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Abstract Among the peripheral instabilities observed at the Globus-M2 tokamak, two types of edge localized modes (ELMs) are brought into focus: ELMs synchronized and desynchronized with the sawtooth oscillations. The desynchronized ELMs appear in regimes that are characterized by high values of pressure in the pedestal, pped ≥ 3 kPa, and they are observed in discharges with the toroidal magnetic field BT > 0.6 T and plasma current IP > 0.3 MA. The desynchronized ELMs belong to the type-III/V with the dominating effect of the peeling mode. The synchronized ELMs were observed in a wider range of discharge parameters, including at BT < 0.6 T and IP < 0.3 MA. Calculations of the stability of the peeling-ballooning (PB) mode showed that at pedestal width ψnorm = 0.09 and pped > 3.5 kPa, destabilization of PB modes is possible without additional influence. Experimental data shows that the microtearing mode plays a dominant role in the pedestal. The microtearing mode does not allow the pedestal at Globus-M2 tokamak to reach the state of the unstable kinetic ballooning mode (KBM), which explains the low predictive power of the EPED model at this tokamak.

Abstract NBI-assisted plasma heating with one or two injectors of fast neutral atoms was studied at the Globus-M2 spherical tokamak at the toroidal magnetic fields of 0.8–0.9 T and plasma currents of 0.35–0.4 MA. Measurements of the spatial temperature and electron density distributions, performed using the Thomson scattering diagnostics, showed a twofold increase in heating of plasma electrons during the injection of neutral particles with energies of up to 45 keV at the beam power of 0.75 MW, as compared to the ohmic heating regime. Switching on the second additional beam with the particle energy of up to 30 keV and power of up to 0.5 MW resulted in obtaining the hot ion mode in the range of mean plasma densities of (1.6–10) × 1019 m−3. According to the data of active spectroscopy and neutral particle analyzer diagnostics, in the hot zone, the ion temperature reached 4 keV at the plasma density of 8 × 1019 m−3, which is more than 2.5 times higher than the electron temperature.

The present work was aimed at the investigation of effect of High Energy Ball Milling (HEBM) time on the sintering kinetics, structure, and properties of heavy tungsten alloy (HTA) W-7%Ni-3%Fe. The HTA samples were obtained from the nanopowders (20-80 nm) by conventional liquid phase sintering (LPS) in hydrogen and by Spark Plasma Sintering (SPS) in vacuum. The HTA density was shown to depend on the HEBM time non-monotonously that originates from the formation of non-equilibrium solid solutions in the W-Ni-Fe systems during HEBM. The SPS kinetics of the HTA nanopowders was shown to have a two-stage character, the intensity of which depends on the Coble diffusion creep rate and on the intensity of diffusion of the tungsten atoms in the crystal lattice of the -phase. The kinetics of sintering of the initial submicron powders have a single-stage character originating from the intensity of the grain boundary diffusion in the -phase. The dependencies of the hardness and of the yield strength on the grain sizes were found to obey the Hall-Petch relation. The hardness, strength, and dynamic strength in the compression tests of the fine-grained tungsten alloys obtained by SPS and LPS were studied.

Studies were performed on the possibility of using the coaxial plasma jet accelerator to facilitate breakdown and the plasma current start-up in the Globus-M2 and KTM tokamaks. The results of experiments on the jet injection into the Globus-M2 tokamak with a magnetic field of 0.7 T showed that the discharge current rise began 1–2 ms earlier than it did in experiments using gas puffing and inductive breakdown of the working gas. In this case, the breakdown voltage decreased approximately 2 times. The results of experiments on plasma jet injection through the equatorial diagnostic duct into the KTM tokamak with a magnetic field of 0.9 T showed that the gas breakdown occurred up to 6 ms earlier than the breakdown initiated using the inductive method. In this case, the loop voltage decreases approximately 1.5 times. In almost all shots using the accelerator, the gas breakdown occurred, while in its absence, sometimes the gas breakdown could not be obtained.

