The study of plasma production and heating in the ion cyclotron range of frequencies (ICRF) has a long history in fusion research. The ICRF discharges have been studied in stellarators, tokamaks and mirror devices, mainly. The possibility of efficient additional plasma heating using ICRF is one of the main aims of the studies. Plasma production using ICRF discharges is also studied, but to a lesser extent. For the purpose of wall conditioning in both pure gases and their mixtures has been used with lower RF power level. In support of the ICRF experiments for plasma production at Wendelstein 7-X, studies on the development of an ICRF start-up scenario were initiated on the Uragan-2M (U-2M) stellarator. Experiments with a controlled minority of hydrogen in helium atmosphere showed a significant increase in the resulting plasma density compared with pure helium and pure hydrogen. Then, the ICRF plasma production was demonstrated on the LHD with the scenario based on U-2M experiment. Successful experiments at U-2M and LHD showed that the ICRF start-up scenario can be scaled up to large stellarator devices, producing plasma with favorable parameters from scratch using ICRF only.

Tantalum nitride (TaN) and tantalum oxide (Ta2O5) coatings were manufactured by using sputtering with sustained gas discharge in Bulat-type facility. Characteristics of the obtained coatings, including surface morphology, nanohardness, surface wettability, Young's modulus, and biocompatibility, were investigated. Different surface roughness of TaN and Ta2O5 made the main contribution to the transition to hydrophobic surface properties, which led to different conditions for cell adhesion. According to the test results, the average value of the elastic modulus for the sample coated with TaN was 426.1 GPa and Ta2O5 - 172.4 GPa, respectively. The maximum nanohardness was obtained for the TaN nitride coating and reached 37.8 GPa. The biocompatibility of the samples was assessed in vitro by the susceptibility of the surface of the material to cells, since cell attachment and proliferation are closely related to the surface characteristics of the implant. The Ta2O5 coating has shown appropriate biocompatibility profile, as it provides an ideal environment for Mesenchimal Stem Cells (MSC) adhesion from day 1, followed by cell proliferation until the end of the experiment. The TaN coating did not support cell attachment and proliferation during the experiment.

Quasistationary plasma accelerators (QSPAs) can be used for diverse applications, including plasmasurface interaction experiments in the conditions close to the fusion reactor transient events (e.g., current disruptions, VDE, and giant ELMs), modifying material surfaces, and creating new surface alloys [1]. A magnetoplasma compressor (MPC), a QSPA-type device capable of generating pinching plasma streams with densities up to $10^{19}-10^{20} \mathrm{~cm}^{-3}$, can be further enhanced by applying an additional magnetic field, opening the possibility for improved discharge characteristics and plasma parameters [2]. The influence of an external magnetic field in the discharge channel of the MPC on the plasma stream dynamics was studied. The complex structure of the plasma stream undergoes significant changes when exposed to an external magnetic field: the magnitude of the electric potential and current increases, fewer current vortices tend to form. The external magnetic field improves the compression characteristics of the plasma flow, in particular, it increases the compression zone size and radial component of the $\mathrm{J} \times \mathrm{B}$ force. Introducing a magnetic field causes the current-sheet-like structure found in our recent research [2] to form earlier. These results significantly expand the range of possible applications of the device.

The experiments on medium-size stellarator Uragan-2M (U-2M) in Kharkiv, Ukraine, are carried on in support of the Wendelstein 7-X (W7-X) experimental program. The scenario ion cyclotron frequency range (ICRF) plasma production at the hydrogen minority regime had been experimentally tested on U-2M and was qualified at the Large Helical Device (LHD). The paper presents the results of further research on the ICRF plasma production. The ICRF discharge studies were carried out in a H2 + He mixture with a controlled hydrogen concentration ranging from few percents to 75%. The two-strap like antenna mimicks the W7-X antenna operated in monopole phasing. The applied RF power was in the range of ∼100 kW. Relatively dense plasma of up to Ne ∼ 1019 m−3 was produced near the first harmonic of the hydrogen cyclotron frequency. The maximum temperature of the electrons and ions was not more than a few tens of electron volt. The characteristic features of RF plasma production and the propagation of electromagnetic waves in the experimental conditions are discussed. The experiments on U-2M and LHD indicate that the minority scenario of ICRF plasma production appears to be scalable and could be used in large stellarator machines. This is, in particular, important for the future experiments ICRF production of target plasma in W-7X in conditions where electron cyclotron resonance heating start-up is not possible.

