OPERATION AND DEVELOPMENT OF FLNR ACCELERATOR COMPLEX (DRIBs-III)
Under the theme on the development of the FLNR cyclotron complex (DRIBs-III project)
in 2021, work was carried out on the construction of new and on the upgrade and optimization of existing accelerating set-ups with a view to improving the intensity and the quality of ion beams of both stable and radioactive nuclides in the energy range from 5 to 60 MeV/nucleon. The project also aimed at improving the efficiency of experiments on the synthesis of new superheavy elements and study of their properties as well as at expanding the programme of experiments on the synthesis of rare exotic nuclei and study of reactions with beams of radioactive nuclides.
According to the JINR Topical Plan for 2021, the following results were achieved.
DC-280. The basic facility of the Superheavy Element Factory — DC-280 cyclotron — provided 5095 h of beamtime for research in 2021. During this period, the novel gas-filled separator GFS-2 was employed for conducting experiments on the synthesis of element 114 (flerovium) in the 242Pu + 48Ca reaction, element 115 (moscovium) in the 243Am + 48Ca reaction, and element 112 (copernicium) in the 238U + 48Ca reaction. The experiment on the synthesis of Mc lasted for 1820 h; Fl, for 410 h; and Cn, for 810 h. The energy of ions extracted from the cyclotron could be smoothly varied, which was of particular importance for experiments conducted at the SHE Factory. Thus, the intensity of the beams of 48Ca ions in experiments varied from 0.05 up to 6.5 pμА. It should be noted that the intensity of the 48Ca beam reached 10 pμА at the extraction radius, providing an intensity of 7.1 pμА in the beam transport channel [1, 2].
Work on adjusting the acceleration modes for the 52,54Сr and 48Ti ions continued. The intensity of the accelerated 52Cr beam reached 2.4 pμА, and the intensities of the beams of 54Cr and 48Ti ions were 2.2 and 1 pμА, respectively. In addition, preparations were complete for experiments at a new physics set-up GFS-3.
U-400M. As part of the U-400M cyclotron upgrade project, the main magnet coils were replaced with a new set in collaboration with the OOO NPO GKMP, Bryansk . The novel components were connected to the power supply and cooling system; a magnetic field measuring system was installed. Another major enhancement involved an upgrade of operational elements and manufacturing of novel components for the vacuum system and for the cooling and control systems of the U-400M cyclotron. The start-up of U-400M is planned for the end of 2022.
U-400. A wide variety of scientific and applied investigations in heavy-ion physics were conducted using the U-400 cyclotron. In 2021, the cyclotron provided 6085 h of beamtime. Most of the operation time was devoted to the implementation of the programme focused on studying the beams of 22N ions (SHELS set-up), 46Ti ions (chemical set-up, SHELS), 48Ca ions (CORSET, SHELS, MAVR), and 56Fe ions (MAVR). In addition, experiments on accelerating 238U ions were carried out. Applied studies (NIIKP) were also conducted employing the U-400 cyclotron.
IC-100. The upgraded IC-100 cyclic implanter is used for the implementation of the applied research programme. Ions ranging from С to W accelerated up to 1.0–1.2 MeV/nucleon at IC-100 were used for irradiation of graphene samples, Si3N4, TiNZrN/Zr, AlNTiN, ZnO, ODS steels, high-temperature superconductors, and titanium-based alloys (under the collaboration programme with the South Africa, Poland, Serbia, Belarus, Kazakhstan, and the Czech Republic).
DC-140. Work on the creation of a new DC-140 cyclotron for applied research has begun . Sent into retirement, the U-200 cyclotron was dismantled and will be replaced with a new accelerating set-up. The foundation and the building were carefully examined. Civil engineering work is proceeding for the building that will host the new cyclotron. In parallel, the systems of the successor are designed and manufactured. The construction of the control and engineering systems is in full swing.
SYNTHESIS AND PROPERTIES OF NUCLEI AT STABILITY LIMITS
Experiment at Gas-Filled Separator (GFS-2). In 2021, three series of experiments were conducted at the new gas-filled separator GFS-2 of the Factory of Superheavy Elements at FLNR JINR. The fusion reactions of a beam of 48Ca ions that impinged on target nuclei of 243Am, 242Pu, and 238U were used to determine the operational characteristics of the new separator, analyze the prospects for future investigations of superheavy nuclei using higher sensitivity (transmission, background conditions, target stability, etc.), and to thoroughly study the properties of the isotopes of Мс, Fl, Cn and their daughter nuclei. The results showed that the transmission of GFS-2 was twice as efficient as that of GFS-1 at U-400.