A new model that describes primary recrystallization in metals has been proposed. This model determines the rate of recrystallization nucleus growth in terms of the kinetics of the decreasing power of disclination dipoles distributed within nucleus boundaries. The equation relating the volume fraction of recrystallized material to the temperature and annealing time has been derived. This equation has the form of the Avrami equation at n = 1 and an activation energy of diffusion along nonequilibrium grain boundaries.

The Y0.95Gd0.05PO4 phosphate with the xenotime structure has been synthesized in powder form and as ceramics. Ceramics with a relative density of ~99% have been produced by spark plasma sintering. The sintering temperature was 1140°C and the sintering time was ~18 min, without isothermal holding. We have assessed the radiation resistance of the ceramics under irradiation with 132Xe26+ ions and investigated the restoration of the obtained metamict phase to a crystalline one via high-temperature heat treatment. No complete amorphization of the samples has been reached at the fluences used in this study. The calculated critical fluence is (9.2 ± 0.1) × 1014 cm–2, and the calculated latent track radius is ~2.8 nm. Hydrolytic tests have shown that the phosphate under study is stable in water under dynamic conditions. The observed Y and Gd leaching rates were Ri = 1.68 × 10–6 and 1.5 × 10–7 g/(cm2 day), respectively.

An array of ten built-in divertor probes was installed on the lower dome of the Globus-M spherical tokamak. It was used to measure the profiles of the floating potential, electron temperature, ion saturation current, and heat flux density to the divertor. It is demonstrated that there is a sharp change in the floating potentials of the probes located near the outer separatrix leg at the development of the peripheral instability.

The article presents the results of studying the transfer of heat and particles in the Globus-M2 spherical tokamak in discharges with neutral injection at the current ramp up. An atomic beam was injected into the tokamak plasma at a fixed toroidal magnetic field of 0.7 T. The plasma current on the plateau was varied in the range 0.2–0.3 MA. Based on the electron temperature and concentration spatial distributions measured by the Thomson scattering method, the transport of heat and particles in plasma was simulated using the ASTRA code. The energy confinement time of the plasma was determined, as well as estimates of the coefficients of thermal diffusivity and diffusion was made.

Two different types of MHD instabilities with rapidly chirping frequency were found to arise in the Globus-M2 spherical tokamak in substantially different frequency ranges. The first type arises at frequencies of an order of 1 MHz in ohmic plasmas at relatively low density 〈 n e 〉 < 2 × 10 19 m − 3 in a wide range of toroidal magnetic fields and plasma currents. This type of instability was identified as compressional Alfvén waves, driven by electrons, accelerated during a sawtooth crush. It was found that the mode frequency is sweeping in time, according to the Berk–Breizman hole–clump nonlinear chirping model. The second type of wave arises in a specific single-swing regime of the central solenoid current with a very narrow plasma column, when the plasma tends to decay at extremely low density 〈 n e 〉 < 2 × 10 18 m − 3 and, in fact, is an instability of the runaway electron beam. The exited modes cover the whole observed frequency range and are divided into several (two or three) frequency regions: approximately 0–30 MHz, 60–120 MHz and sometimes 30–60 MHz. Reconnection of the branches was also observed. Single chirps are more rapid than for 1 MHz Alfvén instability and follow an exponential law. This paper, to our knowledge, is the first report of frequency chirping instabilities excited by accelerated electrons at a spherical tokamak.

In this Letter, results of measurements of radiation losses Prad and effective ion charge Zeff in the conditions of magnetic field up to 0.7 T and plasma current up to 300 kA for a wide range of electron density first obtained on the Globus-M2 tokamak are presented. The analysis of the results shows the decrease in the radiation losses share of the input power on the Globus-M2 tokamak as compared with the same parameter for the Globus-M facility. A large dip at the center of the Prad power profiles is revealed. A decrease in the Zeff values is observed with an increase in electron density.

