Heat loads on the tungsten divertor targets in the ITER and the tokamak power reactors reach ~10MW m
−2
in the steady state of DT discharges, increasing to ~0.6–3.5 GW m
−2
under disruptions and ...ELMs. The results of high heat flux tests (HHFTs) of tungsten under such transient plasma heat loads are reviewed in the paper. The main attention is paid to description of the surface microstructure, recrystallization, and the morphology of the cracks on the target. Effects of melting, cracking of tungsten, drop erosion of the surface, and formation of corrugated and porous layers are observed. Production of submicron-sized tungsten dust and the effects of the inhomogeneous surface of tungsten on the plasma–wall interaction are discussed. In conclusion, the necessity of further HHFTs and investigations of the durability of tungsten under high pulsed plasma loads on the ITER divertor plates, including disruptions and ELMs, is stressed.
The inhomogeneous stochastic clustering of the surface with the self-similarity of the granularity structure from nano- to macroscales is observed in various materials after the action of intense ...high-temperature plasma flows in nuclear fusion facilities. The spectral and statistical characteristics of hierarchical granularity and scale invariance are estimated. They qualitatively differ from the properties of the simplest Brownian surface roughness and clustering under other conditions possibly because of universal mechanisms of the formation of stochastic clustering of materials under the action of a high-temperature plasma.
Experimental data on the novel materials generated in fusion devices under conditions of high-temperature plasma loads is reviewed. In fusion devices, due to the interaction of turbulent plasma with ...the surface, the stochastic clustering occurs and the fractal structure forms on the plasma-facing surfaces. Such surfaces are characterized by an extremely high specific area and statistical self-similarity of the surface roughness. The generated fractal structures are nano-sized and the surface consists from pores and craters ranging in size from tens of nanometers to tens of micrometers. The occurrence of such structures can result in the appearance of additional properties of such a multiscale surface, in particular, the specific catalytic properties. Statistical characteristics of such material surface characterized by the hierarchical granularity and scale invariance qualitatively differ from those of the ordinary rough Brownian surface. This gives basis for development of innovative plasma technologies for the synthesis of new nanostructured materials with the required roughness and porosity for nuclear, chemical, hypersonic technologies, as well for biotechnologies and biomedical applications.
It is proposed to control plasma turbulence near the LCMS of a tokamak with a system of electrodes made from porous tungsten. We propose to apply the RF modulation at the ion-cyclotron resonance ...frequency for driving of fluctuations near the LCMS. Porous tungsten plates used as biasing electrodes are the advantage to increase the emissivity of the porous surface and to reduce a surface erosion. To reduce the drag and thermal load on streamlined surfaces at supersonic and hypersonic speeds, it is proposed to cover the aircraft with materials of high porosity. The first experiments were carried by using model with fractal surfaces having non-Gaussian height statistics from ∼ 500 nanometers to ∼ 200 micrometers obtained by plasma treatment. The advantage of such a surface is the coincidence of the spectral and statistical characteristics of the stochastic topography of the surface with the turbulence characteristics of the flow.
The results of a study of a surface formed by high-temperature plasma loads on refractory metals such as tungsten and stainless steel are presented. There is an inhomogeneous stochastic clustering of ...the surface with self-similarity properties of the granularity structure from nanoscale to macro scale, similar to the previously described fractal structure of carbon materials from fusion device. The statistical characteristics of hierarchical granularity and scale invariance are estimated that qualitatively differ from the properties of the roughness of the Brownian surface, which is possibly due to the universal mechanisms of stochastic clustering of materials under the influence of high-temperature plasma.
Principal component (PCA) and factor analysis (FA) are widely used in animal behaviour research. However, many authors automatically follow questionable practices implemented by default in ...general-purpose statistical software. Worse still, the results of such analyses in research reports typically omit many crucial details which may hamper their evaluation. This article provides simple non-technical guidelines for PCA and FA. A standard for reporting the results of these analyses is suggested. Studies using PCA and FA must report: (1) whether the correlation or covariance matrix was used; (2) sample size, preferably as a footnote to the table of factor loadings; (3) indices of sampling adequacy; (4) how the number of factors was assessed; (5) communalities when sample size is small; (6) details of factor rotation; (7) if factor scores are computed, present determinacy indices; (8) preferably they should publish the original correlation matrix.
We develop a theory of thermal transport in nanoscale-layered structures based on wave processes. The theory incorporates two fundamental principles, first, that the spectra of thermally excited ...waves are determined by the temperature differential and the heat flux, and second, that the wave fields in the heat exchanging domains are coupled. The developed method includes classical theories as special cases that are valid in larger scales, and it naturally explains such phenomena as interface thermal resistance (Kapitsa resistance) and thermal rectification (asymmetry of thermal transport). Numerical examples demonstrate the feasibility of the approach, and they show good agreement with measurements of Kapitsa resistance reported in the literature.
The review summarizes recent experimental observations of materials exposed to extreme hot plasma loads in fusion devices and plasma facilities with high-temperature plasma. Plasma load on the ...material in such devices lead to the stochastic clustering and fractal growth of the surface on scales from tens of nanometers to hundreds of micrometers forming statistical self-similarity of the surface roughness with extremely high specific area. Statistical characteristics of hierarchical granularity and scale invariance of such materials surface qualitatively differ from the properties of the roughness of the ordinary Brownian surface which provides a potential of innovative plasma technologies for synthesis of new nanostructured materials with programmed roughness properties, for hypersonic technologies, for biotechnology and biomedical applications.
For pacemaker electrodes, the surface structure elements should be nanometer-sized in order to reduce the capacitive electrical resistance coupling of the electrode with the myocardium tissue. It is ...proposed to test several approaches. One of them is the creation of the "fuzz" nanostructure on the titanium surface accompanied by the subsequent ruthenium deposition onto this structure. Another one is the formation of the "fuzz" nanostructure on the layer of pre-deposited ruthenium. Such approaches contribute to developing new technology for manufacturing the electric cardiac pacemakers with improved characteristics.
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