The 243Am + 48Ca reaction was studied at five projectile energies and an intensity of up to 1.3 pμА. Six new decay chains of 289Mc (product of the 2n channel), 58 chains of 288Mc (produced in the 3n channel), and two chains of 287Mc (produced in the 4n channel) were synthesized, thereby making it possible to produce a novel isotope 286Mc (5n channel). It should be noted that in earlier experiments the isotope 287Mc was observed only in three chains, and the decay products of 286Mc were detected in two chains. An α decay of 268Db was detected for the first time, allowing the measurements of the α-decay branch and the half-life; moreover, a new isotope 264Lr was produced. Spontaneous fission of the isotope 279Rg was for the first time registered. The cross section for the 3n evaporation channel was shown to be twice as high as that previously measured.
In the experiment with 242Pu, the intensity of 48Ca ions reached 3 pμА. At two 48Ca energies, 25
decay chains of 286Fl and 69 decay chains of 287Fl were registered, respectively. The cross sections were also twice as high as those measured earlier, which could be attributed to statistics that had increased manyfold. Indications were found for the existence of two decay branches of 287Fl, 283Cn, and 279Ds, which differed in the correlation between the partial probabilities of α decay and the spontaneous fission of 279Ds. This can present evidence for the population of the low-energy levels of 287Fl and/or 283Cn. The specific features of the 286Fl and 282Cn decays can also be ascribed to the decay of isomeric levels.
The intensity of the 48Ca beam irradiating the 238U target was 6.5 pμА. During the experimental run, sixteen 283Cn decay chains were observed. In the course of a series of experiments, both the cross sections for the reactions under investigation at various projectile energies and the decay properties of about 30 isotopes of elements Rf through Mc (in Fig. 1 they are marked in bright yellow) were measured. The charges of the Mc, Fl, and Cn ions were measured in rarefied hydrogen. The reliability of the charge systematics obtained at GFS-1 was confirmed, which is crucial for the synthesis of new elements 119 and 120. The results of experiments are presented in [5–8].
Spectroscopy of Heavy and Superheavy Nuclei. The radioactive decay properties of the 253Rf nucleus synthesized in the complete fusion reaction of 50Ti ions with target nuclei of 204Pb, followed by an emission of one neutron, were investigated. Spontaneous fission of 253Rf was confirmed as a dominating decay mode. 253Rf underwent an α decay registered for the first time, leading to an earlier produced isotope 249No (bα = (17 ± 6)%) . In addition, two low-lying short-lived spontaneous fission states for 253Rf with drastically different half-lives were observed. One of these states with a half-life of 0.66 ms was detected for the first time and could be referred to a high-spin K isomeric state in 253Rf. The results were submitted to Phys. Rev. B .
In May 2021, a new detecting system SFiNX was commissioned. This physics instrument comprises 116 neutron counters (3He) surrounding a focal position-sensitive DSSSD detector 100 × 100 mm in size. The SFiNX system is highly efficient in registering neutrons (55%) and is dedicated to studying the properties of spontaneously fissioning short-lived nuclei produced in experiments at the SHELS separator . The new system enabled measurements of neutron yields for the short-lived isotope 252No with the record precision (an average number of neutrons emitted per fission was ν = 4.25 ± 0.09).
During the summer shutdown, the ion-optical system of the SHELS separator was upgraded. The first triplet of ageing quadrupole lenses was replaced by a new set manufactured by Sigma Phi in France. The new triplet aperture is 50% larger, allowing, in turn, a better capture of reaction products flying out from a target. An improved configuration of the vacuum chamber of the new triplet enables a considerable reduction of the background from scattered ions. Conducted in October 2021, a short test run employing the upgraded SHELS separator showed a significant improvement of the characteristics of the ion-optical system and a background reduction in the detector.
Throughout 2021, the FLNR group worked on the assembly and start-up of the new GFS-3 separator installed on the fourth beam line of the DC-280 cyclotron of the SHE Factory. The start-up of the machine is scheduled for the beginning of 2022.