On the spherical tokamak Globus-M2 in discharges with toroidal magnetic field of 0.7 T by means of magnetic probes and a number of other diagnostics during neutral beam injection at the current ramp up stage, magnetic field oscillations in the range of 100–300 kHz having their frequency increasing in time, had been observed. Eigenmodes with wavenumbers n = 1–3 and m = 2–4 were being registered. These oscillations were identified as Alfven cascades. By means of multi-channel fluctuation reflectometer, observed eigenmodes were found to be localized near the magnetic shear reversal radius. Application of MHD-spectroscopy technique allowed us to determine safety factor temporal evolution and experimental values are in well agreement with modelling results, provided by ASTRA transport code.

The Alfven oscillations were studied using the multifrequency Doppler backscattering (DBS) method on the Globus-M spherical tokamak during the neutral deuterium injection. The principles of Alfven mode registration by the DBS method are discussed. Microwave schemes of multifrequency probing are described. It is shown that the observed plasma rotation velocity oscillations are due to the oscillations of the drift velocity in crossed radial electric field of the Alfven wave and the magnetic field. The absolute values of the magnetic field perturbations of the toroidal Alfven eigenmode (TAE) in the internal regions of the tokamak discharge are determined. The obtained data are compared with the results of the magnetic field oscillations measurements obtained by a magnetic probe located outside the plasma region. The use of multifrequency probing in the DBS method made it possible to determine the radial distributions of the amplitude of magnetic field oscillations. These data were obtained for oscillations at the TAE fundamental frequency and at harmonic frequencies, which were found to correspond to different toroidal mode numbers. In general, the data obtained can be compared with the results of numerical modeling of the Alfven spectrum in the Globus-M tokamak. The prospects for the further use of the DBS method for studying Alfven oscillations in toroidal installations are discussed.

High-density (95.3–95.8%) CeO2–xα-SiC (x = 10, 20 vol %) composite ceramics have been produced for the first time by spark plasma sintering (SPS) as promising mineral-like materials for inert fuel matrices. The SPS of CeO2–SiC ceramics has been shown to be a three-stage process. The addition of α-SiC particles shifts characteristic temperatures of CeO2 sintering to higher values. SPS leads to an increase in the hardness, fracture toughness, and thermal conductivity of cerium dioxide-based ceramics.

Globus-M2—a new 1-Tesla spherical tokamak—was recently launched. The main features and research directions of this machine in scope of fusion–fission reactor development are described. Main results of the first experimental campaign with toroidal magnetic field up to 0.73 T and plasma current up to 0.33 MA are discussed. Significant improvement of the discharge parameters as compared to Globus-M was achieved. Plasma total stored energy higher than 7 kJ was obtained. Energy confinement time increase was consistent with predictions by spherical tokamak scalings. Toroidal Alfven eigenmode-induced losses decrease with increase of plasma current and toroidal magnetic field. For the first time, LHCD with the toroidal wave slowing-down was successfully used at a spherical tokamak.

International audience; It is recognized that the filaments have a significant effect on the anomalous energy and particle transport in the tokamak periphery. They are actively investigated using various diagnostics in this regard. Recently studies of filaments using the Doppler backscattering (DBS) method have been performed in the Globus-M and the ASDEX-Upgrade tokamaks. Backscattering from filaments manifests itself as a burst of quasi-coherent fluctuations (BQF) of the signals of IQ detectors. Such signals are easy to describe in the Born approximation using the diagnostic weighting function. However, the filaments in tokamaks differ noticeably in their size and intensity. With an increase in the amplitude of the filaments, it is necessary to consider the transition from linear scattering to nonlinear one and further up to the transition from backscattering to reflection from a moving over dens filament. This problem can be solved only using a full wave code. Our simulation was carried out using the finite-difference time-domain code IPF-FD3D in slab geometry. We did not resort to using well-known non-linear MHD codes to determine filament parameters. In the simulation artificial filament-like perturbations were used, the parameters of which varied over a wide range. Modeling DBS signal was focused on the identification of the influence of the amplitude of the filament and its size on the shape and the size of the DBS output signal. The results obtained largely explain the similarity of the IQ detector data registered in different tokamaks.

A method of plasma boundary location based on last closed magnetic surface position detection as a maximum of electrostatic potential measured using Langmuir probes is presented. It is demonstrated that the method can be used for an absolute calibration of magnetic diagnostics of plasma position (TUMAN-3M) and as an independent diagnostic tool (Globus-M).

