Titanium activation foils for neutron studies were exposed inside the JET tokamak vessel during the entire 15 months long experimental campaign with deuterium fuelling. Afterwards, it was found that the structure of some foils was only slightly affected, while others were totally or partly disintegrated into dust: flakes and powder. The analyses indicated that defects produced in materials by cutting during the sample preparation eventually lead to the degradation of the titanium crystal structure upon the exposure in JET to neutral particles including hydrogen. In some cases, a passive oxide layer on the foil surface effectively prevented the access of hydrogen, and by this protected the metal against partial or complete transformation into the titanium hydride powder.

The morphological and structural changes of dual-phase tungsten specimens with high entropy alloy (HEA) as a second phase (95% W, 5% of FeNiCuCrMn) are investigated after deuterium plasma irradiation. The heat flux factor of deuterium plasma pulses is comparable to transient events (ELM-s and VDE-s) in ITER. The study shows that the use of HEA as a second phase reduces significantly the extent of crack generation in comparison with pure tungsten, and even with a dual-phase alloy of W and FeNi as a second phase. The hardness of W-HEA depends on the manufacturing method (spark plasma sintering, or pressure-less sintering) and is comparable with spark plasma sintered pure tungsten. The layer with decreased hardness is present after irradiation and has a thickness of about 50-80 mu m which is less than in the case of pure tungsten.

The morphological and structural changes of two different dual-phase tungsten alloy (either 3% or 5% of an added mixture of Fe and Ni) are investigated after deuterium plasma irradiation. Heat flux factor of deuterium plasma pulses is comparable to transient events in ITER. This study compares the changes in tungsten alloy materials between two different regimes with a different number of plasma pulses. Fe and Ni as a binder play an essential role in absorbing plasma shocks to decrease the morphological and structural changes. These results are compared to changes of pure single and double forged tungsten irradiated in similar conditions.

The changes of the structure and properties of a dual phase tungsten (W) alloy (with either 3 % or 5 % of an added mixture of Fe and Ni) are investigated after irradiation with powerful deuterium plasma pulses. The interplay of very powerful plasma pulses, comparable with the off-normal events of ITER or plasma pulses with heat flux factor values comparable with ELMs, is studied. We show that the size of characteristic damage that develops on the irradiated surface follows the size of the tungsten grains. The Fe and Ni alloy plays the role of shock absorber between the grains of the material, and disables the development of cracks both on the surface and within the bulk. The results are discussed and compared to previous results obtained for pure double and single forged W.

Experiments on the plasma focus device PF-12 have been carried out to investigate changes in the structure of the surface and bulk of tungsten and tungsten doped with 1% lanthanum oxide after repeated powerful deuterium plasma shots (8, 25 and 100). The surface morphology of the targets exposed to plasma streams is analyzed by electron and optical microscopy. Due to the plasma effect, different surface structures, such as wave-like structures, a melted layer, a mesh of microcracks, droplets, craters, crevices and holes, appear. The change of cross-section hardness after a number of shots in different materials is investigated.

A method has been developed for calculating diffusion profiles in ternary systems by using effective interdiffusion coefficients of components and Boltzmanns solution for diffusion equation with variable diffusion coefficient. Using this method the concentration profiles for several diffusion couples in the systems Fe-Co-Ni and Cu-Fe-Ni are calculated as examples and some peculiarities of these calculations are discussed, particularly, how to solve some possible difficulties, which may sometimes arise at calculation procedures. It is shown that having the data on effective interdiffusion coefficients and their concentration dependence for at least two components in a ternary diffusion couple, the concentration profiles for all three components can be calculated with good accuracy.

An analysis of diffusion paths in single-phase ternary metal systems Co-Fe-Ni and Cu-Fe-Ni on the basis of the phenomenological interdiffusion model using effective interdiffusion coefficients is presented. The peculiarities of practical application of effective interdiffusion coefficients of components for calculating diffusion paths in ternary systems are analysed. It is done on the basis of the relationship between effective interdiffusion coefficients and the diffusion paths. The results were found to be in good agreement with experimental data for the ternary systems Co-Ni-Fe and Cu-Ni-Fe. It is shown that deviation of the diffusion path from linearity in ternary single-phase diffusion couple in the system Cu-Ni-Fe mainly depends on the thermodynamic properties of the system.

Possible interrelations between diffusion paths and interdiffusion coefficients in the system Fe-Co-Ni are analyzed. It is found that the apparition of a straight line shape of diffusion paths imposes strong demands on the values of the conventional interdiffusion coefficients calculated from the experimental data. The possible consequences of this finding are discussed.

The influence of noise flatness and memory-time on the dynamics of a generalized Langevin system driven by an internal Mittag-Leffler noise and by a multiplicative trichotomous noise is studied. In the asymptotic limit at a short memory time the dynamics corresponds to a system with a pure power-law memory kernel for a viscoelastic type friction. However, at long and intermediate memory times the behaviour of the system has a qualitative difference. In particular, a critical memory time and a critical memory exponent have been found, which mark dynamical transitions in the resonant behaviour of the system. The obtained results show that the model considered is quite robust and may be of interest also in cell biology.