Chemistry of Transactinides. Research in 2021 aimed at studying the stopping of reaction products in the recoil chamber after their separation in the gas-filled recoil separator and further transport in inert gases to the cryodetector. These investigations are necessary to conduct a first chemical experiment at the SHE Factory scheduled for 2022. The research was done in cooperation with a superheavy element group from the Paul Scherrer Institute (PSI), Switzerland. The behavior of mercury, a light homologue of copernicium, was studied online employing the U-400 accelerator. Reaction products were first separated in the kinematic separator SHELS. The time of flushing mercury out of the chamber by a gas flow into a quartz tube and the transport time through a Teflon capillary into the cryodetector were measured using two short-lived α-emitting products 179,180Hg formed in the 136Ce(48Ti, xn)184−xHg reaction. The experimental technique consisted of using a trigger, which turned on a beam for 500 ms and subsequently switched it off for 10 s. In this time interval, α radiation was continuously measured by the cryodetector operating in a given mode for argon with a flow of 1 and 3 l · min−1 . The mercury detection time after a short beam-on interval was 0.5 s, which was in good agreement with the results obtained with a model of the chamber (COMSOL software) simulating mercury yield and Ar flow.
By using the SHELS separator, the examining of the conditions for the formation of volatile compounds of the superheavy element nihonium continued. Experiments in 2021 mainly concentrated on studying the effect of oxygen and water vapor on the formation of various compounds of Tl — a light Nh homologue — on a quartz surface. The chemistry of single atoms of thallium produced in the 141Pr (48Ti, xn)189−xTl reactions at U-400 was studied by isothermal adsorption chromatography. A tantalum getter with a furnace temperature of 1000◦C was placed in front of a quartz column to ensure the elemental state of thallium compounds formed by stopping their atoms in the recoil chamber. The admixtures of oxygen and water vapor to the carrier gas Ar were used after passing through the getter. Isothermal adsorption chromatography on the quartz surface was performed at temperatures ranging from 100 to 850◦C. Thallium yield was measured online by gamma spectrometry. The obtained integral chromatograms revealed two chemical forms of thallium characterized by different adsorption behavior. Data are currently being processed with a view to determining the enthalpy of adsorption and identifying the detected thallium compounds.
Dynamics of Heavy-Ion Interaction, Fission of Heavy and Superheavy Nuclei. The synthesis of nuclei with Z > 118 and study of their properties are of particular interest in investigating the “island of stability” due to the shell effect at N = 184 and Z = 114 and/or Z = 120–126. To advance into the region of nuclei with Z > 118 using complete fusion reactions, projectiles heavier than 48Ca should be used. In passing to heavier incident ions, however, the Coulomb repulsion between interacting nuclei strengthens, thereby leading to an increase in the contribution of quasi-fission and deep inelastic scattering, suppressing the formation of a compound nucleus. That is why the experimental studies of competition between fusion and quasi-fission in reactions with the beams of titanium and chromium are of paramount importance in planning experiments on the synthesis of as-yet-undiscovered superheavy elements. Mass and energy distributions of binary fragments formed in the 54Cr + 232Th, 238U reaction at energies in the vicinity of the Coulomb barrier were measured. Experimental data are processed.
Mass and energy distributions of the fission fragments of 178Pt, 180,182,183,190Hg, and 184,192,202Pb formed in reactions with 36Ar and 40,48Ca ions over a wide energy range of 35–70 MeV were measured with a view to studying the fission properties of excited pre-actinide nuclei. The fission properties were shown by analysis to be governed by the proton numbers Z ≈ 36 in a light fragment, Z ≈ 46 in a heavy fragment, and Z = 28 and/or 50 in both light and heavy fragments. With regard to the fission mode ascribed to the proton number Z ≈ 36, a fissioning nucleus has a prolate shape, as opposed to that predicted by the liquid-drop model, and is more compact than that peculiar to the mode caused by the influence of Z ≈ 46 [12, 13].
In studying the 68Zn + 112Sn reaction, it was found that mass and energy distributions of fragments differed widely from those formed in the 36Ar + 144Sm reaction leading to the formation of the very same 180Hg composite system at similar excitation energies of about 50 MeV. The fragment mass distribution for the reaction involving 68Zn is broad and double-humped, with maximum yields of light and heavy fragments of 70 and 110 amu, in contrast to 80 and 100 amu during the fission of 180Hg formed in the 36Ar + 144Sm reaction. Such a considerable difference in mass–energy distributions is due to a greater contribution (over 70%) from quasi-fission in the reaction with 68Zn ions . The research on the fission properties of pre-actinide nuclei was supported by the RFBR grant No.19-52-45023_инд_а (jointly with RFBR and the Department of Science and Technology of the Government of India).