Results of experimental studies of toroidal Alfven eigenmodes (TAEs) in the Globus-M spherical tokamak (R = 36 cm, a = 24 cm) are reported. The experiments were carried out in a wide range of plasma parameters at a magnetic field of up to 0.5 T and plasma current of up to 250 kA. Auxiliary plasma heating was performed by tangential injection of a deuterium beam with a power of Pb= 0.75 MW and particle energy of Eb = 28 keV into deuterium plasma. The experiments have shown that the TAE-induced loss of fast particles decreases with increasing plasma current and magnetic field. Using multifrequency Doppler backscattering diagnostics, it is established that the TAEs are localized at the plasma periphery. Results of simulations of the Alfven continuum and TAE structure by means of the modified KINX and CAXE codes agree satisfactory with the experimental data on the TAE frequencies and localization.

The dynamic strength of heavy 90W—7Ni—3Fe alloy (wt %) was studied on two types of specimens: formed from submicron powder by spark plasma sintering (SPS) and from coarse-grained powder with a particle size of ≈20 µm by standard liquid phase sintering (LPS). Mhe study shows that the dynamic strength of the LPS and SPS specimens ranges up to 2750 and 3150 MPa, respectively, and that the SPS projectiles at an impact velocity of 1200 m/s penetrate 60% deeper into a steel target than the LPS projectiles. The difference in the penetration depth results from different penetration mechanisms: piercing for the coarse-grained material and cratering for the fine-grained one.

The results of experiments and simulations of the transport of heat and particles in the Globus-M spherical tokamak are presented. Investigations were carried out in the ohmic mode in hydrogen and deuterium plasma. It is shown that in the phase of current growth under the same initial conditions, as long as the condition is met at which the minimum of the safety factor exceeds unity, two scenarios of discharge development are possible: with an electron temperature dive or with an electron density peak. After the safety factor reaches the value of 1, the differences are no longer observed. Modeling of transport processes using the ASTRA code showed that the dive of the electron temperature and density is a consequence of the decrease in the transport of heat and particles in the plasma core (i.e., the presence of internal transport barriers).

Applicability of Spark Plasma Sintering has been studied for production of high-density (98.6–99.5%) composite ceramics Y2.5Nd0.5Al5O12 (YAG:Nd) – x MgO (x = 5, 10, 20 vol %). Powder YAG:Nd-MgO compositions have been obtained by precipitation of the MgO phase from Mg(NO3)2 water solution of magnesium nitrate onto the surface of garnet nanoparticles YAG:Nd. It has been demonstrated that the intensity of sintering fine-grained YAG:Nd-MgO composites is governed by volume diffusion at low temperatures and by grain boundary diffusion at high temperatures. Faster sintering at low temperatures is caused by formation of MgAl2O4 spinel particles and internal stress fields that are manifested as broadening and shifting of garnet peaks in the sintered composites.

Fine-grained SrWO4 and NaNd(WO4)2 ceramics with the scheelite structure having high relative densities (99 and 95.8%), which can appear candidate matrices for radioactive waste (RAW) management, are prepared by spark plasma sintering (SPS). The phase identity of the ceramics is determined by X-ray powder diffraction; their microstructure is studied by X-ray photoelectron spectroscopy. The tungstates under study are sintered at rather low temperatures (580–665°C). The intensity of compaction of the tungstates at the early sintering stage is determined by the degree of powder agglomeration. The activation energy of fine-grained scheelite ceramics at high temperatures corresponds with the activation energy of grain-boundary oxygen diffusion.

Spark Plasma Sintering has been used to obtain first ever fine-grained SrWO4 and NaNd(WO4)2 ceramics with the scheelite structure and high density (95.8–99%) that are promising as materials for nuclear waste immobilization. It has been demonstrated that the densification intensity in tungstates at the initial sintering stage is determined by the agglomeration degree of input powders. The activation energy of fine-grained ceramics with the scheelite structure has been established to correlate at high temperatures with the activation energy of grain-boundary diffusion. Rapid sintering of fine-grained NaNd(WO4)2 ceramic results in internal tensile stress fields that lead to lowered hardness and fracture toughness of the ceramic.