The results of vacuum-arc deposition of thin bilayer ZrTa/ZrTaO2 coatings on the surface of titanium dental implants, AISI-316L stainless steel are presented. The structure, phase and chemical composition of deposited coatings have been investigated by means of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and X-ray diffraction analysis XRD. Nanomechanical properties have been investigated by nanoindentation method. The obtained results can be useful for optimization of implant surfaces to prevent corrosion and mechanical failure, thereby improving osseointegration.

The impact of an external longitudinal magnetic field on a self-compressed quasi-stationary plasma flow generated by a high-current magnetoplasma compressor is studied. The additional magnetic field of 0.24 T was applied to the plasma discharge. A significant enhancement of flow compression when an external longitudinal magnetic field is applied was found. The magnetic field also influences the process of current vortices formation, which is linked to the conversion of kinetic energy into magnetic field energy. The formation of fewer vortices inthe presence of the magnetic field suggests more efficient compression and potentially higher plasma parameters in the compression zone.

This paper presents the results of fabricating a model sample of a multilayer coating on a Al2O3 substrate, which consisted of 30 periods of alternately deposited 10.5-nm-thick layers of Ti41Zr41Ni18 and 2.5-nm-thick layers of W. The effect of annealing for 1 h at 500, 600, and 700 °C was studied. Characterization of the phase and structural state of the coating by X-ray diffractometry and small-angle X-ray reflectometry was carried out. It was found that during the annealing process, the tungsten layers in the multilayer composition did not undergo significant changes, and all alterations occur only in the Ti41Zr41Ni18 layers. Annealing affected the thickness of the layers, density, and interlayer roughness. It has been experimentally shown that the phase transformation ”quasicrystal → 2/1 crystalline approximant” is accompanied by an 8.3% volume increase compared to the volume of the quasicrystalline phase, but this does not lead to the destruction of the periodic composition. The multilayer structure proved to be resistant to high temperatures and, despite phase changes, did not lose its bond with the substrate. The used combination of materials and the high annealing temperature did not generate significant internal stresses or mechanical damage. The results obtained in this study allow for the further controlled formation of layered quasicrystal/tungsten microsystems of various designs with different layer thicknesses. The next perspective involves conducting practical tests with plasma to study the radiation-thermal impact.

A 3D-printed tungsten Sn Capillary Porous Structure (CPS) sample was exposed to oblique high-power plasma in the QSPA facility. The experiment aimed to analyze the damage to a liquid metal prototype, a potential component of the divertor in fusion tokamaks. Observations of plasma-surface interactions revealed particle ejection from the exposed target, which depended on the energy density of the incoming plasma stream. The leading edge of the CPS sample was identified as the primary source of the ejected particles. A reduction in mass loss rate of the plasma-treated sample over the course of the experimental series was demonstrated. The W substrate of the CPS target did not sustain significant damage. A comparative analysis of the damage to Sn-CPS and castellated W samples exposed to inclined and normal plasma streams under conditions simulating transients in a fusion reactor was also performed.

Recently, experiments on basic plasma physics issues for solving future problems in fusion energy have been performed on a Large Helical Device. There are several problems to be solved in future devices for fusion energy. Emerging issues in burning plasma are: alpha-channeling (ion heating by alpha particles), turbulence and transport in electron dominant heating helium ash exhaust, reduction of the divertor heat load. To solve these problems, understanding the basic plasma physics of (1) wave–particle interaction through (inverse) Landau damping, (2) characteristics of electron-scale (high- k ) turbulence, (3) ion mixing and the isotope effect, and (4) turbulence spreading and detachment, is necessary. This overview discusses the experimental studies on these issues and turbulent transport in multi-ion plasma and other issues in the appendix.