In 2021, significant efforts were also focused on studying fast fission. Mass and energy distributions of fragments formed in the 40Ca + 144Sm, 208Pb reactions at energies above the Coulomb barrier were measured. Angular momenta at these energies are high, so the fission barrier vanishes. The fission barrier for 184Pb (40Ca + 144Sm) is mainly determined by the macroscopic properties of the potential, whereas the nucleus stability for 248No (40Ca + 208Pb) is governed by the shell correction.
The studies showed that mass distributions of fast fission fragments were almost unaffected by increased interaction energies for the reactions under investigation and were characterized by a negligible mass asymmetry η = (AH − AL)/(AH + AL) = 0.17 for 184Pb and 0.21 for 248No. Mass and energy distributions of quasi-fission fragments formed in the 40Ca + 208Pb reaction differed significantly from those of fast fission fragments. The shape of the mass distribution of quasi-fission fragments was broad and two-humped, with the light fragment of mass about 77 аmu (η ≈ 0.38), which is ascribed to a strong effect of the closed proton (Z = 28) and neutron (N = 50) shells. A paper reporting these results was submitted to Phys. Rev. C. The studies of the effect of the angular momentum on the formation of the compound nucleus were supported by the RFBR grant No.19-42-02014 (jointly with RFBR and the Department of Science and Technology of the Government of India).
Structure of Exotic Nuclei. In 2021, the generated data were analyzed on the experiment with a high-quality 8Не beam (I ∼ 105 s−1, P ∼ 95%, E = 26 MeV/nucleon) in the 8Не(d, 4He)6H and 8Не(d, 3He)7H reactions conducted at the ACCULINNA-2 fragment separator . In nuclear energy levels, there were indications of the population of the ground state at 2.2(5) MeV and several excited states at ∼ 5.5, ∼ 7.5, and ∼ 11 MeV. The 7Н energy spectrum was defined by a missing mass method with the resolution ΔE ∼ 1 MeV by measuring the energies and the emission angles of 3Не recoils in coincidence with tritons from the decay 7H → t + 4n. The experimental technique enabled simultaneous investigations of the 6Н system energy spectrum populated in the 8Не(d, 4He)6H reaction. The data analysis is underway.
Studies continued of the low-lying states for the isotopes 7He, 9He, and 10Li populated in the 6He(d, p)7He, 8He(d, p)9He, and 9Li(d, p)10Li reactions, respectively. For analyzing and interpreting experimental data, theoretical approaches were developed with due regard for the specific features of one-nucleon transfer reactions at a beam energy of 25–30 MeV/nucleon. The data on the spectrum of 7Не energy levels, particularly the interference between states of different parities in the energy range of 1–7 MeV, are being thoroughly analyzed and getting ready for publication. Note also that a high energy resolution of ∼ 150 keV (full width at half maximum — FWHM) for the 7Не ground state 3/2− at E = 0.445 MeV attained in registering triple p–6He–n coincidences was consistent with the best results of the world’s foremost research centres. Taking into account the preliminary analysis of data on 10Li, a wealth of statistics (around 400 triple p–9Li–n coincidences), and a high energy resolution of 230 keV (FWHM), new data on low-lying 10Li states at energies ranging from 0.5 to 4 MeV are expected.
The modifications and upgrade of the research instruments of the ACCULINNA-2 set-up continued into 2021 and involved: (а) construction of a tritium target complex; (b) adjustment of a new tracking system of the secondary beam based on two low-pressure avalanche counters (PPAC detectors); (c) adjustment of the velocity filter based on a highfrequency resonator (RF kicker). Updates on the current status of the ACCULINNA-2 complex are available at http://aculina.jinr.ru.
Reactions with Beams of Light Stable and Radioactive Nuclei. In 2021, two experiments were conducted at the U-400 cyclotron employing the high-resolution magnet analyzer MAVR. In experiments with the beams of 48Са and 56Fe ions accelerated to 10 MeV/nucleon and directed to the Ве, Au, Ta, and 238U targets, the differential cross sections for the emission of alphas and other light charged particles at an angle of 0◦ with respect to their energy were measured with high sensitivity . The resulting spectra were found to contain fast alpha particles of the energy corresponding to the kinematic limit for a three-body exit channel (Fig. 2).
The experimental data were analyzed using a moving source model. The analysis revealed several sources of non-equilibrium particles with extreme energies. The formation of non-equilibrium alphas could be attributed to their emission from a heavier target nucleus upon complete or incomplete fusion of nuclei. Details of a technique for registering coincidences of light particles with the fission fragments of a residual nucleus were also worked out.
