharova won the first place in the physics competition at the Lomonosov-2022 Youth Conference and became the best out of 600 applicants. She entered the Faculty of Physics of Moscow State University without exams in the "Neutronography" specialty, at present, she studies and works with us. Our colleague from Vietnam Chan Van Hook defended his Ph.D. thesis on the research of the impact of solar radiation on the degradation of solar cells. The degradation mechanism is related to fast particle flux that leads to smearing of the heterophase boundary and a decrease in the efficiency of functional heterojunctions. Our leading researcher Doctor of Physical and Mathematical Sciences A.K.Kirillov studied the dependence of the microstructure of fossil coals on the depth of occurrence using small-angle neutron diffraction in his paper. It was published in the peer-reviewed journal Fuel with an impact factor of 8. We have a large collaboration with Member States. Currently, we cooperate in seven projects with Poland, Serbia, Belarus and Kazakhstan.

In general, this year we did a good job - 13 articles were published, 12 of which - in highly rated journals. The average impact factor of our publications today is 3.8.

Prospects for the development of the facility

The accelerator is currently modernized, a large amount of work is carried out by our technical subgroup not only for the repair of units, but also for their modernization. This year, the modernization project was extended and appropriate funding was allocated. The Directorate set clear objectives and determined the deadlines for their implementation. In particular, a unique microbeam spectrometer is scheduled to be installed on the beamline 2 of the accelerator. A special foundation has already been laid for it. There are only a few such devices in Member States. The microbeam spectrometer will allow to analyze microscopic objects from rough surfaces, to irradiate separate cell organelles, it can be used in the production of devices for microsystem technology, nanoelectronics, its occurrence opens up a whole range of possible interdisciplinary investigations.

After the upgrade, we will also have the neutron generator option. In addition to the gas neutron-producing target, solid-state lithium targets will be installed. We will be able to carry out neutron activation analysis on fast neutrons, to irradiate objects to relatively large fluences with variations in temperature, pressure or magnetic fields; the organization of users' programme is scheduled.

The experimental halls are currently renovated, oil-free vacuum equipment is being installed, furniture is being replaced - everything will be done with the latest technology. I would like to note that our relatively successful, in my opinion, progress is the result of the support of the FLNP Directorate and personally Valery Shvetsov. Taking into account the high potential of the instrument complex and the group itself, we claim to be a serious player in the scientific field of FLNP.

The material was prepared by Olga TARANTINA