There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

/pdf/plasma-material-interactions-in-current-tokamaks-and-their-1a6iwv89x6.pdf

Plasma{material interactions in current tokamaks and their implications for next step fusion reactors

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

http://liu.diva-portal.org/smash/get/diva2:303552/FULLTEXT01

The Mn+1AXn phases: Materials science and thin-film processing

The MAX phases are a group of layered ternary compounds with the general formula Mn+1AXn (M: early transition metal; A: group A element; X: C and/or N; n = 1–3), which combine some properties of metals, such as good electrical and thermal conductivity, machinability, low hardness, thermal shock resistance and damage tolerance, with those of ceramics, such as high elastic moduli, high temperature strength, and oxidation and corrosion resistance. The publication of papers on the MAX phases has shown an almost exponential increase in the past decade. The existence of further MAX phases has been reported or proposed. In addition to surveying this activity, the synthesis of MAX phases in the forms of bulk, films and powders is reviewed, together with their physical, mechanical and corrosion/oxidation properties. Recent research and development has revealed potential for the practical application of the MAX phases (particularly using the pressureless sintering and physical vapour deposition coating rout...

Progress in research and development on MAX phases: a family of layered ternary compounds

Material Characterization of Cast Iron by Eddy Current Testing

Investigation of the role of a nonmagnetic spacer in local wall thinning inspection

This paper describes a newly developed arrayed multi-coil probe for the testing of steam generator tubes by eddy current testing. Owing to the multi-coil arrangement, it is possible to detect cracks in the whole round of the tube without rotation. Geometry of the probe was decided with the help of numerical simulation, which leads to high detectability of the probe. The signals of this probe were predicted by the edge based finite element method, and comparison between experimental and numerical results showed good agreement. Furthermore, this probe is expected to be convenient to reconstruct the crack shape from its C-scan image.

Development of an arrayed multi-coil eddy current testing probe with the help of numerical simulation

In this study an approach is proposed to probabilistically evaluate wall thickness and the probability of pipe failure when subjected to wall thinning based on the results of periodic non-destructive evaluations. Electromagnetic acoustic resonance (EMAR) has been adopted as a specific non-destructive method to evaluate pipe wall thickness. A probabilistic model correlating the true and evaluated thicknesses was proposed on the basis of the results of laboratory experiments to measure 38 artificially corroded carbon steel plates. A Bayesian approach was proposed to estimate the probability of true thickness and the probability of failure from results of multiple non-destructive evaluations at certain time intervals. The approach was applied to the analyses of several virtual periodic EMAR evaluations of pipe wall thickness that gradually became thinner, whose results demonstrate that the proposed approach is effective regardless of the variability of corrosion rates.

Probabilistic evaluation of EMAR signals to evaluate pipe wall thickness and its application to pipe wall thinning management

A recently developed nondestructive method, called Magnetic Adaptive Testing, which is based on systematic
measurement and evaluation of minor magnetic hysteresis loops was applied for detection of local material
thinning in a thick, L-shaped ferromagnetic carbon steel, which simulates T-tubes with reinforcing plates.
Artificially made slots were reliably detected with a good signal/noise ratio from the other side of the specimen,
even through a covering ferromagnetic plate.

Tetsuya Uchimoto

Papers

Material Characterization of Cast Iron by Eddy Current Testing

Investigation of the role of a nonmagnetic spacer in local wall thinning inspection

Development of an arrayed multi-coil eddy current testing probe with the help of numerical simulation

Probabilistic evaluation of EMAR signals to evaluate pipe wall thickness and its application to pipe wall thinning management

Nondestructive detection of local material thinning in ferromagnetic materials by Magnetic Adaptive Testing