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.

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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

A very fast numerical solver is developed for simulation of pulsed eddy current testing (PECT) signals caused by volumetric defects by introducing a database-type fast eddy current testing (ECT) simulation scheme for single frequency problems to the Fourier-series and interpolation-based PECT signal simulation code. First, the PECT signal simulation method based on a Fourier series scheme and an interpolation approach is briefly described. Then, a database-type fast numerical solver for single frequency ECT problems is introduced to the Fourier-series-based PECT simulation to enhance simulation efficiency. To cope with fast PECT signal simulation of 3D local wall thinning defects, a 2D shifting symmetry scheme is proposed for inspection targets of both plate and straight pipe geometries to reduce the computational burden required to establish databases of the unflawed field, which are necessary for fast ECT signal simulation. Using these strategies, a very fast numerical solver is developed for simulation of PECT signals of local wall thinning, and its validity is verified by comparing its numerical results with measured PECT signals and with those simulated using a conventional numerical code.

Development of a very fast simulator for pulsed eddy current testing signals of local wall thinning

Governing conditions of repeatable Barkhausen noise response

Macroscopic hysteresis and local Barkhausen noise techniques were used for the comprehensive magnetic investigation of structural low-carbon steel subjected to uniaxial plastic tension. Scattering of the measured magnetic parameters was substantial within the Luders band region with stabilization at higher strains. Compressive residual stresses in the deformation direction formed a hard magnetization axis with intriguing two-phase remagnetization. The magnetic parameters had the highest sensitivity to strain in this direction. They changed as cos2 with rotation to the perpendicular easy magnetization axis, where the magnetic sensitivity was the lowest. The relation between the deformed steel microstructure (dislocation and residual stress patterns) and the obtained magnetic behaviour is interpreted. The applicability of the examined techniques for the non-destructive characterization of steel degradation is discussed.

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Magnetic anisotropy of plastically deformed low-carbon steel

Local wall thinning defects are unavoidable defects in actual engineering structures and in some cases it occurs in a certain depth range of the object structures. In this study, a novel frequency-band-selecting pulsed eddy current testing (FSPECT) has been proposed for the detection of local wall thinning defects in a certain depth range. Feature of peak value has been extracted and analyzed. The results demonstrate that the FSPECT possess the comparable performances in terms of detection sensitivity over the traditional square wave pulsed eddy current testing (PECT). In addition, other fruitful detailed features extraction in the numerical calculation and experimental signals of FSPECT are deeply studied. The features obtained by simulation and experiment mainly include lift-off point of intersection (LOI) and zero-crossing time. Furthermore, the influences of the depth of local wall thinning defect on features of LOI and zero-crossing time have been explored, which enhance the accuracy and reliability of FSPECT method for the evaluation of local wall thinning defects.

Features extraction and discussion in a novel frequency-band-selecting pulsed eddy current testing method for the detection of a certain depth range of defects

Tetsuya Uchimoto

Papers

Development of a very fast simulator for pulsed eddy current testing signals of local wall thinning

Governing conditions of repeatable Barkhausen noise response

Magnetic anisotropy of plastically deformed low-carbon steel

Features extraction and discussion in a novel frequency-band-selecting pulsed eddy current testing method for the detection of a certain depth range of defects

Synthesis of Ti3SiC2/TiC composites from TiH2/SiC/TiC powders