This paper is a study of sintering mechanisms, structure, and mechanical properties of ultrafine-grained 95W-Ni-Fe tungsten heavy alloys. Powder particle sizes were controlled by mechanical activation (MA) of original coarse-grained components and by addition of ultrafine particles. W-Ni-Fe alloys were obtained by sintering in hydrogen and Spark Plasma Sintering (SPS) in a vacuum. The dependence of ultrafine-grained (UFG) alloy density on sintering temperatures has been found to be non-monotonic with a maximum corresponding to the optimal sintering temperature. It has been demonstrated that the sintering activation energy of UFG alloys is significantly lower than that of coarse-grained alloys. It has been shown that the optimal SPS temperature for mechanically activated nanopowders goes down by 350–400 °C in comparison with the optimal sintering temperature in hydrogen for coarse-grained 95W-Ni-Fe powder composition. The reason for a lower optimal sintering temperature lies in a decreased activation energy of grain-boundary diffusion and formation of a non-equilibrium solid solution of nickel and iron in the surface layer of tungsten α-W particles during high-energy MA. High-energy MA and SPS were used to obtain samples of UFG tungsten alloys with high mechanical properties: macro-elastic limit – up to 2250 MPa, yield stress – up to 2500 MPa.

Powders of garnet-type complex oxide Y2.5Nd0.5Al5O12 (YAG:Nd) – x vol% W, Mo (x = 0, 10, 20) were obtained using wet chemistry techniques and precipitation of the metal phase from salt solutions. After synthesis, nanoparticles of YAG:Nd garnet cluster into submicron agglomerates. Spark Plasma Sintering (SPS) was used to obtain fine-grain ceramic-metal composites YAG:Nd – (W, Mo) with a relative density of ∼99%. The effect that metal concentration (tungsten, molybdenum) has on density, microstructure properties, and mechanical properties (microhardness, fracture toughness) of ceramics was studied. SPS activation energies were determined and it was demonstrated that the intensity of shrinkage of the fine-grained YAG:Nd – (W,Mo) ceramic-metal composites close to the activation energy of creep in tungsten (molybdenum). It has been demonstrated that the intensity of creep during SPS of fine-grained composites at medium temperatures is determined by the intensity of volume oxygen diffusion in the lattice of garnet nanoparticles, whereas at high temperatures it is determined by grain-boundary diffusion.

The local measurements of electron density and temperature by Thomson scattering (TS) diagnostics are essential for research of energy confinement, plasma heating, and control at nuclear fusion devices. This paper presents a digital filter polychromator designed for TS spectrum registration. A distinguishing feature of such a digital polychromator is the use of an analog-to-digital converter (ADC) having analog memory with discretization frequency of 5 GHz and 12-bit sampling. The low heat dissipation and compact design of the ADC allow us to integrate the recording and data handling systems in the spectral unit to obtain a standalone device that is totally isolated from other systems and equipment in the voltaic sense. The scattered laser radiation received from the plasma comes to the entrance of the polychromator through a fiber-optic cable, and the processed scattering signals and calculated electron density and temperature are available on a digital interface. The polychromator was tested within the Thomson scattering system at the Globus-M tokamak using two probing lasers: Nd:YAG 1064 nm and Nd:Glass 1055 nm operating with pulse energy up to 2J and FWHM of 4 and 40 ns, respectively. The employed ADCs allowed us to perform superfast signal digitizing in the oscilloscope mode and to demonstrate the possibility of stray signal time separation despite the modest size (~1 m) of the vacuum chamber. The results of measurements performed during the plasma experiment at the Globus-M tokamak are presented, and their comparative analysis with the data obtained at the operating TS system is made.

We have studied the feasibility of preparing high-density (98.6–99.5%) Y2.5Nd0.5Al5O12 (YAG)–xMgO (x = 5, 10, 20 vol %) composite ceramics by spark plasma sintering. YAG–MgO powder materials have been prepared via MgO precipitation from an aqueous solution of magnesium nitrate, Mg(NO3)2, on the surface of garnet particles. The sintering rate of the YAG–MgO composites has been shown to be controlled by volume diffusion at low temperatures and by grain-boundary diffusion at elevated temperatures.

