The created plasma device PLM-M is used to test the heat-shielding lining of the in-vessel components of a thermonuclear reactor with steady-state plasma having parameters similar to the near-wall and divertor plasma of a tokamak. The PLM-M is a linear magnetic trap with a multi-cusp magnetic field. A special feature of the device is the many hours of steady-state operation with magnetized plasma of high parameters. Tungsten modules manufactured using ITER divertor technology have been tested with high-heat loads from 1 to 5 MW/m2. There were no significant macroscopic surface changes, large-scale cracks or splits on the surface, or significant erosion of the tungsten layout during plasma tests. For additional load on the tungsten during plasma tests, a laser with a power simulating the level of ELMs was used. Traces of arcs were detected on the plasma-facing tungsten surface of the model during plasma tests. Additional tests of cooled tungsten modules of in-vessel components are planned in order to estimate their erosion in the ITER and develop recommendations for in-vessel component design for the FNS.

One of the main objectives of the materials science studies on the T-15MD tokamak is to insert samples, including large-scale ones, both for their long-term life cycle tests in the Scrape-Off Layer (SOL) plasma areas and for studying the effect of pulse loads in the divertor section. A conceptual design of a complex for materials science tests on the T-15MD tokamak has been developed at the Department of General Physics and Nuclear Fusion of the National Research University Moscow Power Engineering Institute. The complex will enable unique experiments to be conducted for investigating the state and composition of the divertor and first wall surfaces without the need to disturb the tokamak vessel vacuum or dismantle the components. It will be possible to perform such tests in the time intervals between tokamak pulses, which will reveal changes on the divertor surface after each pulse and allow to estimate correlations between the plasma parameters and changes on the first wall surface. Means are provided in the attachment assembly for cooling mockups with both water flow and dispersed water-air flow. In addition, various dignostics for monitoring the first wall and divertor surfaces can be installed on the attachment assembly.

Tungsten and stainless steel samples were irradiated with stationary helium plasma in the plasma linear multicusp plasma device. The surface of the material is modified under the influence of helium plasma with the formation of nanostructures and microstructures on the surface. The fluence of helium ions equal to 8 x 1027 ions/m2 was achieved on the tungsten sample. Depending on the helium ion fluence, fuzzlike layers, loops, and bubbles of 20- to 500-nm scale were formed on the tungsten surface. The fuzz layer thickness depends on the duration of plasma irradiation in a wide range of fluence. Saturation of the growth of the thickness of the tungsten fuzz layer was observed at a fluence of more than 8 x 1026 ions/m2. The growth of microstructures and nanostructures on the surface of stainless steel irradiated with helium plasma was observed. The growth of nanostructured layers is explained by a theoretical model considering the dynamics of adatoms under the influence of plasma.

This article describes the study of low pressure helium plasma with magnetic confinement at the experimental test setup at the Moscow Power Engineering Institute: plasma linear multicusp (PLM). This facility is intended for testing refractory materials and prototypes of elements of the first wall within the framework of development of the national fusion reactor (DEMO–FNS) and the International Thermonuclear Experimental Reactor (ITER). The facility provides the conditions of plasma impact on the surface of tested sample close to the parameters and regime of operation of tokamak divertor plates. The facility is a magnetic trap with minimum magnetic field on the axis, where the plasma is created by the flow of electrons moving from the directly heated tantalum cathode toward the anode. It is possible to create stationary helium plasma in the facility and to maintain it for several hours under constant discharge parameters: helium pressure in the chamber of 10–3–10–1 Torr, discharge current of 4–30 A, plasma column diameter of 35–40 mm, voltage drop across the discharge gap of 100–200 V. The thermal load on the surface of target introduced into the axial region of plasma column has reached 5 MW/m2. Optical emission spectroscopy is the main diagnostic tool in this work. The procedure for determining atomic concentrations from the data on the relative intensities of atomic spectral lines of metallic impurities is proposed in this work.

A new method of X-ray photoelectron spectra processing based on a target model with a stochastic surface layer is proposed. On the basis of this model, X-ray photoelectron spectra of multilayer multicomponent metallic targets with an inhomogeneous surface layer are obtained for various probing angles considering surface shading effects. A layer-by-layer phase profile of metallic samples is obtained using the advanced method of surface analysis based on angle-resolved X-ray photoelectron spectroscopy. The results are validated by atomic force microscopy.