The paper presents experimental investigations of damages in pure tungsten and ODS (oxide dispersed strengthened) tungsten under dense plasma shots. The experiments were performed with plasma focus devices PF-12 and PF-1000 with a power flux density of 10(6) ... 10(12) W/cm(2) using deuterium. The surface morphology of the targets exposed to plasma streams is analyzed using electron and optical microscopy. Due to the plasma effect, different surface structures, such as wave-like structures, a melted layer, a mesh of microcracks, droplets, craters, crevices and holes appear. Both the original and irradiated samples were investigated by local X-ray spectroscopic analysis and by X-ray phase-shift analysis.

The paper presents experimental investigations of damages in pure tungsten and ODS (oxide dispersed strengthened) tungsten under dense plasma shots. The experiments were performed with plasma focus devices PF-12 and PF-1000 with a power flux density of 10...10 W/cm using deuterium. The surface morphology of the targets exposed to plasma streams is analyzed using electron and optical microscopy. Due to the plasma effect, different surface structures, such as wave-like structures, a melted layer, a mesh of microcracks, droplets, craters, crevices and holes appear. Both the original and irradiated samples were investigated by local X-ray spectroscopic analysis and by X-ray phase-shift analysis. PACS. 52.40.Hf

Experiments on the plasma focus devices PF12 and PF1000 have been carried out by using deuterium for investigating changes in the surface and structure of tungsten and tungsten doped with 1% lanthanum-oxide. The surfaces were analyzed and the damage factor of the irradiated samples was investigated by using electron microscopy. Also, microroughness and microhardness of the cross-sections of the specimens were investigated. As a mesh of microcracks, holes, bubbles, and a wavelike structure, due to the plasma effect, appeared on the surface, microroughness and microhardness of the surface change essentially. As tungsten is a very brittle material, the positive effect of lanthanum-oxide on the bulk and surface properties of the irradiated samples is considered.

Changes in the surface and structure of tungsten and tungsten doped with 1% lanthanum-oxide samples irradiated by powerful deuterium plasma shots are investigated. Comparative analysis of the samples microroughness, the damage factor estimated from SEM images, and the hardness of cross-sections has been carried out. It can be concluded that the doping of tungsten with 1% lanthanum-oxide may decrease the development of a mesh of microcracks on the irradiated surface. However, this doping may increase the microroughness of the sample surface.

An empirical approach to the description of diffusion paths in the ternary system Fe-Co-Ni is developed. It is shown that the experimentally determined diffusion path in this system can be described by the universal function, which contains two parameters, extracted from experimental data. The values of these parameters and their possible dependence on initial compositions of diffusion couples are discussed. Using the universal function, typical diffusion paths for the system Fe-Co-Ni have been calculated. It is shown that the calculated diffusion paths are in a qualitatively good agreement with the available experimental data.

Dependences of the parameters of interdiffusion (effective coefficients, diffusion paths, Kirkendall shift) on the variation of the initial compositions of a diffusion couple have been studied on the concrete example of the Co-Fe-Ni system. The experimental results obtained show that the diffusion paths in the three-component system depend substantially on the selection of initial conditions, even when the initial alloys of the “narrower” diffusion couple lie on the diffusion path of the “wider” pair. At the same time, when represented in reduced concentrations, the diffusion paths of all these diffusion couples practically coincide. The latter makes it possible to predict the type of diffusion paths for any diffusion couple whose initial com- position lies in the same concentration region. In one of the diffusion couples studied, the instability of the Kirkendall plane was revealed, which thus far was observed only in binary systems.

Description of diffusion paths is one of the most interesting and topical problems in experimental investigations of interdiffusion in multicomponent systems and, particularly, in ternary systems. The relationship between effective interdiffusion coefficients and diffusion paths in ternary systems has been discussed earlier but the specific influence of the mobility and thermodynamic properties of components on the characteristics of the diffusion path is still unclear. In this paper an attempt is made to clarify the separate influences of mobility and thermodynamics on the behavior of diffusion paths in ternary systems and the corresponding correlation is found. It is shown that in most cases the deviation of the diffusion path from linearity (an ideal system) is related to the deviation of the thermodynamic properties from the ideal. The results obtained are analyzed on the basis of thermodynamic data for the ternary system Cu-Fe-Ni.

The peculiarities of practical application of effective interdiffusion coefficients of components for calculating diffusion paths in ternary systems are analysed. It is shown that infinite values of the interdiffusion coefficients at zero concentration gradient’s points do not remarkably affect the accuracy of calculation in the case of a correct choice of variables. At zero-flux planes where the respective effective interdiffusion coefficient is equal to zero, no calculation problems arise, as evidently zero-flux planes can occur simultaneously only for one of the components. The results of calculation of diffusion paths for diffusion couples in the ternary systems Cu-Fe-Ni and Co-Fe-Ni using respective effective interdiffusion coefficients are presented. These results demonstrate a good accuracy of such kind of calculations even in the case of very strong deviation from linearity of the diffusion path.