Fine-grained ceramics based on solid solutions of ZrO2-x-Ln2O3 (where Ln = Sm, Yb), which are used to simulate inert matrix fuel (IMF), were obtained by colloidal chemical synthesis of powders and their Spark Plasma Sintering (SPS). It has been established that the SPS activation energy (Qs) for fine-grain ceramics based on ZrO2 corresponds to the activation energy of oxygen diffusion on grain boundaries of zirconium oxide (zirconia). We have demonstrated that introducing oxides of samarium (Sm2O3) and ytterbium (Yb2O3) into zirconia decreases SPS activation energy and stabilizes the phase composition of zirconia. Ceramics with densities up to 100% were obtained by the following modes of SPS: sintering temperature 1000–1250 °C, sintering time 6–10 min. Hydrolysis testing in the static mode (Т = 20 °C, P = 1 atm) in distilled water revealed no leaching of lanthanide ions at detection thresholds of 5 ppm for Sm ions and 0.1 ppm for Yb ions.

Using wet chemistry techniques, ultrafine powders of complex oxides Y2.5Nd0.5Al5O12 (YAG) have been obtained with the garnet structure and coated with layers of nickel by means of precipitation from salt solutions. Spark Plasma Sintering (SPS) was used to obtain fine-grain ceramic composites YAG – Ni with 92–99% density. Sintering activation energies were determined and it was demonstrated that the intensity of high-rate sintering of the investigated ceramic composites is determined by the intensity of the nickel creep at lower heating temperatures, the intensity of oxygen diffusion in the garnet crystal lattice at average SPS temperatures, and the intensity of grain boundary diffusion at high SPS temperatures.

Experiments intended to study the dependence of the ion temperature on the plasma current were carried out on the Globus-M spherical tokamak. The ion temperature was measured at a few spatial points with the help of charge exchange spectroscopy and a charge exchange atom analyzer. On the basis of the experimental data, modeling with the use of the ASTRA numerical code was carried out and the thermal diffusivities for the ion plasma component were determined. The calculation results show that the ion behavior is similar to neoclassical.

The paper presents a method for manufacturing mechanically strong sputtering composite targets containing the phase of the Co2FeSi or Co2MnSi Heusler alloy of the stoichiometric composition, which can be used for fabrication of spin electronic devices by high-frequency magnetron deposition and pulsed laser deposition of thin films.

Spark Plasma Sintering (SPS) has been used to produce samples of fine-grained composites Y2.5Nd0.5Al5O12 + x wt.% α-SiC (x = 1020) with ∼98–99% density. The microstructure of the composites has been studied, as well as the impact of α-SiC particles on the mechanical properties and kinetics of composite sintering. The introduction of the α-SiC part has been demonstrated to form a more fine-grained structure and under the given SPS conditions change the sintering mechanism in ceramics. The study has also demonstrated that introduction of α-SiC particles into garnet results in formation of internal stress fields, which, in turn, leads to a decrease in the activation energy of sintering of fine-grained composites at high temperatures.

Mineral-like matrix Na x (Ca/Sr) 1-2x Nd x WO 4 ( x = 0, 0.1 and 0.2) for radwaste is proposed. Powder samples of complex tungstates have been synthesized by coprecipitation from aqueous solutions of Na, Ca, Sr, Nd salts. Crystallographic characteristics of compounds have been calculated and a monotonous change observed in them along with some x value changes. Monophasic ceramics with high relative density (97–100%) from these powders have been obtained through Spark Plasma Sintering (SPS). SPS of tungstates has been shown to occur in multiple stages, with the sintering kinetics at the final stage of sealing controlled by diffusion both in the crystal lattice and along grain boundaries. Activation energies have been determined for sintering of tungstates at different x values. The reduced activation energy of sintering at the third heating stage (at high temperatures) could be ascribed to the grain growth.