An ozone destructor for a plasma ozone sterilizer has been developed. This is an improved model of an ozone destructor, consisting of two parts, which significantly increases the contact area of activated carbon with ozone. This destructor design is suitable for ozone concentrations of 100…120 mg/l at an oxygen flow rate of 1 l/min. A study was conducted to determine the dependence of the temperature of carbon at the contact point with ozone depending on the amount of decomposed ozone at various oxygen flow rate. It was monitored that output ozone did not exceed the maximum permissible concentration in the working area proving the effectiveness of the developed ozone destructor.

The work presents some experimental results obtained in the new module construction of an electrolyzer with tube electrodes: mass spectra of the mixtures of gases, generated during electrolysis, volt-ampere characteristics, etc. It has been shown that at electrolytes (H2O + 1 wt.% NaHCO3, H2O + 1 wt.% Na2CO3) temperature of ~ 50 °C and a pressure in the electrolyzer chamber of ~ 2 atm, the generated gas is 92 vol.% consists of hydrogen. Estimations show from two to four times (in dependence on electrolyte composition) higher effectiveness of converting electri-cal energy into the amount of electrolysis gas for new electrolysis setup construction compared to the previous ver-sion.

The paper presents experimental studies of a shielding plasma layer formation in front of a tungsten surface exposed with hydrogen plasma in the QSPA-M test-bed facility under the conditions of additional seeding of argon (Ar) along the target surface into the zone of plasma-surface interaction. A pulsed gas injector on the base of a fast electromagnetic valve has been developed for the local injection of Ar. The injector is capable of generating a homogeneous argon gas flow with a maximum concentration above n _Ar = 6 × 10 ^23 m ^−3 and a pulse duration of 0.5 ms. It is shown that the increase in the argon gas density in front of the surface leads to an essential decrease (in 1.5–2 times) in the energy load delivered to the target surface. In the presence of a strong magnetic field (up to 1 T), both the thickness of the shielding layer and the fraction of energy dissipated by the shield increase further. Even for moderate energy densities of the QSPA plasma streams in the experiments with Ar gas injection, less than 40% of the impacting plasma load is absorbed by the tungsten surface. The results demonstrate that this additional shielding attributed to the formation of a dense Ar plasma layer in front of the exposed W surface would be favourable for the divertor armour performance, causing the decreasing erosion of plasma-facing components in the course of transient events in a fusion reactor.

The influence of the external axial magnetic field on pinching plasma flows generated by a magnetoplasma compressor (MPC) has been studied using magnetic and electric probes. In the presence of an external magnetic field, temperature measurements show two groups of electrons with different temperatures near the plasma stream core. The external magnetic field leads to a noticeable increase in the electric current in the plasma stream, electron temperature, and the formation of the current-sheet-like structure observed in the MPC for the first time.

The programmable controller for ozone-plasma sterilizer for programmatic operation of the units and continuous monitoring of the sterilization process has been developed. The design of the controller is based on the model of the PIC18F series microcontroller of the XLP family. The software that ensures the operation of the plasma sterilizer (control and monitoring of parameters) is written in a specialized C++ software in the MPLAB IDE processing environment under the Windows 10 operating system.

The surface modification of advanced materials was studied through a series of repetitive plasma pulses caused tungsten melting. Features of the affected surface layers in reference materials (IGP W, AM W/WTa, Hastelloy, and EUROFER) for both fusion and fission applications were explored after exposure to plasma in the facilities (QSPA, MPC, and PPA) with different durations of plasma pulses. A detailed surface analysis was carried out with Scanning Electron Microscopy. It was found that the plasma treatment led to the formation of a modified layer as a result of the rapid re-solidification of the exposed surface. The fine cellular structures appeared in the re-solidified layers of the irradiated materials, with typical cell sizes ranging from 150 to 500 nm. An increase in the roughness of the exposed surfaces was attributed to the presence of the cracks and re-solidified layer.