Further analysis of experimental data related to the effect of the structure of weakly bound nuclei 6,8He, 9Be, 9,11Li, and 8B on total cross sections was continued.
Fig. 2. Energy spectra of alphas measured at an angle of 0◦. The arrows indicate the kinematic limits of two-body reaction channels
CONSTRUCTION OF NEW AND DEVELOPMENT OF EXISTING EXPERIMENTAL SET-UPS
Construction of a Separator Based on Resonance Laser Ionization (GaLS Set-Up). The GALS set-up under construction is intended for separation and study of the products of multi-nucleon transfer reactions. The following main results were achieved in 2021 :
1. The reference chamber of the GALS set-up designed to search for and study the optimal levels of atomic transitions in multi-stage resonance laser ionization was upgraded. The upgrade began after the parameters of the evaporative laser had been verified. The laser energy density per pulse will be increased up to the level required for atomizing an Os sample. The scanning laser system is currently being modified and adjusted to allow offline work with a reference cell.
2. In cooperation with the Sofia University (Bulgaria), a detecting system of GALS was developed. A key element of the system is a detector component of the BEDO set-up (Orsay, France). The decision on the optimal choice of detectors and the geometry of scintillators is being currently finalized. Designed in collaboration with iThemba LABS (South Africa), the tape station was launched into manufacture.
3. The calculations of the parameters of the electrostatic ion guide system were performed. The distributed power supply systems feeding the beam line electrodes were developed. They are currently being assembled and tested together with the electrical and radio frequency power systems.
Ion Gas Catcher. The construction of the cryogenic gas ion catcher, a new set-up for the SHE Factory and other accelerator FLNR complexes, continued into 2021. A hall was prepared for the assembly and adjustment of the set-up. The apparatus comprises a cryogenic gas catcher and a multiple-reflection time-of-flight mass spectrometer (room 203, bld. 101). A “warm” component of the chamber of the cryogenic catcher was assembled and vented to 10−5 mbar. A multi-electrode system for transporting the beam to the supersonic nozzle is under assembly; components are fabricated for the copper sheath of the cold chamber; and the instrumentation is ready for soldering and welding of the cooling pipe coil for helium fed into the cryogenic catcher.
The multiple-reflection time-of-flight mass spectrometer is designed by the Institute for Analytical Instrumentation of RAS (Saint Petersburg) and supported by a grant from the Ministry of Higher Education and Science of the Russian Federation No. 075-10-2020-117 (“Superheavy nuclei and atoms: Mass limits of nuclei and the borders of the Mendeleev Periodic Table”). This research instrument is intended for precision measurements of the masses of heavy isotopes and superheavy nuclei. In 2021, the design and main ingredients of the set-up underwent conformity assessment, and ion-optical calculations were performed. The feasibility study of a three-dimensional model is ongoing.
RADIATION EFFECTS AND PHYSICAL BASES OF NANOTECHNOLOGY, RADIOANALYTICAL AND RADIOISOTOPE INVESTIGATIONS AT FLNR ACCELERATORS
Comparative Analysis of Radiation Resistance of Nanoparticles Y–Ti(Al)–O in Metallic Matrices and Bulk Y–Ti(Al) Oxides against the Impact of Heavy Ions of Fission Fragment Energy. The tracks of xenon and bismuth ions in the Y4Al2O9 and Y2Ti2O7 nanoparticles were studied using the high-resolution transmission electron microscopy (HRTEM). It was found that ion track radii depended on specific ionizing energy losses. Amorphous latent tracks in Y2Ti2O7 were found to form both in isolated particles and in those embedded into metallic matrices, whilst tracks in Y4Al2O9 were registered only in isolated nano-oxides .
Study of Residual Stress Profiles in Nitrides (AlN, Si3N4) and Carbides (SiC) Irradiated with High-Energy Ions. A depth-resolved Raman spectroscopy technique was used to study the residual stress profiles in polycrystalline silicon and aluminum nitrides irradiated with high-energy bismuth ions at fluences ranging from 1012 to 1013 cm−2. There was experimental evidence of both compressive and tensile stress fields being formed in the irradiated Si3N4 sample, whereas the residual stress in AlN was registered only at the Bi ion fluence of 1013 cm−2 .