The erosion of nanostructured tungsten and titanium by high-heat plasma flux, laser, and arcing is investigated. To fabricate nanostructural fuzz layers and hierarchical granularity on the surfaces, samples were exposed to helium plasma in the steady-state plasma device PLM-M, which is a linear plasma trap of an eight-pole multicusp magnetic field with parameters similar to the scrape-off layer and divertor plasma in a tokamak. Arcing ignited with a Nd:YAG laser pulse on the target fuzzy surface in the helium plasma resulted in the melting of fibers and the creation of craters of several microns in depth and several tens of microns in diameter.

The modern challenges of nuclear energy are the replenishment of dwindling reserves of nuclear fuel and the development of a closed nuclear fuel cycle while complying with strict radiation safety requirements. A fusion neutron source has unique capabilities to solve these problems. The preliminary results of a neutronic analysis of the FNS-C fusion-fission hybrid neutron source with a thorium-uranium aqueous blanket by the Monte Carlo method computer simulation, using the MCNP-4 code with the ENDF/B-VII cross-section library, gives satisfactory results for the study of the possibility of creating a compact source of fusion neutrons based on a small spherical tokamak for commercial use. The obtained results show that the FNS-C hybrid blanket generates enough tritium to fully ensure the uninterrupted operation of the FNS-C throughout the year. The reproduction coefficient of U-233 is 1.027 at a consumption of 1304 kg/year of the fissile material in the aqueous blanket containing Th-232 enriched to 1.47% U-233. The FNS-C is operated with an effective neutron multiplication factor k(eff) similar to 0.99 with reactivity rho = -0.006249 in the presence of delayed neutrons, which corresponds to the safest state of the core of thermal neutron fission reactors. The thermal power of the FNS-C at k(eff) similar to 0.99 is similar to 3 GW, which is comparable to the thermal power of fission reactors. This indicates the potential possibility of creating a safe thorium-uranium breeder power reactor based on a fusion neutron source. The results of the study were obtained for the simplified approximate geometrical FNS-C model. To confirm the preliminary results, it is necessary to develop a more accurate calculation model of the FNS-C machine.

Methods for processing optical emission spectroscopy data in the study of the region of interaction between helium plasma with a density of the main gas [He] ≈ 10 12 –10 14 cm –3 and electrons n e ≈ 10 11 –10 13 cm –3 and a tungsten sample in a PLM facility designed for testing materials with a plasma load are presented. A method for measuring the electron temperature using the coronal approximation is proposed. For the calculation, it is necessary to choose the ratio of the intensities of spectral lines that is most sensitive to the electron temperature; in this case, this is the ratio of the intensity of ionic lines to atomic lines. Comparison of the ratio of the experimental intensities of the He II 468.5 nm ion line and a number of He I atomic lines with well-known electron excitation constants with the calculated dependence of this ratio on the mean electron energy is a reliable method for the spectral determination of the electron temperature of a magnetized rarefied helium plasma. In experiment, the concentration of atomic helium is [He] ≈ 10 14 cm –3 ; the discharge current is 2–10 A; the voltage drop is 160–180 V; the radius and length of the discharge are 16 and 370 mm, respectively. The electron temperature measured using two singlet and two triplet lines of He I is T e = 2.4 ± 0.2 eV. With consideration of the nonlocality of the electron energy distribution function (EEDF), the complex nature of the drift and diffusion of charges in crossed and inhomogeneous electric and magnetic fields, etc., the mean electron energy of ε^_ = (3/2) kT e ≈ 3.6 eV corresponding to this temperature can be considered a lower estimate for the energy of the Maxwellian section of the EEDF of the plasma.

The review summarizes recent experimental results of studying heat transfer on rough surfaces synthesized by plasma. The plasma-surface interaction leads to the stochastic clustering of the surface roughness with a high specific area breaking the symmetry of the virgin surface of the initial crystalline materials. Such a surface is qualitatively different from the ordinary Brownian surface. The micro- and nanostructured surface consist of pores, craters, and nanofibers of size from tens of nanometers to tens of microns, which can provide new heat transfer properties related to a violation of the symmetry of the initial materials. In recent years, new results have been obtained in the study of heat transfer during phase change on plasma-modified surfaces in relation to energy, chemical, and cryogenic technologies. The objective of the review is to describe the specific structure of refractory metals after high-temperature plasma irradiation and the potential application of plasma processing of materials in order to create heat exchange surfaces that provide a significant intensification of two-phase heat transfer. Refractory metals with such a highly porous rough surface can be used as plasma-facing components for operation under extreme heat and plasma loads in thermonuclear and nuclear reactors, as catalysts for hydrogen production, as well as in biotechnology and biomedical applications.

