The paper investigates the trapping and desorption of hydrogen isotopes under irradiation of zirconium alloy E110 with ions of deuterium plasma. It is established that, under the irradiation, ...hydrogen exchange between the alloy and the gaseous ambient occurs: part of deuterium from the irradiation flux is trapped by the alloy, and at the same time, hydrogen initially contained in the alloy is partially desorbed. In general, hydrogen exchange results in an increase in the content of hydrogen isotopes in the sample. Addition of 30 at % oxygen to the plasma-forming gas, as well as increasing the sample temperature from
T
= 450 K to
T
= 600 K, slows down deuterium trapping and accelerates hydrogen desorption, leading to a decrease in the content of hydrogen isotopes in the sample. Increasing the dose of irradiation of E110 alloy with deuterium plasma ions intensifies both deuterium trapping and hydrogen desorption. On the basis of the experimental results, the mechanism of hydrogen exchange between zirconium alloy and gaseous ambient under the ion irradiation is proposed. The process includes three stages: reactions on the oxidized surface of zirconium alloy (hydroxylation of surface oxide and formation of water molecules); reactions on the metal–oxide boundary; and transport of hydrogen isotopes through the surface oxide layer in both directions. Surface reactions initiated by irradiation trigger the hydrogen exchange process.
The diagnostic methods and devices used to study the interaction of plasma with materials in modern fusion facilities are considered. Based on the analysis of methods and devices, it is concluded ...that the measurements performed by them, separated in space and time, do not provide a sufficiently complete amount of information necessary to identify the mechanisms, regularities, and parameters of the development of processes on the surface of the first wall under plasma exposure. A multifunctional diagnostic probe is proposed, which includes materials science and spectrometric parts, as well as single and double Langmuir and Mach probes. The multifunctional probe is designed to carry out a set of mass spectrometric and materials science measurements necessary to identify the mechanisms and regularities of phenomena on the surface of the first wall of a thermonuclear facility under intense plasma irradiation, as well as to measure the parameters of impurity flows into the plasma.
Formation of dust particles and clusters is observed in almost all modern fusion devices. Accumulation of dust in next-generation thermonuclear installations can significantly affect plasma ...parameters and lead to accumulation of unacceptably large amounts of tritium. The use of a specially developed electrostatic probe is planned in the international thermonuclear experimental reactor ITER to collect dust for further analysis. The article describes a numerical model of movement of dust particles in an electrostatic probe. Dust particle trajectories inside the probe are analyzed. Several electrostatic probe design modifications are proposed on the basis of the analysis in order to increase the efficiency of dust collection.
In this work, the results of the irradiation of untreated, preliminarily Ar+-bombarded and Cr-coated samples of zirconium alloy E110 (Zr-1%Nb) with deuterium atoms and ions of deuterium plasma were ...compared with the results of their exposure to superheated water steam (673 K, 11 MPa; 673 K, 0.1 MPa; 633 K, 0.1 MPa). It was concluded that, despite of the difference in the rates of the oxide layer formation, the features of hydrogenation are similar under the two kinds of impact. However, the hydrogen uptake under irradiation occurs hundreds of times faster than during the steam test. The most effective hydrogenation was achieved under irradiation of the E110 sample with 300–500 eV/at ions of deuterium plasma without oxygen. These circumstances allow suggesting the irradiation with ions of hydrogen plasma as an accelerated hydrogenation test of zirconium alloys and protective coatings under conditions simulating the environment of light-water reactor's core. The proposed method could be realized using a simple plasma device and it does not require high power consumption or special qualification of staff.
•Features of zirconium hydrogenation in steam and in hydrogen plasma are similar.•Zirconium hydrogenation in plasma occurs hundreds of times faster than in steam.•Plasma irradiation can be used as accelerated out-of-core test of zirconium alloys.•Accelerated and steam tests of protective layers on zirconium give the same results.
The choice of plasma contact materials and configurations for power fusion reactors is still not obvious. The tokamak with reactor technologies (TRT) under construction should help resolve this ...issue. Therefore, the most complete study of the effect of plasma on the tokamak divertor for various types of discharges and an analysis of their consequences are of great importance. Divertor probes are devices that measure thermal and corpuscular flows toward the surface of a divertor and/or record the results of their impact on the divertor. They have found wide application in fusion facilities. The features, advantages, and disadvantages of the divertor probes presented in literature, as well as cases of using samples of materials or devices to solve individual problems to which divertor probes are applicable are discussed in this work. A preliminary design and thermal calculations of the divertor probe for the TRT tokamak are presented, which, according to the authors, is capable of performing a set of measurements that make it possible to draw a conclusion about the mechanisms and regularities of processes on the divertor surface depending on the parameters and conditions of plasma irradiation, as well as to speed up the determination of optimal materials and modes of plasma irradiation of divertor tiles.