Transmission Electron Microscopy (TEM) Study of Gas Swelling Behavior of Ferritic Steels, Varying with the Structure and Conditions of Their Doping with Inert Gases by Homogeneous Ion Implantation. Using the TEM technique, the regularities in the development of gas porosity were investigated in three samples of ferritic steels: conventional ferritic steel AISI410S and two experimental dispersion strengthened ferritic alloys Сr16-ODS and EP450-ODS. The samples were uniformly doped with helium ions up to the doses of 0.2 and 1 at % and annealed in a vacuum at a temperature of 1023 К. A technique was developed for uniform ion doping of material samples intended for structural studies by TEM. On the basis of theoretical calculations for ion implantation profiles in moving targets, a device with a rotating target was designed and manufactured. The target drive control programme enables the plotting of a resulting ion implantation profile in real time.
Development and Study of Ion-Selective Track Membranes. The detailed studies were conducted on the processes occurring during the irradiation of polyethylene terephthalate films with accelerated heavy ions, their subsequent exposure to ultraviolet radiation and liquid extraction. Such treatment leads to the formation of an ion-conducting cation-selective structure (selective to cations of different charges, too). The ion permeability and selectivity were found to depend on a number of factors, including mutual intersections of tracks, external and internal stresses in the polymer, and electric voltage. A phenomenological model of a resulting structure was proposed whose properties largely corresponded to the heterogeneous ion-exchange membrane [20, 21].
Hydrophobization of Polyethylene Terephthalate Track Membranes by Electron-Beam and Magnetron Sputter Deposition of Polymers onto Their Surfaces with a View to Producing Composite Membranes for Membrane Distillation. Techniques were developed for forming hydrophobic coatings on the surface of the polyethylene terephthalate track membrane by polymerization of organic compounds. The morphology and chemical structure of hydrophobic nanoscale coatings formed by magnetron sputtering of ultra-high-molecular-weight polyethylene and polytetrafluoroethylene in vacuum were also studied. In addition, the FLNR team investigated the physical and chemical properties of nanocoatings formed by electron beam dispersion of 123 polyvinyl chloride in vacuum. A possibility was also investigated of using track membranes with hydrophobized selective layers in seawater desalination by membrane distillation [22, 23].
Characterization and Production of Biodegradable Polymer Nanofibers by Electroforming on the Surface of Metallized Track Membranes for Medical Applications. A wound dressing was developed. The covering represents a perforated polyethylene terephthalate film modified with chitosan nanofibers by electrospinning. Impermeable to water and gas, the new wound dressing has a high tensile strength and elasticity, providing for efficient cell proliferation due to an extracellular matrix-mimicking structure. The composite material is non-toxic and could become a basis for the next generation of wound dressings used in combustiology [24, 25].
Development of Methodological Approaches to the Creation of a Technology for Producing Sterilizing Track Membranes. Approaches were developed to produce a prototype of sterilizing track membranes by creating two arrays of pores in a film whose thickness exceeded the length of the ion path. The prototype is based on a sieving mechanism of separation and sorption of filtered bacterial suspensions. The structural and strength characteristics of experimental and pilot samples of membranes comply with the international norms required for sterilizing membranes. The pilot samples produced by the roll technology were challenged with 107 colony forming units (cfu) of Brevundimonas diminuta (ATCC 19146) per cm2 and demonstrated by testing to produce a sterile filtrate, thus establishing the bacteria retention capability.
X-ray Fluorescence Method and Gamma Activation Analysis Used in the Environmental Impact Assessment of Operational Industrial Facilities, in Particular Coal-Fired Heat and Power Plants (Collaboration with Mongolia). An environmental impact assessment associated with Ulaanbaatar Thermal Power Plant No. 4 was conducted. The concentration of heavy metals and radionuclides in the samples of coal, ash, slag, soil, and plants was estimated using the X-ray fluorescence method, gamma activation and gamma-spectrometer analyses. In addition, the level of heavy metal contamination in soils with regard to the maximum permissible concentration and background content was assessed and the radiation effects on human habitation and the surrounding environment were evaluated .
Expansion of the Fleet of Equipment and Introduction of New Physical and Chemical Investigation Methods (Transmission Electron Microscopy, Thermogravimetry, Measurements of Thermostimulated Currents in Dielectrics). A new Talos F200i transmission electron microscope was launched and used for studying various materials subjected to bombardment with accelerated heavy ions. A differential scanning calorimetry method, a thermally stimulated current technique, and mechanical testing of polymer films were introduced. A set-up for producing nanofibers was launched, and a number of experiments on creating hybrid track membranes and track-membrane-based composites were conducted. Some of the results of novel experimental methods have already been published, and the remainder was prepared for publication.
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