The multiple-recycle fuel cycle for uranium-238 considered here, if practically realized, can bring revolutionary changes in nuclear energy. A full use of uranium-238 implies a practically infinite resource for power generation. Besides the energy, the fuel cycle net output is only fission products, which are co-products rather than waste. For the same amount of energy produced, the amount of fission products is two orders of magnitude less compared with the amount of spent nuclear fuel generated in currently exploited nuclear energy production scenarios. Using the simplest isotope balance model, key features of the multiple-recycle fuel cycle for uranium-238 are investigated. The repetition of this cycle results in smooth transformation of the initial fuel to ‘stationary’ fuel without strong variations in the fractional isotope content. Deficit of delayed neutrons is a threat of the fuel cycle considered as well as other fuel cycles that use plutonium. It has a dramatic impact on reactor controllability and safety. A solution to this threat could be a subcritical nuclear reactor with an external neutron source. In this paper, use of a stellarator–mirror (SM) fusion–fission hybrid for the multiple-recycle fuel cycle for uranium-238 is analysed. A summary of the experimental and theoretical studies on the SM hybrid is given. Preliminary results for principal design of a SM hybrid nuclear reactor for the multiple-recycle fuel cycle for uranium-238 are presented.

The nanocrystalline films of zirconium nitride have been synthesized using ion-plasma vacuum-arc deposition technique on pure Ti-6Al-4V, whereas the hydroxyapatite coatings were deposited by the method of plasmaelectrolytic oxidation in alkaline electrolytes (hydroxyapatite + 1 М potassium hydroxide). Structure evaluation by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) with microanalysis (EDS) – were performed to study phase and chemical composition, surface morphology, microstructure of coatings. The formed HA PEO coatings with spheroidal structure contain the phases of CaTiO3 calcium titanate, CaHPO4 anhydrous dicalcium phosphate, and Ca10(PO4)6(OH)2 hydroxyapatite. It was revealed that ZrN single-phase coatings of cubic modification with finecrystalline grains of 20 nm in size were formed. This experimental study found that coating Ti-6Al-4V with ZrN and HA positively influences preosteoblast cell adhesion, which results in the almost complete coverage of the surface, along with a less number of cells grown on uncoated titanium surface.

The plasma energy transfer to plasma-facing materials, as well as the energy and particles exhaust, needs to be extensively studied for the implementation of the next-step fusion reactor project. Analysis of plasma-surface interaction features has been performed using QSPA exposures of reference plasma-facing materials. The parameters of the plasma streams imitated conditions of transient events in a fusion reactor. The influence of an external magnetic field on the energy balance during the plasma-surface interaction is also discussed.

Herein we report the results of multi-element nitride and intermetallic coatings obtained by the arc-PVD method based on non-trivial elements combinations (Nb - 75.5, Si - 9.65, Cu - 14.85 at% and Ti - 81.8, Nb - 11.8, Al - 6.4 at%). Our experiments examine the development and evolution of biocompatible coatings for metal implants and medical devices. The elemental composition of the surface, microstructure, contact angle and biocompatibility of the coatings were studied. XRD results demonstrated that in the intermetallic TiAlNb samples, a multiphase state is formed between gamma-TiAl, TiAl2, and alpha-Nb5Si3, since only a small part of Nb atoms occupy the same lattice sites as Ti atoms, which leads to the formation of a competing phase alpha-Nb5Si3. The NbCuSi coatings predominantly consist of Nbss with inclusions of silicon silicide. The human umbilical cord mesenchymal stem cells (MSC) were used for biocompatibility assessment using resazurin reduction assay and fluorescent DAPI staining. We show the high biocompatibility and ability to stimulate cell proliferation and distribution over the intermetallic coatings, especially when compared to nitrides ones. Although intermetallic coatings exhibit a higher surface contact angle due to uneven morphology, all samples exhibit hydrophilic properties, which favourably affect cell adhesion and proliferation.

The work presents a setup scheme for studying the processes of hydrogen generation and analysis of its penetration through diffusion-catalytic membranes directly during the electrolysis process, as well as first experimental results obtained when testing this setup (volt-ampere characteristics, mass spectra of the mixtures of gases, generated during electrolysis, etc.).