In this paper, features of the modification of near-surface layer of R6510P100D01 grade graphite under irradiation by deuterium and helium ions at a temperature of 2050 °C is investigated. It is ...shown that irradiation by such ions at a flux density of 1,4×1018 ion/cm2s initiates vacancy transport from the irradiated surface to the bulk of the sample, leading to the formation of a porous layer inside the sample with a thickness of over 2 mm. High sputtering yields, exceeding those for irradiation by the same ions at room temperature with a moderate intensity ion fluxes, lead to the conclusion that in these conditions, sublimation is the main mechanism of the removal of carbon atoms from the surface of graphite.
The features of hydrogen trapping under the irradiation of zirconium alloys E110 and E635 with an electron beam (400 eV, 0.8 mA/cm
2
) in various gaseous ambient containing oxygen and hydrogen (Ar + ...O
2
+ H
2
; Ar + H
2
O) are studied. The effect of surface temperature on the hydrogenation of zirconium alloys under electron irradiation is studied. It is shown that neither exposure nor electron irradiation in a gaseous ambient containing a mixture of H
2
and O
2
at 700 K for 20 h leads to a change in the hydrogen level in the E110 alloy, while hydrogen partially escapes from the E635 alloy during the experiment. The amount of hydrogen in zirconium alloys after exposure in a gaseous ambient containing H
2
O in a similar temperature–time regime also changes insignificantly; however, if the alloys are irradiated with electrons under these conditions, then they contain 1.5–2 times more hydrogen. When temperature of the samples is raised to 900 K, electron irradiation in the presence of water vapor, on the contrary, reduces the trapping of hydrogen in the E110 and E635 alloys, compared with exposure in the same gaseous ambient without irradiation. It is concluded that electron irradiation affects the balance of surface reactions of formation of hydroxyl groups from adsorbed water molecules and reverse reactions of formation of water molecules from surface hydroxyls. The direction of shifting the balance of these reactions depends on the surface temperature.
It was shown (Buzhinsky, 2003) that in situ renewable coating of boron carbide can protect the tiles of the divertors of thermonuclear facilities from destruction and also to prevent accumulation of ...remarkable amounts of tritium in the plasma facing materials. In the paper presented a plasma method for deposition of boron carbide coating with a high adhesion to tungsten was developed. In the laboratory installation boron carbide coating on tungsten was subjected to cycling irradiation by the deuterium ion flux with power density up to 5.0 MW/m2 in the temperature range up to 1500 K. The results of the tests showed that the composition, integrity and adhesion of the coating were not violated in the laboratory tests. In the T-10 tokamak the behavior of the coating was investigated in the temperature range up to 3600 K when irradiated with plasma power in the range of 20-100 MW/m2 during plasma disruption. Being irradiated in T-10 tokamak, the coating retained its continuity, adhesion and protected tungsten from the effect of the even at temperatures of 2500-3600 K, when the coating melted under irradiation and its composition changed to B:C ≈ 1:1.
During the DITS (Deuterium Inventory in Tore Supra) project, inner vessel walls of Tore Supra tokamak have been loaded with deuterium during a specific plasma experiment based on long pulse ...operation. Then, and in order to determine where the deuterium used as a plasma fuel was lost in the plasma facing components, the Tore Supra limiter had been dismounted and post mortem analysis had been performed on samples coming from different places corresponding to erosion or deposited area. In this the thermo-desorption spectrometry (TDS) studies are presented. All the TDS spectra present independently to their origin the same behaviour e.g. 5 desorption bands at 560 K, 820 K, 1050 K, 1238 K and 1375 K. These bands correspond to different trapping processes in carbon material which are identified with the help of laboratories experiments. Finally, the spectra are fitted by a rate equation model in which one of the main parameter which is the exponential pre-factor is experimentally evaluated (2.7.10 super(15) s super(-1)). This gives the possibility to unambiguously determine the trapping energies for the 5 trapping processes: 1.8 eV, 2.8 eV 3.6 eV, 4.2 eV and 4.7 eV. The model uses a dispersion in energy around these values due to the complex structure of Carbon Fibre Composite.
In this work, thermal-desorption spectrometry is used to study Be–W and Al–W intermetallic compounds formed on the surface of tungsten during the deposition of Be and Al atoms evaporated in the ...temperature range of 400–500 K, as well as Al atoms sputtered in argon plasma. Due to safety limitations imposed on work with beryllium in the university laboratory, most of the experiments are carried out with aluminum which is one of the proxy materials to beryllium. Regularities for the formation of intermetallics in the surface layer of tungsten during the deposition of Al and Be atoms, and in the layer formed during the joint deposition of Al and W atoms on tungsten are described. The features of the trapping of argon and hydrogen into the intermetallics are analyzed for different fluences of Al atoms deposited in plasma on the surface of tungsten, as well as for different concentrations of components in the deposition flux during the simultaneous deposition of Al and W atoms on tungsten. The features of the Al–W intermetallic formation and the nature of the retention and desorption of gases during the deposition of evaporated and plasma-sputtered aluminum atoms on tungsten are revealed. The release of a significant part of hydrogen from the Al–W intermetallic under irradiation with 50 eV ions of deuterium plasma at a temperature of 500 K is found. Most of the gases trapped by Be–W and Al–W intermetallics is desorbed in the interval of 1200–1600 K during intermetallics decomposition.
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