The work presents the results of the energy confinement study carried out on the compact spherical tokamak Globus-M2 with a toroidal magnetic field as high as 0.8 T. A reproducible and stable discharge was obtained with the average plasma density (5–10) × 1019 m−3. Despite the increase in the magnetic field, the neutral beam injection (NBI) led to clear and reproducible transition to the H-mode accompanied by a decrease in the turbulence level at the plasma edge. NBI allowed effectively heat the plasma: electron and ion temperatures in the plasma core exceeded 1 keV. Compared to the previous experiments carried out with a toroidal magnetic field as high as 0.4 T plasma total stored energy was increased by a factor of 4. The main reason or this phenomenon is a strong dependence of the energy confinement time on the toroidal magnetic field in the spherical tokamak. It was experimentally confirmed that such kind of dependence is valid for ST with magnetic field up to 0.8 T. It has also been shown that the enhancement of the energy confinement in Globus-M2 with collisionality decrease is associated with an improvement of both electron and ion thermal insulation.

Active NPA measurements of the fast ion distribution using the neutral beam as an additional charge exchange target are discussed. Expressions for the calculation of the NPA signal based on the fast ion distribution and for the reconstruction of the fast ion distribution from the NPA signal are provided. Demonstration of the described approach is carried out on the Globus-M2 spherical tokamak, where a scanning system for the NPAs was recently installed. Main features of the active NPA application on Globus-M2 are considered. The energy and spatial distributions of fast deuterium ions at dedicated pitch angles are obtained and compared with the calculated ones. Key traits of the obtained distributions are considered and explained.

The application of the laser-aided diagnostic using the nanosecond laser for direct measurement of hydrogen concentration on the walls of the Globus-M2 tokamak is under discussion. The D release after the laser irradiation with the fluence in the range of 0.1 - 4 J/cm2 was measured in laboratory experiments at the Large MEPhI mass-monochromator facility for W-D, Ti-D films, and for the W tile exposed in the Globus-M tokamak. The desorption flux was high enough to be detected during similar measurements inside the Globus-M2 tokamak. TMAP 7 modeling of D release from W-D films was done for the relatively low laser fluence (

Experimental study of thermal energy confinement in magnetic confinement devices is one of the fundamental problems in plasma physics. The data processing technique covering kinetic and magnetic measurements performed for the Globus-M tokamak is described. A zero-dimensional code has been developed on the basis of this approach making it possible to calculate important discharge parameters during the experiment (between discharges): the electron and ion stored thermal energy content, plasma effective charge, and confinement time. Good agreement of the zero-dimensional calculations and ASTRA modeling indicates that this approach can be applied for routine data processing in Globus-M in view of the specifics of the device.

A high-energy counter-NBI has been applied for the first time on the Globus-M spherical tokamak. An ELM-free H-mode has been obtained. However, no significant increase in the ion temperature and plasma energy content compared to ELMy H-mode has been observed. This is due to a high level of the fastion losses. Neither increase in the plasma current nor an increase in plasma-wall distance resulted in an increase in NB heating efficiency as it occurred during the co-NBI experiments.

Data on the dynamics of the plasma current quench in the Globus-M tokamak are presented. The main current quench characteristics at different toroidal magnetic fields are compared. The distribution of the toroidal current induced in the vessel wall is determined from magnetic measurements, and the electromagnetic loads acting on the vessel wall during the current quench are calculated. By extrapolating the experimental data, the additional pressure on the vessel wall during the current quench in the upgraded Globus-M2 tokamak is estimated. It is shown that the current quench results in the appearance of bending stresses in the vessel domes. Using numerical simulations, it is shown that the best agreement between the measured and calculated plasma current dynamics during the current quench corresponds to the linear (in time) influx of the carbon impurity.

The mechanisms for the sintering of ultrafine-grained 95%W–3.5%Ni–1.5%Fe heavy tungsten alloy powders have been investigated. It has been established that a decrease in the activation energy of grain boundary diffusion and the formation of a nonequilibrium solid solution of nickel and iron in the surface layer of tungsten particles upon high-energy ball milling are responsible for the decrease in optimal sintering temperature.