The design of the demonstration fusion neutron source (DEMO-FNS) demonstration fusion–fission hybrid facility is carried out at the National Research Center ‘Kurchatov Institute’ in Russia. For the implementation of the DEMO-FNS project, it is important to assess the effect of the fast neutron spectrum on radiation-induced damage to the device materials, primarily the materials of the first wall, which is the most problematic unit of the device. Due to the lack of real hybrid fusion devices, the study can only be carried out using computer simulations of the experiment. A computer simulation using the Monte Carlo method was carried out to calculate the developed three-dimensional full-scale model of the DEMO-FNS reactor with a blanket for the transmutation of minor actinides. The MCNP-4 code was used with cross-sections from the FENDL-2.1 and ENDF/B-6 files, as well as with cross sections for calculating radiation displacements. The neutron spectrum in the first wall of DEMO-FNS was determined at the power of a volumetric deuterium–tritium neutron of 1.42 × 1019 n s−1. It was found that beryllium as a plasma-facing material has too short lifetime under the neutron load on the first wall and divertor plates of DEMO-FNS. The replacement beryllium to tungsten is problematic and requires special study. Copper alloys have sufficient resistance to the effects of neutron radiation of DEMO-FNS for one full power year, but will require several replacements when operating the device for more than 10 years. The steels used in fast reactors can meet the operational requirements of the first wall of DEMO-FNS. To solve the problem of choosing materials for the first wall of DEMO-FNS, new experimental researches on changes in the physical properties of these materials in the fast neutron spectrum are needed.

Titanium, tungsten, carbon, lithium, and beryllium surface structure were analyzed after plasma irradiation in fusion devices. Exceptional extreme high-temperature plasma load in fusion devices leads to specific surface clustering. It is strictly different from any other conditions of material’s clustering. The hierarchical granularity with cauliflower-like shape and surface self-similarity have been observed. Height’s distribution is deviated from the Gaussian function. The relief roughness differs qualitatively from the ordinary Brownian surface and from clustering under other conditions. In fusion devices, the specific conditions regulate material surface clustering faced to plasma. Ions and clusters melt on the surface and move under the effect of stochastic electromagnetic field driven by the near-wall turbulent plasma. In such a process, long-term correlations lead to the growth of surface with a self-similar structure. The multiscale synergistic effects influence the self-similarity–fractal growth from nanometers to millimeters. Experimental results illustrate universality of stochastic clustering of materials irradiated with plasma in fusion devices.

Combined tests of tungsten mock-ups with thermocyclic test in the electron beam facility with the load up to 50 MW/m² and subsequent irradiation with steady-state plasma load up to 1 MW/m² in PLM device have been carried out to simulate a material degradation under loads expected in a fusion reactor. Cracks of 1–5 microns and more have been formed on the surface of the tungsten during e-beam test. Melted layer observed in the area of e-beam hot spot load. Plasma load led to a formation of nanostructured layers on the surface.

The results from experimental investigations of chamber internal parts and plasma-facing materials proposed for use in a thermonuclear reactor are reviewed. The thermonuclear reactor internals will experience various heat loads connected with temperature gradients and local exposure dose with the nuclear reaction neutron energy spectrum. The lifetime of the systems will depend on the resistance of materials to neutron and heat loads. Assurance of heat removal is one of serious problems to be solved in implementing a thermonuclear power plant. The components can be cooled either by gas or liquid, including salt solutions and liquid metals. The parameters of coolants, heat-transfer systems, and cooling systems will take values that are still not attainable as of yet. The variety of available design elaborations suggested in the Russian and foreign projects must be substantiated in terms of heat transfer. The parameters of heat and neutron loads will govern the choice of materials for the thermonuclear reactor systems. The international thermonuclear experimental reactor (ITER), which is under construction, will be built using structures, materials, and technologies that have passed the main tests. The ITER cooling systems will operate with forced single- phase convection of turbulent water flow; the heat transfer will be intensified by using inner finning and flow swirling. The thermal protection lining of the plasma-facing chamber's internal parts in the zones of the highest plasma and heat load will be made of tungsten. In elaborating the design of the next-generation demonstration reactor (DEMO), it will be necessary to additionally develop the blanket construction technologies and solve the problem of converting heat into electricity. The materials for the DEMO reactor must be selected with due regard to the high dose of their irradiation by neutrons with the thermonuclear reaction energy spectrum and critically high heat loads experienced by the plasmafacing chamber's internals. It will be necessary to develop and test new materials for constructing the DEMO thermonuclear reactor and solve matters concerned with their commercial-scale manufacture.